2 * Routines for Token-Ring packet disassembly
3 * Gilbert Ramirez <gram@alumni.rice.edu>
5 * $Id: packet-tr.c,v 1.68 2001/12/10 00:25:40 guy Exp $
7 * Ethereal - Network traffic analyzer
8 * By Gerald Combs <gerald@ethereal.com>
9 * Copyright 1998 Gerald Combs
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.
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.
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.
30 #ifdef HAVE_SYS_TYPES_H
31 # include <sys/types.h>
38 #include "packet-tr.h"
39 #include "packet-llc.h"
41 static int proto_tr = -1;
42 static int hf_tr_dst = -1;
43 static int hf_tr_src = -1;
44 static int hf_tr_addr = -1;
45 static int hf_tr_sr = -1;
46 static int hf_tr_ac = -1;
47 static int hf_tr_priority = -1;
48 static int hf_tr_frame = -1;
49 static int hf_tr_monitor_cnt = -1;
50 static int hf_tr_priority_reservation = -1;
51 static int hf_tr_fc = -1;
52 static int hf_tr_fc_type = -1;
53 static int hf_tr_fc_pcf = -1;
54 static int hf_tr_rif_bytes = -1;
55 static int hf_tr_broadcast = -1;
56 static int hf_tr_max_frame_size = -1;
57 static int hf_tr_direction = -1;
58 static int hf_tr_rif = -1;
59 static int hf_tr_rif_ring = -1;
60 static int hf_tr_rif_bridge = -1;
62 static gint ett_token_ring = -1;
63 static gint ett_token_ring_ac = -1;
64 static gint ett_token_ring_fc = -1;
66 #define TR_MIN_HEADER_LEN 14
67 #define TR_MAX_HEADER_LEN 32
69 static const true_false_string ac_truth = { "Frame", "Token" };
71 static const value_string pcf_vals[] = {
72 { 0, "Normal buffer" },
73 { 1, "Express buffer" },
77 { 5, "Active Monitor Present" },
78 { 6, "Standby Monitor Present" },
82 static const value_string frame_vals[] = {
89 static const value_string broadcast_vals[] = {
90 { 0 << 5, "Non-broadcast" },
91 { 1 << 5, "Non-broadcast" },
92 { 2 << 5, "Non-broadcast" },
93 { 3 << 5, "Non-broadcast" },
94 { 4 << 5, "All-routes broadcast" },
95 { 5 << 5, "All-routes broadcast" },
96 { 6 << 5, "Single-route broadcast" },
97 { 7 << 5, "Single-route broadcast" },
101 static const value_string max_frame_size_vals[] = {
113 static const value_string direction_vals[] = {
114 { 0, "From originating station (-->)" },
115 { 128, "To originating station (<--)" },
119 static dissector_handle_t trmac_handle;
120 static dissector_handle_t llc_handle;
121 static dissector_handle_t data_handle;
124 * DODGY LINUX HACK DODGY LINUX HACK
125 * Linux 2.0.x always passes frames to the Token Ring driver for transmission with
126 * 18 bytes padding for source routing information. Some drivers copy the first
127 * (18 - srlen) bytes up the frame (18 - srlen) bytes thus removing the padding.
128 * Other drivers just make a copy of the entire frame and then hack about with it
129 * so the frame the sniffer gets is fine (just has extra sr routing).
130 * In the first instance (driver hacking frame in situ) the sniffer gets a garbled
132 * This function trys to detect this and returns the offset of where
133 * the frame really starts.
134 * This only detects frames that we have sent ourselves so if we are packet sniffing
135 * on the machine we are watching this is useful.
136 * Compare offset 0 with offset x+1 for a length of x bytes for all value of x = 1 to 18
137 * if match then Linux driver has done in situ source route compression of the crappy
138 * Linux 2.0.x frame so the beginning of the real frame is x bytes in.
