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 #include <sys/cdefs.h> 23 #ifndef lint 24 __RCSID("$NetBSD: print-vjc.c,v 1.6 2017/02/05 04:05:05 spz Exp $"); 25 #endif 26 27 /* \summary: PPP Van Jacobson compression printer */ 28 29 /* specification: RFC 1144 */ 30 31 #ifdef HAVE_CONFIG_H 32 #include "config.h" 33 #endif 34 35 #include <netdissect-stdinc.h> 36 37 #include "netdissect.h" 38 #include "slcompress.h" 39 #include "ppp.h" 40 41 /* 42 * XXX - for BSD/OS PPP, what packets get supplied with a PPP header type 43 * of PPP_VJC and what packets get supplied with a PPP header type of 44 * PPP_VJNC? PPP_VJNC is for "UNCOMPRESSED_TCP" packets, and PPP_VJC 45 * is for COMPRESSED_TCP packets (PPP_IP is used for TYPE_IP packets). 46 * 47 * RFC 1144 implies that, on the wire, the packet type is *not* needed 48 * for PPP, as different PPP protocol types can be used; it only needs 49 * to be put on the wire for SLIP. 50 * 51 * It also indicates that, for compressed SLIP: 52 * 53 * If the COMPRESSED_TCP bit is set in the first byte, it's 54 * a COMPRESSED_TCP packet; that byte is the change byte, and 55 * the COMPRESSED_TCP bit, 0x80, isn't used in the change byte. 56 * 57 * If the upper 4 bits of the first byte are 7, it's an 58 * UNCOMPRESSED_TCP packet; that byte is the first byte of 59 * the UNCOMPRESSED_TCP modified IP header, with a connection 60 * number in the protocol field, and with the version field 61 * being 7, not 4. 62 * 63 * Otherwise, the packet is an IPv4 packet (where the upper 4 bits 64 * of the packet are 4). 65 * 66 * So this routine looks as if it's sort-of intended to handle 67 * compressed SLIP, although it doesn't handle UNCOMPRESSED_TCP 68 * correctly for that (it doesn't fix the version number and doesn't 69 * do anything to the protocol field), and doesn't check for COMPRESSED_TCP 70 * packets correctly for that (you only check the first bit - see 71 * B.1 in RFC 1144). 72 * 73 * But it's called for BSD/OS PPP, not SLIP - perhaps BSD/OS does weird 74 * things with the headers? 75 * 76 * Without a BSD/OS VJC-compressed PPP trace, or knowledge of what the 77 * BSD/OS VJC code does, we can't say what's the case. 78 * 79 * We therefore leave "proto" - which is the PPP protocol type - in place, 80 * *not* marked as unused, for now, so that GCC warnings about the 81 * unused argument remind us that we should fix this some day. 82 * 83 * XXX - also, it fetches the TCP checksum field in COMPRESSED_TCP 84 * packets directly, rather than with EXTRACT_16BITS(); RFC 1144 says 85 * it's "the unmodified TCP checksum", which would imply that it's 86 * big-endian, but perhaps, on the platform where this was developed, 87 * the packets were munged by the networking stack before being handed 88 * to the packet capture mechanism. 89 */ 90 int 91 vjc_print(netdissect_options *ndo, register const char *bp, u_short proto _U_) 92 { 93 int i; 94 95 switch (bp[0] & 0xf0) { 96 case TYPE_IP: 97 if (ndo->ndo_eflag) 98 ND_PRINT((ndo, "(vjc type=IP) ")); 99 return PPP_IP; 100 case TYPE_UNCOMPRESSED_TCP: 101 if (ndo->ndo_eflag) 102 ND_PRINT((ndo, "(vjc type=raw TCP) ")); 103 return PPP_IP; 104 case TYPE_COMPRESSED_TCP: 105 if (ndo->ndo_eflag) 106 ND_PRINT((ndo, "(vjc type=compressed TCP) ")); 107 for (i = 0; i < 8; i++) { 108 if (bp[1] & (0x80 >> i)) 109 ND_PRINT((ndo, "%c", "?CI?SAWU"[i])); 110 } 111 if (bp[1]) 112 ND_PRINT((ndo, " ")); 113 ND_PRINT((ndo, "C=0x%02x ", bp[2])); 114 ND_PRINT((ndo, "sum=0x%04x ", *(const u_short *)&bp[3])); 115 return -1; 116 case TYPE_ERROR: 117 if (ndo->ndo_eflag) 118 ND_PRINT((ndo, "(vjc type=error) ")); 119 return -1; 120 default: 121 if (ndo->ndo_eflag) 122 ND_PRINT((ndo, "(vjc type=0x%02x) ", bp[0] & 0xf0)); 123 return -1; 124 } 125 } 126