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sm_make_chunk.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.
 *
 * This file is part of the SCTP kernel reference Implementation
 *
 * These functions work with the state functions in sctp_sm_statefuns.c
 * to implement the state operations.  These functions implement the
 * steps which require modifying existing data structures.
 *
 * 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>
 *    C. Robin              <chris@hundredacre.ac.uk>
 *    Jon Grimm             <jgrimm@us.ibm.com>
 *    Xingang Guo           <xingang.guo@intel.com>
 *    Dajiang Zhang         <dajiang.zhang@nokia.com>
 *    Sridhar Samudrala     <sri@us.ibm.com>
 *    Daisy Chang     <daisyc@us.ibm.com>
 *    Ardelle Fan     <ardelle.fan@intel.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 <asm/scatterlist.h>
#include <linux/crypto.h>
#include <net/sock.h>

#include <linux/skbuff.h>
#include <linux/random.h>     /* for get_random_bytes */
#include <net/sctp/sctp.h>
#include <net/sctp/sm.h>

extern kmem_cache_t *sctp_chunk_cachep;

SCTP_STATIC
struct sctp_chunk *sctp_make_chunk(const struct sctp_association *asoc,
                           __u8 type, __u8 flags, int paylen);
static sctp_cookie_param_t *sctp_pack_cookie(const struct sctp_endpoint *ep,
                              const struct sctp_association *asoc,
                              const struct sctp_chunk *init_chunk,
                              int *cookie_len,
                              const __u8 *raw_addrs, int addrs_len);
static int sctp_process_param(struct sctp_association *asoc,
                        union sctp_params param,
                        const union sctp_addr *peer_addr,
                        gfp_t gfp);

/* What was the inbound interface for this chunk? */
int sctp_chunk_iif(const struct sctp_chunk *chunk)
{
      struct sctp_af *af;
      int iif = 0;

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

      return iif;
}

/* RFC 2960 3.3.2 Initiation (INIT) (1)
 *
 * Note 2: The ECN capable field is reserved for future use of
 * Explicit Congestion Notification.
 */
static const struct sctp_paramhdr ecap_param = {
      SCTP_PARAM_ECN_CAPABLE,
      __constant_htons(sizeof(struct sctp_paramhdr)),
};
static const struct sctp_paramhdr prsctp_param = {
      SCTP_PARAM_FWD_TSN_SUPPORT,
      __constant_htons(sizeof(struct sctp_paramhdr)),
};

/* A helper to initialize to initialize an op error inside a
 * provided chunk, as most cause codes will be embedded inside an
 * abort chunk.
 */
void  sctp_init_cause(struct sctp_chunk *chunk, __u16 cause_code,
                  const void *payload, size_t paylen)
{
      sctp_errhdr_t err;
      int padlen;
      __u16 len;

        /* Cause code constants are now defined in network order.  */
      err.cause = cause_code;
      len = sizeof(sctp_errhdr_t) + paylen;
      padlen = len % 4;
      err.length  = htons(len);
      len += padlen;
      sctp_addto_chunk(chunk, sizeof(sctp_errhdr_t), &err);
      chunk->subh.err_hdr = sctp_addto_chunk(chunk, paylen, payload);
}

/* 3.3.2 Initiation (INIT) (1)
 *
 * This chunk is used to initiate a SCTP association between two
 * endpoints. The format of the INIT chunk is shown below:
 *
 *     0                   1                   2                   3
 *     0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
 *    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 *    |   Type = 1    |  Chunk Flags  |      Chunk Length             |
 *    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 *    |                         Initiate Tag                          |
 *    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 *    |           Advertised Receiver Window Credit (a_rwnd)          |
 *    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 *    |  Number of Outbound Streams   |  Number of Inbound Streams    |
 *    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 *    |                          Initial TSN                          |
 *    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 *    \                                                               \
 *    /              Optional/Variable-Length Parameters              /
 *    \                                                               \
 *    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 *
 *
 * The INIT chunk contains the following parameters. Unless otherwise
 * noted, each parameter MUST only be included once in the INIT chunk.
 *
 * Fixed Parameters                     Status
 * ----------------------------------------------
 * Initiate Tag                        Mandatory
 * Advertised Receiver Window Credit   Mandatory
 * Number of Outbound Streams          Mandatory
 * Number of Inbound Streams           Mandatory
 * Initial TSN                         Mandatory
 *
 * Variable Parameters                  Status     Type Value
 * -------------------------------------------------------------
 * IPv4 Address (Note 1)               Optional    5
 * IPv6 Address (Note 1)               Optional    6
 * Cookie Preservative                 Optional    9
 * Reserved for ECN Capable (Note 2)   Optional    32768 (0x8000)
 * Host Name Address (Note 3)          Optional    11
 * Supported Address Types (Note 4)    Optional    12
 */
struct sctp_chunk *sctp_make_init(const struct sctp_association *asoc,
                       const struct sctp_bind_addr *bp,
                       gfp_t gfp, int vparam_len)
{
      sctp_inithdr_t init;
      union sctp_params addrs;
      size_t chunksize;
      struct sctp_chunk *retval = NULL;
      int num_types, addrs_len = 0;
      struct sctp_sock *sp;
      sctp_supported_addrs_param_t sat;
      __u16 types[2];
      sctp_adaption_ind_param_t aiparam;

      /* RFC 2960 3.3.2 Initiation (INIT) (1)
       *
       * Note 1: The INIT chunks can contain multiple addresses that
       * can be IPv4 and/or IPv6 in any combination.
       */
      retval = NULL;

      /* Convert the provided bind address list to raw format. */
      addrs = sctp_bind_addrs_to_raw(bp, &addrs_len, gfp);

      init.init_tag              = htonl(asoc->c.my_vtag);
      init.a_rwnd          = htonl(asoc->rwnd);
      init.num_outbound_streams  = htons(asoc->c.sinit_num_ostreams);
      init.num_inbound_streams   = htons(asoc->c.sinit_max_instreams);
      init.initial_tsn     = htonl(asoc->c.initial_tsn);

      /* How many address types are needed? */
      sp = sctp_sk(asoc->base.sk);
      num_types = sp->pf->supported_addrs(sp, types);

      chunksize = sizeof(init) + addrs_len + SCTP_SAT_LEN(num_types);
      chunksize += sizeof(ecap_param);
      if (sctp_prsctp_enable)
            chunksize += sizeof(prsctp_param);
      chunksize += sizeof(aiparam);
      chunksize += vparam_len;

      /* RFC 2960 3.3.2 Initiation (INIT) (1)
       *
       * Note 3: An INIT chunk MUST NOT contain more than one Host
       * Name address parameter. Moreover, the sender of the INIT
       * MUST NOT combine any other address types with the Host Name
       * address in the INIT. The receiver of INIT MUST ignore any
       * other address types if the Host Name address parameter is
       * present in the received INIT chunk.
       *
       * PLEASE DO NOT FIXME [This version does not support Host Name.]
       */

      retval = sctp_make_chunk(asoc, SCTP_CID_INIT, 0, chunksize);
      if (!retval)
            goto nodata;

      retval->subh.init_hdr =
            sctp_addto_chunk(retval, sizeof(init), &init);
      retval->param_hdr.v =
            sctp_addto_chunk(retval, addrs_len, addrs.v);

      /* RFC 2960 3.3.2 Initiation (INIT) (1)
       *
       * Note 4: This parameter, when present, specifies all the
       * address types the sending endpoint can support. The absence
       * of this parameter indicates that the sending endpoint can
       * support any address type.
       */
      sat.param_hdr.type = SCTP_PARAM_SUPPORTED_ADDRESS_TYPES;
      sat.param_hdr.length = htons(SCTP_SAT_LEN(num_types));
      sctp_addto_chunk(retval, sizeof(sat), &sat);
      sctp_addto_chunk(retval, num_types * sizeof(__u16), &types);

      sctp_addto_chunk(retval, sizeof(ecap_param), &ecap_param);
      if (sctp_prsctp_enable)
            sctp_addto_chunk(retval, sizeof(prsctp_param), &prsctp_param);
      aiparam.param_hdr.type = SCTP_PARAM_ADAPTION_LAYER_IND;
      aiparam.param_hdr.length = htons(sizeof(aiparam));
      aiparam.adaption_ind = htonl(sp->adaption_ind);
      sctp_addto_chunk(retval, sizeof(aiparam), &aiparam);
nodata:
      kfree(addrs.v);
      return retval;
}

struct sctp_chunk *sctp_make_init_ack(const struct sctp_association *asoc,
                         const struct sctp_chunk *chunk,
                         gfp_t gfp, int unkparam_len)
{
      sctp_inithdr_t initack;
      struct sctp_chunk *retval;
      union sctp_params addrs;
      int addrs_len;
      sctp_cookie_param_t *cookie;
      int cookie_len;
      size_t chunksize;
      sctp_adaption_ind_param_t aiparam;

      retval = NULL;

      /* Note: there may be no addresses to embed. */
      addrs = sctp_bind_addrs_to_raw(&asoc->base.bind_addr, &addrs_len, gfp);

      initack.init_tag          = htonl(asoc->c.my_vtag);
      initack.a_rwnd                = htonl(asoc->rwnd);
      initack.num_outbound_streams  = htons(asoc->c.sinit_num_ostreams);
      initack.num_inbound_streams   = htons(asoc->c.sinit_max_instreams);
      initack.initial_tsn           = htonl(asoc->c.initial_tsn);

      /* FIXME:  We really ought to build the cookie right
       * into the packet instead of allocating more fresh memory.
       */
      cookie = sctp_pack_cookie(asoc->ep, asoc, chunk, &cookie_len,
                          addrs.v, addrs_len);
      if (!cookie)
            goto nomem_cookie;

      /* Calculate the total size of allocation, include the reserved
       * space for reporting unknown parameters if it is specified.
       */
      chunksize = sizeof(initack) + addrs_len + cookie_len + unkparam_len;

        /* Tell peer that we'll do ECN only if peer advertised such cap.  */
      if (asoc->peer.ecn_capable)
            chunksize += sizeof(ecap_param);

        /* Tell peer that we'll do PR-SCTP only if peer advertised.  */
      if (asoc->peer.prsctp_capable)
            chunksize += sizeof(prsctp_param);

      chunksize += sizeof(aiparam);

      /* Now allocate and fill out the chunk.  */
      retval = sctp_make_chunk(asoc, SCTP_CID_INIT_ACK, 0, chunksize);
      if (!retval)
            goto nomem_chunk;

      /* Per the advice in RFC 2960 6.4, send this reply to
       * the source of the INIT packet.
       */
      retval->transport = chunk->transport;
      retval->subh.init_hdr =
            sctp_addto_chunk(retval, sizeof(initack), &initack);
      retval->param_hdr.v = sctp_addto_chunk(retval, addrs_len, addrs.v);
      sctp_addto_chunk(retval, cookie_len, cookie);
      if (asoc->peer.ecn_capable)
            sctp_addto_chunk(retval, sizeof(ecap_param), &ecap_param);
      if (asoc->peer.prsctp_capable)
            sctp_addto_chunk(retval, sizeof(prsctp_param), &prsctp_param);

      aiparam.param_hdr.type = SCTP_PARAM_ADAPTION_LAYER_IND;
      aiparam.param_hdr.length = htons(sizeof(aiparam));
      aiparam.adaption_ind = htonl(sctp_sk(asoc->base.sk)->adaption_ind);
      sctp_addto_chunk(retval, sizeof(aiparam), &aiparam);

      /* We need to remove the const qualifier at this point.  */
      retval->asoc = (struct sctp_association *) asoc;

