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 #ifdef HAVE_CONFIG_H
  40 #include "config.h"
  41 #endif
  42
  43 #include <tcpdump-stdinc.h>
  44
  45 #include <string.h>
  46
  47 #include "interface.h"
  48 #include "extract.h"
  49 #include "ethertype.h"
  50
  51 static const char tstr[] = "[|gre]";
  52
  53 #define GRE_CP          0x8000          /* checksum present */
  54 #define GRE_RP          0x4000          /* routing present */
  55 #define GRE_KP          0x2000          /* key present */
  56 #define GRE_SP          0x1000          /* sequence# present */
  57 #define GRE_sP          0x0800          /* source routing */
  58 #define GRE_RECRS       0x0700          /* recursion count */
  59 #define GRE_AP          0x0080          /* acknowledgment# present */
  60
  61 static const struct tok gre_flag_values[] = {
  62     { GRE_CP, "checksum present"},
  63     { GRE_RP, "routing present"},
  64     { GRE_KP, "key present"},
  65     { GRE_SP, "sequence# present"},
  66     { GRE_sP, "source routing present"},
  67     { GRE_RECRS, "recursion count"},
  68     { GRE_AP, "ack present"},
  69     { 0, NULL }
  70 };
  71
  72 #define GRE_VERS_MASK   0x0007          /* protocol version */
  73
  74 /* source route entry types */
  75 #define GRESRE_IP       0x0800          /* IP */
  76 #define GRESRE_ASN      0xfffe          /* ASN */
  77
  78 static void gre_print_0(netdissect_options *, const u_char *, u_int);
  79 static void gre_print_1(netdissect_options *, const u_char *, u_int);
  80 static void gre_sre_print(netdissect_options *, uint16_t, uint8_t, uint8_t, const u_char *, u_int);
  81 static void gre_sre_ip_print(netdissect_options *, uint8_t, uint8_t, const u_char *, u_int);
  82 static void gre_sre_asn_print(netdissect_options *, uint8_t, uint8_t, const u_char *, u_int);
  83
  84 void
  85 gre_print(netdissect_options *ndo, const u_char *bp, u_int length)
  86 {
  87         u_int len = length, vers;
  88
  89         if (len < 2) {
  90                 ND_PRINT((ndo, "%s", tstr));
  91                 return;
  92         }
  93         vers = EXTRACT_16BITS(bp) & GRE_VERS_MASK;
  94         ND_PRINT((ndo, "GREv%u",vers));
  95
  96         switch(vers) {
  97         case 0:
  98             gre_print_0(ndo, bp, len);
  99             break;
 100         case 1:
 101             gre_print_1(ndo, bp, len);
 102             break;
 103         default:
 104             ND_PRINT((ndo, " ERROR: unknown-version"));
 105             break;
 106         }
 107 }
 108
 109 static void
 110 gre_print_0(netdissect_options *ndo, const u_char *bp, u_int length)
 111 {
 112         u_int len = length;
 113         uint16_t flags, prot;
 114
 115         flags = EXTRACT_16BITS(bp);
 116         if (ndo->ndo_vflag)
 117             ND_PRINT((ndo, ", Flags [%s]",
 118                    bittok2str(gre_flag_values,"none",flags)));
 119
 120         len -= 2;
 121         bp += 2;
 122
 123         if (len < 2)
 124                 goto trunc;
 125         prot = EXTRACT_16BITS(bp);
 126         len -= 2;
 127         bp += 2;
 128
 129         if ((flags & GRE_CP) | (flags & GRE_RP)) {
 130                 if (len < 2)
 131                         goto trunc;
 132                 if (ndo->ndo_vflag)
 133                         ND_PRINT((ndo, ", sum 0x%x", EXTRACT_16BITS(bp)));
 134                 bp += 2;
 135                 len -= 2;
 136
 137                 if (len < 2)
 138                         goto trunc;
 139                 ND_PRINT((ndo, ", off 0x%x", EXTRACT_16BITS(bp)));
 140                 bp += 2;
 141                 len -= 2;
 142         }
 143
 144         if (flags & GRE_KP) {
 145                 if (len < 4)
 146                         goto trunc;
 147                 ND_PRINT((ndo, ", key=0x%x", EXTRACT_32BITS(bp)));
 148                 bp += 4;
 149                 len -= 4;
 150         }
 151
 152         if (flags & GRE_SP) {
