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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_AP          0x0080          /* acknowledgment# present */
  56
  57 static const struct tok gre_flag_values[] = {
  58     { GRE_CP, "checksum present"},
  59     { GRE_RP, "routing present"},
  60     { GRE_KP, "key present"},
  61     { GRE_SP, "sequence# present"},
  62     { GRE_sP, "source routing present"},
  63     { GRE_AP, "ack present"},
  64     { 0, NULL }
  65 };
  66
  67 #define GRE_RECRS_MASK  0x0700          /* recursion count */
  68 #define GRE_VERS_MASK   0x0007          /* protocol version */
  69
  70 /* source route entry types */
  71 #define GRESRE_IP       0x0800          /* IP */
  72 #define GRESRE_ASN      0xfffe          /* ASN */
  73
  74 static void gre_print_0(netdissect_options *, const u_char *, u_int);
  75 static void gre_print_1(netdissect_options *, const u_char *, u_int);
  76 static int gre_sre_print(netdissect_options *, uint16_t, uint8_t, uint8_t, const u_char *, u_int);
  77 static int gre_sre_ip_print(netdissect_options *, uint8_t, uint8_t, const u_char *, u_int);
  78 static int gre_sre_asn_print(netdissect_options *, uint8_t, uint8_t, const u_char *, u_int);
  79
  80 void
  81 gre_print(netdissect_options *ndo, const u_char *bp, u_int length)
  82 {
  83         u_int len = length, vers;
  84
  85         ndo->ndo_protocol = "gre";
  86         ND_TCHECK_2(bp);
  87         if (len < 2)
  88                 goto trunc;
  89         vers = GET_BE_U_2(bp) & GRE_VERS_MASK;
  90         ND_PRINT("GREv%u",vers);
  91
  92         switch(vers) {
  93         case 0:
  94                 gre_print_0(ndo, bp, len);
  95                 break;
  96         case 1:
  97                 gre_print_1(ndo, bp, len);
  98                 break;
  99         default:
 100                 ND_PRINT(" ERROR: unknown-version");
 101                 break;
 102         }
 103         return;
 104
 105 trunc:
 106         nd_print_trunc(ndo);
 107 }
 108
 109 static void
 110 gre_print_0(netdissect_options *ndo, const u_char *bp, u_int length)
 111 {
 112         u_int len = length;
 113         uint16_t flags, prot;
 114
 115         /* 16 bits ND_TCHECKed in gre_print() */
 116         flags = GET_BE_U_2(bp);
 117         if (ndo->ndo_vflag)
 118                 ND_PRINT(", Flags [%s]",
 119                          bittok2str(gre_flag_values,"none",flags));
 120
 121         len -= 2;
 122         bp += 2;
 123
 124         ND_TCHECK_2(bp);
 125         if (len < 2)
 126                 goto trunc;
 127         prot = GET_BE_U_2(bp);
 128         len -= 2;
 129         bp += 2;
 130
 131         if ((flags & GRE_CP) | (flags & GRE_RP)) {
 132                 ND_TCHECK_2(bp);
 133                 if (len < 2)
 134                         goto trunc;
 135                 if (ndo->ndo_vflag)
 136                         ND_PRINT(", sum 0x%x", GET_BE_U_2(bp));
 137                 bp += 2;
 138                 len -= 2;
 139
 140                 ND_TCHECK_2(bp);
 141                 if (len < 2)
 142                         goto trunc;
 143                 ND_PRINT(", off 0x%x", GET_BE_U_2(bp));
 144                 bp += 2;
 145                 len -= 2;
 146         }
 147
 148         if (flags & GRE_KP) {
 149                 ND_TCHECK_4(bp);
 150                 if (len < 4)
 151                         goto trunc;
 152                 ND_PRINT(", key=0x%x", GET_BE_U_4(bp));
 153                 bp += 4;
 154                 len -= 4;
 155         }
 156
 157         if (flags & GRE_SP) {
 158                 ND_TCHECK_4(bp);
 159                 if (len < 4)
 160                         goto trunc;
 161                 ND_PRINT(", seq %u", GET_BE_U_4(bp));
 162                 bp += 4;
 163                 len -= 4;
 164         }
 165
 166         if (flags & GRE_RP) {
 167                 for (;;) {
 168                         uint16_t af;
