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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  * RFC1701 (GRE), RFC1702 (GRE IPv4), and RFC2637 (Enhanced GRE)
  34  */
  35
  36 #ifdef HAVE_CONFIG_H
  37 #include <config.h>
  38 #endif
  39
  40 #include "netdissect-stdinc.h"
  41
  42 #include <string.h>
  43
  44 #include "netdissect.h"
  45 #include "addrtostr.h"
  46 #include "extract.h"
  47 #include "ethertype.h"
  48
  49
  50 #define GRE_CP          0x8000          /* checksum present */
  51 #define GRE_RP          0x4000          /* routing present */
  52 #define GRE_KP          0x2000          /* key present */
  53 #define GRE_SP          0x1000          /* sequence# present */
  54 #define GRE_sP          0x0800          /* source routing */
  55 #define GRE_RECRS       0x0700          /* recursion count */
  56 #define GRE_AP          0x0080          /* acknowledgment# present */
  57
  58 static const struct tok gre_flag_values[] = {
  59     { GRE_CP, "checksum present"},
  60     { GRE_RP, "routing present"},
  61     { GRE_KP, "key present"},
  62     { GRE_SP, "sequence# present"},
  63     { GRE_sP, "source routing present"},
  64     { GRE_RECRS, "recursion count"},
  65     { GRE_AP, "ack present"},
  66     { 0, NULL }
  67 };
  68
  69 #define GRE_VERS_MASK   0x0007          /* protocol version */
  70
  71 /* source route entry types */
  72 #define GRESRE_IP       0x0800          /* IP */
  73 #define GRESRE_ASN      0xfffe          /* ASN */
  74
  75 static void gre_print_0(netdissect_options *, const u_char *, u_int);
  76 static void gre_print_1(netdissect_options *, const u_char *, u_int);
  77 static int gre_sre_print(netdissect_options *, uint16_t, uint8_t, uint8_t, const u_char *, u_int);
  78 static int gre_sre_ip_print(netdissect_options *, uint8_t, uint8_t, const u_char *, u_int);
  79 static int gre_sre_asn_print(netdissect_options *, uint8_t, uint8_t, const u_char *, u_int);
  80
  81 void
  82 gre_print(netdissect_options *ndo, const u_char *bp, u_int length)
  83 {
  84         u_int len = length, vers;
  85
  86         ndo->ndo_protocol = "gre";
  87         ND_TCHECK_2(bp);
  88         if (len < 2)
  89                 goto trunc;
  90         vers = EXTRACT_BE_U_2(bp) & GRE_VERS_MASK;
  91         ND_PRINT("GREv%u",vers);
  92
  93         switch(vers) {
  94         case 0:
  95                 gre_print_0(ndo, bp, len);
  96                 break;
  97         case 1:
  98                 gre_print_1(ndo, bp, len);
  99                 break;
 100         default:
 101                 ND_PRINT(" ERROR: unknown-version");
 102                 break;
 103         }
 104         return;
 105
 106 trunc:
 107         nd_print_trunc(ndo);
 108         return;
 109 }
 110
 111 static void
 112 gre_print_0(netdissect_options *ndo, const u_char *bp, u_int length)
 113 {
 114         u_int len = length;
 115         uint16_t flags, prot;
 116
 117         /* 16 bits ND_TCHECKed in gre_print() */
 118         flags = EXTRACT_BE_U_2(bp);
 119         if (ndo->ndo_vflag)
 120                 ND_PRINT(", Flags [%s]",
 121                          bittok2str(gre_flag_values,"none",flags));
 122
 123         len -= 2;
 124         bp += 2;
 125
 126         ND_TCHECK_2(bp);
 127         if (len < 2)
 128                 goto trunc;
 129         prot = EXTRACT_BE_U_2(bp);
 130         len -= 2;
 131         bp += 2;
 132
 133         if ((flags & GRE_CP) | (flags & GRE_RP)) {
 134                 ND_TCHECK_2(bp);
 135                 if (len < 2)
 136                         goto trunc;
 137                 if (ndo->ndo_vflag)
 138                         ND_PRINT(", sum 0x%x", EXTRACT_BE_U_2(bp));
 139                 bp += 2;
 140                 len -= 2;
 141
 142                 ND_TCHECK_2(bp);
 143                 if (len < 2)
 144                         goto trunc;
 145                 ND_PRINT(", off 0x%x", EXTRACT_BE_U_2(bp));
 146                 bp += 2;
 147                 len -= 2;
 148         }
 149
 150         if (flags & GRE_KP) {
 151                 ND_TCHECK_4(bp);
 152                 if (len < 4)
 153                         goto trunc;
 154                 ND_PRINT(", key=0x%x", EXTRACT_BE_U_4(bp));
