epan/dissectors/packet-fddi.c

   1 /* packet-fddi.c
   2  * Routines for FDDI packet disassembly
   3  *
   4  * ANSI Standard X3T9.5/88-139, Rev 4.0
   5  *
   6  * ISO Standards 9314-N (N = 1 for PHY, N = 2 for MAC, N = 6 for SMT, etc.)
   7  *
   8  * Laurent Deniel <laurent.deniel@free.fr>
   9  *
  10  * $Id$
  11  *
  12  * Wireshark - Network traffic analyzer
  13  * By Gerald Combs <gerald@wireshark.org>
  14  * Copyright 1998 Gerald Combs
  15  *
  16  * This program is free software; you can redistribute it and/or
  17  * modify it under the terms of the GNU General Public License
  18  * as published by the Free Software Foundation; either version 2
  19  * of the License, or (at your option) any later version.
  20  *
  21  * This program is distributed in the hope that it will be useful,
  22  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  23  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  24  * GNU General Public License for more details.
  25  *
  26  * You should have received a copy of the GNU General Public License
  27  * along with this program; if not, write to the Free Software
  28  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
  29  */
  30
  31 #include "config.h"
  32
  33 #include <glib.h>
  34
  35 #include <epan/packet.h>
  36 #include <epan/bitswap.h>
  37 #include <epan/prefs.h>
  38 #include "packet-fddi.h"
  39 #include "packet-llc.h"
  40 #include <epan/tap.h>
  41
  42 #include <epan/addr_resolv.h>
  43
  44 static int proto_fddi = -1;
  45 static int hf_fddi_fc = -1;
  46 static int hf_fddi_fc_clf = -1;
  47 static int hf_fddi_fc_prio = -1;
  48 static int hf_fddi_fc_smt_subtype = -1;
  49 static int hf_fddi_fc_mac_subtype = -1;
  50 static int hf_fddi_dst = -1;
  51 static int hf_fddi_src = -1;
  52 static int hf_fddi_addr = -1;
  53
  54 static gint ett_fddi = -1;
  55 static gint ett_fddi_fc = -1;
  56
  57 static int fddi_tap = -1;
  58
  59 static gboolean fddi_padding = FALSE;
  60
  61 #define FDDI_PADDING            ((fddi_padding) ? 3 : 0)
  62
  63 /* FDDI Frame Control values */
  64
  65 #define FDDI_FC_VOID            0x00            /* Void frame */
  66 #define FDDI_FC_NRT             0x80            /* Nonrestricted token */
  67 #define FDDI_FC_RT              0xc0            /* Restricted token */
  68 #define FDDI_FC_MAC             0xc0            /* MAC frame */
  69 #define FDDI_FC_SMT             0x40            /* SMT frame */
  70 #define FDDI_FC_SMT_INFO        0x41            /* SMT Info */
  71 #define FDDI_FC_SMT_NSA         0x4F            /* SMT Next station adrs */
  72 #define FDDI_FC_SMT_MIN         FDDI_FC_SMT_INFO
  73 #define FDDI_FC_SMT_MAX         FDDI_FC_SMT_NSA
  74 #define FDDI_FC_MAC_MIN         0xc1
  75 #define FDDI_FC_MAC_BEACON      0xc2            /* MAC Beacon frame */
  76 #define FDDI_FC_MAC_CLAIM       0xc3            /* MAC Claim frame */
  77 #define FDDI_FC_MAC_MAX         0xcf
  78 #define FDDI_FC_LLC_ASYNC       0x50            /* Async. LLC frame */
  79 #define FDDI_FC_LLC_ASYNC_MIN   FDDI_FC_LLC_ASYNC
  80 #define FDDI_FC_LLC_ASYNC_DEF   0x54
  81 #define FDDI_FC_LLC_ASYNC_MAX   0x5f
