1 /* 2 * Copyright (c) 1988-1997 3 * The Regents of the University of California. All rights reserved. 4 * 5 * Copyright (c) 1998-2012 Michael Richardson <mcr@tcpdump.org> 6 * The TCPDUMP project 7 * 8 * Redistribution and use in source and binary forms, with or without 9 * modification, are permitted provided that: (1) source code distributions 10 * retain the above copyright notice and this paragraph in its entirety, (2) 11 * distributions including binary code include the above copyright notice and 12 * this paragraph in its entirety in the documentation or other materials 13 * provided with the distribution, and (3) all advertising materials mentioning 14 * features or use of this software display the following acknowledgement: 15 * ``This product includes software developed by the University of California, 16 * Lawrence Berkeley Laboratory and its contributors.'' Neither the name of 17 * the University nor the names of its contributors may be used to endorse 18 * or promote products derived from this software without specific prior 19 * written permission. 20 * THIS SOFTWARE IS PROVIDED ``AS IS'' AND WITHOUT ANY EXPRESS OR IMPLIED 21 * WARRANTIES, INCLUDING, WITHOUT LIMITATION, THE IMPLIED WARRANTIES OF 22 * MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE. 23 */ 24 25 #include <sys/cdefs.h> 26 #ifndef lint 27 __RCSID("$NetBSD: netdissect.c,v 1.3 2023/08/17 20:19:40 christos Exp $"); 28 #endif 29 30 #ifdef HAVE_CONFIG_H 31 #include <config.h> 32 #endif 33 34 #include "netdissect-stdinc.h" 35 #include "netdissect.h" 36 #include <string.h> 37 #include <stdio.h> 38 #include <stdlib.h> 39 40 #ifdef USE_LIBSMI 41 #include <smi.h> 42 #endif 43 44 /* 45 * Initialize anything that must be initialized before dissecting 46 * packets. 47 * 48 * This should be called at the beginning of the program; it does 49 * not need to be called, and should not be called, for every 50 * netdissect_options structure. 51 */ 52 int 53 nd_init(char *errbuf, size_t errbuf_size) 54 { 55 #ifdef _WIN32 56 WORD wVersionRequested; 57 WSADATA wsaData; 58 int err; 59 60 /* 61 * Request Winsock 2.2; we expect Winsock 2. 62 */ 63 wVersionRequested = MAKEWORD(2, 2); 64 err = WSAStartup(wVersionRequested, &wsaData); 65 if (err != 0) { 66 strlcpy(errbuf, "Attempting to initialize Winsock failed", 67 errbuf_size); 68 return (-1); 69 } 70 #endif /* _WIN32 */ 71 72 #ifdef USE_LIBSMI 73 /* 74 * XXX - should we just fail if this fails? Some of the 75 * libsmi calls may fail. 76 */ 77 smiInit("tcpdump"); 78 #endif 79 80 /* 81 * Clears the error buffer, and uses it so we don't get 82 * "unused argument" warnings at compile time. 83 */ 84 strlcpy(errbuf, "", errbuf_size); 85 return (0); 86 } 87 88 /* 89 * Clean up anything that ndo_init() did. 90 */ 91 void 92 nd_cleanup(void) 93 { 94 #ifdef USE_LIBSMI 95 /* 96 * This appears, in libsmi 0.4.8, to do nothing if smiInit() 97 * wasn't done or failed, so we call it unconditionally. 98 */ 99 smiExit(); 100 #endif 101 102 #ifdef _WIN32 103 /* 104 * Undo the WSAStartup() call above. 105 */ 106 WSACleanup(); 107 #endif 108 } 109 110 int 111 nd_have_smi_support(void) 112 { 113 #ifdef USE_LIBSMI 114 return (1); 115 #else 116 return (0); 117 #endif 118 } 119 120 /* 121 * Indicates whether an SMI module has been loaded, so that we can use 122 * libsmi to translate OIDs. 123 */ 124 int nd_smi_module_loaded; 125 126 int 127 nd_load_smi_module(const char *module, char *errbuf, size_t errbuf_size) 128 { 129 #ifdef USE_LIBSMI 130 if (smiLoadModule(module) == 0) { 131 snprintf(errbuf, errbuf_size, "could not load MIB module %s", 132 module); 133 return (-1); 134 } 135 nd_smi_module_loaded = 1; 136 return (0); 137 #else 138 snprintf(errbuf, errbuf_size, "MIB module %s not loaded: no libsmi support", 139 module); 140 return (-1); 141 #endif 142 } 143 144 const char * 145 nd_smi_version_string(void) 146 { 147 #ifdef USE_LIBSMI 148 return (smi_version_string); 149 #else 150 return (NULL); 151 #endif 152 } 153 154 155 int 156 nd_push_buffer(netdissect_options *ndo, u_char *new_buffer, 157 const u_char *new_packetp, const u_int newlen) 158 { 159 struct netdissect_saved_packet_info *ndspi; 160 161 ndspi = (struct netdissect_saved_packet_info *)malloc(sizeof(struct netdissect_saved_packet_info)); 162 if (ndspi == NULL) 163 return (0); /* fail */ 164 ndspi->ndspi_buffer = new_buffer; 165 ndspi->ndspi_packetp = ndo->ndo_packetp; 166 ndspi->ndspi_snapend = ndo->ndo_snapend; 167 ndspi->ndspi_prev = ndo->ndo_packet_info_stack; 168 169 ndo->ndo_packetp = new_packetp; 170 ndo->ndo_snapend = new_packetp + newlen; 171 ndo->ndo_packet_info_stack = ndspi; 172 173 return (1); /* success */ 174 } 175 176 177 /* 178 * In a given netdissect_options structure: 179 * 180 * push the current packet information onto the packet information 181 * stack; 182 * 183 * given a pointer into the packet and a length past that point in 184 * the packet, calculate a new snapshot end that's at the lower 185 * of the current snapshot end and that point in the packet; 186 * 187 * set the snapshot end to that new value. 