packet-llc.c

   1 /* packet-llc.c
   2  * Routines for IEEE 802.2 LLC layer
   3  * Gilbert Ramirez <gram@alumni.rice.edu>
   4  *
   5  * $Id: packet-llc.c,v 1.109 2003/04/18 03:41:39 guy Exp $
   6  *
   7  * Ethereal - Network traffic analyzer
   8  * By Gerald Combs <gerald@ethereal.com>
   9  * Copyright 1998 Gerald Combs
  10  *
  11  * This program is free software; you can redistribute it and/or
  12  * modify it under the terms of the GNU General Public License
  13  * as published by the Free Software Foundation; either version 2
  14  * of the License, or (at your option) any later version.
  15  *
  16  * This program is distributed in the hope that it will be useful,
  17  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  18  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  19  * GNU General Public License for more details.
  20  *
  21  * You should have received a copy of the GNU General Public License
  22  * along with this program; if not, write to the Free Software
  23  * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA  02111-1307, USA.
  24  */
  25
  26 #ifdef HAVE_CONFIG_H
  27 # include "config.h"
  28 #endif
  29
  30 #include <glib.h>
  31 #include <epan/packet.h>
  32 #include "oui.h"
  33 #include "xdlc.h"
  34 #include "etypes.h"
  35 #include "llcsaps.h"
  36 #include "bridged_pids.h"
  37 #include "ppptypes.h"
  38 #include "arcnet_pids.h"
  39 #include "packet-fc.h"
  40 #include "packet-ip.h"
  41 #include "packet-ipx.h"
  42 #include "packet-netbios.h"
  43 #include "packet-vines.h"
  44 #include <epan/sna-utils.h>
  45
  46 #include "packet-llc.h"
  47
  48 #define UDP_PORT_LLC1   12000
  49 #define UDP_PORT_LLC2   12001
  50 #define UDP_PORT_LLC3   12002
  51 #define UDP_PORT_LLC4   12003
  52 #define UDP_PORT_LLC5   12004
  53
  54 static int proto_llc = -1;
  55 static int hf_llc_dsap = -1;
  56 static int hf_llc_ssap = -1;
  57 static int hf_llc_dsap_ig = -1;
  58 static int hf_llc_ssap_cr = -1;
  59 static int hf_llc_ctrl = -1;
  60 static int hf_llc_type = -1;
  61 static int hf_llc_oui = -1;
  62 static int hf_llc_pid = -1;
  63
  64 static gint ett_llc = -1;
  65 static gint ett_llc_ctrl = -1;
  66
  67 static dissector_table_t subdissector_table;
  68 static dissector_table_t cisco_subdissector_table;
  69 static dissector_table_t xid_subdissector_table;
  70
  71 static dissector_handle_t bpdu_handle;
  72 static dissector_handle_t eth_handle;
  73 static dissector_handle_t fddi_handle;
  74 static dissector_handle_t tr_handle;
  75 static dissector_handle_t data_handle;
  76
  77 /*
  78  * Group/Individual bit, in the DSAP.
  79  */
  80 #define DSAP_GI_BIT     0x01
  81
  82 /*
  83  * Command/Response bit, in the SSAP.
  84  *
  85  * The low-order bit of the SSAP apparently determines whether this
  86  * is a request or a response.  (RFC 1390, "Transmission of IP and
  87  * ARP over FDDI Networks", says
  88  *
  89  *      Command frames are identified by having the low order
  90  *      bit of the SSAP address reset to zero.  Response frames
  91  *      have the low order bit of the SSAP address set to one.
  92  *
  93  * and a page I've seen seems to imply that's part of 802.2.)
  94  */
  95 #define SSAP_CR_BIT     0x01
  96
  97 /*
  98  * Mask to extrace the SAP number from the DSAP or the SSAP.
  99  */
 100 #define SAP_MASK        0xFE
 101
 102 /*
 103  * These are for SSAP and DSAP, wth last bit always zero.
 104  * XXX - some DSAPs come in separate "individual" and "group" versions,
 105  * with the last bit 0 and 1, respectively (e.g., LLC Sub-layer Management,
 106  * IBM SNA Path Control, IBM Net Management), but, whilst 0xFE is
 107  * the ISO Network Layer Protocol, 0xFF is the Global LSAP.
