The Tcpdump Group git mirrors - tcpdump/blob - print-vjc.c

   1 /*
   2  * Copyright (c) 1990, 1991, 1993, 1994, 1995, 1996, 1997
   3  *      The Regents of the University of California.  All rights reserved.
   4  *
   5  * Redistribution and use in source and binary forms, with or without
   6  * modification, are permitted provided that: (1) source code distributions
   7  * retain the above copyright notice and this paragraph in its entirety, (2)
   8  * distributions including binary code include the above copyright notice and
   9  * this paragraph in its entirety in the documentation or other materials
  10  * provided with the distribution, and (3) all advertising materials mentioning
  11  * features or use of this software display the following acknowledgement:
  12  * ``This product includes software developed by the University of California,
  13  * Lawrence Berkeley Laboratory and its contributors.'' Neither the name of
  14  * the University nor the names of its contributors may be used to endorse
  15  * or promote products derived from this software without specific prior
  16  * written permission.
  17  * THIS SOFTWARE IS PROVIDED ``AS IS'' AND WITHOUT ANY EXPRESS OR IMPLIED
  18  * WARRANTIES, INCLUDING, WITHOUT LIMITATION, THE IMPLIED WARRANTIES OF
  19  * MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE.
  20  */
  21
  22 #ifdef HAVE_CONFIG_H
  23 #include "config.h"
  24 #endif
  25
  26 #include <tcpdump-stdinc.h>
  27
  28 #include <stdio.h>
  29
  30 #include "interface.h"
  31
  32 #include "slcompress.h"
  33 #include "ppp.h"
  34
  35 /*
  36  * XXX - for BSD/OS PPP, what packets get supplied with a PPP header type
  37  * of PPP_VJC and what packets get supplied with a PPP header type of
  38  * PPP_VJNC?  PPP_VJNC is for "UNCOMPRESSED_TCP" packets, and PPP_VJC
  39  * is for COMPRESSED_TCP packets (PPP_IP is used for TYPE_IP packets).
  40  *
  41  * RFC 1144 implies that, on the wire, the packet type is *not* needed
  42  * for PPP, as different PPP protocol types can be used; it only needs
  43  * to be put on the wire for SLIP.
  44  *
  45  * It also indicates that, for compressed SLIP:
  46  *
  47  *      If the COMPRESSED_TCP bit is set in the first byte, it's
  48  *      a COMPRESSED_TCP packet; that byte is the change byte, and
  49  *      the COMPRESSED_TCP bit, 0x80, isn't used in the change byte.
  50  *
  51  *      If the upper 4 bits of the first byte are 7, it's an
  52  *      UNCOMPRESSED_TCP packet; that byte is the first byte of
  53  *      the UNCOMPRESSED_TCP modified IP header, with a connection
  54  *      number in the protocol field, and with the version field
  55  *      being 7, not 4.
  56  *
  57  *      Otherwise, the packet is an IPv4 packet (where the upper 4 bits
  58  *      of the packet are 4).
  59  *
  60  * So this routine looks as if it's sort-of intended to handle
  61  * compressed SLIP, although it doesn't handle UNCOMPRESSED_TCP
  62  * correctly for that (it doesn't fix the version number and doesn't
  63  * do anything to the protocol field), and doesn't check for COMPRESSED_TCP
  64  * packets correctly for that (you only check the first bit - see
  65  * B.1 in RFC 1144).
  66  *
  67  * But it's called for BSD/OS PPP, not SLIP - perhaps BSD/OS does weird
  68  * things with the headers?
  69  *
  70  * Without a BSD/OS VJC-compressed PPP trace, or knowledge of what the
  71  * BSD/OS VJC code does, we can't say what's the case.
  72  *
  73  * We therefore leave "proto" - which is the PPP protocol type - in place,
  74  * *not* marked as unused, for now, so that GCC warnings about the
  75  * unused argument remind us that we should fix this some day.
  76  */
  77 int
  78 vjc_print(register const char *bp, u_short proto _U_)
  79 {
  80         int i;
  81
  82         switch (bp[0] & 0xf0) {
  83         case TYPE_IP:
  84                 if (eflag)
  85                         printf("(vjc type=IP) ");
  86                 return PPP_IP;
  87         case TYPE_UNCOMPRESSED_TCP:
  88                 if (eflag)
  89                         printf("(vjc type=raw TCP) ");
  90                 return PPP_IP;
  91         case TYPE_COMPRESSED_TCP:
  92                 if (eflag)
  93                         printf("(vjc type=compressed TCP) ");
  94                 for (i = 0; i < 8; i++) {
  95                         if (bp[1] & (0x80 >> i))
  96                                 printf("%c", "?CI?SAWU"[i]);
  97                 }
  98                 if (bp[1])
  99                         printf(" ");
 100                 printf("C=0x%02x ", bp[2]);
 101                 printf("sum=0x%04x ", *(u_short *)&bp[3]);
 102                 return -1;
 103         case TYPE_ERROR:
 104                 if (eflag)
 105                         printf("(vjc type=error) ");
 106                 return -1;
 107         default:
 108                 if (eflag)
 109                         printf("(vjc type=0x%02x) ", bp[0] & 0xf0);
 110                 return -1;
 111         }
 112 }