usr.sbin/ppp/hdlc.c

   1 /*-
   2  * Copyright (c) 1996 - 2001 Brian Somers <brian@Awfulhak.org>
   3  *          based on work by Toshiharu OHNO <tony-o@iij.ad.jp>
   4  *                           Internet Initiative Japan, Inc (IIJ)
   5  * All rights reserved.
   6  *
   7  * Redistribution and use in source and binary forms, with or without
   8  * modification, are permitted provided that the following conditions
   9  * are met:
  10  * 1. Redistributions of source code must retain the above copyright
  11  *    notice, this list of conditions and the following disclaimer.
  12  * 2. Redistributions in binary form must reproduce the above copyright
  13  *    notice, this list of conditions and the following disclaimer in the
  14  *    documentation and/or other materials provided with the distribution.
  15  *
  16  * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
  17  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  18  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
  19  * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
  20  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
  21  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
  22  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
  23  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
  24  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
  25  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  26  * SUCH DAMAGE.
  27  *
  28  * $FreeBSD: src/usr.sbin/ppp/hdlc.c,v 1.46.2.2 2002/09/01 02:12:27 brian Exp $
  29  */
  30
  31 #include <sys/param.h>
  32 #include <sys/un.h>
  33
  34 #include <stdarg.h>
  35 #include <stdio.h>
  36 #include <string.h>
  37 #include <termios.h>
  38
  39 #include "defs.h"
  40 #include "layer.h"
  41 #include "command.h"
  42 #include "mbuf.h"
  43 #include "log.h"
  44 #include "timer.h"
  45 #include "fsm.h"
  46 #include "lqr.h"
  47 #include "hdlc.h"
  48 #include "throughput.h"
  49 #include "auth.h"
  50 #include "lcp.h"
  51 #include "async.h"
  52 #include "ccp.h"
  53 #include "link.h"
  54 #include "descriptor.h"
  55 #include "chap.h"
  56 #include "physical.h"
  57 #include "prompt.h"
  58 #include "chat.h"
  59 #include "mp.h"
  60 #include "cbcp.h"
  61 #include "datalink.h"
  62
  63 static u_int16_t const fcstab[256] = {
  64    /* 00 */ 0x0000, 0x1189, 0x2312, 0x329b, 0x4624, 0x57ad, 0x6536, 0x74bf,
  65    /* 08 */ 0x8c48, 0x9dc1, 0xaf5a, 0xbed3, 0xca6c, 0xdbe5, 0xe97e, 0xf8f7,
  66    /* 10 */ 0x1081, 0x0108, 0x3393, 0x221a, 0x56a5, 0x472c, 0x75b7, 0x643e,