 108  */
 109 const value_string sap_vals[] = {
 110         { SAP_NULL,           "NULL LSAP" },
 111         { SAP_LLC_SLMGMT,     "LLC Sub-Layer Management" },
 112         { SAP_SNA_PATHCTRL,   "SNA Path Control" },
 113         { SAP_IP,             "TCP/IP" },
 114         { SAP_SNA1,           "SNA" },
 115         { SAP_SNA2,           "SNA" },
 116         { SAP_PROWAY_NM_INIT, "PROWAY (IEC955) Network Management and Initialization" },
 117         { SAP_TI,             "Texas Instruments" },
 118         { SAP_BPDU,           "Spanning Tree BPDU" },
 119         { SAP_RS511,          "EIA RS-511 Manufacturing Message Service" },
 120         { SAP_X25,            "ISO 8208 (X.25 over 802.2)" },
 121         /*
 122          * XXX - setting the group bit of SAP_X25 make 0x7F; is this just
 123          * a group version of that?
 124          */
 125         { 0x7F,               "ISO 802.2" },
 126         { SAP_XNS,            "XNS" },
 127         { SAP_BACNET,         "BACnet" },
 128         { SAP_NESTAR,         "Nestar" },
 129         { SAP_PROWAY_ASLM,    "PROWAY (IEC955) Active Station List Maintenance" },
 130         { SAP_ARP,            "ARP" },  /* XXX - hand to "dissect_arp()"? */
 131         { SAP_SNAP,           "SNAP" },
 132         { SAP_VINES1,         "Banyan Vines" },
 133         { SAP_VINES2,         "Banyan Vines" },
 134         { SAP_NETWARE,        "NetWare" },
 135         { SAP_NETBIOS,        "NetBIOS" },
 136         { SAP_IBMNM,          "IBM Net Management" },
 137         { SAP_HPEXT,          "HP Extended LLC" },
 138         { SAP_UB,             "Ungermann-Bass" },
 139         { SAP_RPL,            "Remote Program Load" },
 140         { SAP_OSINL,          "ISO Network Layer" },
 141         { SAP_GLOBAL,         "Global LSAP" },
 142         { 0x00,               NULL }
 143 };
 144
 145 /*
 146  * See
 147  *
 148  * http://www.cisco.com/univercd/cc/td/doc/product/lan/trsrb/vlan.htm
 149  *
 150  * for the PIDs for VTP and DRiP that go with an OUI of OUI_CISCO.
 151  */
 152 const value_string oui_vals[] = {
 153         { OUI_ENCAP_ETHER, "Encapsulated Ethernet" },
 154 /*
 155 http://www.cisco.com/univercd/cc/td/doc/product/software/ios113ed/113ed_cr/ibm_r/brprt1/brsrb.htm
 156 */
 157         { OUI_CISCO,       "Cisco" },
 158         { OUI_CISCO_90,    "Cisco IOS 9.0 Compatible" },
 159         { OUI_BRIDGED,     "Frame Relay or ATM bridged frames" },
 160                                 /* RFC 2427, RFC 2684 */
 161         { OUI_ATM_FORUM,   "ATM Forum" },
 162         { OUI_CABLE_BPDU,  "DOCSIS Spanning Tree" }, /* DOCSIS spanning tree BPDU */
 163         { OUI_APPLE_ATALK, "Apple (AppleTalk)" },
 164         { 0,               NULL }
 165 };
 166
 167 void
 168 capture_llc(const guchar *pd, int offset, int len, packet_counts *ld) {
 169
 170         int             is_snap;
 171         guint16         control;
 172         int             llc_header_len;
 173         guint32         oui;
 174         guint16         etype;
 175
 176         if (!BYTES_ARE_IN_FRAME(offset, len, 2)) {
 177                 ld->other++;
 178                 return;
 179         }
 180         is_snap = (pd[offset] == SAP_SNAP) && (pd[offset+1] == SAP_SNAP);
 181         llc_header_len = 2;     /* DSAP + SSAP */
 182
 183         /*
 184          * XXX - the page referred to in the comment above about the
 185          * Command/Response bit also implies that LLC Type 2 always
 186          * uses extended operation, so we don't need to determine
 187          * whether it's basic or extended operation; is that the case?
