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sm_statefuns.c

/* SCTP kernel reference Implementation
 * (C) Copyright IBM Corp. 2001, 2004
 * Copyright (c) 1999-2000 Cisco, Inc.
 * Copyright (c) 1999-2001 Motorola, Inc.
 * Copyright (c) 2001-2002 Intel Corp.
 * Copyright (c) 2002      Nokia Corp.
 *
 * This file is part of the SCTP kernel reference Implementation
 *
 * This is part of the SCTP Linux Kernel Reference Implementation.
 *
 * These are the state functions for the state machine.
 *
 * The SCTP reference implementation is free software;
 * you can redistribute it and/or modify it under the terms of
 * the GNU General Public License as published by
 * the Free Software Foundation; either version 2, or (at your option)
 * any later version.
 *
 * The SCTP reference implementation is distributed in the hope that it
 * will be useful, but WITHOUT ANY WARRANTY; without even the implied
 *                 ************************
 * warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
 * See the GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with GNU CC; see the file COPYING.  If not, write to
 * the Free Software Foundation, 59 Temple Place - Suite 330,
 * Boston, MA 02111-1307, USA.
 *
 * Please send any bug reports or fixes you make to the
 * email address(es):
 *    lksctp developers <lksctp-developers@lists.sourceforge.net>
 *
 * Or submit a bug report through the following website:
 *    http://www.sf.net/projects/lksctp
 *
 * Written or modified by:
 *    La Monte H.P. Yarroll <piggy@acm.org>
 *    Karl Knutson          <karl@athena.chicago.il.us>
 *    Mathew Kotowsky       <kotowsky@sctp.org>
 *    Sridhar Samudrala     <samudrala@us.ibm.com>
 *    Jon Grimm             <jgrimm@us.ibm.com>
 *    Hui Huang       <hui.huang@nokia.com>
 *    Dajiang Zhang         <dajiang.zhang@nokia.com>
 *    Daisy Chang     <daisyc@us.ibm.com>
 *    Ardelle Fan     <ardelle.fan@intel.com>
 *    Ryan Layer      <rmlayer@us.ibm.com>
 *    Kevin Gao             <kevin.gao@intel.com>
 *
 * Any bugs reported given to us we will try to fix... any fixes shared will
 * be incorporated into the next SCTP release.
 */

#include <linux/types.h>
#include <linux/kernel.h>
#include <linux/ip.h>
#include <linux/ipv6.h>
#include <linux/net.h>
#include <linux/inet.h>
#include <net/sock.h>
#include <net/inet_ecn.h>
#include <linux/skbuff.h>
#include <net/sctp/sctp.h>
#include <net/sctp/sm.h>
#include <net/sctp/structs.h>

static struct sctp_packet *sctp_abort_pkt_new(const struct sctp_endpoint *ep,
                          const struct sctp_association *asoc,
                          struct sctp_chunk *chunk,
                          const void *payload,
                          size_t paylen);
static int sctp_eat_data(const struct sctp_association *asoc,
                   struct sctp_chunk *chunk,
                   sctp_cmd_seq_t *commands);
static struct sctp_packet *sctp_ootb_pkt_new(const struct sctp_association *asoc,
                                   const struct sctp_chunk *chunk);
static void sctp_send_stale_cookie_err(const struct sctp_endpoint *ep,
                               const struct sctp_association *asoc,
                               const struct sctp_chunk *chunk,
                               sctp_cmd_seq_t *commands,
                               struct sctp_chunk *err_chunk);
static sctp_disposition_t sctp_sf_do_5_2_6_stale(const struct sctp_endpoint *ep,
                                     const struct sctp_association *asoc,
                                     const sctp_subtype_t type,
                                     void *arg,
                                     sctp_cmd_seq_t *commands);
static sctp_disposition_t sctp_sf_shut_8_4_5(const struct sctp_endpoint *ep,
                                   const struct sctp_association *asoc,
                                   const sctp_subtype_t type,
                                   void *arg,
                                   sctp_cmd_seq_t *commands);
static struct sctp_sackhdr *sctp_sm_pull_sack(struct sctp_chunk *chunk);

static sctp_disposition_t sctp_stop_t1_and_abort(sctp_cmd_seq_t *commands,
                                 __u16 error, int sk_err,
                                 const struct sctp_association *asoc,
                                 struct sctp_transport *transport);

static sctp_disposition_t sctp_sf_violation_chunklen(
                             const struct sctp_endpoint *ep,
                             const struct sctp_association *asoc,
                             const sctp_subtype_t type,
                             void *arg,
                             sctp_cmd_seq_t *commands);

/* Small helper function that checks if the chunk length
 * is of the appropriate length.  The 'required_length' argument
 * is set to be the size of a specific chunk we are testing.
 * Return Values:  1 = Valid length
 *             0 = Invalid length
 *
 */
static inline int
sctp_chunk_length_valid(struct sctp_chunk *chunk,
                     __u16 required_length)
{
      __u16 chunk_length = ntohs(chunk->chunk_hdr->length);

      if (unlikely(chunk_length < required_length))
            return 0;

      return 1;
}

/**********************************************************
 * These are the state functions for handling chunk events.
 **********************************************************/

/*
 * Process the final SHUTDOWN COMPLETE.
 *
 * Section: 4 (C) (diagram), 9.2
 * Upon reception of the SHUTDOWN COMPLETE chunk the endpoint will verify
 * that it is in SHUTDOWN-ACK-SENT state, if it is not the chunk should be
 * discarded. If the endpoint is in the SHUTDOWN-ACK-SENT state the endpoint
 * should stop the T2-shutdown timer and remove all knowledge of the
 * association (and thus the association enters the CLOSED state).
 *
 * Verification Tag: 8.5.1(C), sctpimpguide 2.41.
 * C) Rules for packet carrying SHUTDOWN COMPLETE:
 * ...
 * - The receiver of a SHUTDOWN COMPLETE shall accept the packet
 *   if the Verification Tag field of the packet matches its own tag and
 *   the T bit is not set
 *   OR
 *   it is set to its peer's tag and the T bit is set in the Chunk
 *   Flags.
 *   Otherwise, the receiver MUST silently discard the packet
 *   and take no further action.  An endpoint MUST ignore the
 *   SHUTDOWN COMPLETE if it is not in the SHUTDOWN-ACK-SENT state.
 *
 * Inputs
 * (endpoint, asoc, chunk)
 *
 * Outputs
 * (asoc, reply_msg, msg_up, timers, counters)
 *
 * The return value is the disposition of the chunk.
 */
sctp_disposition_t sctp_sf_do_4_C(const struct sctp_endpoint *ep,
                          const struct sctp_association *asoc,
                          const sctp_subtype_t type,
                          void *arg,
                          sctp_cmd_seq_t *commands)
{
      struct sctp_chunk *chunk = arg;
      struct sctp_ulpevent *ev;

      /* RFC 2960 6.10 Bundling
       *
       * An endpoint MUST NOT bundle INIT, INIT ACK or
       * SHUTDOWN COMPLETE with any other chunks.
       */
      if (!chunk->singleton)
            return SCTP_DISPOSITION_VIOLATION;

      if (!sctp_vtag_verify_either(chunk, asoc))
            return sctp_sf_pdiscard(ep, asoc, type, arg, commands);

      /* RFC 2960 10.2 SCTP-to-ULP
       *
       * H) SHUTDOWN COMPLETE notification
       *
       * When SCTP completes the shutdown procedures (section 9.2) this
       * notification is passed to the upper layer.
       */
      ev = sctp_ulpevent_make_assoc_change(asoc, 0, SCTP_SHUTDOWN_COMP,
                                   0, 0, 0, GFP_ATOMIC);
      if (!ev)
            goto nomem;

      sctp_add_cmd_sf(commands, SCTP_CMD_EVENT_ULP, SCTP_ULPEVENT(ev));

      /* Upon reception of the SHUTDOWN COMPLETE chunk the endpoint
       * will verify that it is in SHUTDOWN-ACK-SENT state, if it is
       * not the chunk should be discarded. If the endpoint is in
       * the SHUTDOWN-ACK-SENT state the endpoint should stop the
       * T2-shutdown timer and remove all knowledge of the
       * association (and thus the association enters the CLOSED
       * state).
       */
      sctp_add_cmd_sf(commands, SCTP_CMD_TIMER_STOP,
                  SCTP_TO(SCTP_EVENT_TIMEOUT_T2_SHUTDOWN));

      sctp_add_cmd_sf(commands, SCTP_CMD_TIMER_STOP,
                  SCTP_TO(SCTP_EVENT_TIMEOUT_T5_SHUTDOWN_GUARD));

      sctp_add_cmd_sf(commands, SCTP_CMD_NEW_STATE,
                  SCTP_STATE(SCTP_STATE_CLOSED));

      SCTP_INC_STATS(SCTP_MIB_SHUTDOWNS);
      SCTP_DEC_STATS(SCTP_MIB_CURRESTAB);

      sctp_add_cmd_sf(commands, SCTP_CMD_DELETE_TCB, SCTP_NULL());

      return SCTP_DISPOSITION_DELETE_TCB;

nomem:
      return SCTP_DISPOSITION_NOMEM;
}

/*
 * Respond to a normal INIT chunk.
 * We are the side that is being asked for an association.
 *
 * Section: 5.1 Normal Establishment of an Association, B
 * B) "Z" shall respond immediately with an INIT ACK chunk.  The
 *    destination IP address of the INIT ACK MUST be set to the source
 *    IP address of the INIT to which this INIT ACK is responding.  In
 *    the response, besides filling in other parameters, "Z" must set the
 *    Verification Tag field to Tag_A, and also provide its own
 *    Verification Tag (Tag_Z) in the Initiate Tag field.
 *
 * Verification Tag: Must be 0. 
 *
 * Inputs
 * (endpoint, asoc, chunk)
 *
 * Outputs
 * (asoc, reply_msg, msg_up, timers, counters)
 *
 * The return value is the disposition of the chunk.
 */
sctp_disposition_t sctp_sf_do_5_1B_init(const struct sctp_endpoint *ep,
                              const struct sctp_association *asoc,
                              const sctp_subtype_t type,
                              void *arg,
                              sctp_cmd_seq_t *commands)
{
      struct sctp_chunk *chunk = arg;
      struct sctp_chunk *repl;
      struct sctp_association *new_asoc;
      struct sctp_chunk *err_chunk;
      struct sctp_packet *packet;
      sctp_unrecognized_param_t *unk_param;
      struct sock *sk;
      int len;

      /* 6.10 Bundling
       * An endpoint MUST NOT bundle INIT, INIT ACK or
       * SHUTDOWN COMPLETE with any other chunks.
       * 
       * IG Section 2.11.2
       * Furthermore, we require that the receiver of an INIT chunk MUST
       * enforce these rules by silently discarding an arriving packet
       * with an INIT chunk that is bundled with other chunks.
       */
      if (!chunk->singleton)
            return sctp_sf_pdiscard(ep, asoc, type, arg, commands);

      /* If the packet is an OOTB packet which is temporarily on the
       * control endpoint, respond with an ABORT.
       */
      if (ep == sctp_sk((sctp_get_ctl_sock()))->ep)
            return sctp_sf_tabort_8_4_8(ep, asoc, type, arg, commands);

      sk = ep->base.sk;
      /* If the endpoint is not listening or if the number of associations
       * on the TCP-style socket exceed the max backlog, respond with an
       * ABORT.
       */
      if (!sctp_sstate(sk, LISTENING) ||
          (sctp_style(sk, TCP) &&
           sk_acceptq_is_full(sk)))
            return sctp_sf_tabort_8_4_8(ep, asoc, type, arg, commands);

      /* 3.1 A packet containing an INIT chunk MUST have a zero Verification
       * Tag. 
       */
      if (chunk->sctp_hdr->vtag != 0)
            return sctp_sf_tabort_8_4_8(ep, asoc, type, arg, commands);

      /* Make sure that the INIT chunk has a valid length.
       * Normally, this would cause an ABORT with a Protocol Violation
       * error, but since we don't have an association, we'll
       * just discard the packet.
       */
      if (!sctp_chunk_length_valid(chunk, sizeof(sctp_init_chunk_t)))
            return sctp_sf_pdiscard(ep, asoc, type, arg, commands);

      /* Verify the INIT chunk before processing it. */
      err_chunk = NULL;
      if (!sctp_verify_init(asoc, chunk->chunk_hdr->type,
                        (sctp_init_chunk_t *)chunk->chunk_hdr, chunk,
                        &err_chunk)) {
            /* This chunk contains fatal error. It is to be discarded.
             * Send an ABORT, with causes if there is any.
             */
            if (err_chunk) {
                  packet = sctp_abort_pkt_new(ep, asoc, arg,
                              (__u8 *)(err_chunk->chunk_hdr) +
                              sizeof(sctp_chunkhdr_t),
                              ntohs(err_chunk->chunk_hdr->length) -
                              sizeof(sctp_chunkhdr_t));

                  sctp_chunk_free(err_chunk);

                  if (packet) {
                        sctp_add_cmd_sf(commands, SCTP_CMD_SEND_PKT,
                                    SCTP_PACKET(packet));
                        SCTP_INC_STATS(SCTP_MIB_OUTCTRLCHUNKS);
                        return SCTP_DISPOSITION_CONSUME;
                  } else {
                        return SCTP_DISPOSITION_NOMEM;
                  }
            } else {
                  return sctp_sf_tabort_8_4_8(ep, asoc, type, arg,
                                        commands);
            }
      }

        /* Grab the INIT header.  */
      chunk->subh.init_hdr = (sctp_inithdr_t *)chunk->skb->data;

      /* Tag the variable length parameters.  */
      chunk->param_hdr.v = skb_pull(chunk->skb, sizeof(sctp_inithdr_t));

      new_asoc = sctp_make_temp_asoc(ep, chunk, GFP_ATOMIC);
      if (!new_asoc)
            goto nomem;

      /* The call, sctp_process_init(), can fail on memory allocation.  */
      if (!sctp_process_init(new_asoc, chunk->chunk_hdr->type,
                         sctp_source(chunk),
                         (sctp_init_chunk_t *)chunk->chunk_hdr,
                         GFP_ATOMIC))
            goto nomem_init;

      sctp_add_cmd_sf(commands, SCTP_CMD_NEW_ASOC, SCTP_ASOC(new_asoc));

      /* B) "Z" shall respond immediately with an INIT ACK chunk.  */

      /* If there are errors need to be reported for unknown parameters,
       * make sure to reserve enough room in the INIT ACK for them.
       */
      len = 0;
      if (err_chunk)
            len = ntohs(err_chunk->chunk_hdr->length) -
                  sizeof(sctp_chunkhdr_t);

      if (sctp_assoc_set_bind_addr_from_ep(new_asoc, GFP_ATOMIC) < 0)
            goto nomem_ack;

      repl = sctp_make_init_ack(new_asoc, chunk, GFP_ATOMIC, len);
      if (!repl)
            goto nomem_ack;

      /* If there are errors need to be reported for unknown parameters,
       * include them in the outgoing INIT ACK as "Unrecognized parameter"
       * parameter.
       */
      if (err_chunk) {
            /* Get the "Unrecognized parameter" parameter(s) out of the
             * ERROR chunk generated by sctp_verify_init(). Since the
             * error cause code for "unknown parameter" and the
             * "Unrecognized parameter" type is the same, we can
             * construct the parameters in INIT ACK by copying the
             * ERROR causes over.
             */
            unk_param = (sctp_unrecognized_param_t *)
                      ((__u8 *)(err_chunk->chunk_hdr) +
                      sizeof(sctp_chunkhdr_t));
            /* Replace the cause code with the "Unrecognized parameter"
             * parameter type.
             */
            sctp_addto_chunk(repl, len, unk_param);
            sctp_chunk_free(err_chunk);
      }

      sctp_add_cmd_sf(commands, SCTP_CMD_REPLY, SCTP_CHUNK(repl));

      /*
       * Note:  After sending out INIT ACK with the State Cookie parameter,
       * "Z" MUST NOT allocate any resources, nor keep any states for the
       * new association.  Otherwise, "Z" will be vulnerable to resource
       * attacks.
       */
      sctp_add_cmd_sf(commands, SCTP_CMD_DELETE_TCB, SCTP_NULL());

      return SCTP_DISPOSITION_DELETE_TCB;

nomem_ack:
      if (err_chunk)
            sctp_chunk_free(err_chunk);
nomem_init:
      sctp_association_free(new_asoc);
nomem:
      return SCTP_DISPOSITION_NOMEM;
}

/*
 * Respond to a normal INIT ACK chunk.
 * We are the side that is initiating the association.
 *
 * Section: 5.1 Normal Establishment of an Association, C
 * C) Upon reception of the INIT ACK from "Z", "A" shall stop the T1-init
 *    timer and leave COOKIE-WAIT state. "A" shall then send the State
 *    Cookie received in the INIT ACK chunk in a COOKIE ECHO chunk, start
 *    the T1-cookie timer, and enter the COOKIE-ECHOED state.
 *
 *    Note: The COOKIE ECHO chunk can be bundled with any pending outbound
 *    DATA chunks, but it MUST be the first chunk in the packet and
 *    until the COOKIE ACK is returned the sender MUST NOT send any
 *    other packets to the peer.
 *
 * Verification Tag: 3.3.3
 *   If the value of the Initiate Tag in a received INIT ACK chunk is
 *   found to be 0, the receiver MUST treat it as an error and close the
 *   association by transmitting an ABORT.
 *
 * Inputs
 * (endpoint, asoc, chunk)
 *
 * Outputs
 * (asoc, reply_msg, msg_up, timers, counters)
 *
 * The return value is the disposition of the chunk.
 */
sctp_disposition_t sctp_sf_do_5_1C_ack(const struct sctp_endpoint *ep,
                               const struct sctp_association *asoc,
                               const sctp_subtype_t type,
                               void *arg,
                               sctp_cmd_seq_t *commands)
{
      struct sctp_chunk *chunk = arg;
      sctp_init_chunk_t *initchunk;
      __u32 init_tag;
      struct sctp_chunk *err_chunk;
      struct sctp_packet *packet;
      __u16 error;

      if (!sctp_vtag_verify(chunk, asoc))
            return sctp_sf_pdiscard(ep, asoc, type, arg, commands);

      /* Make sure that the INIT-ACK chunk has a valid length */
      if (!sctp_chunk_length_valid(chunk, sizeof(sctp_initack_chunk_t)))
            return sctp_sf_violation_chunklen(ep, asoc, type, arg,
                                      commands);
      /* 6.10 Bundling
       * An endpoint MUST NOT bundle INIT, INIT ACK or
       * SHUTDOWN COMPLETE with any other chunks.
       */
      if (!chunk->singleton)
            return SCTP_DISPOSITION_VIOLATION;

      /* Grab the INIT header.  */
      chunk->subh.init_hdr = (sctp_inithdr_t *) chunk->skb->data;

      init_tag = ntohl(chunk->subh.init_hdr->init_tag);

      /* Verification Tag: 3.3.3
       *   If the value of the Initiate Tag in a received INIT ACK
       *   chunk is found to be 0, the receiver MUST treat it as an
       *   error and close the association by transmitting an ABORT.
       */
      if (!init_tag) {
            struct sctp_chunk *reply = sctp_make_abort(asoc, chunk, 0);
            if (!reply)
                  goto nomem;

            sctp_add_cmd_sf(commands, SCTP_CMD_REPLY, SCTP_CHUNK(reply));
            return sctp_stop_t1_and_abort(commands, SCTP_ERROR_INV_PARAM,
                                    ECONNREFUSED, asoc,
                                    chunk->transport);
      }

      /* Verify the INIT chunk before processing it. */
      err_chunk = NULL;
      if (!sctp_verify_init(asoc, chunk->chunk_hdr->type,
                        (sctp_init_chunk_t *)chunk->chunk_hdr, chunk,
                        &err_chunk)) {

            SCTP_INC_STATS(SCTP_MIB_ABORTEDS);

            /* This chunk contains fatal error. It is to be discarded.
             * Send an ABORT, with causes if there is any.
             */
            if (err_chunk) {
                  packet = sctp_abort_pkt_new(ep, asoc, arg,
                              (__u8 *)(err_chunk->chunk_hdr) +
                              sizeof(sctp_chunkhdr_t),
                              ntohs(err_chunk->chunk_hdr->length) -
                              sizeof(sctp_chunkhdr_t));

                  sctp_chunk_free(err_chunk);

                  if (packet) {
                        sctp_add_cmd_sf(commands, SCTP_CMD_SEND_PKT,
                                    SCTP_PACKET(packet));
                        SCTP_INC_STATS(SCTP_MIB_OUTCTRLCHUNKS);
                        error = SCTP_ERROR_INV_PARAM;
                  } else {
                        error = SCTP_ERROR_NO_RESOURCE;
                  }
            } else {
                  sctp_sf_tabort_8_4_8(ep, asoc, type, arg, commands);
                  error = SCTP_ERROR_INV_PARAM;
            }
            return sctp_stop_t1_and_abort(commands, error, ECONNREFUSED,
                                    asoc, chunk->transport);
      }

      /* Tag the variable length parameters.  Note that we never
       * convert the parameters in an INIT chunk.
       */
      chunk->param_hdr.v = skb_pull(chunk->skb, sizeof(sctp_inithdr_t));

      initchunk = (sctp_init_chunk_t *) chunk->chunk_hdr;

      sctp_add_cmd_sf(commands, SCTP_CMD_PEER_INIT,
                  SCTP_PEER_INIT(initchunk));

      /* Reset init error count upon receipt of INIT-ACK.  */
      sctp_add_cmd_sf(commands, SCTP_CMD_INIT_COUNTER_RESET, SCTP_NULL());

      /* 5.1 C) "A" shall stop the T1-init timer and leave
       * COOKIE-WAIT state.  "A" shall then ... start the T1-cookie
       * timer, and enter the COOKIE-ECHOED state.
       */
      sctp_add_cmd_sf(commands, SCTP_CMD_TIMER_STOP,
                  SCTP_TO(SCTP_EVENT_TIMEOUT_T1_INIT));
      sctp_add_cmd_sf(commands, SCTP_CMD_TIMER_START,
                  SCTP_TO(SCTP_EVENT_TIMEOUT_T1_COOKIE));
      sctp_add_cmd_sf(commands, SCTP_CMD_NEW_STATE,
                  SCTP_STATE(SCTP_STATE_COOKIE_ECHOED));

      /* 5.1 C) "A" shall then send the State Cookie received in the
       * INIT ACK chunk in a COOKIE ECHO chunk, ...
       */
      /* If there is any errors to report, send the ERROR chunk generated
       * for unknown parameters as well.
       */
      sctp_add_cmd_sf(commands, SCTP_CMD_GEN_COOKIE_ECHO,
                  SCTP_CHUNK(err_chunk));

      return SCTP_DISPOSITION_CONSUME;

nomem:
      return SCTP_DISPOSITION_NOMEM;
}

/*
 * Respond to a normal COOKIE ECHO chunk.
 * We are the side that is being asked for an association.
 *
 * Section: 5.1 Normal Establishment of an Association, D
 * D) Upon reception of the COOKIE ECHO chunk, Endpoint "Z" will reply
 *    with a COOKIE ACK chunk after building a TCB and moving to
 *    the ESTABLISHED state. A COOKIE ACK chunk may be bundled with
 *    any pending DATA chunks (and/or SACK chunks), but the COOKIE ACK
 *    chunk MUST be the first chunk in the packet.
 *
 *   IMPLEMENTATION NOTE: An implementation may choose to send the
 *   Communication Up notification to the SCTP user upon reception
 *   of a valid COOKIE ECHO chunk.
 *
 * Verification Tag: 8.5.1 Exceptions in Verification Tag Rules
 * D) Rules for packet carrying a COOKIE ECHO
 *
 * - When sending a COOKIE ECHO, the endpoint MUST use the value of the
 *   Initial Tag received in the INIT ACK.
 *
 * - The receiver of a COOKIE ECHO follows the procedures in Section 5.
 *
 * Inputs
 * (endpoint, asoc, chunk)
 *
 * Outputs
 * (asoc, reply_msg, msg_up, timers, counters)
 *
 * The return value is the disposition of the chunk.
 */
sctp_disposition_t sctp_sf_do_5_1D_ce(const struct sctp_endpoint *ep,
                              const struct sctp_association *asoc,
                              const sctp_subtype_t type, void *arg,
                              sctp_cmd_seq_t *commands)
{
      struct sctp_chunk *chunk = arg;
      struct sctp_association *new_asoc;
      sctp_init_chunk_t *peer_init;
      struct sctp_chunk *repl;
      struct sctp_ulpevent *ev;
      int error = 0;
      struct sctp_chunk *err_chk_p;

      /* If the packet is an OOTB packet which is temporarily on the
       * control endpoint, respond with an ABORT.
       */
      if (ep == sctp_sk((sctp_get_ctl_sock()))->ep)
            return sctp_sf_ootb(ep, asoc, type, arg, commands);

      /* Make sure that the COOKIE_ECHO chunk has a valid length.
       * In this case, we check that we have enough for at least a
       * chunk header.  More detailed verification is done
       * in sctp_unpack_cookie().
       */
      if (!sctp_chunk_length_valid(chunk, sizeof(sctp_chunkhdr_t)))
            return sctp_sf_pdiscard(ep, asoc, type, arg, commands);

      /* "Decode" the chunk.  We have no optional parameters so we
       * are in good shape.
       */
        chunk->subh.cookie_hdr =
            (struct sctp_signed_cookie *)chunk->skb->data;
      if (!pskb_pull(chunk->skb, ntohs(chunk->chunk_hdr->length) -
                               sizeof(sctp_chunkhdr_t)))
            goto nomem;

      /* 5.1 D) Upon reception of the COOKIE ECHO chunk, Endpoint
       * "Z" will reply with a COOKIE ACK chunk after building a TCB
       * and moving to the ESTABLISHED state.
       */
      new_asoc = sctp_unpack_cookie(ep, asoc, chunk, GFP_ATOMIC, &error,
                              &err_chk_p);

