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strip.c

/*
 * Copyright 1996 The Board of Trustees of The Leland Stanford
 * Junior University. All Rights Reserved.
 *
 * Permission to use, copy, modify, and distribute this
 * software and its documentation for any purpose and without
 * fee is hereby granted, provided that the above copyright
 * notice appear in all copies.  Stanford University
 * makes no representations about the suitability of this
 * software for any purpose.  It is provided "as is" without
 * express or implied warranty.
 *
 * strip.c  This module implements Starmode Radio IP (STRIP)
 *          for kernel-based devices like TTY.  It interfaces between a
 *          raw TTY, and the kernel's INET protocol layers (via DDI).
 *
 * Version: @(#)strip.c 1.3   July 1997
 *
 * Author:  Stuart Cheshire <cheshire@cs.stanford.edu>
 *
 * Fixes:   v0.9 12th Feb 1996 (SC)
 *          New byte stuffing (2+6 run-length encoding)
 *          New watchdog timer task
 *          New Protocol key (SIP0)
 *          
 *          v0.9.1 3rd March 1996 (SC)
 *          Changed to dynamic device allocation -- no more compile
 *          time (or boot time) limit on the number of STRIP devices.
 *          
 *          v0.9.2 13th March 1996 (SC)
 *          Uses arp cache lookups (but doesn't send arp packets yet)
 *          
 *          v0.9.3 17th April 1996 (SC)
 *          Fixed bug where STR_ERROR flag was getting set unneccessarily
 *          (causing otherwise good packets to be unneccessarily dropped)
 *          
 *          v0.9.4 27th April 1996 (SC)
 *          First attempt at using "&COMMAND" Starmode AT commands
 *          
 *          v0.9.5 29th May 1996 (SC)
 *          First attempt at sending (unicast) ARP packets
 *          
 *          v0.9.6 5th June 1996 (Elliot)
 *          Put "message level" tags in every "printk" statement
 *          
 *          v0.9.7 13th June 1996 (laik)
 *          Added support for the /proc fs
 *
 *              v0.9.8 July 1996 (Mema)
 *              Added packet logging
 *
 *              v1.0 November 1996 (SC)
 *              Fixed (severe) memory leaks in the /proc fs code
 *              Fixed race conditions in the logging code
 *
 *              v1.1 January 1997 (SC)
 *              Deleted packet logging (use tcpdump instead)
 *              Added support for Metricom Firmware v204 features
 *              (like message checksums)
 *
 *              v1.2 January 1997 (SC)
 *              Put portables list back in
 *
 *              v1.3 July 1997 (SC)
 *              Made STRIP driver set the radio's baud rate automatically.
 *              It is no longer necessarily to manually set the radio's
 *              rate permanently to 115200 -- the driver handles setting
 *              the rate automatically.
 */

#ifdef MODULE
static const char StripVersion[] = "1.3A-STUART.CHESHIRE-MODULAR";
#else
static const char StripVersion[] = "1.3A-STUART.CHESHIRE";
#endif

#define TICKLE_TIMERS 0
#define EXT_COUNTERS 1


/************************************************************************/
/* Header files                                             */

#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/init.h>
#include <linux/bitops.h>
#include <asm/system.h>
#include <asm/uaccess.h>

# include <linux/ctype.h>
#include <linux/string.h>
#include <linux/mm.h>
#include <linux/interrupt.h>
#include <linux/in.h>
#include <linux/tty.h>
#include <linux/errno.h>
#include <linux/netdevice.h>
#include <linux/inetdevice.h>
#include <linux/etherdevice.h>
#include <linux/skbuff.h>
#include <linux/if_arp.h>
#include <linux/if_strip.h>
#include <linux/proc_fs.h>
#include <linux/seq_file.h>
#include <linux/serial.h>
#include <linux/serialP.h>
#include <linux/rcupdate.h>
#include <net/arp.h>

#include <linux/ip.h>
#include <linux/tcp.h>
#include <linux/time.h>
#include <linux/jiffies.h>

/************************************************************************/
/* Useful structures and definitions                              */

/*
 * A MetricomKey identifies the protocol being carried inside a Metricom
 * Starmode packet.
 */

typedef union {
      __u8 c[4];
      __u32 l;
} MetricomKey;

/*
 * An IP address can be viewed as four bytes in memory (which is what it is) or as
 * a single 32-bit long (which is convenient for assignment, equality testing etc.)
 */

typedef union {
      __u8 b[4];
      __u32 l;
} IPaddr;

/*
 * A MetricomAddressString is used to hold a printable representation of
 * a Metricom address.
 */

typedef struct {
      __u8 c[24];
} MetricomAddressString;

/* Encapsulation can expand packet of size x to 65/64x + 1
 * Sent packet looks like "<CR>*<address>*<key><encaps payload><CR>"
 *                           1 1   1-18  1  4         ?         1
 * eg.                     <CR>*0000-1234*SIP0<encaps payload><CR>
 * We allow 31 bytes for the stars, the key, the address and the <CR>s
 */
#define STRIP_ENCAP_SIZE(X) (32 + (X)*65L/64L)

/*
 * A STRIP_Header is never really sent over the radio, but making a dummy
 * header for internal use within the kernel that looks like an Ethernet
 * header makes certain other software happier. For example, tcpdump
 * already understands Ethernet headers.
 */

typedef struct {
      MetricomAddress dst_addr;     /* Destination address, e.g. "0000-1234"   */
      MetricomAddress src_addr;     /* Source address, e.g. "0000-5678"        */
      unsigned short protocol;      /* The protocol type, using Ethernet codes */
} STRIP_Header;

typedef struct {
      char c[60];
} MetricomNode;

#define NODE_TABLE_SIZE 32
typedef struct {
      struct timeval timestamp;
      int num_nodes;
      MetricomNode node[NODE_TABLE_SIZE];
} MetricomNodeTable;

enum { FALSE = 0, TRUE = 1 };

/*
 * Holds the radio's firmware version.
 */
typedef struct {
      char c[50];
} FirmwareVersion;

/*
 * Holds the radio's serial number.
 */
typedef struct {
      char c[18];
} SerialNumber;

/*
 * Holds the radio's battery voltage.
 */
typedef struct {
      char c[11];
} BatteryVoltage;

typedef struct {
      char c[8];
} char8;

enum {
      NoStructure = 0,  /* Really old firmware */
      StructuredMessages = 1, /* Parsable AT response msgs */
      ChecksummedMessages = 2 /* Parsable AT response msgs with checksums */
};

struct strip {
      int magic;
      /*
       * These are pointers to the malloc()ed frame buffers.
       */

      unsigned char *rx_buff; /* buffer for received IP packet */
      unsigned char *sx_buff; /* buffer for received serial data */
      int sx_count;           /* received serial data counter */
      int sx_size;            /* Serial buffer size           */
      unsigned char *tx_buff; /* transmitter buffer           */
      unsigned char *tx_head; /* pointer to next byte to XMIT */
      int tx_left;            /* bytes left in XMIT queue     */
      int tx_size;            /* Serial buffer size           */

      /*
       * STRIP interface statistics.
       */

      unsigned long rx_packets;     /* inbound frames counter       */
      unsigned long tx_packets;     /* outbound frames counter      */
      unsigned long rx_errors;      /* Parity, etc. errors          */
      unsigned long tx_errors;      /* Planned stuff                */
      unsigned long rx_dropped;     /* No memory for skb            */
      unsigned long tx_dropped;     /* When MTU change              */
      unsigned long rx_over_errors; /* Frame bigger then STRIP buf. */

      unsigned long pps_timer;      /* Timer to determine pps       */
      unsigned long rx_pps_count;   /* Counter to determine pps     */
      unsigned long tx_pps_count;   /* Counter to determine pps     */
      unsigned long sx_pps_count;   /* Counter to determine pps     */
      unsigned long rx_average_pps; /* rx packets per second * 8    */
      unsigned long tx_average_pps; /* tx packets per second * 8    */
      unsigned long sx_average_pps; /* sent packets per second * 8  */

#ifdef EXT_COUNTERS
      unsigned long rx_bytes;       /* total received bytes */
      unsigned long tx_bytes;       /* total received bytes */
      unsigned long rx_rbytes;      /* bytes thru radio i/f */
      unsigned long tx_rbytes;      /* bytes thru radio i/f */
      unsigned long rx_sbytes;      /* tot bytes thru serial i/f */
      unsigned long tx_sbytes;      /* tot bytes thru serial i/f */
      unsigned long rx_ebytes;      /* tot stat/err bytes */
      unsigned long tx_ebytes;      /* tot stat/err bytes */
#endif

      /*
       * Internal variables.
       */

      struct list_head  list;       /* Linked list of devices */

      int discard;                  /* Set if serial error          */
      int working;                  /* Is radio working correctly?  */
      int firmware_level;           /* Message structuring level    */
      int next_command;       /* Next periodic command        */
      unsigned int user_baud;       /* The user-selected baud rate  */
      int mtu;                /* Our mtu (to spot changes!)   */
      long watchdog_doprobe;        /* Next time to test the radio  */
      long watchdog_doreset;        /* Time to do next reset        */
      long gratuitous_arp;          /* Time to send next ARP refresh */
      long arp_interval;            /* Next ARP interval            */
      struct timer_list idle_timer; /* For periodic wakeup calls    */
      MetricomAddress true_dev_addr;      /* True address of radio        */
      int manual_dev_addr;          /* Hack: See note below         */

      FirmwareVersion firmware_version;   /* The radio's firmware version */
      SerialNumber serial_number;   /* The radio's serial number    */
      BatteryVoltage battery_voltage;     /* The radio's battery voltage  */

      /*
       * Other useful structures.
       */

      struct tty_struct *tty;       /* ptr to TTY structure         */
      struct net_device *dev;       /* Our device structure         */

      /*
       * Neighbour radio records
       */

      MetricomNodeTable portables;
      MetricomNodeTable poletops;
};

/*
 * Note: manual_dev_addr hack
 * 
 * It is not possible to change the hardware address of a Metricom radio,
 * or to send packets with a user-specified hardware source address, thus
 * trying to manually set a hardware source address is a questionable
 * thing to do.  However, if the user *does* manually set the hardware
 * source address of a STRIP interface, then the kernel will believe it,
 * and use it in certain places. For example, the hardware address listed
 * by ifconfig will be the manual address, not the true one.
 * (Both addresses are listed in /proc/net/strip.)
 * Also, ARP packets will be sent out giving the user-specified address as
 * the source address, not the real address. This is dangerous, because
 * it means you won't receive any replies -- the ARP replies will go to
 * the specified address, which will be some other radio. The case where
 * this is useful is when that other radio is also connected to the same
 * machine. This allows you to connect a pair of radios to one machine,
 * and to use one exclusively for inbound traffic, and the other
 * exclusively for outbound traffic. Pretty neat, huh?
 * 
 * Here's the full procedure to set this up:
 * 
 * 1. "slattach" two interfaces, e.g. st0 for outgoing packets,
 *    and st1 for incoming packets
 * 
 * 2. "ifconfig" st0 (outbound radio) to have the hardware address
 *    which is the real hardware address of st1 (inbound radio).
 *    Now when it sends out packets, it will masquerade as st1, and
 *    replies will be sent to that radio, which is exactly what we want.
 * 
 * 3. Set the route table entry ("route add default ..." or
 *    "route add -net ...", as appropriate) to send packets via the st0
 *    interface (outbound radio). Do not add any route which sends packets
 *    out via the st1 interface -- that radio is for inbound traffic only.
 * 
 * 4. "ifconfig" st1 (inbound radio) to have hardware address zero.
 *    This tells the STRIP driver to "shut down" that interface and not
 *    send any packets through it. In particular, it stops sending the
 *    periodic gratuitous ARP packets that a STRIP interface normally sends.
 *    Also, when packets arrive on that interface, it will search the
 *    interface list to see if there is another interface who's manual
 *    hardware address matches its own real address (i.e. st0 in this
 *    example) and if so it will transfer ownership of the skbuff to
 *    that interface, so that it looks to the kernel as if the packet
 *    arrived on that interface. This is necessary because when the
 *    kernel sends an ARP packet on st0, it expects to get a reply on
 *    st0, and if it sees the reply come from st1 then it will ignore
 *    it (to be accurate, it puts the entry in the ARP table, but
 *    labelled in such a way that st0 can't use it).
 * 
 * Thanks to Petros Maniatis for coming up with the idea of splitting
 * inbound and outbound traffic between two interfaces, which turned
 * out to be really easy to implement, even if it is a bit of a hack.
 * 
 * Having set a manual address on an interface, you can restore it
 * to automatic operation (where the address is automatically kept
 * consistent with the real address of the radio) by setting a manual
 * address of all ones, e.g. "ifconfig st0 hw strip FFFFFFFFFFFF"
 * This 'turns off' manual override mode for the device address.
 * 
 * Note: The IEEE 802 headers reported in tcpdump will show the *real*
 * radio addresses the packets were sent and received from, so that you
 * can see what is really going on with packets, and which interfaces
 * they are really going through.
 */