 153                 if (len < 4)
 154                         goto trunc;
 155                 ND_PRINT((ndo, ", seq %u", EXTRACT_32BITS(bp)));
 156                 bp += 4;
 157                 len -= 4;
 158         }
 159
 160         if (flags & GRE_RP) {
 161                 for (;;) {
 162                         uint16_t af;
 163                         uint8_t sreoff;
 164                         uint8_t srelen;
 165
 166                         if (len < 4)
 167                                 goto trunc;
 168                         af = EXTRACT_16BITS(bp);
 169                         sreoff = *(bp + 2);
 170                         srelen = *(bp + 3);
 171                         bp += 4;
 172                         len -= 4;
 173
 174                         if (af == 0 && srelen == 0)
 175                                 break;
 176
 177                         gre_sre_print(ndo, af, sreoff, srelen, bp, len);
 178
 179                         if (len < srelen)
 180                                 goto trunc;
 181                         bp += srelen;
 182                         len -= srelen;
 183                 }
 184         }
 185
 186         if (ndo->ndo_eflag)
 187             ND_PRINT((ndo, ", proto %s (0x%04x)",
 188                    tok2str(ethertype_values,"unknown",prot),
 189                    prot));
 190
 191         ND_PRINT((ndo, ", length %u",length));
 192
 193         if (ndo->ndo_vflag < 1)
 194             ND_PRINT((ndo, ": ")); /* put in a colon as protocol demarc */
 195         else
 196             ND_PRINT((ndo, "\n\t")); /* if verbose go multiline */
 197
 198         switch (prot) {
 199         case ETHERTYPE_IP:
 200                 ip_print(ndo, bp, len);
 201                 break;
 202         case ETHERTYPE_IPV6:
 203                 ip6_print(ndo, bp, len);
 204                 break;
 205         case ETHERTYPE_MPLS:
 206                 mpls_print(ndo, bp, len);
 207                 break;
 208         case ETHERTYPE_IPX:
 209                 ipx_print(ndo, bp, len);
 210                 break;
 211         case ETHERTYPE_ATALK:
 212                 atalk_print(ndo, bp, len);
 213                 break;
 214         case ETHERTYPE_GRE_ISO:
 215                 isoclns_print(ndo, bp, len, len);
 216                 break;
 217         case ETHERTYPE_TEB:
 218                 ether_print(ndo, bp, len, len, NULL, NULL);
 219                 break;
 220         default:
 221                 ND_PRINT((ndo, "gre-proto-0x%x", prot));
 222         }
 223         return;
 224
 225 trunc:
 226         ND_PRINT((ndo, "%s", tstr));
 227 }
 228
 229 static void
 230 gre_print_1(netdissect_options *ndo, const u_char *bp, u_int length)
 231 {
 232         u_int len = length;
 233         uint16_t flags, prot;
 234
 235         flags = EXTRACT_16BITS(bp);
 236         len -= 2;
 237         bp += 2;
 238
 239         if (ndo->ndo_vflag)
 240             ND_PRINT((ndo, ", Flags [%s]",
 241                    bittok2str(gre_flag_values,"none",flags)));
 242
 243         if (len < 2)
 244                 goto trunc;
 245         prot = EXTRACT_16BITS(bp);
 246         len -= 2;
 247         bp += 2;
 248
 249
 250         if (flags & GRE_KP) {
 251                 uint32_t k;
 252
 253                 if (len < 4)
 254                         goto trunc;
 255                 k = EXTRACT_32BITS(bp);
 256                 ND_PRINT((ndo, ", call %d", k & 0xffff));
 257                 len -= 4;
 258                 bp += 4;
 259         }
 260
 261         if (flags & GRE_SP) {
 262                 if (len < 4)
 263                         goto trunc;
 264                 ND_PRINT((ndo, ", seq %u", EXTRACT_32BITS(bp)));
 265                 bp += 4;
 266                 len -= 4;
 267         }
 268
 269         if (flags & GRE_AP) {
 270                 if (len < 4)
 271                         goto trunc;
 272                 ND_PRINT((ndo, ", ack %u", EXTRACT_32BITS(bp)));