 169                         uint8_t sreoff;
 170                         uint8_t srelen;
 171
 172                         ND_TCHECK_4(bp);
 173                         if (len < 4)
 174                                 goto trunc;
 175                         af = GET_BE_U_2(bp);
 176                         sreoff = GET_U_1(bp + 2);
 177                         srelen = GET_U_1(bp + 3);
 178                         bp += 4;
 179                         len -= 4;
 180
 181                         if (af == 0 && srelen == 0)
 182                                 break;
 183
 184                         if (!gre_sre_print(ndo, af, sreoff, srelen, bp, len))
 185                                 goto trunc;
 186
 187                         if (len < srelen)
 188                                 goto trunc;
 189                         bp += srelen;
 190                         len -= srelen;
 191                 }
 192         }
 193
 194         if (ndo->ndo_eflag)
 195                 ND_PRINT(", proto %s (0x%04x)",
 196                          tok2str(ethertype_values,"unknown",prot), prot);
 197
 198         ND_PRINT(", length %u",length);
 199
 200         if (ndo->ndo_vflag < 1)
 201                 ND_PRINT(": "); /* put in a colon as protocol demarc */
 202         else
 203                 ND_PRINT("\n\t"); /* if verbose go multiline */
 204
 205         switch (prot) {
 206         case ETHERTYPE_IP:
 207                 ip_print(ndo, bp, len);
 208                 break;
 209         case ETHERTYPE_IPV6:
 210                 ip6_print(ndo, bp, len);
 211                 break;
 212         case ETHERTYPE_MPLS:
 213                 mpls_print(ndo, bp, len);
 214                 break;
 215         case ETHERTYPE_IPX:
 216                 ipx_print(ndo, bp, len);
 217                 break;
 218         case ETHERTYPE_ATALK:
 219                 atalk_print(ndo, bp, len);
 220                 break;
 221         case ETHERTYPE_GRE_ISO:
 222                 isoclns_print(ndo, bp, len);
 223                 break;
 224         case ETHERTYPE_TEB:
 225                 ether_print(ndo, bp, len, ND_BYTES_AVAILABLE_AFTER(bp), NULL, NULL);
 226                 break;
 227         default:
 228                 ND_PRINT("gre-proto-0x%x", prot);
 229         }
 230         return;
 231
 232 trunc:
 233         nd_print_trunc(ndo);
 234 }
 235
 236 static void
 237 gre_print_1(netdissect_options *ndo, const u_char *bp, u_int length)
 238 {
 239         u_int len = length;
 240         uint16_t flags, prot;
 241
 242         /* 16 bits ND_TCHECKed in gre_print() */
 243         flags = GET_BE_U_2(bp);
 244         len -= 2;
 245         bp += 2;
 246
 247         if (ndo->ndo_vflag)
 248                 ND_PRINT(", Flags [%s]",
 249                          bittok2str(gre_flag_values,"none",flags));
 250
 251         ND_TCHECK_2(bp);
 252         if (len < 2)
 253                 goto trunc;
 254         prot = GET_BE_U_2(bp);
 255         len -= 2;
 256         bp += 2;
 257
 258
 259         if (flags & GRE_KP) {
 260                 uint32_t k;
 261
 262                 ND_TCHECK_4(bp);
 263                 if (len < 4)
 264                         goto trunc;
 265                 k = GET_BE_U_4(bp);
 266                 ND_PRINT(", call %u", k & 0xffff);
 267                 len -= 4;
 268                 bp += 4;
 269         }
 270
 271         if (flags & GRE_SP) {
 272                 ND_TCHECK_4(bp);
 273                 if (len < 4)
 274                         goto trunc;
 275                 ND_PRINT(", seq %u", GET_BE_U_4(bp));
 276                 bp += 4;
 277                 len -= 4;
 278         }
 279
 280         if (flags & GRE_AP) {
 281                 ND_TCHECK_4(bp);
 282                 if (len < 4)
 283                         goto trunc;
 284                 ND_PRINT(", ack %u", GET_BE_U_4(bp));
 285                 bp += 4;
 286                 len -= 4;
 287         }
 288
