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   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_CDP                 0x2000  /* Cisco Discovery Protocol */
  88 #define GRE_NHRP                0x2001  /* Next Hop Resolution Protocol */
  89 #define GRE_ERSPAN_III          0x22eb
  90 #define GRE_WCCP                0x883e  /* Web Cache C* Protocol */
  91 #define GRE_ERSPAN_I_II         0x88be
  92
  93 struct wccp_redirect {
  94         nd_uint8_t      flags;
  95 #define WCCP_T                  (1 << 7)
  96 #define WCCP_A                  (1 << 6)
  97 #define WCCP_U                  (1 << 5)
  98         nd_uint8_t      ServiceId;
  99         nd_uint8_t      AltBucket;
 100         nd_uint8_t      PriBucket;
 101 };
 102
 103 static void gre_print_0(netdissect_options *, const u_char *, u_int);
 104 static void gre_print_1(netdissect_options *, const u_char *, u_int);
 105 static int gre_sre_print(netdissect_options *, uint16_t, uint8_t, uint8_t, const u_char *, u_int);
 106 static int gre_sre_ip_print(netdissect_options *, uint8_t, uint8_t, const u_char *, u_int);
 107 static int gre_sre_asn_print(netdissect_options *, uint8_t, uint8_t, const u_char *, u_int);
 108
 109 void
 110 gre_print(netdissect_options *ndo, const u_char *bp, u_int length)
 111 {
 112         u_int vers;
 113
 114         ndo->ndo_protocol = "gre";
 115         nd_print_protocol_caps(ndo);
 116         ND_ICHECK_U(length, <, 2);
 117         vers = GET_BE_U_2(bp) & GRE_VERS_MASK;
 118         ND_PRINT("v%u",vers);
 119
 120         switch(vers) {
 121         case 0:
 122                 gre_print_0(ndo, bp, length);
 123                 break;
 124         case 1:
 125                 gre_print_1(ndo, bp, length);
 126                 break;
 127         default:
 128                 ND_PRINT(" ERROR: unknown-version");
 129                 break;
 130         }
 131         return;
 132
 133 invalid:
 134         nd_print_invalid(ndo);
 135 }
 136
 137 static void
 138 gre_print_0(netdissect_options *ndo, const u_char *bp, u_int length)
 139 {
 140         u_int len = length;
 141         uint16_t flags, prot;
 142
 143         ND_ICHECK_U(len, <, 2);
 144         flags = GET_BE_U_2(bp);
 145         if (ndo->ndo_vflag)
 146                 ND_PRINT(", Flags [%s]",
 147                          bittok2str(gre_flag_values,"none",flags));
 148
 149         len -= 2;
 150         bp += 2;
 151
 152         ND_ICHECK_U(len, <, 2);
 153         prot = GET_BE_U_2(bp);
 154         len -= 2;
 155         bp += 2;
 156
 157         if ((flags & GRE_CP) | (flags & GRE_RP)) {
 158                 uint16_t sum;
 159
 160                 ND_ICHECK_U(len, <, 2);
 161                 sum =  GET_BE_U_2(bp);
 162                 if (ndo->ndo_vflag)
 163                         ND_PRINT(", sum 0x%x", sum);
 164                 bp += 2;
 165                 len -= 2;
 166
 167                 ND_ICHECK_U(len, <, 2);
 168                 ND_PRINT(", off 0x%x", GET_BE_U_2(bp));
 169                 bp += 2;
 170                 len -= 2;
 171         }
 172
 173         if (flags & GRE_KP) {
 174                 uint32_t key;
 175
 176                 ND_ICHECK_U(len, <, 4);
 177                 key = GET_BE_U_4(bp);
 178                 bp += 4;
 179                 len -= 4;
 180
 181                 /*
 182                  * OpenBSD shows this as both a 32-bit
 183                  * (decimal) key value and a VSID+FlowID
 184                  * pair, with the VSID in decimal and
 185                  * the FlowID in hex, as key=<Key>|<VSID>+<FlowID>,
 186                  * in case this is NVGRE.