  67    /* 18 */ 0x9cc9, 0x8d40, 0xbfdb, 0xae52, 0xdaed, 0xcb64, 0xf9ff, 0xe876,
  68    /* 20 */ 0x2102, 0x308b, 0x0210, 0x1399, 0x6726, 0x76af, 0x4434, 0x55bd,
  69    /* 28 */ 0xad4a, 0xbcc3, 0x8e58, 0x9fd1, 0xeb6e, 0xfae7, 0xc87c, 0xd9f5,
  70    /* 30 */ 0x3183, 0x200a, 0x1291, 0x0318, 0x77a7, 0x662e, 0x54b5, 0x453c,
  71    /* 38 */ 0xbdcb, 0xac42, 0x9ed9, 0x8f50, 0xfbef, 0xea66, 0xd8fd, 0xc974,
  72    /* 40 */ 0x4204, 0x538d, 0x6116, 0x709f, 0x0420, 0x15a9, 0x2732, 0x36bb,
  73    /* 48 */ 0xce4c, 0xdfc5, 0xed5e, 0xfcd7, 0x8868, 0x99e1, 0xab7a, 0xbaf3,
  74    /* 50 */ 0x5285, 0x430c, 0x7197, 0x601e, 0x14a1, 0x0528, 0x37b3, 0x263a,
  75    /* 58 */ 0xdecd, 0xcf44, 0xfddf, 0xec56, 0x98e9, 0x8960, 0xbbfb, 0xaa72,
  76    /* 60 */ 0x6306, 0x728f, 0x4014, 0x519d, 0x2522, 0x34ab, 0x0630, 0x17b9,
  77    /* 68 */ 0xef4e, 0xfec7, 0xcc5c, 0xddd5, 0xa96a, 0xb8e3, 0x8a78, 0x9bf1,
  78    /* 70 */ 0x7387, 0x620e, 0x5095, 0x411c, 0x35a3, 0x242a, 0x16b1, 0x0738,
  79    /* 78 */ 0xffcf, 0xee46, 0xdcdd, 0xcd54, 0xb9eb, 0xa862, 0x9af9, 0x8b70,
  80    /* 80 */ 0x8408, 0x9581, 0xa71a, 0xb693, 0xc22c, 0xd3a5, 0xe13e, 0xf0b7,
  81    /* 88 */ 0x0840, 0x19c9, 0x2b52, 0x3adb, 0x4e64, 0x5fed, 0x6d76, 0x7cff,
  82    /* 90 */ 0x9489, 0x8500, 0xb79b, 0xa612, 0xd2ad, 0xc324, 0xf1bf, 0xe036,
  83    /* 98 */ 0x18c1, 0x0948, 0x3bd3, 0x2a5a, 0x5ee5, 0x4f6c, 0x7df7, 0x6c7e,
  84    /* a0 */ 0xa50a, 0xb483, 0x8618, 0x9791, 0xe32e, 0xf2a7, 0xc03c, 0xd1b5,
  85    /* a8 */ 0x2942, 0x38cb, 0x0a50, 0x1bd9, 0x6f66, 0x7eef, 0x4c74, 0x5dfd,
  86    /* b0 */ 0xb58b, 0xa402, 0x9699, 0x8710, 0xf3af, 0xe226, 0xd0bd, 0xc134,
  87    /* b8 */ 0x39c3, 0x284a, 0x1ad1, 0x0b58, 0x7fe7, 0x6e6e, 0x5cf5, 0x4d7c,
  88    /* c0 */ 0xc60c, 0xd785, 0xe51e, 0xf497, 0x8028, 0x91a1, 0xa33a, 0xb2b3,
  89    /* c8 */ 0x4a44, 0x5bcd, 0x6956, 0x78df, 0x0c60, 0x1de9, 0x2f72, 0x3efb,
  90    /* d0 */ 0xd68d, 0xc704, 0xf59f, 0xe416, 0x90a9, 0x8120, 0xb3bb, 0xa232,
  91    /* d8 */ 0x5ac5, 0x4b4c, 0x79d7, 0x685e, 0x1ce1, 0x0d68, 0x3ff3, 0x2e7a,
  92    /* e0 */ 0xe70e, 0xf687, 0xc41c, 0xd595, 0xa12a, 0xb0a3, 0x8238, 0x93b1,
  93    /* e8 */ 0x6b46, 0x7acf, 0x4854, 0x59dd, 0x2d62, 0x3ceb, 0x0e70, 0x1ff9,
  94    /* f0 */ 0xf78f, 0xe606, 0xd49d, 0xc514, 0xb1ab, 0xa022, 0x92b9, 0x8330,
  95    /* f8 */ 0x7bc7, 0x6a4e, 0x58d5, 0x495c, 0x3de3, 0x2c6a, 0x1ef1, 0x0f78
  96 };
  97
  98 void
  99 hdlc_Init(struct hdlc *hdlc, struct lcp *lcp)
 100 {
 101   memset(hdlc, '\0', sizeof(struct hdlc));
 102   hdlc->lqm.owner = lcp;
 103 }
 104
 105 /*
 106  *  HDLC FCS computation. Read RFC 1171 Appendix B and CCITT X.25 section
 107  *  2.27 for further details.