      /* RFC 2960 6.4 Multi-homed SCTP Endpoints
       *
       * An endpoint SHOULD transmit reply chunks (e.g., SACK,
       * HEARTBEAT ACK, * etc.) to the same destination transport
       * address from which it received the DATA or control chunk
       * to which it is replying.
       *
       * [INIT ACK back to where the INIT came from.]
       */
      if (chunk)
            retval->transport = chunk->transport;

nomem_chunk:
      kfree(cookie);
nomem_cookie:
      kfree(addrs.v);
      return retval;
}

/* 3.3.11 Cookie Echo (COOKIE ECHO) (10):
 *
 * This chunk is used only during the initialization of an association.
 * It is sent by the initiator of an association to its peer to complete
 * the initialization process. This chunk MUST precede any DATA chunk
 * sent within the association, but MAY be bundled with one or more DATA
 * chunks in the same packet.
 *
 *      0                   1                   2                   3
 *      0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
 *     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 *     |   Type = 10   |Chunk  Flags   |         Length                |
 *     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 *     /                     Cookie                                    /
 *     \                                                               \
 *     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 *
 * Chunk Flags: 8 bit
 *
 *   Set to zero on transmit and ignored on receipt.
 *
 * Length: 16 bits (unsigned integer)
 *
 *   Set to the size of the chunk in bytes, including the 4 bytes of
 *   the chunk header and the size of the Cookie.
 *
 * Cookie: variable size
 *
 *   This field must contain the exact cookie received in the
 *   State Cookie parameter from the previous INIT ACK.
 *
 *   An implementation SHOULD make the cookie as small as possible
 *   to insure interoperability.
 */
struct sctp_chunk *sctp_make_cookie_echo(const struct sctp_association *asoc,
                            const struct sctp_chunk *chunk)
{
      struct sctp_chunk *retval;
      void *cookie;
      int cookie_len;

      cookie = asoc->peer.cookie;
      cookie_len = asoc->peer.cookie_len;

      /* Build a cookie echo chunk.  */
      retval = sctp_make_chunk(asoc, SCTP_CID_COOKIE_ECHO, 0, cookie_len);
      if (!retval)
            goto nodata;
      retval->subh.cookie_hdr =
            sctp_addto_chunk(retval, cookie_len, cookie);

      /* RFC 2960 6.4 Multi-homed SCTP Endpoints
       *
       * An endpoint SHOULD transmit reply chunks (e.g., SACK,
       * HEARTBEAT ACK, * etc.) to the same destination transport
       * address from which it * received the DATA or control chunk
       * to which it is replying.
       *
       * [COOKIE ECHO back to where the INIT ACK came from.]
       */
      if (chunk)
            retval->transport = chunk->transport;

nodata:
      return retval;
}

/* 3.3.12 Cookie Acknowledgement (COOKIE ACK) (11):
 *
 * This chunk is used only during the initialization of an
 * association.  It is used to acknowledge the receipt of a COOKIE
 * ECHO chunk.  This chunk MUST precede any DATA or SACK chunk sent
 * within the association, but MAY be bundled with one or more DATA
 * chunks or SACK chunk in the same SCTP packet.
 *
 *      0                   1                   2                   3
 *      0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
 *     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 *     |   Type = 11   |Chunk  Flags   |     Length = 4                |
 *     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 *
 * Chunk Flags: 8 bits
 *
 *   Set to zero on transmit and ignored on receipt.
 */
struct sctp_chunk *sctp_make_cookie_ack(const struct sctp_association *asoc,
                           const struct sctp_chunk *chunk)
{
      struct sctp_chunk *retval;

      retval = sctp_make_chunk(asoc, SCTP_CID_COOKIE_ACK, 0, 0);

      /* RFC 2960 6.4 Multi-homed SCTP Endpoints
       *
       * An endpoint SHOULD transmit reply chunks (e.g., SACK,
       * HEARTBEAT ACK, * etc.) to the same destination transport
       * address from which it * received the DATA or control chunk
       * to which it is replying.
       *
       * [COOKIE ACK back to where the COOKIE ECHO came from.]
       */
      if (retval && chunk)
            retval->transport = chunk->transport;

      return retval;
}

/*
 *  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.
 *
 *     0                   1                   2                   3
 *     0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
 *    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 *    | Chunk Type=13 | Flags=00000000|    Chunk Length = 8           |
 *    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 *    |                      Lowest TSN Number                        |
 *    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 *
 *     Note: The CWR is considered a Control chunk.
 */
struct sctp_chunk *sctp_make_cwr(const struct sctp_association *asoc,
                      const __u32 lowest_tsn,
                      const struct sctp_chunk *chunk)
{
      struct sctp_chunk *retval;
      sctp_cwrhdr_t cwr;

      cwr.lowest_tsn = htonl(lowest_tsn);
      retval = sctp_make_chunk(asoc, SCTP_CID_ECN_CWR, 0,
                         sizeof(sctp_cwrhdr_t));

      if (!retval)
            goto nodata;

      retval->subh.ecn_cwr_hdr =
            sctp_addto_chunk(retval, sizeof(cwr), &cwr);

      /* RFC 2960 6.4 Multi-homed SCTP Endpoints
       *
       * An endpoint SHOULD transmit reply chunks (e.g., SACK,
       * HEARTBEAT ACK, * etc.) to the same destination transport
       * address from which it * received the DATA or control chunk
       * to which it is replying.
       *
       * [Report a reduced congestion window back to where the ECNE
       * came from.]
       */
      if (chunk)
            retval->transport = chunk->transport;

nodata:
      return retval;
}

/* Make an ECNE chunk.  This is a congestion experienced report.  */
struct sctp_chunk *sctp_make_ecne(const struct sctp_association *asoc,
                       const __u32 lowest_tsn)
{
      struct sctp_chunk *retval;
      sctp_ecnehdr_t ecne;

      ecne.lowest_tsn = htonl(lowest_tsn);
      retval = sctp_make_chunk(asoc, SCTP_CID_ECN_ECNE, 0,
                         sizeof(sctp_ecnehdr_t));
      if (!retval)
            goto nodata;
      retval->subh.ecne_hdr =
            sctp_addto_chunk(retval, sizeof(ecne), &ecne);

nodata:
      return retval;
}

/* Make a DATA chunk for the given association from the provided
 * parameters.  However, do not populate the data payload.
 */
struct sctp_chunk *sctp_make_datafrag_empty(struct sctp_association *asoc,
                               const struct sctp_sndrcvinfo *sinfo,
                               int data_len, __u8 flags, __u16 ssn)
{
      struct sctp_chunk *retval;
      struct sctp_datahdr dp;
      int chunk_len;

      /* We assign the TSN as LATE as possible, not here when
       * creating the chunk.
       */
      dp.tsn = 0;
      dp.stream = htons(sinfo->sinfo_stream);
      dp.ppid   = sinfo->sinfo_ppid;

      /* Set the flags for an unordered send.  */
      if (sinfo->sinfo_flags & SCTP_UNORDERED) {
            flags |= SCTP_DATA_UNORDERED;
            dp.ssn = 0;
      } else
            dp.ssn = htons(ssn);

      chunk_len = sizeof(dp) + data_len;
      retval = sctp_make_chunk(asoc, SCTP_CID_DATA, flags, chunk_len);
      if (!retval)
            goto nodata;

      retval->subh.data_hdr = sctp_addto_chunk(retval, sizeof(dp), &dp);
      memcpy(&retval->sinfo, sinfo, sizeof(struct sctp_sndrcvinfo));

nodata:
      return retval;
}

/* Create a selective ackowledgement (SACK) for the given
 * association.  This reports on which TSN's we've seen to date,
 * including duplicates and gaps.
 */
struct sctp_chunk *sctp_make_sack(const struct sctp_association *asoc)
{
      struct sctp_chunk *retval;
      struct sctp_sackhdr sack;
      int len;
      __u32 ctsn;
      __u16 num_gabs, num_dup_tsns;
      struct sctp_tsnmap *map = (struct sctp_tsnmap *)&asoc->peer.tsn_map;

      ctsn = sctp_tsnmap_get_ctsn(map);
      SCTP_DEBUG_PRINTK("sackCTSNAck sent:  0x%x.\n", ctsn);

      /* How much room is needed in the chunk? */
      num_gabs = sctp_tsnmap_num_gabs(map);
      num_dup_tsns = sctp_tsnmap_num_dups(map);

      /* Initialize the SACK header.  */
      sack.cum_tsn_ack      = htonl(ctsn);
      sack.a_rwnd                 = htonl(asoc->a_rwnd);
      sack.num_gap_ack_blocks     = htons(num_gabs);
      sack.num_dup_tsns           = htons(num_dup_tsns);

      len = sizeof(sack)
            + sizeof(struct sctp_gap_ack_block) * num_gabs
            + sizeof(__u32) * num_dup_tsns;

      /* Create the chunk.  */
      retval = sctp_make_chunk(asoc, SCTP_CID_SACK, 0, len);
      if (!retval)
            goto nodata;

      /* RFC 2960 6.4 Multi-homed SCTP Endpoints
       *
       * An endpoint SHOULD transmit reply chunks (e.g., SACK,
       * HEARTBEAT ACK, etc.) to the same destination transport
       * address from which it received the DATA or control chunk to
       * which it is replying.  This rule should also be followed if
       * the endpoint is bundling DATA chunks together with the
       * reply chunk.
       *
       * However, when acknowledging multiple DATA chunks received
       * in packets from different source addresses in a single
       * SACK, the SACK chunk may be transmitted to one of the
       * destination transport addresses from which the DATA or
       * control chunks being acknowledged were received.
       *
       * [BUG:  We do not implement the following paragraph.
       * Perhaps we should remember the last transport we used for a
       * SACK and avoid that (if possible) if we have seen any
       * duplicates. --piggy]
       *
       * When a receiver of a duplicate DATA chunk sends a SACK to a
       * multi- homed endpoint it MAY be beneficial to vary the
       * destination address and not use the source address of the
       * DATA chunk.  The reason being that receiving a duplicate
       * from a multi-homed endpoint might indicate that the return
       * path (as specified in the source address of the DATA chunk)
       * for the SACK is broken.
       *
       * [Send to the address from which we last received a DATA chunk.]
       */
      retval->transport = asoc->peer.last_data_from;

      retval->subh.sack_hdr =
            sctp_addto_chunk(retval, sizeof(sack), &sack);

      /* Add the gap ack block information.   */
      if (num_gabs)
            sctp_addto_chunk(retval, sizeof(__u32) * num_gabs,
                         sctp_tsnmap_get_gabs(map));

      /* Add the duplicate TSN information.  */
      if (num_dup_tsns)
            sctp_addto_chunk(retval, sizeof(__u32) * num_dup_tsns,
                         sctp_tsnmap_get_dups(map));

nodata:
      return retval;
}

/* Make a SHUTDOWN chunk. */
struct sctp_chunk *sctp_make_shutdown(const struct sctp_association *asoc,
                              const struct sctp_chunk *chunk)
{
      struct sctp_chunk *retval;
      sctp_shutdownhdr_t shut;
      __u32 ctsn;

      ctsn = sctp_tsnmap_get_ctsn(&asoc->peer.tsn_map);
      shut.cum_tsn_ack = htonl(ctsn);

      retval = sctp_make_chunk(asoc, SCTP_CID_SHUTDOWN, 0,
                         sizeof(sctp_shutdownhdr_t));
      if (!retval)
            goto nodata;

      retval->subh.shutdown_hdr =
            sctp_addto_chunk(retval, sizeof(shut), &shut);

      if (chunk)
            retval->transport = chunk->transport;
nodata:
      return retval;
}

struct sctp_chunk *sctp_make_shutdown_ack(const struct sctp_association *asoc,
                             const struct sctp_chunk *chunk)
{
      struct sctp_chunk *retval;

      retval = sctp_make_chunk(asoc, SCTP_CID_SHUTDOWN_ACK, 0, 0);