/************************************************************************/
/* Constants                                                */

/*
 * CommandString1 works on all radios
 * Other CommandStrings are only used with firmware that provides structured responses.
 * 
 * ats319=1 Enables Info message for node additions and deletions
 * ats319=2 Enables Info message for a new best node
 * ats319=4 Enables checksums
 * ats319=8 Enables ACK messages
 */

static const int MaxCommandStringLength = 32;
static const int CompatibilityCommand = 1;

static const char CommandString0[] = "*&COMMAND*ATS319=7";  /* Turn on checksums & info messages */
static const char CommandString1[] = "*&COMMAND*ATS305?";   /* Query radio name */
static const char CommandString2[] = "*&COMMAND*ATS325?";   /* Query battery voltage */
static const char CommandString3[] = "*&COMMAND*ATS300?";   /* Query version information */
static const char CommandString4[] = "*&COMMAND*ATS311?";   /* Query poletop list */
static const char CommandString5[] = "*&COMMAND*AT~LA";           /* Query portables list */
typedef struct {
      const char *string;
      long length;
} StringDescriptor;

static const StringDescriptor CommandString[] = {
      {CommandString0, sizeof(CommandString0) - 1},
      {CommandString1, sizeof(CommandString1) - 1},
      {CommandString2, sizeof(CommandString2) - 1},
      {CommandString3, sizeof(CommandString3) - 1},
      {CommandString4, sizeof(CommandString4) - 1},
      {CommandString5, sizeof(CommandString5) - 1}
};

#define GOT_ALL_RADIO_INFO(S)      \
    ((S)->firmware_version.c[0] && \
     (S)->battery_voltage.c[0]  && \
     memcmp(&(S)->true_dev_addr, zero_address.c, sizeof(zero_address)))

static const char hextable[16] = "0123456789ABCDEF";

static const MetricomAddress zero_address;
static const MetricomAddress broadcast_address =
    { {0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF} };

static const MetricomKey SIP0Key = { "SIP0" };
static const MetricomKey ARP0Key = { "ARP0" };
static const MetricomKey ATR_Key = { "ATR " };
static const MetricomKey ACK_Key = { "ACK_" };
static const MetricomKey INF_Key = { "INF_" };
static const MetricomKey ERR_Key = { "ERR_" };

static const long MaxARPInterval = 60 * HZ;     /* One minute */

/*
 * Maximum Starmode packet length is 1183 bytes. Allowing 4 bytes for
 * protocol key, 4 bytes for checksum, one byte for CR, and 65/64 expansion
 * for STRIP encoding, that translates to a maximum payload MTU of 1155.
 * Note: A standard NFS 1K data packet is a total of 0x480 (1152) bytes
 * long, including IP header, UDP header, and NFS header. Setting the STRIP
 * MTU to 1152 allows us to send default sized NFS packets without fragmentation.
 */
static const unsigned short MAX_SEND_MTU = 1152;
static const unsigned short MAX_RECV_MTU = 1500;      /* Hoping for Ethernet sized packets in the future! */
static const unsigned short DEFAULT_STRIP_MTU = 1152;
static const int STRIP_MAGIC = 0x5303;
static const long LongTime = 0x7FFFFFFF;

/************************************************************************/
/* Global variables                                         */

static LIST_HEAD(strip_list);
static DEFINE_SPINLOCK(strip_lock);

/************************************************************************/
/* Macros                                             */

/* Returns TRUE if text T begins with prefix P */
#define has_prefix(T,L,P) (((L) >= sizeof(P)-1) && !strncmp((T), (P), sizeof(P)-1))

/* Returns TRUE if text T of length L is equal to string S */
#define text_equal(T,L,S) (((L) == sizeof(S)-1) && !strncmp((T), (S), sizeof(S)-1))

#define READHEX(X) ((X)>='0' && (X)<='9' ? (X)-'0' :      \
                    (X)>='a' && (X)<='f' ? (X)-'a'+10 :   \
                    (X)>='A' && (X)<='F' ? (X)-'A'+10 : 0 )

#define READHEX16(X) ((__u16)(READHEX(X)))

#define READDEC(X) ((X)>='0' && (X)<='9' ? (X)-'0' : 0)

#define ARRAY_END(X) (&((X)[ARRAY_SIZE(X)]))

#define JIFFIE_TO_SEC(X) ((X) / HZ)


/************************************************************************/
/* Utility routines                                         */

static int arp_query(unsigned char *haddr, u32 paddr,
                 struct net_device *dev)
{
      struct neighbour *neighbor_entry;
      int ret = 0;

      neighbor_entry = neigh_lookup(&arp_tbl, &paddr, dev);

      if (neighbor_entry != NULL) {
            neighbor_entry->used = jiffies;
            if (neighbor_entry->nud_state & NUD_VALID) {
                  memcpy(haddr, neighbor_entry->ha, dev->addr_len);
                  ret = 1;
            }
            neigh_release(neighbor_entry);
      }
      return ret;
}

static void DumpData(char *msg, struct strip *strip_info, __u8 * ptr,
                 __u8 * end)
{
      static const int MAX_DumpData = 80;
      __u8 pkt_text[MAX_DumpData], *p = pkt_text;

      *p++ = '\"';

      while (ptr < end && p < &pkt_text[MAX_DumpData - 4]) {
            if (*ptr == '\\') {
                  *p++ = '\\';
                  *p++ = '\\';
            } else {
                  if (*ptr >= 32 && *ptr <= 126) {
                        *p++ = *ptr;
                  } else {
                        sprintf(p, "\\%02X", *ptr);
                        p += 3;
                  }
            }
            ptr++;
      }

      if (ptr == end)
            *p++ = '\"';
      *p++ = 0;

      printk(KERN_INFO "%s: %-13s%s\n", strip_info->dev->name, msg, pkt_text);
}


/************************************************************************/
/* Byte stuffing/unstuffing routines                              */

/* Stuffing scheme:
 * 00    Unused (reserved character)
 * 01-3F Run of 2-64 different characters
 * 40-7F Run of 1-64 different characters plus a single zero at the end
 * 80-BF Run of 1-64 of the same character
 * C0-FF Run of 1-64 zeroes (ASCII 0)
 */

typedef enum {
      Stuff_Diff = 0x00,
      Stuff_DiffZero = 0x40,
      Stuff_Same = 0x80,
      Stuff_Zero = 0xC0,
      Stuff_NoCode = 0xFF,    /* Special code, meaning no code selected */

      Stuff_CodeMask = 0xC0,
      Stuff_CountMask = 0x3F,
      Stuff_MaxCount = 0x3F,
      Stuff_Magic = 0x0D      /* The value we are eliminating */
} StuffingCode;

/* StuffData encodes the data starting at "src" for "length" bytes.
 * It writes it to the buffer pointed to by "dst" (which must be at least
 * as long as 1 + 65/64 of the input length). The output may be up to 1.6%
 * larger than the input for pathological input, but will usually be smaller.
 * StuffData returns the new value of the dst pointer as its result.
 * "code_ptr_ptr" points to a "__u8 *" which is used to hold encoding state
 * between calls, allowing an encoded packet to be incrementally built up
 * from small parts. On the first call, the "__u8 *" pointed to should be
 * initialized to NULL; between subsequent calls the calling routine should
 * leave the value alone and simply pass it back unchanged so that the
 * encoder can recover its current state.
 */

#define StuffData_FinishBlock(X) \
(*code_ptr = (X) ^ Stuff_Magic, code = Stuff_NoCode)

static __u8 *StuffData(__u8 * src, __u32 length, __u8 * dst,
                   __u8 ** code_ptr_ptr)
{
      __u8 *end = src + length;
      __u8 *code_ptr = *code_ptr_ptr;
      __u8 code = Stuff_NoCode, count = 0;

      if (!length)
            return (dst);

      if (code_ptr) {
            /*
             * Recover state from last call, if applicable
             */
            code = (*code_ptr ^ Stuff_Magic) & Stuff_CodeMask;
            count = (*code_ptr ^ Stuff_Magic) & Stuff_CountMask;
      }

      while (src < end) {
            switch (code) {
                  /* Stuff_NoCode: If no current code, select one */
            case Stuff_NoCode:
                  /* Record where we're going to put this code */
                  code_ptr = dst++;
                  count = 0;  /* Reset the count (zero means one instance) */
                  /* Tentatively start a new block */
                  if (*src == 0) {
                        code = Stuff_Zero;
                        src++;
                  } else {
                        code = Stuff_Same;
                        *dst++ = *src++ ^ Stuff_Magic;
                  }
                  /* Note: We optimistically assume run of same -- */
                  /* which will be fixed later in Stuff_Same */
                  /* if it turns out not to be true. */
                  break;

                  /* Stuff_Zero: We already have at least one zero encoded */
            case Stuff_Zero:
                  /* If another zero, count it, else finish this code block */
                  if (*src == 0) {
                        count++;
                        src++;
                  } else {
                        StuffData_FinishBlock(Stuff_Zero + count);
                  }
                  break;

                  /* Stuff_Same: We already have at least one byte encoded */
            case Stuff_Same:
                  /* If another one the same, count it */
                  if ((*src ^ Stuff_Magic) == code_ptr[1]) {
                        count++;
                        src++;
                        break;
                  }
                  /* else, this byte does not match this block. */
                  /* If we already have two or more bytes encoded, finish this code block */
                  if (count) {
                        StuffData_FinishBlock(Stuff_Same + count);
                        break;
                  }
                  /* else, we only have one so far, so switch to Stuff_Diff code */
                  code = Stuff_Diff;
                  /* and fall through to Stuff_Diff case below
                   * Note cunning cleverness here: case Stuff_Diff compares 
                   * the current character with the previous two to see if it
                   * has a run of three the same. Won't this be an error if
                   * there aren't two previous characters stored to compare with?
                   * No. Because we know the current character is *not* the same
                   * as the previous one, the first test below will necessarily
                   * fail and the send half of the "if" won't be executed.
                   */

                  /* Stuff_Diff: We have at least two *different* bytes encoded */
            case Stuff_Diff:
                  /* If this is a zero, must encode a Stuff_DiffZero, and begin a new block */
                  if (*src == 0) {
                        StuffData_FinishBlock(Stuff_DiffZero +
                                          count);
                  }
                  /* else, if we have three in a row, it is worth starting a Stuff_Same block */
                  else if ((*src ^ Stuff_Magic) == dst[-1]
                         && dst[-1] == dst[-2]) {
                        /* Back off the last two characters we encoded */
                        code += count - 2;
                        /* Note: "Stuff_Diff + 0" is an illegal code */
                        if (code == Stuff_Diff + 0) {
                              code = Stuff_Same + 0;
                        }
                        StuffData_FinishBlock(code);
                        code_ptr = dst - 2;
                        /* dst[-1] already holds the correct value */
                        count = 2;  /* 2 means three bytes encoded */
                        code = Stuff_Same;
                  }
                  /* else, another different byte, so add it to the block */
                  else {
                        *dst++ = *src ^ Stuff_Magic;
                        count++;
                  }
                  src++;      /* Consume the byte */
                  break;
            }
            if (count == Stuff_MaxCount) {
                  StuffData_FinishBlock(code + count);
            }
      }
      if (code == Stuff_NoCode) {
            *code_ptr_ptr = NULL;
      } else {
            *code_ptr_ptr = code_ptr;
            StuffData_FinishBlock(code + count);
      }
      return (dst);
}