 188          */
 189         control = get_xdlc_control(pd, offset+2, pd[offset+1] & SSAP_CR_BIT);
 190         llc_header_len += XDLC_CONTROL_LEN(control, TRUE);
 191         if (is_snap)
 192                 llc_header_len += 5;    /* 3 bytes of OUI, 2 bytes of protocol ID */
 193         if (!BYTES_ARE_IN_FRAME(offset, len, llc_header_len)) {
 194                 ld->other++;
 195                 return;
 196         }
 197
 198         if (is_snap) {
 199                 oui = pd[offset+3] << 16 | pd[offset+4] << 8 | pd[offset+5];
 200                 if (XDLC_IS_INFORMATION(control)) {
 201                         etype = pntohs(&pd[offset+6]);
 202                         switch (oui) {
 203
 204                         case OUI_ENCAP_ETHER:
 205                         case OUI_CISCO_90:
 206                         case OUI_APPLE_ATALK:
 207                                 /* No, I have no idea why Apple used
 208                                    one of their own OUIs, rather than
 209                                    OUI_ENCAP_ETHER, and an Ethernet
 210                                    packet type as protocol ID, for
 211                                    AppleTalk data packets - but used
 212                                    OUI_ENCAP_ETHER and an Ethernet
 213                                    packet type for AARP packets. */
 214                                 capture_ethertype(etype, pd, offset+8, len,
 215                                     ld);
 216                                 break;
 217                         case OUI_CISCO:
 218                                 capture_ethertype(etype, pd, offset + 8, len,
 219                                     ld);
 220                                 break;
 221                         default:
 222                                 ld->other++;
 223                                 break;
 224                         }
 225                 }
 226         }
 227         else {
 228                 /* non-SNAP */
 229                 if (XDLC_IS_INFORMATION(control)) {
 230                         switch (pd[offset]) {
 231
 232                         case SAP_IP:
 233                                 capture_ip(pd, offset + llc_header_len, len,
 234                                     ld);
 235                                 break;
 236
 237                         case SAP_NETWARE:
 238                                 capture_ipx(ld);
 239                                 break;
 240
 241                         case SAP_NETBIOS:
 242                                 capture_netbios(ld);
 243                                 break;
 244
 245                         case SAP_VINES1:
 246                         case SAP_VINES2:
 247                                 capture_vines(ld);
 248                                 break;
 249
 250                         default:
 251                                 ld->other++;
 252                                 break;
 253                         }
 254                 }
 255         }
 256 }
 257
 258 static void
 259 dissect_llc(tvbuff_t *tvb, packet_info *pinfo, proto_tree *tree)
 260 {
 261         proto_tree      *llc_tree = NULL;
 262         proto_item      *ti = NULL;
 263         int             is_snap;
 264         guint16         control;
 265         int             llc_header_len;
 266         guint8          dsap, ssap;
 267         tvbuff_t        *next_tvb;
 268
 269         if (check_col(pinfo->cinfo, COL_PROTOCOL)) {
 270                 col_set_str(pinfo->cinfo, COL_PROTOCOL, "LLC");
 271         }
 272         if (check_col(pinfo->cinfo, COL_INFO)) {
 273                 col_clear(pinfo->cinfo, COL_INFO);
 274         }
 275
 276         dsap = tvb_get_guint8(tvb, 0);
 277         if (tree) {
 278                 ti = proto_tree_add_item(tree, proto_llc, tvb, 0, -1, FALSE);
 279                 llc_tree = proto_item_add_subtree(ti, ett_llc);
 280                 proto_tree_add_uint(llc_tree, hf_llc_dsap, tvb, 0,
 281                         1, dsap & SAP_MASK);
 282                 proto_tree_add_boolean(llc_tree, hf_llc_dsap_ig, tvb, 0,
 283                         1, dsap & DSAP_GI_BIT);
 284         } else
 285                 llc_tree = NULL;
 286
 287         ssap = tvb_get_guint8(tvb, 1);
 288         if (tree) {
 289                 proto_tree_add_uint(llc_tree, hf_llc_ssap, tvb, 1,
 290                         1, ssap & SAP_MASK);
 291                 proto_tree_add_boolean(llc_tree, hf_llc_ssap_cr, tvb, 1,
 292                         1, ssap & SSAP_CR_BIT);
 293         } else
 294                 llc_tree = NULL;
 295
 296         is_snap = (dsap == SAP_SNAP) && (ssap == SAP_SNAP);
 297         llc_header_len = 2;     /* DSAP + SSAP */
 298
 299         /*
 300          * XXX - the page referred to in the comment above about the
 301          * Command/Response bit also implies that LLC Type 2 always
 302          * uses extended operation, so we don't need to determine
 303          * whether it's basic or extended operation; is that the case?