 108  */
 109 u_short
 110 hdlc_Fcs(u_char *cp, size_t len)
 111 {
 112   u_short fcs = INITFCS;
 113
 114   while (len--)
 115     fcs = (fcs >> 8) ^ fcstab[(fcs ^ *cp++) & 0xff];
 116
 117   return fcs;
 118 }
 119
 120 static inline u_short
 121 HdlcFcsBuf(u_short fcs, struct mbuf *m)
 122 {
 123   int len;
 124   u_char *pos, *end;
 125
 126   len = m_length(m);
 127   pos = MBUF_CTOP(m);
 128   end = pos + m->m_len;
 129   while (len--) {
 130     fcs = (fcs >> 8) ^ fcstab[(fcs ^ *pos++) & 0xff];
 131     if (pos == end && len) {
 132       m = m->m_next;
 133       pos = MBUF_CTOP(m);
 134       end = pos + m->m_len;
 135     }
 136   }
 137   return (fcs);
 138 }
 139
 140 static struct mbuf *
 141 hdlc_LayerPush(struct bundle *bundle __unused, struct link *l __unused,
 142                struct mbuf *bp, int pri __unused, u_short *proto __unused)
 143 {
 144   struct mbuf *last;
 145   u_char *cp;
 146   u_short fcs;
 147
 148   m_settype(bp, MB_HDLCOUT);
 149   fcs = HdlcFcsBuf(INITFCS, bp);
 150   fcs = ~fcs;
 151
 152   for (last = bp; last->m_next; last = last->m_next)
 153     ;
 154
 155   if (last->m_size - last->m_offset - last->m_len >= 2) {
 156     cp = MBUF_CTOP(last) + last->m_len;
 157     last->m_len += 2;
 158   } else {
 159     struct mbuf *tail = m_get(2, MB_HDLCOUT);
 160     last->m_next = tail;
 161     cp = MBUF_CTOP(tail);
 162   }
 163
 164   *cp++ = fcs & 0377;           /* Low byte first (nothing like consistency) */
 165   *cp++ = fcs >> 8;
 166
 167   log_DumpBp(LogHDLC, "hdlc_Output", bp);
 168
 169   return bp;
 170 }
 171
 172 /* Check out the latest ``Assigned numbers'' rfc (rfc1700.txt) */
 173 static struct {
 174   u_short from;
 175   u_short to;
 176   const char *name;
 177 } protocols[] = {
 178   { 0x0001, 0x0001, "Padding Protocol" },
 179   { 0x0003, 0x001f, "reserved (transparency inefficient)" },
 180   { 0x0021, 0x0021, "Internet Protocol" },
 181   { 0x0023, 0x0023, "OSI Network Layer" },
 182   { 0x0025, 0x0025, "Xerox NS IDP" },
 183   { 0x0027, 0x0027, "DECnet Phase IV" },
 184   { 0x0029, 0x0029, "Appletalk" },
 185   { 0x002b, 0x002b, "Novell IPX" },
 186   { 0x002d, 0x002d, "Van Jacobson Compressed TCP/IP" },
 187   { 0x002f, 0x002f, "Van Jacobson Uncompressed TCP/IP" },
 188   { 0x0031, 0x0031, "Bridging PDU" },
 189   { 0x0033, 0x0033, "Stream Protocol (ST-II)" },
 190   { 0x0035, 0x0035, "Banyan Vines" },
 191   { 0x0037, 0x0037, "reserved (until 1993)" },
 192   { 0x0039, 0x0039, "AppleTalk EDDP" },
 193   { 0x003b, 0x003b, "AppleTalk SmartBuffered" },
 194   { 0x003d, 0x003d, "Multi-Link" },
 195   { 0x003f, 0x003f, "NETBIOS Framing" },
 196   { 0x0041, 0x0041, "Cisco Systems" },
 197   { 0x0043, 0x0043, "Ascom Timeplex" },
 198   { 0x0045, 0x0045, "Fujitsu Link Backup and Load Balancing (LBLB)" },
 199   { 0x0047, 0x0047, "DCA Remote Lan" },
 200   { 0x0049, 0x0049, "Serial Data Transport Protocol (PPP-SDTP)" },
 201   { 0x004b, 0x004b, "SNA over 802.2" },
 202   { 0x004d, 0x004d, "SNA" },
 203   { 0x004f, 0x004f, "IP6 Header Compression" },