/*
 * UnStuffData decodes the data at "src", up to (but not including) "end".
 * It writes the decoded data into the buffer pointed to by "dst", up to a
 * maximum of "dst_length", and returns the new value of "src" so that a
 * follow-on call can read more data, continuing from where the first left off.
 * 
 * There are three types of results:
 * 1. The source data runs out before extracting "dst_length" bytes:
 *    UnStuffData returns NULL to indicate failure.
 * 2. The source data produces exactly "dst_length" bytes:
 *    UnStuffData returns new_src = end to indicate that all bytes were consumed.
 * 3. "dst_length" bytes are extracted, with more remaining.
 *    UnStuffData returns new_src < end to indicate that there are more bytes
 *    to be read.
 * 
 * Note: The decoding may be destructive, in that it may alter the source
 * data in the process of decoding it (this is necessary to allow a follow-on
 * call to resume correctly).
 */

static __u8 *UnStuffData(__u8 * src, __u8 * end, __u8 * dst,
                   __u32 dst_length)
{
      __u8 *dst_end = dst + dst_length;
      /* Sanity check */
      if (!src || !end || !dst || !dst_length)
            return (NULL);
      while (src < end && dst < dst_end) {
            int count = (*src ^ Stuff_Magic) & Stuff_CountMask;
            switch ((*src ^ Stuff_Magic) & Stuff_CodeMask) {
            case Stuff_Diff:
                  if (src + 1 + count >= end)
                        return (NULL);
                  do {
                        *dst++ = *++src ^ Stuff_Magic;
                  }
                  while (--count >= 0 && dst < dst_end);
                  if (count < 0)
                        src += 1;
                  else {
                        if (count == 0)
                              *src = Stuff_Same ^ Stuff_Magic;
                        else
                              *src =
                                  (Stuff_Diff +
                                   count) ^ Stuff_Magic;
                  }
                  break;
            case Stuff_DiffZero:
                  if (src + 1 + count >= end)
                        return (NULL);
                  do {
                        *dst++ = *++src ^ Stuff_Magic;
                  }
                  while (--count >= 0 && dst < dst_end);
                  if (count < 0)
                        *src = Stuff_Zero ^ Stuff_Magic;
                  else
                        *src =
                            (Stuff_DiffZero + count) ^ Stuff_Magic;
                  break;
            case Stuff_Same:
                  if (src + 1 >= end)
                        return (NULL);
                  do {
                        *dst++ = src[1] ^ Stuff_Magic;
                  }
                  while (--count >= 0 && dst < dst_end);
                  if (count < 0)
                        src += 2;
                  else
                        *src = (Stuff_Same + count) ^ Stuff_Magic;
                  break;
            case Stuff_Zero:
                  do {
                        *dst++ = 0;
                  }
                  while (--count >= 0 && dst < dst_end);
                  if (count < 0)
                        src += 1;
                  else
                        *src = (Stuff_Zero + count) ^ Stuff_Magic;
                  break;
            }
      }
      if (dst < dst_end)
            return (NULL);
      else
            return (src);
}


/************************************************************************/
/* General routines for STRIP                               */

/*
 * get_baud returns the current baud rate, as one of the constants defined in
 * termbits.h
 * If the user has issued a baud rate override using the 'setserial' command
 * and the logical current rate is set to 38.4, then the true baud rate
 * currently in effect (57.6 or 115.2) is returned.
 */
static unsigned int get_baud(struct tty_struct *tty)
{
      if (!tty || !tty->termios)
            return (0);
      if ((tty->termios->c_cflag & CBAUD) == B38400 && tty->driver_data) {
            struct async_struct *info =
                (struct async_struct *) tty->driver_data;
            if ((info->flags & ASYNC_SPD_MASK) == ASYNC_SPD_HI)
                  return (B57600);
            if ((info->flags & ASYNC_SPD_MASK) == ASYNC_SPD_VHI)
                  return (B115200);
      }
      return (tty->termios->c_cflag & CBAUD);
}

/*
 * set_baud sets the baud rate to the rate defined by baudcode
 * Note: The rate B38400 should be avoided, because the user may have
 * issued a 'setserial' speed override to map that to a different speed.
 * We could achieve a true rate of 38400 if we needed to by cancelling
 * any user speed override that is in place, but that might annoy the
 * user, so it is simplest to just avoid using 38400.
 */
static void set_baud(struct tty_struct *tty, unsigned int baudcode)
{
      struct termios old_termios = *(tty->termios);
      tty->termios->c_cflag &= ~CBAUD;    /* Clear the old baud setting */
      tty->termios->c_cflag |= baudcode;  /* Set the new baud setting */
      tty->driver->set_termios(tty, &old_termios);
}

/*
 * Convert a string to a Metricom Address.
 */

#define IS_RADIO_ADDRESS(p) (                                                 \
  isdigit((p)[0]) && isdigit((p)[1]) && isdigit((p)[2]) && isdigit((p)[3]) && \
  (p)[4] == '-' &&                                                            \
  isdigit((p)[5]) && isdigit((p)[6]) && isdigit((p)[7]) && isdigit((p)[8])    )

static int string_to_radio_address(MetricomAddress * addr, __u8 * p)
{
      if (!IS_RADIO_ADDRESS(p))
            return (1);
      addr->c[0] = 0;
      addr->c[1] = 0;
      addr->c[2] = READHEX(p[0]) << 4 | READHEX(p[1]);
      addr->c[3] = READHEX(p[2]) << 4 | READHEX(p[3]);
      addr->c[4] = READHEX(p[5]) << 4 | READHEX(p[6]);
      addr->c[5] = READHEX(p[7]) << 4 | READHEX(p[8]);
      return (0);
}

/*
 * Convert a Metricom Address to a string.
 */

static __u8 *radio_address_to_string(const MetricomAddress * addr,
                             MetricomAddressString * p)
{
      sprintf(p->c, "%02X%02X-%02X%02X", addr->c[2], addr->c[3],
            addr->c[4], addr->c[5]);
      return (p->c);
}

/*
 * Note: Must make sure sx_size is big enough to receive a stuffed
 * MAX_RECV_MTU packet. Additionally, we also want to ensure that it's
 * big enough to receive a large radio neighbour list (currently 4K).
 */

static int allocate_buffers(struct strip *strip_info, int mtu)
{
      struct net_device *dev = strip_info->dev;
      int sx_size = max_t(int, STRIP_ENCAP_SIZE(MAX_RECV_MTU), 4096);
      int tx_size = STRIP_ENCAP_SIZE(mtu) + MaxCommandStringLength;
      __u8 *r = kmalloc(MAX_RECV_MTU, GFP_ATOMIC);
      __u8 *s = kmalloc(sx_size, GFP_ATOMIC);
      __u8 *t = kmalloc(tx_size, GFP_ATOMIC);
      if (r && s && t) {
            strip_info->rx_buff = r;
            strip_info->sx_buff = s;
            strip_info->tx_buff = t;
            strip_info->sx_size = sx_size;
            strip_info->tx_size = tx_size;
            strip_info->mtu = dev->mtu = mtu;
            return (1);
      }
      kfree(r);
      kfree(s);
      kfree(t);
      return (0);
}

/*
 * MTU has been changed by the IP layer. 
 * We could be in
 * an upcall from the tty driver, or in an ip packet queue.
 */
static int strip_change_mtu(struct net_device *dev, int new_mtu)
{
      struct strip *strip_info = netdev_priv(dev);
      int old_mtu = strip_info->mtu;
      unsigned char *orbuff = strip_info->rx_buff;
      unsigned char *osbuff = strip_info->sx_buff;
      unsigned char *otbuff = strip_info->tx_buff;

      if (new_mtu > MAX_SEND_MTU) {
            printk(KERN_ERR
                   "%s: MTU exceeds maximum allowable (%d), MTU change cancelled.\n",
                   strip_info->dev->name, MAX_SEND_MTU);
            return -EINVAL;
      }

      spin_lock_bh(&strip_lock);
      if (!allocate_buffers(strip_info, new_mtu)) {
            printk(KERN_ERR "%s: unable to grow strip buffers, MTU change cancelled.\n",
                   strip_info->dev->name);
            spin_unlock_bh(&strip_lock);
            return -ENOMEM;
      }

      if (strip_info->sx_count) {
            if (strip_info->sx_count <= strip_info->sx_size)
                  memcpy(strip_info->sx_buff, osbuff,
                         strip_info->sx_count);
            else {
                  strip_info->discard = strip_info->sx_count;
                  strip_info->rx_over_errors++;
            }
      }

      if (strip_info->tx_left) {
            if (strip_info->tx_left <= strip_info->tx_size)
                  memcpy(strip_info->tx_buff, strip_info->tx_head,
                         strip_info->tx_left);
            else {
                  strip_info->tx_left = 0;
                  strip_info->tx_dropped++;
            }
      }
      strip_info->tx_head = strip_info->tx_buff;
      spin_unlock_bh(&strip_lock);

      printk(KERN_NOTICE "%s: strip MTU changed fom %d to %d.\n",
             strip_info->dev->name, old_mtu, strip_info->mtu);

      kfree(orbuff);
      kfree(osbuff);
      kfree(otbuff);
      return 0;
}

static void strip_unlock(struct strip *strip_info)
{
      /*
       * Set the timer to go off in one second.
       */
      strip_info->idle_timer.expires = jiffies + 1 * HZ;
      add_timer(&strip_info->idle_timer);
      netif_wake_queue(strip_info->dev);
}



/*
 * If the time is in the near future, time_delta prints the number of
 * seconds to go into the buffer and returns the address of the buffer.
 * If the time is not in the near future, it returns the address of the
 * string "Not scheduled" The buffer must be long enough to contain the
 * ascii representation of the number plus 9 charactes for the " seconds"
 * and the null character.
 */
#ifdef CONFIG_PROC_FS
static char *time_delta(char buffer[], long time)
{
      time -= jiffies;
      if (time > LongTime / 2)
            return ("Not scheduled");
      if (time < 0)
            time = 0;   /* Don't print negative times */
      sprintf(buffer, "%ld seconds", time / HZ);
      return (buffer);
}

/* get Nth element of the linked list */
static struct strip *strip_get_idx(loff_t pos) 
{
      struct list_head *l;
      int i = 0;

      list_for_each_rcu(l, &strip_list) {
            if (pos == i)
                  return list_entry(l, struct strip, list);
            ++i;
      }
      return NULL;
}

static void *strip_seq_start(struct seq_file *seq, loff_t *pos)
{
      rcu_read_lock();
      return *pos ? strip_get_idx(*pos - 1) : SEQ_START_TOKEN;
}

static void *strip_seq_next(struct seq_file *seq, void *v, loff_t *pos)
{
      struct list_head *l;
      struct strip *s;

      ++*pos;
      if (v == SEQ_START_TOKEN)
            return strip_get_idx(1);

      s = v;
      l = &s->list;
      list_for_each_continue_rcu(l, &strip_list) {
            return list_entry(l, struct strip, list);
      }
      return NULL;
}

static void strip_seq_stop(struct seq_file *seq, void *v)
{
      rcu_read_unlock();
}

static void strip_seq_neighbours(struct seq_file *seq,
                     const MetricomNodeTable * table,
                     const char *title)
{
      /* We wrap this in a do/while loop, so if the table changes */
      /* while we're reading it, we just go around and try again. */
      struct timeval t;

      do {
            int i;
            t = table->timestamp;
            if (table->num_nodes)
                  seq_printf(seq, "\n %s\n", title);
            for (i = 0; i < table->num_nodes; i++) {
                  MetricomNode node;

                  spin_lock_bh(&strip_lock);
                  node = table->node[i];
                  spin_unlock_bh(&strip_lock);
                  seq_printf(seq, "  %s\n", node.c);
            }
      } while (table->timestamp.tv_sec != t.tv_sec
             || table->timestamp.tv_usec != t.tv_usec);
}

/*
 * This function prints radio status information via the seq_file
 * interface.  The interface takes care of buffer size and over
 * run issues. 
 *
 * The buffer in seq_file is PAGESIZE (4K) 
 * so this routine should never print more or it will get truncated.
 * With the maximum of 32 portables and 32 poletops
 * reported, the routine outputs 3107 bytes into the buffer.
 */
static void strip_seq_status_info(struct seq_file *seq, 
                          const struct strip *strip_info)
{
      char temp[32];
      MetricomAddressString addr_string;

