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 static void gre_print_0(netdissect_options *, const u_char *, u_int);
  85 static void gre_print_1(netdissect_options *, const u_char *, u_int);
  86 static int gre_sre_print(netdissect_options *, uint16_t, uint8_t, uint8_t, const u_char *, u_int);
  87 static int gre_sre_ip_print(netdissect_options *, uint8_t, uint8_t, const u_char *, u_int);
  88 static int gre_sre_asn_print(netdissect_options *, uint8_t, uint8_t, const u_char *, u_int);
  89
  90 void
  91 gre_print(netdissect_options *ndo, const u_char *bp, u_int length)
  92 {
  93         u_int vers;
  94
  95         ndo->ndo_protocol = "gre";
  96         nd_print_protocol_caps(ndo);
  97         ND_ICHECK_U(length, <, 2);
  98         vers = GET_BE_U_2(bp) & GRE_VERS_MASK;
  99         ND_PRINT("v%u",vers);
 100
 101         switch(vers) {
 102         case 0:
 103                 gre_print_0(ndo, bp, length);
 104                 break;
 105         case 1:
 106                 gre_print_1(ndo, bp, length);
 107                 break;
 108         default:
 109                 ND_PRINT(" ERROR: unknown-version");
 110                 break;
 111         }
 112         return;
 113
 114 invalid:
 115         nd_print_invalid(ndo);
 116 }
 117
 118 static void
 119 gre_print_0(netdissect_options *ndo, const u_char *bp, u_int length)
 120 {
 121         u_int len = length;
 122         uint16_t flags, prot;
 123
 124         ND_ICHECK_U(len, <, 2);
 125         flags = GET_BE_U_2(bp);
 126         if (ndo->ndo_vflag)
 127                 ND_PRINT(", Flags [%s]",
 128                          bittok2str(gre_flag_values,"none",flags));
 129
 130         len -= 2;
 131         bp += 2;
 132
 133         ND_ICHECK_U(len, <, 2);
 134         prot = GET_BE_U_2(bp);
 135         len -= 2;
 136         bp += 2;
 137
 138         if ((flags & GRE_CP) | (flags & GRE_RP)) {
 139                 uint16_t sum;
 140
 141                 ND_ICHECK_U(len, <, 2);
 142                 sum =  GET_BE_U_2(bp);
 143                 if (ndo->ndo_vflag)
 144                         ND_PRINT(", sum 0x%x", sum);
 145                 bp += 2;
 146                 len -= 2;
 147
 148                 ND_ICHECK_U(len, <, 2);
 149                 ND_PRINT(", off 0x%x", GET_BE_U_2(bp));
 150                 bp += 2;
 151                 len -= 2;
 152         }
 153
 154         if (flags & GRE_KP) {
 155                 uint32_t key;
 156
 157                 ND_ICHECK_U(len, <, 4);
 158                 key = GET_BE_U_4(bp);
 159                 bp += 4;
 160                 len -= 4;
 161
 162                 /*
 163                  * OpenBSD shows this as both a 32-bit
 164                  * (decimal) key value and a VSID+FlowID
 165                  * pair, with the VSID in decimal and
 166                  * the FlowID in hex, as key=<Key>|<VSID>+<FlowID>,
 167                  * in case this is NVGRE.