139 * (And this real frame x bytes in looks like a proper TR frame that goes on the wire
140 * with none of the Linux idiosyncrasies).
142 int check_for_old_linux_tvb(tvbuff_t *tvb)
147 /* Restrict our looping to the boundaries of the frame */
148 bytes = tvb_length(tvb);
153 data = tvb_get_ptr(tvb, 0, bytes);
155 for(x = 1; x <= bytes-1 ;x++)
157 if (memcmp(&data[0], &data[x], x) == 0)
165 int check_for_old_linux(const u_char * pd)
170 if (memcmp(&pd[0],&pd[x],x) == 0)
180 add_ring_bridge_pairs(int rcf_len, tvbuff_t*, proto_tree *tree);
183 capture_tr(const u_char *pd, int offset, int len, packet_counts *ld) {
185 int source_routed = 0;
188 guint8 trn_rif_bytes;
189 guint8 actual_rif_bytes;
192 /* The trn_hdr struct, as separate variables */
193 guint8 trn_fc; /* field control field */
194 const guint8 *trn_shost; /* source host */
196 if (!BYTES_ARE_IN_FRAME(offset, len, TR_MIN_HEADER_LEN)) {
201 if ((x = check_for_old_linux(pd)))
203 /* Actually packet starts x bytes into what we have got but with all
204 source routing compressed
206 /* pd = &pd[x]; */ offset+=x;
210 trn_fc = pd[offset + 1];
211 trn_shost = &pd[offset + 8];
213 frame_type = (trn_fc & 192) >> 6;
215 /* if the high bit on the first byte of src hwaddr is 1, then
216 this packet is source-routed */
217 source_routed = trn_shost[0] & 128;
219 trn_rif_bytes = pd[offset + 14] & 31;
221 /* the Linux 2.0 TR code strips source-route bits in
222 * order to test for SR. This can be removed from most
223 * packets with oltr, but not all. So, I try to figure out
224 * which packets should have been SR here. I'll check to
225 * see if there's a SNAP or IPX field right after
228 if (!source_routed && trn_rif_bytes > 0) {
229 if (pd[offset + 0x0e] != pd[offset + 0x0f]) {
230 first2_sr = pntohs(&pd[offset + 0xe0 + trn_rif_bytes]);
232 (first2_sr == 0xaaaa &&
233 pd[offset + 0x10 + trn_rif_bytes] == 0x03) ||
235 first2_sr == 0xe0e0 ||
236 first2_sr == 0xe0aa ) {
244 actual_rif_bytes = trn_rif_bytes;
248 actual_rif_bytes = 0;
251 /* this is a silly hack for Linux 2.0.x. Read the comment below,
252 in front of the other #ifdef linux. If we're sniffing our own NIC,
253 we get a full RIF, sometimes with garbage */
254 if ((source_routed && trn_rif_bytes == 2 && frame_type == 1) ||
255 (!source_routed && frame_type == 1)) {
256 /* look for SNAP or IPX only */
257 if ( (pd[offset + 0x20] == 0xaa && pd[offset + 0x21] == 0xaa && pd[offset + 0x22] == 03) ||
258 (pd[offset + 0x20] == 0xe0 && pd[offset + 0x21] == 0xe0) ) {
259 actual_rif_bytes = 18;
261 pd[offset + 0x23] == 0 &&
262 pd[offset + 0x24] == 0 &&
263 pd[offset + 0x25] == 0 &&
264 pd[offset + 0x26] == 0x00 &&
265 pd[offset + 0x27] == 0x11) {
267 actual_rif_bytes = 18;
269 /* Linux 2.0.x also requires drivers pass up a fake SNAP and LLC header before th