      /* First, we must copy all of our data to a safe place, */
      /* in case a serial interrupt comes in and changes it.  */
      int tx_left = strip_info->tx_left;
      unsigned long rx_average_pps = strip_info->rx_average_pps;
      unsigned long tx_average_pps = strip_info->tx_average_pps;
      unsigned long sx_average_pps = strip_info->sx_average_pps;
      int working = strip_info->working;
      int firmware_level = strip_info->firmware_level;
      long watchdog_doprobe = strip_info->watchdog_doprobe;
      long watchdog_doreset = strip_info->watchdog_doreset;
      long gratuitous_arp = strip_info->gratuitous_arp;
      long arp_interval = strip_info->arp_interval;
      FirmwareVersion firmware_version = strip_info->firmware_version;
      SerialNumber serial_number = strip_info->serial_number;
      BatteryVoltage battery_voltage = strip_info->battery_voltage;
      char *if_name = strip_info->dev->name;
      MetricomAddress true_dev_addr = strip_info->true_dev_addr;
      MetricomAddress dev_dev_addr =
          *(MetricomAddress *) strip_info->dev->dev_addr;
      int manual_dev_addr = strip_info->manual_dev_addr;
#ifdef EXT_COUNTERS
      unsigned long rx_bytes = strip_info->rx_bytes;
      unsigned long tx_bytes = strip_info->tx_bytes;
      unsigned long rx_rbytes = strip_info->rx_rbytes;
      unsigned long tx_rbytes = strip_info->tx_rbytes;
      unsigned long rx_sbytes = strip_info->rx_sbytes;
      unsigned long tx_sbytes = strip_info->tx_sbytes;
      unsigned long rx_ebytes = strip_info->rx_ebytes;
      unsigned long tx_ebytes = strip_info->tx_ebytes;
#endif

      seq_printf(seq, "\nInterface name\t\t%s\n", if_name);
      seq_printf(seq, " Radio working:\t\t%s\n", working ? "Yes" : "No");
      radio_address_to_string(&true_dev_addr, &addr_string);
      seq_printf(seq, " Radio address:\t\t%s\n", addr_string.c);
      if (manual_dev_addr) {
            radio_address_to_string(&dev_dev_addr, &addr_string);
            seq_printf(seq, " Device address:\t%s\n", addr_string.c);
      }
      seq_printf(seq, " Firmware version:\t%s", !working ? "Unknown" :
                 !firmware_level ? "Should be upgraded" :
                 firmware_version.c);
      if (firmware_level >= ChecksummedMessages)
            seq_printf(seq, " (Checksums Enabled)");
      seq_printf(seq, "\n");
      seq_printf(seq, " Serial number:\t\t%s\n", serial_number.c);
      seq_printf(seq, " Battery voltage:\t%s\n", battery_voltage.c);
      seq_printf(seq, " Transmit queue (bytes):%d\n", tx_left);
      seq_printf(seq, " Receive packet rate:   %ld packets per second\n",
                 rx_average_pps / 8);
      seq_printf(seq, " Transmit packet rate:  %ld packets per second\n",
                 tx_average_pps / 8);
      seq_printf(seq, " Sent packet rate:      %ld packets per second\n",
                 sx_average_pps / 8);
      seq_printf(seq, " Next watchdog probe:\t%s\n",
                 time_delta(temp, watchdog_doprobe));
      seq_printf(seq, " Next watchdog reset:\t%s\n",
                 time_delta(temp, watchdog_doreset));
      seq_printf(seq, " Next gratuitous ARP:\t");

      if (!memcmp
          (strip_info->dev->dev_addr, zero_address.c,
           sizeof(zero_address)))
            seq_printf(seq, "Disabled\n");
      else {
            seq_printf(seq, "%s\n", time_delta(temp, gratuitous_arp));
            seq_printf(seq, " Next ARP interval:\t%ld seconds\n",
                       JIFFIE_TO_SEC(arp_interval));
      }

      if (working) {
#ifdef EXT_COUNTERS
            seq_printf(seq, "\n");
            seq_printf(seq,
                       " Total bytes:         \trx:\t%lu\ttx:\t%lu\n",
                       rx_bytes, tx_bytes);
            seq_printf(seq,
                       "  thru radio:         \trx:\t%lu\ttx:\t%lu\n",
                       rx_rbytes, tx_rbytes);
            seq_printf(seq,
                       "  thru serial port:   \trx:\t%lu\ttx:\t%lu\n",
                       rx_sbytes, tx_sbytes);
            seq_printf(seq,
                       " Total stat/err bytes:\trx:\t%lu\ttx:\t%lu\n",
                       rx_ebytes, tx_ebytes);
#endif
            strip_seq_neighbours(seq, &strip_info->poletops,
                              "Poletops:");
            strip_seq_neighbours(seq, &strip_info->portables,
                              "Portables:");
      }
}

/*
 * This function is exports status information from the STRIP driver through
 * the /proc file system.
 */
static int strip_seq_show(struct seq_file *seq, void *v)
{
      if (v == SEQ_START_TOKEN)
            seq_printf(seq, "strip_version: %s\n", StripVersion);
      else
            strip_seq_status_info(seq, (const struct strip *)v);
      return 0;
}


static struct seq_operations strip_seq_ops = {
      .start = strip_seq_start,
      .next  = strip_seq_next,
      .stop  = strip_seq_stop,
      .show  = strip_seq_show,
};

static int strip_seq_open(struct inode *inode, struct file *file)
{
      return seq_open(file, &strip_seq_ops);
}

static struct file_operations strip_seq_fops = {
      .owner       = THIS_MODULE,
      .open    = strip_seq_open,
      .read    = seq_read,
      .llseek  = seq_lseek,
      .release = seq_release,
};
#endif



/************************************************************************/
/* Sending routines                                         */

static void ResetRadio(struct strip *strip_info)
{
      struct tty_struct *tty = strip_info->tty;
      static const char init[] = "ate0q1dt**starmode\r**";
      StringDescriptor s = { init, sizeof(init) - 1 };

      /* 
       * If the radio isn't working anymore,
       * we should clear the old status information.
       */
      if (strip_info->working) {
            printk(KERN_INFO "%s: No response: Resetting radio.\n",
                   strip_info->dev->name);
            strip_info->firmware_version.c[0] = '\0';
            strip_info->serial_number.c[0] = '\0';
            strip_info->battery_voltage.c[0] = '\0';
            strip_info->portables.num_nodes = 0;
            do_gettimeofday(&strip_info->portables.timestamp);
            strip_info->poletops.num_nodes = 0;
            do_gettimeofday(&strip_info->poletops.timestamp);
      }

      strip_info->pps_timer = jiffies;
      strip_info->rx_pps_count = 0;
      strip_info->tx_pps_count = 0;
      strip_info->sx_pps_count = 0;
      strip_info->rx_average_pps = 0;
      strip_info->tx_average_pps = 0;
      strip_info->sx_average_pps = 0;

      /* Mark radio address as unknown */
      *(MetricomAddress *) & strip_info->true_dev_addr = zero_address;
      if (!strip_info->manual_dev_addr)
            *(MetricomAddress *) strip_info->dev->dev_addr =
                zero_address;
      strip_info->working = FALSE;
      strip_info->firmware_level = NoStructure;
      strip_info->next_command = CompatibilityCommand;
      strip_info->watchdog_doprobe = jiffies + 10 * HZ;
      strip_info->watchdog_doreset = jiffies + 1 * HZ;

      /* If the user has selected a baud rate above 38.4 see what magic we have to do */
      if (strip_info->user_baud > B38400) {
            /*
             * Subtle stuff: Pay attention :-)
             * If the serial port is currently at the user's selected (>38.4) rate,
             * then we temporarily switch to 19.2 and issue the ATS304 command
             * to tell the radio to switch to the user's selected rate.
             * If the serial port is not currently at that rate, that means we just
             * issued the ATS304 command last time through, so this time we restore
             * the user's selected rate and issue the normal starmode reset string.
             */
            if (strip_info->user_baud == get_baud(tty)) {
                  static const char b0[] = "ate0q1s304=57600\r";
                  static const char b1[] = "ate0q1s304=115200\r";
                  static const StringDescriptor baudstring[2] =
                      { {b0, sizeof(b0) - 1}
                  , {b1, sizeof(b1) - 1}
                  };
                  set_baud(tty, B19200);
                  if (strip_info->user_baud == B57600)
                        s = baudstring[0];
                  else if (strip_info->user_baud == B115200)
                        s = baudstring[1];
                  else
                        s = baudstring[1];      /* For now */
            } else
                  set_baud(tty, strip_info->user_baud);
      }

      tty->driver->write(tty, s.string, s.length);
#ifdef EXT_COUNTERS
      strip_info->tx_ebytes += s.length;
#endif
}

/*
 * Called by the driver when there's room for more data.  If we have
 * more packets to send, we send them here.
 */

static void strip_write_some_more(struct tty_struct *tty)
{
      struct strip *strip_info = (struct strip *) tty->disc_data;

      /* First make sure we're connected. */
      if (!strip_info || strip_info->magic != STRIP_MAGIC ||
          !netif_running(strip_info->dev))
            return;

      if (strip_info->tx_left > 0) {
            int num_written =
                tty->driver->write(tty, strip_info->tx_head,
                              strip_info->tx_left);
            strip_info->tx_left -= num_written;
            strip_info->tx_head += num_written;
#ifdef EXT_COUNTERS
            strip_info->tx_sbytes += num_written;
#endif
      } else {          /* Else start transmission of another packet */

            tty->flags &= ~(1 << TTY_DO_WRITE_WAKEUP);
            strip_unlock(strip_info);
      }
}

static __u8 *add_checksum(__u8 * buffer, __u8 * end)
{
      __u16 sum = 0;
      __u8 *p = buffer;
      while (p < end)
            sum += *p++;
      end[3] = hextable[sum & 0xF];
      sum >>= 4;
      end[2] = hextable[sum & 0xF];
      sum >>= 4;
      end[1] = hextable[sum & 0xF];
      sum >>= 4;
      end[0] = hextable[sum & 0xF];
      return (end + 4);
}

static unsigned char *strip_make_packet(unsigned char *buffer,
                              struct strip *strip_info,
                              struct sk_buff *skb)
{
      __u8 *ptr = buffer;
      __u8 *stuffstate = NULL;
      STRIP_Header *header = (STRIP_Header *) skb->data;
      MetricomAddress haddr = header->dst_addr;
      int len = skb->len - sizeof(STRIP_Header);
      MetricomKey key;

      /*HexDump("strip_make_packet", strip_info, skb->data, skb->data + skb->len); */

      if (header->protocol == htons(ETH_P_IP))
            key = SIP0Key;
      else if (header->protocol == htons(ETH_P_ARP))
            key = ARP0Key;
      else {
            printk(KERN_ERR
                   "%s: strip_make_packet: Unknown packet type 0x%04X\n",
                   strip_info->dev->name, ntohs(header->protocol));
            return (NULL);
      }

      if (len > strip_info->mtu) {
            printk(KERN_ERR
                   "%s: Dropping oversized transmit packet: %d bytes\n",
                   strip_info->dev->name, len);
            return (NULL);
      }

      /*
       * If we're sending to ourselves, discard the packet.
       * (Metricom radios choke if they try to send a packet to their own address.)
       */
      if (!memcmp(haddr.c, strip_info->true_dev_addr.c, sizeof(haddr))) {
            printk(KERN_ERR "%s: Dropping packet addressed to self\n",
                   strip_info->dev->name);
            return (NULL);
      }

      /*
       * If this is a broadcast packet, send it to our designated Metricom
       * 'broadcast hub' radio (First byte of address being 0xFF means broadcast)
       */
      if (haddr.c[0] == 0xFF) {
            u32 brd = 0;
            struct in_device *in_dev;

            rcu_read_lock();
            in_dev = __in_dev_get_rcu(strip_info->dev);
            if (in_dev == NULL) {
                  rcu_read_unlock();
                  return NULL;
            }
            if (in_dev->ifa_list)
                  brd = in_dev->ifa_list->ifa_broadcast;
            rcu_read_unlock();

            /* arp_query returns 1 if it succeeds in looking up the address, 0 if it fails */
            if (!arp_query(haddr.c, brd, strip_info->dev)) {
                  printk(KERN_ERR
                         "%s: Unable to send packet (no broadcast hub configured)\n",
                         strip_info->dev->name);
                  return (NULL);
            }
            /*
             * If we are the broadcast hub, don't bother sending to ourselves.
             * (Metricom radios choke if they try to send a packet to their own address.)
             */
            if (!memcmp
                (haddr.c, strip_info->true_dev_addr.c, sizeof(haddr)))
                  return (NULL);
      }

