The Tcpdump Group git mirrors - tcpdump/blob - netdissect.c

   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 <config.h>
  26
  27 #include "netdissect-stdinc.h"
  28 #include "netdissect.h"
  29 #include <string.h>
  30 #include <stdio.h>
  31 #include <stdlib.h>
  32
  33 #ifdef USE_LIBSMI
  34 #include <smi.h>
  35 #endif
  36
  37 /*
  38  * Initialize anything that must be initialized before dissecting
  39  * packets.
  40  *
  41  * This should be called at the beginning of the program; it does
  42  * not need to be called, and should not be called, for every
  43  * netdissect_options structure.
  44  */
  45 int
  46 nd_init(char *errbuf, size_t errbuf_size)
  47 {
  48 #ifdef _WIN32
  49         WORD wVersionRequested;
  50         WSADATA wsaData;
  51         int err;
  52
  53         /*
  54          * Request Winsock 2.2; we expect Winsock 2.
  55          */
  56         wVersionRequested = MAKEWORD(2, 2);
  57         err = WSAStartup(wVersionRequested, &wsaData);
  58         if (err != 0) {
  59                 strlcpy(errbuf, "Attempting to initialize Winsock failed",
  60                     errbuf_size);
  61                 return (-1);
  62         }
  63 #endif /* _WIN32 */
  64
  65 #ifdef USE_LIBSMI
  66         /*
  67          * XXX - should we just fail if this fails?  Some of the
  68          * libsmi calls may fail.
  69          */
  70         smiInit("tcpdump");
  71 #endif
  72
  73         /*
  74          * Clears the error buffer, and uses it so we don't get
  75          * "unused argument" warnings at compile time.
  76          */
  77         strlcpy(errbuf, "", errbuf_size);
  78         return (0);
  79 }
  80
  81 /*
  82  * Clean up anything that ndo_init() did.
  83  */
  84 void
  85 nd_cleanup(void)
  86 {
  87 #ifdef USE_LIBSMI
  88         /*
  89          * This appears, in libsmi 0.4.8, to do nothing if smiInit()
  90          * wasn't done or failed, so we call it unconditionally.
  91          */
  92         smiExit();
  93 #endif
  94
  95 #ifdef _WIN32
  96         /*
  97          * Undo the WSAStartup() call above.
  98          */
  99         WSACleanup();
 100 #endif
 101 }
 102
 103 int
 104 nd_have_smi_support(void)
 105 {
 106 #ifdef USE_LIBSMI
 107         return (1);
 108 #else
 109         return (0);
 110 #endif
 111 }
 112
 113 /*
 114  * Indicates whether an SMI module has been loaded, so that we can use
 115  * libsmi to translate OIDs.
 116  */
 117 int nd_smi_module_loaded;
 118
 119 int
 120 nd_load_smi_module(const char *module, char *errbuf, size_t errbuf_size)
 121 {
 122 #ifdef USE_LIBSMI
 123         if (smiLoadModule(module) == 0) {
 124                 snprintf(errbuf, errbuf_size, "could not load MIB module %s",
 125                     module);
 126                 return (-1);
 127         }
 128         nd_smi_module_loaded = 1;
 129         return (0);
 130 #else
 131         snprintf(errbuf, errbuf_size, "MIB module %s not loaded: no libsmi support",
 132             module);
 133         return (-1);
 134 #endif
 135 }
 136
 137 const char *
 138 nd_smi_version_string(void)
 139 {
 140 #ifdef USE_LIBSMI
 141         return (smi_version_string);
 142 #else
 143         return (NULL);
 144 #endif
 145 }
 146
 147
 148 int
 149 nd_push_buffer(netdissect_options *ndo, u_char *new_buffer,
 150                const u_char *new_packetp, const u_int newlen)
 151 {
 152         struct netdissect_saved_packet_info *ndspi;
 153
 154         ndspi = (struct netdissect_saved_packet_info *)malloc(sizeof(struct netdissect_saved_packet_info));
 155         if (ndspi == NULL)
 156                 return (0);     /* fail */
 157         ndspi->ndspi_buffer = new_buffer;
 158         ndspi->ndspi_packetp = ndo->ndo_packetp;
 159         ndspi->ndspi_snapend = ndo->ndo_snapend;
 160         ndspi->ndspi_prev = ndo->ndo_packet_info_stack;
 161
 162         ndo->ndo_packetp = new_packetp;
 163         ndo->ndo_snapend = new_packetp + newlen;
 164         ndo->ndo_packet_info_stack = ndspi;
 165
 166         return (1);     /* success */
 167 }
 168
 169
 170 /*
 171  * In a given netdissect_options structure:
 172  *
 173  *    push the current packet information onto the packet information
 174  *    stack;
 175  *
 176  *    given a pointer into the packet and a length past that point in
 177  *    the packet, calculate a new snapshot end that's at the lower
 178  *    of the current snapshot end and that point in the packet;
 179  *
 180  *    set the snapshot end to that new value.