 204   { 0x0051, 0x0051, "KNX Bridging Data" },
 205   { 0x0053, 0x0053, "Encryption" },
 206   { 0x0055, 0x0055, "Individual Link Encryption" },
 207   { 0x0057, 0x0057, "Internet Protocol V6" },
 208   { 0x006f, 0x006f, "Stampede Bridging" },
 209   { 0x0071, 0x0071, "BAP Bandwidth Allocation Protocol" },
 210   { 0x0073, 0x0073, "MP+ Protocol" },
 211   { 0x007d, 0x007d, "reserved (Control Escape)" },
 212   { 0x007f, 0x007f, "reserved (compression inefficient)" },
 213   { 0x00cf, 0x00cf, "reserved (PPP NLPID)" },
 214   { 0x00fb, 0x00fb, "compression on single link in multilink group" },
 215   { 0x00fd, 0x00fd, "1st choice compression" },
 216   { 0x00ff, 0x00ff, "reserved (compression inefficient)" },
 217   { 0x0200, 0x02ff, "(compression inefficient)" },
 218   { 0x0201, 0x0201, "802.1d Hello Packets" },
 219   { 0x0203, 0x0203, "IBM Source Routing BPDU" },
 220   { 0x0205, 0x0205, "DEC LANBridge100 Spanning Tree" },
 221   { 0x0207, 0x0207, "Cisco Discovery Protocol" },
 222   { 0x0209, 0x0209, "Netcs Twin Routing" },
 223   { 0x0231, 0x0231, "Luxcom" },
 224   { 0x0233, 0x0233, "Sigma Network Systems" },
 225   { 0x0235, 0x0235, "Apple Client Server Protocol" },
 226   { 0x1e00, 0x1eff, "(compression inefficient)" },
 227   { 0x4001, 0x4001, "Cray Communications Control Protocol" },
 228   { 0x4003, 0x4003, "CDPD Mobile Network Registration Protocol" },
 229   { 0x4021, 0x4021, "Stacker LZS" },
 230   { 0x8001, 0x801f, "Not Used - reserved" },
 231   { 0x8021, 0x8021, "Internet Protocol Control Protocol" },
 232   { 0x8023, 0x8023, "OSI Network Layer Control Protocol" },
 233   { 0x8025, 0x8025, "Xerox NS IDP Control Protocol" },
 234   { 0x8027, 0x8027, "DECnet Phase IV Control Protocol" },
 235   { 0x8029, 0x8029, "Appletalk Control Protocol" },
 236   { 0x802b, 0x802b, "Novell IPX Control Protocol" },
 237   { 0x802d, 0x802d, "reserved" },
 238   { 0x802f, 0x802f, "reserved" },
 239   { 0x8031, 0x8031, "Bridging NCP" },
 240   { 0x8033, 0x8033, "Stream Protocol Control Protocol" },
 241   { 0x8035, 0x8035, "Banyan Vines Control Protocol" },
 242   { 0x8037, 0x8037, "reserved till 1993" },
 243   { 0x8039, 0x8039, "reserved" },
 244   { 0x803b, 0x803b, "reserved" },
 245   { 0x803d, 0x803d, "Multi-Link Control Protocol" },
 246   { 0x803f, 0x803f, "NETBIOS Framing Control Protocol" },
 247   { 0x8041, 0x8041, "Cisco Systems Control Protocol" },
 248   { 0x8043, 0x8043, "Ascom Timeplex" },
 249   { 0x8045, 0x8045, "Fujitsu LBLB Control Protocol" },
 250   { 0x8047, 0x8047, "DCA Remote Lan Network Control Protocol (RLNCP)" },
 251   { 0x8049, 0x8049, "Serial Data Control Protocol (PPP-SDCP)" },
 252   { 0x804b, 0x804b, "SNA over 802.2 Control Protocol" },
 253   { 0x804d, 0x804d, "SNA Control Protocol" },
 254   { 0x804f, 0x804f, "IP6 Header Compression Control Protocol" },
 255   { 0x8051, 0x8051, "KNX Bridging Control Protocol" },
 256   { 0x8053, 0x8053, "Encryption Control Protocol" },
 257   { 0x8055, 0x8055, "Individual Link Encryption Control Protocol" },
