The Tcpdump Group git mirrors - tcpdump/blob - print-gre.c

   1 /*      $OpenBSD: print-gre.c,v 1.6 2002/10/30 03:04:04 fgsch Exp $     */
   2
   3 /*
   4  * Copyright (c) 2002 Jason L. Wright (jason@thought.net)
   5  * All rights reserved.
   6  *
   7  * Redistribution and use in source and binary forms, with or without
   8  * modification, are permitted provided that the following conditions
   9  * are met:
  10  * 1. Redistributions of source code must retain the above copyright
  11  *    notice, this list of conditions and the following disclaimer.
  12  * 2. Redistributions in binary form must reproduce the above copyright
  13  *    notice, this list of conditions and the following disclaimer in the
  14  *    documentation and/or other materials provided with the distribution.
  15  * 3. All advertising materials mentioning features or use of this software
  16  *    must display the following acknowledgement:
  17  *      This product includes software developed by Jason L. Wright
  18  * 4. The name of the author may not be used to endorse or promote products
  19  *    derived from this software without specific prior written permission.
  20  *
  21  * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
  22  * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
  23  * WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
  24  * DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT,
  25  * INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
  26  * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
  27  * SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
  28  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
  29  * STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
  30  * ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
  31  * POSSIBILITY OF SUCH DAMAGE.
  32  */
  33
  34 /*
  35  * tcpdump filter for GRE - Generic Routing Encapsulation
  36  * RFC1701 (GRE), RFC1702 (GRE IPv4), and RFC2637 (Enhanced GRE)
  37  */
  38
  39 #define NETDISSECT_REWORKED
  40 #ifdef HAVE_CONFIG_H
  41 #include "config.h"
  42 #endif
  43
  44 #include <tcpdump-stdinc.h>
  45
  46 #include <string.h>
  47
  48 #include "interface.h"
  49 #include "extract.h"
  50 #include "ethertype.h"
  51
  52 static const char tstr[] = "[|gre]";
  53
  54 #define GRE_CP          0x8000          /* checksum present */
  55 #define GRE_RP          0x4000          /* routing present */
  56 #define GRE_KP          0x2000          /* key present */
  57 #define GRE_SP          0x1000          /* sequence# present */
  58 #define GRE_sP          0x0800          /* source routing */
  59 #define GRE_RECRS       0x0700          /* recursion count */
  60 #define GRE_AP          0x0080          /* acknowledgment# present */
  61
  62 static const struct tok gre_flag_values[] = {
  63     { GRE_CP, "checksum present"},
  64     { GRE_RP, "routing present"},
  65     { GRE_KP, "key present"},
  66     { GRE_SP, "sequence# present"},
  67     { GRE_sP, "source routing present"},
  68     { GRE_RECRS, "recursion count"},
  69     { GRE_AP, "ack present"},
  70     { 0, NULL }
  71 };
  72
  73 #define GRE_VERS_MASK   0x0007          /* protocol version */
  74
  75 /* source route entry types */
  76 #define GRESRE_IP       0x0800          /* IP */
  77 #define GRESRE_ASN      0xfffe          /* ASN */
  78
  79 static void gre_print_0(netdissect_options *, const u_char *, u_int);
  80 static void gre_print_1(netdissect_options *, const u_char *, u_int);
  81 static void gre_sre_print(netdissect_options *, uint16_t, uint8_t, uint8_t, const u_char *, u_int);
  82 static void gre_sre_ip_print(netdissect_options *, uint8_t, uint8_t, const u_char *, u_int);
  83 static void gre_sre_asn_print(netdissect_options *, uint8_t, uint8_t, const u_char *, u_int);
  84
  85 void
  86 gre_print(netdissect_options *ndo, const u_char *bp, u_int length)
  87 {
  88         u_int len = length, vers;
  89
  90         if (len < 2) {
  91                 ND_PRINT((ndo, "%s", tstr));
  92                 return;
  93         }
  94         vers = EXTRACT_16BITS(bp) & GRE_VERS_MASK;
  95         ND_PRINT((ndo, "GREv%u",vers));
  96
  97         switch(vers) {
  98         case 0:
  99             gre_print_0(ndo, bp, len);
 100             break;
 101         case 1:
 102             gre_print_1(ndo, bp, len);
 103             break;
 104         default:
 105             ND_PRINT((ndo, " ERROR: unknown-version"));
 106             break;
 107         }
 108 }
 109
 110 static void
 111 gre_print_0(netdissect_options *ndo, const u_char *bp, u_int length)