      *ptr++ = 0x0D;
      *ptr++ = '*';
      *ptr++ = hextable[haddr.c[2] >> 4];
      *ptr++ = hextable[haddr.c[2] & 0xF];
      *ptr++ = hextable[haddr.c[3] >> 4];
      *ptr++ = hextable[haddr.c[3] & 0xF];
      *ptr++ = '-';
      *ptr++ = hextable[haddr.c[4] >> 4];
      *ptr++ = hextable[haddr.c[4] & 0xF];
      *ptr++ = hextable[haddr.c[5] >> 4];
      *ptr++ = hextable[haddr.c[5] & 0xF];
      *ptr++ = '*';
      *ptr++ = key.c[0];
      *ptr++ = key.c[1];
      *ptr++ = key.c[2];
      *ptr++ = key.c[3];

      ptr =
          StuffData(skb->data + sizeof(STRIP_Header), len, ptr,
                  &stuffstate);

      if (strip_info->firmware_level >= ChecksummedMessages)
            ptr = add_checksum(buffer + 1, ptr);

      *ptr++ = 0x0D;
      return (ptr);
}

static void strip_send(struct strip *strip_info, struct sk_buff *skb)
{
      MetricomAddress haddr;
      unsigned char *ptr = strip_info->tx_buff;
      int doreset = (long) jiffies - strip_info->watchdog_doreset >= 0;
      int doprobe = (long) jiffies - strip_info->watchdog_doprobe >= 0
          && !doreset;
      u32 addr, brd;

      /*
       * 1. If we have a packet, encapsulate it and put it in the buffer
       */
      if (skb) {
            char *newptr = strip_make_packet(ptr, strip_info, skb);
            strip_info->tx_pps_count++;
            if (!newptr)
                  strip_info->tx_dropped++;
            else {
                  ptr = newptr;
                  strip_info->sx_pps_count++;
                  strip_info->tx_packets++;     /* Count another successful packet */
#ifdef EXT_COUNTERS
                  strip_info->tx_bytes += skb->len;
                  strip_info->tx_rbytes += ptr - strip_info->tx_buff;
#endif
                  /*DumpData("Sending:", strip_info, strip_info->tx_buff, ptr); */
                  /*HexDump("Sending", strip_info, strip_info->tx_buff, ptr); */
            }
      }

      /*
       * 2. If it is time for another tickle, tack it on, after the packet
       */
      if (doprobe) {
            StringDescriptor ts = CommandString[strip_info->next_command];
#if TICKLE_TIMERS
            {
                  struct timeval tv;
                  do_gettimeofday(&tv);
                  printk(KERN_INFO "**** Sending tickle string %d      at %02d.%06d\n",
                         strip_info->next_command, tv.tv_sec % 100,
                         tv.tv_usec);
            }
#endif
            if (ptr == strip_info->tx_buff)
                  *ptr++ = 0x0D;

            *ptr++ = '*';     /* First send "**" to provoke an error message */
            *ptr++ = '*';

            /* Then add the command */
            memcpy(ptr, ts.string, ts.length);

            /* Add a checksum ? */
            if (strip_info->firmware_level < ChecksummedMessages)
                  ptr += ts.length;
            else
                  ptr = add_checksum(ptr, ptr + ts.length);

            *ptr++ = 0x0D;    /* Terminate the command with a <CR> */

            /* Cycle to next periodic command? */
            if (strip_info->firmware_level >= StructuredMessages)
                  if (++strip_info->next_command >=
                      ARRAY_SIZE(CommandString))
                        strip_info->next_command = 0;
#ifdef EXT_COUNTERS
            strip_info->tx_ebytes += ts.length;
#endif
            strip_info->watchdog_doprobe = jiffies + 10 * HZ;
            strip_info->watchdog_doreset = jiffies + 1 * HZ;
            /*printk(KERN_INFO "%s: Routine radio test.\n", strip_info->dev->name); */
      }

      /*
       * 3. Set up the strip_info ready to send the data (if any).
       */
      strip_info->tx_head = strip_info->tx_buff;
      strip_info->tx_left = ptr - strip_info->tx_buff;
      strip_info->tty->flags |= (1 << TTY_DO_WRITE_WAKEUP);

      /*
       * 4. Debugging check to make sure we're not overflowing the buffer.
       */
      if (strip_info->tx_size - strip_info->tx_left < 20)
            printk(KERN_ERR "%s: Sending%5d bytes;%5d bytes free.\n",
                   strip_info->dev->name, strip_info->tx_left,
                   strip_info->tx_size - strip_info->tx_left);

      /*
       * 5. If watchdog has expired, reset the radio. Note: if there's data waiting in
       * the buffer, strip_write_some_more will send it after the reset has finished
       */
      if (doreset) {
            ResetRadio(strip_info);
            return;
      }

      if (1) {
            struct in_device *in_dev;

            brd = addr = 0;
            rcu_read_lock();
            in_dev = __in_dev_get_rcu(strip_info->dev);
            if (in_dev) {
                  if (in_dev->ifa_list) {
                        brd = in_dev->ifa_list->ifa_broadcast;
                        addr = in_dev->ifa_list->ifa_local;
                  }
            }
            rcu_read_unlock();
      }


      /*
       * 6. If it is time for a periodic ARP, queue one up to be sent.
       * We only do this if:
       *  1. The radio is working
       *  2. It's time to send another periodic ARP
       *  3. We really know what our address is (and it is not manually set to zero)
       *  4. We have a designated broadcast address configured
       * If we queue up an ARP packet when we don't have a designated broadcast
       * address configured, then the packet will just have to be discarded in
       * strip_make_packet. This is not fatal, but it causes misleading information
       * to be displayed in tcpdump. tcpdump will report that periodic APRs are
       * being sent, when in fact they are not, because they are all being dropped
       * in the strip_make_packet routine.
       */
      if (strip_info->working
          && (long) jiffies - strip_info->gratuitous_arp >= 0
          && memcmp(strip_info->dev->dev_addr, zero_address.c,
                  sizeof(zero_address))
          && arp_query(haddr.c, brd, strip_info->dev)) {
            /*printk(KERN_INFO "%s: Sending gratuitous ARP with interval %ld\n",
               strip_info->dev->name, strip_info->arp_interval / HZ); */
            strip_info->gratuitous_arp =
                jiffies + strip_info->arp_interval;
            strip_info->arp_interval *= 2;
            if (strip_info->arp_interval > MaxARPInterval)
                  strip_info->arp_interval = MaxARPInterval;
            if (addr)
                  arp_send(ARPOP_REPLY, ETH_P_ARP, addr,    /* Target address of ARP packet is our address */
                         strip_info->dev, /* Device to send packet on */
                         addr,      /* Source IP address this ARP packet comes from */
                         NULL,      /* Destination HW address is NULL (broadcast it) */
                         strip_info->dev->dev_addr,   /* Source HW address is our HW address */
                         strip_info->dev->dev_addr);  /* Target HW address is our HW address (redundant) */
      }

      /*
       * 7. All ready. Start the transmission
       */
      strip_write_some_more(strip_info->tty);
}

/* Encapsulate a datagram and kick it into a TTY queue. */
static int strip_xmit(struct sk_buff *skb, struct net_device *dev)
{
      struct strip *strip_info = netdev_priv(dev);

      if (!netif_running(dev)) {
            printk(KERN_ERR "%s: xmit call when iface is down\n",
                   dev->name);
            return (1);
      }

      netif_stop_queue(dev);

      del_timer(&strip_info->idle_timer);


      if (time_after(jiffies, strip_info->pps_timer + HZ)) {
            unsigned long t = jiffies - strip_info->pps_timer;
            unsigned long rx_pps_count = (strip_info->rx_pps_count * HZ * 8 + t / 2) / t;
            unsigned long tx_pps_count = (strip_info->tx_pps_count * HZ * 8 + t / 2) / t;
            unsigned long sx_pps_count = (strip_info->sx_pps_count * HZ * 8 + t / 2) / t;

            strip_info->pps_timer = jiffies;
            strip_info->rx_pps_count = 0;
            strip_info->tx_pps_count = 0;
            strip_info->sx_pps_count = 0;

            strip_info->rx_average_pps = (strip_info->rx_average_pps + rx_pps_count + 1) / 2;
            strip_info->tx_average_pps = (strip_info->tx_average_pps + tx_pps_count + 1) / 2;
            strip_info->sx_average_pps = (strip_info->sx_average_pps + sx_pps_count + 1) / 2;

            if (rx_pps_count / 8 >= 10)
                  printk(KERN_INFO "%s: WARNING: Receiving %ld packets per second.\n",
                         strip_info->dev->name, rx_pps_count / 8);
            if (tx_pps_count / 8 >= 10)
                  printk(KERN_INFO "%s: WARNING: Tx        %ld packets per second.\n",
                         strip_info->dev->name, tx_pps_count / 8);
            if (sx_pps_count / 8 >= 10)
                  printk(KERN_INFO "%s: WARNING: Sending   %ld packets per second.\n",
                         strip_info->dev->name, sx_pps_count / 8);
      }

      spin_lock_bh(&strip_lock);

      strip_send(strip_info, skb);

      spin_unlock_bh(&strip_lock);

      if (skb)
            dev_kfree_skb(skb);
      return 0;
}

/*
 * IdleTask periodically calls strip_xmit, so even when we have no IP packets
 * to send for an extended period of time, the watchdog processing still gets
 * done to ensure that the radio stays in Starmode
 */

static void strip_IdleTask(unsigned long parameter)
{
      strip_xmit(NULL, (struct net_device *) parameter);
}

/*
 * Create the MAC header for an arbitrary protocol layer
 *
 * saddr!=NULL        means use this specific address (n/a for Metricom)
 * saddr==NULL        means use default device source address
 * daddr!=NULL        means use this destination address
 * daddr==NULL        means leave destination address alone
 *                 (e.g. unresolved arp -- kernel will call
 *                 rebuild_header later to fill in the address)
 */

static int strip_header(struct sk_buff *skb, struct net_device *dev,
                  unsigned short type, void *daddr, void *saddr,
                  unsigned len)
{
      struct strip *strip_info = netdev_priv(dev);
      STRIP_Header *header = (STRIP_Header *) skb_push(skb, sizeof(STRIP_Header));

      /*printk(KERN_INFO "%s: strip_header 0x%04X %s\n", dev->name, type,
         type == ETH_P_IP ? "IP" : type == ETH_P_ARP ? "ARP" : ""); */

      header->src_addr = strip_info->true_dev_addr;
      header->protocol = htons(type);

      /*HexDump("strip_header", netdev_priv(dev), skb->data, skb->data + skb->len); */

      if (!daddr)
            return (-dev->hard_header_len);

      header->dst_addr = *(MetricomAddress *) daddr;
      return (dev->hard_header_len);
}

/*
 * Rebuild the MAC header. This is called after an ARP
 * (or in future other address resolution) has completed on this
 * sk_buff. We now let ARP fill in the other fields.
 * I think this should return zero if packet is ready to send,
 * or non-zero if it needs more time to do an address lookup
 */

static int strip_rebuild_header(struct sk_buff *skb)
{
#ifdef CONFIG_INET
      STRIP_Header *header = (STRIP_Header *) skb->data;

      /* Arp find returns zero if if knows the address, */
      /* or if it doesn't know the address it sends an ARP packet and returns non-zero */
      return arp_find(header->dst_addr.c, skb) ? 1 : 0;
#else
      return 0;
#endif
}


/************************************************************************/
/* Receiving routines                                       */

/*
 * This function parses the response to the ATS300? command,
 * extracting the radio version and serial number.
 */
static void get_radio_version(struct strip *strip_info, __u8 * ptr, __u8 * end)
{
      __u8 *p, *value_begin, *value_end;
      int len;

      /* Determine the beginning of the second line of the payload */
      p = ptr;
      while (p < end && *p != 10)
            p++;
      if (p >= end)
            return;
      p++;
      value_begin = p;