      /* FIXME:
       * If the re-build failed, what is the proper error path
       * from here?
       *
       * [We should abort the association. --piggy]
       */
      if (!new_asoc) {
            /* FIXME: Several errors are possible.  A bad cookie should
             * be silently discarded, but think about logging it too.
             */
            switch (error) {
            case -SCTP_IERROR_NOMEM:
                  goto nomem;

            case -SCTP_IERROR_STALE_COOKIE:
                  sctp_send_stale_cookie_err(ep, asoc, chunk, commands,
                                       err_chk_p);
                  return sctp_sf_pdiscard(ep, asoc, type, arg, commands);

            case -SCTP_IERROR_BAD_SIG:
            default:
                  return sctp_sf_pdiscard(ep, asoc, type, arg, commands);
            };
      }

      sctp_add_cmd_sf(commands, SCTP_CMD_NEW_ASOC, SCTP_ASOC(new_asoc));
      sctp_add_cmd_sf(commands, SCTP_CMD_NEW_STATE,
                  SCTP_STATE(SCTP_STATE_ESTABLISHED));
      SCTP_INC_STATS(SCTP_MIB_CURRESTAB);
      SCTP_INC_STATS(SCTP_MIB_PASSIVEESTABS);
      sctp_add_cmd_sf(commands, SCTP_CMD_HB_TIMERS_START, SCTP_NULL());

      if (new_asoc->autoclose)
            sctp_add_cmd_sf(commands, SCTP_CMD_TIMER_START,
                        SCTP_TO(SCTP_EVENT_TIMEOUT_AUTOCLOSE));

      sctp_add_cmd_sf(commands, SCTP_CMD_TRANSMIT, SCTP_NULL());

      /* Re-build the bind address for the association is done in
       * the sctp_unpack_cookie() already.
       */
      /* This is a brand-new association, so these are not yet side
       * effects--it is safe to run them here.
       */
      peer_init = &chunk->subh.cookie_hdr->c.peer_init[0];

      if (!sctp_process_init(new_asoc, chunk->chunk_hdr->type,
                         &chunk->subh.cookie_hdr->c.peer_addr,
                         peer_init, GFP_ATOMIC))
            goto nomem_init;

      repl = sctp_make_cookie_ack(new_asoc, chunk);
      if (!repl)
            goto nomem_repl;

      sctp_add_cmd_sf(commands, SCTP_CMD_REPLY, SCTP_CHUNK(repl));

      /* RFC 2960 5.1 Normal Establishment of an Association
       *
       * D) IMPLEMENTATION NOTE: An implementation may choose to
       * send the Communication Up notification to the SCTP user
       * upon reception of a valid COOKIE ECHO chunk.
       */
      ev = sctp_ulpevent_make_assoc_change(new_asoc, 0, SCTP_COMM_UP, 0,
                                   new_asoc->c.sinit_num_ostreams,
                                   new_asoc->c.sinit_max_instreams,
                                   GFP_ATOMIC);
      if (!ev)
            goto nomem_ev;

      sctp_add_cmd_sf(commands, SCTP_CMD_EVENT_ULP, SCTP_ULPEVENT(ev));

      /* Sockets API Draft Section 5.3.1.6      
       * When a peer sends a Adaption Layer Indication parameter , SCTP
       * delivers this notification to inform the application that of the
       * peers requested adaption layer.
       */
      if (new_asoc->peer.adaption_ind) {
            ev = sctp_ulpevent_make_adaption_indication(new_asoc,
                                              GFP_ATOMIC);
            if (!ev)
                  goto nomem_ev;

            sctp_add_cmd_sf(commands, SCTP_CMD_EVENT_ULP,
                        SCTP_ULPEVENT(ev));
      }

      return SCTP_DISPOSITION_CONSUME;

nomem_ev:
      sctp_chunk_free(repl);
nomem_repl:
nomem_init:
      sctp_association_free(new_asoc);
nomem:
      return SCTP_DISPOSITION_NOMEM;
}

/*
 * Respond to a normal COOKIE ACK chunk.
 * We are the side that is being asked for an association.
 *
 * RFC 2960 5.1 Normal Establishment of an Association
 *
 * E) Upon reception of the COOKIE ACK, endpoint "A" will move from the
 *    COOKIE-ECHOED state to the ESTABLISHED state, stopping the T1-cookie
 *    timer. It may also notify its ULP about the successful
 *    establishment of the association with a Communication Up
 *    notification (see Section 10).
 *
 * Verification Tag:
 * Inputs
 * (endpoint, asoc, chunk)
 *
 * Outputs
 * (asoc, reply_msg, msg_up, timers, counters)
 *
 * The return value is the disposition of the chunk.
 */
sctp_disposition_t sctp_sf_do_5_1E_ca(const struct sctp_endpoint *ep,
                              const struct sctp_association *asoc,
                              const sctp_subtype_t type, void *arg,
                              sctp_cmd_seq_t *commands)
{
      struct sctp_chunk *chunk = arg;
      struct sctp_ulpevent *ev;

      if (!sctp_vtag_verify(chunk, asoc))
            return sctp_sf_pdiscard(ep, asoc, type, arg, commands);

      /* Verify that the chunk length for the COOKIE-ACK is OK.
       * If we don't do this, any bundled chunks may be junked.
       */
      if (!sctp_chunk_length_valid(chunk, sizeof(sctp_chunkhdr_t)))
            return sctp_sf_violation_chunklen(ep, asoc, type, arg,
                                      commands);

      /* Reset init error count upon receipt of COOKIE-ACK,
       * to avoid problems with the managemement of this
       * counter in stale cookie situations when a transition back
       * from the COOKIE-ECHOED state to the COOKIE-WAIT
       * state is performed.
       */
      sctp_add_cmd_sf(commands, SCTP_CMD_INIT_COUNTER_RESET, SCTP_NULL());

      /* RFC 2960 5.1 Normal Establishment of an Association
       *
       * E) Upon reception of the COOKIE ACK, endpoint "A" will move
       * from the COOKIE-ECHOED state to the ESTABLISHED state,
       * stopping the T1-cookie timer.
       */
      sctp_add_cmd_sf(commands, SCTP_CMD_TIMER_STOP,
                  SCTP_TO(SCTP_EVENT_TIMEOUT_T1_COOKIE));
      sctp_add_cmd_sf(commands, SCTP_CMD_NEW_STATE,
                  SCTP_STATE(SCTP_STATE_ESTABLISHED));
      SCTP_INC_STATS(SCTP_MIB_CURRESTAB);
      SCTP_INC_STATS(SCTP_MIB_ACTIVEESTABS);
      sctp_add_cmd_sf(commands, SCTP_CMD_HB_TIMERS_START, SCTP_NULL());
      if (asoc->autoclose)
            sctp_add_cmd_sf(commands, SCTP_CMD_TIMER_START,
                        SCTP_TO(SCTP_EVENT_TIMEOUT_AUTOCLOSE));
      sctp_add_cmd_sf(commands, SCTP_CMD_TRANSMIT, SCTP_NULL());

      /* It may also notify its ULP about the successful
       * establishment of the association with a Communication Up
       * notification (see Section 10).
       */
      ev = sctp_ulpevent_make_assoc_change(asoc, 0, SCTP_COMM_UP,
                                   0, asoc->c.sinit_num_ostreams,
                                   asoc->c.sinit_max_instreams,
                                   GFP_ATOMIC);

      if (!ev)
            goto nomem;

      sctp_add_cmd_sf(commands, SCTP_CMD_EVENT_ULP, SCTP_ULPEVENT(ev));

      /* Sockets API Draft Section 5.3.1.6
       * When a peer sends a Adaption Layer Indication parameter , SCTP
       * delivers this notification to inform the application that of the
       * peers requested adaption layer.
       */
      if (asoc->peer.adaption_ind) {
            ev = sctp_ulpevent_make_adaption_indication(asoc, GFP_ATOMIC);
            if (!ev)
                  goto nomem;

            sctp_add_cmd_sf(commands, SCTP_CMD_EVENT_ULP,
                        SCTP_ULPEVENT(ev));
      }

      return SCTP_DISPOSITION_CONSUME;
nomem:
      return SCTP_DISPOSITION_NOMEM;
}

/* Generate and sendout a heartbeat packet.  */
static sctp_disposition_t sctp_sf_heartbeat(const struct sctp_endpoint *ep,
                                  const struct sctp_association *asoc,
                                  const sctp_subtype_t type,
                                  void *arg,
                                  sctp_cmd_seq_t *commands)
{
      struct sctp_transport *transport = (struct sctp_transport *) arg;
      struct sctp_chunk *reply;
      sctp_sender_hb_info_t hbinfo;
      size_t paylen = 0;

      hbinfo.param_hdr.type = SCTP_PARAM_HEARTBEAT_INFO;
      hbinfo.param_hdr.length = htons(sizeof(sctp_sender_hb_info_t));
      hbinfo.daddr = transport->ipaddr;
      hbinfo.sent_at = jiffies;
      hbinfo.hb_nonce = transport->hb_nonce;

      /* Send a heartbeat to our peer.  */
      paylen = sizeof(sctp_sender_hb_info_t);
      reply = sctp_make_heartbeat(asoc, transport, &hbinfo, paylen);
      if (!reply)
            return SCTP_DISPOSITION_NOMEM;

      /* Set rto_pending indicating that an RTT measurement
       * is started with this heartbeat chunk.
       */
      sctp_add_cmd_sf(commands, SCTP_CMD_RTO_PENDING,
                  SCTP_TRANSPORT(transport));

      sctp_add_cmd_sf(commands, SCTP_CMD_REPLY, SCTP_CHUNK(reply));
      return SCTP_DISPOSITION_CONSUME;
}

/* Generate a HEARTBEAT packet on the given transport.  */
sctp_disposition_t sctp_sf_sendbeat_8_3(const struct sctp_endpoint *ep,
                              const struct sctp_association *asoc,
                              const sctp_subtype_t type,
                              void *arg,
                              sctp_cmd_seq_t *commands)
{
      struct sctp_transport *transport = (struct sctp_transport *) arg;

      if (asoc->overall_error_count >= asoc->max_retrans) {
            sctp_add_cmd_sf(commands, SCTP_CMD_SET_SK_ERR,
                        SCTP_ERROR(ETIMEDOUT));
            /* CMD_ASSOC_FAILED calls CMD_DELETE_TCB. */
            sctp_add_cmd_sf(commands, SCTP_CMD_ASSOC_FAILED,
                        SCTP_U32(SCTP_ERROR_NO_ERROR));
            SCTP_INC_STATS(SCTP_MIB_ABORTEDS);
            SCTP_DEC_STATS(SCTP_MIB_CURRESTAB);
            return SCTP_DISPOSITION_DELETE_TCB;
      }

      /* Section 3.3.5.
       * The Sender-specific Heartbeat Info field should normally include
       * information about the sender's current time when this HEARTBEAT
       * chunk is sent and the destination transport address to which this
       * HEARTBEAT is sent (see Section 8.3).
       */

      if (transport->param_flags & SPP_HB_ENABLE) {
            if (SCTP_DISPOSITION_NOMEM ==
                        sctp_sf_heartbeat(ep, asoc, type, arg,
                                      commands))
                  return SCTP_DISPOSITION_NOMEM;
            /* Set transport error counter and association error counter
             * when sending heartbeat.
             */
            sctp_add_cmd_sf(commands, SCTP_CMD_TRANSPORT_RESET,
                        SCTP_TRANSPORT(transport));
      }
      sctp_add_cmd_sf(commands, SCTP_CMD_HB_TIMER_UPDATE,
                  SCTP_TRANSPORT(transport));

        return SCTP_DISPOSITION_CONSUME;
}

/*
 * Process an heartbeat request.
 *
 * Section: 8.3 Path Heartbeat
 * The receiver of the HEARTBEAT should immediately respond with a
 * HEARTBEAT ACK that contains the Heartbeat Information field copied
 * from the received HEARTBEAT chunk.
 *
 * Verification Tag:  8.5 Verification Tag [Normal verification]
 * When receiving an SCTP packet, the endpoint MUST ensure that the
 * value in the Verification Tag field of the received SCTP packet
 * matches its own Tag. If the received Verification Tag value does not
 * match the receiver's own tag value, the receiver shall silently
 * discard the packet and shall not process it any further except for
 * those cases listed in Section 8.5.1 below.
 *
 * Inputs
 * (endpoint, asoc, chunk)
 *
 * Outputs
 * (asoc, reply_msg, msg_up, timers, counters)
 *
 * The return value is the disposition of the chunk.
 */
sctp_disposition_t sctp_sf_beat_8_3(const struct sctp_endpoint *ep,
                            const struct sctp_association *asoc,
                            const sctp_subtype_t type,
                            void *arg,
                            sctp_cmd_seq_t *commands)
{
      struct sctp_chunk *chunk = arg;
      struct sctp_chunk *reply;
      size_t paylen = 0;

      if (!sctp_vtag_verify(chunk, asoc))
            return sctp_sf_pdiscard(ep, asoc, type, arg, commands);

      /* Make sure that the HEARTBEAT chunk has a valid length. */
      if (!sctp_chunk_length_valid(chunk, sizeof(sctp_heartbeat_chunk_t)))
            return sctp_sf_violation_chunklen(ep, asoc, type, arg,
                                      commands);

      /* 8.3 The receiver of the HEARTBEAT should immediately
       * respond with a HEARTBEAT ACK that contains the Heartbeat
       * Information field copied from the received HEARTBEAT chunk.
       */
      chunk->subh.hb_hdr = (sctp_heartbeathdr_t *) chunk->skb->data;
      paylen = ntohs(chunk->chunk_hdr->length) - sizeof(sctp_chunkhdr_t);
      if (!pskb_pull(chunk->skb, paylen))
            goto nomem;

      reply = sctp_make_heartbeat_ack(asoc, chunk,
                              chunk->subh.hb_hdr, paylen);
      if (!reply)
            goto nomem;

      sctp_add_cmd_sf(commands, SCTP_CMD_REPLY, SCTP_CHUNK(reply));
      return SCTP_DISPOSITION_CONSUME;

nomem:
      return SCTP_DISPOSITION_NOMEM;
}

/*
 * Process the returning HEARTBEAT ACK.
 *
 * Section: 8.3 Path Heartbeat
 * Upon the receipt of the HEARTBEAT ACK, the sender of the HEARTBEAT
 * should clear the error counter of the destination transport
 * address to which the HEARTBEAT was sent, and mark the destination
 * transport address as active if it is not so marked. The endpoint may
 * optionally report to the upper layer when an inactive destination
 * address is marked as active due to the reception of the latest
 * HEARTBEAT ACK. The receiver of the HEARTBEAT ACK must also
 * clear the association overall error count as well (as defined
 * in section 8.1).
 *
 * The receiver of the HEARTBEAT ACK should also perform an RTT
 * measurement for that destination transport address using the time
 * value carried in the HEARTBEAT ACK chunk.
 *
 * Verification Tag:  8.5 Verification Tag [Normal verification]
 *
 * Inputs
 * (endpoint, asoc, chunk)
 *
 * Outputs
 * (asoc, reply_msg, msg_up, timers, counters)
 *
 * The return value is the disposition of the chunk.
 */
sctp_disposition_t sctp_sf_backbeat_8_3(const struct sctp_endpoint *ep,
                              const struct sctp_association *asoc,
                              const sctp_subtype_t type,
                              void *arg,
                              sctp_cmd_seq_t *commands)
{
      struct sctp_chunk *chunk = arg;
      union sctp_addr from_addr;
      struct sctp_transport *link;
      sctp_sender_hb_info_t *hbinfo;
      unsigned long max_interval;

      if (!sctp_vtag_verify(chunk, asoc))
            return sctp_sf_pdiscard(ep, asoc, type, arg, commands);

      /* Make sure that the HEARTBEAT-ACK chunk has a valid length.  */
      if (!sctp_chunk_length_valid(chunk, sizeof(sctp_heartbeat_chunk_t)))
            return sctp_sf_violation_chunklen(ep, asoc, type, arg,
                                      commands);

      hbinfo = (sctp_sender_hb_info_t *) chunk->skb->data;
      /* Make sure that the length of the parameter is what we expect */
      if (ntohs(hbinfo->param_hdr.length) !=
                            sizeof(sctp_sender_hb_info_t)) {
            return SCTP_DISPOSITION_DISCARD;
      }

      from_addr = hbinfo->daddr;
      link = sctp_assoc_lookup_paddr(asoc, &from_addr);

      /* This should never happen, but lets log it if so.  */
      if (unlikely(!link)) {
            if (from_addr.sa.sa_family == AF_INET6) {
                  printk(KERN_WARNING
                         "%s association %p could not find address "
                         NIP6_FMT "\n",
                         __FUNCTION__,
                         asoc,
                         NIP6(from_addr.v6.sin6_addr));
            } else {
                  printk(KERN_WARNING
                         "%s association %p could not find address "
                         NIPQUAD_FMT "\n",
                         __FUNCTION__,
                         asoc,
                         NIPQUAD(from_addr.v4.sin_addr.s_addr));
            }
            return SCTP_DISPOSITION_DISCARD;
      }

      /* Validate the 64-bit random nonce. */
      if (hbinfo->hb_nonce != link->hb_nonce)
            return SCTP_DISPOSITION_DISCARD;

      max_interval = link->hbinterval + link->rto;

      /* Check if the timestamp looks valid.  */
      if (time_after(hbinfo->sent_at, jiffies) ||
          time_after(jiffies, hbinfo->sent_at + max_interval)) {
            SCTP_DEBUG_PRINTK("%s: HEARTBEAT ACK with invalid timestamp"
                          "received for transport: %p\n",
                           __FUNCTION__, link);
            return SCTP_DISPOSITION_DISCARD;
      }

      /* 8.3 Upon the receipt of the HEARTBEAT ACK, the sender of
       * the HEARTBEAT should clear the error counter of the
       * destination transport address to which the HEARTBEAT was
       * sent and mark the destination transport address as active if
       * it is not so marked.
       */
      sctp_add_cmd_sf(commands, SCTP_CMD_TRANSPORT_ON, SCTP_TRANSPORT(link));

      return SCTP_DISPOSITION_CONSUME;
}

/* Helper function to send out an abort for the restart
 * condition.
 */
static int sctp_sf_send_restart_abort(union sctp_addr *ssa,
                              struct sctp_chunk *init,
                              sctp_cmd_seq_t *commands)
{
      int len;
      struct sctp_packet *pkt;
      union sctp_addr_param *addrparm;
      struct sctp_errhdr *errhdr;
      struct sctp_endpoint *ep;
      char buffer[sizeof(struct sctp_errhdr)+sizeof(union sctp_addr_param)];
      struct sctp_af *af = sctp_get_af_specific(ssa->v4.sin_family);

      /* Build the error on the stack.   We are way to malloc crazy
       * throughout the code today.
       */
      errhdr = (struct sctp_errhdr *)buffer;
      addrparm = (union sctp_addr_param *)errhdr->variable;

      /* Copy into a parm format. */
      len = af->to_addr_param(ssa, addrparm);
      len += sizeof(sctp_errhdr_t);

      errhdr->cause = SCTP_ERROR_RESTART;
      errhdr->length = htons(len);

      /* Assign to the control socket. */
      ep = sctp_sk((sctp_get_ctl_sock()))->ep;

      /* Association is NULL since this may be a restart attack and we
       * want to send back the attacker's vtag.
       */
      pkt = sctp_abort_pkt_new(ep, NULL, init, errhdr, len);

      if (!pkt)
            goto out;
      sctp_add_cmd_sf(commands, SCTP_CMD_SEND_PKT, SCTP_PACKET(pkt));

      SCTP_INC_STATS(SCTP_MIB_OUTCTRLCHUNKS);

      /* Discard the rest of the inbound packet. */
      sctp_add_cmd_sf(commands, SCTP_CMD_DISCARD_PACKET, SCTP_NULL());

out:
      /* Even if there is no memory, treat as a failure so
       * the packet will get dropped.
       */
      return 0;
}

/* A restart is occurring, check to make sure no new addresses
 * are being added as we may be under a takeover attack.
 */
static int sctp_sf_check_restart_addrs(const struct sctp_association *new_asoc,
                               const struct sctp_association *asoc,
                               struct sctp_chunk *init,
                               sctp_cmd_seq_t *commands)
{
      struct sctp_transport *new_addr, *addr;
      struct list_head *pos, *pos2;
      int found;

      /* Implementor's Guide - Sectin 5.2.2
       * ...
       * Before responding the endpoint MUST check to see if the
       * unexpected INIT adds new addresses to the association. If new
       * addresses are added to the association, the endpoint MUST respond
       * with an ABORT..
       */

      /* Search through all current addresses and make sure
       * we aren't adding any new ones.
       */
      new_addr = NULL;
      found = 0;

      list_for_each(pos, &new_asoc->peer.transport_addr_list) {
            new_addr = list_entry(pos, struct sctp_transport, transports);
            found = 0;
            list_for_each(pos2, &asoc->peer.transport_addr_list) {
                  addr = list_entry(pos2, struct sctp_transport,
                                transports);
                  if (sctp_cmp_addr_exact(&new_addr->ipaddr,
                                    &addr->ipaddr)) {
                        found = 1;
                        break;
                  }
            }
            if (!found)
                  break;
      }

      /* If a new address was added, ABORT the sender. */
      if (!found && new_addr) {
            sctp_sf_send_restart_abort(&new_addr->ipaddr, init, commands);
      }

      /* Return success if all addresses were found. */
      return found;
}

/* Populate the verification/tie tags based on overlapping INIT
 * scenario.
 *
 * Note: Do not use in CLOSED or SHUTDOWN-ACK-SENT state.
 */
static void sctp_tietags_populate(struct sctp_association *new_asoc,
                          const struct sctp_association *asoc)
{
      switch (asoc->state) {

      /* 5.2.1 INIT received in COOKIE-WAIT or COOKIE-ECHOED State */

      case SCTP_STATE_COOKIE_WAIT:
            new_asoc->c.my_vtag     = asoc->c.my_vtag;
            new_asoc->c.my_ttag     = asoc->c.my_vtag;
            new_asoc->c.peer_ttag   = 0;
            break;

      case SCTP_STATE_COOKIE_ECHOED:
            new_asoc->c.my_vtag     = asoc->c.my_vtag;
            new_asoc->c.my_ttag     = asoc->c.my_vtag;
            new_asoc->c.peer_ttag   = asoc->c.peer_vtag;
            break;

      /* 5.2.2 Unexpected INIT in States Other than CLOSED, COOKIE-ECHOED,
       * COOKIE-WAIT and SHUTDOWN-ACK-SENT
       */
      default:
            new_asoc->c.my_ttag   = asoc->c.my_vtag;
            new_asoc->c.peer_ttag = asoc->c.peer_vtag;
            break;
      };

      /* Other parameters for the endpoint SHOULD be copied from the
       * existing parameters of the association (e.g. number of
       * outbound streams) into the INIT ACK and cookie.
       */
      new_asoc->rwnd                  = asoc->rwnd;
      new_asoc->c.sinit_num_ostreams  = asoc->c.sinit_num_ostreams;
      new_asoc->c.sinit_max_instreams = asoc->c.sinit_max_instreams;
      new_asoc->c.initial_tsn         = asoc->c.initial_tsn;
}

/*
 * Compare vtag/tietag values to determine unexpected COOKIE-ECHO
 * handling action.
 *
 * RFC 2960 5.2.4 Handle a COOKIE ECHO when a TCB exists.
 *
 * Returns value representing action to be taken.   These action values
 * correspond to Action/Description values in RFC 2960, Table 2.
 */
static char sctp_tietags_compare(struct sctp_association *new_asoc,
                         const struct sctp_association *asoc)
{
      /* In this case, the peer may have restarted.  */
      if ((asoc->c.my_vtag != new_asoc->c.my_vtag) &&
          (asoc->c.peer_vtag != new_asoc->c.peer_vtag) &&
          (asoc->c.my_vtag == new_asoc->c.my_ttag) &&
          (asoc->c.peer_vtag == new_asoc->c.peer_ttag))
            return 'A';

      /* Collision case B. */
      if ((asoc->c.my_vtag == new_asoc->c.my_vtag) &&
          ((asoc->c.peer_vtag != new_asoc->c.peer_vtag) ||
           (0 == asoc->c.peer_vtag))) {
            return 'B';
      }

      /* Collision case D. */
      if ((asoc->c.my_vtag == new_asoc->c.my_vtag) &&
          (asoc->c.peer_vtag == new_asoc->c.peer_vtag))
            return 'D';

      /* Collision case C. */
      if ((asoc->c.my_vtag != new_asoc->c.my_vtag) &&
          (asoc->c.peer_vtag == new_asoc->c.peer_vtag) &&
          (0 == new_asoc->c.my_ttag) &&
          (0 == new_asoc->c.peer_ttag))
            return 'C';

      /* No match to any of the special cases; discard this packet. */
      return 'E';
}

/* Common helper routine for both duplicate and simulataneous INIT
 * chunk handling.
 */
static sctp_disposition_t sctp_sf_do_unexpected_init(
      const struct sctp_endpoint *ep,
      const struct sctp_association *asoc,
      const sctp_subtype_t type,
      void *arg, sctp_cmd_seq_t *commands)
{
      sctp_disposition_t retval;
      struct sctp_chunk *chunk = arg;
      struct sctp_chunk *repl;
      struct sctp_association *new_asoc;
      struct sctp_chunk *err_chunk;
      struct sctp_packet *packet;
      sctp_unrecognized_param_t *unk_param;
      int len;

      /* 6.10 Bundling
       * An endpoint MUST NOT bundle INIT, INIT ACK or
       * SHUTDOWN COMPLETE with any other chunks.
       *
       * IG Section 2.11.2
       * Furthermore, we require that the receiver of an INIT chunk MUST
       * enforce these rules by silently discarding an arriving packet
       * with an INIT chunk that is bundled with other chunks.
       */
      if (!chunk->singleton)
            return sctp_sf_pdiscard(ep, asoc, type, arg, commands);

      /* 3.1 A packet containing an INIT chunk MUST have a zero Verification
       * Tag. 
       */
      if (chunk->sctp_hdr->vtag != 0)
            return sctp_sf_tabort_8_4_8(ep, asoc, type, arg, commands);

      /* Make sure that the INIT chunk has a valid length.
       * In this case, we generate a protocol violation since we have
       * an association established.
       */
      if (!sctp_chunk_length_valid(chunk, sizeof(sctp_init_chunk_t)))
            return sctp_sf_violation_chunklen(ep, asoc, type, arg,
                                      commands);
      /* Grab the INIT header.  */
      chunk->subh.init_hdr = (sctp_inithdr_t *) chunk->skb->data;

      /* Tag the variable length parameters.  */
      chunk->param_hdr.v = skb_pull(chunk->skb, sizeof(sctp_inithdr_t));

      /* Verify the INIT chunk before processing it. */
      err_chunk = NULL;
      if (!sctp_verify_init(asoc, chunk->chunk_hdr->type,
                        (sctp_init_chunk_t *)chunk->chunk_hdr, chunk,
                        &err_chunk)) {
            /* This chunk contains fatal error. It is to be discarded.
             * Send an ABORT, with causes if there is any.
             */
            if (err_chunk) {
                  packet = sctp_abort_pkt_new(ep, asoc, arg,
                              (__u8 *)(err_chunk->chunk_hdr) +
                              sizeof(sctp_chunkhdr_t),
                              ntohs(err_chunk->chunk_hdr->length) -
                              sizeof(sctp_chunkhdr_t));

                  if (packet) {
                        sctp_add_cmd_sf(commands, SCTP_CMD_SEND_PKT,
                                    SCTP_PACKET(packet));
                        SCTP_INC_STATS(SCTP_MIB_OUTCTRLCHUNKS);
                        retval = SCTP_DISPOSITION_CONSUME;
                  } else {
                        retval = SCTP_DISPOSITION_NOMEM;
                  }
                  goto cleanup;
            } else {
                  return sctp_sf_tabort_8_4_8(ep, asoc, type, arg,
                                        commands);
            }
      }

