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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  * 3. All advertising materials mentioning features or use of this software
  16  *    must display the following acknowledgement:
  17  *      This product includes software developed by Jason L. Wright
  18  * 4. The name of the author may not be used to endorse or promote products
  19  *    derived from this software without specific prior written permission.
  20  *
  21  * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
  22  * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
  23  * WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
  24  * DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT,
  25  * INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
  26  * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
  27  * SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
  28  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
  29  * STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
  30  * ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
  31  * POSSIBILITY OF SUCH DAMAGE.
  32  */
  33
  34 /* \summary: Generic Routing Encapsulation (GRE) printer */
  35
  36 /*
  37  * netdissect printer for GRE - Generic Routing Encapsulation
  38  * RFC1701 (GRE), RFC1702 (GRE IPv4), and RFC2637 (Enhanced GRE)
  39  */
  40
  41 #ifdef HAVE_CONFIG_H
  42 #include <config.h>
  43 #endif
  44
  45 #include "netdissect-stdinc.h"
  46
  47 #include <string.h>
  48
  49 #include "netdissect.h"
  50 #include "addrtostr.h"
  51 #include "extract.h"
  52 #include "ethertype.h"
  53
  54 static const char tstr[] = "[|gre]";
  55
  56 #define GRE_CP          0x8000          /* checksum present */
  57 #define GRE_RP          0x4000          /* routing present */
  58 #define GRE_KP          0x2000          /* key present */
  59 #define GRE_SP          0x1000          /* sequence# present */
  60 #define GRE_sP          0x0800          /* source routing */
  61 #define GRE_RECRS       0x0700          /* recursion count */
  62 #define GRE_AP          0x0080          /* acknowledgment# present */
  63
  64 static const struct tok gre_flag_values[] = {
  65     { GRE_CP, "checksum present"},
  66     { GRE_RP, "routing present"},
  67     { GRE_KP, "key present"},
  68     { GRE_SP, "sequence# present"},
  69     { GRE_sP, "source routing present"},
  70     { GRE_RECRS, "recursion count"},
  71     { GRE_AP, "ack present"},
  72     { 0, NULL }
  73 };
  74
  75 #define GRE_VERS_MASK   0x0007          /* protocol version */
  76
  77 /* source route entry types */
  78 #define GRESRE_IP       0x0800          /* IP */
  79 #define GRESRE_ASN      0xfffe          /* ASN */
  80
  81 static void gre_print_0(netdissect_options *, const u_char *, u_int);
  82 static void gre_print_1(netdissect_options *, const u_char *, u_int);
  83 static int gre_sre_print(netdissect_options *, uint16_t, uint8_t, uint8_t, const u_char *, u_int);
  84 static int gre_sre_ip_print(netdissect_options *, uint8_t, uint8_t, const u_char *, u_int);
  85 static int gre_sre_asn_print(netdissect_options *, uint8_t, uint8_t, const u_char *, u_int);
  86
  87 void
  88 gre_print(netdissect_options *ndo, const u_char *bp, u_int length)
  89 {
  90         u_int len = length, vers;
  91
  92         ndo->ndo_protocol = "gre";
  93         ND_TCHECK_2(bp);
  94         if (len < 2)
  95                 goto trunc;
  96         vers = EXTRACT_BE_U_2(bp) & GRE_VERS_MASK;
  97         ND_PRINT("GREv%u",vers);
  98
  99         switch(vers) {
 100         case 0:
 101             gre_print_0(ndo, bp, len);
 102             break;
 103         case 1:
 104             gre_print_1(ndo, bp, len);
 105             break;
 106         default:
 107             ND_PRINT(" ERROR: unknown-version");
 108             break;
 109         }
 110         return;
 111
 112 trunc:
 113         ND_PRINT("%s", tstr);
 114         return;
 115 }
 116
 117 static void
 118 gre_print_0(netdissect_options *ndo, const u_char *bp, u_int length)
 119 {
