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  *
  16  * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
  17  * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
  18  * WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
  19  * DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT,
  20  * INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
  21  * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
  22  * SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
  23  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
  24  * STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
  25  * ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
  26  * POSSIBILITY OF SUCH DAMAGE.
  27  */
  28
  29 /* \summary: Generic Routing Encapsulation (GRE) printer */
  30
  31 /*
  32  * netdissect printer for GRE - Generic Routing Encapsulation
  33  * RFC 1701 (GRE), RFC 1702 (GRE IPv4), RFC 2637 (PPTP, which
  34  * has an extended form of GRE), RFC 2784 (revised GRE, with
  35  * R, K, S, and s bits and Recur and Offset fields now reserved
  36  * in the header, and no optional Key or Sequence number in the
  37  * header), and RFC 2890 (proposal to add back the K and S bits
  38  * and the optional Key and Sequence number).
  39  *
  40  * The RFC 2637 PPTP GRE repurposes the Key field to hold a
  41  * 16-bit Payload Length and a 16-bit Call ID.
  42  *
  43  * RFC 7637 (NVGRE) repurposes the Key field to hold a 24-bit
  44  * Virtual Subnet ID (VSID) and an 8-bit FlowID.
  45  */
  46
  47 #ifdef HAVE_CONFIG_H
  48 #include <config.h>
  49 #endif
  50
  51 #include "netdissect-stdinc.h"
  52
  53 #define ND_LONGJMP_FROM_TCHECK
  54 #include "netdissect.h"
  55 #include "addrtostr.h"
  56 #include "extract.h"
  57 #include "ethertype.h"
  58
  59
  60 #define GRE_CP          0x8000          /* checksum present */
  61 #define GRE_RP          0x4000          /* routing present */
  62 #define GRE_KP          0x2000          /* key present */
  63 #define GRE_SP          0x1000          /* sequence# present */
  64 #define GRE_sP          0x0800          /* source routing */
  65 #define GRE_AP          0x0080          /* acknowledgment# present */
  66
  67 static const struct tok gre_flag_values[] = {
  68     { GRE_CP, "checksum present"},
  69     { GRE_RP, "routing present"},
  70     { GRE_KP, "key present"},
  71     { GRE_SP, "sequence# present"},
  72     { GRE_sP, "source routing present"},
  73     { GRE_AP, "ack present"},
  74     { 0, NULL }
  75 };
  76
  77 #define GRE_RECRS_MASK  0x0700          /* recursion count */
  78 #define GRE_VERS_MASK   0x0007          /* protocol version */
  79
  80 /* source route entry types */
  81 #define GRESRE_IP       0x0800          /* IP */
  82 #define GRESRE_ASN      0xfffe          /* ASN */
  83
  84 /*
  85  * Ethertype values used for GRE (but not elsewhere?).
  86  */
  87 #define GRE_WCCP                0x883e  /* Web Cache C* Protocol */
  88
  89 struct wccp_redirect {
  90         nd_uint8_t      flags;
  91 #define WCCP_T                  (1 << 7)
  92 #define WCCP_A                  (1 << 6)
  93 #define WCCP_U                  (1 << 5)
  94         nd_uint8_t      ServiceId;
  95         nd_uint8_t      AltBucket;
  96         nd_uint8_t      PriBucket;
  97 };
  98
  99 static void gre_print_0(netdissect_options *, const u_char *, u_int);
 100 static void gre_print_1(netdissect_options *, const u_char *, u_int);
 101 static int gre_sre_print(netdissect_options *, uint16_t, uint8_t, uint8_t, const u_char *, u_int);
 102 static int gre_sre_ip_print(netdissect_options *, uint8_t, uint8_t, const u_char *, u_int);
 103 static int gre_sre_asn_print(netdissect_options *, uint8_t, uint8_t, const u_char *, u_int);
 104
 105 void
 106 gre_print(netdissect_options *ndo, const u_char *bp, u_int length)
 107 {
 108         u_int vers;
 109
 110         ndo->ndo_protocol = "gre";
 111         nd_print_protocol_caps(ndo);
 112         ND_ICHECK_U(length, <, 2);
 113         vers = GET_BE_U_2(bp) & GRE_VERS_MASK;
 114         ND_PRINT("v%u",vers);
 115
 116         switch(vers) {
 117         case 0:
 118                 gre_print_0(ndo, bp, length);
 119                 break;
 120         case 1:
 121                 gre_print_1(ndo, bp, length);
 122                 break;
 123         default:
 124                 ND_PRINT(" ERROR: unknown-version");
 125                 break;
