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 /* \summary: PPP Van Jacobson compression printer */ 23 24 /* specification: RFC 1144 */ 25 26 #ifdef HAVE_CONFIG_H 27 #include "config.h" 28 #endif 29 30 #include <netdissect-stdinc.h> 31 32 #include "netdissect.h" 33 #include "slcompress.h" 34 #include "ppp.h" 35 36 /* 37 * XXX - for BSD/OS PPP, what packets get supplied with a PPP header type 38 * of PPP_VJC and what packets get supplied with a PPP header type of 39 * PPP_VJNC? PPP_VJNC is for "UNCOMPRESSED_TCP" packets, and PPP_VJC 40 * is for COMPRESSED_TCP packets (PPP_IP is used for TYPE_IP packets). 41 * 42 * RFC 1144 implies that, on the wire, the packet type is *not* needed 43 * for PPP, as different PPP protocol types can be used; it only needs 44 * to be put on the wire for SLIP. 45 * 46 * It also indicates that, for compressed SLIP: 47 * 48 * If the COMPRESSED_TCP bit is set in the first byte, it's 49 * a COMPRESSED_TCP packet; that byte is the change byte, and 50 * the COMPRESSED_TCP bit, 0x80, isn't used in the change byte. 51 * 52 * If the upper 4 bits of the first byte are 7, it's an 53 * UNCOMPRESSED_TCP packet; that byte is the first byte of 54 * the UNCOMPRESSED_TCP modified IP header, with a connection 55 * number in the protocol field, and with the version field 56 * being 7, not 4. 57 * 58 * Otherwise, the packet is an IPv4 packet (where the upper 4 bits 59 * of the packet are 4). 60 * 61 * So this routine looks as if it's sort-of intended to handle 62 * compressed SLIP, although it doesn't handle UNCOMPRESSED_TCP 63 * correctly for that (it doesn't fix the version number and doesn't 64 * do anything to the protocol field), and doesn't check for COMPRESSED_TCP 65 * packets correctly for that (you only check the first bit - see 66 * B.1 in RFC 1144). 67 * 68 * But it's called for BSD/OS PPP, not SLIP - perhaps BSD/OS does weird 69 * things with the headers? 70 * 71 * Without a BSD/OS VJC-compressed PPP trace, or knowledge of what the 72 * BSD/OS VJC code does, we can't say what's the case. 73 * 74 * We therefore leave "proto" - which is the PPP protocol type - in place, 75 * *not* marked as unused, for now, so that GCC warnings about the 76 * unused argument remind us that we should fix this some day. 77 * 78 * XXX - also, it fetches the TCP checksum field in COMPRESSED_TCP 79 * packets directly, rather than with EXTRACT_16BITS(); RFC 1144 says 80 * it's "the unmodified TCP checksum", which would imply that it's 81 * big-endian, but perhaps, on the platform where this was developed, 82 * the packets were munged by the networking stack before being handed 83 * to the packet capture mechanism. 84 */ 85 int 86 vjc_print(netdissect_options *ndo, register const char *bp, u_short proto _U_) 87 { 88 int i; 89 90 switch (bp[0] & 0xf0) { 91 case TYPE_IP: 92 if (ndo->ndo_eflag) 93 ND_PRINT((ndo, "(vjc type=IP) ")); 94 return PPP_IP; 95 case TYPE_UNCOMPRESSED_TCP: 96 if (ndo->ndo_eflag) 97 ND_PRINT((ndo, "(vjc type=raw TCP) ")); 98 return PPP_IP; 99 case TYPE_COMPRESSED_TCP: 100 if (ndo->ndo_eflag) 101 ND_PRINT((ndo, "(vjc type=compressed TCP) ")); 102 for (i = 0; i < 8; i++) { 103 if (bp[1] & (0x80 >> i)) 104 ND_PRINT((ndo, "%c", "?CI?SAWU"[i])); 105 } 106 if (bp[1]) 107 ND_PRINT((ndo, " ")); 108 ND_PRINT((ndo, "C=0x%02x ", bp[2])); 109 ND_PRINT((ndo, "sum=0x%04x ", *(const u_short *)&bp[3])); 110 return -1; 111 case TYPE_ERROR: 112 if (ndo->ndo_eflag) 113 ND_PRINT((ndo, "(vjc type=error) ")); 114 return -1; 115 default: 116 if (ndo->ndo_eflag) 117 ND_PRINT((ndo, "(vjc type=0x%02x) ", bp[0] & 0xf0)); 118 return -1; 119 } 120 } 121