 120         u_int len = length;
 121         uint16_t flags, prot;
 122
 123         /* 16 bits ND_TCHECKed in gre_print() */
 124         flags = EXTRACT_BE_U_2(bp);
 125         if (ndo->ndo_vflag)
 126             ND_PRINT(", Flags [%s]",
 127                    bittok2str(gre_flag_values,"none",flags));
 128
 129         len -= 2;
 130         bp += 2;
 131
 132         ND_TCHECK_2(bp);
 133         if (len < 2)
 134                 goto trunc;
 135         prot = EXTRACT_BE_U_2(bp);
 136         len -= 2;
 137         bp += 2;
 138
 139         if ((flags & GRE_CP) | (flags & GRE_RP)) {
 140                 ND_TCHECK_2(bp);
 141                 if (len < 2)
 142                         goto trunc;
 143                 if (ndo->ndo_vflag)
 144                         ND_PRINT(", sum 0x%x", EXTRACT_BE_U_2(bp));
 145                 bp += 2;
 146                 len -= 2;
 147
 148                 ND_TCHECK_2(bp);
 149                 if (len < 2)
 150                         goto trunc;
 151                 ND_PRINT(", off 0x%x", EXTRACT_BE_U_2(bp));
 152                 bp += 2;
 153                 len -= 2;
 154         }
 155
 156         if (flags & GRE_KP) {
 157                 ND_TCHECK_4(bp);
 158                 if (len < 4)
 159                         goto trunc;
 160                 ND_PRINT(", key=0x%x", EXTRACT_BE_U_4(bp));
 161                 bp += 4;
 162                 len -= 4;
 163         }
 164
 165         if (flags & GRE_SP) {
 166                 ND_TCHECK_4(bp);
 167                 if (len < 4)
 168                         goto trunc;
 169                 ND_PRINT(", seq %u", EXTRACT_BE_U_4(bp));
 170                 bp += 4;
 171                 len -= 4;
 172         }
 173
 174         if (flags & GRE_RP) {
 175                 for (;;) {
 176                         uint16_t af;
 177                         uint8_t sreoff;
 178                         uint8_t srelen;
 179
 180                         ND_TCHECK_4(bp);
 181                         if (len < 4)
 182                                 goto trunc;
 183                         af = EXTRACT_BE_U_2(bp);
 184                         sreoff = EXTRACT_U_1(bp + 2);
 185                         srelen = EXTRACT_U_1(bp + 3);
 186                         bp += 4;
 187                         len -= 4;
 188
 189                         if (af == 0 && srelen == 0)
 190                                 break;
 191
 192                         if (!gre_sre_print(ndo, af, sreoff, srelen, bp, len))
 193                                 goto trunc;
 194
 195                         if (len < srelen)
 196                                 goto trunc;
 197                         bp += srelen;
 198                         len -= srelen;
 199                 }
 200         }
 201
 202         if (ndo->ndo_eflag)
 203             ND_PRINT(", proto %s (0x%04x)",
 204                    tok2str(ethertype_values,"unknown",prot),
 205                    prot);
 206
 207         ND_PRINT(", length %u",length);
 208
 209         if (ndo->ndo_vflag < 1)
 210             ND_PRINT(": "); /* put in a colon as protocol demarc */
 211         else
 212             ND_PRINT("\n\t"); /* if verbose go multiline */
 213
 214         switch (prot) {
 215         case ETHERTYPE_IP:
 216                 ip_print(ndo, bp, len);
 217                 break;
 218         case ETHERTYPE_IPV6:
 219                 ip6_print(ndo, bp, len);
 220                 break;
 221         case ETHERTYPE_MPLS:
 222                 mpls_print(ndo, bp, len);
 223                 break;
 224         case ETHERTYPE_IPX:
 225                 ipx_print(ndo, bp, len);
 226                 break;
 227         case ETHERTYPE_ATALK:
 228                 atalk_print(ndo, bp, len);
 229                 break;
 230         case ETHERTYPE_GRE_ISO:
 231                 isoclns_print(ndo, bp, len);
 232                 break;
 233         case ETHERTYPE_TEB:
 234                 ether_print(ndo, bp, len, ndo->ndo_snapend - bp, NULL, NULL);
 235                 break;
 236         default:
 237                 ND_PRINT("gre-proto-0x%x", prot);
