hdlc.c revision 34494 
1/*
2 *	     PPP High Level Link Control (HDLC) Module
3 *
4 *	    Written by Toshiharu OHNO (tony-o@iij.ad.jp)
5 *
6 *   Copyright (C) 1993, Internet Initiative Japan, Inc. All rights reserverd.
7 *
8 * Redistribution and use in source and binary forms are permitted
9 * provided that the above copyright notice and this paragraph are
10 * duplicated in all such forms and that any documentation,
11 * advertising materials, and other materials related to such
12 * distribution and use acknowledge that the software was developed
13 * by the Internet Initiative Japan, Inc.  The name of the
14 * IIJ may not be used to endorse or promote products derived
15 * from this software without specific prior written permission.
16 * THIS SOFTWARE IS PROVIDED ``AS IS'' AND WITHOUT ANY EXPRESS OR
17 * IMPLIED WARRANTIES, INCLUDING, WITHOUT LIMITATION, THE IMPLIED
18 * WARRANTIES OF MERCHANTIBILITY AND FITNESS FOR A PARTICULAR PURPOSE.
19 *
20 * $Id: hdlc.c,v 1.28 1998/01/21 02:15:15 brian Exp $
21 *
22 *	TODO:
23 */
24#include <sys/param.h>
25#include <netinet/in.h>
26
27#include <stdio.h>
28#include <string.h>
29#include <termios.h>
30
31#include "command.h"
32#include "mbuf.h"
33#include "log.h"
34#include "defs.h"
35#include "timer.h"
36#include "fsm.h"
37#include "hdlc.h"
38#include "lcpproto.h"
39#include "ipcp.h"
40#include "ip.h"
41#include "vjcomp.h"
42#include "pap.h"
43#include "chap.h"
44#include "lcp.h"
45#include "async.h"
46#include "lqr.h"
47#include "loadalias.h"
48#include "vars.h"
49#include "modem.h"
50#include "ccp.h"
51
52static struct hdlcstat {
53  int badfcs;
54  int badaddr;
55  int badcommand;
56  int unknownproto;
57}        HdlcStat;
58
59static u_int32_t ifOutPackets;
60static u_int32_t ifOutOctets;
61static u_int32_t ifOutLQRs;
62
63static struct protostat {
64  u_short number;
65  const char *name;
66  u_long in_count;
67  u_long out_count;
68} ProtocolStat[] = {
69  { PROTO_IP, "IP" },
70  { PROTO_VJUNCOMP, "VJ_UNCOMP" },
71  { PROTO_VJCOMP, "VJ_COMP" },
72  { PROTO_COMPD, "COMPD" },
73  { PROTO_LCP, "LCP" },
74  { PROTO_IPCP, "IPCP" },
75  { PROTO_CCP, "CCP" },
76  { PROTO_PAP, "PAP" },
77  { PROTO_LQR, "LQR" },
78  { PROTO_CHAP, "CHAP" },
79  { 0, "Others" }
80};
81
82static u_short const fcstab[256] = {
83   /* 00 */ 0x0000, 0x1189, 0x2312, 0x329b, 0x4624, 0x57ad, 0x6536, 0x74bf,
84   /* 08 */ 0x8c48, 0x9dc1, 0xaf5a, 0xbed3, 0xca6c, 0xdbe5, 0xe97e, 0xf8f7,
85   /* 10 */ 0x1081, 0x0108, 0x3393, 0x221a, 0x56a5, 0x472c, 0x75b7, 0x643e,