 304          */
 305         control = dissect_xdlc_control(tvb, 2, pinfo, llc_tree,
 306                                 hf_llc_ctrl, ett_llc_ctrl,
 307                                 ssap & SSAP_CR_BIT, TRUE);
 308         llc_header_len += XDLC_CONTROL_LEN(control, TRUE);
 309         if (is_snap)
 310                 llc_header_len += 5;    /* 3 bytes of OUI, 2 bytes of protocol ID */
 311
 312         if (tree)
 313                 proto_item_set_len(ti, llc_header_len);
 314
 315         if (is_snap) {
 316                 dissect_snap(tvb, 3, pinfo, tree, llc_tree, control,
 317                     hf_llc_oui, hf_llc_type, hf_llc_pid, 2);
 318         }
 319         else {
 320                 if (check_col(pinfo->cinfo, COL_INFO)) {
 321                         col_append_fstr(pinfo->cinfo, COL_INFO,
 322                             "; DSAP %s %s, SSAP %s %s",
 323                             val_to_str(dsap & SAP_MASK, sap_vals, "%02x"),
 324                             dsap & DSAP_GI_BIT ?
 325                               "Group" : "Individual",
 326                             val_to_str(ssap & SAP_MASK, sap_vals, "%02x"),
 327                             ssap & SSAP_CR_BIT ?
 328                               "Response" : "Command"
 329                         );
 330                 }
 331
 332                 if (tvb_length_remaining(tvb, llc_header_len) > 0) {
 333                         next_tvb = tvb_new_subset(tvb, llc_header_len, -1, -1);
 334                         if (XDLC_IS_INFORMATION(control)) {
 335                                 /*
 336                                  * Non-SNAP I or UI frame.
 337                                  * Try the regular LLC subdissector table
 338                                  * with the DSAP.
 339                                  */
 340                                 if (!dissector_try_port(subdissector_table,
 341                                     dsap, next_tvb, pinfo, tree)) {
 342                                         call_dissector(data_handle, next_tvb,
 343                                             pinfo, tree);
 344                                 }
 345                         } else if ((control & (XDLC_U_MODIFIER_MASK|XDLC_U))
 346                             == (XDLC_XID|XDLC_U)) {
 347                                 /*
 348                                  * Non-SNAP XID frame.
 349                                  * Try the XID LLC subdissector table
 350                                  * with the DSAP.
 351                                  */
 352                                 if (!dissector_try_port(xid_subdissector_table,
 353                                     dsap, next_tvb, pinfo, tree)) {
 354                                         call_dissector(data_handle, next_tvb,
 355                                             pinfo, tree);
 356                                 }
 357                         } else {
 358                                 call_dissector(data_handle, next_tvb, pinfo,
 359                                     tree);
 360                         }
 361                 }
 362         }
 363 }
 364
 365 /*
 366  * Dissect SNAP header; used elsewhere, e.g. in the Frame Relay dissector.
 367  */
 368 void
 369 dissect_snap(tvbuff_t *tvb, int offset, packet_info *pinfo, proto_tree *tree,
 370     proto_tree *snap_tree, int control, int hf_oui, int hf_type, int hf_pid,
 371     int bridge_pad)
 372 {
 373         guint32         oui;
 374         guint16         etype;
 375         tvbuff_t        *next_tvb;
 376
 377         oui =   tvb_get_ntoh24(tvb, offset);
 378         etype = tvb_get_ntohs(tvb, offset+3);
 379
 380         if (check_col(pinfo->cinfo, COL_INFO)) {
 381                 col_append_fstr(pinfo->cinfo, COL_INFO,
 382                     "; SNAP, OUI 0x%06X (%s), PID 0x%04X",
 383                     oui, val_to_str(oui, oui_vals, "Unknown"), etype);
 384         }
 385         if (tree) {
 386                 proto_tree_add_uint(snap_tree, hf_oui, tvb, offset, 3, oui);
 387         }
 388
 389         switch (oui) {
 390
 391         case OUI_ENCAP_ETHER:
 392         case OUI_CISCO_90:
 393         case OUI_APPLE_ATALK:
 394                 /* No, I have no idea why Apple used
 395                    one of their own OUIs, rather than
 396                    OUI_ENCAP_ETHER, and an Ethernet
 397                    packet type as protocol ID, for
 398                    AppleTalk data packets - but used
 399                    OUI_ENCAP_ETHER and an Ethernet
 400                    packet type for AARP packets. */
 401                 if (XDLC_IS_INFORMATION(control)) {
 402                         ethertype(etype, tvb, offset+5,
 403                             pinfo, tree, snap_tree, hf_type, -1);
 404                 } else {
 405                         next_tvb = tvb_new_subset(tvb, offset+5, -1, -1);
 406                         call_dissector(data_handle,next_tvb, pinfo, tree);
 407                 }
 408                 break;
 409
 410         case OUI_BRIDGED:
 411                 /*
 412                  * MAC frames bridged over ATM (RFC 2684) or Frame Relay
 413                  * (RFC 2427).