 273                 bp += 4;
 274                 len -= 4;
 275         }
 276
 277         if ((flags & GRE_SP) == 0)
 278                 ND_PRINT((ndo, ", no-payload"));
 279
 280         if (ndo->ndo_eflag)
 281             ND_PRINT((ndo, ", proto %s (0x%04x)",
 282                    tok2str(ethertype_values,"unknown",prot),
 283                    prot));
 284
 285         ND_PRINT((ndo, ", length %u",length));
 286
 287         if ((flags & GRE_SP) == 0)
 288             return;
 289
 290         if (ndo->ndo_vflag < 1)
 291             ND_PRINT((ndo, ": ")); /* put in a colon as protocol demarc */
 292         else
 293             ND_PRINT((ndo, "\n\t")); /* if verbose go multiline */
 294
 295         switch (prot) {
 296         case ETHERTYPE_PPP:
 297                 ppp_print(ndo, bp, len);
 298                 break;
 299         default:
 300                 ND_PRINT((ndo, "gre-proto-0x%x", prot));
 301                 break;
 302         }
 303         return;
 304
 305 trunc:
 306         ND_PRINT((ndo, "%s", tstr));
 307 }
 308
 309 static void
 310 gre_sre_print(netdissect_options *ndo, uint16_t af, uint8_t sreoff,
 311     uint8_t srelen, const u_char *bp, u_int len)
 312 {
 313         switch (af) {
 314         case GRESRE_IP:
 315                 ND_PRINT((ndo, ", (rtaf=ip"));
 316                 gre_sre_ip_print(ndo, sreoff, srelen, bp, len);
 317                 ND_PRINT((ndo, ")"));
 318                 break;
 319         case GRESRE_ASN:
 320                 ND_PRINT((ndo, ", (rtaf=asn"));
 321                 gre_sre_asn_print(ndo, sreoff, srelen, bp, len);
 322                 ND_PRINT((ndo, ")"));
 323                 break;
 324         default:
 325                 ND_PRINT((ndo, ", (rtaf=0x%x)", af));
 326         }
 327 }
 328
 329 static void
 330 gre_sre_ip_print(netdissect_options *ndo, uint8_t sreoff, uint8_t srelen,
 331                  const u_char *bp, u_int len)
 332 {
 333         struct in_addr a;
 334         const u_char *up = bp;
 335
 336         if (sreoff & 3) {
 337                 ND_PRINT((ndo, ", badoffset=%u", sreoff));
 338                 return;
 339         }
 340         if (srelen & 3) {
 341                 ND_PRINT((ndo, ", badlength=%u", srelen));
 342                 return;
 343         }
 344         if (sreoff >= srelen) {
 345                 ND_PRINT((ndo, ", badoff/len=%u/%u", sreoff, srelen));
 346                 return;
 347         }
 348
 349         for (;;) {
 350                 if (len < 4 || srelen == 0)
 351                         return;
 352
 353                 memcpy(&a, bp, sizeof(a));
 354                 ND_PRINT((ndo, " %s%s",
 355                     ((bp - up) == sreoff) ? "*" : "",
 356                     inet_ntoa(a)));
 357
 358                 bp += 4;
 359                 len -= 4;
 360                 srelen -= 4;
 361         }
 362 }
 363
 364 static void
 365 gre_sre_asn_print(netdissect_options *ndo, uint8_t sreoff, uint8_t srelen,
 366                   const u_char *bp, u_int len)
 367 {
 368         const u_char *up = bp;
 369
 370         if (sreoff & 1) {
 371                 ND_PRINT((ndo, ", badoffset=%u", sreoff));
 372                 return;
 373         }
 374         if (srelen & 1) {
 375                 ND_PRINT((ndo, ", badlength=%u", srelen));
 376                 return;
 377         }
 378         if (sreoff >= srelen) {
 379                 ND_PRINT((ndo, ", badoff/len=%u/%u", sreoff, srelen));
 380                 return;
 381         }
 382
 383         for (;;) {
 384                 if (len < 2 || srelen == 0)
 385                         return;
 386
 387                 ND_PRINT((ndo, " %s%x",
 388                     ((bp - up) == sreoff) ? "*" : "",
 389                     EXTRACT_16BITS(bp)));
 390
 391                 bp += 2;
 392                 len -= 2;
 393                 srelen -= 2;
 394         }
 395 }