86   /* 18 */ 0x9cc9, 0x8d40, 0xbfdb, 0xae52, 0xdaed, 0xcb64, 0xf9ff, 0xe876,
87   /* 20 */ 0x2102, 0x308b, 0x0210, 0x1399, 0x6726, 0x76af, 0x4434, 0x55bd,
88   /* 28 */ 0xad4a, 0xbcc3, 0x8e58, 0x9fd1, 0xeb6e, 0xfae7, 0xc87c, 0xd9f5,
89   /* 30 */ 0x3183, 0x200a, 0x1291, 0x0318, 0x77a7, 0x662e, 0x54b5, 0x453c,
90   /* 38 */ 0xbdcb, 0xac42, 0x9ed9, 0x8f50, 0xfbef, 0xea66, 0xd8fd, 0xc974,
91   /* 40 */ 0x4204, 0x538d, 0x6116, 0x709f, 0x0420, 0x15a9, 0x2732, 0x36bb,
92   /* 48 */ 0xce4c, 0xdfc5, 0xed5e, 0xfcd7, 0x8868, 0x99e1, 0xab7a, 0xbaf3,
93   /* 50 */ 0x5285, 0x430c, 0x7197, 0x601e, 0x14a1, 0x0528, 0x37b3, 0x263a,
94   /* 58 */ 0xdecd, 0xcf44, 0xfddf, 0xec56, 0x98e9, 0x8960, 0xbbfb, 0xaa72,
95   /* 60 */ 0x6306, 0x728f, 0x4014, 0x519d, 0x2522, 0x34ab, 0x0630, 0x17b9,
96   /* 68 */ 0xef4e, 0xfec7, 0xcc5c, 0xddd5, 0xa96a, 0xb8e3, 0x8a78, 0x9bf1,
97   /* 70 */ 0x7387, 0x620e, 0x5095, 0x411c, 0x35a3, 0x242a, 0x16b1, 0x0738,
98   /* 78 */ 0xffcf, 0xee46, 0xdcdd, 0xcd54, 0xb9eb, 0xa862, 0x9af9, 0x8b70,
99   /* 80 */ 0x8408, 0x9581, 0xa71a, 0xb693, 0xc22c, 0xd3a5, 0xe13e, 0xf0b7,
100   /* 88 */ 0x0840, 0x19c9, 0x2b52, 0x3adb, 0x4e64, 0x5fed, 0x6d76, 0x7cff,
101   /* 90 */ 0x9489, 0x8500, 0xb79b, 0xa612, 0xd2ad, 0xc324, 0xf1bf, 0xe036,
102   /* 98 */ 0x18c1, 0x0948, 0x3bd3, 0x2a5a, 0x5ee5, 0x4f6c, 0x7df7, 0x6c7e,
103   /* a0 */ 0xa50a, 0xb483, 0x8618, 0x9791, 0xe32e, 0xf2a7, 0xc03c, 0xd1b5,
104   /* a8 */ 0x2942, 0x38cb, 0x0a50, 0x1bd9, 0x6f66, 0x7eef, 0x4c74, 0x5dfd,
105   /* b0 */ 0xb58b, 0xa402, 0x9699, 0x8710, 0xf3af, 0xe226, 0xd0bd, 0xc134,
106   /* b8 */ 0x39c3, 0x284a, 0x1ad1, 0x0b58, 0x7fe7, 0x6e6e, 0x5cf5, 0x4d7c,
107   /* c0 */ 0xc60c, 0xd785, 0xe51e, 0xf497, 0x8028, 0x91a1, 0xa33a, 0xb2b3,
108   /* c8 */ 0x4a44, 0x5bcd, 0x6956, 0x78df, 0x0c60, 0x1de9, 0x2f72, 0x3efb,
109   /* d0 */ 0xd68d, 0xc704, 0xf59f, 0xe416, 0x90a9, 0x8120, 0xb3bb, 0xa232,
110   /* d8 */ 0x5ac5, 0x4b4c, 0x79d7, 0x685e, 0x1ce1, 0x0d68, 0x3ff3, 0x2e7a,
111   /* e0 */ 0xe70e, 0xf687, 0xc41c, 0xd595, 0xa12a, 0xb0a3, 0x8238, 0x93b1,
112   /* e8 */ 0x6b46, 0x7acf, 0x4854, 0x59dd, 0x2d62, 0x3ceb, 0x0e70, 0x1ff9,
113   /* f0 */ 0xf78f, 0xe606, 0xd49d, 0xc514, 0xb1ab, 0xa022, 0x92b9, 0x8330,
114   /* f8 */ 0x7bc7, 0x6a4e, 0x58d5, 0x495c, 0x3de3, 0x2c6a, 0x1ef1, 0x0f78
115};
116
117u_char EscMap[33];
118
119void
120HdlcInit()
121{
122  ifOutOctets = 0;
123  ifOutPackets = 0;
124  ifOutLQRs = 0;
125}
126
127/*
128 *  HDLC FCS computation. Read RFC 1171 Appendix B and CCITT X.25 section
129 *  2.27 for further details.