      /* RFC 2960 6.4 Multi-homed SCTP Endpoints
       *
       * An endpoint SHOULD transmit reply chunks (e.g., SACK,
       * HEARTBEAT ACK, * etc.) to the same destination transport
       * address from which it * received the DATA or control chunk
       * to which it is replying.
       *
       * [ACK back to where the SHUTDOWN came from.]
       */
      if (retval && chunk)
            retval->transport = chunk->transport;

      return retval;
}

struct sctp_chunk *sctp_make_shutdown_complete(
      const struct sctp_association *asoc,
      const struct sctp_chunk *chunk)
{
      struct sctp_chunk *retval;
      __u8 flags = 0;

      /* Set the T-bit if we have no association (vtag will be
       * reflected)
       */
      flags |= asoc ? 0 : SCTP_CHUNK_FLAG_T;

      retval = sctp_make_chunk(asoc, SCTP_CID_SHUTDOWN_COMPLETE, flags, 0);

      /* RFC 2960 6.4 Multi-homed SCTP Endpoints
       *
       * An endpoint SHOULD transmit reply chunks (e.g., SACK,
       * HEARTBEAT ACK, * etc.) to the same destination transport
       * address from which it * received the DATA or control chunk
       * to which it is replying.
       *
       * [Report SHUTDOWN COMPLETE back to where the SHUTDOWN ACK
       * came from.]
       */
      if (retval && chunk)
            retval->transport = chunk->transport;

        return retval;
}

/* Create an ABORT.  Note that we set the T bit if we have no
 * association, except when responding to an INIT (sctpimpguide 2.41).
 */
struct sctp_chunk *sctp_make_abort(const struct sctp_association *asoc,
                        const struct sctp_chunk *chunk,
                        const size_t hint)
{
      struct sctp_chunk *retval;
      __u8 flags = 0;

      /* Set the T-bit if we have no association and 'chunk' is not
       * an INIT (vtag will be reflected).
       */
      if (!asoc) {
            if (chunk && chunk->chunk_hdr &&
                chunk->chunk_hdr->type == SCTP_CID_INIT)
                  flags = 0;
            else
                  flags = SCTP_CHUNK_FLAG_T;
      }

      retval = sctp_make_chunk(asoc, SCTP_CID_ABORT, flags, hint);

      /* RFC 2960 6.4 Multi-homed SCTP Endpoints
       *
       * An endpoint SHOULD transmit reply chunks (e.g., SACK,
       * HEARTBEAT ACK, * etc.) to the same destination transport
       * address from which it * received the DATA or control chunk
       * to which it is replying.
       *
       * [ABORT back to where the offender came from.]
       */
      if (retval && chunk)
            retval->transport = chunk->transport;

      return retval;
}

/* Helper to create ABORT with a NO_USER_DATA error.  */
struct sctp_chunk *sctp_make_abort_no_data(
      const struct sctp_association *asoc,
      const struct sctp_chunk *chunk, __u32 tsn)
{
      struct sctp_chunk *retval;
      __u32 payload;

      retval = sctp_make_abort(asoc, chunk, sizeof(sctp_errhdr_t)
                         + sizeof(tsn));

      if (!retval)
            goto no_mem;

      /* Put the tsn back into network byte order.  */
      payload = htonl(tsn);
      sctp_init_cause(retval, SCTP_ERROR_NO_DATA, (const void *)&payload,
                  sizeof(payload));

      /* RFC 2960 6.4 Multi-homed SCTP Endpoints
       *
       * An endpoint SHOULD transmit reply chunks (e.g., SACK,
       * HEARTBEAT ACK, * etc.) to the same destination transport
       * address from which it * received the DATA or control chunk
       * to which it is replying.
       *
       * [ABORT back to where the offender came from.]
       */
      if (chunk)
            retval->transport = chunk->transport;

no_mem:
      return retval;
}

/* Helper to create ABORT with a SCTP_ERROR_USER_ABORT error.  */
struct sctp_chunk *sctp_make_abort_user(const struct sctp_association *asoc,
                              const struct msghdr *msg,
                              size_t paylen)
{
      struct sctp_chunk *retval;
      void *payload = NULL;
      int err;

      retval = sctp_make_abort(asoc, NULL, sizeof(sctp_errhdr_t) + paylen);
      if (!retval)
            goto err_chunk;

      if (paylen) {
            /* Put the msg_iov together into payload.  */
            payload = kmalloc(paylen, GFP_KERNEL);
            if (!payload)
                  goto err_payload;

            err = memcpy_fromiovec(payload, msg->msg_iov, paylen);
            if (err < 0)
                  goto err_copy;
      }

      sctp_init_cause(retval, SCTP_ERROR_USER_ABORT, payload, paylen);

      if (paylen)
            kfree(payload);

      return retval;

err_copy:
      kfree(payload);
err_payload:
      sctp_chunk_free(retval);
      retval = NULL;
err_chunk:
      return retval;
}

/* Make an ABORT chunk with a PROTOCOL VIOLATION cause code. */ 
struct sctp_chunk *sctp_make_abort_violation(
      const struct sctp_association *asoc,
      const struct sctp_chunk *chunk,
      const __u8   *payload,
      const size_t paylen)
{
      struct sctp_chunk  *retval;
      struct sctp_paramhdr phdr;

      retval = sctp_make_abort(asoc, chunk, sizeof(sctp_errhdr_t) + paylen
                              + sizeof(sctp_chunkhdr_t));
      if (!retval)
            goto end;

      sctp_init_cause(retval, SCTP_ERROR_PROTO_VIOLATION, payload, paylen);

      phdr.type = htons(chunk->chunk_hdr->type);
      phdr.length = chunk->chunk_hdr->length;
      sctp_addto_chunk(retval, sizeof(sctp_paramhdr_t), &phdr);

end:
      return retval;
}

/* Make a HEARTBEAT chunk.  */
struct sctp_chunk *sctp_make_heartbeat(const struct sctp_association *asoc,
                          const struct sctp_transport *transport,
                          const void *payload, const size_t paylen)
{
      struct sctp_chunk *retval = sctp_make_chunk(asoc, SCTP_CID_HEARTBEAT,
                                        0, paylen);

      if (!retval)
            goto nodata;

      /* Cast away the 'const', as this is just telling the chunk
       * what transport it belongs to.
       */
      retval->transport = (struct sctp_transport *) transport;
      retval->subh.hbs_hdr = sctp_addto_chunk(retval, paylen, payload);

nodata:
      return retval;
}

struct sctp_chunk *sctp_make_heartbeat_ack(const struct sctp_association *asoc,
                              const struct sctp_chunk *chunk,
                              const void *payload, const size_t paylen)
{
      struct sctp_chunk *retval;

      retval  = sctp_make_chunk(asoc, SCTP_CID_HEARTBEAT_ACK, 0, paylen);
      if (!retval)
            goto nodata;

      retval->subh.hbs_hdr = sctp_addto_chunk(retval, paylen, payload);

      /* RFC 2960 6.4 Multi-homed SCTP Endpoints
       *
       * An endpoint SHOULD transmit reply chunks (e.g., SACK,
       * HEARTBEAT ACK, * etc.) to the same destination transport
       * address from which it * received the DATA or control chunk
       * to which it is replying.
       *
       * [HBACK back to where the HEARTBEAT came from.]
       */
      if (chunk)
            retval->transport = chunk->transport;

nodata:
      return retval;
}

/* Create an Operation Error chunk with the specified space reserved.
 * This routine can be used for containing multiple causes in the chunk.
 */
static struct sctp_chunk *sctp_make_op_error_space(
      const struct sctp_association *asoc,
      const struct sctp_chunk *chunk,
      size_t size)
{
      struct sctp_chunk *retval;

      retval = sctp_make_chunk(asoc, SCTP_CID_ERROR, 0,
                         sizeof(sctp_errhdr_t) + size);
      if (!retval)
            goto nodata;

      /* RFC 2960 6.4 Multi-homed SCTP Endpoints
       *
       * An endpoint SHOULD transmit reply chunks (e.g., SACK,
       * HEARTBEAT ACK, etc.) to the same destination transport
       * address from which it received the DATA or control chunk
       * to which it is replying.
       *
       */
      if (chunk)
            retval->transport = chunk->transport;

nodata:
      return retval;
}

/* Create an Operation Error chunk.  */
struct sctp_chunk *sctp_make_op_error(const struct sctp_association *asoc,
                         const struct sctp_chunk *chunk,
                         __u16 cause_code, const void *payload,
                         size_t paylen)
{
      struct sctp_chunk *retval;

      retval = sctp_make_op_error_space(asoc, chunk, paylen);
      if (!retval)
            goto nodata;

      sctp_init_cause(retval, cause_code, payload, paylen);

nodata:
      return retval;
}

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

/* Turn an skb into a chunk.
 * FIXME: Eventually move the structure directly inside the skb->cb[].
 */
struct sctp_chunk *sctp_chunkify(struct sk_buff *skb,
                      const struct sctp_association *asoc,
                      struct sock *sk)
{
      struct sctp_chunk *retval;

      retval = kmem_cache_alloc(sctp_chunk_cachep, SLAB_ATOMIC);

      if (!retval)
            goto nodata;
      memset(retval, 0, sizeof(struct sctp_chunk));

      if (!sk) {
            SCTP_DEBUG_PRINTK("chunkifying skb %p w/o an sk\n", skb);
      }

      INIT_LIST_HEAD(&retval->list);
      retval->skb       = skb;
      retval->asoc            = (struct sctp_association *)asoc;
      retval->resent    = 0;
      retval->has_tsn         = 0;
      retval->has_ssn         = 0;
      retval->rtt_in_progress = 0;
      retval->sent_at         = 0;
      retval->singleton = 1;
      retval->end_of_packet   = 0;
      retval->ecn_ce_done     = 0;
      retval->pdiscard  = 0;

      /* sctpimpguide-05.txt Section 2.8.2
       * M1) Each time a new DATA chunk is transmitted
       * set the 'TSN.Missing.Report' count for that TSN to 0. The
       * 'TSN.Missing.Report' count will be used to determine missing chunks
       * and when to fast retransmit.
       */
      retval->tsn_missing_report = 0;
      retval->tsn_gap_acked = 0;
      retval->fast_retransmit = 0;

      /* If this is a fragmented message, track all fragments
       * of the message (for SEND_FAILED).
       */
      retval->msg = NULL;

      /* Polish the bead hole.  */
      INIT_LIST_HEAD(&retval->transmitted_list);
      INIT_LIST_HEAD(&retval->frag_list);
      SCTP_DBG_OBJCNT_INC(chunk);
      atomic_set(&retval->refcnt, 1);

nodata:
      return retval;
}

/* Set chunk->source and dest based on the IP header in chunk->skb.  */
void sctp_init_addrs(struct sctp_chunk *chunk, union sctp_addr *src,
                 union sctp_addr *dest)
{
      memcpy(&chunk->source, src, sizeof(union sctp_addr));
      memcpy(&chunk->dest, dest, sizeof(union sctp_addr));
}

/* Extract the source address from a chunk.  */
const union sctp_addr *sctp_source(const struct sctp_chunk *chunk)
{
      /* If we have a known transport, use that.  */
      if (chunk->transport) {
            return &chunk->transport->ipaddr;
      } else {
            /* Otherwise, extract it from the IP header.  */
            return &chunk->source;
      }
}

/* Create a new chunk, setting the type and flags headers from the
 * arguments, reserving enough space for a 'paylen' byte payload.
 */
SCTP_STATIC
struct sctp_chunk *sctp_make_chunk(const struct sctp_association *asoc,
                           __u8 type, __u8 flags, int paylen)
{
      struct sctp_chunk *retval;
      sctp_chunkhdr_t *chunk_hdr;
      struct sk_buff *skb;
      struct sock *sk;

      /* No need to allocate LL here, as this is only a chunk. */
      skb = alloc_skb(WORD_ROUND(sizeof(sctp_chunkhdr_t) + paylen),
                  GFP_ATOMIC);
      if (!skb)
            goto nodata;