270 real LLC hdr for all Token Ring frames that arrive with DSAP and SSAP != 0xAA
271 (i.e. for non SNAP frames e.g. for Netware frames)
272 the fake SNAP header has the ETH_P_TR_802_2 ether type (0x0011) and the protocol id
273 bytes as zero frame looks like :-
274 TR Header | Fake LLC | Fake SNAP | Wire LLC | Rest of data */
275 offset += 8; /* Skip fake LLC and SNAP */
279 offset += actual_rif_bytes + TR_MIN_HEADER_LEN;
281 /* The package is either MAC or LLC */
282 switch (frame_type) {
288 capture_llc(pd, offset, len, ld);
291 /* non-MAC, non-LLC, i.e., "Reserved" */
299 dissect_tr(tvbuff_t *tvb, packet_info *pinfo, proto_tree *tree)
301 proto_tree *tr_tree, *bf_tree;
307 volatile int fixoffset = 0;
308 volatile int source_routed = 0;
309 volatile guint8 trn_rif_bytes;
310 volatile guint8 actual_rif_bytes;
311 volatile guint8 c1_nonsr;
312 volatile guint8 c2_nonsr;
313 volatile guint16 first2_sr;
314 tvbuff_t *volatile tr_tvb;
316 /* The trn_hdr struct, as separate variables */
317 guint8 trn_ac; /* access control field */
318 guint8 trn_fc; /* field control field */
319 const guint8 *trn_dhost; /* destination host */
320 const guint8 *trn_shost; /* source host */
322 /* non-source-routed version of source addr */
323 static guint8 trn_shost_nonsr[6];
326 /* Token-Ring Strings */
327 char *fc[] = { "MAC", "LLC", "Reserved", "Unknown" };
329 if (check_col(pinfo->cinfo, COL_PROTOCOL))
330 col_set_str(pinfo->cinfo, COL_PROTOCOL, "TR");
332 if ((x = check_for_old_linux_tvb((tvbuff_t*) tvb))) {
333 /* Actually packet starts x bytes into what we have got but with all
334 source routing compressed. See comment above */
335 tr_tvb = tvb_new_subset((tvbuff_t*) tvb, x, -1, -1);
342 trn_fc = tvb_get_guint8(tr_tvb, 1);
343 trn_dhost = tvb_get_ptr(tr_tvb, 2, 6);
344 trn_shost = tvb_get_ptr(tr_tvb, 8, 6);
347 memcpy(trn_shost_nonsr, trn_shost, 6);
348 trn_shost_nonsr[0] &= 127;
349 frame_type = (trn_fc & 192) >> 6;
351 if (check_col(pinfo->cinfo, COL_INFO))
352 col_add_fstr(pinfo->cinfo, COL_INFO, "Token-Ring %s", fc[frame_type]);
354 /* if the high bit on the first byte of src hwaddr is 1, then
355 this packet is source-routed */
356 source_routed = trn_shost[0] & 128;
358 trn_rif_bytes = tvb_get_guint8(tr_tvb, 14) & 31;
360 /* the Linux 2.0 TR code strips source-route bits in
361 * order to test for SR. This can be removed from most
362 * packets with oltr, but not all. So, I try to figure out
363 * which packets should have been SR here. I'll check to
364 * see if there's a SNAP or IPX field right after
367 if (frame_type == 1 && !source_routed && trn_rif_bytes > 0) {
370 c1_nonsr = tvb_get_guint8(tr_tvb, 14);
371 c2_nonsr = tvb_get_guint8(tr_tvb, 15);
373 if (c1_nonsr != c2_nonsr) {
375 first2_sr = tvb_get_ntohs(tr_tvb, trn_rif_bytes + 0x0e);