130 */
131inline u_short
132HdlcFcs(u_short fcs, u_char * cp, int len)
133{
134  while (len--)
135    fcs = (fcs >> 8) ^ fcstab[(fcs ^ *cp++) & 0xff];
136  return (fcs);
137}
138
139static inline u_short
140HdlcFcsBuf(u_short fcs, struct mbuf *m)
141{
142  int len;
143  u_char *pos, *end;
144
145  len = plength(m);
146  pos = MBUF_CTOP(m);
147  end = pos + m->cnt;
148  while (len--) {
149    fcs = (fcs >> 8) ^ fcstab[(fcs ^ *pos++) & 0xff];
150    if (pos == end && len) {
151      m = m->next;
152      pos = MBUF_CTOP(m);
153      end = pos + m->cnt;
154    }
155  }
156  return (fcs);
157}
158
159void
160HdlcOutput(int pri, u_short proto, struct mbuf * bp)
161{
162  struct mbuf *mhp, *mfcs;
163  struct protostat *statp;
164  struct lqrdata *lqr;
165  u_char *cp;
166  u_short fcs;
167
168  if ((proto & 0xfff1) == 0x21)		/* Network Layer protocol */
169    if (CcpFsm.state == ST_OPENED)
170      if (CcpOutput(pri, proto, bp))
171        return;
172
173  if (DEV_IS_SYNC)
174    mfcs = NULL;
175  else
176    mfcs = mballoc(2, MB_HDLCOUT);
177
178  mhp = mballoc(4, MB_HDLCOUT);
179  mhp->cnt = 0;
180  cp = MBUF_CTOP(mhp);
181  if (proto == PROTO_LCP || LcpInfo.his_acfcomp == 0) {
182    *cp++ = HDLC_ADDR;
183    *cp++ = HDLC_UI;
184    mhp->cnt += 2;
185  }
186
187  /*
188   * If possible, compress protocol field.
189   */
190  if (LcpInfo.his_protocomp && (proto & 0xff00) == 0) {
191    *cp++ = proto;
192    mhp->cnt++;
193  } else {
194    *cp++ = proto >> 8;
195    *cp = proto & 0377;
196    mhp->cnt += 2;
197  }
198  mhp->next = bp;
199  while (bp->next != NULL)
200    bp = bp->next;
201  bp->next = mfcs;
202  bp = mhp->next;
203
204  lqr = &MyLqrData;
205  lqr->PeerOutPackets = ifOutPackets++;
206  ifOutOctets += plength(mhp) + 1;
207  lqr->PeerOutOctets = ifOutOctets;
208
209  if (proto == PROTO_LQR) {
210    lqr->MagicNumber = LcpInfo.want_magic;
211    lqr->LastOutLQRs = HisLqrData.PeerOutLQRs;
212    lqr->LastOutPackets = HisLqrData.PeerOutPackets;
213    lqr->LastOutOctets = HisLqrData.PeerOutOctets;
214    lqr->PeerInLQRs = HisLqrSave.SaveInLQRs;
215    lqr->PeerInPackets = HisLqrSave.SaveInPackets;
216    lqr->PeerInDiscards = HisLqrSave.SaveInDiscards;
217    lqr->PeerInErrors = HisLqrSave.SaveInErrors;
218    lqr->PeerInOctets = HisLqrSave.SaveInOctets;
219    if (HisLqrData.LastOutLQRs == ifOutLQRs) {
220      /*
221       * only increment if it's the first time or we've got a reply
222       * from the last one
223       */
224      lqr->PeerOutLQRs = ++ifOutLQRs;
225      LqrDump("LqrOutput", lqr);
226    } else {
227      lqr->PeerOutLQRs = ifOutLQRs;
228      LqrDump("LqrOutput (again)", lqr);
229    }
230    LqrChangeOrder(lqr, (struct lqrdata *) (MBUF_CTOP(bp)));
231  }
232  if (!DEV_IS_SYNC) {
233    mfcs->cnt = 0;
234    fcs = HdlcFcsBuf(INITFCS, mhp);
235    fcs = ~fcs;
236    cp = MBUF_CTOP(mfcs);
237    *cp++ = fcs & 0377;		/* Low byte first!! */