  82 #define FDDI_FC_LLC_SYNC        0xd0            /* Sync. LLC frame */
  83 #define FDDI_FC_LLC_SYNC_MIN    FDDI_FC_LLC_SYNC
  84 #define FDDI_FC_LLC_SYNC_MAX    0xd7
  85 #define FDDI_FC_IMP_ASYNC       0x60            /* Implementor Async. */
  86 #define FDDI_FC_IMP_ASYNC_MIN   FDDI_FC_IMP_ASYNC
  87 #define FDDI_FC_IMP_ASYNC_MAX   0x6f
  88 #define FDDI_FC_IMP_SYNC        0xe0            /* Implementor Synch. */
  89
  90 #define FDDI_FC_CLFF            0xF0            /* Class/Length/Format bits */
  91 #define FDDI_FC_ZZZZ            0x0F            /* Control bits */
  92
  93 /*
  94  * Async frame ZZZZ bits:
  95  */
  96 #define FDDI_FC_ASYNC_R         0x08            /* Reserved */
  97 #define FDDI_FC_ASYNC_PRI       0x07            /* Priority */
  98
  99 #define CLFF_BITS(fc)   (((fc) & FDDI_FC_CLFF) >> 4)
 100 #define ZZZZ_BITS(fc)   ((fc) & FDDI_FC_ZZZZ)
 101
 102 static const value_string clf_vals[] = {
 103   { CLFF_BITS(FDDI_FC_VOID),      "Void" },
 104   { CLFF_BITS(FDDI_FC_SMT),       "SMT" },
 105   { CLFF_BITS(FDDI_FC_LLC_ASYNC), "Async LLC" },
 106   { CLFF_BITS(FDDI_FC_IMP_ASYNC), "Implementor Async" },
 107   { CLFF_BITS(FDDI_FC_NRT),       "Nonrestricted Token" },
 108   { CLFF_BITS(FDDI_FC_MAC),       "MAC" },
 109   { CLFF_BITS(FDDI_FC_LLC_SYNC),  "Sync LLC" },
 110   { CLFF_BITS(FDDI_FC_IMP_SYNC),  "Implementor Sync" },
 111   { 0,                            NULL }
 112 };
 113
 114 static const value_string smt_subtype_vals[] = {
 115   { ZZZZ_BITS(FDDI_FC_SMT_INFO), "Info" },
 116   { ZZZZ_BITS(FDDI_FC_SMT_NSA),  "Next Station Address" },
 117   { 0,                           NULL }
 118 };
 119
 120 static const value_string mac_subtype_vals[] = {
 121   { ZZZZ_BITS(FDDI_FC_MAC_BEACON), "Beacon" },
 122   { ZZZZ_BITS(FDDI_FC_MAC_CLAIM),  "Claim" },
 123   { 0,                             NULL }
 124 };
 125
 126 #define FDDI_HEADER_SIZE       13
 127
 128 /* field positions */
 129
 130 #define FDDI_P_FC               0
 131 #define FDDI_P_DHOST            1
 132 #define FDDI_P_SHOST            7
 133
 134 static dissector_handle_t llc_handle;
 135 static dissector_handle_t data_handle;
 136
 137 static void
 138 swap_mac_addr(guint8 *swapped_addr, tvbuff_t *tvb, gint offset)
 139 {
 140   int i;
 141
 142   for (i = 0; i < 6; i++) {
 143     swapped_addr[i] = BIT_SWAP(tvb_get_guint8(tvb, offset+i));
 144   }
 145 }
 146
 147
 148 void
 149 capture_fddi(const guchar *pd, int len, packet_counts *ld)
 150 {
 151   int offset = 0, fc;
 152
 153   if (!BYTES_ARE_IN_FRAME(0, len, FDDI_HEADER_SIZE + FDDI_PADDING)) {
 154     ld->other++;
 155     return;
 156   }
 157   offset = FDDI_PADDING + FDDI_HEADER_SIZE;
 158
 159   fc = (int) pd[FDDI_P_FC+FDDI_PADDING];
 160
 161   switch (fc) {
 162
 163     /* From now, only 802.2 SNAP (Async. LCC frame) is supported */
 164
 165     case FDDI_FC_LLC_ASYNC + 0  :
 166     case FDDI_FC_LLC_ASYNC + 1  :
 167     case FDDI_FC_LLC_ASYNC + 2  :
 168     case FDDI_FC_LLC_ASYNC + 3  :
 169     case FDDI_FC_LLC_ASYNC + 4  :
 170     case FDDI_FC_LLC_ASYNC + 5  :
 171     case FDDI_FC_LLC_ASYNC + 6  :