 414                  *
 415                  * We have to figure out how much padding to put
 416                  * into the frame.  We were handed a "bridge_pad"
 417                  * argument which should be 0 for Frame Relay and
 418                  * 2 for ATM; we add to that the amount of padding
 419                  * common to both bridging types.
 420                  */
 421                 if (tree) {
 422                         proto_tree_add_uint(snap_tree, hf_pid, tvb, offset+3, 2,
 423                             etype);
 424                 }
 425
 426                 switch (etype) {
 427
 428                 case BPID_ETH_WITH_FCS:
 429                 case BPID_ETH_WITHOUT_FCS:
 430                         next_tvb = tvb_new_subset(tvb, offset+5+bridge_pad,
 431                             -1, -1);
 432                         call_dissector(eth_handle, next_tvb, pinfo, tree);
 433                         break;
 434
 435                 case BPID_802_5_WITH_FCS:
 436                 case BPID_802_5_WITHOUT_FCS:
 437                         /*
 438                          * We treat the last padding byte as the Access
 439                          * Control byte, as that's what the Token
 440                          * Ring dissector expects the first byte to
 441                          * be.
 442                          */
 443                         next_tvb = tvb_new_subset(tvb, offset+5+bridge_pad,
 444                             -1, -1);
 445                         call_dissector(tr_handle, next_tvb, pinfo, tree);
 446                         break;
 447
 448                 case BPID_FDDI_WITH_FCS:
 449                 case BPID_FDDI_WITHOUT_FCS:
 450                         next_tvb = tvb_new_subset(tvb, offset+5+1+bridge_pad,
 451                             -1, -1);
 452                         call_dissector(fddi_handle, next_tvb, pinfo, tree);
 453                         break;
 454
 455                 case BPID_BPDU:
 456                         next_tvb = tvb_new_subset(tvb, offset+5, -1, -1);
 457                         call_dissector(bpdu_handle, next_tvb, pinfo, tree);
 458                         break;
 459
 460                 default:
 461                         next_tvb = tvb_new_subset(tvb, offset+5, -1, -1);
 462                         call_dissector(data_handle,next_tvb, pinfo, tree);
 463                         break;
 464                 }
 465                 break;
 466
 467         case OUI_CISCO:
 468                 /* So are all CDP packets LLC packets
 469                    with an OUI of OUI_CISCO and a
 470                    protocol ID of 0x2000, or
 471                    are some of them raw or encapsulated
 472                    Ethernet? */
 473                 if (tree) {
 474                         proto_tree_add_uint(snap_tree, hf_pid, tvb, offset+3, 2,
 475                             etype);
 476                 }
 477                 next_tvb = tvb_new_subset(tvb, offset+5, -1, -1);
 478                 if (XDLC_IS_INFORMATION(control)) {
 479                         /* do lookup with the subdissector table */
 480                         /* for future reference, 0x0102 is Cisco DRIP */
 481                         if (!dissector_try_port(cisco_subdissector_table,
 482                             etype, next_tvb, pinfo, tree))
 483                                 call_dissector(data_handle,next_tvb, pinfo, tree);
 484                 } else
 485                         call_dissector(data_handle,next_tvb, pinfo, tree);
 486                 break;
 487
 488         case OUI_CABLE_BPDU:    /* DOCSIS cable modem spanning tree BPDU */
 489                 if (tree) {
 490                         proto_tree_add_uint(snap_tree, hf_pid, tvb, offset+3, 2,
 491                             etype);
 492                 }
 493                 next_tvb = tvb_new_subset(tvb, offset+5, -1, -1);
 494                 call_dissector(bpdu_handle, next_tvb, pinfo, tree);
 495                 break;
 496
 497         default:
 498                 if (tree) {
 499                         proto_tree_add_uint(snap_tree, hf_pid, tvb, offset+3, 2,
 500                             etype);
 501                 }