238    *cp++ = fcs >> 8;
239    mfcs->cnt = 2;
240  }
241  LogDumpBp(LogHDLC, "HdlcOutput", mhp);
242  for (statp = ProtocolStat; statp->number; statp++)
243    if (statp->number == proto)
244      break;
245  statp->out_count++;
246
247  LogPrintf(LogDEBUG, "HdlcOutput: proto = 0x%04x\n", proto);
248
249  if (DEV_IS_SYNC)
250    ModemOutput(pri, mhp);
251  else
252    AsyncOutput(pri, mhp, proto);
253}
254
255/* Check out the latest ``Assigned numbers'' rfc (rfc1700.txt) */
256static struct {
257  u_short from;
258  u_short to;
259  const char *name;
260} protocols[] = {
261  { 0x0001, 0x0001, "Padding Protocol" },
262  { 0x0003, 0x001f, "reserved (transparency inefficient)" },
263  { 0x0021, 0x0021, "Internet Protocol" },
264  { 0x0023, 0x0023, "OSI Network Layer" },
265  { 0x0025, 0x0025, "Xerox NS IDP" },
266  { 0x0027, 0x0027, "DECnet Phase IV" },
267  { 0x0029, 0x0029, "Appletalk" },
268  { 0x002b, 0x002b, "Novell IPX" },
269  { 0x002d, 0x002d, "Van Jacobson Compressed TCP/IP" },
270  { 0x002f, 0x002f, "Van Jacobson Uncompressed TCP/IP" },
271  { 0x0031, 0x0031, "Bridging PDU" },
272  { 0x0033, 0x0033, "Stream Protocol (ST-II)" },
273  { 0x0035, 0x0035, "Banyan Vines" },
274  { 0x0037, 0x0037, "reserved (until 1993)" },
275  { 0x0039, 0x0039, "AppleTalk EDDP" },
276  { 0x003b, 0x003b, "AppleTalk SmartBuffered" },
277  { 0x003d, 0x003d, "Multi-Link" },
278  { 0x003f, 0x003f, "NETBIOS Framing" },
279  { 0x0041, 0x0041, "Cisco Systems" },
280  { 0x0043, 0x0043, "Ascom Timeplex" },
281  { 0x0045, 0x0045, "Fujitsu Link Backup and Load Balancing (LBLB)" },
282  { 0x0047, 0x0047, "DCA Remote Lan" },
283  { 0x0049, 0x0049, "Serial Data Transport Protocol (PPP-SDTP)" },
284  { 0x004b, 0x004b, "SNA over 802.2" },
285  { 0x004d, 0x004d, "SNA" },
286  { 0x004f, 0x004f, "IP6 Header Compression" },
287  { 0x0051, 0x0051, "KNX Bridging Data" },
288  { 0x0053, 0x0053, "Encryption" },
289  { 0x0055, 0x0055, "Individual Link Encryption" },
290  { 0x006f, 0x006f, "Stampede Bridging" },
291  { 0x0071, 0x0071, "BAP Bandwidth Allocation Protocol" },
292  { 0x0073, 0x0073, "MP+ Protocol" },
293  { 0x007d, 0x007d, "reserved (Control Escape)" },
294  { 0x007f, 0x007f, "reserved (compression inefficient)" },
295  { 0x00cf, 0x00cf, "reserved (PPP NLPID)" },
296  { 0x00fb, 0x00fb, "compression on single link in multilink group" },
297  { 0x00fd, 0x00fd, "1st choice compression" },
298  { 0x00ff, 0x00ff, "reserved (compression inefficient)" },
299  { 0x0200, 0x02ff, "(compression inefficient)" },
300  { 0x0201, 0x0201, "802.1d Hello Packets" },
301  { 0x0203, 0x0203, "IBM Source Routing BPDU" },
302  { 0x0205, 0x0205, "DEC LANBridge100 Spanning Tree" },
303  { 0x0207, 0x0207, "Cisco Discovery Protocol" },
304  { 0x0209, 0x0209, "Netcs Twin Routing" },
305  { 0x0231, 0x0231, "Luxcom" },
306  { 0x0233, 0x0233, "Sigma Network Systems" },
307  { 0x0235, 0x0235, "Apple Client Server Protocol" },