377 if ( ( first2_sr == 0xaaaa &&
378 tvb_get_guint8(tr_tvb, trn_rif_bytes + 0x10) == 0x03) ||
380 first2_sr == 0xe0e0 ||
381 first2_sr == 0xe0aa ) {
388 /* We had no information beyond the TR header. Just assume
389 * this is a normal (non-Linux) TR header. */
396 actual_rif_bytes = trn_rif_bytes;
400 actual_rif_bytes = 0;
403 /* this is a silly hack for Linux 2.0.x. Read the comment below,
404 in front of the other #ifdef linux. If we're sniffing our own NIC,
405 we get a full RIF, sometimes with garbage */
407 if (frame_type == 1 && ( (source_routed && trn_rif_bytes == 2) ||
409 /* look for SNAP or IPX only */
411 (tvb_get_ntohs(tr_tvb, 0x20) == 0xaaaa &&
412 tvb_get_guint8(tr_tvb, 0x22) == 0x03)
414 tvb_get_ntohs(tr_tvb, 0x20) == 0xe0e0 ) {
416 actual_rif_bytes = 18;
419 tvb_get_ntohl(tr_tvb, 0x23) == 0 &&
420 tvb_get_guint8(tr_tvb, 0x27) == 0x11) {
422 actual_rif_bytes = 18;
424 /* Linux 2.0.x also requires drivers pass up a fake SNAP and LLC header before th
425 real LLC hdr for all Token Ring frames that arrive with DSAP and SSAP != 0xAA
426 (i.e. for non SNAP frames e.g. for Netware frames)
427 the fake SNAP header has the ETH_P_TR_802_2 ether type (0x0011) and the protocol id
428 bytes as zero frame looks like :-
429 TR Header | Fake LLC | Fake SNAP | Wire LLC | Rest of data */
430 fixoffset += 8; /* Skip fake LLC and SNAP */
435 /* We had no information beyond the TR header. Just assume
436 * this is a normal (non-Linux) TR header. */
442 /* XXX - copy it to some buffer associated with "*pinfo", rather than
443 just making "trn_shost_nonsr" static? */
444 SET_ADDRESS(&pinfo->dl_src, AT_ETHER, 6, trn_shost_nonsr);
445 SET_ADDRESS(&pinfo->src, AT_ETHER, 6, trn_shost_nonsr);
446 SET_ADDRESS(&pinfo->dl_dst, AT_ETHER, 6, trn_dhost);
447 SET_ADDRESS(&pinfo->dst, AT_ETHER, 6, trn_dhost);
449 /* protocol analysis tree */
451 /* Create Token-Ring Tree */
452 ti = proto_tree_add_item(tree, proto_tr, tr_tvb, 0, TR_MIN_HEADER_LEN + actual_rif_bytes, FALSE);
453 tr_tree = proto_item_add_subtree(ti, ett_token_ring);
455 /* Create the Access Control bitfield tree */
456 trn_ac = tvb_get_guint8(tr_tvb, 0);
457 ti = proto_tree_add_uint(tr_tree, hf_tr_ac, tr_tvb, 0, 1, trn_ac);
458 bf_tree = proto_item_add_subtree(ti, ett_token_ring_ac);
460 proto_tree_add_uint(bf_tree, hf_tr_priority, tr_tvb, 0, 1, trn_ac);
461 proto_tree_add_boolean(bf_tree, hf_tr_frame, tr_tvb, 0, 1, trn_ac);
462 proto_tree_add_uint(bf_tree, hf_tr_monitor_cnt, tr_tvb, 0, 1, trn_ac);
463 proto_tree_add_uint(bf_tree, hf_tr_priority_reservation, tr_tvb, 0, 1, trn_ac);
465 /* Create the Frame Control bitfield tree */
466 ti = proto_tree_add_uint(tr_tree, hf_tr_fc, tr_tvb, 1, 1, trn_fc);
467 bf_tree = proto_item_add_subtree(ti, ett_token_ring_fc);