 502                 next_tvb = tvb_new_subset(tvb, offset+5, -1, -1);
 503                 call_dissector(data_handle,next_tvb, pinfo, tree);
 504                 break;
 505         }
 506 }
 507
 508 void
 509 proto_register_llc(void)
 510 {
 511         static struct true_false_string ig_bit = { "Group", "Individual" };
 512         static struct true_false_string cr_bit = { "Response", "Command" };
 513
 514         static hf_register_info hf[] = {
 515                 { &hf_llc_dsap,
 516                 { "DSAP",       "llc.dsap", FT_UINT8, BASE_HEX,
 517                         VALS(sap_vals), 0x0, "", HFILL }},
 518
 519                 { &hf_llc_dsap_ig,
 520                 { "IG Bit",     "llc.dsap.ig", FT_BOOLEAN, BASE_HEX,
 521                         &ig_bit, 0x0, "Individual/Group", HFILL }},
 522
 523                 { &hf_llc_ssap,
 524                 { "SSAP", "llc.ssap", FT_UINT8, BASE_HEX,
 525                         VALS(sap_vals), 0x0, "", HFILL }},
 526
 527                 { &hf_llc_ssap_cr,
 528                 { "CR Bit", "llc.ssap.cr", FT_BOOLEAN, BASE_HEX,
 529                         &cr_bit, 0x0, "Command/Response", HFILL }},
 530
 531                 { &hf_llc_ctrl,
 532                 { "Control", "llc.control", FT_UINT16, BASE_HEX,
 533                         NULL, 0x0, "", HFILL }},
 534
 535                 /* registered here but handled in ethertype.c */
 536                 { &hf_llc_type,
 537                 { "Type", "llc.type", FT_UINT16, BASE_HEX,
 538                         VALS(etype_vals), 0x0, "", HFILL }},
 539
 540                 { &hf_llc_oui,
 541                 { "Organization Code",  "llc.oui", FT_UINT24, BASE_HEX,
 542                         VALS(oui_vals), 0x0, "", HFILL }},
 543
 544                 { &hf_llc_pid,
 545                 { "Protocol ID", "llc.pid", FT_UINT16, BASE_HEX,
 546                         NULL, 0x0, "", HFILL }}
 547         };
 548         static gint *ett[] = {
 549                 &ett_llc,
 550                 &ett_llc_ctrl,
 551         };
 552
 553         proto_llc = proto_register_protocol("Logical-Link Control", "LLC", "llc");
 554         proto_register_field_array(proto_llc, hf, array_length(hf));
 555         proto_register_subtree_array(ett, array_length(ett));
 556
 557 /* subdissector code */
 558         subdissector_table = register_dissector_table("llc.dsap",
 559           "LLC SAP", FT_UINT8, BASE_HEX);
 560         cisco_subdissector_table = register_dissector_table("llc.cisco_pid",
 561           "Cisco OUI PID", FT_UINT16, BASE_HEX);
 562         xid_subdissector_table = register_dissector_table("llc.xid_dsap",
 563           "LLC XID SAP", FT_UINT8, BASE_HEX);
 564
 565         register_dissector("llc", dissect_llc, proto_llc);
 566 }
 567
 568 void
 569 proto_reg_handoff_llc(void)
 570 {
 571         dissector_handle_t llc_handle;
 572
 573         /*
 574          * Get handles for the BPDU, Ethernet, FDDI, and Token Ring
 575          * dissectors.
 576          */
 577         bpdu_handle = find_dissector("bpdu");
 578         eth_handle = find_dissector("eth");
 579         fddi_handle = find_dissector("fddi");
 580         tr_handle = find_dissector("tr");
 581         data_handle = find_dissector("data");
 582
 583         llc_handle = find_dissector("llc");
 584         dissector_add("wtap_encap", WTAP_ENCAP_ATM_RFC1483, llc_handle);
 585         /* RFC 2043 */
 586         dissector_add("ppp.protocol", PPP_LLC, llc_handle);
 587         /* RFC 2353 */
 588         dissector_add("udp.port", UDP_PORT_LLC1, llc_handle);
 589         dissector_add("udp.port", UDP_PORT_LLC2, llc_handle);
 590         dissector_add("udp.port", UDP_PORT_LLC3, llc_handle);
 591         dissector_add("udp.port", UDP_PORT_LLC4, llc_handle);
 592         dissector_add("udp.port", UDP_PORT_LLC5, llc_handle);
 593         /* IP-over-FC when we have the full FC frame */
 594         dissector_add("fc.ftype", FC_FTYPE_IP, llc_handle);
 595
 596         /*
 597          * BACNET-over-ARCNET is really BACNET-over-802.2 LLC-over-ARCNET,
 598          * apparently.
 599          */
 600         dissector_add("arcnet.protocol_id", ARCNET_PROTO_BACNET, llc_handle);
 601 }