      /* Determine the end of line */
      while (p < end && *p != 10)
            p++;
      if (p >= end)
            return;
      value_end = p;
      p++;

      len = value_end - value_begin;
      len = min_t(int, len, sizeof(FirmwareVersion) - 1);
      if (strip_info->firmware_version.c[0] == 0)
            printk(KERN_INFO "%s: Radio Firmware: %.*s\n",
                   strip_info->dev->name, len, value_begin);
      sprintf(strip_info->firmware_version.c, "%.*s", len, value_begin);

      /* Look for the first colon */
      while (p < end && *p != ':')
            p++;
      if (p >= end)
            return;
      /* Skip over the space */
      p += 2;
      len = sizeof(SerialNumber) - 1;
      if (p + len <= end) {
            sprintf(strip_info->serial_number.c, "%.*s", len, p);
      } else {
            printk(KERN_DEBUG
                   "STRIP: radio serial number shorter (%zd) than expected (%d)\n",
                   end - p, len);
      }
}

/*
 * This function parses the response to the ATS325? command,
 * extracting the radio battery voltage.
 */
static void get_radio_voltage(struct strip *strip_info, __u8 * ptr, __u8 * end)
{
      int len;

      len = sizeof(BatteryVoltage) - 1;
      if (ptr + len <= end) {
            sprintf(strip_info->battery_voltage.c, "%.*s", len, ptr);
      } else {
            printk(KERN_DEBUG
                   "STRIP: radio voltage string shorter (%zd) than expected (%d)\n",
                   end - ptr, len);
      }
}

/*
 * This function parses the responses to the AT~LA and ATS311 commands,
 * which list the radio's neighbours.
 */
static void get_radio_neighbours(MetricomNodeTable * table, __u8 * ptr, __u8 * end)
{
      table->num_nodes = 0;
      while (ptr < end && table->num_nodes < NODE_TABLE_SIZE) {
            MetricomNode *node = &table->node[table->num_nodes++];
            char *dst = node->c, *limit = dst + sizeof(*node) - 1;
            while (ptr < end && *ptr <= 32)
                  ptr++;
            while (ptr < end && dst < limit && *ptr != 10)
                  *dst++ = *ptr++;
            *dst++ = 0;
            while (ptr < end && ptr[-1] != 10)
                  ptr++;
      }
      do_gettimeofday(&table->timestamp);
}

static int get_radio_address(struct strip *strip_info, __u8 * p)
{
      MetricomAddress addr;

      if (string_to_radio_address(&addr, p))
            return (1);

      /* See if our radio address has changed */
      if (memcmp(strip_info->true_dev_addr.c, addr.c, sizeof(addr))) {
            MetricomAddressString addr_string;
            radio_address_to_string(&addr, &addr_string);
            printk(KERN_INFO "%s: Radio address = %s\n",
                   strip_info->dev->name, addr_string.c);
            strip_info->true_dev_addr = addr;
            if (!strip_info->manual_dev_addr)
                  *(MetricomAddress *) strip_info->dev->dev_addr =
                      addr;
            /* Give the radio a few seconds to get its head straight, then send an arp */
            strip_info->gratuitous_arp = jiffies + 15 * HZ;
            strip_info->arp_interval = 1 * HZ;
      }
      return (0);
}

static int verify_checksum(struct strip *strip_info)
{
      __u8 *p = strip_info->sx_buff;
      __u8 *end = strip_info->sx_buff + strip_info->sx_count - 4;
      u_short sum =
          (READHEX16(end[0]) << 12) | (READHEX16(end[1]) << 8) |
          (READHEX16(end[2]) << 4) | (READHEX16(end[3]));
      while (p < end)
            sum -= *p++;
      if (sum == 0 && strip_info->firmware_level == StructuredMessages) {
            strip_info->firmware_level = ChecksummedMessages;
            printk(KERN_INFO "%s: Radio provides message checksums\n",
                   strip_info->dev->name);
      }
      return (sum == 0);
}

static void RecvErr(char *msg, struct strip *strip_info)
{
      __u8 *ptr = strip_info->sx_buff;
      __u8 *end = strip_info->sx_buff + strip_info->sx_count;
      DumpData(msg, strip_info, ptr, end);
      strip_info->rx_errors++;
}

static void RecvErr_Message(struct strip *strip_info, __u8 * sendername,
                      const __u8 * msg, u_long len)
{
      if (has_prefix(msg, len, "001")) {  /* Not in StarMode! */
            RecvErr("Error Msg:", strip_info);
            printk(KERN_INFO "%s: Radio %s is not in StarMode\n",
                   strip_info->dev->name, sendername);
      }

      else if (has_prefix(msg, len, "002")) {   /* Remap handle */
            /* We ignore "Remap handle" messages for now */
      }

      else if (has_prefix(msg, len, "003")) {   /* Can't resolve name */
            RecvErr("Error Msg:", strip_info);
            printk(KERN_INFO "%s: Destination radio name is unknown\n",
                   strip_info->dev->name);
      }

      else if (has_prefix(msg, len, "004")) {   /* Name too small or missing */
            strip_info->watchdog_doreset = jiffies + LongTime;
#if TICKLE_TIMERS
            {
                  struct timeval tv;
                  do_gettimeofday(&tv);
                  printk(KERN_INFO
                         "**** Got ERR_004 response         at %02d.%06d\n",
                         tv.tv_sec % 100, tv.tv_usec);
            }
#endif
            if (!strip_info->working) {
                  strip_info->working = TRUE;
                  printk(KERN_INFO "%s: Radio now in starmode\n",
                         strip_info->dev->name);
                  /*
                   * If the radio has just entered a working state, we should do our first
                   * probe ASAP, so that we find out our radio address etc. without delay.
                   */
                  strip_info->watchdog_doprobe = jiffies;
            }
            if (strip_info->firmware_level == NoStructure && sendername) {
                  strip_info->firmware_level = StructuredMessages;
                  strip_info->next_command = 0; /* Try to enable checksums ASAP */
                  printk(KERN_INFO
                         "%s: Radio provides structured messages\n",
                         strip_info->dev->name);
            }
            if (strip_info->firmware_level >= StructuredMessages) {
                  /*
                   * If this message has a valid checksum on the end, then the call to verify_checksum
                   * will elevate the firmware_level to ChecksummedMessages for us. (The actual return
                   * code from verify_checksum is ignored here.)
                   */
                  verify_checksum(strip_info);
                  /*
                   * If the radio has structured messages but we don't yet have all our information about it,
                   * we should do probes without delay, until we have gathered all the information
                   */
                  if (!GOT_ALL_RADIO_INFO(strip_info))
                        strip_info->watchdog_doprobe = jiffies;
            }
      }

      else if (has_prefix(msg, len, "005"))     /* Bad count specification */
            RecvErr("Error Msg:", strip_info);

      else if (has_prefix(msg, len, "006"))     /* Header too big */
            RecvErr("Error Msg:", strip_info);

      else if (has_prefix(msg, len, "007")) {   /* Body too big */
            RecvErr("Error Msg:", strip_info);
            printk(KERN_ERR
                   "%s: Error! Packet size too big for radio.\n",
                   strip_info->dev->name);
      }

      else if (has_prefix(msg, len, "008")) {   /* Bad character in name */
            RecvErr("Error Msg:", strip_info);
            printk(KERN_ERR
                   "%s: Radio name contains illegal character\n",
                   strip_info->dev->name);
      }

      else if (has_prefix(msg, len, "009"))     /* No count or line terminator */
            RecvErr("Error Msg:", strip_info);

      else if (has_prefix(msg, len, "010"))     /* Invalid checksum */
            RecvErr("Error Msg:", strip_info);

      else if (has_prefix(msg, len, "011"))     /* Checksum didn't match */
            RecvErr("Error Msg:", strip_info);

      else if (has_prefix(msg, len, "012"))     /* Failed to transmit packet */
            RecvErr("Error Msg:", strip_info);

      else
            RecvErr("Error Msg:", strip_info);
}

static void process_AT_response(struct strip *strip_info, __u8 * ptr,
                        __u8 * end)
{
      u_long len;
      __u8 *p = ptr;
      while (p < end && p[-1] != 10)
            p++;        /* Skip past first newline character */
      /* Now ptr points to the AT command, and p points to the text of the response. */
      len = p - ptr;

#if TICKLE_TIMERS
      {
            struct timeval tv;
            do_gettimeofday(&tv);
            printk(KERN_INFO "**** Got AT response %.7s      at %02d.%06d\n",
                   ptr, tv.tv_sec % 100, tv.tv_usec);
      }
#endif

      if (has_prefix(ptr, len, "ATS300?"))
            get_radio_version(strip_info, p, end);
      else if (has_prefix(ptr, len, "ATS305?"))
            get_radio_address(strip_info, p);
      else if (has_prefix(ptr, len, "ATS311?"))
            get_radio_neighbours(&strip_info->poletops, p, end);
      else if (has_prefix(ptr, len, "ATS319=7"))
            verify_checksum(strip_info);
      else if (has_prefix(ptr, len, "ATS325?"))
            get_radio_voltage(strip_info, p, end);
      else if (has_prefix(ptr, len, "AT~LA"))
            get_radio_neighbours(&strip_info->portables, p, end);
      else
            RecvErr("Unknown AT Response:", strip_info);
}

static void process_ACK(struct strip *strip_info, __u8 * ptr, __u8 * end)
{
      /* Currently we don't do anything with ACKs from the radio */
}

static void process_Info(struct strip *strip_info, __u8 * ptr, __u8 * end)
{
      if (ptr + 16 > end)
            RecvErr("Bad Info Msg:", strip_info);
}

static struct net_device *get_strip_dev(struct strip *strip_info)
{
      /* If our hardware address is *manually set* to zero, and we know our */
      /* real radio hardware address, try to find another strip device that has been */
      /* manually set to that address that we can 'transfer ownership' of this packet to  */
      if (strip_info->manual_dev_addr &&
          !memcmp(strip_info->dev->dev_addr, zero_address.c,
                sizeof(zero_address))
          && memcmp(&strip_info->true_dev_addr, zero_address.c,
                  sizeof(zero_address))) {
            struct net_device *dev;
            read_lock_bh(&dev_base_lock);
            dev = dev_base;
            while (dev) {
                  if (dev->type == strip_info->dev->type &&
                      !memcmp(dev->dev_addr,
                            &strip_info->true_dev_addr,
                            sizeof(MetricomAddress))) {
                        printk(KERN_INFO
                               "%s: Transferred packet ownership to %s.\n",
                               strip_info->dev->name, dev->name);
                        read_unlock_bh(&dev_base_lock);
                        return (dev);
                  }
                  dev = dev->next;
            }
            read_unlock_bh(&dev_base_lock);
      }
      return (strip_info->dev);
}

/*
 * Send one completely decapsulated datagram to the next layer.
 */

static void deliver_packet(struct strip *strip_info, STRIP_Header * header,
                     __u16 packetlen)
{
      struct sk_buff *skb = dev_alloc_skb(sizeof(STRIP_Header) + packetlen);
      if (!skb) {
            printk(KERN_ERR "%s: memory squeeze, dropping packet.\n",
                   strip_info->dev->name);
            strip_info->rx_dropped++;
      } else {
            memcpy(skb_put(skb, sizeof(STRIP_Header)), header,
                   sizeof(STRIP_Header));
            memcpy(skb_put(skb, packetlen), strip_info->rx_buff,
                   packetlen);
            skb->dev = get_strip_dev(strip_info);
            skb->protocol = header->protocol;
            skb->mac.raw = skb->data;

            /* Having put a fake header on the front of the sk_buff for the */
            /* benefit of tools like tcpdump, skb_pull now 'consumes' that  */
            /* fake header before we hand the packet up to the next layer.  */
            skb_pull(skb, sizeof(STRIP_Header));

            /* Finally, hand the packet up to the next layer (e.g. IP or ARP, etc.) */
            strip_info->rx_packets++;
            strip_info->rx_pps_count++;
#ifdef EXT_COUNTERS
            strip_info->rx_bytes += packetlen;
#endif
            skb->dev->last_rx = jiffies;
            netif_rx(skb);
      }
}

static void process_IP_packet(struct strip *strip_info,
                        STRIP_Header * header, __u8 * ptr,
                        __u8 * end)
{
      __u16 packetlen;