 187                  */
 188                 ND_PRINT(", key=0x%x", key);
 189         }
 190
 191         if (flags & GRE_SP) {
 192                 ND_ICHECK_U(len, <, 4);
 193                 ND_PRINT(", seq %u", GET_BE_U_4(bp));
 194                 bp += 4;
 195                 len -= 4;
 196         }
 197
 198         if (flags & GRE_RP) {
 199                 for (;;) {
 200                         uint16_t af;
 201                         uint8_t sreoff;
 202                         uint8_t srelen;
 203
 204                         ND_ICHECK_U(len, <, 4);
 205                         af = GET_BE_U_2(bp);
 206                         sreoff = GET_U_1(bp + 2);
 207                         srelen = GET_U_1(bp + 3);
 208                         bp += 4;
 209                         len -= 4;
 210
 211                         if (af == 0 && srelen == 0)
 212                                 break;
 213
 214                         if (!gre_sre_print(ndo, af, sreoff, srelen, bp, len))
 215                                 goto invalid;
 216
 217                         ND_ICHECK_U(len, <, srelen);
 218                         bp += srelen;
 219                         len -= srelen;
 220                 }
 221         }
 222
 223         if (ndo->ndo_eflag)
 224                 ND_PRINT(", proto %s (0x%04x)",
 225                          tok2str(ethertype_values,"unknown",prot), prot);
 226
 227         ND_PRINT(", length %u",length);
 228
 229         if (ndo->ndo_vflag < 1)
 230                 ND_PRINT(": "); /* put in a colon as protocol demarc */
 231         else
 232                 ND_PRINT("\n\t"); /* if verbose go multiline */
 233
 234         switch (prot) {
 235         case 0x0000:
 236                 /*
 237                  * 0x0000 is reserved, but Cisco, at least, appears to
 238                  * use it for keep-alives; see, for example,
 239                  * https://www.cisco.com/c/en/us/support/docs/ip/generic-routing-encapsulation-gre/118370-technote-gre-00.html#anc1
 240                  */
 241                 printf("keep-alive");
 242                 break;
 243         case GRE_WCCP:
 244                 /*
 245                  * This is a bit weird.
 246                  *
 247                  * This may either just mean "IPv4" or it may mean
 248                  * "IPv4 preceded by a WCCP redirect header".  We
 249                  * check to see if the first octet looks like the
 250                  * beginning of an IPv4 header and, if not, dissect
 251                  * it "IPv4 preceded by a WCCP redirect header",
 252                  * otherwise we dissect it as just IPv4.
 253                  *
 254                  * See "Packet redirection" in draft-forster-wrec-wccp-v1-00,
 255                  * section 4.12 "Traffic Forwarding" in
 256                  * draft-wilson-wrec-wccp-v2-01, and section 3.12.1
 257                  * "Forwarding using GRE Encapsulation" in
 258                  * draft-param-wccp-v2rev1-01.
 259                  */
 260                 ND_PRINT("wccp ");
 261
 262                 ND_ICHECK_U(len, <, 1);
 263                 if (GET_U_1(bp) >> 4 != 4) {
 264                         /*
 265                          * First octet isn't 0x4*, so it's not IPv4.
