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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 = GET_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 }
 109
 110 static void
 111 gre_print_0(netdissect_options *ndo, const u_char *bp, u_int length)
 112 {
 113         u_int len = length;
 114         uint16_t flags, prot;
 115
 116         /* 16 bits ND_TCHECKed in gre_print() */
 117         flags = GET_BE_U_2(bp);
 118         if (ndo->ndo_vflag)
 119                 ND_PRINT(", Flags [%s]",
 120                          bittok2str(gre_flag_values,"none",flags));
 121
 122         len -= 2;
 123         bp += 2;
 124
 125         ND_TCHECK_2(bp);
 126         if (len < 2)
 127                 goto trunc;
 128         prot = GET_BE_U_2(bp);
 129         len -= 2;
 130         bp += 2;
 131
 132         if ((flags & GRE_CP) | (flags & GRE_RP)) {
 133                 ND_TCHECK_2(bp);
 134                 if (len < 2)
 135                         goto trunc;
 136                 if (ndo->ndo_vflag)
 137                         ND_PRINT(", sum 0x%x", GET_BE_U_2(bp));
 138                 bp += 2;
 139                 len -= 2;
 140
 141                 ND_TCHECK_2(bp);
 142                 if (len < 2)
 143                         goto trunc;
 144                 ND_PRINT(", off 0x%x", GET_BE_U_2(bp));
 145                 bp += 2;
 146                 len -= 2;
 147         }
 148
 149         if (flags & GRE_KP) {
 150                 ND_TCHECK_4(bp);
 151                 if (len < 4)
 152                         goto trunc;
 153                 ND_PRINT(", key=0x%x", GET_BE_U_4(bp));
 154                 bp += 4;
 155                 len -= 4;
 156         }
 157
 158         if (flags & GRE_SP) {
 159                 ND_TCHECK_4(bp);
 160                 if (len < 4)
 161                         goto trunc;
 162                 ND_PRINT(", seq %u", GET_BE_U_4(bp));
 163                 bp += 4;
 164                 len -= 4;
 165         }
 166
 167         if (flags & GRE_RP) {
 168                 for (;;) {
 169                         uint16_t af;
 170                         uint8_t sreoff;
 171                         uint8_t srelen;
 172
 173                         ND_TCHECK_4(bp);
 174                         if (len < 4)
 175                                 goto trunc;
 176                         af = GET_BE_U_2(bp);
 177                         sreoff = GET_U_1(bp + 2);
 178                         srelen = GET_U_1(bp + 3);
 179                         bp += 4;
 180                         len -= 4;
 181
 182                         if (af == 0 && srelen == 0)
 183                                 break;
 184
 185                         if (!gre_sre_print(ndo, af, sreoff, srelen, bp, len))
 186                                 goto trunc;
 187
 188                         if (len < srelen)
 189                                 goto trunc;
 190                         bp += srelen;
 191                         len -= srelen;
 192                 }
 193         }
 194
 195         if (ndo->ndo_eflag)
 196                 ND_PRINT(", proto %s (0x%04x)",
 197                          tok2str(ethertype_values,"unknown",prot), prot);
 198
 199         ND_PRINT(", length %u",length);
 200
 201         if (ndo->ndo_vflag < 1)
 202                 ND_PRINT(": "); /* put in a colon as protocol demarc */
 203         else
 204                 ND_PRINT("\n\t"); /* if verbose go multiline */
 205
 206         switch (prot) {
 207         case ETHERTYPE_IP:
 208                 ip_print(ndo, bp, len);
 209                 break;
 210         case ETHERTYPE_IPV6:
 211                 ip6_print(ndo, bp, len);
 212                 break;
 213         case ETHERTYPE_MPLS:
 214                 mpls_print(ndo, bp, len);
 215                 break;
 216         case ETHERTYPE_IPX:
 217                 ipx_print(ndo, bp, len);
 218                 break;
 219         case ETHERTYPE_ATALK:
 220                 atalk_print(ndo, bp, len);
 221                 break;
 222         case ETHERTYPE_GRE_ISO:
 223                 isoclns_print(ndo, bp, len);
 224                 break;
 225         case ETHERTYPE_TEB:
 226                 ether_print(ndo, bp, len, ND_BYTES_AVAILABLE_AFTER(bp), NULL, NULL);
 227                 break;
 228         default:
 229                 ND_PRINT("gre-proto-0x%x", prot);
 230         }
 231         return;
 232
 233 trunc:
 234         nd_print_trunc(ndo);
 235 }
 236
 237 static void
 238 gre_print_1(netdissect_options *ndo, const u_char *bp, u_int length)
 239 {
 240         u_int len = length;
 241         uint16_t flags, prot;
 242
 243         /* 16 bits ND_TCHECKed in gre_print() */
 244         flags = GET_BE_U_2(bp);
 245         len -= 2;
 246         bp += 2;
 247
 248         if (ndo->ndo_vflag)
 249                 ND_PRINT(", Flags [%s]",
 250                          bittok2str(gre_flag_values,"none",flags));
 251
 252         ND_TCHECK_2(bp);
 253         if (len < 2)
 254                 goto trunc;