 289         if ((flags & GRE_SP) == 0)
 290                 ND_PRINT(", no-payload");
 291
 292         if (ndo->ndo_eflag)
 293                 ND_PRINT(", proto %s (0x%04x)",
 294                          tok2str(ethertype_values,"unknown",prot), prot);
 295
 296         ND_PRINT(", length %u",length);
 297
 298         if ((flags & GRE_SP) == 0)
 299                 return;
 300
 301         if (ndo->ndo_vflag < 1)
 302                 ND_PRINT(": "); /* put in a colon as protocol demarc */
 303         else
 304                 ND_PRINT("\n\t"); /* if verbose go multiline */
 305
 306         switch (prot) {
 307         case ETHERTYPE_PPP:
 308                 ppp_print(ndo, bp, len);
 309                 break;
 310         default:
 311                 ND_PRINT("gre-proto-0x%x", prot);
 312                 break;
 313         }
 314         return;
 315
 316 trunc:
 317         nd_print_trunc(ndo);
 318 }
 319
 320 static int
 321 gre_sre_print(netdissect_options *ndo, uint16_t af, uint8_t sreoff,
 322               uint8_t srelen, const u_char *bp, u_int len)
 323 {
 324         int ret;
 325
 326         switch (af) {
 327         case GRESRE_IP:
 328                 ND_PRINT(", (rtaf=ip");
 329                 ret = gre_sre_ip_print(ndo, sreoff, srelen, bp, len);
 330                 ND_PRINT(")");
 331                 break;
 332         case GRESRE_ASN:
 333                 ND_PRINT(", (rtaf=asn");
 334                 ret = gre_sre_asn_print(ndo, sreoff, srelen, bp, len);
 335                 ND_PRINT(")");
 336                 break;
 337         default:
 338                 ND_PRINT(", (rtaf=0x%x)", af);
 339                 ret = 1;
 340         }
 341         return (ret);
 342 }
 343
 344 static int
 345 gre_sre_ip_print(netdissect_options *ndo, uint8_t sreoff, uint8_t srelen,
 346                  const u_char *bp, u_int len)
 347 {
 348         const u_char *up = bp;
 349         char buf[INET_ADDRSTRLEN];
 350
 351         if (sreoff & 3) {
 352                 ND_PRINT(", badoffset=%u", sreoff);
 353                 return (1);
 354         }
 355         if (srelen & 3) {
 356                 ND_PRINT(", badlength=%u", srelen);
 357                 return (1);
 358         }
 359         if (sreoff >= srelen) {
 360                 ND_PRINT(", badoff/len=%u/%u", sreoff, srelen);
 361                 return (1);
 362         }
 363
 364         while (srelen != 0) {
 365                 ND_TCHECK_4(bp);
 366                 if (len < 4)
 367                         return (0);
 368
 369                 addrtostr(bp, buf, sizeof(buf));
 370                 ND_PRINT(" %s%s",
 371                          ((bp - up) == sreoff) ? "*" : "", buf);
 372
 373                 bp += 4;
 374                 len -= 4;
 375                 srelen -= 4;
 376         }
 377         return (1);
 378 trunc:
 379         return 0;
 380 }
 381
 382 static int
 383 gre_sre_asn_print(netdissect_options *ndo, uint8_t sreoff, uint8_t srelen,
 384                   const u_char *bp, u_int len)
 385 {
 386         const u_char *up = bp;
 387
 388         if (sreoff & 1) {
 389                 ND_PRINT(", badoffset=%u", sreoff);
 390                 return (1);
 391         }
 392         if (srelen & 1) {
 393                 ND_PRINT(", badlength=%u", srelen);
 394                 return (1);
 395         }
 396         if (sreoff >= srelen) {
 397                 ND_PRINT(", badoff/len=%u/%u", sreoff, srelen);
 398                 return (1);
 399         }
 400
 401         while (srelen != 0) {
 402                 ND_TCHECK_2(bp);
 403                 if (len < 2)
 404                         return (0);
 405
 406                 ND_PRINT(" %s%x",
 407                          ((bp - up) == sreoff) ? "*" : "", GET_BE_U_2(bp));
 408
 409                 bp += 2;
 410                 len -= 2;
 411                 srelen -= 2;
 412         }
 413         return (1);
 414 trunc:
 415         return 0;
 416 }