 266                          */
 267                         const struct wccp_redirect *wccp;
 268                         uint8_t wccp_flags;
 269
 270                         ND_ICHECK_ZU(len, <, sizeof(*wccp));
 271                         wccp = (const struct wccp_redirect *)bp;
 272                         wccp_flags = GET_U_1(wccp->flags);
 273
 274                         ND_PRINT("T:%c A:%c U:%c SId:%u Alt:%u Pri:%u",
 275                             (wccp_flags & WCCP_T) ? '1' : '0',
 276                             (wccp_flags & WCCP_A) ? '1' : '0',
 277                             (wccp_flags & WCCP_U) ? '1' : '0',
 278                             GET_U_1(wccp->ServiceId),
 279                             GET_U_1(wccp->AltBucket),
 280                             GET_U_1(wccp->PriBucket));
 281
 282                         bp += sizeof(*wccp);
 283                         len -= sizeof(*wccp);
 284
 285                         printf(": ");
 286                 }
 287                 /* FALLTHROUGH */
 288         case ETHERTYPE_IP:
 289                 ip_print(ndo, bp, len);
 290                 break;
 291         case ETHERTYPE_IPV6:
 292                 ip6_print(ndo, bp, len);
 293                 break;
 294         case ETHERTYPE_MPLS:
 295         case ETHERTYPE_MPLS_MULTI:
 296                 mpls_print(ndo, bp, len);
 297                 break;
 298         case ETHERTYPE_IPX:
 299                 ipx_print(ndo, bp, len);
 300                 break;
 301         case ETHERTYPE_ATALK:
 302                 atalk_print(ndo, bp, len);
 303                 break;
 304         case ETHERTYPE_GRE_ISO:
 305                 isoclns_print(ndo, bp, len);
 306                 break;
 307         case ETHERTYPE_TEB:
 308                 ether_print(ndo, bp, len, ND_BYTES_AVAILABLE_AFTER(bp), NULL, NULL);
 309                 break;
 310         case ETHERTYPE_NSH:
 311                 nsh_print(ndo, bp, len);
 312                 break;
 313         case GRE_ERSPAN_I_II:
 314                 erspan_print(ndo, flags, bp, len);
 315                 break;
 316         case GRE_CDP:
 317                 cdp_print(ndo, bp, len);
 318                 break;
 319         case GRE_NHRP:
 320                 nhrp_print(ndo, bp, len);
 321                 break;
 322         default:
 323                 ND_PRINT("gre-proto-0x%x", prot);
 324         }
 325         return;
 326
 327 invalid:
 328         nd_print_invalid(ndo);
 329 }
 330
 331 static void
 332 gre_print_1(netdissect_options *ndo, const u_char *bp, u_int length)
 333 {
 334         u_int len = length;
 335         uint16_t flags, prot;
 336
 337         ND_ICHECK_U(len, <, 2);
 338         flags = GET_BE_U_2(bp);
 339         len -= 2;
 340         bp += 2;
 341
 342         if (ndo->ndo_vflag)
 343                 ND_PRINT(", Flags [%s]",
 344                          bittok2str(gre_flag_values,"none",flags));
 345
 346         ND_ICHECK_U(len, <, 2);
 347         prot = GET_BE_U_2(bp);
 348         len -= 2;
 349         bp += 2;
 350
 351         if (flags & GRE_KP) {
 352                 /* Skip payload length? */
 353                 ND_ICHECK_U(len, <, 2);
 354                 ND_TCHECK_LEN(bp, 2);
 355                 len -= 2;
 356                 bp += 2;
 357
 358                 ND_ICHECK_U(len, <, 2);
 359                 ND_PRINT(", call %u", GET_BE_U_2(bp));
 360                 len -= 2;
 361                 bp += 2;
 362         } else
 363                 ND_PRINT(", (ERROR: K flag not set)");
 364
 365         if (flags & GRE_SP) {
 366                 ND_ICHECK_U(len, <, 4);
 367                 ND_PRINT(", seq %u", GET_BE_U_4(bp));
 368                 bp += 4;
 369                 len -= 4;
 370         }
 371
 372         if (flags & GRE_AP) {
 373                 ND_ICHECK_U(len, <, 4);
 374                 ND_PRINT(", ack %u", GET_BE_U_4(bp));
 375                 bp += 4;
 376                 len -= 4;
