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1 office 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 #define NETDISSECT_REWORKED
23 #ifdef HAVE_CONFIG_H
24 #include "config.h"
25 #endif
26  
27 #include <tcpdump-stdinc.h>
28  
29 #include "interface.h"
30 #include "slcompress.h"
31 #include "ppp.h"
32  
33 /*
34 * XXX - for BSD/OS PPP, what packets get supplied with a PPP header type
35 * of PPP_VJC and what packets get supplied with a PPP header type of
36 * PPP_VJNC? PPP_VJNC is for "UNCOMPRESSED_TCP" packets, and PPP_VJC
37 * is for COMPRESSED_TCP packets (PPP_IP is used for TYPE_IP packets).
38 *
39 * RFC 1144 implies that, on the wire, the packet type is *not* needed
40 * for PPP, as different PPP protocol types can be used; it only needs
41 * to be put on the wire for SLIP.
42 *
43 * It also indicates that, for compressed SLIP:
44 *
45 * If the COMPRESSED_TCP bit is set in the first byte, it's
46 * a COMPRESSED_TCP packet; that byte is the change byte, and
47 * the COMPRESSED_TCP bit, 0x80, isn't used in the change byte.
48 *
49 * If the upper 4 bits of the first byte are 7, it's an
50 * UNCOMPRESSED_TCP packet; that byte is the first byte of
51 * the UNCOMPRESSED_TCP modified IP header, with a connection
52 * number in the protocol field, and with the version field
53 * being 7, not 4.
54 *
55 * Otherwise, the packet is an IPv4 packet (where the upper 4 bits
56 * of the packet are 4).
57 *
58 * So this routine looks as if it's sort-of intended to handle
59 * compressed SLIP, although it doesn't handle UNCOMPRESSED_TCP
60 * correctly for that (it doesn't fix the version number and doesn't
61 * do anything to the protocol field), and doesn't check for COMPRESSED_TCP
62 * packets correctly for that (you only check the first bit - see
63 * B.1 in RFC 1144).
64 *
65 * But it's called for BSD/OS PPP, not SLIP - perhaps BSD/OS does weird
66 * things with the headers?
67 *
68 * Without a BSD/OS VJC-compressed PPP trace, or knowledge of what the
69 * BSD/OS VJC code does, we can't say what's the case.
70 *
71 * We therefore leave "proto" - which is the PPP protocol type - in place,
72 * *not* marked as unused, for now, so that GCC warnings about the
73 * unused argument remind us that we should fix this some day.
74 */
75 int
76 vjc_print(netdissect_options *ndo, register const char *bp, u_short proto _U_)
77 {
78 int i;
79  
80 switch (bp[0] & 0xf0) {
81 case TYPE_IP:
82 if (ndo->ndo_eflag)
83 ND_PRINT((ndo, "(vjc type=IP) "));
84 return PPP_IP;
85 case TYPE_UNCOMPRESSED_TCP:
86 if (ndo->ndo_eflag)
87 ND_PRINT((ndo, "(vjc type=raw TCP) "));
88 return PPP_IP;
89 case TYPE_COMPRESSED_TCP:
90 if (ndo->ndo_eflag)
91 ND_PRINT((ndo, "(vjc type=compressed TCP) "));
92 for (i = 0; i < 8; i++) {
93 if (bp[1] & (0x80 >> i))
94 ND_PRINT((ndo, "%c", "?CI?SAWU"[i]));
95 }
96 if (bp[1])
97 ND_PRINT((ndo, " "));
98 ND_PRINT((ndo, "C=0x%02x ", bp[2]));
99 ND_PRINT((ndo, "sum=0x%04x ", *(u_short *)&bp[3]));
100 return -1;
101 case TYPE_ERROR:
102 if (ndo->ndo_eflag)
103 ND_PRINT((ndo, "(vjc type=error) "));
104 return -1;
105 default:
106 if (ndo->ndo_eflag)
107 ND_PRINT((ndo, "(vjc type=0x%02x) ", bp[0] & 0xf0));
108 return -1;
109 }
110 }