 172     case FDDI_FC_LLC_ASYNC + 7  :
 173     case FDDI_FC_LLC_ASYNC + 8  :
 174     case FDDI_FC_LLC_ASYNC + 9  :
 175     case FDDI_FC_LLC_ASYNC + 10 :
 176     case FDDI_FC_LLC_ASYNC + 11 :
 177     case FDDI_FC_LLC_ASYNC + 12 :
 178     case FDDI_FC_LLC_ASYNC + 13 :
 179     case FDDI_FC_LLC_ASYNC + 14 :
 180     case FDDI_FC_LLC_ASYNC + 15 :
 181       capture_llc(pd, offset, len, ld);
 182       return;
 183     default :
 184       ld->other++;
 185       return;
 186
 187   } /* fc */
 188
 189 } /* capture_fddi */
 190
 191 static const gchar *
 192 fddifc_to_str(int fc)
 193 {
 194   static gchar strbuf[128+1];
 195
 196   switch (fc) {
 197
 198   case FDDI_FC_VOID:                    /* Void frame */
 199     return "Void frame";
 200
 201   case FDDI_FC_NRT:                     /* Nonrestricted token */
 202     return "Nonrestricted token";
 203
 204   case FDDI_FC_RT:                      /* Restricted token */
 205     return "Restricted token";
 206
 207   case FDDI_FC_SMT_INFO:                /* SMT Info */
 208     return "SMT info";
 209
 210   case FDDI_FC_SMT_NSA:                 /* SMT Next station adrs */
 211     return "SMT Next station address";
 212
 213   case FDDI_FC_MAC_BEACON:              /* MAC Beacon frame */
 214     return "MAC beacon";
 215
 216   case FDDI_FC_MAC_CLAIM:               /* MAC Claim frame */
 217     return "MAC claim token";
 218
 219   default:
 220     switch (fc & FDDI_FC_CLFF) {
 221
 222     case FDDI_FC_MAC:
 223       g_snprintf(strbuf, sizeof(strbuf), "MAC frame, control %x", fc & FDDI_FC_ZZZZ);
 224       return strbuf;
 225
 226     case FDDI_FC_SMT:
 227       g_snprintf(strbuf, sizeof(strbuf), "SMT frame, control %x", fc & FDDI_FC_ZZZZ);
 228       return strbuf;
 229
 230     case FDDI_FC_LLC_ASYNC:
 231       if (fc & FDDI_FC_ASYNC_R)
 232         g_snprintf(strbuf, sizeof(strbuf), "Async LLC frame, control %x", fc & FDDI_FC_ZZZZ);
 233       else
 234         g_snprintf(strbuf, sizeof(strbuf), "Async LLC frame, priority %d",
 235                         fc & FDDI_FC_ASYNC_PRI);
 236       return strbuf;
 237
 238     case FDDI_FC_LLC_SYNC:
 239       if (fc & FDDI_FC_ZZZZ) {
 240         g_snprintf(strbuf, sizeof(strbuf), "Sync LLC frame, control %x", fc & FDDI_FC_ZZZZ);
 241         return strbuf;
 242       } else
 243         return "Sync LLC frame";
 244
 245     case FDDI_FC_IMP_ASYNC:
 246       g_snprintf(strbuf, sizeof(strbuf), "Implementor async frame, control %x",
 247                         fc & FDDI_FC_ZZZZ);
 248       return strbuf;
 249
 250     case FDDI_FC_IMP_SYNC:
 251       g_snprintf(strbuf, sizeof(strbuf), "Implementor sync frame, control %x",
 252                         fc & FDDI_FC_ZZZZ);
 253       return strbuf;
 254
 255     default:
 256       return "Unknown frame type";
 257     }
 258   }
 259 }
 260
 261
 262 static void
 263 dissect_fddi(tvbuff_t *tvb, packet_info *pinfo, proto_tree *tree,
 264              gboolean bitswapped)
 265 {
 266   proto_tree      *fh_tree     = NULL;
 267   proto_item      *ti, *hidden_item;
 268   const gchar     *fc_str;
 269   proto_tree      *fc_tree;