 258   { 0x8057, 0x8057, "Internet Protocol V6 Control Protocol" },
 259   { 0x806f, 0x806f, "Stampede Bridging Control Protocol" },
 260   { 0x8073, 0x8073, "MP+ Control Protocol" },
 261   { 0x8071, 0x8071, "BACP Bandwidth Allocation Control Protocol" },
 262   { 0x807d, 0x807d, "Not Used - reserved" },
 263   { 0x80cf, 0x80cf, "Not Used - reserved" },
 264   { 0x80fb, 0x80fb, "compression on single link in multilink group control" },
 265   { 0x80fd, 0x80fd, "Compression Control Protocol" },
 266   { 0x80ff, 0x80ff, "Not Used - reserved" },
 267   { 0x8207, 0x8207, "Cisco Discovery Protocol Control" },
 268   { 0x8209, 0x8209, "Netcs Twin Routing" },
 269   { 0x8235, 0x8235, "Apple Client Server Protocol Control" },
 270   { 0xc021, 0xc021, "Link Control Protocol" },
 271   { 0xc023, 0xc023, "Password Authentication Protocol" },
 272   { 0xc025, 0xc025, "Link Quality Report" },
 273   { 0xc027, 0xc027, "Shiva Password Authentication Protocol" },
 274   { 0xc029, 0xc029, "CallBack Control Protocol (CBCP)" },
 275   { 0xc081, 0xc081, "Container Control Protocol" },
 276   { 0xc223, 0xc223, "Challenge Handshake Authentication Protocol" },
 277   { 0xc225, 0xc225, "RSA Authentication Protocol" },
 278   { 0xc227, 0xc227, "Extensible Authentication Protocol" },
 279   { 0xc26f, 0xc26f, "Stampede Bridging Authorization Protocol" },
 280   { 0xc281, 0xc281, "Proprietary Authentication Protocol" },
 281   { 0xc283, 0xc283, "Proprietary Authentication Protocol" },
 282   { 0xc481, 0xc481, "Proprietary Node ID Authentication Protocol" }
 283 };
 284
 285 #define NPROTOCOLS NELEM(protocols)
 286
 287 const char *
 288 hdlc_Protocol2Nam(u_short proto)
 289 {
 290   unsigned f;
 291
 292   for (f = 0; f < NPROTOCOLS; f++)
 293     if (proto >= protocols[f].from && proto <= protocols[f].to)
 294       return protocols[f].name;
 295     else if (proto < protocols[f].from)
 296       break;
 297   return "unrecognised protocol";
 298 }
 299
 300 static struct mbuf *
 301 hdlc_LayerPull(struct bundle *b __unused, struct link *l, struct mbuf *bp,
 302                u_short *proto __unused)
 303 {
 304   struct physical *p = link2physical(l);
 305   u_short fcs;
 306   int len;
 307
 308   if (!p) {
 309     log_Printf(LogERROR, "Can't Pull a hdlc packet from a logical link\n");
 310     return bp;
 311   }
 312
 313   log_DumpBp(LogHDLC, "hdlc_LayerPull:", bp);
 314
 315   fcs = hdlc_Fcs(MBUF_CTOP(bp), bp->m_len);
 316
 317   log_Printf(LogDEBUG, "%s: hdlc_LayerPull: fcs = %04x (%s)\n",
 318              p->link.name, fcs, (fcs == GOODFCS) ? "good" : "BAD!");
 319
 320   if (fcs != GOODFCS) {
 321     p->hdlc.lqm.SaveInErrors++;
 322     p->hdlc.stats.badfcs++;
 323     m_freem(bp);
 324     return NULL;
 325   }
 326
 327   p->hdlc.lqm.SaveInOctets += bp->m_len + 1;
 328   p->hdlc.lqm.SaveInPackets++;
 329
 330   len = m_length(bp);
 331   if (len < 4) {                        /* rfc1662 section 4.3 */
 332     m_freem(bp);
 333     bp = NULL;
 334   }
 335
 336   bp = m_adj(bp, -2);                   /* discard the FCS */