      /*
       * Other parameters for the endpoint SHOULD be copied from the
       * existing parameters of the association (e.g. number of
       * outbound streams) into the INIT ACK and cookie.
       * FIXME:  We are copying parameters from the endpoint not the
       * association.
       */
      new_asoc = sctp_make_temp_asoc(ep, chunk, GFP_ATOMIC);
      if (!new_asoc)
            goto nomem;

      /* In the outbound INIT ACK the endpoint MUST copy its current
       * Verification Tag and Peers Verification tag into a reserved
       * place (local tie-tag and per tie-tag) within the state cookie.
       */
      if (!sctp_process_init(new_asoc, chunk->chunk_hdr->type,
                         sctp_source(chunk),
                         (sctp_init_chunk_t *)chunk->chunk_hdr,
                         GFP_ATOMIC)) {
            retval = SCTP_DISPOSITION_NOMEM;
            goto nomem_init;
      }

      /* Make sure no new addresses are being added during the
       * restart.   Do not do this check for COOKIE-WAIT state,
       * since there are no peer addresses to check against.
       * Upon return an ABORT will have been sent if needed.
       */
      if (!sctp_state(asoc, COOKIE_WAIT)) {
            if (!sctp_sf_check_restart_addrs(new_asoc, asoc, chunk,
                                     commands)) {
                  retval = SCTP_DISPOSITION_CONSUME;
                  goto cleanup_asoc;
            }
      }

      sctp_tietags_populate(new_asoc, asoc);

      /* B) "Z" shall respond immediately with an INIT ACK chunk.  */

      /* If there are errors need to be reported for unknown parameters,
       * make sure to reserve enough room in the INIT ACK for them.
       */
      len = 0;
      if (err_chunk) {
            len = ntohs(err_chunk->chunk_hdr->length) -
                  sizeof(sctp_chunkhdr_t);
      }

      if (sctp_assoc_set_bind_addr_from_ep(new_asoc, GFP_ATOMIC) < 0)
            goto nomem;

      repl = sctp_make_init_ack(new_asoc, chunk, GFP_ATOMIC, len);
      if (!repl)
            goto nomem;

      /* If there are errors need to be reported for unknown parameters,
       * include them in the outgoing INIT ACK as "Unrecognized parameter"
       * parameter.
       */
      if (err_chunk) {
            /* Get the "Unrecognized parameter" parameter(s) out of the
             * ERROR chunk generated by sctp_verify_init(). Since the
             * error cause code for "unknown parameter" and the
             * "Unrecognized parameter" type is the same, we can
             * construct the parameters in INIT ACK by copying the
             * ERROR causes over.
             */
            unk_param = (sctp_unrecognized_param_t *)
                      ((__u8 *)(err_chunk->chunk_hdr) +
                      sizeof(sctp_chunkhdr_t));
            /* Replace the cause code with the "Unrecognized parameter"
             * parameter type.
             */
            sctp_addto_chunk(repl, len, unk_param);
      }

      sctp_add_cmd_sf(commands, SCTP_CMD_NEW_ASOC, SCTP_ASOC(new_asoc));
      sctp_add_cmd_sf(commands, SCTP_CMD_REPLY, SCTP_CHUNK(repl));

      /*
       * Note: After sending out INIT ACK with the State Cookie parameter,
       * "Z" MUST NOT allocate any resources for this new association.
       * Otherwise, "Z" will be vulnerable to resource attacks.
       */
      sctp_add_cmd_sf(commands, SCTP_CMD_DELETE_TCB, SCTP_NULL());
      retval = SCTP_DISPOSITION_CONSUME;

cleanup:
      if (err_chunk)
            sctp_chunk_free(err_chunk);
      return retval;
nomem:
      retval = SCTP_DISPOSITION_NOMEM;
      goto cleanup;
nomem_init:
cleanup_asoc:
      sctp_association_free(new_asoc);
      goto cleanup;
}

/*
 * Handle simultanous INIT.
 * This means we started an INIT and then we got an INIT request from
 * our peer.
 *
 * Section: 5.2.1 INIT received in COOKIE-WAIT or COOKIE-ECHOED State (Item B)
 * This usually indicates an initialization collision, i.e., each
 * endpoint is attempting, at about the same time, to establish an
 * association with the other endpoint.
 *
 * Upon receipt of an INIT in the COOKIE-WAIT or COOKIE-ECHOED state, an
 * endpoint MUST respond with an INIT ACK using the same parameters it
 * sent in its original INIT chunk (including its Verification Tag,
 * unchanged). These original parameters are combined with those from the
 * newly received INIT chunk. The endpoint shall also generate a State
 * Cookie with the INIT ACK. The endpoint uses the parameters sent in its
 * INIT to calculate the State Cookie.
 *
 * After that, the endpoint MUST NOT change its state, the T1-init
 * timer shall be left running and the corresponding TCB MUST NOT be
 * destroyed. The normal procedures for handling State Cookies when
 * a TCB exists will resolve the duplicate INITs to a single association.
 *
 * For an endpoint that is in the COOKIE-ECHOED state it MUST populate
 * its Tie-Tags with the Tag information of itself and its peer (see
 * section 5.2.2 for a description of the Tie-Tags).
 *
 * Verification Tag: Not explicit, but an INIT can not have a valid
 * verification tag, so we skip the check.
 *
 * Inputs
 * (endpoint, asoc, chunk)
 *
 * Outputs
 * (asoc, reply_msg, msg_up, timers, counters)
 *
 * The return value is the disposition of the chunk.
 */
sctp_disposition_t sctp_sf_do_5_2_1_siminit(const struct sctp_endpoint *ep,
                            const struct sctp_association *asoc,
                            const sctp_subtype_t type,
                            void *arg,
                            sctp_cmd_seq_t *commands)
{
      /* Call helper to do the real work for both simulataneous and
       * duplicate INIT chunk handling.
       */
      return sctp_sf_do_unexpected_init(ep, asoc, type, arg, commands);
}

/*
 * Handle duplicated INIT messages.  These are usually delayed
 * restransmissions.
 *
 * Section: 5.2.2 Unexpected INIT in States Other than CLOSED,
 * COOKIE-ECHOED and COOKIE-WAIT
 *
 * Unless otherwise stated, upon reception of an unexpected INIT for
 * this association, the endpoint shall generate an INIT ACK with a
 * State Cookie.  In the outbound INIT ACK the endpoint MUST copy its
 * current Verification Tag and peer's Verification Tag into a reserved
 * place within the state cookie.  We shall refer to these locations as
 * the Peer's-Tie-Tag and the Local-Tie-Tag.  The outbound SCTP packet
 * containing this INIT ACK MUST carry a Verification Tag value equal to
 * the Initiation Tag found in the unexpected INIT.  And the INIT ACK
 * MUST contain a new Initiation Tag (randomly generated see Section
 * 5.3.1).  Other parameters for the endpoint SHOULD be copied from the
 * existing parameters of the association (e.g. number of outbound
 * streams) into the INIT ACK and cookie.
 *
 * After sending out the INIT ACK, the endpoint shall take no further
 * actions, i.e., the existing association, including its current state,
 * and the corresponding TCB MUST NOT be changed.
 *
 * Note: Only when a TCB exists and the association is not in a COOKIE-
 * WAIT state are the Tie-Tags populated.  For a normal association INIT
 * (i.e. the endpoint is in a COOKIE-WAIT state), the Tie-Tags MUST be
 * set to 0 (indicating that no previous TCB existed).  The INIT ACK and
 * State Cookie are populated as specified in section 5.2.1.
 *
 * Verification Tag: Not specified, but an INIT has no way of knowing
 * what the verification tag could be, so we ignore it.
 *
 * Inputs
 * (endpoint, asoc, chunk)
 *
 * Outputs
 * (asoc, reply_msg, msg_up, timers, counters)
 *
 * The return value is the disposition of the chunk.
 */
sctp_disposition_t sctp_sf_do_5_2_2_dupinit(const struct sctp_endpoint *ep,
                              const struct sctp_association *asoc,
                              const sctp_subtype_t type,
                              void *arg,
                              sctp_cmd_seq_t *commands)
{
      /* Call helper to do the real work for both simulataneous and
       * duplicate INIT chunk handling.
       */
      return sctp_sf_do_unexpected_init(ep, asoc, type, arg, commands);
}



/* Unexpected COOKIE-ECHO handler for peer restart (Table 2, action 'A')
 *
 * Section 5.2.4
 *  A)  In this case, the peer may have restarted.
 */
static sctp_disposition_t sctp_sf_do_dupcook_a(const struct sctp_endpoint *ep,
                              const struct sctp_association *asoc,
                              struct sctp_chunk *chunk,
                              sctp_cmd_seq_t *commands,
                              struct sctp_association *new_asoc)
{
      sctp_init_chunk_t *peer_init;
      struct sctp_ulpevent *ev;
      struct sctp_chunk *repl;
      struct sctp_chunk *err;
      sctp_disposition_t disposition;

      /* new_asoc is a brand-new association, so these are not yet
       * side effects--it is safe to run them here.
       */
      peer_init = &chunk->subh.cookie_hdr->c.peer_init[0];

      if (!sctp_process_init(new_asoc, chunk->chunk_hdr->type,
                         sctp_source(chunk), peer_init,
                         GFP_ATOMIC))
            goto nomem;

      /* Make sure no new addresses are being added during the
       * restart.  Though this is a pretty complicated attack
       * since you'd have to get inside the cookie.
       */
      if (!sctp_sf_check_restart_addrs(new_asoc, asoc, chunk, commands)) {
            return SCTP_DISPOSITION_CONSUME;
      }

      /* If the endpoint is in the SHUTDOWN-ACK-SENT state and recognizes
       * the peer has restarted (Action A), it MUST NOT setup a new
       * association but instead resend the SHUTDOWN ACK and send an ERROR
       * chunk with a "Cookie Received while Shutting Down" error cause to
       * its peer.
      */
      if (sctp_state(asoc, SHUTDOWN_ACK_SENT)) {
            disposition = sctp_sf_do_9_2_reshutack(ep, asoc,
                        SCTP_ST_CHUNK(chunk->chunk_hdr->type),
                        chunk, commands);
            if (SCTP_DISPOSITION_NOMEM == disposition)
                  goto nomem;

            err = sctp_make_op_error(asoc, chunk,
                               SCTP_ERROR_COOKIE_IN_SHUTDOWN,
                               NULL, 0);
            if (err)
                  sctp_add_cmd_sf(commands, SCTP_CMD_REPLY,
                              SCTP_CHUNK(err));

            return SCTP_DISPOSITION_CONSUME;
      }

      /* For now, fail any unsent/unacked data.  Consider the optional
       * choice of resending of this data.
       */
      sctp_add_cmd_sf(commands, SCTP_CMD_PURGE_OUTQUEUE, SCTP_NULL());

      /* Update the content of current association. */
      sctp_add_cmd_sf(commands, SCTP_CMD_UPDATE_ASSOC, SCTP_ASOC(new_asoc));

      repl = sctp_make_cookie_ack(new_asoc, chunk);
      if (!repl)
            goto nomem;

      sctp_add_cmd_sf(commands, SCTP_CMD_REPLY, SCTP_CHUNK(repl));

      /* Report association restart to upper layer. */
      ev = sctp_ulpevent_make_assoc_change(asoc, 0, SCTP_RESTART, 0,
                                   new_asoc->c.sinit_num_ostreams,
                                   new_asoc->c.sinit_max_instreams,
                                   GFP_ATOMIC);
      if (!ev)
            goto nomem_ev;

      sctp_add_cmd_sf(commands, SCTP_CMD_EVENT_ULP, SCTP_ULPEVENT(ev));
      return SCTP_DISPOSITION_CONSUME;

nomem_ev:
      sctp_chunk_free(repl);
nomem:
      return SCTP_DISPOSITION_NOMEM;
}

/* Unexpected COOKIE-ECHO handler for setup collision (Table 2, action 'B')
 *
 * Section 5.2.4
 *   B) In this case, both sides may be attempting to start an association
 *      at about the same time but the peer endpoint started its INIT
 *      after responding to the local endpoint's INIT
 */
/* This case represents an initialization collision.  */
static sctp_disposition_t sctp_sf_do_dupcook_b(const struct sctp_endpoint *ep,
                              const struct sctp_association *asoc,
                              struct sctp_chunk *chunk,
                              sctp_cmd_seq_t *commands,
                              struct sctp_association *new_asoc)
{
      sctp_init_chunk_t *peer_init;
      struct sctp_ulpevent *ev;
      struct sctp_chunk *repl;

      /* new_asoc is a brand-new association, so these are not yet
       * side effects--it is safe to run them here.
       */
      peer_init = &chunk->subh.cookie_hdr->c.peer_init[0];
      if (!sctp_process_init(new_asoc, chunk->chunk_hdr->type,
                         sctp_source(chunk), peer_init,
                         GFP_ATOMIC))
            goto nomem;

      /* Update the content of current association.  */
      sctp_add_cmd_sf(commands, SCTP_CMD_UPDATE_ASSOC, SCTP_ASOC(new_asoc));
      sctp_add_cmd_sf(commands, SCTP_CMD_NEW_STATE,
                  SCTP_STATE(SCTP_STATE_ESTABLISHED));
      SCTP_INC_STATS(SCTP_MIB_CURRESTAB);
      sctp_add_cmd_sf(commands, SCTP_CMD_HB_TIMERS_START, SCTP_NULL());

      repl = sctp_make_cookie_ack(new_asoc, chunk);
      if (!repl)
            goto nomem;

      sctp_add_cmd_sf(commands, SCTP_CMD_REPLY, SCTP_CHUNK(repl));
      sctp_add_cmd_sf(commands, SCTP_CMD_TRANSMIT, SCTP_NULL());

      /* RFC 2960 5.1 Normal Establishment of an Association
       *
       * D) IMPLEMENTATION NOTE: An implementation may choose to
       * send the Communication Up notification to the SCTP user
       * upon reception of a valid COOKIE ECHO chunk.
       */
      ev = sctp_ulpevent_make_assoc_change(asoc, 0, SCTP_COMM_UP, 0,
                                   new_asoc->c.sinit_num_ostreams,
                                   new_asoc->c.sinit_max_instreams,
                                   GFP_ATOMIC);
      if (!ev)
            goto nomem_ev;

      sctp_add_cmd_sf(commands, SCTP_CMD_EVENT_ULP, SCTP_ULPEVENT(ev));

      /* Sockets API Draft Section 5.3.1.6
       * When a peer sends a Adaption Layer Indication parameter , SCTP
       * delivers this notification to inform the application that of the
       * peers requested adaption layer.
       */
      if (asoc->peer.adaption_ind) {
            ev = sctp_ulpevent_make_adaption_indication(asoc, GFP_ATOMIC);
            if (!ev)
                  goto nomem_ev;

            sctp_add_cmd_sf(commands, SCTP_CMD_EVENT_ULP,
                        SCTP_ULPEVENT(ev));
      }

      return SCTP_DISPOSITION_CONSUME;

nomem_ev:
      sctp_chunk_free(repl);
nomem:
      return SCTP_DISPOSITION_NOMEM;
}

/* Unexpected COOKIE-ECHO handler for setup collision (Table 2, action 'C')
 *
 * Section 5.2.4
 *  C) In this case, the local endpoint's cookie has arrived late.
 *     Before it arrived, the local endpoint sent an INIT and received an
 *     INIT-ACK and finally sent a COOKIE ECHO with the peer's same tag
 *     but a new tag of its own.
 */
/* This case represents an initialization collision.  */
static sctp_disposition_t sctp_sf_do_dupcook_c(const struct sctp_endpoint *ep,
                              const struct sctp_association *asoc,
                              struct sctp_chunk *chunk,
                              sctp_cmd_seq_t *commands,
                              struct sctp_association *new_asoc)
{
      /* The cookie should be silently discarded.
       * The endpoint SHOULD NOT change states and should leave
       * any timers running.
       */
      return SCTP_DISPOSITION_DISCARD;
}

/* Unexpected COOKIE-ECHO handler lost chunk (Table 2, action 'D')
 *
 * Section 5.2.4
 *
 * D) When both local and remote tags match the endpoint should always
 *    enter the ESTABLISHED state, if it has not already done so.
 */
/* This case represents an initialization collision.  */
static sctp_disposition_t sctp_sf_do_dupcook_d(const struct sctp_endpoint *ep,
                              const struct sctp_association *asoc,
                              struct sctp_chunk *chunk,
                              sctp_cmd_seq_t *commands,
                              struct sctp_association *new_asoc)
{
      struct sctp_ulpevent *ev = NULL;
      struct sctp_chunk *repl;

      /* Clarification from Implementor's Guide:
       * D) When both local and remote tags match the endpoint should
         * enter the ESTABLISHED state, if it is in the COOKIE-ECHOED state.
         * It should stop any cookie timer that may be running and send
         * a COOKIE ACK.
       */

      /* Don't accidentally move back into established state. */
      if (asoc->state < SCTP_STATE_ESTABLISHED) {
            sctp_add_cmd_sf(commands, SCTP_CMD_TIMER_STOP,
                        SCTP_TO(SCTP_EVENT_TIMEOUT_T1_COOKIE));
            sctp_add_cmd_sf(commands, SCTP_CMD_NEW_STATE,
                        SCTP_STATE(SCTP_STATE_ESTABLISHED));
            SCTP_INC_STATS(SCTP_MIB_CURRESTAB);
            sctp_add_cmd_sf(commands, SCTP_CMD_HB_TIMERS_START,
                        SCTP_NULL());

            /* RFC 2960 5.1 Normal Establishment of an Association
             *
             * D) IMPLEMENTATION NOTE: An implementation may choose
             * to send the Communication Up notification to the
             * SCTP user upon reception of a valid COOKIE
             * ECHO chunk.
             */
            ev = sctp_ulpevent_make_assoc_change(new_asoc, 0,
                                   SCTP_COMM_UP, 0,
                                   new_asoc->c.sinit_num_ostreams,
                                   new_asoc->c.sinit_max_instreams,
                                             GFP_ATOMIC);
            if (!ev)
                  goto nomem;
            sctp_add_cmd_sf(commands, SCTP_CMD_EVENT_ULP,
                        SCTP_ULPEVENT(ev));

            /* Sockets API Draft Section 5.3.1.6
             * When a peer sends a Adaption Layer Indication parameter,
             * SCTP delivers this notification to inform the application
             * that of the peers requested adaption layer.
             */
            if (new_asoc->peer.adaption_ind) {
                  ev = sctp_ulpevent_make_adaption_indication(new_asoc,
                                                 GFP_ATOMIC);
                  if (!ev)
                        goto nomem;

                  sctp_add_cmd_sf(commands, SCTP_CMD_EVENT_ULP,
                              SCTP_ULPEVENT(ev));
            }
      }
      sctp_add_cmd_sf(commands, SCTP_CMD_TRANSMIT, SCTP_NULL());

      repl = sctp_make_cookie_ack(new_asoc, chunk);
      if (!repl)
            goto nomem;

      sctp_add_cmd_sf(commands, SCTP_CMD_REPLY, SCTP_CHUNK(repl));
      sctp_add_cmd_sf(commands, SCTP_CMD_TRANSMIT, SCTP_NULL());

      return SCTP_DISPOSITION_CONSUME;

nomem:
      if (ev)
            sctp_ulpevent_free(ev);
      return SCTP_DISPOSITION_NOMEM;
}

/*
 * Handle a duplicate COOKIE-ECHO.  This usually means a cookie-carrying
 * chunk was retransmitted and then delayed in the network.
 *
 * Section: 5.2.4 Handle a COOKIE ECHO when a TCB exists
 *
 * Verification Tag: None.  Do cookie validation.
 *
 * Inputs
 * (endpoint, asoc, chunk)
 *
 * Outputs
 * (asoc, reply_msg, msg_up, timers, counters)
 *
 * The return value is the disposition of the chunk.
 */
sctp_disposition_t sctp_sf_do_5_2_4_dupcook(const struct sctp_endpoint *ep,
                              const struct sctp_association *asoc,
                              const sctp_subtype_t type,
                              void *arg,
                              sctp_cmd_seq_t *commands)
{
      sctp_disposition_t retval;
      struct sctp_chunk *chunk = arg;
      struct sctp_association *new_asoc;
      int error = 0;
      char action;
      struct sctp_chunk *err_chk_p;

      /* Make sure that the chunk has a valid length from the protocol
       * perspective.  In this case check to make sure we have at least
       * enough for the chunk header.  Cookie length verification is
       * done later.
       */
      if (!sctp_chunk_length_valid(chunk, sizeof(sctp_chunkhdr_t)))
            return sctp_sf_violation_chunklen(ep, asoc, type, arg,
                                      commands);

      /* "Decode" the chunk.  We have no optional parameters so we
       * are in good shape.
       */
        chunk->subh.cookie_hdr = (struct sctp_signed_cookie *)chunk->skb->data;
      if (!pskb_pull(chunk->skb, ntohs(chunk->chunk_hdr->length) -
                              sizeof(sctp_chunkhdr_t)))
            goto nomem;

      /* In RFC 2960 5.2.4 3, if both Verification Tags in the State Cookie
       * of a duplicate COOKIE ECHO match the Verification Tags of the
       * current association, consider the State Cookie valid even if
       * the lifespan is exceeded.
       */
      new_asoc = sctp_unpack_cookie(ep, asoc, chunk, GFP_ATOMIC, &error,
                              &err_chk_p);

      /* FIXME:
       * If the re-build failed, what is the proper error path
       * from here?
       *
       * [We should abort the association. --piggy]
       */
      if (!new_asoc) {
            /* FIXME: Several errors are possible.  A bad cookie should
             * be silently discarded, but think about logging it too.
             */
            switch (error) {
            case -SCTP_IERROR_NOMEM:
                  goto nomem;

            case -SCTP_IERROR_STALE_COOKIE:
                  sctp_send_stale_cookie_err(ep, asoc, chunk, commands,
                                       err_chk_p);
                  return sctp_sf_pdiscard(ep, asoc, type, arg, commands);
            case -SCTP_IERROR_BAD_SIG:
            default:
                  return sctp_sf_pdiscard(ep, asoc, type, arg, commands);
            };
      }

      /* Compare the tie_tag in cookie with the verification tag of
       * current association.
       */
      action = sctp_tietags_compare(new_asoc, asoc);

      switch (action) {
      case 'A': /* Association restart. */
            retval = sctp_sf_do_dupcook_a(ep, asoc, chunk, commands,
                                    new_asoc);
            break;

      case 'B': /* Collision case B. */
            retval = sctp_sf_do_dupcook_b(ep, asoc, chunk, commands,
                                    new_asoc);
            break;

      case 'C': /* Collision case C. */
            retval = sctp_sf_do_dupcook_c(ep, asoc, chunk, commands,
                                    new_asoc);
            break;

      case 'D': /* Collision case D. */
            retval = sctp_sf_do_dupcook_d(ep, asoc, chunk, commands,
                                    new_asoc);
            break;

      default: /* Discard packet for all others. */
            retval = sctp_sf_pdiscard(ep, asoc, type, arg, commands);
            break;
        };

      /* Delete the tempory new association. */
      sctp_add_cmd_sf(commands, SCTP_CMD_NEW_ASOC, SCTP_ASOC(new_asoc));
      sctp_add_cmd_sf(commands, SCTP_CMD_DELETE_TCB, SCTP_NULL());

      return retval;

nomem:
      return SCTP_DISPOSITION_NOMEM;
}

/*
 * Process an ABORT.  (SHUTDOWN-PENDING state)
 *
 * See sctp_sf_do_9_1_abort().
 */
sctp_disposition_t sctp_sf_shutdown_pending_abort(
      const struct sctp_endpoint *ep,
      const struct sctp_association *asoc,
      const sctp_subtype_t type,
      void *arg,
      sctp_cmd_seq_t *commands)
{
      struct sctp_chunk *chunk = arg;

      if (!sctp_vtag_verify_either(chunk, asoc))
            return sctp_sf_pdiscard(ep, asoc, type, arg, commands);

      /* Make sure that the ABORT chunk has a valid length.
       * Since this is an ABORT chunk, we have to discard it
       * because of the following text:
       * RFC 2960, Section 3.3.7
       *    If an endpoint receives an ABORT with a format error or for an
       *    association that doesn't exist, it MUST silently discard it.
       * Becasue the length is "invalid", we can't really discard just
       * as we do not know its true length.  So, to be safe, discard the
       * packet.
       */
      if (!sctp_chunk_length_valid(chunk, sizeof(sctp_abort_chunk_t)))
            return sctp_sf_pdiscard(ep, asoc, type, arg, commands);

      /* Stop the T5-shutdown guard timer.  */
      sctp_add_cmd_sf(commands, SCTP_CMD_TIMER_STOP,
                  SCTP_TO(SCTP_EVENT_TIMEOUT_T5_SHUTDOWN_GUARD));

      return sctp_sf_do_9_1_abort(ep, asoc, type, arg, commands);
}

/*
 * Process an ABORT.  (SHUTDOWN-SENT state)
 *
 * See sctp_sf_do_9_1_abort().
 */
sctp_disposition_t sctp_sf_shutdown_sent_abort(const struct sctp_endpoint *ep,
                              const struct sctp_association *asoc,
                              const sctp_subtype_t type,
                              void *arg,
                              sctp_cmd_seq_t *commands)
{
      struct sctp_chunk *chunk = arg;

      if (!sctp_vtag_verify_either(chunk, asoc))
            return sctp_sf_pdiscard(ep, asoc, type, arg, commands);

      /* Make sure that the ABORT chunk has a valid length.
       * Since this is an ABORT chunk, we have to discard it
       * because of the following text:
       * RFC 2960, Section 3.3.7
       *    If an endpoint receives an ABORT with a format error or for an
       *    association that doesn't exist, it MUST silently discard it.
       * Becasue the length is "invalid", we can't really discard just
       * as we do not know its true length.  So, to be safe, discard the
       * packet.
       */
      if (!sctp_chunk_length_valid(chunk, sizeof(sctp_abort_chunk_t)))
            return sctp_sf_pdiscard(ep, asoc, type, arg, commands);

      /* Stop the T2-shutdown timer. */
      sctp_add_cmd_sf(commands, SCTP_CMD_TIMER_STOP,
                  SCTP_TO(SCTP_EVENT_TIMEOUT_T2_SHUTDOWN));