      /* Make room for the chunk header.  */
      chunk_hdr = (sctp_chunkhdr_t *)skb_put(skb, sizeof(sctp_chunkhdr_t));
      chunk_hdr->type     = type;
      chunk_hdr->flags  = flags;
      chunk_hdr->length = htons(sizeof(sctp_chunkhdr_t));

      sk = asoc ? asoc->base.sk : NULL;
      retval = sctp_chunkify(skb, asoc, sk);
      if (!retval) {
            kfree_skb(skb);
            goto nodata;
      }

      retval->chunk_hdr = chunk_hdr;
      retval->chunk_end = ((__u8 *)chunk_hdr) + sizeof(struct sctp_chunkhdr);

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

      return retval;
nodata:
      return NULL;
}


/* Release the memory occupied by a chunk.  */
static void sctp_chunk_destroy(struct sctp_chunk *chunk)
{
      /* Free the chunk skb data and the SCTP_chunk stub itself. */
      dev_kfree_skb(chunk->skb);

      SCTP_DBG_OBJCNT_DEC(chunk);
      kmem_cache_free(sctp_chunk_cachep, chunk);
}

/* Possibly, free the chunk.  */
void sctp_chunk_free(struct sctp_chunk *chunk)
{
      BUG_ON(!list_empty(&chunk->list));
      list_del_init(&chunk->transmitted_list);

      /* Release our reference on the message tracker. */
      if (chunk->msg)
            sctp_datamsg_put(chunk->msg);

      sctp_chunk_put(chunk);
}

/* Grab a reference to the chunk. */
void sctp_chunk_hold(struct sctp_chunk *ch)
{
      atomic_inc(&ch->refcnt);
}

/* Release a reference to the chunk. */
void sctp_chunk_put(struct sctp_chunk *ch)
{
      if (atomic_dec_and_test(&ch->refcnt))
            sctp_chunk_destroy(ch);
}

/* Append bytes to the end of a chunk.  Will panic if chunk is not big
 * enough.
 */
void *sctp_addto_chunk(struct sctp_chunk *chunk, int len, const void *data)
{
      void *target;
      void *padding;
      int chunklen = ntohs(chunk->chunk_hdr->length);
      int padlen = chunklen % 4;

      padding = skb_put(chunk->skb, padlen);
      target = skb_put(chunk->skb, len);

      memset(padding, 0, padlen);
      memcpy(target, data, len);

      /* Adjust the chunk length field.  */
      chunk->chunk_hdr->length = htons(chunklen + padlen + len);
      chunk->chunk_end = chunk->skb->tail;

      return target;
}

/* Append bytes from user space to the end of a chunk.  Will panic if
 * chunk is not big enough.
 * Returns a kernel err value.
 */
int sctp_user_addto_chunk(struct sctp_chunk *chunk, int off, int len,
                    struct iovec *data)
{
      __u8 *target;
      int err = 0;

      /* Make room in chunk for data.  */
      target = skb_put(chunk->skb, len);

      /* Copy data (whole iovec) into chunk */
      if ((err = memcpy_fromiovecend(target, data, off, len)))
            goto out;

      /* Adjust the chunk length field.  */
      chunk->chunk_hdr->length =
            htons(ntohs(chunk->chunk_hdr->length) + len);
      chunk->chunk_end = chunk->skb->tail;

out:
      return err;
}

/* Helper function to assign a TSN if needed.  This assumes that both
 * the data_hdr and association have already been assigned.
 */
void sctp_chunk_assign_ssn(struct sctp_chunk *chunk)
{
      __u16 ssn;
      __u16 sid;

      if (chunk->has_ssn)
            return;

      /* This is the last possible instant to assign a SSN. */
      if (chunk->chunk_hdr->flags & SCTP_DATA_UNORDERED) {
            ssn = 0;
      } else {
            sid = htons(chunk->subh.data_hdr->stream);
            if (chunk->chunk_hdr->flags & SCTP_DATA_LAST_FRAG)
                  ssn = sctp_ssn_next(&chunk->asoc->ssnmap->out, sid);
            else
                  ssn = sctp_ssn_peek(&chunk->asoc->ssnmap->out, sid);
            ssn = htons(ssn);
      }

      chunk->subh.data_hdr->ssn = ssn;
      chunk->has_ssn = 1;
}

/* Helper function to assign a TSN if needed.  This assumes that both
 * the data_hdr and association have already been assigned.
 */
void sctp_chunk_assign_tsn(struct sctp_chunk *chunk)
{
      if (!chunk->has_tsn) {
            /* This is the last possible instant to
             * assign a TSN.
             */
            chunk->subh.data_hdr->tsn =
                  htonl(sctp_association_get_next_tsn(chunk->asoc));
            chunk->has_tsn = 1;
      }
}

/* Create a CLOSED association to use with an incoming packet.  */
struct sctp_association *sctp_make_temp_asoc(const struct sctp_endpoint *ep,
                              struct sctp_chunk *chunk,
                              gfp_t gfp)
{
      struct sctp_association *asoc;
      struct sk_buff *skb;
      sctp_scope_t scope;
      struct sctp_af *af;

      /* Create the bare association.  */
      scope = sctp_scope(sctp_source(chunk));
      asoc = sctp_association_new(ep, ep->base.sk, scope, gfp);
      if (!asoc)
            goto nodata;
      asoc->temp = 1;
      skb = chunk->skb;
      /* Create an entry for the source address of the packet.  */
      af = sctp_get_af_specific(ipver2af(skb->nh.iph->version));
      if (unlikely(!af))
            goto fail;
      af->from_skb(&asoc->c.peer_addr, skb, 1);
nodata:
      return asoc;

fail:
      sctp_association_free(asoc);
      return NULL;
}

/* Build a cookie representing asoc.
 * This INCLUDES the param header needed to put the cookie in the INIT ACK.
 */
static sctp_cookie_param_t *sctp_pack_cookie(const struct sctp_endpoint *ep,
                              const struct sctp_association *asoc,
                              const struct sctp_chunk *init_chunk,
                              int *cookie_len,
                              const __u8 *raw_addrs, int addrs_len)
{
      sctp_cookie_param_t *retval;
      struct sctp_signed_cookie *cookie;
      struct scatterlist sg;
      int headersize, bodysize;
      unsigned int keylen;
      char *key;

      /* Header size is static data prior to the actual cookie, including
       * any padding.
       */
      headersize = sizeof(sctp_paramhdr_t) + 
                 (sizeof(struct sctp_signed_cookie) - 
                  sizeof(struct sctp_cookie));
      bodysize = sizeof(struct sctp_cookie)
            + ntohs(init_chunk->chunk_hdr->length) + addrs_len;

      /* Pad out the cookie to a multiple to make the signature
       * functions simpler to write.
       */
      if (bodysize % SCTP_COOKIE_MULTIPLE)
            bodysize += SCTP_COOKIE_MULTIPLE
                  - (bodysize % SCTP_COOKIE_MULTIPLE);
      *cookie_len = headersize + bodysize;

      retval = kmalloc(*cookie_len, GFP_ATOMIC);

      if (!retval) {
            *cookie_len = 0;
            goto nodata;
      }

      /* Clear this memory since we are sending this data structure
       * out on the network.
       */
      memset(retval, 0x00, *cookie_len);
      cookie = (struct sctp_signed_cookie *) retval->body;

      /* Set up the parameter header.  */
      retval->p.type = SCTP_PARAM_STATE_COOKIE;
      retval->p.length = htons(*cookie_len);

      /* Copy the cookie part of the association itself.  */
      cookie->c = asoc->c;
      /* Save the raw address list length in the cookie. */
      cookie->c.raw_addr_list_len = addrs_len;

      /* Remember PR-SCTP capability. */
      cookie->c.prsctp_capable = asoc->peer.prsctp_capable;

      /* Save adaption indication in the cookie. */
      cookie->c.adaption_ind = asoc->peer.adaption_ind;

      /* Set an expiration time for the cookie.  */
      do_gettimeofday(&cookie->c.expiration);
      TIMEVAL_ADD(asoc->cookie_life, cookie->c.expiration);

      /* Copy the peer's init packet.  */
      memcpy(&cookie->c.peer_init[0], init_chunk->chunk_hdr,
             ntohs(init_chunk->chunk_hdr->length));

      /* Copy the raw local address list of the association. */
      memcpy((__u8 *)&cookie->c.peer_init[0] +
             ntohs(init_chunk->chunk_hdr->length), raw_addrs, addrs_len);

      if (sctp_sk(ep->base.sk)->hmac) {
            /* Sign the message.  */
            sg.page = virt_to_page(&cookie->c);
            sg.offset = (unsigned long)(&cookie->c) % PAGE_SIZE;
            sg.length = bodysize;
            keylen = SCTP_SECRET_SIZE;
            key = (char *)ep->secret_key[ep->current_key];

            sctp_crypto_hmac(sctp_sk(ep->base.sk)->hmac, key, &keylen,
                         &sg, 1, cookie->signature);
      }

nodata:
      return retval;
}

/* Unpack the cookie from COOKIE ECHO chunk, recreating the association.  */
struct sctp_association *sctp_unpack_cookie(
      const struct sctp_endpoint *ep,
      const struct sctp_association *asoc,
      struct sctp_chunk *chunk, gfp_t gfp,
      int *error, struct sctp_chunk **errp)
{
      struct sctp_association *retval = NULL;
      struct sctp_signed_cookie *cookie;
      struct sctp_cookie *bear_cookie;
      int headersize, bodysize, fixed_size;
      __u8 *digest = ep->digest;
      struct scatterlist sg;
      unsigned int keylen, len;
      char *key;
      sctp_scope_t scope;
      struct sk_buff *skb = chunk->skb;
      struct timeval tv;

      /* Header size is static data prior to the actual cookie, including
       * any padding.
       */
      headersize = sizeof(sctp_chunkhdr_t) +
                 (sizeof(struct sctp_signed_cookie) - 
                  sizeof(struct sctp_cookie));
      bodysize = ntohs(chunk->chunk_hdr->length) - headersize;
      fixed_size = headersize + sizeof(struct sctp_cookie);

      /* Verify that the chunk looks like it even has a cookie.
       * There must be enough room for our cookie and our peer's
       * INIT chunk.
       */
      len = ntohs(chunk->chunk_hdr->length);
      if (len < fixed_size + sizeof(struct sctp_chunkhdr))
            goto malformed;

      /* Verify that the cookie has been padded out. */
      if (bodysize % SCTP_COOKIE_MULTIPLE)
            goto malformed;

      /* Process the cookie.  */
      cookie = chunk->subh.cookie_hdr;
      bear_cookie = &cookie->c;

      if (!sctp_sk(ep->base.sk)->hmac)
            goto no_hmac;

      /* Check the signature.  */
      keylen = SCTP_SECRET_SIZE;
      sg.page = virt_to_page(bear_cookie);
      sg.offset = (unsigned long)(bear_cookie) % PAGE_SIZE;
      sg.length = bodysize;
      key = (char *)ep->secret_key[ep->current_key];

      memset(digest, 0x00, SCTP_SIGNATURE_SIZE);
      sctp_crypto_hmac(sctp_sk(ep->base.sk)->hmac, key, &keylen, &sg,
                   1, digest);

      if (memcmp(digest, cookie->signature, SCTP_SIGNATURE_SIZE)) {
            /* Try the previous key. */
            key = (char *)ep->secret_key[ep->last_key];
            memset(digest, 0x00, SCTP_SIGNATURE_SIZE);
            sctp_crypto_hmac(sctp_sk(ep->base.sk)->hmac, key, &keylen,
                         &sg, 1, digest);

            if (memcmp(digest, cookie->signature, SCTP_SIGNATURE_SIZE)) {
                  /* Yikes!  Still bad signature! */
                  *error = -SCTP_IERROR_BAD_SIG;
                  goto fail;
            }
      }

no_hmac:
      /* IG Section 2.35.2:
       *  3) Compare the port numbers and the verification tag contained
       *     within the COOKIE ECHO chunk to the actual port numbers and the
       *     verification tag within the SCTP common header of the received
       *     packet. If these values do not match the packet MUST be silently
       *     discarded,
       */
      if (ntohl(chunk->sctp_hdr->vtag) != bear_cookie->my_vtag) {
            *error = -SCTP_IERROR_BAD_TAG;
            goto fail;
      }

      if (ntohs(chunk->sctp_hdr->source) != bear_cookie->peer_addr.v4.sin_port ||
          ntohs(chunk->sctp_hdr->dest) != bear_cookie->my_port) {
            *error = -SCTP_IERROR_BAD_PORTS;
            goto fail;
      }