469 proto_tree_add_uint(bf_tree, hf_tr_fc_type, tr_tvb, 1, 1, trn_fc);
470 proto_tree_add_uint(bf_tree, hf_tr_fc_pcf, tr_tvb, 1, 1, trn_fc);
471 proto_tree_add_ether(tr_tree, hf_tr_dst, tr_tvb, 2, 6, trn_dhost);
472 proto_tree_add_ether(tr_tree, hf_tr_src, tr_tvb, 8, 6, trn_shost);
473 proto_tree_add_ether_hidden(tr_tree, hf_tr_addr, tr_tvb, 2, 6, trn_dhost);
474 proto_tree_add_ether_hidden(tr_tree, hf_tr_addr, tr_tvb, 8, 6, trn_shost);
476 proto_tree_add_boolean(tr_tree, hf_tr_sr, tr_tvb, 8, 1, source_routed);
478 /* non-source-routed version of src addr */
479 proto_tree_add_ether_hidden(tr_tree, hf_tr_src, tr_tvb, 8, 6, trn_shost_nonsr);
483 rcf1 = tvb_get_guint8(tr_tvb, 14);
484 proto_tree_add_uint(tr_tree, hf_tr_rif_bytes, tr_tvb, 14, 1, trn_rif_bytes);
485 proto_tree_add_uint(tr_tree, hf_tr_broadcast, tr_tvb, 14, 1, rcf1 & 224);
488 rcf2 = tvb_get_guint8(tr_tvb, 15);
489 proto_tree_add_uint(tr_tree, hf_tr_max_frame_size, tr_tvb, 15, 1, rcf2 & 112);
490 proto_tree_add_uint(tr_tree, hf_tr_direction, tr_tvb, 15, 1, rcf2 & 128);
492 /* if we have more than 2 bytes of RIF, then we have
494 if (trn_rif_bytes > 2) {
495 add_ring_bridge_pairs(trn_rif_bytes, tr_tvb, tr_tree);
499 /* Linux 2.0.x has a problem in that the 802.5 code creates
500 an emtpy full (18-byte) RIF area. It's up to the tr driver to
501 either fill it in or remove it before sending the bytes out
502 to the wire. If you run tcpdump on a Linux 2.0.x machine running
503 token-ring, tcpdump will capture these 18 filler bytes. They
504 are filled with garbage. The best way to detect this problem is
505 to know the src hwaddr of the machine from which you were running
506 tcpdump. W/o that, however, I'm guessing that DSAP == SSAP if the
507 frame type is LLC. It's very much a hack. */
508 if (actual_rif_bytes > trn_rif_bytes) {
509 proto_tree_add_text(tr_tree, tr_tvb, TR_MIN_HEADER_LEN + trn_rif_bytes, actual_rif_bytes - trn_rif_bytes,
510 "Empty RIF from Linux 2.0.x driver. The sniffing NIC "
511 "is also running a protocol stack.");
514 proto_tree_add_text(tr_tree, tr_tvb, TR_MIN_HEADER_LEN + 18,8,"Linux 2.0.x fake LLC and SNAP header");
518 next_tvb = tvb_new_subset(tr_tvb, TR_MIN_HEADER_LEN + actual_rif_bytes + fixoffset, -1, -1);
520 /* The package is either MAC or LLC */
521 switch (frame_type) {
524 call_dissector(trmac_handle, next_tvb, pinfo, tree);
527 call_dissector(llc_handle, next_tvb, pinfo, tree);
530 /* non-MAC, non-LLC, i.e., "Reserved" */
531 call_dissector(data_handle,next_tvb, pinfo, tree);
536 /* this routine is taken from the Linux net/802/tr.c code, which shows
537 ring-bridge pairs in the /proc/net/tr_rif virtual file. */
539 add_ring_bridge_pairs(int rcf_len, tvbuff_t *tvb, proto_tree *tree)
542 int segment, brdgnmb, unprocessed_rif;