      /* Stop the T5-shutdown guard timer.  */
      sctp_add_cmd_sf(commands, SCTP_CMD_TIMER_STOP,
                  SCTP_TO(SCTP_EVENT_TIMEOUT_T5_SHUTDOWN_GUARD));

      return sctp_sf_do_9_1_abort(ep, asoc, type, arg, commands);
}

/*
 * Process an ABORT.  (SHUTDOWN-ACK-SENT state)
 *
 * See sctp_sf_do_9_1_abort().
 */
sctp_disposition_t sctp_sf_shutdown_ack_sent_abort(
      const struct sctp_endpoint *ep,
      const struct sctp_association *asoc,
      const sctp_subtype_t type,
      void *arg,
      sctp_cmd_seq_t *commands)
{
      /* The same T2 timer, so we should be able to use
       * common function with the SHUTDOWN-SENT state.
       */
      return sctp_sf_shutdown_sent_abort(ep, asoc, type, arg, commands);
}

/*
 * Handle an Error received in COOKIE_ECHOED state.
 *
 * Only handle the error type of stale COOKIE Error, the other errors will
 * be ignored.
 *
 * Inputs
 * (endpoint, asoc, chunk)
 *
 * Outputs
 * (asoc, reply_msg, msg_up, timers, counters)
 *
 * The return value is the disposition of the chunk.
 */
sctp_disposition_t sctp_sf_cookie_echoed_err(const struct sctp_endpoint *ep,
                              const struct sctp_association *asoc,
                              const sctp_subtype_t type,
                              void *arg,
                              sctp_cmd_seq_t *commands)
{
      struct sctp_chunk *chunk = arg;
      sctp_errhdr_t *err;

      if (!sctp_vtag_verify(chunk, asoc))
            return sctp_sf_pdiscard(ep, asoc, type, arg, commands);

      /* Make sure that the ERROR chunk has a valid length.
       * The parameter walking depends on this as well.
       */
      if (!sctp_chunk_length_valid(chunk, sizeof(sctp_operr_chunk_t)))
            return sctp_sf_violation_chunklen(ep, asoc, type, arg,
                                      commands);

      /* Process the error here */
      /* FUTURE FIXME:  When PR-SCTP related and other optional
       * parms are emitted, this will have to change to handle multiple
       * errors.
       */
      sctp_walk_errors(err, chunk->chunk_hdr) {
            if (SCTP_ERROR_STALE_COOKIE == err->cause)
                  return sctp_sf_do_5_2_6_stale(ep, asoc, type, 
                                          arg, commands);
      }

      /* It is possible to have malformed error causes, and that
       * will cause us to end the walk early.  However, since
       * we are discarding the packet, there should be no adverse
       * affects.
       */
      return sctp_sf_pdiscard(ep, asoc, type, arg, commands);
}

/*
 * Handle a Stale COOKIE Error
 *
 * Section: 5.2.6 Handle Stale COOKIE Error
 * If the association is in the COOKIE-ECHOED state, the endpoint may elect
 * one of the following three alternatives.
 * ...
 * 3) Send a new INIT chunk to the endpoint, adding a Cookie
 *    Preservative parameter requesting an extension to the lifetime of
 *    the State Cookie. When calculating the time extension, an
 *    implementation SHOULD use the RTT information measured based on the
 *    previous COOKIE ECHO / ERROR exchange, and should add no more
 *    than 1 second beyond the measured RTT, due to long State Cookie
 *    lifetimes making the endpoint more subject to a replay attack.
 *
 * Verification Tag:  Not explicit, but safe to ignore.
 *
 * Inputs
 * (endpoint, asoc, chunk)
 *
 * Outputs
 * (asoc, reply_msg, msg_up, timers, counters)
 *
 * The return value is the disposition of the chunk.
 */
static sctp_disposition_t sctp_sf_do_5_2_6_stale(const struct sctp_endpoint *ep,
                                     const struct sctp_association *asoc,
                                     const sctp_subtype_t type,
                                     void *arg,
                                     sctp_cmd_seq_t *commands)
{
      struct sctp_chunk *chunk = arg;
      time_t stale;
      sctp_cookie_preserve_param_t bht;
      sctp_errhdr_t *err;
      struct sctp_chunk *reply;
      struct sctp_bind_addr *bp;
      int attempts = asoc->init_err_counter + 1;

      if (attempts > asoc->max_init_attempts) {
            sctp_add_cmd_sf(commands, SCTP_CMD_SET_SK_ERR,
                        SCTP_ERROR(ETIMEDOUT));
            sctp_add_cmd_sf(commands, SCTP_CMD_INIT_FAILED,
                        SCTP_U32(SCTP_ERROR_STALE_COOKIE));
            return SCTP_DISPOSITION_DELETE_TCB;
      }

      err = (sctp_errhdr_t *)(chunk->skb->data);

      /* When calculating the time extension, an implementation
       * SHOULD use the RTT information measured based on the
       * previous COOKIE ECHO / ERROR exchange, and should add no
       * more than 1 second beyond the measured RTT, due to long
       * State Cookie lifetimes making the endpoint more subject to
       * a replay attack.
       * Measure of Staleness's unit is usec. (1/1000000 sec)
       * Suggested Cookie Life-span Increment's unit is msec.
       * (1/1000 sec)
       * In general, if you use the suggested cookie life, the value
       * found in the field of measure of staleness should be doubled
       * to give ample time to retransmit the new cookie and thus
       * yield a higher probability of success on the reattempt.
       */
      stale = ntohl(*(suseconds_t *)((u8 *)err + sizeof(sctp_errhdr_t)));
      stale = (stale * 2) / 1000;

      bht.param_hdr.type = SCTP_PARAM_COOKIE_PRESERVATIVE;
      bht.param_hdr.length = htons(sizeof(bht));
      bht.lifespan_increment = htonl(stale);

      /* Build that new INIT chunk.  */
      bp = (struct sctp_bind_addr *) &asoc->base.bind_addr;
      reply = sctp_make_init(asoc, bp, GFP_ATOMIC, sizeof(bht));
      if (!reply)
            goto nomem;

      sctp_addto_chunk(reply, sizeof(bht), &bht);

      /* Clear peer's init_tag cached in assoc as we are sending a new INIT */
      sctp_add_cmd_sf(commands, SCTP_CMD_CLEAR_INIT_TAG, SCTP_NULL());

      /* Stop pending T3-rtx and heartbeat timers */
      sctp_add_cmd_sf(commands, SCTP_CMD_T3_RTX_TIMERS_STOP, SCTP_NULL());
      sctp_add_cmd_sf(commands, SCTP_CMD_HB_TIMERS_STOP, SCTP_NULL());

      /* Delete non-primary peer ip addresses since we are transitioning
       * back to the COOKIE-WAIT state
       */
      sctp_add_cmd_sf(commands, SCTP_CMD_DEL_NON_PRIMARY, SCTP_NULL());

      /* If we've sent any data bundled with COOKIE-ECHO we will need to 
       * resend 
       */
      sctp_add_cmd_sf(commands, SCTP_CMD_RETRAN, 
                  SCTP_TRANSPORT(asoc->peer.primary_path));

      /* Cast away the const modifier, as we want to just
       * rerun it through as a sideffect.
       */
      sctp_add_cmd_sf(commands, SCTP_CMD_INIT_COUNTER_INC, SCTP_NULL());

      sctp_add_cmd_sf(commands, SCTP_CMD_TIMER_STOP,
                  SCTP_TO(SCTP_EVENT_TIMEOUT_T1_COOKIE));
      sctp_add_cmd_sf(commands, SCTP_CMD_NEW_STATE,
                  SCTP_STATE(SCTP_STATE_COOKIE_WAIT));
      sctp_add_cmd_sf(commands, SCTP_CMD_TIMER_START,
                  SCTP_TO(SCTP_EVENT_TIMEOUT_T1_INIT));

      sctp_add_cmd_sf(commands, SCTP_CMD_REPLY, SCTP_CHUNK(reply));

      return SCTP_DISPOSITION_CONSUME;

nomem:
      return SCTP_DISPOSITION_NOMEM;
}

/*
 * Process an ABORT.
 *
 * Section: 9.1
 * After checking the Verification Tag, the receiving endpoint shall
 * remove the association from its record, and shall report the
 * termination to its upper layer.
 *
 * Verification Tag: 8.5.1 Exceptions in Verification Tag Rules
 * B) Rules for packet carrying ABORT:
 *
 *  - The endpoint shall always fill in the Verification Tag field of the
 *    outbound packet with the destination endpoint's tag value if it
 *    is known.
 *
 *  - If the ABORT is sent in response to an OOTB packet, the endpoint
 *    MUST follow the procedure described in Section 8.4.
 *
 *  - The receiver MUST accept the packet if the Verification Tag
 *    matches either its own tag, OR the tag of its peer. Otherwise, the
 *    receiver MUST silently discard the packet and take no further
 *    action.
 *
 * Inputs
 * (endpoint, asoc, chunk)
 *
 * Outputs
 * (asoc, reply_msg, msg_up, timers, counters)
 *
 * The return value is the disposition of the chunk.
 */
sctp_disposition_t sctp_sf_do_9_1_abort(const struct sctp_endpoint *ep,
                              const struct sctp_association *asoc,
                              const sctp_subtype_t type,
                              void *arg,
                              sctp_cmd_seq_t *commands)
{
      struct sctp_chunk *chunk = arg;
      unsigned len;
      __u16 error = SCTP_ERROR_NO_ERROR;

      if (!sctp_vtag_verify_either(chunk, asoc))
            return sctp_sf_pdiscard(ep, asoc, type, arg, commands);

      /* Make sure that the ABORT chunk has a valid length.
       * Since this is an ABORT chunk, we have to discard it
       * because of the following text:
       * RFC 2960, Section 3.3.7
       *    If an endpoint receives an ABORT with a format error or for an
       *    association that doesn't exist, it MUST silently discard it.
       * Becasue the length is "invalid", we can't really discard just
       * as we do not know its true length.  So, to be safe, discard the
       * packet.
       */
      if (!sctp_chunk_length_valid(chunk, sizeof(sctp_abort_chunk_t)))
            return sctp_sf_pdiscard(ep, asoc, type, arg, commands);

      /* See if we have an error cause code in the chunk.  */
      len = ntohs(chunk->chunk_hdr->length);
      if (len >= sizeof(struct sctp_chunkhdr) + sizeof(struct sctp_errhdr))
            error = ((sctp_errhdr_t *)chunk->skb->data)->cause;

      sctp_add_cmd_sf(commands, SCTP_CMD_SET_SK_ERR, SCTP_ERROR(ECONNRESET));
      /* ASSOC_FAILED will DELETE_TCB. */
      sctp_add_cmd_sf(commands, SCTP_CMD_ASSOC_FAILED, SCTP_U32(error));
      SCTP_INC_STATS(SCTP_MIB_ABORTEDS);
      SCTP_DEC_STATS(SCTP_MIB_CURRESTAB);

      return SCTP_DISPOSITION_ABORT;
}

/*
 * Process an ABORT.  (COOKIE-WAIT state)
 *
 * See sctp_sf_do_9_1_abort() above.
 */
sctp_disposition_t sctp_sf_cookie_wait_abort(const struct sctp_endpoint *ep,
                             const struct sctp_association *asoc,
                             const sctp_subtype_t type,
                             void *arg,
                             sctp_cmd_seq_t *commands)
{
      struct sctp_chunk *chunk = arg;
      unsigned len;
      __u16 error = SCTP_ERROR_NO_ERROR;

      if (!sctp_vtag_verify_either(chunk, asoc))
            return sctp_sf_pdiscard(ep, asoc, type, arg, commands);

      /* Make sure that the ABORT chunk has a valid length.
       * Since this is an ABORT chunk, we have to discard it
       * because of the following text:
       * RFC 2960, Section 3.3.7
       *    If an endpoint receives an ABORT with a format error or for an
       *    association that doesn't exist, it MUST silently discard it.
       * Becasue the length is "invalid", we can't really discard just
       * as we do not know its true length.  So, to be safe, discard the
       * packet.
       */
      if (!sctp_chunk_length_valid(chunk, sizeof(sctp_abort_chunk_t)))
            return sctp_sf_pdiscard(ep, asoc, type, arg, commands);

      /* See if we have an error cause code in the chunk.  */
      len = ntohs(chunk->chunk_hdr->length);
      if (len >= sizeof(struct sctp_chunkhdr) + sizeof(struct sctp_errhdr))
            error = ((sctp_errhdr_t *)chunk->skb->data)->cause;

      return sctp_stop_t1_and_abort(commands, error, ECONNREFUSED, asoc,
                              chunk->transport);
}

/*
 * Process an incoming ICMP as an ABORT.  (COOKIE-WAIT state)
 */
sctp_disposition_t sctp_sf_cookie_wait_icmp_abort(const struct sctp_endpoint *ep,
                              const struct sctp_association *asoc,
                              const sctp_subtype_t type,
                              void *arg,
                              sctp_cmd_seq_t *commands)
{
      return sctp_stop_t1_and_abort(commands, SCTP_ERROR_NO_ERROR,
                              ENOPROTOOPT, asoc,
                              (struct sctp_transport *)arg);
}

/*
 * Process an ABORT.  (COOKIE-ECHOED state)
 */
sctp_disposition_t sctp_sf_cookie_echoed_abort(const struct sctp_endpoint *ep,
                                     const struct sctp_association *asoc,
                                     const sctp_subtype_t type,
                                     void *arg,
                                     sctp_cmd_seq_t *commands)
{
      /* There is a single T1 timer, so we should be able to use
       * common function with the COOKIE-WAIT state.
       */
      return sctp_sf_cookie_wait_abort(ep, asoc, type, arg, commands);
}

/*
 * Stop T1 timer and abort association with "INIT failed".
 *
 * This is common code called by several sctp_sf_*_abort() functions above.
 */
static sctp_disposition_t sctp_stop_t1_and_abort(sctp_cmd_seq_t *commands,
                                 __u16 error, int sk_err,
                                 const struct sctp_association *asoc,
                                 struct sctp_transport *transport)
{
      SCTP_DEBUG_PRINTK("ABORT received (INIT).\n");
      sctp_add_cmd_sf(commands, SCTP_CMD_NEW_STATE,
                  SCTP_STATE(SCTP_STATE_CLOSED));
      SCTP_INC_STATS(SCTP_MIB_ABORTEDS);
      sctp_add_cmd_sf(commands, SCTP_CMD_TIMER_STOP,
                  SCTP_TO(SCTP_EVENT_TIMEOUT_T1_INIT));
      sctp_add_cmd_sf(commands, SCTP_CMD_SET_SK_ERR, SCTP_ERROR(sk_err));
      /* CMD_INIT_FAILED will DELETE_TCB. */
      sctp_add_cmd_sf(commands, SCTP_CMD_INIT_FAILED,
                  SCTP_U32(error));
      return SCTP_DISPOSITION_ABORT;
}

/*
 * sctp_sf_do_9_2_shut
 *
 * Section: 9.2
 * Upon the reception of the SHUTDOWN, the peer endpoint shall
 *  - enter the SHUTDOWN-RECEIVED state,
 *
 *  - stop accepting new data from its SCTP user
 *
 *  - verify, by checking the Cumulative TSN Ack field of the chunk,
 *    that all its outstanding DATA chunks have been received by the
 *    SHUTDOWN sender.
 *
 * Once an endpoint as reached the SHUTDOWN-RECEIVED state it MUST NOT
 * send a SHUTDOWN in response to a ULP request. And should discard
 * subsequent SHUTDOWN chunks.
 *
 * If there are still outstanding DATA chunks left, the SHUTDOWN
 * receiver shall continue to follow normal data transmission
 * procedures defined in Section 6 until all outstanding DATA chunks
 * are acknowledged; however, the SHUTDOWN receiver MUST NOT accept
 * new data from its SCTP user.
 *
 * Verification Tag:  8.5 Verification Tag [Normal verification]
 *
 * Inputs
 * (endpoint, asoc, chunk)
 *
 * Outputs
 * (asoc, reply_msg, msg_up, timers, counters)
 *
 * The return value is the disposition of the chunk.
 */
sctp_disposition_t sctp_sf_do_9_2_shutdown(const struct sctp_endpoint *ep,
                                 const struct sctp_association *asoc,
                                 const sctp_subtype_t type,
                                 void *arg,
                                 sctp_cmd_seq_t *commands)
{
      struct sctp_chunk *chunk = arg;
      sctp_shutdownhdr_t *sdh;
      sctp_disposition_t disposition;
      struct sctp_ulpevent *ev;

      if (!sctp_vtag_verify(chunk, asoc))
            return sctp_sf_pdiscard(ep, asoc, type, arg, commands);

      /* Make sure that the SHUTDOWN chunk has a valid length. */
      if (!sctp_chunk_length_valid(chunk,
                              sizeof(struct sctp_shutdown_chunk_t)))
            return sctp_sf_violation_chunklen(ep, asoc, type, arg,
                                      commands);

      /* Convert the elaborate header.  */
      sdh = (sctp_shutdownhdr_t *)chunk->skb->data;
      skb_pull(chunk->skb, sizeof(sctp_shutdownhdr_t));
      chunk->subh.shutdown_hdr = sdh;

      /* API 5.3.1.5 SCTP_SHUTDOWN_EVENT
       * When a peer sends a SHUTDOWN, SCTP delivers this notification to
       * inform the application that it should cease sending data.
       */
      ev = sctp_ulpevent_make_shutdown_event(asoc, 0, GFP_ATOMIC);
      if (!ev) {
            disposition = SCTP_DISPOSITION_NOMEM;
            goto out;   
      }
      sctp_add_cmd_sf(commands, SCTP_CMD_EVENT_ULP, SCTP_ULPEVENT(ev));

      /* Upon the reception of the SHUTDOWN, the peer endpoint shall
       *  - enter the SHUTDOWN-RECEIVED state,
       *  - stop accepting new data from its SCTP user
       *
       * [This is implicit in the new state.]
       */
      sctp_add_cmd_sf(commands, SCTP_CMD_NEW_STATE,
                  SCTP_STATE(SCTP_STATE_SHUTDOWN_RECEIVED));
      disposition = SCTP_DISPOSITION_CONSUME;

      if (sctp_outq_is_empty(&asoc->outqueue)) {
            disposition = sctp_sf_do_9_2_shutdown_ack(ep, asoc, type,
                                            arg, commands);
      }

      if (SCTP_DISPOSITION_NOMEM == disposition)
            goto out;

      /*  - verify, by checking the Cumulative TSN Ack field of the
       *    chunk, that all its outstanding DATA chunks have been
       *    received by the SHUTDOWN sender.
       */
      sctp_add_cmd_sf(commands, SCTP_CMD_PROCESS_CTSN,
                  SCTP_U32(chunk->subh.shutdown_hdr->cum_tsn_ack));

out:
      return disposition;
}

/* RFC 2960 9.2
 * If an endpoint is in SHUTDOWN-ACK-SENT state and receives an INIT chunk
 * (e.g., if the SHUTDOWN COMPLETE was lost) with source and destination
 * transport addresses (either in the IP addresses or in the INIT chunk)
 * that belong to this association, it should discard the INIT chunk and
 * retransmit the SHUTDOWN ACK chunk.
 */
sctp_disposition_t sctp_sf_do_9_2_reshutack(const struct sctp_endpoint *ep,
                            const struct sctp_association *asoc,
                            const sctp_subtype_t type,
                            void *arg,
                            sctp_cmd_seq_t *commands)
{
      struct sctp_chunk *chunk = (struct sctp_chunk *) arg;
      struct sctp_chunk *reply;

      /* Since we are not going to really process this INIT, there
       * is no point in verifying chunk boundries.  Just generate
       * the SHUTDOWN ACK.
       */
      reply = sctp_make_shutdown_ack(asoc, chunk);
      if (NULL == reply)
            goto nomem;

      /* Set the transport for the SHUTDOWN ACK chunk and the timeout for
       * the T2-SHUTDOWN timer.
       */
      sctp_add_cmd_sf(commands, SCTP_CMD_SETUP_T2, SCTP_CHUNK(reply));

      /* and restart the T2-shutdown timer. */
      sctp_add_cmd_sf(commands, SCTP_CMD_TIMER_RESTART,
                  SCTP_TO(SCTP_EVENT_TIMEOUT_T2_SHUTDOWN));

      sctp_add_cmd_sf(commands, SCTP_CMD_REPLY, SCTP_CHUNK(reply));

      return SCTP_DISPOSITION_CONSUME;
nomem:
      return SCTP_DISPOSITION_NOMEM;
}

/*
 * sctp_sf_do_ecn_cwr
 *
 * Section:  Appendix A: Explicit Congestion Notification
 *
 * CWR:
 *
 * RFC 2481 details a specific bit for a sender to send in the header of
 * its next outbound TCP segment to indicate to its peer that it has
 * reduced its congestion window.  This is termed the CWR bit.  For
 * SCTP the same indication is made by including the CWR chunk.
 * This chunk contains one data element, i.e. the TSN number that
 * was sent in the ECNE chunk.  This element represents the lowest
 * TSN number in the datagram that was originally marked with the
 * CE bit.
 *
 * Verification Tag: 8.5 Verification Tag [Normal verification]
 * Inputs
 * (endpoint, asoc, chunk)
 *
 * Outputs
 * (asoc, reply_msg, msg_up, timers, counters)
 *
 * The return value is the disposition of the chunk.
 */
sctp_disposition_t sctp_sf_do_ecn_cwr(const struct sctp_endpoint *ep,
                              const struct sctp_association *asoc,
                              const sctp_subtype_t type,
                              void *arg,
                              sctp_cmd_seq_t *commands)
{
      sctp_cwrhdr_t *cwr;
      struct sctp_chunk *chunk = arg;

      if (!sctp_vtag_verify(chunk, asoc))
            return sctp_sf_pdiscard(ep, asoc, type, arg, commands);

      if (!sctp_chunk_length_valid(chunk, sizeof(sctp_ecne_chunk_t)))
            return sctp_sf_violation_chunklen(ep, asoc, type, arg,
                                      commands);
            
      cwr = (sctp_cwrhdr_t *) chunk->skb->data;
      skb_pull(chunk->skb, sizeof(sctp_cwrhdr_t));

      cwr->lowest_tsn = ntohl(cwr->lowest_tsn);

      /* Does this CWR ack the last sent congestion notification? */
      if (TSN_lte(asoc->last_ecne_tsn, cwr->lowest_tsn)) {
            /* Stop sending ECNE. */
            sctp_add_cmd_sf(commands,
                        SCTP_CMD_ECN_CWR,
                        SCTP_U32(cwr->lowest_tsn));
      }
      return SCTP_DISPOSITION_CONSUME;
}

/*
 * sctp_sf_do_ecne
 *
 * Section:  Appendix A: Explicit Congestion Notification
 *
 * ECN-Echo
 *
 * RFC 2481 details a specific bit for a receiver to send back in its
 * TCP acknowledgements to notify the sender of the Congestion
 * Experienced (CE) bit having arrived from the network.  For SCTP this
 * same indication is made by including the ECNE chunk.  This chunk
 * contains one data element, i.e. the lowest TSN associated with the IP
 * datagram marked with the CE bit.....
 *
 * Verification Tag: 8.5 Verification Tag [Normal verification]
 * Inputs
 * (endpoint, asoc, chunk)
 *
 * Outputs
 * (asoc, reply_msg, msg_up, timers, counters)
 *
 * The return value is the disposition of the chunk.
 */
sctp_disposition_t sctp_sf_do_ecne(const struct sctp_endpoint *ep,
                           const struct sctp_association *asoc,
                           const sctp_subtype_t type,
                           void *arg,
                           sctp_cmd_seq_t *commands)
{
      sctp_ecnehdr_t *ecne;
      struct sctp_chunk *chunk = arg;

      if (!sctp_vtag_verify(chunk, asoc))
            return sctp_sf_pdiscard(ep, asoc, type, arg, commands);

      if (!sctp_chunk_length_valid(chunk, sizeof(sctp_ecne_chunk_t)))
            return sctp_sf_violation_chunklen(ep, asoc, type, arg,
                                      commands);

      ecne = (sctp_ecnehdr_t *) chunk->skb->data;
      skb_pull(chunk->skb, sizeof(sctp_ecnehdr_t));

      /* If this is a newer ECNE than the last CWR packet we sent out */
      sctp_add_cmd_sf(commands, SCTP_CMD_ECN_ECNE,
                  SCTP_U32(ntohl(ecne->lowest_tsn)));

      return SCTP_DISPOSITION_CONSUME;
}

/*
 * Section: 6.2  Acknowledgement on Reception of DATA Chunks
 *
 * The SCTP endpoint MUST always acknowledge the reception of each valid
 * DATA chunk.
 *
 * The guidelines on delayed acknowledgement algorithm specified in
 * Section 4.2 of [RFC2581] SHOULD be followed. Specifically, an
 * acknowledgement SHOULD be generated for at least every second packet
 * (not every second DATA chunk) received, and SHOULD be generated within
 * 200 ms of the arrival of any unacknowledged DATA chunk. In some
 * situations it may be beneficial for an SCTP transmitter to be more
 * conservative than the algorithms detailed in this document allow.
 * However, an SCTP transmitter MUST NOT be more aggressive than the
 * following algorithms allow.
 *
 * A SCTP receiver MUST NOT generate more than one SACK for every
 * incoming packet, other than to update the offered window as the
 * receiving application consumes new data.
 *
 * Verification Tag:  8.5 Verification Tag [Normal verification]
 *
 * Inputs
 * (endpoint, asoc, chunk)
 *
 * Outputs
 * (asoc, reply_msg, msg_up, timers, counters)
 *
 * The return value is the disposition of the chunk.
 */
sctp_disposition_t sctp_sf_eat_data_6_2(const struct sctp_endpoint *ep,
                              const struct sctp_association *asoc,
                              const sctp_subtype_t type,
                              void *arg,
                              sctp_cmd_seq_t *commands)
{
      struct sctp_chunk *chunk = arg;
      int error;

      if (!sctp_vtag_verify(chunk, asoc)) {
            sctp_add_cmd_sf(commands, SCTP_CMD_REPORT_BAD_TAG,
                        SCTP_NULL());
            return sctp_sf_pdiscard(ep, asoc, type, arg, commands);
        }

      if (!sctp_chunk_length_valid(chunk, sizeof(sctp_data_chunk_t)))
            return sctp_sf_violation_chunklen(ep, asoc, type, arg,
                                      commands);

      error = sctp_eat_data(asoc, chunk, commands );
      switch (error) {
      case SCTP_IERROR_NO_ERROR:
            break;
      case SCTP_IERROR_HIGH_TSN:
      case SCTP_IERROR_BAD_STREAM:
            goto discard_noforce;
      case SCTP_IERROR_DUP_TSN:
      case SCTP_IERROR_IGNORE_TSN:
            goto discard_force;
      case SCTP_IERROR_NO_DATA:
            goto consume;
      default:
            BUG();
      }

      if (asoc->autoclose) {
            sctp_add_cmd_sf(commands, SCTP_CMD_TIMER_RESTART,
                        SCTP_TO(SCTP_EVENT_TIMEOUT_AUTOCLOSE));
      }