      /* Check to see if the cookie is stale.  If there is already
       * an association, there is no need to check cookie's expiration
       * for init collision case of lost COOKIE ACK.
       */
      skb_get_timestamp(skb, &tv);
      if (!asoc && tv_lt(bear_cookie->expiration, tv)) {
            __u16 len;
            /*
             * Section 3.3.10.3 Stale Cookie Error (3)
             *
             * Cause of error
             * ---------------
             * Stale Cookie Error:  Indicates the receipt of a valid State
             * Cookie that has expired.
             */
            len = ntohs(chunk->chunk_hdr->length);
            *errp = sctp_make_op_error_space(asoc, chunk, len);
            if (*errp) {
                  suseconds_t usecs = (tv.tv_sec -
                        bear_cookie->expiration.tv_sec) * 1000000L +
                        tv.tv_usec - bear_cookie->expiration.tv_usec;

                  usecs = htonl(usecs);
                  sctp_init_cause(*errp, SCTP_ERROR_STALE_COOKIE,
                              &usecs, sizeof(usecs));
                  *error = -SCTP_IERROR_STALE_COOKIE;
            } else
                  *error = -SCTP_IERROR_NOMEM;

            goto fail;
      }

      /* Make a new base association.  */
      scope = sctp_scope(sctp_source(chunk));
      retval = sctp_association_new(ep, ep->base.sk, scope, gfp);
      if (!retval) {
            *error = -SCTP_IERROR_NOMEM;
            goto fail;
      }

      /* Set up our peer's port number.  */
      retval->peer.port = ntohs(chunk->sctp_hdr->source);

      /* Populate the association from the cookie.  */
      memcpy(&retval->c, bear_cookie, sizeof(*bear_cookie));

      if (sctp_assoc_set_bind_addr_from_cookie(retval, bear_cookie,
                                     GFP_ATOMIC) < 0) {
            *error = -SCTP_IERROR_NOMEM;
            goto fail;
      }

      /* Also, add the destination address. */
      if (list_empty(&retval->base.bind_addr.address_list)) {
            sctp_add_bind_addr(&retval->base.bind_addr, &chunk->dest, 1,
                           GFP_ATOMIC);
      }

      retval->next_tsn = retval->c.initial_tsn;
      retval->ctsn_ack_point = retval->next_tsn - 1;
      retval->addip_serial = retval->c.initial_tsn;
      retval->adv_peer_ack_point = retval->ctsn_ack_point;
      retval->peer.prsctp_capable = retval->c.prsctp_capable;
      retval->peer.adaption_ind = retval->c.adaption_ind;

      /* The INIT stuff will be done by the side effects.  */
      return retval;

fail:
      if (retval)
            sctp_association_free(retval);

      return NULL;

malformed:
      /* Yikes!  The packet is either corrupt or deliberately
       * malformed.
       */
      *error = -SCTP_IERROR_MALFORMED;
      goto fail;
}

/********************************************************************
 * 3rd Level Abstractions
 ********************************************************************/

struct __sctp_missing {
      __u32 num_missing;
      __u16 type;
}  __attribute__((packed));

/*
 * Report a missing mandatory parameter.
 */
static int sctp_process_missing_param(const struct sctp_association *asoc,
                              sctp_param_t paramtype,
                              struct sctp_chunk *chunk,
                              struct sctp_chunk **errp)
{
      struct __sctp_missing report;
      __u16 len;

      len = WORD_ROUND(sizeof(report));

      /* Make an ERROR chunk, preparing enough room for
       * returning multiple unknown parameters.
       */
      if (!*errp)
            *errp = sctp_make_op_error_space(asoc, chunk, len);

      if (*errp) {
            report.num_missing = htonl(1);
            report.type = paramtype;
            sctp_init_cause(*errp, SCTP_ERROR_INV_PARAM,
                        &report, sizeof(report));
      }

      /* Stop processing this chunk. */
      return 0;
}

/* Report an Invalid Mandatory Parameter.  */
static int sctp_process_inv_mandatory(const struct sctp_association *asoc,
                              struct sctp_chunk *chunk,
                              struct sctp_chunk **errp)
{
      /* Invalid Mandatory Parameter Error has no payload. */

      if (!*errp)
            *errp = sctp_make_op_error_space(asoc, chunk, 0);

      if (*errp)
            sctp_init_cause(*errp, SCTP_ERROR_INV_PARAM, NULL, 0);

      /* Stop processing this chunk. */
      return 0;
}

static int sctp_process_inv_paramlength(const struct sctp_association *asoc,
                              struct sctp_paramhdr *param,
                              const struct sctp_chunk *chunk,
                              struct sctp_chunk **errp)
{
      char        error[] = "The following parameter had invalid length:";
      size_t            payload_len = WORD_ROUND(sizeof(error)) + 
                                    sizeof(sctp_paramhdr_t);


      /* Create an error chunk and fill it in with our payload. */
      if (!*errp)
            *errp = sctp_make_op_error_space(asoc, chunk, payload_len);

      if (*errp) {
            sctp_init_cause(*errp, SCTP_ERROR_PROTO_VIOLATION, error,
                        sizeof(error));
            sctp_addto_chunk(*errp, sizeof(sctp_paramhdr_t), param);
      }

      return 0;
}


/* Do not attempt to handle the HOST_NAME parm.  However, do
 * send back an indicator to the peer.
 */
static int sctp_process_hn_param(const struct sctp_association *asoc,
                         union sctp_params param,
                         struct sctp_chunk *chunk,
                         struct sctp_chunk **errp)
{
      __u16 len = ntohs(param.p->length);

      /* Make an ERROR chunk. */
      if (!*errp)
            *errp = sctp_make_op_error_space(asoc, chunk, len);

      if (*errp)
            sctp_init_cause(*errp, SCTP_ERROR_DNS_FAILED,
                        param.v, len);

      /* Stop processing this chunk. */
      return 0;
}

/* RFC 3.2.1 & the Implementers Guide 2.2.
 *
 * The Parameter 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
 * Parameter Type.
 *
 * 00 - Stop processing this SCTP chunk and discard it,
 *    do not process any further chunks within it.
 *
 * 01 - Stop processing this SCTP chunk and discard it,
 *    do not process any further chunks within it, and report
 *    the unrecognized parameter in an 'Unrecognized
 *    Parameter Type' (in either an ERROR or in the INIT ACK).
 *
 * 10 - Skip this parameter and continue processing.
 *
 * 11 - Skip this parameter and continue processing but
 *    report the unrecognized parameter in an
 *    'Unrecognized Parameter Type' (in either an ERROR or in
 *    the INIT ACK).
 *
 * Return value:
 *    0 - discard the chunk
 *    1 - continue with the chunk
 */
static int sctp_process_unk_param(const struct sctp_association *asoc,
                          union sctp_params param,
                          struct sctp_chunk *chunk,
                          struct sctp_chunk **errp)
{
      int retval = 1;

      switch (param.p->type & SCTP_PARAM_ACTION_MASK) {
      case SCTP_PARAM_ACTION_DISCARD:
            retval =  0;
            break;
      case SCTP_PARAM_ACTION_DISCARD_ERR:
            retval =  0;
            /* Make an ERROR chunk, preparing enough room for
             * returning multiple unknown parameters.
             */
            if (NULL == *errp)
                  *errp = sctp_make_op_error_space(asoc, chunk,
                              ntohs(chunk->chunk_hdr->length));

            if (*errp)
                  sctp_init_cause(*errp, SCTP_ERROR_UNKNOWN_PARAM,
                              param.v,
                              WORD_ROUND(ntohs(param.p->length)));

            break;
      case SCTP_PARAM_ACTION_SKIP:
            break;
      case SCTP_PARAM_ACTION_SKIP_ERR:
            /* Make an ERROR chunk, preparing enough room for
             * returning multiple unknown parameters.
             */
            if (NULL == *errp)
                  *errp = sctp_make_op_error_space(asoc, chunk,
                              ntohs(chunk->chunk_hdr->length));

            if (*errp) {
                  sctp_init_cause(*errp, SCTP_ERROR_UNKNOWN_PARAM,
                              param.v,
                              WORD_ROUND(ntohs(param.p->length)));
            } else {
                  /* If there is no memory for generating the ERROR
                   * report as specified, an ABORT will be triggered
                   * to the peer and the association won't be
                   * established.
                   */
                  retval = 0;
            }

            break;
      default:
            break;
      }

      return retval;
}

/* Find unrecognized parameters in the chunk.
 * Return values:
 *    0 - discard the chunk
 *    1 - continue with the chunk
 */
static int sctp_verify_param(const struct sctp_association *asoc,
                       union sctp_params param,
                       sctp_cid_t cid,
                       struct sctp_chunk *chunk,
                       struct sctp_chunk **err_chunk)
{
      int retval = 1;

      /* FIXME - This routine is not looking at each parameter per the
       * chunk type, i.e., unrecognized parameters should be further
       * identified based on the chunk id.
       */

      switch (param.p->type) {
      case SCTP_PARAM_IPV4_ADDRESS:
      case SCTP_PARAM_IPV6_ADDRESS:
      case SCTP_PARAM_COOKIE_PRESERVATIVE:
      case SCTP_PARAM_SUPPORTED_ADDRESS_TYPES:
      case SCTP_PARAM_STATE_COOKIE:
      case SCTP_PARAM_HEARTBEAT_INFO:
      case SCTP_PARAM_UNRECOGNIZED_PARAMETERS:
      case SCTP_PARAM_ECN_CAPABLE:
      case SCTP_PARAM_ADAPTION_LAYER_IND:
            break;

      case SCTP_PARAM_HOST_NAME_ADDRESS:
            /* Tell the peer, we won't support this param.  */
            return sctp_process_hn_param(asoc, param, chunk, err_chunk);
      case SCTP_PARAM_FWD_TSN_SUPPORT:
            if (sctp_prsctp_enable)
                  break;
            /* Fall Through */ 
      default:
            SCTP_DEBUG_PRINTK("Unrecognized param: %d for chunk %d.\n",
                        ntohs(param.p->type), cid);
            return sctp_process_unk_param(asoc, param, chunk, err_chunk);

            break;
      }
      return retval;
}

/* Verify the INIT packet before we process it.  */
int sctp_verify_init(const struct sctp_association *asoc,
                 sctp_cid_t cid,
                 sctp_init_chunk_t *peer_init,
                 struct sctp_chunk *chunk,
                 struct sctp_chunk **errp)
{
      union sctp_params param;
      int has_cookie = 0;

      /* Verify stream values are non-zero. */
      if ((0 == peer_init->init_hdr.num_outbound_streams) ||
          (0 == peer_init->init_hdr.num_inbound_streams)) {

            sctp_process_inv_mandatory(asoc, chunk, errp);
            return 0;
      }

      /* Check for missing mandatory parameters.  */
      sctp_walk_params(param, peer_init, init_hdr.params) {

            if (SCTP_PARAM_STATE_COOKIE == param.p->type)
                  has_cookie = 1;