308  { 0x1e00, 0x1eff, "(compression inefficient)" },
309  { 0x4001, 0x4001, "Cray Communications Control Protocol" },
310  { 0x4003, 0x4003, "CDPD Mobile Network Registration Protocol" },
311  { 0x4021, 0x4021, "Stacker LZS" },
312  { 0x8001, 0x801f, "Not Used - reserved" },
313  { 0x8021, 0x8021, "Internet Protocol Control Protocol" },
314  { 0x8023, 0x8023, "OSI Network Layer Control Protocol" },
315  { 0x8025, 0x8025, "Xerox NS IDP Control Protocol" },
316  { 0x8027, 0x8027, "DECnet Phase IV Control Protocol" },
317  { 0x8029, 0x8029, "Appletalk Control Protocol" },
318  { 0x802b, 0x802b, "Novell IPX Control Protocol" },
319  { 0x802d, 0x802d, "reserved" },
320  { 0x802f, 0x802f, "reserved" },
321  { 0x8031, 0x8031, "Bridging NCP" },
322  { 0x8033, 0x8033, "Stream Protocol Control Protocol" },
323  { 0x8035, 0x8035, "Banyan Vines Control Protocol" },
324  { 0x8037, 0x8037, "reserved till 1993" },
325  { 0x8039, 0x8039, "reserved" },
326  { 0x803b, 0x803b, "reserved" },
327  { 0x803d, 0x803d, "Multi-Link Control Protocol" },
328  { 0x803f, 0x803f, "NETBIOS Framing Control Protocol" },
329  { 0x8041, 0x8041, "Cisco Systems Control Protocol" },
330  { 0x8043, 0x8043, "Ascom Timeplex" },
331  { 0x8045, 0x8045, "Fujitsu LBLB Control Protocol" },
332  { 0x8047, 0x8047, "DCA Remote Lan Network Control Protocol (RLNCP)" },
333  { 0x8049, 0x8049, "Serial Data Control Protocol (PPP-SDCP)" },
334  { 0x804b, 0x804b, "SNA over 802.2 Control Protocol" },
335  { 0x804d, 0x804d, "SNA Control Protocol" },
336  { 0x804f, 0x804f, "IP6 Header Compression Control Protocol" },
337  { 0x8051, 0x8051, "KNX Bridging Control Protocol" },
338  { 0x8053, 0x8053, "Encryption Control Protocol" },
339  { 0x8055, 0x8055, "Individual Link Encryption Control Protocol" },
340  { 0x806f, 0x806f, "Stampede Bridging Control Protocol" },
341  { 0x8073, 0x8073, "MP+ Control Protocol" },
342  { 0x8071, 0x8071, "BACP Bandwidth Allocation Control Protocol" },
343  { 0x807d, 0x807d, "Not Used - reserved" },
344  { 0x80cf, 0x80cf, "Not Used - reserved" },
345  { 0x80fb, 0x80fb, "compression on single link in multilink group control" },
346  { 0x80fd, 0x80fd, "Compression Control Protocol" },
347  { 0x80ff, 0x80ff, "Not Used - reserved" },
348  { 0x8207, 0x8207, "Cisco Discovery Protocol Control" },
349  { 0x8209, 0x8209, "Netcs Twin Routing" },
350  { 0x8235, 0x8235, "Apple Client Server Protocol Control" },
351  { 0xc021, 0xc021, "Link Control Protocol" },
352  { 0xc023, 0xc023, "Password Authentication Protocol" },
353  { 0xc025, 0xc025, "Link Quality Report" },
354  { 0xc027, 0xc027, "Shiva Password Authentication Protocol" },
355  { 0xc029, 0xc029, "CallBack Control Protocol (CBCP)" },
356  { 0xc081, 0xc081, "Container Control Protocol" },
357  { 0xc223, 0xc223, "Challenge Handshake Authentication Protocol" },
358  { 0xc225, 0xc225, "RSA Authentication Protocol" },