 270   static guchar    src[6], dst[6]; /* has to be static due to SET_ADDRESS */
 271   guchar           src_swapped[6], dst_swapped[6];
 272   tvbuff_t        *next_tvb;
 273   static fddi_hdr  fddihdrs[4];
 274   static int       fddihdr_num = 0;
 275   fddi_hdr        *fddihdr;
 276
 277   fddihdr_num++;
 278   if (fddihdr_num >= 4) {
 279      fddihdr_num = 0;
 280   }
 281   fddihdr = &fddihdrs[fddihdr_num];
 282
 283   col_set_str(pinfo->cinfo, COL_PROTOCOL, "FDDI");
 284
 285   fddihdr->fc = tvb_get_guint8(tvb, FDDI_P_FC + FDDI_PADDING);
 286   fc_str = fddifc_to_str(fddihdr->fc);
 287
 288   col_add_str(pinfo->cinfo, COL_INFO, fc_str);
 289
 290   if (tree) {
 291     ti = proto_tree_add_protocol_format(tree, proto_fddi, tvb, 0, FDDI_HEADER_SIZE+FDDI_PADDING,
 292                                         "Fiber Distributed Data Interface, %s", fc_str);
 293     fh_tree = proto_item_add_subtree(ti, ett_fddi);
 294     ti = proto_tree_add_uint_format_value(fh_tree, hf_fddi_fc, tvb, FDDI_P_FC + FDDI_PADDING, 1, fddihdr->fc,
 295         "0x%02x (%s)", fddihdr->fc, fc_str);
 296     fc_tree = proto_item_add_subtree(ti, ett_fddi_fc);
 297     proto_tree_add_uint(fc_tree, hf_fddi_fc_clf, tvb, FDDI_P_FC + FDDI_PADDING, 1, fddihdr->fc);
 298     switch ((fddihdr->fc) & FDDI_FC_CLFF) {
 299
 300     case FDDI_FC_SMT:
 301       proto_tree_add_uint(fc_tree, hf_fddi_fc_smt_subtype, tvb, FDDI_P_FC + FDDI_PADDING, 1, fddihdr->fc);
 302       break;
 303
 304     case FDDI_FC_MAC:
 305       if (fddihdr->fc != FDDI_FC_RT)
 306         proto_tree_add_uint(fc_tree, hf_fddi_fc_mac_subtype, tvb, FDDI_P_FC + FDDI_PADDING, 1, fddihdr->fc);
 307       break;
 308
 309     case FDDI_FC_LLC_ASYNC:
 310       if (!((fddihdr->fc) & FDDI_FC_ASYNC_R))
 311         proto_tree_add_uint(fc_tree, hf_fddi_fc_prio, tvb, FDDI_P_FC + FDDI_PADDING, 1, fddihdr->fc);
 312       break;
 313     }
 314   }
 315
 316   /* Extract the destination address, possibly bit-swapping it. */
 317   if (bitswapped)
 318     swap_mac_addr(dst, tvb, FDDI_P_DHOST + FDDI_PADDING);
 319   else
 320     tvb_memcpy(tvb, dst, FDDI_P_DHOST + FDDI_PADDING, sizeof(dst));
 321   swap_mac_addr(dst_swapped, tvb, FDDI_P_DHOST + FDDI_PADDING);
 322
 323   /* XXX - copy them to some buffer associated with "pi", rather than
 324      just making "dst" static? */
 325   SET_ADDRESS(&pinfo->dl_dst, AT_ETHER, 6, &dst[0]);
 326   SET_ADDRESS(&pinfo->dst, AT_ETHER, 6, &dst[0]);
 327   SET_ADDRESS(&fddihdr->dst, AT_ETHER, 6, &dst[0]);
 328
 329   if (fh_tree) {
 330     proto_tree_add_ether(fh_tree, hf_fddi_dst, tvb, FDDI_P_DHOST + FDDI_PADDING, 6, dst);
 331     hidden_item = proto_tree_add_ether(fh_tree, hf_fddi_addr, tvb, FDDI_P_DHOST + FDDI_PADDING, 6, dst);
 332     PROTO_ITEM_SET_HIDDEN(hidden_item);
 333
 334     /* hide some bit-swapped mac address fields in the proto_tree, just in case */
 335     hidden_item = proto_tree_add_ether(fh_tree, hf_fddi_dst, tvb, FDDI_P_DHOST + FDDI_PADDING, 6, dst_swapped);
 336     PROTO_ITEM_SET_HIDDEN(hidden_item);
 337     hidden_item = proto_tree_add_ether(fh_tree, hf_fddi_addr, tvb, FDDI_P_DHOST + FDDI_PADDING, 6, dst_swapped);