      } /* for (loop through all parameters) */

      /* There is a possibility that a parameter length was bad and
       * in that case we would have stoped walking the parameters.
       * The current param.p would point at the bad one.
       * Current consensus on the mailing list is to generate a PROTOCOL
       * VIOLATION error.  We build the ERROR chunk here and let the normal
       * error handling code build and send the packet.
       */
      if (param.v < (void*)chunk->chunk_end - sizeof(sctp_paramhdr_t)) {
            sctp_process_inv_paramlength(asoc, param.p, chunk, errp);
            return 0;
      }

      /* The only missing mandatory param possible today is
       * the state cookie for an INIT-ACK chunk.
       */
      if ((SCTP_CID_INIT_ACK == cid) && !has_cookie) {
            sctp_process_missing_param(asoc, SCTP_PARAM_STATE_COOKIE,
                                 chunk, errp);
            return 0;
      }

      /* Find unrecognized parameters. */

      sctp_walk_params(param, peer_init, init_hdr.params) {

            if (!sctp_verify_param(asoc, param, cid, chunk, errp)) {
                  if (SCTP_PARAM_HOST_NAME_ADDRESS == param.p->type)
                        return 0;
                  else
                        return 1;
            }

      } /* for (loop through all parameters) */

      return 1;
}

/* Unpack the parameters in an INIT packet into an association.
 * Returns 0 on failure, else success.
 * FIXME:  This is an association method.
 */
int sctp_process_init(struct sctp_association *asoc, sctp_cid_t cid,
                  const union sctp_addr *peer_addr,
                  sctp_init_chunk_t *peer_init, gfp_t gfp)
{
      union sctp_params param;
      struct sctp_transport *transport;
      struct list_head *pos, *temp;
      char *cookie;

      /* We must include the address that the INIT packet came from.
       * This is the only address that matters for an INIT packet.
       * When processing a COOKIE ECHO, we retrieve the from address
       * of the INIT from the cookie.
       */

      /* This implementation defaults to making the first transport
       * added as the primary transport.  The source address seems to
       * be a a better choice than any of the embedded addresses.
       */
      if (peer_addr)
            if(!sctp_assoc_add_peer(asoc, peer_addr, gfp, SCTP_ACTIVE))
                  goto nomem;

      /* Process the initialization parameters.  */

      sctp_walk_params(param, peer_init, init_hdr.params) {

            if (!sctp_process_param(asoc, param, peer_addr, gfp))
                        goto clean_up;
      }

      /* Walk list of transports, removing transports in the UNKNOWN state. */
      list_for_each_safe(pos, temp, &asoc->peer.transport_addr_list) {
            transport = list_entry(pos, struct sctp_transport, transports);
            if (transport->state == SCTP_UNKNOWN) {
                  sctp_assoc_rm_peer(asoc, transport);
            }
      }

      /* The fixed INIT headers are always in network byte
       * order.
       */
      asoc->peer.i.init_tag =
            ntohl(peer_init->init_hdr.init_tag);
      asoc->peer.i.a_rwnd =
            ntohl(peer_init->init_hdr.a_rwnd);
      asoc->peer.i.num_outbound_streams =
            ntohs(peer_init->init_hdr.num_outbound_streams);
      asoc->peer.i.num_inbound_streams =
            ntohs(peer_init->init_hdr.num_inbound_streams);
      asoc->peer.i.initial_tsn =
            ntohl(peer_init->init_hdr.initial_tsn);

      /* Apply the upper bounds for output streams based on peer's
       * number of inbound streams.
       */
      if (asoc->c.sinit_num_ostreams  >
          ntohs(peer_init->init_hdr.num_inbound_streams)) {
            asoc->c.sinit_num_ostreams =
                  ntohs(peer_init->init_hdr.num_inbound_streams);
      }

      if (asoc->c.sinit_max_instreams >
          ntohs(peer_init->init_hdr.num_outbound_streams)) {
            asoc->c.sinit_max_instreams =
                  ntohs(peer_init->init_hdr.num_outbound_streams);
      }

      /* Copy Initiation tag from INIT to VT_peer in cookie.   */
      asoc->c.peer_vtag = asoc->peer.i.init_tag;

      /* Peer Rwnd   : Current calculated value of the peer's rwnd.  */
      asoc->peer.rwnd = asoc->peer.i.a_rwnd;

      /* Copy cookie in case we need to resend COOKIE-ECHO. */
      cookie = asoc->peer.cookie;
      if (cookie) {
            asoc->peer.cookie = kmalloc(asoc->peer.cookie_len, gfp);
            if (!asoc->peer.cookie)
                  goto clean_up;
            memcpy(asoc->peer.cookie, cookie, asoc->peer.cookie_len);
      }

      /* RFC 2960 7.2.1 The initial value of ssthresh MAY be arbitrarily
       * high (for example, implementations MAY use the size of the receiver
       * advertised window).
       */
      list_for_each(pos, &asoc->peer.transport_addr_list) {
            transport = list_entry(pos, struct sctp_transport, transports);
            transport->ssthresh = asoc->peer.i.a_rwnd;
      }

      /* Set up the TSN tracking pieces.  */
      sctp_tsnmap_init(&asoc->peer.tsn_map, SCTP_TSN_MAP_SIZE,
                   asoc->peer.i.initial_tsn);

      /* RFC 2960 6.5 Stream Identifier and Stream Sequence Number
       *
       * The stream sequence number in all the streams shall start
       * from 0 when the association is established.  Also, when the
       * stream sequence number reaches the value 65535 the next
       * stream sequence number shall be set to 0.
       */

      /* Allocate storage for the negotiated streams if it is not a temporary
       * association.
       */
      if (!asoc->temp) {
            int assoc_id;
            int error;

            asoc->ssnmap = sctp_ssnmap_new(asoc->c.sinit_max_instreams,
                                     asoc->c.sinit_num_ostreams, gfp);
            if (!asoc->ssnmap)
                  goto clean_up;

      retry:
            if (unlikely(!idr_pre_get(&sctp_assocs_id, gfp)))
                  goto clean_up;
            spin_lock_bh(&sctp_assocs_id_lock);
            error = idr_get_new_above(&sctp_assocs_id, (void *)asoc, 1,
                                &assoc_id);
            spin_unlock_bh(&sctp_assocs_id_lock);
            if (error == -EAGAIN)
                  goto retry;
            else if (error)
                  goto clean_up;

            asoc->assoc_id = (sctp_assoc_t) assoc_id;
      }

      /* 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 the following:
       * ...
       * A2) A serial number should be assigned to the Chunk. The serial
       * number should be a monotonically increasing number. All serial
       * numbers are defined to be initialized at the start of the
       * association to the same value as the Initial TSN.
       */
      asoc->peer.addip_serial = asoc->peer.i.initial_tsn - 1;
      return 1;

clean_up:
      /* Release the transport structures. */
      list_for_each_safe(pos, temp, &asoc->peer.transport_addr_list) {
            transport = list_entry(pos, struct sctp_transport, transports);
            list_del_init(pos);
            sctp_transport_free(transport);
      }

      asoc->peer.transport_count = 0;

nomem:
      return 0;
}


/* Update asoc with the option described in param.
 *
 * RFC2960 3.3.2.1 Optional/Variable Length Parameters in INIT
 *
 * asoc is the association to update.
 * param is the variable length parameter to use for update.
 * cid tells us if this is an INIT, INIT ACK or COOKIE ECHO.
 * If the current packet is an INIT we want to minimize the amount of
 * work we do.  In particular, we should not build transport
 * structures for the addresses.
 */
static int sctp_process_param(struct sctp_association *asoc,
                        union sctp_params param,
                        const union sctp_addr *peer_addr,
                        gfp_t gfp)
{
      union sctp_addr addr;
      int i;
      __u16 sat;
      int retval = 1;
      sctp_scope_t scope;
      time_t stale;
      struct sctp_af *af;

      /* We maintain all INIT parameters in network byte order all the
       * time.  This allows us to not worry about whether the parameters
       * came from a fresh INIT, and INIT ACK, or were stored in a cookie.
       */
      switch (param.p->type) {
      case SCTP_PARAM_IPV6_ADDRESS:
            if (PF_INET6 != asoc->base.sk->sk_family)
                  break;
            /* Fall through. */
      case SCTP_PARAM_IPV4_ADDRESS:
            af = sctp_get_af_specific(param_type2af(param.p->type));
            af->from_addr_param(&addr, param.addr, asoc->peer.port, 0);
            scope = sctp_scope(peer_addr);
            if (sctp_in_scope(&addr, scope))
                  if (!sctp_assoc_add_peer(asoc, &addr, gfp, SCTP_UNCONFIRMED))
                        return 0;
            break;

      case SCTP_PARAM_COOKIE_PRESERVATIVE:
            if (!sctp_cookie_preserve_enable)
                  break;

            stale = ntohl(param.life->lifespan_increment);

            /* Suggested Cookie Life span increment's unit is msec,
             * (1/1000sec).
             */
            asoc->cookie_life.tv_sec += stale / 1000;
            asoc->cookie_life.tv_usec += (stale % 1000) * 1000;
            break;

      case SCTP_PARAM_HOST_NAME_ADDRESS:
            SCTP_DEBUG_PRINTK("unimplemented SCTP_HOST_NAME_ADDRESS\n");
            break;

      case SCTP_PARAM_SUPPORTED_ADDRESS_TYPES:
            /* Turn off the default values first so we'll know which
             * ones are really set by the peer.
             */
            asoc->peer.ipv4_address = 0;
            asoc->peer.ipv6_address = 0;

            /* Cycle through address types; avoid divide by 0. */
            sat = ntohs(param.p->length) - sizeof(sctp_paramhdr_t);
            if (sat)
                  sat /= sizeof(__u16);

            for (i = 0; i < sat; ++i) {
                  switch (param.sat->types[i]) {
                  case SCTP_PARAM_IPV4_ADDRESS:
                        asoc->peer.ipv4_address = 1;
                        break;

                  case SCTP_PARAM_IPV6_ADDRESS:
                        asoc->peer.ipv6_address = 1;
                        break;

                  case SCTP_PARAM_HOST_NAME_ADDRESS:
                        asoc->peer.hostname_address = 1;
                        break;

                  default: /* Just ignore anything else.  */
                        break;
                  };
            }
            break;

      case SCTP_PARAM_STATE_COOKIE:
            asoc->peer.cookie_len =
                  ntohs(param.p->length) - sizeof(sctp_paramhdr_t);
            asoc->peer.cookie = param.cookie->body;
            break;

      case SCTP_PARAM_HEARTBEAT_INFO:
            /* Would be odd to receive, but it causes no problems. */
            break;

      case SCTP_PARAM_UNRECOGNIZED_PARAMETERS:
            /* Rejected during verify stage. */
            break;

      case SCTP_PARAM_ECN_CAPABLE:
            asoc->peer.ecn_capable = 1;
            break;

      case SCTP_PARAM_ADAPTION_LAYER_IND:
            asoc->peer.adaption_ind = param.aind->adaption_ind;
            break;

      case SCTP_PARAM_FWD_TSN_SUPPORT:
            if (sctp_prsctp_enable) {
                  asoc->peer.prsctp_capable = 1;
                  break;
            }
            /* Fall Through */ 
      default:
            /* Any unrecognized parameters should have been caught
             * and handled by sctp_verify_param() which should be
             * called prior to this routine.  Simply log the error
             * here.
             */
            SCTP_DEBUG_PRINTK("Ignoring param: %d for association %p.\n",
                          ntohs(param.p->type), asoc);
            break;
      };

      return retval;
}

/* Select a new verification tag.  */
__u32 sctp_generate_tag(const struct sctp_endpoint *ep)
{
      /* I believe that this random number generator complies with RFC1750.
       * A tag of 0 is reserved for special cases (e.g. INIT).
       */
      __u32 x;

      do {
            get_random_bytes(&x, sizeof(__u32));
      } while (x == 0);

      return x;
}

/* Select an initial TSN to send during startup.  */
__u32 sctp_generate_tsn(const struct sctp_endpoint *ep)
{
      __u32 retval;

      get_random_bytes(&retval, sizeof(__u32));
      return retval;
}

/*
 * ADDIP 3.1.1 Address Configuration Change Chunk (ASCONF)
 *      0                   1                   2                   3
 *      0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
 *     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 *     | Type = 0xC1   |  Chunk Flags  |      Chunk Length             |
 *     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 *     |                       Serial Number                           |
 *     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 *     |                    Address Parameter                          |
 *     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 *     |                     ASCONF Parameter #1                       |
 *     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 *     \                                                               \
 *     /                             ....                              /
 *     \                                                               \
 *     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 *     |                     ASCONF Parameter #N                       |
 *      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 *
 * Address Parameter and other parameter will not be wrapped in this function 
 */
static struct sctp_chunk *sctp_make_asconf(struct sctp_association *asoc,
                                 union sctp_addr *addr,
                                 int vparam_len)
{
      sctp_addiphdr_t asconf;
      struct sctp_chunk *retval;
      int length = sizeof(asconf) + vparam_len;
      union sctp_addr_param addrparam;
      int addrlen;
      struct sctp_af *af = sctp_get_af_specific(addr->v4.sin_family);

      addrlen = af->to_addr_param(addr, &addrparam);
      if (!addrlen)
            return NULL;
      length += addrlen;