      /* If this is the last chunk in a packet, we need to count it
       * toward sack generation.  Note that we need to SACK every
       * OTHER packet containing data chunks, EVEN IF WE DISCARD
       * THEM.  We elect to NOT generate SACK's if the chunk fails
       * the verification tag test.
       *
       * RFC 2960 6.2 Acknowledgement on Reception of DATA Chunks
       *
       * The SCTP endpoint MUST always acknowledge the reception of
       * each valid DATA chunk.
       *
       * The guidelines on delayed acknowledgement algorithm
       * specified in  Section 4.2 of [RFC2581] SHOULD be followed.
       * Specifically, an acknowledgement SHOULD be generated for at
       * least every second packet (not every second DATA chunk)
       * received, and SHOULD be generated within 200 ms of the
       * arrival of any unacknowledged DATA chunk.  In some
       * situations it may be beneficial for an SCTP transmitter to
       * be more conservative than the algorithms detailed in this
       * document allow. However, an SCTP transmitter MUST NOT be
       * more aggressive than the following algorithms allow.
       */
      if (chunk->end_of_packet)
            sctp_add_cmd_sf(commands, SCTP_CMD_GEN_SACK, SCTP_NOFORCE());

      return SCTP_DISPOSITION_CONSUME;

discard_force:
      /* RFC 2960 6.2 Acknowledgement on Reception of DATA Chunks
       *
       * When a packet arrives with duplicate DATA chunk(s) and with
       * no new DATA chunk(s), the endpoint MUST immediately send a
       * SACK with no delay.  If a packet arrives with duplicate
       * DATA chunk(s) bundled with new DATA chunks, the endpoint
       * MAY immediately send a SACK.  Normally receipt of duplicate
       * DATA chunks will occur when the original SACK chunk was lost
       * and the peer's RTO has expired.  The duplicate TSN number(s)
       * SHOULD be reported in the SACK as duplicate.
       */
      /* In our case, we split the MAY SACK advice up whether or not
       * the last chunk is a duplicate.'
       */
      if (chunk->end_of_packet)
            sctp_add_cmd_sf(commands, SCTP_CMD_GEN_SACK, SCTP_FORCE());
      return SCTP_DISPOSITION_DISCARD;

discard_noforce:
      if (chunk->end_of_packet)
            sctp_add_cmd_sf(commands, SCTP_CMD_GEN_SACK, SCTP_NOFORCE());

      return SCTP_DISPOSITION_DISCARD;
consume:
      return SCTP_DISPOSITION_CONSUME;
      
}

/*
 * sctp_sf_eat_data_fast_4_4
 *
 * Section: 4 (4)
 * (4) In SHUTDOWN-SENT state the endpoint MUST acknowledge any received
 *    DATA chunks without delay.
 *
 * Verification Tag:  8.5 Verification Tag [Normal verification]
 * Inputs
 * (endpoint, asoc, chunk)
 *
 * Outputs
 * (asoc, reply_msg, msg_up, timers, counters)
 *
 * The return value is the disposition of the chunk.
 */
sctp_disposition_t sctp_sf_eat_data_fast_4_4(const struct sctp_endpoint *ep,
                             const struct sctp_association *asoc,
                             const sctp_subtype_t type,
                             void *arg,
                             sctp_cmd_seq_t *commands)
{
      struct sctp_chunk *chunk = arg;
      int error;

      if (!sctp_vtag_verify(chunk, asoc)) {
            sctp_add_cmd_sf(commands, SCTP_CMD_REPORT_BAD_TAG,
                        SCTP_NULL());
            return sctp_sf_pdiscard(ep, asoc, type, arg, commands);
      }

      if (!sctp_chunk_length_valid(chunk, sizeof(sctp_data_chunk_t)))
            return sctp_sf_violation_chunklen(ep, asoc, type, arg,
                                      commands);

      error = sctp_eat_data(asoc, chunk, commands );
      switch (error) {
      case SCTP_IERROR_NO_ERROR:
      case SCTP_IERROR_HIGH_TSN:
      case SCTP_IERROR_DUP_TSN:
      case SCTP_IERROR_IGNORE_TSN:
      case SCTP_IERROR_BAD_STREAM:
            break;
      case SCTP_IERROR_NO_DATA:
            goto consume;
      default:
            BUG();
      }

      /* Go a head and force a SACK, since we are shutting down. */

      /* Implementor's Guide.
       *
       * While in SHUTDOWN-SENT state, the SHUTDOWN sender MUST immediately
       * respond to each received packet containing one or more DATA chunk(s)
       * with a SACK, a SHUTDOWN chunk, and restart the T2-shutdown timer
       */
      if (chunk->end_of_packet) {
            /* We must delay the chunk creation since the cumulative
             * TSN has not been updated yet.
             */
            sctp_add_cmd_sf(commands, SCTP_CMD_GEN_SHUTDOWN, SCTP_NULL());
            sctp_add_cmd_sf(commands, SCTP_CMD_GEN_SACK, SCTP_FORCE());
            sctp_add_cmd_sf(commands, SCTP_CMD_TIMER_RESTART,
                        SCTP_TO(SCTP_EVENT_TIMEOUT_T2_SHUTDOWN));
      }

consume:
      return SCTP_DISPOSITION_CONSUME;
}

/*
 * Section: 6.2  Processing a Received SACK
 * D) Any time a SACK arrives, the endpoint performs the following:
 *
 *     i) If Cumulative TSN Ack is less than the Cumulative TSN Ack Point,
 *     then drop the SACK.   Since Cumulative TSN Ack is monotonically
 *     increasing, a SACK whose Cumulative TSN Ack is less than the
 *     Cumulative TSN Ack Point indicates an out-of-order SACK.
 *
 *     ii) Set rwnd equal to the newly received a_rwnd minus the number
 *     of bytes still outstanding after processing the Cumulative TSN Ack
 *     and the Gap Ack Blocks.
 *
 *     iii) If the SACK is missing a TSN that was previously
 *     acknowledged via a Gap Ack Block (e.g., the data receiver
 *     reneged on the data), then mark the corresponding DATA chunk
 *     as available for retransmit:  Mark it as missing for fast
 *     retransmit as described in Section 7.2.4 and if no retransmit
 *     timer is running for the destination address to which the DATA
 *     chunk was originally transmitted, then T3-rtx is started for
 *     that destination address.
 *
 * Verification Tag:  8.5 Verification Tag [Normal verification]
 *
 * Inputs
 * (endpoint, asoc, chunk)
 *
 * Outputs
 * (asoc, reply_msg, msg_up, timers, counters)
 *
 * The return value is the disposition of the chunk.
 */
sctp_disposition_t sctp_sf_eat_sack_6_2(const struct sctp_endpoint *ep,
                              const struct sctp_association *asoc,
                              const sctp_subtype_t type,
                              void *arg,
                              sctp_cmd_seq_t *commands)
{
      struct sctp_chunk *chunk = arg;
      sctp_sackhdr_t *sackh;
      __u32 ctsn;

      if (!sctp_vtag_verify(chunk, asoc))
            return sctp_sf_pdiscard(ep, asoc, type, arg, commands);

      /* Make sure that the SACK chunk has a valid length. */
      if (!sctp_chunk_length_valid(chunk, sizeof(sctp_sack_chunk_t)))
            return sctp_sf_violation_chunklen(ep, asoc, type, arg,
                                      commands);

      /* Pull the SACK chunk from the data buffer */
      sackh = sctp_sm_pull_sack(chunk);
      /* Was this a bogus SACK? */
      if (!sackh)
            return sctp_sf_pdiscard(ep, asoc, type, arg, commands);
      chunk->subh.sack_hdr = sackh;
      ctsn = ntohl(sackh->cum_tsn_ack);

      /* i) If Cumulative TSN Ack is less than the Cumulative TSN
       *     Ack Point, then drop the SACK.  Since Cumulative TSN
       *     Ack is monotonically increasing, a SACK whose
       *     Cumulative TSN Ack is less than the Cumulative TSN Ack
       *     Point indicates an out-of-order SACK.
       */
      if (TSN_lt(ctsn, asoc->ctsn_ack_point)) {
            SCTP_DEBUG_PRINTK("ctsn %x\n", ctsn);
            SCTP_DEBUG_PRINTK("ctsn_ack_point %x\n", asoc->ctsn_ack_point);
            return SCTP_DISPOSITION_DISCARD;
      }

      /* Return this SACK for further processing.  */
      sctp_add_cmd_sf(commands, SCTP_CMD_PROCESS_SACK, SCTP_SACKH(sackh));

      /* Note: We do the rest of the work on the PROCESS_SACK
       * sideeffect.
       */
      return SCTP_DISPOSITION_CONSUME;
}

/*
 * Generate an ABORT in response to a packet.
 *
 * Section: 8.4 Handle "Out of the blue" Packets, sctpimpguide 2.41
 *
 * 8) The receiver should respond to the sender of the OOTB packet with
 *    an ABORT.  When sending the ABORT, the receiver of the OOTB packet
 *    MUST fill in the Verification Tag field of the outbound packet
 *    with the value found in the Verification Tag field of the OOTB
 *    packet and set the T-bit in the Chunk Flags to indicate that the
 *    Verification Tag is reflected.  After sending this ABORT, the
 *    receiver of the OOTB packet shall discard the OOTB packet and take
 *    no further action.
 *
 * Verification Tag:
 *
 * The return value is the disposition of the chunk.
*/
sctp_disposition_t sctp_sf_tabort_8_4_8(const struct sctp_endpoint *ep,
                              const struct sctp_association *asoc,
                              const sctp_subtype_t type,
                              void *arg,
                              sctp_cmd_seq_t *commands)
{
      struct sctp_packet *packet = NULL;
      struct sctp_chunk *chunk = arg;
      struct sctp_chunk *abort;

      packet = sctp_ootb_pkt_new(asoc, chunk);

      if (packet) {
            /* Make an ABORT. The T bit will be set if the asoc
             * is NULL.
             */
            abort = sctp_make_abort(asoc, chunk, 0);
            if (!abort) {
                  sctp_ootb_pkt_free(packet);
                  return SCTP_DISPOSITION_NOMEM;
            }

            /* Reflect vtag if T-Bit is set */
            if (sctp_test_T_bit(abort))
                  packet->vtag = ntohl(chunk->sctp_hdr->vtag);

            /* Set the skb to the belonging sock for accounting.  */
            abort->skb->sk = ep->base.sk;

            sctp_packet_append_chunk(packet, abort);

            sctp_add_cmd_sf(commands, SCTP_CMD_SEND_PKT,
                        SCTP_PACKET(packet));

            SCTP_INC_STATS(SCTP_MIB_OUTCTRLCHUNKS);

            return SCTP_DISPOSITION_CONSUME;
      }

      return SCTP_DISPOSITION_NOMEM;
}

/*
 * Received an ERROR chunk from peer.  Generate SCTP_REMOTE_ERROR
 * event as ULP notification for each cause included in the chunk.
 *
 * API 5.3.1.3 - SCTP_REMOTE_ERROR
 *
 * The return value is the disposition of the chunk.
*/
sctp_disposition_t sctp_sf_operr_notify(const struct sctp_endpoint *ep,
                              const struct sctp_association *asoc,
                              const sctp_subtype_t type,
                              void *arg,
                              sctp_cmd_seq_t *commands)
{
      struct sctp_chunk *chunk = arg;
      struct sctp_ulpevent *ev;

      if (!sctp_vtag_verify(chunk, asoc))
            return sctp_sf_pdiscard(ep, asoc, type, arg, commands);

      /* Make sure that the ERROR chunk has a valid length. */
      if (!sctp_chunk_length_valid(chunk, sizeof(sctp_operr_chunk_t)))
            return sctp_sf_violation_chunklen(ep, asoc, type, arg,
                                      commands);

      while (chunk->chunk_end > chunk->skb->data) {
            ev = sctp_ulpevent_make_remote_error(asoc, chunk, 0,
                                         GFP_ATOMIC);
            if (!ev)
                  goto nomem;

            if (!sctp_add_cmd(commands, SCTP_CMD_EVENT_ULP,
                          SCTP_ULPEVENT(ev))) {
                  sctp_ulpevent_free(ev);
                  goto nomem;
            }

            sctp_add_cmd_sf(commands, SCTP_CMD_PROCESS_OPERR,
                        SCTP_CHUNK(chunk));     
      }
      return SCTP_DISPOSITION_CONSUME;

nomem:
      return SCTP_DISPOSITION_NOMEM;
}

/*
 * Process an inbound SHUTDOWN ACK.
 *
 * From Section 9.2:
 * Upon the receipt of the SHUTDOWN ACK, the SHUTDOWN sender shall
 * stop the T2-shutdown timer, send a SHUTDOWN COMPLETE chunk to its
 * peer, and remove all record of the association.
 *
 * The return value is the disposition.
 */
sctp_disposition_t sctp_sf_do_9_2_final(const struct sctp_endpoint *ep,
                              const struct sctp_association *asoc,
                              const sctp_subtype_t type,
                              void *arg,
                              sctp_cmd_seq_t *commands)
{
      struct sctp_chunk *chunk = arg;
      struct sctp_chunk *reply;
      struct sctp_ulpevent *ev;

      if (!sctp_vtag_verify(chunk, asoc))
            return sctp_sf_pdiscard(ep, asoc, type, arg, commands);

      /* Make sure that the SHUTDOWN_ACK chunk has a valid length. */
      if (!sctp_chunk_length_valid(chunk, sizeof(sctp_chunkhdr_t)))
            return sctp_sf_violation_chunklen(ep, asoc, type, arg,
                                      commands);

      /* 10.2 H) SHUTDOWN COMPLETE notification
       *
       * When SCTP completes the shutdown procedures (section 9.2) this
       * notification is passed to the upper layer.
       */
      ev = sctp_ulpevent_make_assoc_change(asoc, 0, SCTP_SHUTDOWN_COMP,
                                   0, 0, 0, GFP_ATOMIC);
      if (!ev)
            goto nomem;

      sctp_add_cmd_sf(commands, SCTP_CMD_EVENT_ULP, SCTP_ULPEVENT(ev));

      /* Upon the receipt of the SHUTDOWN ACK, the SHUTDOWN sender shall
       * stop the T2-shutdown timer,
       */
      sctp_add_cmd_sf(commands, SCTP_CMD_TIMER_STOP,
                  SCTP_TO(SCTP_EVENT_TIMEOUT_T2_SHUTDOWN));

      sctp_add_cmd_sf(commands, SCTP_CMD_TIMER_STOP,
                  SCTP_TO(SCTP_EVENT_TIMEOUT_T5_SHUTDOWN_GUARD));

      /* ...send a SHUTDOWN COMPLETE chunk to its peer, */
      reply = sctp_make_shutdown_complete(asoc, chunk);
      if (!reply)
            goto nomem;

      sctp_add_cmd_sf(commands, SCTP_CMD_NEW_STATE,
                  SCTP_STATE(SCTP_STATE_CLOSED));
      SCTP_INC_STATS(SCTP_MIB_SHUTDOWNS);
      SCTP_DEC_STATS(SCTP_MIB_CURRESTAB);
      sctp_add_cmd_sf(commands, SCTP_CMD_REPLY, SCTP_CHUNK(reply));

      /* ...and remove all record of the association. */
      sctp_add_cmd_sf(commands, SCTP_CMD_DELETE_TCB, SCTP_NULL());
      return SCTP_DISPOSITION_DELETE_TCB;

nomem:
      return SCTP_DISPOSITION_NOMEM;
}

/*
 * RFC 2960, 8.4 - Handle "Out of the blue" Packets, sctpimpguide 2.41.
 *
 * 5) If the packet contains a SHUTDOWN ACK chunk, the receiver should
 *    respond to the sender of the OOTB packet with a SHUTDOWN COMPLETE.
 *    When sending the SHUTDOWN COMPLETE, the receiver of the OOTB
 *    packet must fill in the Verification Tag field of the outbound
 *    packet with the Verification Tag received in the SHUTDOWN ACK and
 *    set the T-bit in the Chunk Flags to indicate that the Verification
 *    Tag is reflected.
 *
 * 8) The receiver should respond to the sender of the OOTB packet with
 *    an ABORT.  When sending the ABORT, the receiver of the OOTB packet
 *    MUST fill in the Verification Tag field of the outbound packet
 *    with the value found in the Verification Tag field of the OOTB
 *    packet and set the T-bit in the Chunk Flags to indicate that the
 *    Verification Tag is reflected.  After sending this ABORT, the
 *    receiver of the OOTB packet shall discard the OOTB packet and take
 *    no further action.
 */
sctp_disposition_t sctp_sf_ootb(const struct sctp_endpoint *ep,
                        const struct sctp_association *asoc,
                        const sctp_subtype_t type,
                        void *arg,
                        sctp_cmd_seq_t *commands)
{
      struct sctp_chunk *chunk = arg;
      struct sk_buff *skb = chunk->skb;
      sctp_chunkhdr_t *ch;
      __u8 *ch_end;
      int ootb_shut_ack = 0;

      SCTP_INC_STATS(SCTP_MIB_OUTOFBLUES);

      ch = (sctp_chunkhdr_t *) chunk->chunk_hdr;
      do {
            /* Break out if chunk length is less then minimal. */
            if (ntohs(ch->length) < sizeof(sctp_chunkhdr_t))
                  break;

            ch_end = ((__u8 *)ch) + WORD_ROUND(ntohs(ch->length));
            if (ch_end > skb->tail)
                  break;

            if (SCTP_CID_SHUTDOWN_ACK == ch->type)
                  ootb_shut_ack = 1;

            /* RFC 2960, Section 3.3.7
             *   Moreover, under any circumstances, an endpoint that
             *   receives an ABORT  MUST NOT respond to that ABORT by
             *   sending an ABORT of its own.
             */
            if (SCTP_CID_ABORT == ch->type)
                  return sctp_sf_pdiscard(ep, asoc, type, arg, commands);
                  
            ch = (sctp_chunkhdr_t *) ch_end;
      } while (ch_end < skb->tail);

      if (ootb_shut_ack)
            sctp_sf_shut_8_4_5(ep, asoc, type, arg, commands);
      else
            sctp_sf_tabort_8_4_8(ep, asoc, type, arg, commands);

      return sctp_sf_pdiscard(ep, asoc, type, arg, commands);
}

/*
 * Handle an "Out of the blue" SHUTDOWN ACK.
 *
 * Section: 8.4 5, sctpimpguide 2.41.
 *
 * 5) If the packet contains a SHUTDOWN ACK chunk, the receiver should
 *    respond to the sender of the OOTB packet with a SHUTDOWN COMPLETE.
 *    When sending the SHUTDOWN COMPLETE, the receiver of the OOTB
 *    packet must fill in the Verification Tag field of the outbound
 *    packet with the Verification Tag received in the SHUTDOWN ACK and
 *    set the T-bit in the Chunk Flags to indicate that the Verification
 *    Tag is reflected.
 *
 * Inputs
 * (endpoint, asoc, type, arg, commands)
 *
 * Outputs
 * (sctp_disposition_t)
 *
 * The return value is the disposition of the chunk.
 */
static sctp_disposition_t sctp_sf_shut_8_4_5(const struct sctp_endpoint *ep,
                                   const struct sctp_association *asoc,
                                   const sctp_subtype_t type,
                                   void *arg,
                                   sctp_cmd_seq_t *commands)
{
      struct sctp_packet *packet = NULL;
      struct sctp_chunk *chunk = arg;
      struct sctp_chunk *shut;

      packet = sctp_ootb_pkt_new(asoc, chunk);

      if (packet) {
            /* Make an SHUTDOWN_COMPLETE.
             * The T bit will be set if the asoc is NULL.
             */
            shut = sctp_make_shutdown_complete(asoc, chunk);
            if (!shut) {
                  sctp_ootb_pkt_free(packet);
                  return SCTP_DISPOSITION_NOMEM;
            }

            /* Reflect vtag if T-Bit is set */
            if (sctp_test_T_bit(shut))
                  packet->vtag = ntohl(chunk->sctp_hdr->vtag);

            /* Set the skb to the belonging sock for accounting.  */
            shut->skb->sk = ep->base.sk;

            sctp_packet_append_chunk(packet, shut);

            sctp_add_cmd_sf(commands, SCTP_CMD_SEND_PKT,
                        SCTP_PACKET(packet));

            SCTP_INC_STATS(SCTP_MIB_OUTCTRLCHUNKS);

            /* If the chunk length is invalid, we don't want to process
             * the reset of the packet.
             */
            if (!sctp_chunk_length_valid(chunk, sizeof(sctp_chunkhdr_t)))
                  return sctp_sf_pdiscard(ep, asoc, type, arg, commands);

            return SCTP_DISPOSITION_CONSUME;
      }

      return SCTP_DISPOSITION_NOMEM;
}

/*
 * Handle SHUTDOWN ACK in COOKIE_ECHOED or COOKIE_WAIT state.
 *
 * Verification Tag:  8.5.1 E) Rules for packet carrying a SHUTDOWN ACK
 *   If the receiver is in COOKIE-ECHOED or COOKIE-WAIT state the
 *   procedures in section 8.4 SHOULD be followed, in other words it
 *   should be treated as an Out Of The Blue packet.
 *   [This means that we do NOT check the Verification Tag on these
 *   chunks. --piggy ]
 *
 */
sctp_disposition_t sctp_sf_do_8_5_1_E_sa(const struct sctp_endpoint *ep,
                              const struct sctp_association *asoc,
                              const sctp_subtype_t type,
                              void *arg,
                              sctp_cmd_seq_t *commands)
{
      /* Although we do have an association in this case, it corresponds
       * to a restarted association. So the packet is treated as an OOTB
       * packet and the state function that handles OOTB SHUTDOWN_ACK is
       * called with a NULL association.
       */
      return sctp_sf_shut_8_4_5(ep, NULL, type, arg, commands);
}

/* ADDIP Section 4.2 Upon reception of an ASCONF Chunk.  */
sctp_disposition_t sctp_sf_do_asconf(const struct sctp_endpoint *ep,
                             const struct sctp_association *asoc,
                             const sctp_subtype_t type, void *arg,
                             sctp_cmd_seq_t *commands)
{
      struct sctp_chunk *chunk = arg;
      struct sctp_chunk *asconf_ack = NULL;
      sctp_addiphdr_t         *hdr;
      __u32             serial;

      if (!sctp_vtag_verify(chunk, asoc)) {
            sctp_add_cmd_sf(commands, SCTP_CMD_REPORT_BAD_TAG,
                        SCTP_NULL());
            return sctp_sf_pdiscard(ep, asoc, type, arg, commands);
      }

      /* Make sure that the ASCONF ADDIP chunk has a valid length.  */
      if (!sctp_chunk_length_valid(chunk, sizeof(sctp_addip_chunk_t)))
            return sctp_sf_violation_chunklen(ep, asoc, type, arg,
                                      commands);

      hdr = (sctp_addiphdr_t *)chunk->skb->data;
      serial = ntohl(hdr->serial);

      /* ADDIP 4.2 C1) Compare the value of the serial number to the value
       * the endpoint stored in a new association variable
       * 'Peer-Serial-Number'. 
       */
      if (serial == asoc->peer.addip_serial + 1) {
            /* ADDIP 4.2 C2) If the value found in the serial number is
             * equal to the ('Peer-Serial-Number' + 1), the endpoint MUST
             * do V1-V5.
             */
            asconf_ack = sctp_process_asconf((struct sctp_association *)
                                     asoc, chunk);
            if (!asconf_ack)
                  return SCTP_DISPOSITION_NOMEM;
      } else if (serial == asoc->peer.addip_serial) {
            /* ADDIP 4.2 C3) If the value found in the serial number is
             * equal to the value stored in the 'Peer-Serial-Number'
             * IMPLEMENTATION NOTE: As an optimization a receiver may wish
             * to save the last ASCONF-ACK for some predetermined period of
             * time and instead of re-processing the ASCONF (with the same
             * serial number) it may just re-transmit the ASCONF-ACK.
             */
            if (asoc->addip_last_asconf_ack)
                  asconf_ack = asoc->addip_last_asconf_ack;
            else
                  return SCTP_DISPOSITION_DISCARD;
      } else {
            /* ADDIP 4.2 C4) Otherwise, the ASCONF Chunk is discarded since 
             * it must be either a stale packet or from an attacker.
             */   
            return SCTP_DISPOSITION_DISCARD;
      }

      /* ADDIP 4.2 C5) In both cases C2 and C3 the ASCONF-ACK MUST be sent
       * back to the source address contained in the IP header of the ASCONF
       * being responded to.
       */
      sctp_add_cmd_sf(commands, SCTP_CMD_REPLY, SCTP_CHUNK(asconf_ack));
      
      return SCTP_DISPOSITION_CONSUME;
}

/*
 * ADDIP Section 4.3 General rules for address manipulation
 * When building TLV parameters for the ASCONF Chunk that will add or
 * delete IP addresses the D0 to D13 rules should be applied:
 */
sctp_disposition_t sctp_sf_do_asconf_ack(const struct sctp_endpoint *ep,
                               const struct sctp_association *asoc,
                               const sctp_subtype_t type, void *arg,
                               sctp_cmd_seq_t *commands)
{
      struct sctp_chunk *asconf_ack = arg;
      struct sctp_chunk *last_asconf = asoc->addip_last_asconf;
      struct sctp_chunk *abort;
      sctp_addiphdr_t         *addip_hdr;
      __u32             sent_serial, rcvd_serial;

      if (!sctp_vtag_verify(asconf_ack, asoc)) {
            sctp_add_cmd_sf(commands, SCTP_CMD_REPORT_BAD_TAG,
                        SCTP_NULL());
            return sctp_sf_pdiscard(ep, asoc, type, arg, commands);
      }

      /* Make sure that the ADDIP chunk has a valid length.  */
      if (!sctp_chunk_length_valid(asconf_ack, sizeof(sctp_addip_chunk_t)))
            return sctp_sf_violation_chunklen(ep, asoc, type, arg,
                                      commands);

      addip_hdr = (sctp_addiphdr_t *)asconf_ack->skb->data;
      rcvd_serial = ntohl(addip_hdr->serial);

      if (last_asconf) {
            addip_hdr = (sctp_addiphdr_t *)last_asconf->subh.addip_hdr;
            sent_serial = ntohl(addip_hdr->serial);
      } else {
            sent_serial = asoc->addip_serial - 1;
      }