 155                 bp += 4;
 156                 len -= 4;
 157         }
 158
 159         if (flags & GRE_SP) {
 160                 ND_TCHECK_4(bp);
 161                 if (len < 4)
 162                         goto trunc;
 163                 ND_PRINT(", seq %u", EXTRACT_BE_U_4(bp));
 164                 bp += 4;
 165                 len -= 4;
 166         }
 167
 168         if (flags & GRE_RP) {
 169                 for (;;) {
 170                         uint16_t af;
 171                         uint8_t sreoff;
 172                         uint8_t srelen;
 173
 174                         ND_TCHECK_4(bp);
 175                         if (len < 4)
 176                                 goto trunc;
 177                         af = EXTRACT_BE_U_2(bp);
 178                         sreoff = EXTRACT_U_1(bp + 2);
 179                         srelen = EXTRACT_U_1(bp + 3);
 180                         bp += 4;
 181                         len -= 4;
 182
 183                         if (af == 0 && srelen == 0)
 184                                 break;
 185
 186                         if (!gre_sre_print(ndo, af, sreoff, srelen, bp, len))
 187                                 goto trunc;
 188
 189                         if (len < srelen)
 190                                 goto trunc;
 191                         bp += srelen;
 192                         len -= srelen;
 193                 }
 194         }
 195
 196         if (ndo->ndo_eflag)
 197                 ND_PRINT(", proto %s (0x%04x)",
 198                          tok2str(ethertype_values,"unknown",prot), prot);
 199
 200         ND_PRINT(", length %u",length);
 201
 202         if (ndo->ndo_vflag < 1)
 203                 ND_PRINT(": "); /* put in a colon as protocol demarc */
 204         else
 205                 ND_PRINT("\n\t"); /* if verbose go multiline */
 206
 207         switch (prot) {
 208         case ETHERTYPE_IP:
 209                 ip_print(ndo, bp, len);
 210                 break;
 211         case ETHERTYPE_IPV6:
 212                 ip6_print(ndo, bp, len);
 213                 break;
 214         case ETHERTYPE_MPLS:
 215                 mpls_print(ndo, bp, len);
 216                 break;
 217         case ETHERTYPE_IPX:
 218                 ipx_print(ndo, bp, len);
 219                 break;
 220         case ETHERTYPE_ATALK:
 221                 atalk_print(ndo, bp, len);
 222                 break;
 223         case ETHERTYPE_GRE_ISO:
 224                 isoclns_print(ndo, bp, len);
 225                 break;
 226         case ETHERTYPE_TEB:
 227                 ether_print(ndo, bp, len, ndo->ndo_snapend - bp, NULL, NULL);
 228                 break;
 229         default:
 230                 ND_PRINT("gre-proto-0x%x", prot);
 231         }
 232         return;
 233
 234 trunc:
 235         nd_print_trunc(ndo);
 236 }
 237
 238 static void
 239 gre_print_1(netdissect_options *ndo, const u_char *bp, u_int length)
 240 {
 241         u_int len = length;
 242         uint16_t flags, prot;
 243
 244         /* 16 bits ND_TCHECKed in gre_print() */
 245         flags = EXTRACT_BE_U_2(bp);
 246         len -= 2;
 247         bp += 2;
 248
 249         if (ndo->ndo_vflag)
 250                 ND_PRINT(", Flags [%s]",
 251                          bittok2str(gre_flag_values,"none",flags));
 252
 253         ND_TCHECK_2(bp);
 254         if (len < 2)
 255                 goto trunc;
 256         prot = EXTRACT_BE_U_2(bp);
 257         len -= 2;
 258         bp += 2;
 259
 260
 261         if (flags & GRE_KP) {
 262                 uint32_t k;
 263
 264                 ND_TCHECK_4(bp);
 265                 if (len < 4)
 266                         goto trunc;
 267                 k = EXTRACT_BE_U_4(bp);
 268                 ND_PRINT(", call %u", k & 0xffff);
 269                 len -= 4;
 270                 bp += 4;
 271         }
 272
 273         if (flags & GRE_SP) {
 274                 ND_TCHECK_4(bp);
 275                 if (len < 4)
 276                         goto trunc;
 277                 ND_PRINT(", seq %u", EXTRACT_BE_U_4(bp));
 278                 bp += 4;
 279                 len -= 4;
 280         }
 281
 282         if (flags & GRE_AP) {