      /* Create the chunk.  */
      retval = sctp_make_chunk(asoc, SCTP_CID_ASCONF, 0, length);
      if (!retval)
            return NULL;

      asconf.serial = htonl(asoc->addip_serial++);

      retval->subh.addip_hdr =
            sctp_addto_chunk(retval, sizeof(asconf), &asconf);
      retval->param_hdr.v =
            sctp_addto_chunk(retval, addrlen, &addrparam);

      return retval;
}

/* ADDIP
 * 3.2.1 Add IP Address
 *    0                   1                   2                   3
 *    0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
 *     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 *     |        Type = 0xC001          |    Length = Variable          |
 *     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 *     |               ASCONF-Request Correlation ID                   |
 *     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 *     |                       Address Parameter                       |
 *     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 *
 * 3.2.2 Delete IP Address
 *    0                   1                   2                   3
 *    0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
 *     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 *     |        Type = 0xC002          |    Length = Variable          |
 *     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 *     |               ASCONF-Request Correlation ID                   |
 *     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 *     |                       Address Parameter                       |
 *     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 *
 */
struct sctp_chunk *sctp_make_asconf_update_ip(struct sctp_association *asoc,
                                    union sctp_addr         *laddr,
                                    struct sockaddr         *addrs,
                                    int               addrcnt,
                                    __u16             flags)
{
      sctp_addip_param_t      param;
      struct sctp_chunk *retval;
      union sctp_addr_param   addr_param;
      union sctp_addr         *addr;
      void              *addr_buf;
      struct sctp_af          *af;
      int               paramlen = sizeof(param);
      int               addr_param_len = 0;
      int               totallen = 0;
      int               i;

      /* Get total length of all the address parameters. */
      addr_buf = addrs;
      for (i = 0; i < addrcnt; i++) {
            addr = (union sctp_addr *)addr_buf;
            af = sctp_get_af_specific(addr->v4.sin_family);
            addr_param_len = af->to_addr_param(addr, &addr_param);

            totallen += paramlen;
            totallen += addr_param_len;

            addr_buf += af->sockaddr_len;
      }

      /* Create an asconf chunk with the required length. */
      retval = sctp_make_asconf(asoc, laddr, totallen);
      if (!retval)
            return NULL;

      /* Add the address parameters to the asconf chunk. */
      addr_buf = addrs;
      for (i = 0; i < addrcnt; i++) {
            addr = (union sctp_addr *)addr_buf;
            af = sctp_get_af_specific(addr->v4.sin_family);
            addr_param_len = af->to_addr_param(addr, &addr_param);
            param.param_hdr.type = flags;
            param.param_hdr.length = htons(paramlen + addr_param_len);
            param.crr_id = i;

            sctp_addto_chunk(retval, paramlen, &param);
            sctp_addto_chunk(retval, addr_param_len, &addr_param);

            addr_buf += af->sockaddr_len;
      }
      return retval;
}

/* ADDIP
 * 3.2.4 Set Primary IP Address
 *    0                   1                   2                   3
 *    0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
 *     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 *     |        Type =0xC004           |    Length = Variable          |
 *     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 *     |               ASCONF-Request Correlation ID                   |
 *     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 *     |                       Address Parameter                       |
 *     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 *
 * Create an ASCONF chunk with Set Primary IP address parameter. 
 */
struct sctp_chunk *sctp_make_asconf_set_prim(struct sctp_association *asoc,
                                   union sctp_addr *addr)
{
      sctp_addip_param_t      param;
      struct sctp_chunk       *retval;
      int               len = sizeof(param);
      union sctp_addr_param   addrparam;
      int               addrlen;
      struct sctp_af          *af = sctp_get_af_specific(addr->v4.sin_family);

      addrlen = af->to_addr_param(addr, &addrparam);
      if (!addrlen)
            return NULL;
      len += addrlen;

      /* Create the chunk and make asconf header. */
      retval = sctp_make_asconf(asoc, addr, len);
      if (!retval)
            return NULL;

      param.param_hdr.type = SCTP_PARAM_SET_PRIMARY;
      param.param_hdr.length = htons(len);
      param.crr_id = 0;

      sctp_addto_chunk(retval, sizeof(param), &param);
      sctp_addto_chunk(retval, addrlen, &addrparam);

      return retval;
}

/* ADDIP 3.1.2 Address Configuration Acknowledgement Chunk (ASCONF-ACK)
 *      0                   1                   2                   3
 *      0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
 *     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 *     | Type = 0x80   |  Chunk Flags  |      Chunk Length             |
 *     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 *     |                       Serial Number                           |
 *     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 *     |                 ASCONF Parameter Response#1                   |
 *     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 *     \                                                               \
 *     /                             ....                              /
 *     \                                                               \
 *     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 *     |                 ASCONF Parameter Response#N                   |
 *     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 *
 * Create an ASCONF_ACK chunk with enough space for the parameter responses. 
 */
static struct sctp_chunk *sctp_make_asconf_ack(const struct sctp_association *asoc,
                                     __u32 serial, int vparam_len)
{
      sctp_addiphdr_t         asconf;
      struct sctp_chunk *retval;
      int               length = sizeof(asconf) + vparam_len;

      /* Create the chunk.  */
      retval = sctp_make_chunk(asoc, SCTP_CID_ASCONF_ACK, 0, length);
      if (!retval)
            return NULL;

      asconf.serial = htonl(serial);

      retval->subh.addip_hdr =
            sctp_addto_chunk(retval, sizeof(asconf), &asconf);

      return retval;
}

/* Add response parameters to an ASCONF_ACK chunk. */
static void sctp_add_asconf_response(struct sctp_chunk *chunk, __u32 crr_id,
                        __u16 err_code, sctp_addip_param_t *asconf_param)
{
      sctp_addip_param_t      ack_param;
      sctp_errhdr_t           err_param;
      int               asconf_param_len = 0;
      int               err_param_len = 0;
      __u16             response_type;

      if (SCTP_ERROR_NO_ERROR == err_code) {
            response_type = SCTP_PARAM_SUCCESS_REPORT;
      } else {
            response_type = SCTP_PARAM_ERR_CAUSE;
            err_param_len = sizeof(err_param);
            if (asconf_param)
                  asconf_param_len =
                         ntohs(asconf_param->param_hdr.length);
      }

      /* Add Success Indication or Error Cause Indication parameter. */ 
      ack_param.param_hdr.type = response_type;
      ack_param.param_hdr.length = htons(sizeof(ack_param) +
                                 err_param_len +
                                 asconf_param_len);
      ack_param.crr_id = crr_id;
      sctp_addto_chunk(chunk, sizeof(ack_param), &ack_param);

      if (SCTP_ERROR_NO_ERROR == err_code)
            return;

      /* Add Error Cause parameter. */
      err_param.cause = err_code;
      err_param.length = htons(err_param_len + asconf_param_len);
      sctp_addto_chunk(chunk, err_param_len, &err_param);

      /* Add the failed TLV copied from ASCONF chunk. */
      if (asconf_param)
            sctp_addto_chunk(chunk, asconf_param_len, asconf_param);
}

/* Process a asconf parameter. */
static __u16 sctp_process_asconf_param(struct sctp_association *asoc,
                               struct sctp_chunk *asconf,
                               sctp_addip_param_t *asconf_param)
{
      struct sctp_transport *peer;
      struct sctp_af *af;
      union sctp_addr   addr;
      struct list_head *pos;
      union sctp_addr_param *addr_param;
                         
      addr_param = (union sctp_addr_param *)
                  ((void *)asconf_param + sizeof(sctp_addip_param_t));

      af = sctp_get_af_specific(param_type2af(addr_param->v4.param_hdr.type));
      if (unlikely(!af))
            return SCTP_ERROR_INV_PARAM;

      af->from_addr_param(&addr, addr_param, asoc->peer.port, 0);
      switch (asconf_param->param_hdr.type) {
      case SCTP_PARAM_ADD_IP:
            /* ADDIP 4.3 D9) If an endpoint receives an ADD IP address
             * request and does not have the local resources to add this
             * new address to the association, it MUST return an Error
             * Cause TLV set to the new error code 'Operation Refused
             * Due to Resource Shortage'.
             */

            peer = sctp_assoc_add_peer(asoc, &addr, GFP_ATOMIC, SCTP_UNCONFIRMED);
            if (!peer)
                  return SCTP_ERROR_RSRC_LOW;

            /* Start the heartbeat timer. */
            if (!mod_timer(&peer->hb_timer, sctp_transport_timeout(peer)))
                  sctp_transport_hold(peer);
            break;
      case SCTP_PARAM_DEL_IP:
            /* ADDIP 4.3 D7) If a request is received to delete the
             * last remaining IP address of a peer endpoint, the receiver
             * MUST send an Error Cause TLV with the error cause set to the
             * new error code 'Request to Delete Last Remaining IP Address'.
             */
            pos = asoc->peer.transport_addr_list.next;
            if (pos->next == &asoc->peer.transport_addr_list)
                  return SCTP_ERROR_DEL_LAST_IP;

            /* ADDIP 4.3 D8) If a request is received to delete an IP
             * address which is also the source address of the IP packet
             * which contained the ASCONF chunk, the receiver MUST reject
             * this request. To reject the request the receiver MUST send
             * an Error Cause TLV set to the new error code 'Request to
             * Delete Source IP Address'
             */
            if (sctp_cmp_addr_exact(sctp_source(asconf), &addr))
                  return SCTP_ERROR_DEL_SRC_IP;

            sctp_assoc_del_peer(asoc, &addr);
            break;
      case SCTP_PARAM_SET_PRIMARY:
            peer = sctp_assoc_lookup_paddr(asoc, &addr);
            if (!peer)
                  return SCTP_ERROR_INV_PARAM;

            sctp_assoc_set_primary(asoc, peer);
            break;
      default:
            return SCTP_ERROR_INV_PARAM;
            break;
      }

      return SCTP_ERROR_NO_ERROR;
}

/* Process an incoming ASCONF chunk with the next expected serial no. and 
 * return an ASCONF_ACK chunk to be sent in response.
 */
struct sctp_chunk *sctp_process_asconf(struct sctp_association *asoc,
                               struct sctp_chunk *asconf)
{
      sctp_addiphdr_t         *hdr;
      union sctp_addr_param   *addr_param;
      sctp_addip_param_t      *asconf_param;
      struct sctp_chunk *asconf_ack;