      /* D0) If an endpoint receives an ASCONF-ACK that is greater than or
       * equal to the next serial number to be used but no ASCONF chunk is
       * outstanding the endpoint MUST ABORT the association. Note that a
       * sequence number is greater than if it is no more than 2^^31-1
       * larger than the current sequence number (using serial arithmetic).
       */
      if (ADDIP_SERIAL_gte(rcvd_serial, sent_serial + 1) &&
          !(asoc->addip_last_asconf)) {
            abort = sctp_make_abort(asoc, asconf_ack,
                              sizeof(sctp_errhdr_t));
            if (abort) {
                  sctp_init_cause(abort, SCTP_ERROR_ASCONF_ACK, NULL, 0);
                  sctp_add_cmd_sf(commands, SCTP_CMD_REPLY,
                              SCTP_CHUNK(abort));
            }
            /* We are going to ABORT, so we might as well stop
             * processing the rest of the chunks in the packet.
             */
            sctp_add_cmd_sf(commands, SCTP_CMD_TIMER_STOP,
                        SCTP_TO(SCTP_EVENT_TIMEOUT_T4_RTO));
            sctp_add_cmd_sf(commands, SCTP_CMD_DISCARD_PACKET,SCTP_NULL());
            sctp_add_cmd_sf(commands, SCTP_CMD_SET_SK_ERR,
                          SCTP_ERROR(ECONNABORTED));
            sctp_add_cmd_sf(commands, SCTP_CMD_ASSOC_FAILED,
                        SCTP_U32(SCTP_ERROR_ASCONF_ACK));
            SCTP_INC_STATS(SCTP_MIB_ABORTEDS);
            SCTP_DEC_STATS(SCTP_MIB_CURRESTAB);
            return SCTP_DISPOSITION_ABORT;
      }

      if ((rcvd_serial == sent_serial) && asoc->addip_last_asconf) {
            sctp_add_cmd_sf(commands, SCTP_CMD_TIMER_STOP,
                        SCTP_TO(SCTP_EVENT_TIMEOUT_T4_RTO));

            if (!sctp_process_asconf_ack((struct sctp_association *)asoc,
                                   asconf_ack))
                  return SCTP_DISPOSITION_CONSUME;

            abort = sctp_make_abort(asoc, asconf_ack,
                              sizeof(sctp_errhdr_t));
            if (abort) {
                  sctp_init_cause(abort, SCTP_ERROR_RSRC_LOW, NULL, 0);
                  sctp_add_cmd_sf(commands, SCTP_CMD_REPLY,
                              SCTP_CHUNK(abort));
            }
            /* We are going to ABORT, so we might as well stop
             * processing the rest of the chunks in the packet.
             */
            sctp_add_cmd_sf(commands, SCTP_CMD_DISCARD_PACKET,SCTP_NULL());
            sctp_add_cmd_sf(commands, SCTP_CMD_SET_SK_ERR,
                          SCTP_ERROR(ECONNABORTED));
            sctp_add_cmd_sf(commands, SCTP_CMD_ASSOC_FAILED,
                        SCTP_U32(SCTP_ERROR_ASCONF_ACK));
            SCTP_INC_STATS(SCTP_MIB_ABORTEDS);
            SCTP_DEC_STATS(SCTP_MIB_CURRESTAB);
            return SCTP_DISPOSITION_ABORT;
      }

      return SCTP_DISPOSITION_DISCARD;
}

/*
 * PR-SCTP Section 3.6 Receiver Side Implementation of PR-SCTP
 *
 * When a FORWARD TSN chunk arrives, the data receiver MUST first update
 * its cumulative TSN point to the value carried in the FORWARD TSN
 * chunk, and then MUST further advance its cumulative TSN point locally
 * if possible.
 * After the above processing, the data receiver MUST stop reporting any
 * missing TSNs earlier than or equal to the new cumulative TSN point.
 *
 * Verification Tag:  8.5 Verification Tag [Normal verification]
 *
 * The return value is the disposition of the chunk.
 */
sctp_disposition_t sctp_sf_eat_fwd_tsn(const struct sctp_endpoint *ep,
                               const struct sctp_association *asoc,
                               const sctp_subtype_t type,
                               void *arg,
                               sctp_cmd_seq_t *commands)
{
      struct sctp_chunk *chunk = arg;
      struct sctp_fwdtsn_hdr *fwdtsn_hdr;
      __u16 len;
      __u32 tsn;

      if (!sctp_vtag_verify(chunk, asoc)) {
            sctp_add_cmd_sf(commands, SCTP_CMD_REPORT_BAD_TAG,
                        SCTP_NULL());
            return sctp_sf_pdiscard(ep, asoc, type, arg, commands);
      }

      /* Make sure that the FORWARD_TSN chunk has valid length.  */
      if (!sctp_chunk_length_valid(chunk, sizeof(struct sctp_fwdtsn_chunk)))
            return sctp_sf_violation_chunklen(ep, asoc, type, arg,
                                      commands);

      fwdtsn_hdr = (struct sctp_fwdtsn_hdr *)chunk->skb->data;
      chunk->subh.fwdtsn_hdr = fwdtsn_hdr;
      len = ntohs(chunk->chunk_hdr->length);
      len -= sizeof(struct sctp_chunkhdr);
      skb_pull(chunk->skb, len);

      tsn = ntohl(fwdtsn_hdr->new_cum_tsn);
      SCTP_DEBUG_PRINTK("%s: TSN 0x%x.\n", __FUNCTION__, tsn);

      /* The TSN is too high--silently discard the chunk and count on it
       * getting retransmitted later.
       */
      if (sctp_tsnmap_check(&asoc->peer.tsn_map, tsn) < 0)
            goto discard_noforce;

      sctp_add_cmd_sf(commands, SCTP_CMD_REPORT_FWDTSN, SCTP_U32(tsn));
      if (len > sizeof(struct sctp_fwdtsn_hdr))
            sctp_add_cmd_sf(commands, SCTP_CMD_PROCESS_FWDTSN, 
                        SCTP_CHUNK(chunk));
      
      /* Count this as receiving DATA. */
      if (asoc->autoclose) {
            sctp_add_cmd_sf(commands, SCTP_CMD_TIMER_RESTART,
                        SCTP_TO(SCTP_EVENT_TIMEOUT_AUTOCLOSE));
      }
      
      /* FIXME: For now send a SACK, but DATA processing may
       * send another. 
       */
      sctp_add_cmd_sf(commands, SCTP_CMD_GEN_SACK, SCTP_NOFORCE());

      return SCTP_DISPOSITION_CONSUME;

discard_noforce:
      return SCTP_DISPOSITION_DISCARD;
}

sctp_disposition_t sctp_sf_eat_fwd_tsn_fast(
      const struct sctp_endpoint *ep,
      const struct sctp_association *asoc,
      const sctp_subtype_t type,
      void *arg,
      sctp_cmd_seq_t *commands)
{
      struct sctp_chunk *chunk = arg;
      struct sctp_fwdtsn_hdr *fwdtsn_hdr;
      __u16 len;
      __u32 tsn;

      if (!sctp_vtag_verify(chunk, asoc)) {
            sctp_add_cmd_sf(commands, SCTP_CMD_REPORT_BAD_TAG,
                        SCTP_NULL());
            return sctp_sf_pdiscard(ep, asoc, type, arg, commands);
      }

      /* Make sure that the FORWARD_TSN chunk has a valid length.  */
      if (!sctp_chunk_length_valid(chunk, sizeof(struct sctp_fwdtsn_chunk)))
            return sctp_sf_violation_chunklen(ep, asoc, type, arg,
                                      commands);

      fwdtsn_hdr = (struct sctp_fwdtsn_hdr *)chunk->skb->data;
      chunk->subh.fwdtsn_hdr = fwdtsn_hdr;
      len = ntohs(chunk->chunk_hdr->length);
      len -= sizeof(struct sctp_chunkhdr);
      skb_pull(chunk->skb, len);

      tsn = ntohl(fwdtsn_hdr->new_cum_tsn);
      SCTP_DEBUG_PRINTK("%s: TSN 0x%x.\n", __FUNCTION__, tsn);

      /* The TSN is too high--silently discard the chunk and count on it
       * getting retransmitted later.
       */
      if (sctp_tsnmap_check(&asoc->peer.tsn_map, tsn) < 0)
            goto gen_shutdown;

      sctp_add_cmd_sf(commands, SCTP_CMD_REPORT_FWDTSN, SCTP_U32(tsn));
      if (len > sizeof(struct sctp_fwdtsn_hdr))
            sctp_add_cmd_sf(commands, SCTP_CMD_PROCESS_FWDTSN, 
                        SCTP_CHUNK(chunk));
      
      /* Go a head and force a SACK, since we are shutting down. */
gen_shutdown:
      /* Implementor's Guide.
       *
       * While in SHUTDOWN-SENT state, the SHUTDOWN sender MUST immediately
       * respond to each received packet containing one or more DATA chunk(s)
       * with a SACK, a SHUTDOWN chunk, and restart the T2-shutdown timer
       */
      sctp_add_cmd_sf(commands, SCTP_CMD_GEN_SHUTDOWN, SCTP_NULL());
      sctp_add_cmd_sf(commands, SCTP_CMD_GEN_SACK, SCTP_FORCE());
      sctp_add_cmd_sf(commands, SCTP_CMD_TIMER_RESTART,
                  SCTP_TO(SCTP_EVENT_TIMEOUT_T2_SHUTDOWN));

        return SCTP_DISPOSITION_CONSUME;
}

/*
 * Process an unknown chunk.
 *
 * Section: 3.2. Also, 2.1 in the implementor's guide.
 *
 * Chunk Types are encoded such that the highest-order two bits specify
 * the action that must be taken if the processing endpoint does not
 * recognize the Chunk Type.
 *
 * 00 - Stop processing this SCTP packet and discard it, do not process
 *      any further chunks within it.
 *
 * 01 - Stop processing this SCTP packet and discard it, do not process
 *      any further chunks within it, and report the unrecognized
 *      chunk in an 'Unrecognized Chunk Type'.
 *
 * 10 - Skip this chunk and continue processing.
 *
 * 11 - Skip this chunk and continue processing, but report in an ERROR
 *      Chunk using the 'Unrecognized Chunk Type' cause of error.
 *
 * The return value is the disposition of the chunk.
 */
sctp_disposition_t sctp_sf_unk_chunk(const struct sctp_endpoint *ep,
                             const struct sctp_association *asoc,
                             const sctp_subtype_t type,
                             void *arg,
                             sctp_cmd_seq_t *commands)
{
      struct sctp_chunk *unk_chunk = arg;
      struct sctp_chunk *err_chunk;
      sctp_chunkhdr_t *hdr;

      SCTP_DEBUG_PRINTK("Processing the unknown chunk id %d.\n", type.chunk);

      if (!sctp_vtag_verify(unk_chunk, asoc))
            return sctp_sf_pdiscard(ep, asoc, type, arg, commands);

      /* Make sure that the chunk has a valid length.
       * Since we don't know the chunk type, we use a general
       * chunkhdr structure to make a comparison.
       */
      if (!sctp_chunk_length_valid(unk_chunk, sizeof(sctp_chunkhdr_t)))
            return sctp_sf_violation_chunklen(ep, asoc, type, arg,
                                      commands);

      switch (type.chunk & SCTP_CID_ACTION_MASK) {
      case SCTP_CID_ACTION_DISCARD:
            /* Discard the packet.  */
            return sctp_sf_pdiscard(ep, asoc, type, arg, commands);
            break;
      case SCTP_CID_ACTION_DISCARD_ERR:
            /* Discard the packet.  */
            sctp_sf_pdiscard(ep, asoc, type, arg, commands);

            /* Generate an ERROR chunk as response. */
            hdr = unk_chunk->chunk_hdr;
            err_chunk = sctp_make_op_error(asoc, unk_chunk,
                                     SCTP_ERROR_UNKNOWN_CHUNK, hdr,
                                     WORD_ROUND(ntohs(hdr->length)));
            if (err_chunk) {
                  sctp_add_cmd_sf(commands, SCTP_CMD_REPLY,
                              SCTP_CHUNK(err_chunk));
            }
            return SCTP_DISPOSITION_CONSUME;
            break;
      case SCTP_CID_ACTION_SKIP:
            /* Skip the chunk.  */
            return SCTP_DISPOSITION_DISCARD;
            break;
      case SCTP_CID_ACTION_SKIP_ERR:
            /* Generate an ERROR chunk as response. */
            hdr = unk_chunk->chunk_hdr;
            err_chunk = sctp_make_op_error(asoc, unk_chunk,
                                     SCTP_ERROR_UNKNOWN_CHUNK, hdr,
                                     WORD_ROUND(ntohs(hdr->length)));
            if (err_chunk) {
                  sctp_add_cmd_sf(commands, SCTP_CMD_REPLY,
                              SCTP_CHUNK(err_chunk));
            }
            /* Skip the chunk.  */
            return SCTP_DISPOSITION_CONSUME;
            break;
      default:
            break;
      }

      return SCTP_DISPOSITION_DISCARD;
}

/*
 * Discard the chunk.
 *
 * Section: 0.2, 5.2.3, 5.2.5, 5.2.6, 6.0, 8.4.6, 8.5.1c, 9.2
 * [Too numerous to mention...]
 * Verification Tag: No verification needed.
 * Inputs
 * (endpoint, asoc, chunk)
 *
 * Outputs
 * (asoc, reply_msg, msg_up, timers, counters)
 *
 * The return value is the disposition of the chunk.
 */
sctp_disposition_t sctp_sf_discard_chunk(const struct sctp_endpoint *ep,
                               const struct sctp_association *asoc,
                               const sctp_subtype_t type,
                               void *arg,
                               sctp_cmd_seq_t *commands)
{
      SCTP_DEBUG_PRINTK("Chunk %d is discarded\n", type.chunk);
      return SCTP_DISPOSITION_DISCARD;
}

/*
 * Discard the whole packet.
 *
 * Section: 8.4 2)
 *
 * 2) If the OOTB packet contains an ABORT chunk, the receiver MUST
 *    silently discard the OOTB packet and take no further action.
 *
 * Verification Tag: No verification necessary
 *
 * Inputs
 * (endpoint, asoc, chunk)
 *
 * Outputs
 * (asoc, reply_msg, msg_up, timers, counters)
 *
 * The return value is the disposition of the chunk.
 */
sctp_disposition_t sctp_sf_pdiscard(const struct sctp_endpoint *ep,
                            const struct sctp_association *asoc,
                            const sctp_subtype_t type,
                            void *arg,
                            sctp_cmd_seq_t *commands)
{
      sctp_add_cmd_sf(commands, SCTP_CMD_DISCARD_PACKET, SCTP_NULL());

      return SCTP_DISPOSITION_CONSUME;
}


/*
 * The other end is violating protocol.
 *
 * Section: Not specified
 * Verification Tag: Not specified
 * Inputs
 * (endpoint, asoc, chunk)
 *
 * Outputs
 * (asoc, reply_msg, msg_up, timers, counters)
 *
 * We simply tag the chunk as a violation.  The state machine will log
 * the violation and continue.
 */
sctp_disposition_t sctp_sf_violation(const struct sctp_endpoint *ep,
                             const struct sctp_association *asoc,
                             const sctp_subtype_t type,
                             void *arg,
                             sctp_cmd_seq_t *commands)
{
      return SCTP_DISPOSITION_VIOLATION;
}


/*
 * Handle a protocol violation when the chunk length is invalid.
 * "Invalid" length is identified as smaller then the minimal length a
 * given chunk can be.  For example, a SACK chunk has invalid length
 * if it's length is set to be smaller then the size of sctp_sack_chunk_t.
 *
 * We inform the other end by sending an ABORT with a Protocol Violation
 * error code. 
 *
 * Section: Not specified
 * Verification Tag:  Nothing to do
 * Inputs
 * (endpoint, asoc, chunk)
 *
 * Outputs
 * (reply_msg, msg_up, counters)
 *
 * Generate an  ABORT chunk and terminate the association.
 */
static sctp_disposition_t sctp_sf_violation_chunklen(
                             const struct sctp_endpoint *ep,
                             const struct sctp_association *asoc,
                             const sctp_subtype_t type,
                             void *arg,
                             sctp_cmd_seq_t *commands)
{
      struct sctp_chunk *chunk =  arg;
      struct sctp_chunk *abort = NULL;
      char           err_str[]="The following chunk had invalid length:";

      /* Make the abort chunk. */
      abort = sctp_make_abort_violation(asoc, chunk, err_str,
                                sizeof(err_str));
      if (!abort)
            goto nomem;

      sctp_add_cmd_sf(commands, SCTP_CMD_REPLY, SCTP_CHUNK(abort));
      SCTP_INC_STATS(SCTP_MIB_OUTCTRLCHUNKS);

      if (asoc->state <= SCTP_STATE_COOKIE_ECHOED) {
            sctp_add_cmd_sf(commands, SCTP_CMD_TIMER_STOP,
                        SCTP_TO(SCTP_EVENT_TIMEOUT_T1_INIT));
            sctp_add_cmd_sf(commands, SCTP_CMD_SET_SK_ERR,
                        SCTP_ERROR(ECONNREFUSED));
            sctp_add_cmd_sf(commands, SCTP_CMD_INIT_FAILED,
                        SCTP_U32(SCTP_ERROR_PROTO_VIOLATION));
      } else {
            sctp_add_cmd_sf(commands, SCTP_CMD_SET_SK_ERR,
                          SCTP_ERROR(ECONNABORTED));
            sctp_add_cmd_sf(commands, SCTP_CMD_ASSOC_FAILED,
                        SCTP_U32(SCTP_ERROR_PROTO_VIOLATION));
            SCTP_DEC_STATS(SCTP_MIB_CURRESTAB);
      }

      sctp_add_cmd_sf(commands, SCTP_CMD_DISCARD_PACKET, SCTP_NULL());

      SCTP_INC_STATS(SCTP_MIB_ABORTEDS);
      
      return SCTP_DISPOSITION_ABORT;

nomem:
      return SCTP_DISPOSITION_NOMEM;
}

/***************************************************************************
 * These are the state functions for handling primitive (Section 10) events.
 ***************************************************************************/
/*
 * sctp_sf_do_prm_asoc
 *
 * Section: 10.1 ULP-to-SCTP
 * B) Associate
 *
 * Format: ASSOCIATE(local SCTP instance name, destination transport addr,
 * outbound stream count)
 * -> association id [,destination transport addr list] [,outbound stream
 * count]
 *
 * This primitive allows the upper layer to initiate an association to a
 * specific peer endpoint.
 *
 * The peer endpoint shall be specified by one of the transport addresses
 * which defines the endpoint (see Section 1.4).  If the local SCTP
 * instance has not been initialized, the ASSOCIATE is considered an
 * error.
 * [This is not relevant for the kernel implementation since we do all
 * initialization at boot time.  It we hadn't initialized we wouldn't
 * get anywhere near this code.]
 *
 * An association id, which is a local handle to the SCTP association,
 * will be returned on successful establishment of the association. If
 * SCTP is not able to open an SCTP association with the peer endpoint,
 * an error is returned.
 * [In the kernel implementation, the struct sctp_association needs to
 * be created BEFORE causing this primitive to run.]
 *
 * Other association parameters may be returned, including the
 * complete destination transport addresses of the peer as well as the
 * outbound stream count of the local endpoint. One of the transport
 * address from the returned destination addresses will be selected by
 * the local endpoint as default primary path for sending SCTP packets
 * to this peer.  The returned "destination transport addr list" can
 * be used by the ULP to change the default primary path or to force
 * sending a packet to a specific transport address.  [All of this
 * stuff happens when the INIT ACK arrives.  This is a NON-BLOCKING
 * function.]
 *
 * Mandatory attributes:
 *
 * o local SCTP instance name - obtained from the INITIALIZE operation.
 *   [This is the argument asoc.]
 * o destination transport addr - specified as one of the transport
 * addresses of the peer endpoint with which the association is to be
 * established.
 *  [This is asoc->peer.active_path.]
 * o outbound stream count - the number of outbound streams the ULP
 * would like to open towards this peer endpoint.
 * [BUG: This is not currently implemented.]
 * Optional attributes:
 *
 * None.
 *
 * The return value is a disposition.
 */
sctp_disposition_t sctp_sf_do_prm_asoc(const struct sctp_endpoint *ep,
                               const struct sctp_association *asoc,
                               const sctp_subtype_t type,
                               void *arg,
                               sctp_cmd_seq_t *commands)
{
      struct sctp_chunk *repl;

      /* The comment below says that we enter COOKIE-WAIT AFTER
       * sending the INIT, but that doesn't actually work in our
       * implementation...
       */
      sctp_add_cmd_sf(commands, SCTP_CMD_NEW_STATE,
                  SCTP_STATE(SCTP_STATE_COOKIE_WAIT));

      /* RFC 2960 5.1 Normal Establishment of an Association
       *
       * A) "A" first sends an INIT chunk to "Z".  In the INIT, "A"
       * must provide its Verification Tag (Tag_A) in the Initiate
       * Tag field.  Tag_A SHOULD be a random number in the range of
       * 1 to 4294967295 (see 5.3.1 for Tag value selection). ...
       */

      repl = sctp_make_init(asoc, &asoc->base.bind_addr, GFP_ATOMIC, 0);
      if (!repl)
            goto nomem;

      /* Cast away the const modifier, as we want to just
       * rerun it through as a sideffect.
       */
      sctp_add_cmd_sf(commands, SCTP_CMD_NEW_ASOC,
                  SCTP_ASOC((struct sctp_association *) asoc));

      /* Choose transport for INIT. */
      sctp_add_cmd_sf(commands, SCTP_CMD_INIT_CHOOSE_TRANSPORT,
                  SCTP_CHUNK(repl));

      /* After sending the INIT, "A" starts the T1-init timer and
       * enters the COOKIE-WAIT state.
       */
      sctp_add_cmd_sf(commands, SCTP_CMD_TIMER_START,
                  SCTP_TO(SCTP_EVENT_TIMEOUT_T1_INIT));
      sctp_add_cmd_sf(commands, SCTP_CMD_REPLY, SCTP_CHUNK(repl));
      return SCTP_DISPOSITION_CONSUME;

nomem:
      return SCTP_DISPOSITION_NOMEM;
}

/*
 * Process the SEND primitive.
 *
 * Section: 10.1 ULP-to-SCTP
 * E) Send
 *
 * Format: SEND(association id, buffer address, byte count [,context]
 *         [,stream id] [,life time] [,destination transport address]
 *         [,unorder flag] [,no-bundle flag] [,payload protocol-id] )
 * -> result
 *
 * This is the main method to send user data via SCTP.
 *
 * Mandatory attributes:
 *
 *  o association id - local handle to the SCTP association
 *
 *  o buffer address - the location where the user message to be
 *    transmitted is stored;
 *
 *  o byte count - The size of the user data in number of bytes;
 *
 * Optional attributes:
 *
 *  o context - an optional 32 bit integer that will be carried in the
 *    sending failure notification to the ULP if the transportation of
 *    this User Message fails.
 *
 *  o stream id - to indicate which stream to send the data on. If not
 *    specified, stream 0 will be used.
 *
 *  o life time - specifies the life time of the user data. The user data
 *    will not be sent by SCTP after the life time expires. This
 *    parameter can be used to avoid efforts to transmit stale
 *    user messages. SCTP notifies the ULP if the data cannot be
 *    initiated to transport (i.e. sent to the destination via SCTP's
 *    send primitive) within the life time variable. However, the
 *    user data will be transmitted if SCTP has attempted to transmit a
 *    chunk before the life time expired.
 *
 *  o destination transport address - specified as one of the destination
 *    transport addresses of the peer endpoint to which this packet
 *    should be sent. Whenever possible, SCTP should use this destination
 *    transport address for sending the packets, instead of the current
 *    primary path.
 *
 *  o unorder flag - this flag, if present, indicates that the user
 *    would like the data delivered in an unordered fashion to the peer
 *    (i.e., the U flag is set to 1 on all DATA chunks carrying this
 *    message).
 *
 *  o no-bundle flag - instructs SCTP not to bundle this user data with
 *    other outbound DATA chunks. SCTP MAY still bundle even when
 *    this flag is present, when faced with network congestion.
 *
 *  o payload protocol-id - A 32 bit unsigned integer that is to be
 *    passed to the peer indicating the type of payload protocol data
 *    being transmitted. This value is passed as opaque data by SCTP.
 *
 * The return value is the disposition.
 */
sctp_disposition_t sctp_sf_do_prm_send(const struct sctp_endpoint *ep,
                               const struct sctp_association *asoc,
                               const sctp_subtype_t type,
                               void *arg,
                               sctp_cmd_seq_t *commands)
{
      struct sctp_chunk *chunk = arg;

      sctp_add_cmd_sf(commands, SCTP_CMD_REPLY, SCTP_CHUNK(chunk));
      return SCTP_DISPOSITION_CONSUME;
}

/*
 * Process the SHUTDOWN primitive.
 *
 * Section: 10.1:
 * C) Shutdown
 *
 * Format: SHUTDOWN(association id)
 * -> result
 *
 * Gracefully closes an association. Any locally queued user data
 * will be delivered to the peer. The association will be terminated only
 * after the peer acknowledges all the SCTP packets sent.  A success code
 * will be returned on successful termination of the association. If
 * attempting to terminate the association results in a failure, an error
 * code shall be returned.
 *
 * Mandatory attributes:
 *
 *  o association id - local handle to the SCTP association
 *
 * Optional attributes:
 *
 * None.
 *
 * The return value is the disposition.
 */
sctp_disposition_t sctp_sf_do_9_2_prm_shutdown(
      const struct sctp_endpoint *ep,
      const struct sctp_association *asoc,
      const sctp_subtype_t type,
      void *arg,
      sctp_cmd_seq_t *commands)
{
      int disposition;

      /* From 9.2 Shutdown of an Association
       * Upon receipt of the SHUTDOWN primitive from its upper
       * layer, the endpoint enters SHUTDOWN-PENDING state and
       * remains there until all outstanding data has been
       * acknowledged by its peer. The endpoint accepts no new data
       * from its upper layer, but retransmits data to the far end
       * if necessary to fill gaps.
       */
      sctp_add_cmd_sf(commands, SCTP_CMD_NEW_STATE,
                  SCTP_STATE(SCTP_STATE_SHUTDOWN_PENDING));

      /* sctpimpguide-05 Section 2.12.2
       * The sender of the SHUTDOWN MAY also start an overall guard timer
       * 'T5-shutdown-guard' to bound the overall time for shutdown sequence.
       */
      sctp_add_cmd_sf(commands, SCTP_CMD_TIMER_START,
                  SCTP_TO(SCTP_EVENT_TIMEOUT_T5_SHUTDOWN_GUARD));

      disposition = SCTP_DISPOSITION_CONSUME;
      if (sctp_outq_is_empty(&asoc->outqueue)) {
            disposition = sctp_sf_do_9_2_start_shutdown(ep, asoc, type,
                                              arg, commands);
      }
      return disposition;
}