 112 {
 113         u_int len = length;
 114         uint16_t flags, prot;
 115
 116         flags = EXTRACT_16BITS(bp);
 117         if (ndo->ndo_vflag)
 118             ND_PRINT((ndo, ", Flags [%s]",
 119                    bittok2str(gre_flag_values,"none",flags)));
 120
 121         len -= 2;
 122         bp += 2;
 123
 124         if (len < 2)
 125                 goto trunc;
 126         prot = EXTRACT_16BITS(bp);
 127         len -= 2;
 128         bp += 2;
 129
 130         if ((flags & GRE_CP) | (flags & GRE_RP)) {
 131                 if (len < 2)
 132                         goto trunc;
 133                 if (ndo->ndo_vflag)
 134                         ND_PRINT((ndo, ", sum 0x%x", EXTRACT_16BITS(bp)));
 135                 bp += 2;
 136                 len -= 2;
 137
 138                 if (len < 2)
 139                         goto trunc;
 140                 ND_PRINT((ndo, ", off 0x%x", EXTRACT_16BITS(bp)));
 141                 bp += 2;
 142                 len -= 2;
 143         }
 144
 145         if (flags & GRE_KP) {
 146                 if (len < 4)
 147                         goto trunc;
 148                 ND_PRINT((ndo, ", key=0x%x", EXTRACT_32BITS(bp)));
 149                 bp += 4;
 150                 len -= 4;
 151         }
 152
 153         if (flags & GRE_SP) {
 154                 if (len < 4)
 155                         goto trunc;
 156                 ND_PRINT((ndo, ", seq %u", EXTRACT_32BITS(bp)));
 157                 bp += 4;
 158                 len -= 4;
 159         }
 160
 161         if (flags & GRE_RP) {
 162                 for (;;) {
 163                         uint16_t af;
 164                         uint8_t sreoff;
 165                         uint8_t srelen;
 166
 167                         if (len < 4)
 168                                 goto trunc;
 169                         af = EXTRACT_16BITS(bp);
 170                         sreoff = *(bp + 2);
 171                         srelen = *(bp + 3);
 172                         bp += 4;
 173                         len -= 4;
 174
 175                         if (af == 0 && srelen == 0)
 176                                 break;
 177
 178                         gre_sre_print(ndo, af, sreoff, srelen, bp, len);
 179
 180                         if (len < srelen)
 181                                 goto trunc;
 182                         bp += srelen;
 183                         len -= srelen;
 184                 }
 185         }
 186
 187         if (ndo->ndo_eflag)
 188             ND_PRINT((ndo, ", proto %s (0x%04x)",
 189                    tok2str(ethertype_values,"unknown",prot),
 190                    prot));
 191
 192         ND_PRINT((ndo, ", length %u",length));
 193
 194         if (ndo->ndo_vflag < 1)
 195             ND_PRINT((ndo, ": ")); /* put in a colon as protocol demarc */
 196         else
 197             ND_PRINT((ndo, "\n\t")); /* if verbose go multiline */
 198
 199         switch (prot) {
 200         case ETHERTYPE_IP:
 201                 ip_print(ndo, bp, len);
 202                 break;
 203 #ifdef INET6
 204         case ETHERTYPE_IPV6:
 205                 ip6_print(ndo, bp, len);
 206                 break;
 207 #endif
 208         case ETHERTYPE_MPLS:
 209                 mpls_print(ndo, bp, len);
 210                 break;
 211         case ETHERTYPE_IPX:
 212                 ipx_print(ndo, bp, len);
 213                 break;
 214         case ETHERTYPE_ATALK:
 215                 atalk_print(ndo, bp, len);
 216                 break;
 217         case ETHERTYPE_GRE_ISO:
 218                 isoclns_print(ndo, bp, len, len);
 219                 break;
 220         case ETHERTYPE_TEB:
 221                 ether_print(ndo, bp, len, len, NULL, NULL);
 222                 break;
 223         default:
 224                 ND_PRINT((ndo, "gre-proto-0x%x", prot));
 225         }
 226         return;
 227
 228 trunc:
 229         ND_PRINT((ndo, "%s", tstr));
 230 }
 231
 232 static void
 233 gre_print_1(netdissect_options *ndo, const u_char *bp, u_int length)
 234 {
 235         u_int len = length;
 236         uint16_t flags, prot;
 237
 238         flags = EXTRACT_16BITS(bp);
 239         len -= 2;
 240         bp += 2;
 241
 242         if (ndo->ndo_vflag)
 243             ND_PRINT((ndo, ", Flags [%s]",
 244                    bittok2str(gre_flag_values,"none",flags)));
 245
 246         if (len < 2)
 247                 goto trunc;
 248         prot = EXTRACT_16BITS(bp);
 249         len -= 2;
 250         bp += 2;
 251
 252
 253         if (flags & GRE_KP) {
 254                 uint32_t k;
 255