 338     PROTO_ITEM_SET_HIDDEN(hidden_item);
 339   }
 340
 341   /* Extract the source address, possibly bit-swapping it. */
 342   if (bitswapped)
 343     swap_mac_addr(src, tvb, FDDI_P_SHOST + FDDI_PADDING);
 344   else
 345     tvb_memcpy(tvb, src, FDDI_P_SHOST + FDDI_PADDING, sizeof(src));
 346   swap_mac_addr(src_swapped, tvb, FDDI_P_SHOST + FDDI_PADDING);
 347
 348   /* XXX - copy them to some buffer associated with "pi", rather than
 349      just making "src" static? */
 350   SET_ADDRESS(&pinfo->dl_src, AT_ETHER, 6, &src[0]);
 351   SET_ADDRESS(&pinfo->src, AT_ETHER, 6, &src[0]);
 352   SET_ADDRESS(&fddihdr->src, AT_ETHER, 6, &src[0]);
 353
 354   if (fh_tree) {
 355     proto_tree_add_ether(fh_tree, hf_fddi_src, tvb, FDDI_P_SHOST + FDDI_PADDING, 6, src);
 356     hidden_item = proto_tree_add_ether(fh_tree, hf_fddi_addr, tvb, FDDI_P_SHOST + FDDI_PADDING, 6, src);
 357     PROTO_ITEM_SET_HIDDEN(hidden_item);
 358
 359     /* hide some bit-swapped mac address fields in the proto_tree, just in case */
 360     hidden_item = proto_tree_add_ether(fh_tree, hf_fddi_src, tvb, FDDI_P_SHOST + FDDI_PADDING, 6, src_swapped);
 361     PROTO_ITEM_SET_HIDDEN(hidden_item);
 362     hidden_item = proto_tree_add_ether(fh_tree, hf_fddi_addr, tvb, FDDI_P_SHOST + FDDI_PADDING, 6, src_swapped);
 363     PROTO_ITEM_SET_HIDDEN(hidden_item);
 364   }
 365
 366   next_tvb = tvb_new_subset_remaining(tvb, FDDI_HEADER_SIZE + FDDI_PADDING);
 367
 368
 369   tap_queue_packet(fddi_tap, pinfo, fddihdr);
 370
 371   switch (fddihdr->fc) {
 372
 373     /* From now, only 802.2 SNAP (Async. LCC frame) is supported */
 374
 375     case FDDI_FC_LLC_ASYNC + 0  :
 376     case FDDI_FC_LLC_ASYNC + 1  :
 377     case FDDI_FC_LLC_ASYNC + 2  :
 378     case FDDI_FC_LLC_ASYNC + 3  :
 379     case FDDI_FC_LLC_ASYNC + 4  :
 380     case FDDI_FC_LLC_ASYNC + 5  :
 381     case FDDI_FC_LLC_ASYNC + 6  :
 382     case FDDI_FC_LLC_ASYNC + 7  :
 383     case FDDI_FC_LLC_ASYNC + 8  :
 384     case FDDI_FC_LLC_ASYNC + 9  :
 385     case FDDI_FC_LLC_ASYNC + 10 :
 386     case FDDI_FC_LLC_ASYNC + 11 :
 387     case FDDI_FC_LLC_ASYNC + 12 :
 388     case FDDI_FC_LLC_ASYNC + 13 :
 389     case FDDI_FC_LLC_ASYNC + 14 :
 390     case FDDI_FC_LLC_ASYNC + 15 :
 391       call_dissector(llc_handle, next_tvb, pinfo, tree);
 392       return;
 393
 394     default :
 395       call_dissector(data_handle,next_tvb, pinfo, tree);
 396       return;
 397
 398   } /* fc */
 399 } /* dissect_fddi */
 400
 401
 402 static void
 403 dissect_fddi_bitswapped(tvbuff_t *tvb, packet_info *pinfo, proto_tree *tree)
 404 {
 405   dissect_fddi(tvb, pinfo, tree, TRUE);
 406 }
 407
 408 static void
 409 dissect_fddi_not_bitswapped(tvbuff_t *tvb, packet_info *pinfo, proto_tree *tree)
 410 {
 411   dissect_fddi(tvb, pinfo, tree, FALSE);
 412 }
 413
 414 void
 415 proto_register_fddi(void)
 416 {
 417   static hf_register_info hf[] = {
 418
 419     /*
 420      * XXX - we want this guy to have his own private formatting
 421      * routine, using "fc_to_str()"; if "fc_to_str()" returns
 422      * NULL, just show the hex value, else show the string.