 255         prot = GET_BE_U_2(bp);
 256         len -= 2;
 257         bp += 2;
 258
 259
 260         if (flags & GRE_KP) {
 261                 uint32_t k;
 262
 263                 ND_TCHECK_4(bp);
 264                 if (len < 4)
 265                         goto trunc;
 266                 k = GET_BE_U_4(bp);
 267                 ND_PRINT(", call %u", k & 0xffff);
 268                 len -= 4;
 269                 bp += 4;
 270         }
 271
 272         if (flags & GRE_SP) {
 273                 ND_TCHECK_4(bp);
 274                 if (len < 4)
 275                         goto trunc;
 276                 ND_PRINT(", seq %u", GET_BE_U_4(bp));
 277                 bp += 4;
 278                 len -= 4;
 279         }
 280
 281         if (flags & GRE_AP) {
 282                 ND_TCHECK_4(bp);
 283                 if (len < 4)
 284                         goto trunc;
 285                 ND_PRINT(", ack %u", GET_BE_U_4(bp));
 286                 bp += 4;
 287                 len -= 4;
 288         }
 289
 290         if ((flags & GRE_SP) == 0)
 291                 ND_PRINT(", no-payload");
 292
 293         if (ndo->ndo_eflag)
 294                 ND_PRINT(", proto %s (0x%04x)",
 295                          tok2str(ethertype_values,"unknown",prot), prot);
 296
 297         ND_PRINT(", length %u",length);
 298
 299         if ((flags & GRE_SP) == 0)
 300                 return;
 301
 302         if (ndo->ndo_vflag < 1)
 303                 ND_PRINT(": "); /* put in a colon as protocol demarc */
 304         else
 305                 ND_PRINT("\n\t"); /* if verbose go multiline */
 306
 307         switch (prot) {
 308         case ETHERTYPE_PPP:
 309                 ppp_print(ndo, bp, len);
 310                 break;
 311         default:
 312                 ND_PRINT("gre-proto-0x%x", prot);
 313                 break;
 314         }
 315         return;
 316
 317 trunc:
 318         nd_print_trunc(ndo);
 319 }
 320
 321 static int
 322 gre_sre_print(netdissect_options *ndo, uint16_t af, uint8_t sreoff,
 323               uint8_t srelen, const u_char *bp, u_int len)
 324 {
 325         int ret;
 326
 327         switch (af) {
 328         case GRESRE_IP:
 329                 ND_PRINT(", (rtaf=ip");
 330                 ret = gre_sre_ip_print(ndo, sreoff, srelen, bp, len);
 331                 ND_PRINT(")");
 332                 break;
 333         case GRESRE_ASN:
 334                 ND_PRINT(", (rtaf=asn");
 335                 ret = gre_sre_asn_print(ndo, sreoff, srelen, bp, len);
 336                 ND_PRINT(")");
 337                 break;
 338         default:
 339                 ND_PRINT(", (rtaf=0x%x)", af);
 340                 ret = 1;
 341         }
 342         return (ret);
 343 }
 344
 345 static int
 346 gre_sre_ip_print(netdissect_options *ndo, uint8_t sreoff, uint8_t srelen,
 347                  const u_char *bp, u_int len)
 348 {
 349         const u_char *up = bp;
 350         char buf[INET_ADDRSTRLEN];
 351
 352         if (sreoff & 3) {
 353                 ND_PRINT(", badoffset=%u", sreoff);
 354                 return (1);
 355         }
 356         if (srelen & 3) {
 357                 ND_PRINT(", badlength=%u", srelen);
 358                 return (1);
 359         }
 360         if (sreoff >= srelen) {
 361                 ND_PRINT(", badoff/len=%u/%u", sreoff, srelen);
 362                 return (1);
 363         }
 364
 365         while (srelen != 0) {
 366                 ND_TCHECK_4(bp);
 367                 if (len < 4)
 368                         return (0);
 369
 370                 addrtostr(bp, buf, sizeof(buf));
 371                 ND_PRINT(" %s%s",
 372                          ((bp - up) == sreoff) ? "*" : "", buf);
 373
 374                 bp += 4;
 375                 len -= 4;
 376                 srelen -= 4;
 377         }
 378         return (1);
 379 trunc:
 380         return 0;
 381 }
 382
 383 static int
 384 gre_sre_asn_print(netdissect_options *ndo, uint8_t sreoff, uint8_t srelen,
 385                   const u_char *bp, u_int len)
 386 {
 387         const u_char *up = bp;
 388
 389         if (sreoff & 1) {
 390                 ND_PRINT(", badoffset=%u", sreoff);
 391                 return (1);
 392         }
 393         if (srelen & 1) {
 394                 ND_PRINT(", badlength=%u", srelen);
 395                 return (1);
 396         }
 397         if (sreoff >= srelen) {
 398                 ND_PRINT(", badoff/len=%u/%u", sreoff, srelen);
 399                 return (1);
 400         }
 401
 402         while (srelen != 0) {
 403                 ND_TCHECK_2(bp);
 404                 if (len < 2)
 405                         return (0);
 406
 407                 ND_PRINT(" %s%x",
 408                          ((bp - up) == sreoff) ? "*" : "", GET_BE_U_2(bp));
 409
 410                 bp += 2;
 411                 len -= 2;
 412                 srelen -= 2;
 413         }
 414         return (1);
 415 trunc:
 416         return 0;
 417 }