 168                  */
 169                 ND_PRINT(", key=0x%x", key);
 170         }
 171
 172         if (flags & GRE_SP) {
 173                 ND_ICHECK_U(len, <, 4);
 174                 ND_PRINT(", seq %u", GET_BE_U_4(bp));
 175                 bp += 4;
 176                 len -= 4;
 177         }
 178
 179         if (flags & GRE_RP) {
 180                 for (;;) {
 181                         uint16_t af;
 182                         uint8_t sreoff;
 183                         uint8_t srelen;
 184
 185                         ND_ICHECK_U(len, <, 4);
 186                         af = GET_BE_U_2(bp);
 187                         sreoff = GET_U_1(bp + 2);
 188                         srelen = GET_U_1(bp + 3);
 189                         bp += 4;
 190                         len -= 4;
 191
 192                         if (af == 0 && srelen == 0)
 193                                 break;
 194
 195                         if (!gre_sre_print(ndo, af, sreoff, srelen, bp, len))
 196                                 goto invalid;
 197
 198                         ND_ICHECK_U(len, <, srelen);
 199                         bp += srelen;
 200                         len -= srelen;
 201                 }
 202         }
 203
 204         if (ndo->ndo_eflag)
 205                 ND_PRINT(", proto %s (0x%04x)",
 206                          tok2str(ethertype_values,"unknown",prot), prot);
 207
 208         ND_PRINT(", length %u",length);
 209
 210         if (ndo->ndo_vflag < 1)
 211                 ND_PRINT(": "); /* put in a colon as protocol demarc */
 212         else
 213                 ND_PRINT("\n\t"); /* if verbose go multiline */
 214
 215         switch (prot) {
 216         case 0x0000:
 217                 /*
 218                  * 0x0000 is reserved, but Cisco, at least, appears to
 219                  * use it for keep-alives; see, for example,
 220                  * https://www.cisco.com/c/en/us/support/docs/ip/generic-routing-encapsulation-gre/118370-technote-gre-00.html#anc1
 221                  */
 222                 printf("keep-alive");
 223                 break;
 224         case ETHERTYPE_IP:
 225                 ip_print(ndo, bp, len);
 226                 break;
 227         case ETHERTYPE_IPV6:
 228                 ip6_print(ndo, bp, len);
 229                 break;
 230         case ETHERTYPE_MPLS:
 231                 mpls_print(ndo, bp, len);
 232                 break;
 233         case ETHERTYPE_IPX:
 234                 ipx_print(ndo, bp, len);
 235                 break;
 236         case ETHERTYPE_ATALK:
 237                 atalk_print(ndo, bp, len);
 238                 break;
 239         case ETHERTYPE_GRE_ISO:
 240                 isoclns_print(ndo, bp, len);
 241                 break;
 242         case ETHERTYPE_TEB:
 243                 ether_print(ndo, bp, len, ND_BYTES_AVAILABLE_AFTER(bp), NULL, NULL);
 244                 break;
 245         default:
 246                 ND_PRINT("gre-proto-0x%x", prot);
 247         }
 248         return;
 249
 250 invalid:
 251         nd_print_invalid(ndo);
 252 }
 253
 254 static void
 255 gre_print_1(netdissect_options *ndo, const u_char *bp, u_int length)
 256 {
 257         u_int len = length;
 258         uint16_t flags, prot;
 259
 260         ND_ICHECK_U(len, <, 2);
 261         flags = GET_BE_U_2(bp);
 262         len -= 2;
 263         bp += 2;
 264
 265         if (ndo->ndo_vflag)
 266                 ND_PRINT(", Flags [%s]",
 267                          bittok2str(gre_flag_values,"none",flags));
 268
 269         ND_ICHECK_U(len, <, 2);
 270         prot = GET_BE_U_2(bp);
 271         len -= 2;
 272         bp += 2;
 273
 274
 275         if (flags & GRE_KP) {
 276                 uint32_t k;
 277
 278                 ND_ICHECK_U(len, <, 4);
 279                 k = GET_BE_U_4(bp);
 280                 ND_PRINT(", call %u", k & 0xffff);
 281                 len -= 4;
 282                 bp += 4;
 283         }
 284
 285         if (flags & GRE_SP) {
 286                 ND_ICHECK_U(len, <, 4);
 287                 ND_PRINT(", seq %u", GET_BE_U_4(bp));
 288                 bp += 4;
 289                 len -= 4;