 283                 ND_TCHECK_4(bp);
 284                 if (len < 4)
 285                         goto trunc;
 286                 ND_PRINT(", ack %u", EXTRACT_BE_U_4(bp));
 287                 bp += 4;
 288                 len -= 4;
 289         }
 290
 291         if ((flags & GRE_SP) == 0)
 292                 ND_PRINT(", no-payload");
 293
 294         if (ndo->ndo_eflag)
 295                 ND_PRINT(", proto %s (0x%04x)",
 296                          tok2str(ethertype_values,"unknown",prot), prot);
 297
 298         ND_PRINT(", length %u",length);
 299
 300         if ((flags & GRE_SP) == 0)
 301                 return;
 302
 303         if (ndo->ndo_vflag < 1)
 304                 ND_PRINT(": "); /* put in a colon as protocol demarc */
 305         else
 306                 ND_PRINT("\n\t"); /* if verbose go multiline */
 307
 308         switch (prot) {
 309         case ETHERTYPE_PPP:
 310                 ppp_print(ndo, bp, len);
 311                 break;
 312         default:
 313                 ND_PRINT("gre-proto-0x%x", prot);
 314                 break;
 315         }
 316         return;
 317
 318 trunc:
 319         nd_print_trunc(ndo);
 320 }
 321
 322 static int
 323 gre_sre_print(netdissect_options *ndo, uint16_t af, uint8_t sreoff,
 324               uint8_t srelen, const u_char *bp, u_int len)
 325 {
 326         int ret;
 327
 328         switch (af) {
 329         case GRESRE_IP:
 330                 ND_PRINT(", (rtaf=ip");
 331                 ret = gre_sre_ip_print(ndo, sreoff, srelen, bp, len);
 332                 ND_PRINT(")");
 333                 break;
 334         case GRESRE_ASN:
 335                 ND_PRINT(", (rtaf=asn");
 336                 ret = gre_sre_asn_print(ndo, sreoff, srelen, bp, len);
 337                 ND_PRINT(")");
 338                 break;
 339         default:
 340                 ND_PRINT(", (rtaf=0x%x)", af);
 341                 ret = 1;
 342         }
 343         return (ret);
 344 }
 345
 346 static int
 347 gre_sre_ip_print(netdissect_options *ndo, uint8_t sreoff, uint8_t srelen,
 348                  const u_char *bp, u_int len)
 349 {
 350         const u_char *up = bp;
 351         char buf[INET_ADDRSTRLEN];
 352
 353         if (sreoff & 3) {
 354                 ND_PRINT(", badoffset=%u", sreoff);
 355                 return (1);
 356         }
 357         if (srelen & 3) {
 358                 ND_PRINT(", badlength=%u", srelen);
 359                 return (1);
 360         }
 361         if (sreoff >= srelen) {
 362                 ND_PRINT(", badoff/len=%u/%u", sreoff, srelen);
 363                 return (1);
 364         }
 365
 366         while (srelen != 0) {
 367                 ND_TCHECK_4(bp);
 368                 if (len < 4)
 369                         return (0);
 370
 371                 addrtostr(bp, buf, sizeof(buf));
 372                 ND_PRINT(" %s%s",
 373                          ((bp - up) == sreoff) ? "*" : "", buf);
 374
 375                 bp += 4;
 376                 len -= 4;
 377                 srelen -= 4;
 378         }
 379         return (1);
 380 trunc:
 381         return 0;
 382 }
 383
 384 static int
 385 gre_sre_asn_print(netdissect_options *ndo, uint8_t sreoff, uint8_t srelen,
 386                   const u_char *bp, u_int len)
 387 {
 388         const u_char *up = bp;
 389
 390         if (sreoff & 1) {
 391                 ND_PRINT(", badoffset=%u", sreoff);
 392                 return (1);
 393         }
 394         if (srelen & 1) {
 395                 ND_PRINT(", badlength=%u", srelen);
 396                 return (1);
 397         }
 398         if (sreoff >= srelen) {
 399                 ND_PRINT(", badoff/len=%u/%u", sreoff, srelen);
 400                 return (1);
 401         }
 402
 403         while (srelen != 0) {
 404                 ND_TCHECK_2(bp);
 405                 if (len < 2)
 406                         return (0);
 407
 408                 ND_PRINT(" %s%x",
 409                          ((bp - up) == sreoff) ? "*" : "", EXTRACT_BE_U_2(bp));
 410
 411                 bp += 2;
 412                 len -= 2;
 413                 srelen -= 2;
 414         }
 415         return (1);
 416 trunc:
 417         return 0;
 418 }