      /* Decode start of the IP packet header */
      ptr = UnStuffData(ptr, end, strip_info->rx_buff, 4);
      if (!ptr) {
            RecvErr("IP Packet too short", strip_info);
            return;
      }

      packetlen = ((__u16) strip_info->rx_buff[2] << 8) | strip_info->rx_buff[3];

      if (packetlen > MAX_RECV_MTU) {
            printk(KERN_INFO "%s: Dropping oversized received IP packet: %d bytes\n",
                   strip_info->dev->name, packetlen);
            strip_info->rx_dropped++;
            return;
      }

      /*printk(KERN_INFO "%s: Got %d byte IP packet\n", strip_info->dev->name, packetlen); */

      /* Decode remainder of the IP packet */
      ptr =
          UnStuffData(ptr, end, strip_info->rx_buff + 4, packetlen - 4);
      if (!ptr) {
            RecvErr("IP Packet too short", strip_info);
            return;
      }

      if (ptr < end) {
            RecvErr("IP Packet too long", strip_info);
            return;
      }

      header->protocol = htons(ETH_P_IP);

      deliver_packet(strip_info, header, packetlen);
}

static void process_ARP_packet(struct strip *strip_info,
                         STRIP_Header * header, __u8 * ptr,
                         __u8 * end)
{
      __u16 packetlen;
      struct arphdr *arphdr = (struct arphdr *) strip_info->rx_buff;

      /* Decode start of the ARP packet */
      ptr = UnStuffData(ptr, end, strip_info->rx_buff, 8);
      if (!ptr) {
            RecvErr("ARP Packet too short", strip_info);
            return;
      }

      packetlen = 8 + (arphdr->ar_hln + arphdr->ar_pln) * 2;

      if (packetlen > MAX_RECV_MTU) {
            printk(KERN_INFO
                   "%s: Dropping oversized received ARP packet: %d bytes\n",
                   strip_info->dev->name, packetlen);
            strip_info->rx_dropped++;
            return;
      }

      /*printk(KERN_INFO "%s: Got %d byte ARP %s\n",
         strip_info->dev->name, packetlen,
         ntohs(arphdr->ar_op) == ARPOP_REQUEST ? "request" : "reply"); */

      /* Decode remainder of the ARP packet */
      ptr =
          UnStuffData(ptr, end, strip_info->rx_buff + 8, packetlen - 8);
      if (!ptr) {
            RecvErr("ARP Packet too short", strip_info);
            return;
      }

      if (ptr < end) {
            RecvErr("ARP Packet too long", strip_info);
            return;
      }

      header->protocol = htons(ETH_P_ARP);

      deliver_packet(strip_info, header, packetlen);
}

/*
 * process_text_message processes a <CR>-terminated block of data received
 * from the radio that doesn't begin with a '*' character. All normal
 * Starmode communication messages with the radio begin with a '*',
 * so any text that does not indicates a serial port error, a radio that
 * is in Hayes command mode instead of Starmode, or a radio with really
 * old firmware that doesn't frame its Starmode responses properly.
 */
static void process_text_message(struct strip *strip_info)
{
      __u8 *msg = strip_info->sx_buff;
      int len = strip_info->sx_count;

      /* Check for anything that looks like it might be our radio name */
      /* (This is here for backwards compatibility with old firmware)  */
      if (len == 9 && get_radio_address(strip_info, msg) == 0)
            return;

      if (text_equal(msg, len, "OK"))
            return;           /* Ignore 'OK' responses from prior commands */
      if (text_equal(msg, len, "ERROR"))
            return;           /* Ignore 'ERROR' messages */
      if (has_prefix(msg, len, "ate0q1"))
            return;           /* Ignore character echo back from the radio */

      /* Catch other error messages */
      /* (This is here for backwards compatibility with old firmware) */
      if (has_prefix(msg, len, "ERR_")) {
            RecvErr_Message(strip_info, NULL, &msg[4], len - 4);
            return;
      }

      RecvErr("No initial *", strip_info);
}

/*
 * process_message processes a <CR>-terminated block of data received
 * from the radio. If the radio is not in Starmode or has old firmware,
 * it may be a line of text in response to an AT command. Ideally, with
 * a current radio that's properly in Starmode, all data received should
 * be properly framed and checksummed radio message blocks, containing
 * either a starmode packet, or a other communication from the radio
 * firmware, like "INF_" Info messages and &COMMAND responses.
 */
static void process_message(struct strip *strip_info)
{
      STRIP_Header header = { zero_address, zero_address, 0 };
      __u8 *ptr = strip_info->sx_buff;
      __u8 *end = strip_info->sx_buff + strip_info->sx_count;
      __u8 sendername[32], *sptr = sendername;
      MetricomKey key;

      /*HexDump("Receiving", strip_info, ptr, end); */

      /* Check for start of address marker, and then skip over it */
      if (*ptr == '*')
            ptr++;
      else {
            process_text_message(strip_info);
            return;
      }

      /* Copy out the return address */
      while (ptr < end && *ptr != '*'
             && sptr < ARRAY_END(sendername) - 1)
            *sptr++ = *ptr++;
      *sptr = 0;        /* Null terminate the sender name */

      /* Check for end of address marker, and skip over it */
      if (ptr >= end || *ptr != '*') {
            RecvErr("No second *", strip_info);
            return;
      }
      ptr++;                  /* Skip the second '*' */

      /* If the sender name is "&COMMAND", ignore this 'packet'       */
      /* (This is here for backwards compatibility with old firmware) */
      if (!strcmp(sendername, "&COMMAND")) {
            strip_info->firmware_level = NoStructure;
            strip_info->next_command = CompatibilityCommand;
            return;
      }

      if (ptr + 4 > end) {
            RecvErr("No proto key", strip_info);
            return;
      }

      /* Get the protocol key out of the buffer */
      key.c[0] = *ptr++;
      key.c[1] = *ptr++;
      key.c[2] = *ptr++;
      key.c[3] = *ptr++;

      /* If we're using checksums, verify the checksum at the end of the packet */
      if (strip_info->firmware_level >= ChecksummedMessages) {
            end -= 4;   /* Chop the last four bytes off the packet (they're the checksum) */
            if (ptr > end) {
                  RecvErr("Missing Checksum", strip_info);
                  return;
            }
            if (!verify_checksum(strip_info)) {
                  RecvErr("Bad Checksum", strip_info);
                  return;
            }
      }

      /*printk(KERN_INFO "%s: Got packet from \"%s\".\n", strip_info->dev->name, sendername); */

      /*
       * Fill in (pseudo) source and destination addresses in the packet.
       * We assume that the destination address was our address (the radio does not
       * tell us this). If the radio supplies a source address, then we use it.
       */
      header.dst_addr = strip_info->true_dev_addr;
      string_to_radio_address(&header.src_addr, sendername);

#ifdef EXT_COUNTERS
      if (key.l == SIP0Key.l) {
            strip_info->rx_rbytes += (end - ptr);
            process_IP_packet(strip_info, &header, ptr, end);
      } else if (key.l == ARP0Key.l) {
            strip_info->rx_rbytes += (end - ptr);
            process_ARP_packet(strip_info, &header, ptr, end);
      } else if (key.l == ATR_Key.l) {
            strip_info->rx_ebytes += (end - ptr);
            process_AT_response(strip_info, ptr, end);
      } else if (key.l == ACK_Key.l) {
            strip_info->rx_ebytes += (end - ptr);
            process_ACK(strip_info, ptr, end);
      } else if (key.l == INF_Key.l) {
            strip_info->rx_ebytes += (end - ptr);
            process_Info(strip_info, ptr, end);
      } else if (key.l == ERR_Key.l) {
            strip_info->rx_ebytes += (end - ptr);
            RecvErr_Message(strip_info, sendername, ptr, end - ptr);
      } else
            RecvErr("Unrecognized protocol key", strip_info);
#else
      if (key.l == SIP0Key.l)
            process_IP_packet(strip_info, &header, ptr, end);
      else if (key.l == ARP0Key.l)
            process_ARP_packet(strip_info, &header, ptr, end);
      else if (key.l == ATR_Key.l)
            process_AT_response(strip_info, ptr, end);
      else if (key.l == ACK_Key.l)
            process_ACK(strip_info, ptr, end);
      else if (key.l == INF_Key.l)
            process_Info(strip_info, ptr, end);
      else if (key.l == ERR_Key.l)
            RecvErr_Message(strip_info, sendername, ptr, end - ptr);
      else
            RecvErr("Unrecognized protocol key", strip_info);
#endif
}

#define TTYERROR(X) ((X) == TTY_BREAK   ? "Break"            : \
                     (X) == TTY_FRAME   ? "Framing Error"    : \
                     (X) == TTY_PARITY  ? "Parity Error"     : \
                     (X) == TTY_OVERRUN ? "Hardware Overrun" : "Unknown Error")

/*
 * Handle the 'receiver data ready' interrupt.
 * This function is called by the 'tty_io' module in the kernel when
 * a block of STRIP data has been received, which can now be decapsulated
 * and sent on to some IP layer for further processing.
 */

static void strip_receive_buf(struct tty_struct *tty, const unsigned char *cp,
              char *fp, int count)
{
      struct strip *strip_info = (struct strip *) tty->disc_data;
      const unsigned char *end = cp + count;

      if (!strip_info || strip_info->magic != STRIP_MAGIC
          || !netif_running(strip_info->dev))
            return;

      spin_lock_bh(&strip_lock);
#if 0
      {
            struct timeval tv;
            do_gettimeofday(&tv);
            printk(KERN_INFO
                   "**** strip_receive_buf: %3d bytes at %02d.%06d\n",
                   count, tv.tv_sec % 100, tv.tv_usec);
      }
#endif

#ifdef EXT_COUNTERS
      strip_info->rx_sbytes += count;
#endif

      /* Read the characters out of the buffer */
      while (cp < end) {
            if (fp && *fp)
                  printk(KERN_INFO "%s: %s on serial port\n",
                         strip_info->dev->name, TTYERROR(*fp));
            if (fp && *fp++ && !strip_info->discard) {      /* If there's a serial error, record it */
                  /* If we have some characters in the buffer, discard them */
                  strip_info->discard = strip_info->sx_count;
                  strip_info->rx_errors++;
            }

            /* Leading control characters (CR, NL, Tab, etc.) are ignored */
            if (strip_info->sx_count > 0 || *cp >= ' ') {
                  if (*cp == 0x0D) {      /* If end of packet, decide what to do with it */
                        if (strip_info->sx_count > 3000)
                              printk(KERN_INFO
                                     "%s: Cut a %d byte packet (%zd bytes remaining)%s\n",
                                     strip_info->dev->name,
                                     strip_info->sx_count,
                                     end - cp - 1,
                                     strip_info->
                                     discard ? " (discarded)" :
                                     "");
                        if (strip_info->sx_count >
                            strip_info->sx_size) {
                              strip_info->rx_over_errors++;
                              printk(KERN_INFO
                                     "%s: sx_buff overflow (%d bytes total)\n",
                                     strip_info->dev->name,
                                     strip_info->sx_count);
                        } else if (strip_info->discard)
                              printk(KERN_INFO
                                     "%s: Discarding bad packet (%d/%d)\n",
                                     strip_info->dev->name,
                                     strip_info->discard,
                                     strip_info->sx_count);
                        else
                              process_message(strip_info);
                        strip_info->discard = 0;
                        strip_info->sx_count = 0;
                  } else {
                        /* Make sure we have space in the buffer */
                        if (strip_info->sx_count <
                            strip_info->sx_size)
                              strip_info->sx_buff[strip_info->
                                              sx_count] =
                                  *cp;
                        strip_info->sx_count++;
                  }
            }
            cp++;
      }
      spin_unlock_bh(&strip_lock);
}