 126         }
 127         return;
 128
 129 invalid:
 130         nd_print_invalid(ndo);
 131 }
 132
 133 static void
 134 gre_print_0(netdissect_options *ndo, const u_char *bp, u_int length)
 135 {
 136         u_int len = length;
 137         uint16_t flags, prot;
 138
 139         ND_ICHECK_U(len, <, 2);
 140         flags = GET_BE_U_2(bp);
 141         if (ndo->ndo_vflag)
 142                 ND_PRINT(", Flags [%s]",
 143                          bittok2str(gre_flag_values,"none",flags));
 144
 145         len -= 2;
 146         bp += 2;
 147
 148         ND_ICHECK_U(len, <, 2);
 149         prot = GET_BE_U_2(bp);
 150         len -= 2;
 151         bp += 2;
 152
 153         if ((flags & GRE_CP) | (flags & GRE_RP)) {
 154                 uint16_t sum;
 155
 156                 ND_ICHECK_U(len, <, 2);
 157                 sum =  GET_BE_U_2(bp);
 158                 if (ndo->ndo_vflag)
 159                         ND_PRINT(", sum 0x%x", sum);
 160                 bp += 2;
 161                 len -= 2;
 162
 163                 ND_ICHECK_U(len, <, 2);
 164                 ND_PRINT(", off 0x%x", GET_BE_U_2(bp));
 165                 bp += 2;
 166                 len -= 2;
 167         }
 168
 169         if (flags & GRE_KP) {
 170                 uint32_t key;
 171
 172                 ND_ICHECK_U(len, <, 4);
 173                 key = GET_BE_U_4(bp);
 174                 bp += 4;
 175                 len -= 4;
 176
 177                 /*
 178                  * OpenBSD shows this as both a 32-bit
 179                  * (decimal) key value and a VSID+FlowID
 180                  * pair, with the VSID in decimal and
 181                  * the FlowID in hex, as key=<Key>|<VSID>+<FlowID>,
 182                  * in case this is NVGRE.
 183                  */
 184                 ND_PRINT(", key=0x%x", key);
 185         }
 186
 187         if (flags & GRE_SP) {
 188                 ND_ICHECK_U(len, <, 4);
 189                 ND_PRINT(", seq %u", GET_BE_U_4(bp));
 190                 bp += 4;
 191                 len -= 4;
 192         }
 193
 194         if (flags & GRE_RP) {
 195                 for (;;) {
 196                         uint16_t af;
 197                         uint8_t sreoff;
 198                         uint8_t srelen;
 199
 200                         ND_ICHECK_U(len, <, 4);
 201                         af = GET_BE_U_2(bp);
 202                         sreoff = GET_U_1(bp + 2);
 203                         srelen = GET_U_1(bp + 3);
 204                         bp += 4;
 205                         len -= 4;
 206
 207                         if (af == 0 && srelen == 0)
 208                                 break;
 209
 210                         if (!gre_sre_print(ndo, af, sreoff, srelen, bp, len))
 211                                 goto invalid;
 212
 213                         ND_ICHECK_U(len, <, srelen);
 214                         bp += srelen;
 215                         len -= srelen;
 216                 }
 217         }
 218
 219         if (ndo->ndo_eflag)
 220                 ND_PRINT(", proto %s (0x%04x)",
 221                          tok2str(ethertype_values,"unknown",prot), prot);
 222
 223         ND_PRINT(", length %u",length);
 224
 225         if (ndo->ndo_vflag < 1)
 226                 ND_PRINT(": "); /* put in a colon as protocol demarc */
 227         else
 228                 ND_PRINT("\n\t"); /* if verbose go multiline */
 229
 230         switch (prot) {
 231         case 0x0000:
 232                 /*
 233                  * 0x0000 is reserved, but Cisco, at least, appears to
 234                  * use it for keep-alives; see, for example,
 235                  * https://www.cisco.com/c/en/us/support/docs/ip/generic-routing-encapsulation-gre/118370-technote-gre-00.html#anc1
 236                  */
 237                 printf("keep-alive");
 238                 break;
 239         case GRE_WCCP:
 240                 /*
 241                  * This is a bit weird.
 242                  *
 243                  * This may either just mean "IPv4" or it may mean
 244                  * "IPv4 preceded by a WCCP redirect header".  We
 245                  * check to seeif the first octet looks like the
 246                  * beginning of an IPv4 header and, if not, dissect
 247                  * it "IPv4 preceded by a WCCP redirect header",
 248                  * otherwise we dissect it as just IPv4.