 423      */
 424     { &hf_fddi_fc,
 425       { "Frame Control", "fddi.fc", FT_UINT8, BASE_HEX, NULL, 0x0,
 426         NULL, HFILL }},
 427
 428     { &hf_fddi_fc_clf,
 429       { "Class/Length/Format", "fddi.fc.clf", FT_UINT8, BASE_HEX, VALS(clf_vals), FDDI_FC_CLFF,
 430         NULL, HFILL }},
 431
 432     { &hf_fddi_fc_prio,
 433       { "Priority", "fddi.fc.prio", FT_UINT8, BASE_DEC, NULL, FDDI_FC_ASYNC_PRI,
 434         NULL, HFILL }},
 435
 436     { &hf_fddi_fc_smt_subtype,
 437       { "SMT Subtype", "fddi.fc.smt_subtype", FT_UINT8, BASE_DEC, VALS(smt_subtype_vals), FDDI_FC_ZZZZ,
 438         NULL, HFILL }},
 439
 440     { &hf_fddi_fc_mac_subtype,
 441       { "MAC Subtype", "fddi.fc.mac_subtype", FT_UINT8, BASE_DEC, VALS(mac_subtype_vals), FDDI_FC_ZZZZ,
 442         NULL, HFILL }},
 443
 444     { &hf_fddi_dst,
 445       { "Destination", "fddi.dst", FT_ETHER, BASE_NONE, NULL, 0x0,
 446         "Destination Hardware Address", HFILL }},
 447
 448     { &hf_fddi_src,
 449       { "Source", "fddi.src", FT_ETHER, BASE_NONE, NULL, 0x0,
 450         NULL, HFILL }},
 451
 452     { &hf_fddi_addr,
 453       { "Source or Destination Address", "fddi.addr", FT_ETHER, BASE_NONE, NULL, 0x0,
 454         "Source or Destination Hardware Address", HFILL }},
 455
 456   };
 457   static gint *ett[] = {
 458     &ett_fddi,
 459     &ett_fddi_fc,
 460   };
 461
 462   module_t *fddi_module;
 463
 464   proto_fddi = proto_register_protocol("Fiber Distributed Data Interface",
 465                                        "FDDI", "fddi");
 466   proto_register_field_array(proto_fddi, hf, array_length(hf));
 467   proto_register_subtree_array(ett, array_length(ett));
 468
 469   /*
 470    * Called from various dissectors for encapsulated FDDI frames.
 471    * We assume the MAC addresses in them aren't bitswapped.
 472    */
 473   register_dissector("fddi", dissect_fddi_not_bitswapped, proto_fddi);
 474
 475   fddi_module = prefs_register_protocol(proto_fddi, NULL);
 476   prefs_register_bool_preference(fddi_module, "padding",
 477                                  "Add 3-byte padding to all FDDI packets",
 478                                  "Whether the FDDI dissector should add 3-byte padding to all "
 479                                  "captured FDDI packets (useful with e.g. Tru64 UNIX tcpdump)",
 480                                  &fddi_padding);
 481
 482   fddi_tap = register_tap("fddi");
 483 }
 484
 485 void
 486 proto_reg_handoff_fddi(void)
 487 {
 488   dissector_handle_t fddi_handle, fddi_bitswapped_handle;
 489
 490   /*
 491    * Get a handle for the LLC dissector.
 492    */
 493   llc_handle = find_dissector("llc");
 494   data_handle = find_dissector("data");
 495
 496   fddi_handle = find_dissector("fddi");
 497   dissector_add_uint("wtap_encap", WTAP_ENCAP_FDDI, fddi_handle);
 498   fddi_bitswapped_handle =
 499     create_dissector_handle(dissect_fddi_bitswapped, proto_fddi);
 500   dissector_add_uint("wtap_encap", WTAP_ENCAP_FDDI_BITSWAPPED,
 501                      fddi_bitswapped_handle);
 502 }