 290         }
 291
 292         if (flags & GRE_AP) {
 293                 ND_ICHECK_U(len, <, 4);
 294                 ND_PRINT(", ack %u", GET_BE_U_4(bp));
 295                 bp += 4;
 296                 len -= 4;
 297         }
 298
 299         if ((flags & GRE_SP) == 0)
 300                 ND_PRINT(", no-payload");
 301
 302         if (ndo->ndo_eflag)
 303                 ND_PRINT(", proto %s (0x%04x)",
 304                          tok2str(ethertype_values,"unknown",prot), prot);
 305
 306         ND_PRINT(", length %u",length);
 307
 308         if ((flags & GRE_SP) == 0)
 309                 return;
 310
 311         if (ndo->ndo_vflag < 1)
 312                 ND_PRINT(": "); /* put in a colon as protocol demarc */
 313         else
 314                 ND_PRINT("\n\t"); /* if verbose go multiline */
 315
 316         switch (prot) {
 317         case ETHERTYPE_PPP:
 318                 ppp_print(ndo, bp, len);
 319                 break;
 320         default:
 321                 ND_PRINT("gre-proto-0x%x", prot);
 322                 break;
 323         }
 324         return;
 325
 326 invalid:
 327         nd_print_invalid(ndo);
 328 }
 329
 330 static int
 331 gre_sre_print(netdissect_options *ndo, uint16_t af, uint8_t sreoff,
 332               uint8_t srelen, const u_char *bp, u_int len)
 333 {
 334         int ret;
 335
 336         switch (af) {
 337         case GRESRE_IP:
 338                 ND_PRINT(", (rtaf=ip");
 339                 ret = gre_sre_ip_print(ndo, sreoff, srelen, bp, len);
 340                 ND_PRINT(")");
 341                 break;
 342         case GRESRE_ASN:
 343                 ND_PRINT(", (rtaf=asn");
 344                 ret = gre_sre_asn_print(ndo, sreoff, srelen, bp, len);
 345                 ND_PRINT(")");
 346                 break;
 347         default:
 348                 ND_PRINT(", (rtaf=0x%x)", af);
 349                 ret = 1;
 350         }
 351         return (ret);
 352 }
 353
 354 static int
 355 gre_sre_ip_print(netdissect_options *ndo, uint8_t sreoff, uint8_t srelen,
 356                  const u_char *bp, u_int len)
 357 {
 358         const u_char *up = bp;
 359         char buf[INET_ADDRSTRLEN];
 360
 361         if (sreoff & 3) {
 362                 ND_PRINT(", badoffset=%u", sreoff);
 363                 goto invalid;
 364         }
 365         if (srelen & 3) {
 366                 ND_PRINT(", badlength=%u", srelen);
 367                 goto invalid;
 368         }
 369         if (sreoff >= srelen) {
 370                 ND_PRINT(", badoff/len=%u/%u", sreoff, srelen);
 371                 goto invalid;
 372         }
 373
 374         while (srelen != 0) {
 375                 ND_ICHECK_U(len, <, 4);
 376
 377                 ND_TCHECK_LEN(bp, sizeof(nd_ipv4));
 378                 addrtostr(bp, buf, sizeof(buf));
 379                 ND_PRINT(" %s%s",
 380                          ((bp - up) == sreoff) ? "*" : "", buf);
 381
 382                 bp += 4;
 383                 len -= 4;
 384                 srelen -= 4;
 385         }
 386         return 1;
 387
 388 invalid:
 389         return 0;
 390 }
 391
 392 static int
 393 gre_sre_asn_print(netdissect_options *ndo, uint8_t sreoff, uint8_t srelen,
 394                   const u_char *bp, u_int len)
 395 {
 396         const u_char *up = bp;
 397
 398         if (sreoff & 1) {
 399                 ND_PRINT(", badoffset=%u", sreoff);
 400                 goto invalid;
 401         }
 402         if (srelen & 1) {
 403                 ND_PRINT(", badlength=%u", srelen);
 404                 goto invalid;
 405         }
 406         if (sreoff >= srelen) {
 407                 ND_PRINT(", badoff/len=%u/%u", sreoff, srelen);
 408                 goto invalid;
 409         }
 410
 411         while (srelen != 0) {
 412                 ND_ICHECK_U(len, <, 2);
 413
 414                 ND_PRINT(" %s%x",
 415                          ((bp - up) == sreoff) ? "*" : "", GET_BE_U_2(bp));
 416
 417                 bp += 2;
 418                 len -= 2;
 419                 srelen -= 2;
 420         }
 421         return 1;
 422
 423 invalid:
 424         return 0;
 425 }