/*
 * Process the ABORT primitive.
 *
 * Section: 10.1:
 * C) Abort
 *
 * Format: Abort(association id [, cause code])
 * -> result
 *
 * Ungracefully closes an association. Any locally queued user data
 * will be discarded and an ABORT chunk is sent to the peer.  A success code
 * will be returned on successful abortion of the association. If
 * attempting to abort the association results in a failure, an error
 * code shall be returned.
 *
 * Mandatory attributes:
 *
 *  o association id - local handle to the SCTP association
 *
 * Optional attributes:
 *
 *  o cause code - reason of the abort to be passed to the peer
 *
 * None.
 *
 * The return value is the disposition.
 */
sctp_disposition_t sctp_sf_do_9_1_prm_abort(
      const struct sctp_endpoint *ep,
      const struct sctp_association *asoc,
      const sctp_subtype_t type,
      void *arg,
      sctp_cmd_seq_t *commands)
{
      /* From 9.1 Abort of an Association
       * Upon receipt of the ABORT primitive from its upper
       * layer, the endpoint enters CLOSED state and
       * discard all outstanding data has been
       * acknowledged by its peer. The endpoint accepts no new data
       * from its upper layer, but retransmits data to the far end
       * if necessary to fill gaps.
       */
      struct sctp_chunk *abort = arg;
      sctp_disposition_t retval;

      retval = SCTP_DISPOSITION_CONSUME;

      sctp_add_cmd_sf(commands, SCTP_CMD_REPLY, SCTP_CHUNK(abort));

      /* Even if we can't send the ABORT due to low memory delete the
       * TCB.  This is a departure from our typical NOMEM handling.
       */

      sctp_add_cmd_sf(commands, SCTP_CMD_SET_SK_ERR,
                  SCTP_ERROR(ECONNABORTED));
      /* Delete the established association. */
      sctp_add_cmd_sf(commands, SCTP_CMD_ASSOC_FAILED,
                  SCTP_U32(SCTP_ERROR_USER_ABORT));

      SCTP_INC_STATS(SCTP_MIB_ABORTEDS);
      SCTP_DEC_STATS(SCTP_MIB_CURRESTAB);

      return retval;
}

/* We tried an illegal operation on an association which is closed.  */
sctp_disposition_t sctp_sf_error_closed(const struct sctp_endpoint *ep,
                              const struct sctp_association *asoc,
                              const sctp_subtype_t type,
                              void *arg,
                              sctp_cmd_seq_t *commands)
{
      sctp_add_cmd_sf(commands, SCTP_CMD_REPORT_ERROR, SCTP_ERROR(-EINVAL));
      return SCTP_DISPOSITION_CONSUME;
}

/* We tried an illegal operation on an association which is shutting
 * down.
 */
sctp_disposition_t sctp_sf_error_shutdown(const struct sctp_endpoint *ep,
                                const struct sctp_association *asoc,
                                const sctp_subtype_t type,
                                void *arg,
                                sctp_cmd_seq_t *commands)
{
      sctp_add_cmd_sf(commands, SCTP_CMD_REPORT_ERROR,
                  SCTP_ERROR(-ESHUTDOWN));
      return SCTP_DISPOSITION_CONSUME;
}

/*
 * sctp_cookie_wait_prm_shutdown
 *
 * Section: 4 Note: 2
 * Verification Tag:
 * Inputs
 * (endpoint, asoc)
 *
 * The RFC does not explicitly address this issue, but is the route through the
 * state table when someone issues a shutdown while in COOKIE_WAIT state.
 *
 * Outputs
 * (timers)
 */
sctp_disposition_t sctp_sf_cookie_wait_prm_shutdown(
      const struct sctp_endpoint *ep,
      const struct sctp_association *asoc,
      const sctp_subtype_t type,
      void *arg,
      sctp_cmd_seq_t *commands)
{
      sctp_add_cmd_sf(commands, SCTP_CMD_TIMER_STOP,
                  SCTP_TO(SCTP_EVENT_TIMEOUT_T1_INIT));

      sctp_add_cmd_sf(commands, SCTP_CMD_NEW_STATE,
                  SCTP_STATE(SCTP_STATE_CLOSED));

      SCTP_INC_STATS(SCTP_MIB_SHUTDOWNS);

      sctp_add_cmd_sf(commands, SCTP_CMD_DELETE_TCB, SCTP_NULL());

      return SCTP_DISPOSITION_DELETE_TCB;
}

/*
 * sctp_cookie_echoed_prm_shutdown
 *
 * Section: 4 Note: 2
 * Verification Tag:
 * Inputs
 * (endpoint, asoc)
 *
 * The RFC does not explcitly address this issue, but is the route through the
 * state table when someone issues a shutdown while in COOKIE_ECHOED state.
 *
 * Outputs
 * (timers)
 */
sctp_disposition_t sctp_sf_cookie_echoed_prm_shutdown(
      const struct sctp_endpoint *ep,
      const struct sctp_association *asoc,
      const sctp_subtype_t type,
      void *arg, sctp_cmd_seq_t *commands)
{
      /* There is a single T1 timer, so we should be able to use
       * common function with the COOKIE-WAIT state.
       */
      return sctp_sf_cookie_wait_prm_shutdown(ep, asoc, type, arg, commands);
}

/*
 * sctp_sf_cookie_wait_prm_abort
 *
 * Section: 4 Note: 2
 * Verification Tag:
 * Inputs
 * (endpoint, asoc)
 *
 * The RFC does not explicitly address this issue, but is the route through the
 * state table when someone issues an abort while in COOKIE_WAIT state.
 *
 * Outputs
 * (timers)
 */
sctp_disposition_t sctp_sf_cookie_wait_prm_abort(
      const struct sctp_endpoint *ep,
      const struct sctp_association *asoc,
      const sctp_subtype_t type,
      void *arg,
      sctp_cmd_seq_t *commands)
{
      struct sctp_chunk *abort = arg;
      sctp_disposition_t retval;

      /* Stop T1-init timer */
      sctp_add_cmd_sf(commands, SCTP_CMD_TIMER_STOP,
                  SCTP_TO(SCTP_EVENT_TIMEOUT_T1_INIT));
      retval = SCTP_DISPOSITION_CONSUME;

      sctp_add_cmd_sf(commands, SCTP_CMD_REPLY, SCTP_CHUNK(abort));

      sctp_add_cmd_sf(commands, SCTP_CMD_NEW_STATE,
                  SCTP_STATE(SCTP_STATE_CLOSED));

      SCTP_INC_STATS(SCTP_MIB_ABORTEDS);

      /* Even if we can't send the ABORT due to low memory delete the
       * TCB.  This is a departure from our typical NOMEM handling.
       */

      sctp_add_cmd_sf(commands, SCTP_CMD_SET_SK_ERR,
                  SCTP_ERROR(ECONNREFUSED));
      /* Delete the established association. */
      sctp_add_cmd_sf(commands, SCTP_CMD_INIT_FAILED,
                  SCTP_U32(SCTP_ERROR_USER_ABORT));

      return retval;
}

/*
 * sctp_sf_cookie_echoed_prm_abort
 *
 * Section: 4 Note: 3
 * Verification Tag:
 * Inputs
 * (endpoint, asoc)
 *
 * The RFC does not explcitly address this issue, but is the route through the
 * state table when someone issues an abort while in COOKIE_ECHOED state.
 *
 * Outputs
 * (timers)
 */
sctp_disposition_t sctp_sf_cookie_echoed_prm_abort(
      const struct sctp_endpoint *ep,
      const struct sctp_association *asoc,
      const sctp_subtype_t type,
      void *arg,
      sctp_cmd_seq_t *commands)
{
      /* There is a single T1 timer, so we should be able to use
       * common function with the COOKIE-WAIT state.
       */
      return sctp_sf_cookie_wait_prm_abort(ep, asoc, type, arg, commands);
}

/*
 * sctp_sf_shutdown_pending_prm_abort
 *
 * Inputs
 * (endpoint, asoc)
 *
 * The RFC does not explicitly address this issue, but is the route through the
 * state table when someone issues an abort while in SHUTDOWN-PENDING state.
 *
 * Outputs
 * (timers)
 */
sctp_disposition_t sctp_sf_shutdown_pending_prm_abort(
      const struct sctp_endpoint *ep,
      const struct sctp_association *asoc,
      const sctp_subtype_t type,
      void *arg,
      sctp_cmd_seq_t *commands)
{
      /* Stop the T5-shutdown guard timer.  */
      sctp_add_cmd_sf(commands, SCTP_CMD_TIMER_STOP,
                  SCTP_TO(SCTP_EVENT_TIMEOUT_T5_SHUTDOWN_GUARD));

      return sctp_sf_do_9_1_prm_abort(ep, asoc, type, arg, commands);
}

/*
 * sctp_sf_shutdown_sent_prm_abort
 *
 * Inputs
 * (endpoint, asoc)
 *
 * The RFC does not explicitly address this issue, but is the route through the
 * state table when someone issues an abort while in SHUTDOWN-SENT state.
 *
 * Outputs
 * (timers)
 */
sctp_disposition_t sctp_sf_shutdown_sent_prm_abort(
      const struct sctp_endpoint *ep,
      const struct sctp_association *asoc,
      const sctp_subtype_t type,
      void *arg,
      sctp_cmd_seq_t *commands)
{
      /* Stop the T2-shutdown timer.  */
      sctp_add_cmd_sf(commands, SCTP_CMD_TIMER_STOP,
                  SCTP_TO(SCTP_EVENT_TIMEOUT_T2_SHUTDOWN));

      /* Stop the T5-shutdown guard timer.  */
      sctp_add_cmd_sf(commands, SCTP_CMD_TIMER_STOP,
                  SCTP_TO(SCTP_EVENT_TIMEOUT_T5_SHUTDOWN_GUARD));

      return sctp_sf_do_9_1_prm_abort(ep, asoc, type, arg, commands);
}

/*
 * sctp_sf_cookie_echoed_prm_abort
 *
 * Inputs
 * (endpoint, asoc)
 *
 * The RFC does not explcitly address this issue, but is the route through the
 * state table when someone issues an abort while in COOKIE_ECHOED state.
 *
 * Outputs
 * (timers)
 */
sctp_disposition_t sctp_sf_shutdown_ack_sent_prm_abort(
      const struct sctp_endpoint *ep,
      const struct sctp_association *asoc,
      const sctp_subtype_t type,
      void *arg,
      sctp_cmd_seq_t *commands)
{
      /* The same T2 timer, so we should be able to use
       * common function with the SHUTDOWN-SENT state.
       */
      return sctp_sf_shutdown_sent_prm_abort(ep, asoc, type, arg, commands);
}

/*
 * Process the REQUESTHEARTBEAT primitive
 *
 * 10.1 ULP-to-SCTP
 * J) Request Heartbeat
 *
 * Format: REQUESTHEARTBEAT(association id, destination transport address)
 *
 * -> result
 *
 * Instructs the local endpoint to perform a HeartBeat on the specified
 * destination transport address of the given association. The returned
 * result should indicate whether the transmission of the HEARTBEAT
 * chunk to the destination address is successful.
 *
 * Mandatory attributes:
 *
 * o association id - local handle to the SCTP association
 *
 * o destination transport address - the transport address of the
 *   association on which a heartbeat should be issued.
 */
sctp_disposition_t sctp_sf_do_prm_requestheartbeat(
                              const struct sctp_endpoint *ep,
                              const struct sctp_association *asoc,
                              const sctp_subtype_t type,
                              void *arg,
                              sctp_cmd_seq_t *commands)
{
      return sctp_sf_heartbeat(ep, asoc, type, (struct sctp_transport *)arg,
                         commands);
}

/*
 * ADDIP Section 4.1 ASCONF Chunk Procedures
 * When an endpoint has an ASCONF signaled change to be sent to the
 * remote endpoint it should do A1 to A9
 */
sctp_disposition_t sctp_sf_do_prm_asconf(const struct sctp_endpoint *ep,
                              const struct sctp_association *asoc,
                              const sctp_subtype_t type,
                              void *arg,
                              sctp_cmd_seq_t *commands)
{
      struct sctp_chunk *chunk = arg;

      sctp_add_cmd_sf(commands, SCTP_CMD_SETUP_T4, SCTP_CHUNK(chunk));
      sctp_add_cmd_sf(commands, SCTP_CMD_TIMER_START,
                  SCTP_TO(SCTP_EVENT_TIMEOUT_T4_RTO));
      sctp_add_cmd_sf(commands, SCTP_CMD_REPLY, SCTP_CHUNK(chunk));
      return SCTP_DISPOSITION_CONSUME;
}

/*
 * Ignore the primitive event
 *
 * The return value is the disposition of the primitive.
 */
sctp_disposition_t sctp_sf_ignore_primitive(
      const struct sctp_endpoint *ep,
      const struct sctp_association *asoc,
      const sctp_subtype_t type,
      void *arg,
      sctp_cmd_seq_t *commands)
{
      SCTP_DEBUG_PRINTK("Primitive type %d is ignored.\n", type.primitive);
      return SCTP_DISPOSITION_DISCARD;
}

/***************************************************************************
 * These are the state functions for the OTHER events.
 ***************************************************************************/

/*
 * Start the shutdown negotiation.
 *
 * From Section 9.2:
 * Once all its outstanding data has been acknowledged, the endpoint
 * shall send a SHUTDOWN chunk to its peer including in the Cumulative
 * TSN Ack field the last sequential TSN it has received from the peer.
 * It shall then start the T2-shutdown timer and enter the SHUTDOWN-SENT
 * state. If the timer expires, the endpoint must re-send the SHUTDOWN
 * with the updated last sequential TSN received from its peer.
 *
 * The return value is the disposition.
 */
sctp_disposition_t sctp_sf_do_9_2_start_shutdown(
      const struct sctp_endpoint *ep,
      const struct sctp_association *asoc,
      const sctp_subtype_t type,
      void *arg,
      sctp_cmd_seq_t *commands)
{
      struct sctp_chunk *reply;

      /* Once all its outstanding data has been acknowledged, the
       * endpoint shall send a SHUTDOWN chunk to its peer including
       * in the Cumulative TSN Ack field the last sequential TSN it
       * has received from the peer.
       */
      reply = sctp_make_shutdown(asoc, NULL);
      if (!reply)
            goto nomem;

      /* Set the transport for the SHUTDOWN chunk and the timeout for the
       * T2-shutdown timer.
       */
      sctp_add_cmd_sf(commands, SCTP_CMD_SETUP_T2, SCTP_CHUNK(reply));

      /* It shall then start the T2-shutdown timer */
      sctp_add_cmd_sf(commands, SCTP_CMD_TIMER_START,
                  SCTP_TO(SCTP_EVENT_TIMEOUT_T2_SHUTDOWN));

      if (asoc->autoclose)
            sctp_add_cmd_sf(commands, SCTP_CMD_TIMER_STOP,
                        SCTP_TO(SCTP_EVENT_TIMEOUT_AUTOCLOSE));

      /* and enter the SHUTDOWN-SENT state.  */
      sctp_add_cmd_sf(commands, SCTP_CMD_NEW_STATE,
                  SCTP_STATE(SCTP_STATE_SHUTDOWN_SENT));

      /* sctp-implguide 2.10 Issues with Heartbeating and failover
       *
       * HEARTBEAT ... is discontinued after sending either SHUTDOWN
         * or SHUTDOWN-ACK.
       */
      sctp_add_cmd_sf(commands, SCTP_CMD_HB_TIMERS_STOP, SCTP_NULL());

      sctp_add_cmd_sf(commands, SCTP_CMD_REPLY, SCTP_CHUNK(reply));

      return SCTP_DISPOSITION_CONSUME;

nomem:
      return SCTP_DISPOSITION_NOMEM;
}

/*
 * Generate a SHUTDOWN ACK now that everything is SACK'd.
 *
 * From Section 9.2:
 *
 * If it has no more outstanding DATA chunks, the SHUTDOWN receiver
 * shall send a SHUTDOWN ACK and start a T2-shutdown timer of its own,
 * entering the SHUTDOWN-ACK-SENT state. If the timer expires, the
 * endpoint must re-send the SHUTDOWN ACK.
 *
 * The return value is the disposition.
 */
sctp_disposition_t sctp_sf_do_9_2_shutdown_ack(
      const struct sctp_endpoint *ep,
      const struct sctp_association *asoc,
      const sctp_subtype_t type,
      void *arg,
      sctp_cmd_seq_t *commands)
{
      struct sctp_chunk *chunk = (struct sctp_chunk *) arg;
      struct sctp_chunk *reply;

      /* There are 2 ways of getting here:
       *    1) called in response to a SHUTDOWN chunk
       *    2) called when SCTP_EVENT_NO_PENDING_TSN event is issued.
       *
       * For the case (2), the arg parameter is set to NULL.  We need
       * to check that we have a chunk before accessing it's fields.
       */
      if (chunk) {
            if (!sctp_vtag_verify(chunk, asoc))
                  return sctp_sf_pdiscard(ep, asoc, type, arg, commands);

            /* Make sure that the SHUTDOWN chunk has a valid length. */
            if (!sctp_chunk_length_valid(chunk, sizeof(struct sctp_shutdown_chunk_t)))
                  return sctp_sf_violation_chunklen(ep, asoc, type, arg,
                                            commands);
      }

      /* If it has no more outstanding DATA chunks, the SHUTDOWN receiver
       * shall send a SHUTDOWN ACK ...
       */
      reply = sctp_make_shutdown_ack(asoc, chunk);
      if (!reply)
            goto nomem;

      /* Set the transport for the SHUTDOWN ACK chunk and the timeout for
       * the T2-shutdown timer.
       */
      sctp_add_cmd_sf(commands, SCTP_CMD_SETUP_T2, SCTP_CHUNK(reply));

      /* and start/restart a T2-shutdown timer of its own, */
      sctp_add_cmd_sf(commands, SCTP_CMD_TIMER_RESTART,
                  SCTP_TO(SCTP_EVENT_TIMEOUT_T2_SHUTDOWN));

      if (asoc->autoclose)
            sctp_add_cmd_sf(commands, SCTP_CMD_TIMER_STOP,
                        SCTP_TO(SCTP_EVENT_TIMEOUT_AUTOCLOSE));

      /* Enter the SHUTDOWN-ACK-SENT state.  */
      sctp_add_cmd_sf(commands, SCTP_CMD_NEW_STATE,
                  SCTP_STATE(SCTP_STATE_SHUTDOWN_ACK_SENT));

      /* sctp-implguide 2.10 Issues with Heartbeating and failover
       *
       * HEARTBEAT ... is discontinued after sending either SHUTDOWN
         * or SHUTDOWN-ACK.
       */
      sctp_add_cmd_sf(commands, SCTP_CMD_HB_TIMERS_STOP, SCTP_NULL());

      sctp_add_cmd_sf(commands, SCTP_CMD_REPLY, SCTP_CHUNK(reply));

      return SCTP_DISPOSITION_CONSUME;

nomem:
      return SCTP_DISPOSITION_NOMEM;
}

/*
 * Ignore the event defined as other
 *
 * The return value is the disposition of the event.
 */
sctp_disposition_t sctp_sf_ignore_other(const struct sctp_endpoint *ep,
                              const struct sctp_association *asoc,
                              const sctp_subtype_t type,
                              void *arg,
                              sctp_cmd_seq_t *commands)
{
      SCTP_DEBUG_PRINTK("The event other type %d is ignored\n", type.other);
      return SCTP_DISPOSITION_DISCARD;
}

/************************************************************
 * These are the state functions for handling timeout events.
 ************************************************************/

/*
 * RTX Timeout
 *
 * Section: 6.3.3 Handle T3-rtx Expiration
 *
 * Whenever the retransmission timer T3-rtx expires for a destination
 * address, do the following:
 * [See below]
 *
 * The return value is the disposition of the chunk.
 */
sctp_disposition_t sctp_sf_do_6_3_3_rtx(const struct sctp_endpoint *ep,
                              const struct sctp_association *asoc,
                              const sctp_subtype_t type,
                              void *arg,
                              sctp_cmd_seq_t *commands)
{
      struct sctp_transport *transport = arg;

      if (asoc->overall_error_count >= asoc->max_retrans) {
            sctp_add_cmd_sf(commands, SCTP_CMD_SET_SK_ERR,
                        SCTP_ERROR(ETIMEDOUT));
            /* CMD_ASSOC_FAILED calls CMD_DELETE_TCB. */
            sctp_add_cmd_sf(commands, SCTP_CMD_ASSOC_FAILED,
                        SCTP_U32(SCTP_ERROR_NO_ERROR));
            SCTP_INC_STATS(SCTP_MIB_ABORTEDS);
            SCTP_DEC_STATS(SCTP_MIB_CURRESTAB);
            return SCTP_DISPOSITION_DELETE_TCB;
      }

      /* E1) For the destination address for which the timer
       * expires, adjust its ssthresh with rules defined in Section
       * 7.2.3 and set the cwnd <- MTU.
       */

      /* E2) For the destination address for which the timer
       * expires, set RTO <- RTO * 2 ("back off the timer").  The
       * maximum value discussed in rule C7 above (RTO.max) may be
       * used to provide an upper bound to this doubling operation.
       */

      /* E3) Determine how many of the earliest (i.e., lowest TSN)
       * outstanding DATA chunks for the address for which the
       * T3-rtx has expired will fit into a single packet, subject
       * to the MTU constraint for the path corresponding to the
       * destination transport address to which the retransmission
       * is being sent (this may be different from the address for
       * which the timer expires [see Section 6.4]).  Call this
       * value K. Bundle and retransmit those K DATA chunks in a
       * single packet to the destination endpoint.
       *
       * Note: Any DATA chunks that were sent to the address for
       * which the T3-rtx timer expired but did not fit in one MTU
       * (rule E3 above), should be marked for retransmission and
       * sent as soon as cwnd allows (normally when a SACK arrives).
       */

      /* NB: Rules E4 and F1 are implicit in R1.  */
      sctp_add_cmd_sf(commands, SCTP_CMD_RETRAN, SCTP_TRANSPORT(transport));

      /* Do some failure management (Section 8.2). */
      sctp_add_cmd_sf(commands, SCTP_CMD_STRIKE, SCTP_TRANSPORT(transport));

      return SCTP_DISPOSITION_CONSUME;
}

/*
 * Generate delayed SACK on timeout
 *
 * Section: 6.2  Acknowledgement on Reception of DATA Chunks
 *
 * The guidelines on delayed acknowledgement algorithm specified in
 * Section 4.2 of [RFC2581] SHOULD be followed.  Specifically, an
 * acknowledgement SHOULD be generated for at least every second packet
 * (not every second DATA chunk) received, and SHOULD be generated
 * within 200 ms of the arrival of any unacknowledged DATA chunk.  In
 * some situations it may be beneficial for an SCTP transmitter to be
 * more conservative than the algorithms detailed in this document
 * allow. However, an SCTP transmitter MUST NOT be more aggressive than
 * the following algorithms allow.
 */
sctp_disposition_t sctp_sf_do_6_2_sack(const struct sctp_endpoint *ep,
                               const struct sctp_association *asoc,
                               const sctp_subtype_t type,
                               void *arg,
                               sctp_cmd_seq_t *commands)
{
      sctp_add_cmd_sf(commands, SCTP_CMD_GEN_SACK, SCTP_FORCE());
      return SCTP_DISPOSITION_CONSUME;
}

/*
 * sctp_sf_t1_init_timer_expire
 *
 * Section: 4 Note: 2
 * Verification Tag:
 * Inputs
 * (endpoint, asoc)
 *
 *  RFC 2960 Section 4 Notes
 *  2) If the T1-init timer expires, the endpoint MUST retransmit INIT
 *     and re-start the T1-init timer without changing state.  This MUST
 *     be repeated up to 'Max.Init.Retransmits' times.  After that, the
 *     endpoint MUST abort the initialization process and report the
 *     error to SCTP user.
 *
 * Outputs
 * (timers, events)
 *
 */
sctp_disposition_t sctp_sf_t1_init_timer_expire(const struct sctp_endpoint *ep,
                                 const struct sctp_association *asoc,
                                 const sctp_subtype_t type,
                                 void *arg,
                                 sctp_cmd_seq_t *commands)
{
      struct sctp_chunk *repl = NULL;
      struct sctp_bind_addr *bp;
      int attempts = asoc->init_err_counter + 1;

      SCTP_DEBUG_PRINTK("Timer T1 expired (INIT).\n");

      if (attempts <= asoc->max_init_attempts) {
            bp = (struct sctp_bind_addr *) &asoc->base.bind_addr;
            repl = sctp_make_init(asoc, bp, GFP_ATOMIC, 0);
            if (!repl)
                  return SCTP_DISPOSITION_NOMEM;

            /* Choose transport for INIT. */
            sctp_add_cmd_sf(commands, SCTP_CMD_INIT_CHOOSE_TRANSPORT,
                        SCTP_CHUNK(repl));

            /* Issue a sideeffect to do the needed accounting. */
            sctp_add_cmd_sf(commands, SCTP_CMD_INIT_RESTART,
                        SCTP_TO(SCTP_EVENT_TIMEOUT_T1_INIT));

            sctp_add_cmd_sf(commands, SCTP_CMD_REPLY, SCTP_CHUNK(repl));
      } else {
            SCTP_DEBUG_PRINTK("Giving up on INIT, attempts: %d"
                          " max_init_attempts: %d\n",
                          attempts, asoc->max_init_attempts);
            sctp_add_cmd_sf(commands, SCTP_CMD_SET_SK_ERR,
                        SCTP_ERROR(ETIMEDOUT));
            sctp_add_cmd_sf(commands, SCTP_CMD_INIT_FAILED,
                        SCTP_U32(SCTP_ERROR_NO_ERROR));
            return SCTP_DISPOSITION_DELETE_TCB;
      }

      return SCTP_DISPOSITION_CONSUME;
}

/*
 * sctp_sf_t1_cookie_timer_expire
 *
 * Section: 4 Note: 2
 * Verification Tag:
 * Inputs
 * (endpoint, asoc)
 *
 *  RFC 2960 Section 4 Notes
 *  3) If the T1-cookie timer expires, the endpoint MUST retransmit
 *     COOKIE ECHO and re-start the T1-cookie timer without changing
 *     state.  This MUST be repeated up to 'Max.Init.Retransmits' times.
 *     After that, the endpoint MUST abort the initialization process and
 *     report the error to SCTP user.
 *
 * Outputs
 * (timers, events)
 *
 */
sctp_disposition_t sctp_sf_t1_cookie_timer_expire(const struct sctp_endpoint *ep,
                                 const struct sctp_association *asoc,
                                 const sctp_subtype_t type,
                                 void *arg,
                                 sctp_cmd_seq_t *commands)
{
      struct sctp_chunk *repl = NULL;
      int attempts = asoc->init_err_counter + 1;