 238         }
 239         return;
 240
 241 trunc:
 242         ND_PRINT("%s", tstr);
 243 }
 244
 245 static void
 246 gre_print_1(netdissect_options *ndo, const u_char *bp, u_int length)
 247 {
 248         u_int len = length;
 249         uint16_t flags, prot;
 250
 251         /* 16 bits ND_TCHECKed in gre_print() */
 252         flags = EXTRACT_BE_U_2(bp);
 253         len -= 2;
 254         bp += 2;
 255
 256         if (ndo->ndo_vflag)
 257             ND_PRINT(", Flags [%s]",
 258                    bittok2str(gre_flag_values,"none",flags));
 259
 260         ND_TCHECK_2(bp);
 261         if (len < 2)
 262                 goto trunc;
 263         prot = EXTRACT_BE_U_2(bp);
 264         len -= 2;
 265         bp += 2;
 266
 267
 268         if (flags & GRE_KP) {
 269                 uint32_t k;
 270
 271                 ND_TCHECK_4(bp);
 272                 if (len < 4)
 273                         goto trunc;
 274                 k = EXTRACT_BE_U_4(bp);
 275                 ND_PRINT(", call %u", k & 0xffff);
 276                 len -= 4;
 277                 bp += 4;
 278         }
 279
 280         if (flags & GRE_SP) {
 281                 ND_TCHECK_4(bp);
 282                 if (len < 4)
 283                         goto trunc;
 284                 ND_PRINT(", seq %u", EXTRACT_BE_U_4(bp));
 285                 bp += 4;
 286                 len -= 4;
 287         }
 288
 289         if (flags & GRE_AP) {
 290                 ND_TCHECK_4(bp);
 291                 if (len < 4)
 292                         goto trunc;
 293                 ND_PRINT(", ack %u", EXTRACT_BE_U_4(bp));
 294                 bp += 4;
 295                 len -= 4;
 296         }
 297
 298         if ((flags & GRE_SP) == 0)
 299                 ND_PRINT(", no-payload");
 300
 301         if (ndo->ndo_eflag)
 302             ND_PRINT(", proto %s (0x%04x)",
 303                    tok2str(ethertype_values,"unknown",prot),
 304                    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 trunc:
 327         ND_PRINT("%s", tstr);
 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                 return (1);
 364         }
 365         if (srelen & 3) {
 366                 ND_PRINT(", badlength=%u", srelen);
 367                 return (1);
 368         }
 369         if (sreoff >= srelen) {
 370                 ND_PRINT(", badoff/len=%u/%u", sreoff, srelen);
 371                 return (1);
 372         }
 373
 374         while (srelen != 0) {
 375                 if (!ND_TTEST_4(bp))
 376                         return (0);
 377                 if (len < 4)
 378                         return (0);
 379
 380                 addrtostr(bp, buf, sizeof(buf));
 381                 ND_PRINT(" %s%s",
 382                     ((bp - up) == sreoff) ? "*" : "", buf);
 383
 384                 bp += 4;
 385                 len -= 4;
 386                 srelen -= 4;
 387         }
 388         return (1);
 389 }
 390
 391 static int
 392 gre_sre_asn_print(netdissect_options *ndo, uint8_t sreoff, uint8_t srelen,
 393                   const u_char *bp, u_int len)
 394 {
 395         const u_char *up = bp;
 396
 397         if (sreoff & 1) {
 398                 ND_PRINT(", badoffset=%u", sreoff);
 399                 return (1);
 400         }
 401         if (srelen & 1) {
 402                 ND_PRINT(", badlength=%u", srelen);
 403                 return (1);
 404         }
 405         if (sreoff >= srelen) {
 406                 ND_PRINT(", badoff/len=%u/%u", sreoff, srelen);
 407                 return (1);
 408         }
 409
 410         while (srelen != 0) {
 411                 if (!ND_TTEST_2(bp))
 412                         return (0);
 413                 if (len < 2)
 414                         return (0);
 415
 416                 ND_PRINT(" %s%x",
 417                     ((bp - up) == sreoff) ? "*" : "",
 418                     EXTRACT_BE_U_2(bp));
 419
 420                 bp += 2;
 421                 len -= 2;
 422                 srelen -= 2;
 423         }
 424         return (1);
 425 }