      __u16 err_code;
      int   length = 0;
      int   chunk_len = asconf->skb->len;
      __u32 serial;
      int   all_param_pass = 1;

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

      /* Skip the addiphdr and store a pointer to address parameter.  */ 
      length = sizeof(sctp_addiphdr_t);
      addr_param = (union sctp_addr_param *)(asconf->skb->data + length);
      chunk_len -= length;

      /* Skip the address parameter and store a pointer to the first
       * asconf paramter.
       */ 
      length = ntohs(addr_param->v4.param_hdr.length);
      asconf_param = (sctp_addip_param_t *)((void *)addr_param + length);
      chunk_len -= length;

      /* create an ASCONF_ACK chunk. 
       * Based on the definitions of parameters, we know that the size of
       * ASCONF_ACK parameters are less than or equal to the twice of ASCONF
       * paramters.
       */
      asconf_ack = sctp_make_asconf_ack(asoc, serial, chunk_len * 2);
      if (!asconf_ack)
            goto done;

      /* Process the TLVs contained within the ASCONF chunk. */
      while (chunk_len > 0) {
            err_code = sctp_process_asconf_param(asoc, asconf,
                                         asconf_param);
            /* ADDIP 4.1 A7)
             * If an error response is received for a TLV parameter,
             * all TLVs with no response before the failed TLV are
             * considered successful if not reported.  All TLVs after
             * the failed response are considered unsuccessful unless
             * a specific success indication is present for the parameter.
             */
            if (SCTP_ERROR_NO_ERROR != err_code)
                  all_param_pass = 0;

            if (!all_param_pass)
                  sctp_add_asconf_response(asconf_ack,
                                     asconf_param->crr_id, err_code,
                                     asconf_param);

            /* ADDIP 4.3 D11) When an endpoint receiving an ASCONF to add
             * an IP address sends an 'Out of Resource' in its response, it
             * MUST also fail any subsequent add or delete requests bundled
             * in the ASCONF. 
             */
            if (SCTP_ERROR_RSRC_LOW == err_code)
                  goto done;

            /* Move to the next ASCONF param. */
            length = ntohs(asconf_param->param_hdr.length);
            asconf_param = (sctp_addip_param_t *)((void *)asconf_param +
                                          length);
            chunk_len -= length;
      }
      
done:
      asoc->peer.addip_serial++;

      /* If we are sending a new ASCONF_ACK hold a reference to it in assoc
       * after freeing the reference to old asconf ack if any. 
       */
      if (asconf_ack) {
            if (asoc->addip_last_asconf_ack)
                  sctp_chunk_free(asoc->addip_last_asconf_ack);

            sctp_chunk_hold(asconf_ack);
            asoc->addip_last_asconf_ack = asconf_ack;
      }

      return asconf_ack;
}

/* Process a asconf parameter that is successfully acked. */
static int sctp_asconf_param_success(struct sctp_association *asoc,
                             sctp_addip_param_t *asconf_param)
{
      struct sctp_af *af;
      union sctp_addr   addr;
      struct sctp_bind_addr *bp = &asoc->base.bind_addr;
      union sctp_addr_param *addr_param;
      struct list_head *pos;
      struct sctp_transport *transport;
      struct sctp_sockaddr_entry *saddr;
      int retval = 0;

      addr_param = (union sctp_addr_param *)
                  ((void *)asconf_param + sizeof(sctp_addip_param_t));

      /* We have checked the packet before, so we do not check again.   */
      af = sctp_get_af_specific(param_type2af(addr_param->v4.param_hdr.type));
      af->from_addr_param(&addr, addr_param, bp->port, 0);

      switch (asconf_param->param_hdr.type) {
      case SCTP_PARAM_ADD_IP:
            sctp_local_bh_disable();
            sctp_write_lock(&asoc->base.addr_lock);
            list_for_each(pos, &bp->address_list) {
                  saddr = list_entry(pos, struct sctp_sockaddr_entry, list);
                  if (sctp_cmp_addr_exact(&saddr->a, &addr))
                        saddr->use_as_src = 1;
            }
            sctp_write_unlock(&asoc->base.addr_lock);
            sctp_local_bh_enable();
            break;
      case SCTP_PARAM_DEL_IP:
            sctp_local_bh_disable();
            sctp_write_lock(&asoc->base.addr_lock);
            retval = sctp_del_bind_addr(bp, &addr);
            sctp_write_unlock(&asoc->base.addr_lock);
            sctp_local_bh_enable();
            list_for_each(pos, &asoc->peer.transport_addr_list) {
                  transport = list_entry(pos, struct sctp_transport,
                                     transports);
                  dst_release(transport->dst);
                  sctp_transport_route(transport, NULL,
                                   sctp_sk(asoc->base.sk));
            }
            break;
      default:
            break;
      }

      return retval;
}

/* Get the corresponding ASCONF response error code from the ASCONF_ACK chunk
 * for the given asconf parameter.  If there is no response for this parameter,
 * return the error code based on the third argument 'no_err'. 
 * ADDIP 4.1
 * A7) If an error response is received for a TLV parameter, all TLVs with no
 * response before the failed TLV are considered successful if not reported.
 * All TLVs after the failed response are considered unsuccessful unless a
 * specific success indication is present for the parameter.
 */
static __u16 sctp_get_asconf_response(struct sctp_chunk *asconf_ack,
                              sctp_addip_param_t *asconf_param,
                              int no_err)
{
      sctp_addip_param_t      *asconf_ack_param;
      sctp_errhdr_t           *err_param;
      int               length;
      int               asconf_ack_len = asconf_ack->skb->len;
      __u16             err_code;

      if (no_err)
            err_code = SCTP_ERROR_NO_ERROR;
      else
            err_code = SCTP_ERROR_REQ_REFUSED;

      /* Skip the addiphdr from the asconf_ack chunk and store a pointer to
       * the first asconf_ack parameter.
       */ 
      length = sizeof(sctp_addiphdr_t);
      asconf_ack_param = (sctp_addip_param_t *)(asconf_ack->skb->data +
                                      length);
      asconf_ack_len -= length;

      while (asconf_ack_len > 0) {
            if (asconf_ack_param->crr_id == asconf_param->crr_id) {
                  switch(asconf_ack_param->param_hdr.type) {
                  case SCTP_PARAM_SUCCESS_REPORT:
                        return SCTP_ERROR_NO_ERROR;
                  case SCTP_PARAM_ERR_CAUSE:
                        length = sizeof(sctp_addip_param_t);
                        err_param = (sctp_errhdr_t *)
                                 ((void *)asconf_ack_param + length);
                        asconf_ack_len -= length;
                        if (asconf_ack_len > 0)
                              return err_param->cause;
                        else
                              return SCTP_ERROR_INV_PARAM;
                        break;
                  default:
                        return SCTP_ERROR_INV_PARAM;
                  }
            }

            length = ntohs(asconf_ack_param->param_hdr.length);
            asconf_ack_param = (sctp_addip_param_t *)
                              ((void *)asconf_ack_param + length);
            asconf_ack_len -= length;
      }

      return err_code;
}

/* Process an incoming ASCONF_ACK chunk against the cached last ASCONF chunk. */
int sctp_process_asconf_ack(struct sctp_association *asoc,
                      struct sctp_chunk *asconf_ack)
{
      struct sctp_chunk *asconf = asoc->addip_last_asconf;
      union sctp_addr_param   *addr_param;
      sctp_addip_param_t      *asconf_param;
      int   length = 0;
      int   asconf_len = asconf->skb->len;
      int   all_param_pass = 0;
      int   no_err = 1;
      int   retval = 0;
      __u16 err_code = SCTP_ERROR_NO_ERROR;

      /* Skip the chunkhdr and addiphdr from the last asconf sent and store
       * a pointer to address parameter.
       */ 
      length = sizeof(sctp_addip_chunk_t);
      addr_param = (union sctp_addr_param *)(asconf->skb->data + length);
      asconf_len -= length;

      /* Skip the address parameter in the last asconf sent and store a
       * pointer to the first asconf paramter.
       */ 
      length = ntohs(addr_param->v4.param_hdr.length);
      asconf_param = (sctp_addip_param_t *)((void *)addr_param + length);
      asconf_len -= length;

      /* ADDIP 4.1
       * A8) If there is no response(s) to specific TLV parameter(s), and no
       * failures are indicated, then all request(s) are considered
       * successful.
       */
      if (asconf_ack->skb->len == sizeof(sctp_addiphdr_t))
            all_param_pass = 1;

      /* Process the TLVs contained in the last sent ASCONF chunk. */
      while (asconf_len > 0) {
            if (all_param_pass)
                  err_code = SCTP_ERROR_NO_ERROR;
            else {
                  err_code = sctp_get_asconf_response(asconf_ack,
                                              asconf_param,
                                              no_err);
                  if (no_err && (SCTP_ERROR_NO_ERROR != err_code))
                        no_err = 0;
            }

            switch (err_code) {
            case SCTP_ERROR_NO_ERROR:
                  retval = sctp_asconf_param_success(asoc, asconf_param);
                  break;

            case SCTP_ERROR_RSRC_LOW:
                  retval = 1;
                  break;

            case SCTP_ERROR_INV_PARAM:
                  /* Disable sending this type of asconf parameter in
                   * future.
                   */   
                  asoc->peer.addip_disabled_mask |=
                        asconf_param->param_hdr.type;
                  break;

            case SCTP_ERROR_REQ_REFUSED:
            case SCTP_ERROR_DEL_LAST_IP:
            case SCTP_ERROR_DEL_SRC_IP:
            default:
                   break;
            }

            /* Skip the processed asconf parameter and move to the next
             * one.
             */ 
            length = ntohs(asconf_param->param_hdr.length);
            asconf_param = (sctp_addip_param_t *)((void *)asconf_param +
                                          length);
            asconf_len -= length;
      }

      /* Free the cached last sent asconf chunk. */
      sctp_chunk_free(asconf);
      asoc->addip_last_asconf = NULL;

      /* Send the next asconf chunk from the addip chunk queue. */
      if (!list_empty(&asoc->addip_chunk_list)) {
            struct list_head *entry = asoc->addip_chunk_list.next;
            asconf = list_entry(entry, struct sctp_chunk, list);

            list_del_init(entry);

            /* Hold the chunk until an ASCONF_ACK is received. */
            sctp_chunk_hold(asconf);
            if (sctp_primitive_ASCONF(asoc, asconf))
                  sctp_chunk_free(asconf);
            else
                  asoc->addip_last_asconf = asconf;
      }

      return retval;
}

/* Make a FWD TSN chunk. */ 
struct sctp_chunk *sctp_make_fwdtsn(const struct sctp_association *asoc,
                            __u32 new_cum_tsn, size_t nstreams,
                            struct sctp_fwdtsn_skip *skiplist)
{
      struct sctp_chunk *retval = NULL;
      struct sctp_fwdtsn_chunk *ftsn_chunk;
      struct sctp_fwdtsn_hdr ftsn_hdr; 
      struct sctp_fwdtsn_skip skip;
      size_t hint;
      int i;

      hint = (nstreams + 1) * sizeof(__u32);

      retval = sctp_make_chunk(asoc, SCTP_CID_FWD_TSN, 0, hint);

      if (!retval)
            return NULL;

      ftsn_chunk = (struct sctp_fwdtsn_chunk *)retval->subh.fwdtsn_hdr;

      ftsn_hdr.new_cum_tsn = htonl(new_cum_tsn);
      retval->subh.fwdtsn_hdr =
            sctp_addto_chunk(retval, sizeof(ftsn_hdr), &ftsn_hdr);

      for (i = 0; i < nstreams; i++) {
            skip.stream = skiplist[i].stream;
            skip.ssn = skiplist[i].ssn;
            sctp_addto_chunk(retval, sizeof(skip), &skip);
      }

      return retval;
}

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