      SCTP_DEBUG_PRINTK("Timer T1 expired (COOKIE-ECHO).\n");

      if (attempts <= asoc->max_init_attempts) {
            repl = sctp_make_cookie_echo(asoc, NULL);
            if (!repl)
                  return SCTP_DISPOSITION_NOMEM;

            /* Issue a sideeffect to do the needed accounting. */
            sctp_add_cmd_sf(commands, SCTP_CMD_COOKIEECHO_RESTART,
                        SCTP_TO(SCTP_EVENT_TIMEOUT_T1_COOKIE));

            sctp_add_cmd_sf(commands, SCTP_CMD_REPLY, SCTP_CHUNK(repl));
      } else {
            sctp_add_cmd_sf(commands, SCTP_CMD_SET_SK_ERR,
                        SCTP_ERROR(ETIMEDOUT));
            sctp_add_cmd_sf(commands, SCTP_CMD_INIT_FAILED,
                        SCTP_U32(SCTP_ERROR_NO_ERROR));
            return SCTP_DISPOSITION_DELETE_TCB;
      }

      return SCTP_DISPOSITION_CONSUME;
}

/* RFC2960 9.2 If the timer expires, the endpoint must re-send the SHUTDOWN
 * with the updated last sequential TSN received from its peer.
 *
 * An endpoint should limit the number of retransmissions of the
 * SHUTDOWN chunk to the protocol parameter 'Association.Max.Retrans'.
 * If this threshold is exceeded the endpoint should destroy the TCB and
 * MUST report the peer endpoint unreachable to the upper layer (and
 * thus the association enters the CLOSED state).  The reception of any
 * packet from its peer (i.e. as the peer sends all of its queued DATA
 * chunks) should clear the endpoint's retransmission count and restart
 * the T2-Shutdown timer,  giving its peer ample opportunity to transmit
 * all of its queued DATA chunks that have not yet been sent.
 */
sctp_disposition_t sctp_sf_t2_timer_expire(const struct sctp_endpoint *ep,
                                 const struct sctp_association *asoc,
                                 const sctp_subtype_t type,
                                 void *arg,
                                 sctp_cmd_seq_t *commands)
{
      struct sctp_chunk *reply = NULL;

      SCTP_DEBUG_PRINTK("Timer T2 expired.\n");
      if (asoc->overall_error_count >= asoc->max_retrans) {
            sctp_add_cmd_sf(commands, SCTP_CMD_SET_SK_ERR,
                        SCTP_ERROR(ETIMEDOUT));
            /* Note:  CMD_ASSOC_FAILED calls CMD_DELETE_TCB. */
            sctp_add_cmd_sf(commands, SCTP_CMD_ASSOC_FAILED,
                        SCTP_U32(SCTP_ERROR_NO_ERROR));
            SCTP_INC_STATS(SCTP_MIB_ABORTEDS);
            SCTP_DEC_STATS(SCTP_MIB_CURRESTAB);
            return SCTP_DISPOSITION_DELETE_TCB;
      }

      switch (asoc->state) {
      case SCTP_STATE_SHUTDOWN_SENT:
            reply = sctp_make_shutdown(asoc, NULL);
            break;

      case SCTP_STATE_SHUTDOWN_ACK_SENT:
            reply = sctp_make_shutdown_ack(asoc, NULL);
            break;

      default:
            BUG();
            break;
      };

      if (!reply)
            goto nomem;

      /* Do some failure management (Section 8.2). */
      sctp_add_cmd_sf(commands, SCTP_CMD_STRIKE,
                  SCTP_TRANSPORT(asoc->shutdown_last_sent_to));

      /* Set the transport for the SHUTDOWN/ACK chunk and the timeout for
       * the T2-shutdown timer.
       */
      sctp_add_cmd_sf(commands, SCTP_CMD_SETUP_T2, SCTP_CHUNK(reply));

      /* Restart the T2-shutdown timer.  */
      sctp_add_cmd_sf(commands, SCTP_CMD_TIMER_RESTART,
                  SCTP_TO(SCTP_EVENT_TIMEOUT_T2_SHUTDOWN));
      sctp_add_cmd_sf(commands, SCTP_CMD_REPLY, SCTP_CHUNK(reply));
      return SCTP_DISPOSITION_CONSUME;

nomem:
      return SCTP_DISPOSITION_NOMEM;
}

/*
 * ADDIP Section 4.1 ASCONF CHunk Procedures
 * If the T4 RTO timer expires the endpoint should do B1 to B5
 */
sctp_disposition_t sctp_sf_t4_timer_expire(
      const struct sctp_endpoint *ep,
      const struct sctp_association *asoc,
      const sctp_subtype_t type,
      void *arg,
      sctp_cmd_seq_t *commands)
{
      struct sctp_chunk *chunk = asoc->addip_last_asconf;
      struct sctp_transport *transport = chunk->transport;

      /* ADDIP 4.1 B1) Increment the error counters and perform path failure
       * detection on the appropriate destination address as defined in
       * RFC2960 [5] section 8.1 and 8.2.
       */
      sctp_add_cmd_sf(commands, SCTP_CMD_STRIKE, SCTP_TRANSPORT(transport));

      /* Reconfig T4 timer and transport. */
      sctp_add_cmd_sf(commands, SCTP_CMD_SETUP_T4, SCTP_CHUNK(chunk));

      /* ADDIP 4.1 B2) Increment the association error counters and perform
       * endpoint failure detection on the association as defined in
       * RFC2960 [5] section 8.1 and 8.2.
       * association error counter is incremented in SCTP_CMD_STRIKE.
       */
      if (asoc->overall_error_count >= asoc->max_retrans) {
            sctp_add_cmd_sf(commands, SCTP_CMD_TIMER_STOP,
                        SCTP_TO(SCTP_EVENT_TIMEOUT_T4_RTO));
            sctp_add_cmd_sf(commands, SCTP_CMD_SET_SK_ERR,
                        SCTP_ERROR(ETIMEDOUT));
            sctp_add_cmd_sf(commands, SCTP_CMD_ASSOC_FAILED,
                        SCTP_U32(SCTP_ERROR_NO_ERROR));
            SCTP_INC_STATS(SCTP_MIB_ABORTEDS);
            SCTP_INC_STATS(SCTP_MIB_CURRESTAB);
            return SCTP_DISPOSITION_ABORT;
      }

      /* ADDIP 4.1 B3) Back-off the destination address RTO value to which
       * the ASCONF chunk was sent by doubling the RTO timer value.
       * This is done in SCTP_CMD_STRIKE.
       */

      /* ADDIP 4.1 B4) Re-transmit the ASCONF Chunk last sent and if possible
       * choose an alternate destination address (please refer to RFC2960
       * [5] section 6.4.1). An endpoint MUST NOT add new parameters to this
       * chunk, it MUST be the same (including its serial number) as the last 
       * ASCONF sent.
       */
      sctp_chunk_hold(asoc->addip_last_asconf);
      sctp_add_cmd_sf(commands, SCTP_CMD_REPLY,
                  SCTP_CHUNK(asoc->addip_last_asconf));

      /* ADDIP 4.1 B5) Restart the T-4 RTO timer. Note that if a different
       * destination is selected, then the RTO used will be that of the new
       * destination address.
       */
      sctp_add_cmd_sf(commands, SCTP_CMD_TIMER_RESTART,
                  SCTP_TO(SCTP_EVENT_TIMEOUT_T4_RTO));

      return SCTP_DISPOSITION_CONSUME;
}

/* sctpimpguide-05 Section 2.12.2
 * The sender of the SHUTDOWN MAY also start an overall guard timer
 * 'T5-shutdown-guard' to bound the overall time for shutdown sequence.
 * At the expiration of this timer the sender SHOULD abort the association
 * by sending an ABORT chunk.
 */
sctp_disposition_t sctp_sf_t5_timer_expire(const struct sctp_endpoint *ep,
                                 const struct sctp_association *asoc,
                                 const sctp_subtype_t type,
                                 void *arg,
                                 sctp_cmd_seq_t *commands)
{
      struct sctp_chunk *reply = NULL;

      SCTP_DEBUG_PRINTK("Timer T5 expired.\n");

      reply = sctp_make_abort(asoc, NULL, 0);
      if (!reply)
            goto nomem;

      sctp_add_cmd_sf(commands, SCTP_CMD_REPLY, SCTP_CHUNK(reply));
      sctp_add_cmd_sf(commands, SCTP_CMD_SET_SK_ERR,
                  SCTP_ERROR(ETIMEDOUT));
      sctp_add_cmd_sf(commands, SCTP_CMD_ASSOC_FAILED,
                  SCTP_U32(SCTP_ERROR_NO_ERROR));

      return SCTP_DISPOSITION_DELETE_TCB;
nomem:
      return SCTP_DISPOSITION_NOMEM;
}

/* Handle expiration of AUTOCLOSE timer.  When the autoclose timer expires,
 * the association is automatically closed by starting the shutdown process.
 * The work that needs to be done is same as when SHUTDOWN is initiated by
 * the user.  So this routine looks same as sctp_sf_do_9_2_prm_shutdown().
 */
sctp_disposition_t sctp_sf_autoclose_timer_expire(
      const struct sctp_endpoint *ep,
      const struct sctp_association *asoc,
      const sctp_subtype_t type,
      void *arg,
      sctp_cmd_seq_t *commands)
{
      int disposition;

      /* From 9.2 Shutdown of an Association
       * Upon receipt of the SHUTDOWN primitive from its upper
       * layer, the endpoint enters SHUTDOWN-PENDING state and
       * remains there until all outstanding data has been
       * acknowledged by its peer. The endpoint accepts no new data
       * from its upper layer, but retransmits data to the far end
       * if necessary to fill gaps.
       */
      sctp_add_cmd_sf(commands, SCTP_CMD_NEW_STATE,
                  SCTP_STATE(SCTP_STATE_SHUTDOWN_PENDING));

      /* sctpimpguide-05 Section 2.12.2
       * The sender of the SHUTDOWN MAY also start an overall guard timer
       * 'T5-shutdown-guard' to bound the overall time for shutdown sequence.
       */
      sctp_add_cmd_sf(commands, SCTP_CMD_TIMER_START,
                  SCTP_TO(SCTP_EVENT_TIMEOUT_T5_SHUTDOWN_GUARD));
      disposition = SCTP_DISPOSITION_CONSUME;
      if (sctp_outq_is_empty(&asoc->outqueue)) {
            disposition = sctp_sf_do_9_2_start_shutdown(ep, asoc, type,
                                              arg, commands);
      }
      return disposition;
}

/*****************************************************************************
 * These are sa state functions which could apply to all types of events.
 ****************************************************************************/

/*
 * This table entry is not implemented.
 *
 * Inputs
 * (endpoint, asoc, chunk)
 *
 * The return value is the disposition of the chunk.
 */
sctp_disposition_t sctp_sf_not_impl(const struct sctp_endpoint *ep,
                            const struct sctp_association *asoc,
                            const sctp_subtype_t type,
                            void *arg,
                            sctp_cmd_seq_t *commands)
{
      return SCTP_DISPOSITION_NOT_IMPL;
}

/*
 * This table entry represents a bug.
 *
 * Inputs
 * (endpoint, asoc, chunk)
 *
 * The return value is the disposition of the chunk.
 */
sctp_disposition_t sctp_sf_bug(const struct sctp_endpoint *ep,
                         const struct sctp_association *asoc,
                         const sctp_subtype_t type,
                         void *arg,
                         sctp_cmd_seq_t *commands)
{
      return SCTP_DISPOSITION_BUG;
}

/*
 * This table entry represents the firing of a timer in the wrong state.
 * Since timer deletion cannot be guaranteed a timer 'may' end up firing
 * when the association is in the wrong state.   This event should
 * be ignored, so as to prevent any rearming of the timer.
 *
 * Inputs
 * (endpoint, asoc, chunk)
 *
 * The return value is the disposition of the chunk.
 */
sctp_disposition_t sctp_sf_timer_ignore(const struct sctp_endpoint *ep,
                              const struct sctp_association *asoc,
                              const sctp_subtype_t type,
                              void *arg,
                              sctp_cmd_seq_t *commands)
{
      SCTP_DEBUG_PRINTK("Timer %d ignored.\n", type.chunk);
      return SCTP_DISPOSITION_CONSUME;
}

/********************************************************************
 * 2nd Level Abstractions
 ********************************************************************/

/* Pull the SACK chunk based on the SACK header. */
static struct sctp_sackhdr *sctp_sm_pull_sack(struct sctp_chunk *chunk)
{
      struct sctp_sackhdr *sack;
      unsigned int len;
      __u16 num_blocks;
      __u16 num_dup_tsns;

      /* Protect ourselves from reading too far into
       * the skb from a bogus sender.
       */
      sack = (struct sctp_sackhdr *) chunk->skb->data;

      num_blocks = ntohs(sack->num_gap_ack_blocks);
      num_dup_tsns = ntohs(sack->num_dup_tsns);
      len = sizeof(struct sctp_sackhdr);
      len += (num_blocks + num_dup_tsns) * sizeof(__u32);
      if (len > chunk->skb->len)
            return NULL;

      skb_pull(chunk->skb, len);

      return sack;
}

/* Create an ABORT packet to be sent as a response, with the specified
 * error causes.
 */
static struct sctp_packet *sctp_abort_pkt_new(const struct sctp_endpoint *ep,
                          const struct sctp_association *asoc,
                          struct sctp_chunk *chunk,
                          const void *payload,
                          size_t paylen)
{
      struct sctp_packet *packet;
      struct sctp_chunk *abort;

      packet = sctp_ootb_pkt_new(asoc, chunk);

      if (packet) {
            /* Make an ABORT.
             * The T bit will be set if the asoc is NULL.
             */
            abort = sctp_make_abort(asoc, chunk, paylen);
            if (!abort) {
                  sctp_ootb_pkt_free(packet);
                  return NULL;
            }

            /* Reflect vtag if T-Bit is set */
            if (sctp_test_T_bit(abort))
                  packet->vtag = ntohl(chunk->sctp_hdr->vtag);

            /* Add specified error causes, i.e., payload, to the
             * end of the chunk.
             */
            sctp_addto_chunk(abort, paylen, payload);

            /* Set the skb to the belonging sock for accounting.  */
            abort->skb->sk = ep->base.sk;

            sctp_packet_append_chunk(packet, abort);

      }

      return packet;
}

/* Allocate a packet for responding in the OOTB conditions.  */
static struct sctp_packet *sctp_ootb_pkt_new(const struct sctp_association *asoc,
                                   const struct sctp_chunk *chunk)
{
      struct sctp_packet *packet;
      struct sctp_transport *transport;
      __u16 sport;
      __u16 dport;
      __u32 vtag;

      /* Get the source and destination port from the inbound packet.  */
      sport = ntohs(chunk->sctp_hdr->dest);
      dport = ntohs(chunk->sctp_hdr->source);

      /* The V-tag is going to be the same as the inbound packet if no
       * association exists, otherwise, use the peer's vtag.
       */
      if (asoc) {
            vtag = asoc->peer.i.init_tag;
      } else {
            /* Special case the INIT and stale COOKIE_ECHO as there is no
             * vtag yet.
             */
            switch(chunk->chunk_hdr->type) {
            case SCTP_CID_INIT:
            {
                  sctp_init_chunk_t *init;

                  init = (sctp_init_chunk_t *)chunk->chunk_hdr;
                  vtag = ntohl(init->init_hdr.init_tag);
                  break;
            }
            default:    
                  vtag = ntohl(chunk->sctp_hdr->vtag);
                  break;
            }
      }

      /* Make a transport for the bucket, Eliza... */
      transport = sctp_transport_new(sctp_source(chunk), GFP_ATOMIC);
      if (!transport)
            goto nomem;

      /* Cache a route for the transport with the chunk's destination as
       * the source address.
       */
      sctp_transport_route(transport, (union sctp_addr *)&chunk->dest,
                       sctp_sk(sctp_get_ctl_sock()));

      packet = sctp_packet_init(&transport->packet, transport, sport, dport);
      packet = sctp_packet_config(packet, vtag, 0);

      return packet;

nomem:
      return NULL;
}

/* Free the packet allocated earlier for responding in the OOTB condition.  */
void sctp_ootb_pkt_free(struct sctp_packet *packet)
{
      sctp_transport_free(packet->transport);
}

/* Send a stale cookie error when a invalid COOKIE ECHO chunk is found  */
static void sctp_send_stale_cookie_err(const struct sctp_endpoint *ep,
                               const struct sctp_association *asoc,
                               const struct sctp_chunk *chunk,
                               sctp_cmd_seq_t *commands,
                               struct sctp_chunk *err_chunk)
{
      struct sctp_packet *packet;

      if (err_chunk) {
            packet = sctp_ootb_pkt_new(asoc, chunk);
            if (packet) {
                  struct sctp_signed_cookie *cookie;

                  /* Override the OOTB vtag from the cookie. */
                  cookie = chunk->subh.cookie_hdr;
                  packet->vtag = cookie->c.peer_vtag;
                  
                  /* Set the skb to the belonging sock for accounting. */
                  err_chunk->skb->sk = ep->base.sk;
                  sctp_packet_append_chunk(packet, err_chunk);
                  sctp_add_cmd_sf(commands, SCTP_CMD_SEND_PKT,
                              SCTP_PACKET(packet));
                  SCTP_INC_STATS(SCTP_MIB_OUTCTRLCHUNKS);
            } else
                  sctp_chunk_free (err_chunk);
      }
}


/* Process a data chunk */
static int sctp_eat_data(const struct sctp_association *asoc,
                   struct sctp_chunk *chunk,
                   sctp_cmd_seq_t *commands)
{
      sctp_datahdr_t *data_hdr;
      struct sctp_chunk *err;
      size_t datalen;
      sctp_verb_t deliver;
      int tmp;
      __u32 tsn;
      int account_value;
      struct sctp_tsnmap *map = (struct sctp_tsnmap *)&asoc->peer.tsn_map;
      struct sock *sk = asoc->base.sk;
      int rcvbuf_over = 0;

      data_hdr = chunk->subh.data_hdr = (sctp_datahdr_t *)chunk->skb->data;
      skb_pull(chunk->skb, sizeof(sctp_datahdr_t));

      tsn = ntohl(data_hdr->tsn);
      SCTP_DEBUG_PRINTK("eat_data: TSN 0x%x.\n", tsn);

      /* ASSERT:  Now skb->data is really the user data.  */

      /*
       * If we are established, and we have used up our receive buffer
       * memory, think about droping the frame.
       * Note that we have an opportunity to improve performance here.
       * If we accept one chunk from an skbuff, we have to keep all the
       * memory of that skbuff around until the chunk is read into user
       * space. Therefore, once we accept 1 chunk we may as well accept all
       * remaining chunks in the skbuff. The data_accepted flag helps us do
       * that.
       */
      if ((asoc->state == SCTP_STATE_ESTABLISHED) && (!chunk->data_accepted)) {
            /*
             * If the receive buffer policy is 1, then each
             * association can allocate up to sk_rcvbuf bytes
             * otherwise, all the associations in aggregate
             * may allocate up to sk_rcvbuf bytes
             */
            if (asoc->ep->rcvbuf_policy)
                  account_value = atomic_read(&asoc->rmem_alloc);
            else
                  account_value = atomic_read(&sk->sk_rmem_alloc);
            if (account_value > sk->sk_rcvbuf) {
                  /*
                   * We need to make forward progress, even when we are
                   * under memory pressure, so we always allow the
                   * next tsn after the ctsn ack point to be accepted.
                   * This lets us avoid deadlocks in which we have to
                   * drop frames that would otherwise let us drain the
                   * receive queue.
                   */
                  if ((sctp_tsnmap_get_ctsn(map) + 1) != tsn)
                        return SCTP_IERROR_IGNORE_TSN;

                  /*
                   * We're going to accept the frame but we should renege
                   * to make space for it. This will send us down that
                   * path later in this function.
                   */
                  rcvbuf_over = 1;
            }
      }

      /* Process ECN based congestion.
       *
       * Since the chunk structure is reused for all chunks within
       * a packet, we use ecn_ce_done to track if we've already
       * done CE processing for this packet.
       *
       * We need to do ECN processing even if we plan to discard the
       * chunk later.
       */

      if (!chunk->ecn_ce_done) {
            struct sctp_af *af;
            chunk->ecn_ce_done = 1;

            af = sctp_get_af_specific(
                  ipver2af(chunk->skb->nh.iph->version));

            if (af && af->is_ce(chunk->skb) && asoc->peer.ecn_capable) {
                  /* Do real work as sideffect. */
                  sctp_add_cmd_sf(commands, SCTP_CMD_ECN_CE,
                              SCTP_U32(tsn));
            }
      }

      tmp = sctp_tsnmap_check(&asoc->peer.tsn_map, tsn);
      if (tmp < 0) {
            /* The TSN is too high--silently discard the chunk and
             * count on it getting retransmitted later.
             */
            return SCTP_IERROR_HIGH_TSN;
      } else if (tmp > 0) {
            /* This is a duplicate.  Record it.  */
            sctp_add_cmd_sf(commands, SCTP_CMD_REPORT_DUP, SCTP_U32(tsn));
            return SCTP_IERROR_DUP_TSN;
      }

      /* This is a new TSN.  */

      /* Discard if there is no room in the receive window.
       * Actually, allow a little bit of overflow (up to a MTU).
       */
      datalen = ntohs(chunk->chunk_hdr->length);
      datalen -= sizeof(sctp_data_chunk_t);

      deliver = SCTP_CMD_CHUNK_ULP;

      /* Think about partial delivery. */
      if ((datalen >= asoc->rwnd) && (!asoc->ulpq.pd_mode)) {

            /* Even if we don't accept this chunk there is
             * memory pressure.
             */
            sctp_add_cmd_sf(commands, SCTP_CMD_PART_DELIVER, SCTP_NULL());
      }

        /* Spill over rwnd a little bit.  Note: While allowed, this spill over
       * seems a bit troublesome in that frag_point varies based on
       * PMTU.  In cases, such as loopback, this might be a rather
       * large spill over.
       * NOTE: If we have a full receive buffer here, we only renege if
       * our receiver can still make progress without the tsn being
       * received. We do this because in the event that the associations
       * receive queue is empty we are filling a leading gap, and since
       * reneging moves the gap to the end of the tsn stream, we are likely
       * to stall again very shortly. Avoiding the renege when we fill a
       * leading gap is a good heuristic for avoiding such steady state
       * stalls.
       */
      if (!asoc->rwnd || asoc->rwnd_over ||
          (datalen > asoc->rwnd + asoc->frag_point) ||
          (rcvbuf_over && (!skb_queue_len(&sk->sk_receive_queue)))) {

            /* If this is the next TSN, consider reneging to make
             * room.   Note: Playing nice with a confused sender.  A
             * malicious sender can still eat up all our buffer
             * space and in the future we may want to detect and
             * do more drastic reneging.
             */
            if (sctp_tsnmap_has_gap(map) &&
                (sctp_tsnmap_get_ctsn(map) + 1) == tsn) {
                  SCTP_DEBUG_PRINTK("Reneging for tsn:%u\n", tsn);
                  deliver = SCTP_CMD_RENEGE;
            } else {
                  SCTP_DEBUG_PRINTK("Discard tsn: %u len: %Zd, "
                                "rwnd: %d\n", tsn, datalen,
                                asoc->rwnd);
                  return SCTP_IERROR_IGNORE_TSN;
            }
      }

      /*
       * Section 3.3.10.9 No User Data (9)
       *
       * Cause of error
       * ---------------
       * No User Data:  This error cause is returned to the originator of a
       * DATA chunk if a received DATA chunk has no user data.
       */
      if (unlikely(0 == datalen)) {
            err = sctp_make_abort_no_data(asoc, chunk, tsn);
            if (err) {
                  sctp_add_cmd_sf(commands, SCTP_CMD_REPLY,
                              SCTP_CHUNK(err));
            }
            /* We are going to ABORT, so we might as well stop
             * processing the rest of the chunks in the packet.
             */
            sctp_add_cmd_sf(commands, SCTP_CMD_DISCARD_PACKET,SCTP_NULL());
            sctp_add_cmd_sf(commands, SCTP_CMD_SET_SK_ERR,
                        SCTP_ERROR(ECONNABORTED));
            sctp_add_cmd_sf(commands, SCTP_CMD_ASSOC_FAILED,
                        SCTP_U32(SCTP_ERROR_NO_DATA));
            SCTP_INC_STATS(SCTP_MIB_ABORTEDS);
            SCTP_DEC_STATS(SCTP_MIB_CURRESTAB);
            return SCTP_IERROR_NO_DATA;
      }

      /* If definately accepting the DATA chunk, record its TSN, otherwise
       * wait for renege processing.
       */
      if (SCTP_CMD_CHUNK_ULP == deliver)
            sctp_add_cmd_sf(commands, SCTP_CMD_REPORT_TSN, SCTP_U32(tsn));

      chunk->data_accepted = 1;

      /* Note: Some chunks may get overcounted (if we drop) or overcounted
       * if we renege and the chunk arrives again.
       */
      if (chunk->chunk_hdr->flags & SCTP_DATA_UNORDERED)
            SCTP_INC_STATS(SCTP_MIB_INUNORDERCHUNKS);
      else
            SCTP_INC_STATS(SCTP_MIB_INORDERCHUNKS);

      /* RFC 2960 6.5 Stream Identifier and Stream Sequence Number
       *
       * If an endpoint receive a DATA chunk with an invalid stream
       * identifier, it shall acknowledge the reception of the DATA chunk
       * following the normal procedure, immediately send an ERROR chunk
       * with cause set to "Invalid Stream Identifier" (See Section 3.3.10)
       * and discard the DATA chunk.
       */
      if (ntohs(data_hdr->stream) >= asoc->c.sinit_max_instreams) {
            err = sctp_make_op_error(asoc, chunk, SCTP_ERROR_INV_STRM,
                               &data_hdr->stream,
                               sizeof(data_hdr->stream));
            if (err)
                  sctp_add_cmd_sf(commands, SCTP_CMD_REPLY,
                              SCTP_CHUNK(err));
            return SCTP_IERROR_BAD_STREAM;
      }

      /* Send the data up to the user.  Note:  Schedule  the
       * SCTP_CMD_CHUNK_ULP cmd before the SCTP_CMD_GEN_SACK, as the SACK
       * chunk needs the updated rwnd.
       */
      sctp_add_cmd_sf(commands, deliver, SCTP_CHUNK(chunk));

      return SCTP_IERROR_NO_ERROR;
}

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