188 */ 189 int 190 nd_push_snaplen(netdissect_options *ndo, const u_char *bp, const u_int newlen) 191 { 192 struct netdissect_saved_packet_info *ndspi; 193 u_int snaplen_remaining; 194 195 ndspi = (struct netdissect_saved_packet_info *)malloc(sizeof(struct netdissect_saved_packet_info)); 196 if (ndspi == NULL) 197 return (0); /* fail */ 198 ndspi->ndspi_buffer = NULL; /* no new buffer */ 199 ndspi->ndspi_packetp = ndo->ndo_packetp; 200 ndspi->ndspi_snapend = ndo->ndo_snapend; 201 ndspi->ndspi_prev = ndo->ndo_packet_info_stack; 202 203 /* 204 * Push the saved previous data onto the stack. 205 */ 206 ndo->ndo_packet_info_stack = ndspi; 207 208 /* 209 * Find out how many bytes remain after the current snapend. 210 * 211 * We're restricted to packets with at most UINT_MAX bytes; 212 * cast the result to u_int, so that we don't get truncation 213 * warnings on LP64 and LLP64 platforms. (ptrdiff_t is 214 * signed and we want an unsigned difference; the pointer 215 * should at most be equal to snapend, and must *never* 216 * be past snapend.) 217 */ 218 snaplen_remaining = (u_int)(ndo->ndo_snapend - bp); 219 220 /* 221 * If the new snapend is smaller than the one calculated 222 * above, set the snapend to that value, otherwise leave 223 * it unchanged. 224 */ 225 if (newlen <= snaplen_remaining) { 226 /* Snapend isn't past the previous snapend */ 227 ndo->ndo_snapend = bp + newlen; 228 } 229 230 return (1); /* success */ 231 } 232 233 /* 234 * In a given netdissect_options structure: 235 * 236 * given a pointer into the packet and a length past that point in 237 * the packet, calculate a new snapshot end that's at the lower 238 * of the previous snapshot end - or, if there is no previous 239 * snapshot end, the current snapshot end - and that point in the 240 * packet; 241 * 242 * set the snapshot end to that new value. 243 * 244 * This is to change the current snapshot end. This may increase the 245 * snapshot end, as it may be used, for example, for a Jumbo Payload 246 * option in IPv6. It must not increase it past the snapshot length 247 * atop which the current one was pushed, however. 248 */ 249 void 250 nd_change_snaplen(netdissect_options *ndo, const u_char *bp, const u_int newlen) 251 { 252 struct netdissect_saved_packet_info *ndspi; 253 const u_char *previous_snapend; 254 u_int snaplen_remaining; 255 256 ndspi = ndo->ndo_packet_info_stack; 257 if (ndspi->ndspi_prev != NULL) 258 previous_snapend = ndspi->ndspi_prev->ndspi_snapend; 259 else 260 previous_snapend = ndo->ndo_snapend; 261 262 /* 263 * Find out how many bytes remain after the previous 264 * snapend - or, if there is no previous snapend, after 265 * the current snapend. 266 * 267 * We're restricted to packets with at most UINT_MAX bytes; 268 * cast the result to u_int, so that we don't get truncation 269 * warnings on LP64 and LLP64 platforms. (ptrdiff_t is 270 * signed and we want an unsigned difference; the pointer 271 * should at most be equal to snapend, and must *never* 272 * be past snapend.) 273 */ 274 snaplen_remaining = (u_int)(previous_snapend - bp); 275 276 /* 277 * If the new snapend is smaller than the one calculated 278 * above, set the snapend to that value, otherwise leave 279 * it unchanged. 280 */ 281 if (newlen <= snaplen_remaining) { 282 /* Snapend isn't past the previous snapend */ 283 ndo->ndo_snapend = bp + newlen; 284 } 285 } 286 287 void 288 nd_pop_packet_info(netdissect_options *ndo) 289 { 290 struct netdissect_saved_packet_info *ndspi; 291 292 ndspi = ndo->ndo_packet_info_stack; 293 ndo->ndo_packetp = ndspi->ndspi_packetp; 294 ndo->ndo_snapend = ndspi->ndspi_snapend; 295 ndo->ndo_packet_info_stack = ndspi->ndspi_prev; 296 297 free(ndspi->ndspi_buffer); 298 free(ndspi); 299 } 300 301 void 302 nd_pop_all_packet_info(netdissect_options *ndo) 303 { 304 while (ndo->ndo_packet_info_stack != NULL) 305 nd_pop_packet_info(ndo); 306 } 307