359  { 0xc227, 0xc227, "Extensible Authentication Protocol" },
360  { 0xc26f, 0xc26f, "Stampede Bridging Authorization Protocol" },
361  { 0xc281, 0xc281, "Proprietary Authentication Protocol" },
362  { 0xc283, 0xc283, "Proprietary Authentication Protocol" },
363  { 0xc481, 0xc481, "Proprietary Node ID Authentication Protocol" }
364};
365
366#define NPROTOCOLS (sizeof protocols/sizeof protocols[0])
367
368static const char *
369Protocol2Nam(u_short proto)
370{
371  int f;
372
373  for (f = 0; f < NPROTOCOLS; f++)
374    if (proto >= protocols[f].from && proto <= protocols[f].to)
375      return protocols[f].name;
376    else if (proto < protocols[f].from)
377      break;
378  return "unrecognised protocol";
379}
380
381static void
382DecodePacket(u_short proto, struct mbuf * bp)
383{
384  u_char *cp;
385
386  LogPrintf(LogDEBUG, "DecodePacket: proto = 0x%04x\n", proto);
387
388  /*
389   * If proto isn't PROTO_COMPD, we still want to pass it to the
390   * decompression routines so that the dictionary's updated
391   */
392  if (CcpFsm.state == ST_OPENED)
393    if (proto == PROTO_COMPD) {
394      if ((bp = CompdInput(&proto, bp)) == NULL)
395        return;
396    } else if ((proto & 0xfff1) == 0x21)	/* Network Layer protocol */
397      CcpDictSetup(proto, bp);
398
399  switch (proto) {
400  case PROTO_LCP:
401    LcpInput(bp);
402    break;
403  case PROTO_PAP:
404    PapInput(bp);
405    break;
406  case PROTO_LQR:
407    HisLqrSave.SaveInLQRs++;
408    LqrInput(bp);
409    break;
410  case PROTO_CHAP:
411    ChapInput(bp);
412    break;
413  case PROTO_VJUNCOMP:
414  case PROTO_VJCOMP:
415    bp = VjCompInput(bp, proto);
416    if (bp == NULL) {
417      break;
418    }
419    /* fall down */
420  case PROTO_IP:
421    IpInput(bp);
422    break;
423  case PROTO_IPCP:
424    IpcpInput(bp);
425    break;
426  case PROTO_CCP:
427    CcpInput(bp);
428    break;
429  default:
430    LogPrintf(LogPHASE, "Unknown protocol 0x%04x (%s)\n",
431              proto, Protocol2Nam(proto));
432    bp->offset -= 2;
433    bp->cnt += 2;
434    cp = MBUF_CTOP(bp);
435    LcpSendProtoRej(cp, bp->cnt);
436    HisLqrSave.SaveInDiscards++;
437    HdlcStat.unknownproto++;
438    pfree(bp);
439    break;
440  }
441}
442
443int
444ReportProtStatus(struct cmdargs const *arg)
445{
446  struct protostat *statp;
447  int cnt;
448
449  statp = ProtocolStat;
450  statp--;
451  cnt = 0;
452  fprintf(VarTerm, "    Protocol     in        out      Protocol      in       out\n");
453  do {
454    statp++;
455    fprintf(VarTerm, "   %-9s: %8lu, %8lu",
456	    statp->name, statp->in_count, statp->out_count);
457    if (++cnt == 2) {
458      fprintf(VarTerm, "\n");
459      cnt = 0;
460    }
461  } while (statp->number);
462  if (cnt)
463    fprintf(VarTerm, "\n");
464  return (0);
465}
466
467int
468ReportHdlcStatus(struct cmdargs const *arg)
469{
470  struct hdlcstat *hp = &HdlcStat;
471
