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