 337   m_settype(bp, MB_HDLCIN);
 338
 339   return bp;
 340 }
 341
 342 /* Detect a HDLC frame */
 343
 344 static const struct frameheader {
 345   const u_char *data;
 346   int len;
 347 } FrameHeaders[] = {
 348   { "\176\377\003\300\041", 5 },
 349   { "\176\377\175\043\300\041", 6 },
 350   { "\176\177\175\043\100\041", 6 },
 351   { "\176\175\337\175\043\300\041", 7 },
 352   { "\176\175\137\175\043\100\041", 7 },
 353   { NULL, 0 }
 354 };
 355
 356 int
 357 hdlc_Detect(u_char const **cp, unsigned n, int issync)
 358 {
 359   const struct frameheader *fh;
 360   const u_char *h;
 361   size_t len, cmp;
 362
 363   while (n) {
 364     for (fh = FrameHeaders; fh->len; fh++) {
 365       h = issync ? fh->data + 1 : fh->data;
 366       len = issync ? fh->len - 1 : fh->len;
 367       cmp = n >= len ? len : n;
 368       if (memcmp(*cp, h, cmp) == 0)
 369         return cmp == len;
 370     }
 371     n--;
 372     (*cp)++;
 373   }
 374
 375   return 0;
 376 }
 377
 378 int
 379 hdlc_ReportStatus(struct cmdargs const *arg)
 380 {
 381   struct hdlc *hdlc = &arg->cx->physical->hdlc;
 382
 383   prompt_Printf(arg->prompt, "%s HDLC level errors:\n", arg->cx->name);
 384   prompt_Printf(arg->prompt, " Bad Frame Check Sequence fields: %u\n",
 385                 hdlc->stats.badfcs);
 386   prompt_Printf(arg->prompt, " Bad address (!= 0x%02x) fields:    %u\n",
 387                 HDLC_ADDR, hdlc->stats.badaddr);
 388   prompt_Printf(arg->prompt, " Bad command (!= 0x%02x) fields:    %u\n",
 389                 HDLC_UI, hdlc->stats.badcommand);
 390   prompt_Printf(arg->prompt, " Unrecognised protocol fields:    %u\n",
 391                 hdlc->stats.unknownproto);
 392   return 0;
 393 }
 394
 395 static void
 396 hdlc_ReportTime(void *v)
 397 {
 398   /* Moan about HDLC errors */
 399   struct hdlc *hdlc = (struct hdlc *)v;
 400
 401   timer_Stop(&hdlc->ReportTimer);
 402
 403   if (memcmp(&hdlc->laststats, &hdlc->stats, sizeof hdlc->stats)) {
 404     log_Printf(LogPHASE,
 405               "%s: HDLC errors -> FCS: %u, ADDR: %u, COMD: %u, PROTO: %u\n",
 406               hdlc->lqm.owner->fsm.link->name,
 407               hdlc->stats.badfcs - hdlc->laststats.badfcs,
 408               hdlc->stats.badaddr - hdlc->laststats.badaddr,
 409               hdlc->stats.badcommand - hdlc->laststats.badcommand,
 410               hdlc->stats.unknownproto - hdlc->laststats.unknownproto);
 411     hdlc->laststats = hdlc->stats;
 412   }
 413
 414   timer_Start(&hdlc->ReportTimer);
 415 }
 416
 417 void
 418 hdlc_StartTimer(struct hdlc *hdlc)
 419 {
 420   timer_Stop(&hdlc->ReportTimer);
 421   hdlc->ReportTimer.load = 60 * SECTICKS;
 422   hdlc->ReportTimer.arg = hdlc;
 423   hdlc->ReportTimer.func = hdlc_ReportTime;
 424   hdlc->ReportTimer.name = "hdlc";
 425   timer_Start(&hdlc->ReportTimer);
 426 }
 427
 428 void
 429 hdlc_StopTimer(struct hdlc *hdlc)
 430 {
 431   timer_Stop(&hdlc->ReportTimer);
 432 }
 433
 434 struct layer hdlclayer = { LAYER_HDLC, "hdlc", hdlc_LayerPush, hdlc_LayerPull };