 249                  *
 250                  * See "Packet redirection" in draft-forster-wrec-wccp-v1-00,
 251                  * scetion 4.12 "Traffic Forwarding" in
 252                  * draft-wilson-wrec-wccp-v2-01, and section 3.12.1
 253                  * "Forwarding using GRE Encapsulation" in
 254                  * draft-param-wccp-v2rev1-01.
 255                  */
 256                 ND_PRINT("wccp ");
 257
 258                 ND_ICHECK_U(len, <, 1);
 259                 if (GET_U_1(bp) >> 4 != 4) {
 260                         /*
 261                          * First octet isn't 0x4*, so it's not IPv4.
 262                          */
 263                         const struct wccp_redirect *wccp;
 264                         uint8_t wccp_flags;
 265
 266                         ND_ICHECK_ZU(len, <, sizeof(*wccp));
 267                         wccp = (const struct wccp_redirect *)bp;
 268                         wccp_flags = GET_U_1(wccp->flags);
 269
 270                         ND_PRINT("T:%c A:%c U:%c SId:%u Alt:%u Pri:%u",
 271                             (wccp_flags & WCCP_T) ? '1' : '0',
 272                             (wccp_flags & WCCP_A) ? '1' : '0',
 273                             (wccp_flags & WCCP_U) ? '1' : '0',
 274                             GET_U_1(wccp->ServiceId),
 275                             GET_U_1(wccp->AltBucket),
 276                             GET_U_1(wccp->PriBucket));
 277
 278                         bp += sizeof(*wccp);
 279                         len -= sizeof(*wccp);
 280
 281                         printf(": ");
 282                 }
 283                 /* FALLTHROUGH */
 284                 break;
 285         case ETHERTYPE_IP:
 286                 ip_print(ndo, bp, len);
 287                 break;
 288         case ETHERTYPE_IPV6:
 289                 ip6_print(ndo, bp, len);
 290                 break;
 291         case ETHERTYPE_MPLS:
 292         case ETHERTYPE_MPLS_MULTI:
 293                 mpls_print(ndo, bp, len);
 294                 break;
 295         case ETHERTYPE_IPX:
 296                 ipx_print(ndo, bp, len);
 297                 break;
 298         case ETHERTYPE_ATALK:
 299                 atalk_print(ndo, bp, len);
 300                 break;
 301         case ETHERTYPE_GRE_ISO:
 302                 isoclns_print(ndo, bp, len);
 303                 break;
 304         case ETHERTYPE_TEB:
 305                 ether_print(ndo, bp, len, ND_BYTES_AVAILABLE_AFTER(bp), NULL, NULL);
 306                 break;
 307         default:
 308                 ND_PRINT("gre-proto-0x%x", prot);
 309         }
 310         return;
 311
 312 invalid:
 313         nd_print_invalid(ndo);
 314 }
 315
 316 static void
 317 gre_print_1(netdissect_options *ndo, const u_char *bp, u_int length)
 318 {
 319         u_int len = length;
 320         uint16_t flags, prot;
 321
 322         ND_ICHECK_U(len, <, 2);
 323         flags = GET_BE_U_2(bp);
 324         len -= 2;
 325         bp += 2;
 326
 327         if (ndo->ndo_vflag)
 328                 ND_PRINT(", Flags [%s]",
 329                          bittok2str(gre_flag_values,"none",flags));
 330
 331         ND_ICHECK_U(len, <, 2);
 332         prot = GET_BE_U_2(bp);
 333         len -= 2;
 334         bp += 2;
 335
 336
 337         if (flags & GRE_KP) {
 338                 uint32_t k;
 339
 340                 ND_ICHECK_U(len, <, 4);
 341                 k = GET_BE_U_4(bp);
 342                 ND_PRINT(", call %u", k & 0xffff);
 343                 len -= 4;
 344                 bp += 4;
 345         }
 346
 347         if (flags & GRE_SP) {
 348                 ND_ICHECK_U(len, <, 4);
 349                 ND_PRINT(", seq %u", GET_BE_U_4(bp));
 350                 bp += 4;
 351                 len -= 4;
 352         }
 353
 354         if (flags & GRE_AP) {
 355                 ND_ICHECK_U(len, <, 4);
 356                 ND_PRINT(", ack %u", GET_BE_U_4(bp));
 357                 bp += 4;