 181  */
 182 int
 183 nd_push_snaplen(netdissect_options *ndo, const u_char *bp, const u_int newlen)
 184 {
 185         struct netdissect_saved_packet_info *ndspi;
 186         u_int snaplen_remaining;
 187
 188         ndspi = (struct netdissect_saved_packet_info *)malloc(sizeof(struct netdissect_saved_packet_info));
 189         if (ndspi == NULL)
 190                 return (0);     /* fail */
 191         ndspi->ndspi_buffer = NULL;     /* no new buffer */
 192         ndspi->ndspi_packetp = ndo->ndo_packetp;
 193         ndspi->ndspi_snapend = ndo->ndo_snapend;
 194         ndspi->ndspi_prev = ndo->ndo_packet_info_stack;
 195
 196         /*
 197          * Push the saved previous data onto the stack.
 198          */
 199         ndo->ndo_packet_info_stack = ndspi;
 200
 201         /*
 202          * Find out how many bytes remain after the current snapend.
 203          *
 204          * We're restricted to packets with at most UINT_MAX bytes;
 205          * cast the result to u_int, so that we don't get truncation
 206          * warnings on LP64 and LLP64 platforms.  (ptrdiff_t is
 207          * signed and we want an unsigned difference; the pointer
 208          * should at most be equal to snapend, and must *never*
 209          * be past snapend.)
 210          */
 211         snaplen_remaining = (u_int)(ndo->ndo_snapend - bp);
 212
 213         /*
 214          * If the new snapend is smaller than the one calculated
 215          * above, set the snapend to that value, otherwise leave
 216          * it unchanged.
 217          */
 218         if (newlen <= snaplen_remaining) {
 219                 /* Snapend isn't past the previous snapend */
 220                 ndo->ndo_snapend = bp + newlen;
 221         }
 222
 223         return (1);     /* success */
 224 }
 225
 226 /*
 227  * In a given netdissect_options structure:
 228  *
 229  *    given a pointer into the packet and a length past that point in
 230  *    the packet, calculate a new snapshot end that's at the lower
 231  *    of the previous snapshot end - or, if there is no previous
 232  *    snapshot end, the current snapshot end - and that point in the
 233  *    packet;
 234  *
 235  *    set the snapshot end to that new value.
 236  *
 237  * This is to change the current snapshot end.  This may increase the
 238  * snapshot end, as it may be used, for example, for a Jumbo Payload
 239  * option in IPv6.  It must not increase it past the snapshot length
 240  * atop which the current one was pushed, however.
 241  */
 242 void
 243 nd_change_snaplen(netdissect_options *ndo, const u_char *bp, const u_int newlen)
 244 {
 245         struct netdissect_saved_packet_info *ndspi;
 246         const u_char *previous_snapend;
 247         u_int snaplen_remaining;
 248
 249         ndspi = ndo->ndo_packet_info_stack;
 250         if (ndspi->ndspi_prev != NULL)
 251                 previous_snapend = ndspi->ndspi_prev->ndspi_snapend;
 252         else
 253                 previous_snapend = ndo->ndo_snapend;
 254
 255         /*
 256          * Find out how many bytes remain after the previous
 257          * snapend - or, if there is no previous snapend, after
 258          * the current snapend.
 259          *
 260          * We're restricted to packets with at most UINT_MAX bytes;
 261          * cast the result to u_int, so that we don't get truncation
 262          * warnings on LP64 and LLP64 platforms.  (ptrdiff_t is
 263          * signed and we want an unsigned difference; the pointer
 264          * should at most be equal to snapend, and must *never*
 265          * be past snapend.)
 266          */
 267         snaplen_remaining = (u_int)(previous_snapend - bp);
 268
 269         /*
 270          * If the new snapend is smaller than the one calculated
 271          * above, set the snapend to that value, otherwise leave
 272          * it unchanged.
 273          */
 274         if (newlen <= snaplen_remaining) {
 275                 /* Snapend isn't past the previous snapend */
 276                 ndo->ndo_snapend = bp + newlen;
 277         }
 278 }
 279
 280 void
 281 nd_pop_packet_info(netdissect_options *ndo)
 282 {
 283         struct netdissect_saved_packet_info *ndspi;
 284
 285         ndspi = ndo->ndo_packet_info_stack;
 286         ndo->ndo_packetp = ndspi->ndspi_packetp;
 287         ndo->ndo_snapend = ndspi->ndspi_snapend;
 288         ndo->ndo_packet_info_stack = ndspi->ndspi_prev;
 289
 290         free(ndspi->ndspi_buffer);
 291         free(ndspi);
 292 }
 293
 294 void
 295 nd_pop_all_packet_info(netdissect_options *ndo)
 296 {
 297         while (ndo->ndo_packet_info_stack != NULL)
 298                 nd_pop_packet_info(ndo);
 299 }
 300
 301 NORETURN void
 302 nd_trunc_longjmp(netdissect_options *ndo)
 303 {
 304         longjmp(ndo->ndo_early_end, ND_TRUNCATED);
 305 #ifdef _AIX
 306         /*
 307          * In AIX <setjmp.h> decorates longjmp() with "#pragma leaves", which tells
 308          * XL C that the function is noreturn, but GCC remains unaware of that and
 309          * yields a "'noreturn' function does return" warning.
 310          */
 311         ND_UNREACHABLE
 312 #endif /* _AIX */
 313 }