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      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 #ifndef lint
     27 static const char rcsid[] _U_ =
     28     "@(#) $Header: /tcpdump/master/tcpdump/print-vjc.c,v 1.15 2004-03-25 03:31:17 mcr Exp $ (LBL)";
     29 #endif
     30 
     31 #include <tcpdump-stdinc.h>
     32 
     33 #include <pcap.h>
     34 #include <stdio.h>
     35 
     36 #include "interface.h"
     37 #include "addrtoname.h"
     38 
     39 #include "slcompress.h"
     40 #include "ppp.h"
     41 
     42 /*
     43  * XXX - for BSD/OS PPP, what packets get supplied with a PPP header type
     44  * of PPP_VJC and what packets get supplied with a PPP header type of
     45  * PPP_VJNC?  PPP_VJNC is for "UNCOMPRESSED_TCP" packets, and PPP_VJC
     46  * is for COMPRESSED_TCP packets (PPP_IP is used for TYPE_IP packets).
     47  *
     48  * RFC 1144 implies that, on the wire, the packet type is *not* needed
     49  * for PPP, as different PPP protocol types can be used; it only needs
     50  * to be put on the wire for SLIP.
     51  *
     52  * It also indicates that, for compressed SLIP:
     53  *
     54  *	If the COMPRESSED_TCP bit is set in the first byte, it's
     55  *	a COMPRESSED_TCP packet; that byte is the change byte, and
     56  *	the COMPRESSED_TCP bit, 0x80, isn't used in the change byte.
     57  *
     58  *	If the upper 4 bits of the first byte are 7, it's an
     59  *	UNCOMPRESSED_TCP packet; that byte is the first byte of
     60  *	the UNCOMPRESSED_TCP modified IP header, with a connection
     61  *	number in the protocol field, and with the version field
     62  *	being 7, not 4.
     63  *
     64  *	Otherwise, the packet is an IPv4 packet (where the upper 4 bits
     65  *	of the packet are 4).
     66  *
     67  * So this routine looks as if it's sort-of intended to handle
     68  * compressed SLIP, although it doesn't handle UNCOMPRESSED_TCP
     69  * correctly for that (it doesn't fix the version number and doesn't
     70  * do anything to the protocol field), and doesn't check for COMPRESSED_TCP
     71  * packets correctly for that (you only check the first bit - see
     72  * B.1 in RFC 1144).
     73  *
     74  * But it's called for BSD/OS PPP, not SLIP - perhaps BSD/OS does weird
     75  * things with the headers?
     76  *
     77  * Without a BSD/OS VJC-compressed PPP trace, or knowledge of what the
     78  * BSD/OS VJC code does, we can't say what's the case.
     79  *
     80  * We therefore leave "proto" - which is the PPP protocol type - in place,
     81  * *not* marked as unused, for now, so that GCC warnings about the
     82  * unused argument remind us that we should fix this some day.
     83  */
     84 int
     85 vjc_print(register const char *bp, u_short proto _U_)
     86 {
     87 	int i;
     88 
     89 	switch (bp[0] & 0xf0) {
     90 	case TYPE_IP:
     91 		if (eflag)
     92 			printf("(vjc type=IP) ");
     93 		return PPP_IP;
     94 	case TYPE_UNCOMPRESSED_TCP:
     95 		if (eflag)
     96 			printf("(vjc type=raw TCP) ");
     97 		return PPP_IP;
     98 	case TYPE_COMPRESSED_TCP:
     99 		if (eflag)
    100 			printf("(vjc type=compressed TCP) ");
    101 		for (i = 0; i < 8; i++) {
    102 			if (bp[1] & (0x80 >> i))
    103 				printf("%c", "?CI?SAWU"[i]);
    104 		}
    105 		if (bp[1])
    106 			printf(" ");
    107 		printf("C=0x%02x ", bp[2]);
    108 		printf("sum=0x%04x ", *(u_short *)&bp[3]);
    109 		return -1;
    110 	case TYPE_ERROR:
    111 		if (eflag)
    112 			printf("(vjc type=error) ");
    113 		return -1;
    114 	default:
    115 		if (eflag)
    116 			printf("(vjc type=0x%02x) ", bp[0] & 0xf0);
    117 		return -1;
    118 	}
    119 }
    120