 377         }
 378
 379         if ((flags & GRE_SP) == 0)
 380                 ND_PRINT(", no-payload");
 381
 382         if (ndo->ndo_eflag)
 383                 ND_PRINT(", proto %s (0x%04x)",
 384                          tok2str(ethertype_values,"unknown",prot), prot);
 385
 386         ND_PRINT(", length %u",length);
 387
 388         if ((flags & GRE_SP) == 0)
 389                 return;
 390
 391         if (ndo->ndo_vflag < 1)
 392                 ND_PRINT(": "); /* put in a colon as protocol demarc */
 393         else
 394                 ND_PRINT("\n\t"); /* if verbose go multiline */
 395
 396         switch (prot) {
 397         case ETHERTYPE_PPP:
 398                 ppp_print(ndo, bp, len);
 399                 break;
 400         default:
 401                 ND_PRINT("gre-proto-0x%x", prot);
 402                 break;
 403         }
 404         return;
 405
 406 invalid:
 407         nd_print_invalid(ndo);
 408 }
 409
 410 static int
 411 gre_sre_print(netdissect_options *ndo, uint16_t af, uint8_t sreoff,
 412               uint8_t srelen, const u_char *bp, u_int len)
 413 {
 414         int ret;
 415
 416         switch (af) {
 417         case GRESRE_IP:
 418                 ND_PRINT(", (rtaf=ip");
 419                 ret = gre_sre_ip_print(ndo, sreoff, srelen, bp, len);
 420                 ND_PRINT(")");
 421                 break;
 422         case GRESRE_ASN:
 423                 ND_PRINT(", (rtaf=asn");
 424                 ret = gre_sre_asn_print(ndo, sreoff, srelen, bp, len);
 425                 ND_PRINT(")");
 426                 break;
 427         default:
 428                 ND_PRINT(", (rtaf=0x%x)", af);
 429                 ret = 1;
 430         }
 431         return (ret);
 432 }
 433
 434 static int
 435 gre_sre_ip_print(netdissect_options *ndo, uint8_t sreoff, uint8_t srelen,
 436                  const u_char *bp, u_int len)
 437 {
 438         const u_char *up = bp;
 439         char buf[INET_ADDRSTRLEN];
 440
 441         if (sreoff & 3) {
 442                 ND_PRINT(", badoffset=%u", sreoff);
 443                 goto invalid;
 444         }
 445         if (srelen & 3) {
 446                 ND_PRINT(", badlength=%u", srelen);
 447                 goto invalid;
 448         }
 449         if (sreoff >= srelen) {
 450                 ND_PRINT(", badoff/len=%u/%u", sreoff, srelen);
 451                 goto invalid;
 452         }
 453
 454         while (srelen != 0) {
 455                 ND_ICHECK_U(len, <, 4);
 456
 457                 ND_TCHECK_LEN(bp, sizeof(nd_ipv4));
 458                 addrtostr(bp, buf, sizeof(buf));
 459                 ND_PRINT(" %s%s",
 460                          ((bp - up) == sreoff) ? "*" : "", buf);
 461
 462                 bp += 4;
 463                 len -= 4;
 464                 srelen -= 4;
 465         }
 466         return 1;
 467
 468 invalid:
 469         return 0;
 470 }
 471
 472 static int
 473 gre_sre_asn_print(netdissect_options *ndo, uint8_t sreoff, uint8_t srelen,
 474                   const u_char *bp, u_int len)
 475 {
 476         const u_char *up = bp;
 477
 478         if (sreoff & 1) {
 479                 ND_PRINT(", badoffset=%u", sreoff);
 480                 goto invalid;
 481         }
 482         if (srelen & 1) {
 483                 ND_PRINT(", badlength=%u", srelen);
 484                 goto invalid;
 485         }
 486         if (sreoff >= srelen) {
 487                 ND_PRINT(", badoff/len=%u/%u", sreoff, srelen);
 488                 goto invalid;
 489         }
 490
 491         while (srelen != 0) {
 492                 ND_ICHECK_U(len, <, 2);
 493
 494                 ND_PRINT(" %s%x",
 495                          ((bp - up) == sreoff) ? "*" : "", GET_BE_U_2(bp));
 496
 497                 bp += 2;
 498                 len -= 2;
 499                 srelen -= 2;
 500         }
 501         return 1;
 502
 503 invalid:
 504         return 0;
 505 }