472  if (VarTerm) {
473    fprintf(VarTerm, "HDLC level errors\n\n");
474    fprintf(VarTerm, "FCS: %u  ADDR: %u  COMMAND: %u  PROTO: %u\n",
475	    hp->badfcs, hp->badaddr, hp->badcommand, hp->unknownproto);
476  }
477  return 0;
478}
479
480static struct hdlcstat laststat;
481
482void
483HdlcErrorCheck()
484{
485  struct hdlcstat *hp = &HdlcStat;
486  struct hdlcstat *op = &laststat;
487
488  if (memcmp(hp, op, sizeof laststat)) {
489    LogPrintf(LogPHASE, "HDLC errors -> FCS: %u ADDR: %u COMD: %u PROTO: %u\n",
490	      hp->badfcs - op->badfcs, hp->badaddr - op->badaddr,
491      hp->badcommand - op->badcommand, hp->unknownproto - op->unknownproto);
492  }
493  laststat = HdlcStat;
494}
495
496void
497HdlcInput(struct mbuf * bp)
498{
499  u_short fcs, proto;
500  u_char *cp, addr, ctrl;
501  struct protostat *statp;
502
503  LogDumpBp(LogHDLC, "HdlcInput:", bp);
504  if (DEV_IS_SYNC)
505    fcs = GOODFCS;
506  else
507    fcs = HdlcFcs(INITFCS, MBUF_CTOP(bp), bp->cnt);
508  HisLqrSave.SaveInOctets += bp->cnt + 1;
509
510  LogPrintf(LogDEBUG, "HdlcInput: fcs = %04x (%s)\n",
511	    fcs, (fcs == GOODFCS) ? "good" : "bad");
512  if (fcs != GOODFCS) {
513    HisLqrSave.SaveInErrors++;
514    LogPrintf(LogDEBUG, "HdlcInput: Bad FCS\n");
515    HdlcStat.badfcs++;
516    pfree(bp);
517    return;
518  }
519  if (!DEV_IS_SYNC)
520    bp->cnt -= 2;		/* discard FCS part */
521
522  if (bp->cnt < 2) {		/* XXX: raise this bar ? */
523    pfree(bp);
524    return;
525  }
526  cp = MBUF_CTOP(bp);
527
528  if (!LcpInfo.want_acfcomp) {
529
530    /*
531     * We expect that packet is not compressed.
532     */
533    addr = *cp++;
534    if (addr != HDLC_ADDR) {
535      HisLqrSave.SaveInErrors++;
536      HdlcStat.badaddr++;
537      LogPrintf(LogDEBUG, "HdlcInput: addr %02x\n", *cp);
538      pfree(bp);
539      return;
540    }
541    ctrl = *cp++;
542    if (ctrl != HDLC_UI) {
543      HisLqrSave.SaveInErrors++;
544      HdlcStat.badcommand++;
545      LogPrintf(LogDEBUG, "HdlcInput: %02x\n", *cp);
546      pfree(bp);
547      return;
548    }
549    bp->offset += 2;
550    bp->cnt -= 2;
551  } else if (cp[0] == HDLC_ADDR && cp[1] == HDLC_UI) {
552
553    /*
554     * We can receive compressed packet, but peer still send uncompressed
555     * packet to me.
556     */
557    cp += 2;
558    bp->offset += 2;
559    bp->cnt -= 2;
560  }
561  if (LcpInfo.want_protocomp) {
562    proto = 0;
563    cp--;
564    do {
565      cp++;
566      bp->offset++;
567      bp->cnt--;
568      proto = proto << 8;
569      proto += *cp;
570    } while (!(proto & 1));
571  } else {
572    proto = *cp++ << 8;
573    proto |= *cp++;
574    bp->offset += 2;
575    bp->cnt -= 2;
576  }
577
578  for (statp = ProtocolStat; statp->number; statp++)
579    if (statp->number == proto)
580      break;
581  statp->in_count++;
582  HisLqrSave.SaveInPackets++;
583
584  DecodePacket(proto, bp);
585}
586