/************************************************************************/
/* General control routines                                 */

static int set_mac_address(struct strip *strip_info,
                     MetricomAddress * addr)
{
      /*
       * We're using a manually specified address if the address is set
       * to anything other than all ones. Setting the address to all ones
       * disables manual mode and goes back to automatic address determination
       * (tracking the true address that the radio has).
       */
      strip_info->manual_dev_addr =
          memcmp(addr->c, broadcast_address.c,
               sizeof(broadcast_address));
      if (strip_info->manual_dev_addr)
            *(MetricomAddress *) strip_info->dev->dev_addr = *addr;
      else
            *(MetricomAddress *) strip_info->dev->dev_addr =
                strip_info->true_dev_addr;
      return 0;
}

static int strip_set_mac_address(struct net_device *dev, void *addr)
{
      struct strip *strip_info = netdev_priv(dev);
      struct sockaddr *sa = addr;
      printk(KERN_INFO "%s: strip_set_dev_mac_address called\n", dev->name);
      set_mac_address(strip_info, (MetricomAddress *) sa->sa_data);
      return 0;
}

static struct net_device_stats *strip_get_stats(struct net_device *dev)
{
      struct strip *strip_info = netdev_priv(dev);
      static struct net_device_stats stats;

      memset(&stats, 0, sizeof(struct net_device_stats));

      stats.rx_packets = strip_info->rx_packets;
      stats.tx_packets = strip_info->tx_packets;
      stats.rx_dropped = strip_info->rx_dropped;
      stats.tx_dropped = strip_info->tx_dropped;
      stats.tx_errors = strip_info->tx_errors;
      stats.rx_errors = strip_info->rx_errors;
      stats.rx_over_errors = strip_info->rx_over_errors;
      return (&stats);
}


/************************************************************************/
/* Opening and closing                                      */

/*
 * Here's the order things happen:
 * When the user runs "slattach -p strip ..."
 *  1. The TTY module calls strip_open;;
 *  2. strip_open calls strip_alloc
 *  3.                  strip_alloc calls register_netdev
 *  4.                  register_netdev calls strip_dev_init
 *  5. then strip_open finishes setting up the strip_info
 *
 * When the user runs "ifconfig st<x> up address netmask ..."
 *  6. strip_open_low gets called
 *
 * When the user runs "ifconfig st<x> down"
 *  7. strip_close_low gets called
 *
 * When the user kills the slattach process
 *  8. strip_close gets called
 *  9. strip_close calls dev_close
 * 10. if the device is still up, then dev_close calls strip_close_low
 * 11. strip_close calls strip_free
 */

/* Open the low-level part of the STRIP channel. Easy! */

static int strip_open_low(struct net_device *dev)
{
      struct strip *strip_info = netdev_priv(dev);

      if (strip_info->tty == NULL)
            return (-ENODEV);

      if (!allocate_buffers(strip_info, dev->mtu))
            return (-ENOMEM);

      strip_info->sx_count = 0;
      strip_info->tx_left = 0;

      strip_info->discard = 0;
      strip_info->working = FALSE;
      strip_info->firmware_level = NoStructure;
      strip_info->next_command = CompatibilityCommand;
      strip_info->user_baud = get_baud(strip_info->tty);

      printk(KERN_INFO "%s: Initializing Radio.\n",
             strip_info->dev->name);
      ResetRadio(strip_info);
      strip_info->idle_timer.expires = jiffies + 1 * HZ;
      add_timer(&strip_info->idle_timer);
      netif_wake_queue(dev);
      return (0);
}


/*
 * Close the low-level part of the STRIP channel. Easy!
 */

static int strip_close_low(struct net_device *dev)
{
      struct strip *strip_info = netdev_priv(dev);

      if (strip_info->tty == NULL)
            return -EBUSY;
      strip_info->tty->flags &= ~(1 << TTY_DO_WRITE_WAKEUP);

      netif_stop_queue(dev);

      /*
       * Free all STRIP frame buffers.
       */
      kfree(strip_info->rx_buff);
      strip_info->rx_buff = NULL;
      kfree(strip_info->sx_buff);
      strip_info->sx_buff = NULL;
      kfree(strip_info->tx_buff);
      strip_info->tx_buff = NULL;

      del_timer(&strip_info->idle_timer);
      return 0;
}

/*
 * This routine is called by DDI when the
 * (dynamically assigned) device is registered
 */

static void strip_dev_setup(struct net_device *dev)
{
      /*
       * Finish setting up the DEVICE info.
       */

      SET_MODULE_OWNER(dev);

      dev->trans_start = 0;
      dev->last_rx = 0;
      dev->tx_queue_len = 30; /* Drop after 30 frames queued */

      dev->flags = 0;
      dev->mtu = DEFAULT_STRIP_MTU;
      dev->type = ARPHRD_METRICOM;  /* dtang */
      dev->hard_header_len = sizeof(STRIP_Header);
      /*
       *  dev->priv             Already holds a pointer to our struct strip
       */

      *(MetricomAddress *) & dev->broadcast = broadcast_address;
      dev->dev_addr[0] = 0;
      dev->addr_len = sizeof(MetricomAddress);

      /*
       * Pointers to interface service routines.
       */

      dev->open = strip_open_low;
      dev->stop = strip_close_low;
      dev->hard_start_xmit = strip_xmit;
      dev->hard_header = strip_header;
      dev->rebuild_header = strip_rebuild_header;
      dev->set_mac_address = strip_set_mac_address;
      dev->get_stats = strip_get_stats;
      dev->change_mtu = strip_change_mtu;
}

/*
 * Free a STRIP channel.
 */

static void strip_free(struct strip *strip_info)
{
      spin_lock_bh(&strip_lock);
      list_del_rcu(&strip_info->list);
      spin_unlock_bh(&strip_lock);

      strip_info->magic = 0;

      free_netdev(strip_info->dev);
}


/*
 * Allocate a new free STRIP channel
 */
static struct strip *strip_alloc(void)
{
      struct list_head *n;
      struct net_device *dev;
      struct strip *strip_info;

      dev = alloc_netdev(sizeof(struct strip), "st%d",
                     strip_dev_setup);

      if (!dev)
            return NULL;      /* If no more memory, return */


      strip_info = dev->priv;
      strip_info->dev = dev;

      strip_info->magic = STRIP_MAGIC;
      strip_info->tty = NULL;

      strip_info->gratuitous_arp = jiffies + LongTime;
      strip_info->arp_interval = 0;
      init_timer(&strip_info->idle_timer);
      strip_info->idle_timer.data = (long) dev;
      strip_info->idle_timer.function = strip_IdleTask;


      spin_lock_bh(&strip_lock);
 rescan:
      /*
       * Search the list to find where to put our new entry
       * (and in the process decide what channel number it is
       * going to be)
       */
      list_for_each(n, &strip_list) {
            struct strip *s = hlist_entry(n, struct strip, list);

            if (s->dev->base_addr == dev->base_addr) {
                  ++dev->base_addr;
                  goto rescan;
            }
      }

      sprintf(dev->name, "st%ld", dev->base_addr);

      list_add_tail_rcu(&strip_info->list, &strip_list);
      spin_unlock_bh(&strip_lock);

      return strip_info;
}

/*
 * Open the high-level part of the STRIP channel.
 * This function is called by the TTY module when the
 * STRIP line discipline is called for.  Because we are
 * sure the tty line exists, we only have to link it to
 * a free STRIP channel...
 */

static int strip_open(struct tty_struct *tty)
{
      struct strip *strip_info = (struct strip *) tty->disc_data;

      /*
       * First make sure we're not already connected.
       */

      if (strip_info && strip_info->magic == STRIP_MAGIC)
            return -EEXIST;

      /*
       * OK.  Find a free STRIP channel to use.
       */
      if ((strip_info = strip_alloc()) == NULL)
            return -ENFILE;

      /*
       * Register our newly created device so it can be ifconfig'd
       * strip_dev_init() will be called as a side-effect
       */

      if (register_netdev(strip_info->dev) != 0) {
            printk(KERN_ERR "strip: register_netdev() failed.\n");
            strip_free(strip_info);
            return -ENFILE;
      }

      strip_info->tty = tty;
      tty->disc_data = strip_info;
      tty->receive_room = 65536;

      if (tty->driver->flush_buffer)
            tty->driver->flush_buffer(tty);

      /*
       * Restore default settings
       */

      strip_info->dev->type = ARPHRD_METRICOM;  /* dtang */

      /*
       * Set tty options
       */

      tty->termios->c_iflag |= IGNBRK | IGNPAR; /* Ignore breaks and parity errors. */
      tty->termios->c_cflag |= CLOCAL;    /* Ignore modem control signals. */
      tty->termios->c_cflag &= ~HUPCL;    /* Don't close on hup */

      printk(KERN_INFO "STRIP: device \"%s\" activated\n",
             strip_info->dev->name);

      /*
       * Done.  We have linked the TTY line to a channel.
       */
      return (strip_info->dev->base_addr);
}

/*
 * Close down a STRIP channel.
 * This means flushing out any pending queues, and then restoring the
 * TTY line discipline to what it was before it got hooked to STRIP
 * (which usually is TTY again).
 */

static void strip_close(struct tty_struct *tty)
{
      struct strip *strip_info = (struct strip *) tty->disc_data;

      /*
       * First make sure we're connected.
       */

      if (!strip_info || strip_info->magic != STRIP_MAGIC)
            return;

      unregister_netdev(strip_info->dev);

      tty->disc_data = NULL;
      strip_info->tty = NULL;
      printk(KERN_INFO "STRIP: device \"%s\" closed down\n",
             strip_info->dev->name);
      strip_free(strip_info);
      tty->disc_data = NULL;
}


/************************************************************************/
/* Perform I/O control calls on an active STRIP channel.          */

static int strip_ioctl(struct tty_struct *tty, struct file *file,
                   unsigned int cmd, unsigned long arg)
{
      struct strip *strip_info = (struct strip *) tty->disc_data;

      /*
       * First make sure we're connected.
       */

      if (!strip_info || strip_info->magic != STRIP_MAGIC)
            return -EINVAL;

      switch (cmd) {
      case SIOCGIFNAME:
            if(copy_to_user((void __user *) arg, strip_info->dev->name, strlen(strip_info->dev->name) + 1))
                  return -EFAULT;
            break;
      case SIOCSIFHWADDR:
      {
            MetricomAddress addr;
            //printk(KERN_INFO "%s: SIOCSIFHWADDR\n", strip_info->dev->name);
            if(copy_from_user(&addr, (void __user *) arg, sizeof(MetricomAddress)))
                  return -EFAULT;
            return set_mac_address(strip_info, &addr);
      }
      /*
       * Allow stty to read, but not set, the serial port
       */

      case TCGETS:
      case TCGETA:
            return n_tty_ioctl(tty, file, cmd, arg);
            break;
      default:
            return -ENOIOCTLCMD;
            break;
      }
      return 0;
}


/************************************************************************/
/* Initialization                                     */

static struct tty_ldisc strip_ldisc = {
      .magic = TTY_LDISC_MAGIC,
      .name = "strip",
      .owner = THIS_MODULE,
      .open = strip_open,
      .close = strip_close,
      .ioctl = strip_ioctl,
      .receive_buf = strip_receive_buf,
      .write_wakeup = strip_write_some_more,
};

/*
 * Initialize the STRIP driver.
 * This routine is called at boot time, to bootstrap the multi-channel
 * STRIP driver
 */

static char signon[] __initdata =
    KERN_INFO "STRIP: Version %s (unlimited channels)\n";

static int __init strip_init_driver(void)
{
      int status;

      printk(signon, StripVersion);

      
      /*
       * Fill in our line protocol discipline, and register it
       */
      if ((status = tty_register_ldisc(N_STRIP, &strip_ldisc)))
            printk(KERN_ERR "STRIP: can't register line discipline (err = %d)\n",
                   status);

      /*
       * Register the status file with /proc
       */
      proc_net_fops_create("strip", S_IFREG | S_IRUGO, &strip_seq_fops);

      return status;
}

module_init(strip_init_driver);

static const char signoff[] __exitdata =
    KERN_INFO "STRIP: Module Unloaded\n";

static void __exit strip_exit_driver(void)
{
      int i;
      struct list_head *p,*n;

      /* module ref count rules assure that all entries are unregistered */
      list_for_each_safe(p, n, &strip_list) {
            struct strip *s = list_entry(p, struct strip, list);
            strip_free(s);
      }

      /* Unregister with the /proc/net file here. */
      proc_net_remove("strip");

      if ((i = tty_unregister_ldisc(N_STRIP)))
            printk(KERN_ERR "STRIP: can't unregister line discipline (err = %d)\n", i);

      printk(signoff);
}

module_exit(strip_exit_driver);

MODULE_AUTHOR("Stuart Cheshire <cheshire@cs.stanford.edu>");
MODULE_DESCRIPTION("Starmode Radio IP (STRIP) Device Driver");
MODULE_LICENSE("Dual BSD/GPL");

MODULE_SUPPORTED_DEVICE("Starmode Radio IP (STRIP) modem");

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