 256                 if (len < 4)
 257                         goto trunc;
 258                 k = EXTRACT_32BITS(bp);
 259                 ND_PRINT((ndo, ", call %d", k & 0xffff));
 260                 len -= 4;
 261                 bp += 4;
 262         }
 263
 264         if (flags & GRE_SP) {
 265                 if (len < 4)
 266                         goto trunc;
 267                 ND_PRINT((ndo, ", seq %u", EXTRACT_32BITS(bp)));
 268                 bp += 4;
 269                 len -= 4;
 270         }
 271
 272         if (flags & GRE_AP) {
 273                 if (len < 4)
 274                         goto trunc;
 275                 ND_PRINT((ndo, ", ack %u", EXTRACT_32BITS(bp)));
 276                 bp += 4;
 277                 len -= 4;
 278         }
 279
 280         if ((flags & GRE_SP) == 0)
 281                 ND_PRINT((ndo, ", no-payload"));
 282
 283         if (ndo->ndo_eflag)
 284             ND_PRINT((ndo, ", proto %s (0x%04x)",
 285                    tok2str(ethertype_values,"unknown",prot),
 286                    prot));
 287
 288         ND_PRINT((ndo, ", length %u",length));
 289
 290         if ((flags & GRE_SP) == 0)
 291             return;
 292
 293         if (ndo->ndo_vflag < 1)
 294             ND_PRINT((ndo, ": ")); /* put in a colon as protocol demarc */
 295         else
 296             ND_PRINT((ndo, "\n\t")); /* if verbose go multiline */
 297
 298         switch (prot) {
 299         case ETHERTYPE_PPP:
 300                 ppp_print(ndo, bp, len);
 301                 break;
 302         default:
 303                 ND_PRINT((ndo, "gre-proto-0x%x", prot));
 304                 break;
 305         }
 306         return;
 307
 308 trunc:
 309         ND_PRINT((ndo, "%s", tstr));
 310 }
 311
 312 static void
 313 gre_sre_print(netdissect_options *ndo, uint16_t af, uint8_t sreoff,
 314     uint8_t srelen, const u_char *bp, u_int len)
 315 {
 316         switch (af) {
 317         case GRESRE_IP:
 318                 ND_PRINT((ndo, ", (rtaf=ip"));
 319                 gre_sre_ip_print(ndo, sreoff, srelen, bp, len);
 320                 ND_PRINT((ndo, ") "));
 321                 break;
 322         case GRESRE_ASN:
 323                 ND_PRINT((ndo, ", (rtaf=asn"));
 324                 gre_sre_asn_print(ndo, sreoff, srelen, bp, len);
 325                 ND_PRINT((ndo, ") "));
 326                 break;
 327         default:
 328                 ND_PRINT((ndo, ", (rtaf=0x%x) ", af));
 329         }
 330 }
 331
 332 static void
 333 gre_sre_ip_print(netdissect_options *ndo, uint8_t sreoff, uint8_t srelen,
 334                  const u_char *bp, u_int len)
 335 {
 336         struct in_addr a;
 337         const u_char *up = bp;
 338
 339         if (sreoff & 3) {
 340                 ND_PRINT((ndo, ", badoffset=%u", sreoff));
 341                 return;
 342         }
 343         if (srelen & 3) {
 344                 ND_PRINT((ndo, ", badlength=%u", srelen));
 345                 return;
 346         }
 347         if (sreoff >= srelen) {
 348                 ND_PRINT((ndo, ", badoff/len=%u/%u", sreoff, srelen));
 349                 return;
 350         }
 351
 352         for (;;) {
 353                 if (len < 4 || srelen == 0)
 354                         return;
 355
 356                 memcpy(&a, bp, sizeof(a));
 357                 ND_PRINT((ndo, " %s%s",
 358                     ((bp - up) == sreoff) ? "*" : "",
 359                     inet_ntoa(a)));
 360
 361                 bp += 4;
 362                 len -= 4;
 363                 srelen -= 4;
 364         }
 365 }
 366
 367 static void
 368 gre_sre_asn_print(netdissect_options *ndo, uint8_t sreoff, uint8_t srelen,
 369                   const u_char *bp, u_int len)
 370 {
 371         const u_char *up = bp;
 372
 373         if (sreoff & 1) {
 374                 ND_PRINT((ndo, ", badoffset=%u", sreoff));
 375                 return;
 376         }
 377         if (srelen & 1) {
 378                 ND_PRINT((ndo, ", badlength=%u", srelen));
 379                 return;
 380         }
 381         if (sreoff >= srelen) {
 382                 ND_PRINT((ndo, ", badoff/len=%u/%u", sreoff, srelen));
 383                 return;
 384         }
 385
 386         for (;;) {
 387                 if (len < 2 || srelen == 0)
 388                         return;
 389
 390                 ND_PRINT((ndo, " %s%x",
 391                     ((bp - up) == sreoff) ? "*" : "",
 392                     EXTRACT_16BITS(bp)));
 393
 394                 bp += 2;
 395                 len -= 2;
 396                 srelen -= 2;
 397         }
 398 }