 358                 len -= 4;
 359         }
 360
 361         if ((flags & GRE_SP) == 0)
 362                 ND_PRINT(", no-payload");
 363
 364         if (ndo->ndo_eflag)
 365                 ND_PRINT(", proto %s (0x%04x)",
 366                          tok2str(ethertype_values,"unknown",prot), prot);
 367
 368         ND_PRINT(", length %u",length);
 369
 370         if ((flags & GRE_SP) == 0)
 371                 return;
 372
 373         if (ndo->ndo_vflag < 1)
 374                 ND_PRINT(": "); /* put in a colon as protocol demarc */
 375         else
 376                 ND_PRINT("\n\t"); /* if verbose go multiline */
 377
 378         switch (prot) {
 379         case ETHERTYPE_PPP:
 380                 ppp_print(ndo, bp, len);
 381                 break;
 382         default:
 383                 ND_PRINT("gre-proto-0x%x", prot);
 384                 break;
 385         }
 386         return;
 387
 388 invalid:
 389         nd_print_invalid(ndo);
 390 }
 391
 392 static int
 393 gre_sre_print(netdissect_options *ndo, uint16_t af, uint8_t sreoff,
 394               uint8_t srelen, const u_char *bp, u_int len)
 395 {
 396         int ret;
 397
 398         switch (af) {
 399         case GRESRE_IP:
 400                 ND_PRINT(", (rtaf=ip");
 401                 ret = gre_sre_ip_print(ndo, sreoff, srelen, bp, len);
 402                 ND_PRINT(")");
 403                 break;
 404         case GRESRE_ASN:
 405                 ND_PRINT(", (rtaf=asn");
 406                 ret = gre_sre_asn_print(ndo, sreoff, srelen, bp, len);
 407                 ND_PRINT(")");
 408                 break;
 409         default:
 410                 ND_PRINT(", (rtaf=0x%x)", af);
 411                 ret = 1;
 412         }
 413         return (ret);
 414 }
 415
 416 static int
 417 gre_sre_ip_print(netdissect_options *ndo, uint8_t sreoff, uint8_t srelen,
 418                  const u_char *bp, u_int len)
 419 {
 420         const u_char *up = bp;
 421         char buf[INET_ADDRSTRLEN];
 422
 423         if (sreoff & 3) {
 424                 ND_PRINT(", badoffset=%u", sreoff);
 425                 goto invalid;
 426         }
 427         if (srelen & 3) {
 428                 ND_PRINT(", badlength=%u", srelen);
 429                 goto invalid;
 430         }
 431         if (sreoff >= srelen) {
 432                 ND_PRINT(", badoff/len=%u/%u", sreoff, srelen);
 433                 goto invalid;
 434         }
 435
 436         while (srelen != 0) {
 437                 ND_ICHECK_U(len, <, 4);
 438
 439                 ND_TCHECK_LEN(bp, sizeof(nd_ipv4));
 440                 addrtostr(bp, buf, sizeof(buf));
 441                 ND_PRINT(" %s%s",
 442                          ((bp - up) == sreoff) ? "*" : "", buf);
 443
 444                 bp += 4;
 445                 len -= 4;
 446                 srelen -= 4;
 447         }
 448         return 1;
 449
 450 invalid:
 451         return 0;
 452 }
 453
 454 static int
 455 gre_sre_asn_print(netdissect_options *ndo, uint8_t sreoff, uint8_t srelen,
 456                   const u_char *bp, u_int len)
 457 {
 458         const u_char *up = bp;
 459
 460         if (sreoff & 1) {
 461                 ND_PRINT(", badoffset=%u", sreoff);
 462                 goto invalid;
 463         }
 464         if (srelen & 1) {
 465                 ND_PRINT(", badlength=%u", srelen);
 466                 goto invalid;
 467         }
 468         if (sreoff >= srelen) {
 469                 ND_PRINT(", badoff/len=%u/%u", sreoff, srelen);
 470                 goto invalid;
 471         }
 472
 473         while (srelen != 0) {
 474                 ND_ICHECK_U(len, <, 2);
 475
 476                 ND_PRINT(" %s%x",
 477                          ((bp - up) == sreoff) ? "*" : "", GET_BE_U_2(bp));
 478
 479                 bp += 2;
 480                 len -= 2;
 481                 srelen -= 2;
 482         }
 483         return 1;
 484
 485 invalid:
 486         return 0;
 487 }