545 #define RIF_OFFSET 16
546 #define RIF_BYTES_TO_PROCESS 30
548 char buffer[3 + (RIF_BYTES_TO_PROCESS / 2) * 6 + 1];
550 /* Only process so many bytes of RIF, as per TR spec, and not overflow
551 * static buffer above */
552 unprocessed_rif = rcf_len - RIF_BYTES_TO_PROCESS;
553 rcf_len = MIN(rcf_len, RIF_BYTES_TO_PROCESS);
555 /* Ignore the 2 RCF bytes, since they don't make up the ring/bride pairs */
558 for(j = 1; j < rcf_len - 1; j += 2) {
560 segment = tvb_get_ntohs(tvb, RIF_OFFSET) >> 4;
561 size = sprintf(buffer, "%03X",segment);
562 proto_tree_add_uint_hidden(tree, hf_tr_rif_ring, tvb, TR_MIN_HEADER_LEN + 2, 2, segment);
565 segment = tvb_get_ntohs(tvb, RIF_OFFSET + 1 + j) >> 4;
566 brdgnmb = tvb_get_guint8(tvb, RIF_OFFSET + j) & 0x0f;
567 size = sprintf(buffer+buff_offset, "-%01X-%03X",brdgnmb,segment);
568 proto_tree_add_uint_hidden(tree, hf_tr_rif_ring, tvb, TR_MIN_HEADER_LEN + 3 + j, 2, segment);
569 proto_tree_add_uint_hidden(tree, hf_tr_rif_bridge, tvb, TR_MIN_HEADER_LEN + 2 + j, 1, brdgnmb);
572 proto_tree_add_string(tree, hf_tr_rif, tvb, TR_MIN_HEADER_LEN + 2, rcf_len, buffer);
574 if (unprocessed_rif > 0) {
575 proto_tree_add_text(tree, tvb, TR_MIN_HEADER_LEN + RIF_BYTES_TO_PROCESS, unprocessed_rif,
576 "Extra RIF bytes beyond spec: %d", unprocessed_rif);
581 proto_register_tr(void)
583 static hf_register_info hf[] = {
585 { "Access Control", "tr.ac", FT_UINT8, BASE_HEX, NULL, 0x0,
589 { "Priority", "tr.priority", FT_UINT8, BASE_DEC, NULL, 0xe0,
593 { "Frame", "tr.frame", FT_BOOLEAN, 8, TFS(&ac_truth), 0x10,
596 { &hf_tr_monitor_cnt,
597 { "Monitor Count", "tr.monitor_cnt", FT_UINT8, BASE_DEC, NULL, 0x08,
600 { &hf_tr_priority_reservation,
601 { "Priority Reservation","tr.priority_reservation", FT_UINT8, BASE_DEC, NULL, 0x07,
605 { "Frame Control", "tr.fc", FT_UINT8, BASE_HEX, NULL, 0x0,
609 { "Frame Type", "tr.frame_type", FT_UINT8, BASE_DEC, VALS(frame_vals), 0xc0,
613 { "Frame PCF", "tr.frame_pcf", FT_UINT8, BASE_DEC, VALS(pcf_vals), 0x0f,
617 { "Destination", "tr.dst", FT_ETHER, BASE_NONE, NULL, 0x0,
618 "Destination Hardware Address", HFILL }},
621 { "Source", "tr.src", FT_ETHER, BASE_NONE, NULL, 0x0,
622 "Source Hardware Address", HFILL }},
625 { "Source or Destination Address", "tr.addr", FT_ETHER, BASE_NONE, NULL, 0x0,
626 "Source or Destination Hardware Address", HFILL }},
629 { "Source Routed", "tr.sr", FT_BOOLEAN, BASE_NONE, NULL, 0x0,
630 "Source Routed", HFILL }},
633 { "RIF Bytes", "tr.rif_bytes", FT_UINT8, BASE_DEC, NULL, 0x0,
634 "Number of bytes in Routing Information Fields, including "
635 "the two bytes of Routing Control Field", HFILL }},
638 { "Broadcast Type", "tr.broadcast", FT_UINT8, BASE_DEC, VALS(broadcast_vals), 0x0,
639 "Type of Token-Ring Broadcast", HFILL }},
641 { &hf_tr_max_frame_size,
642 { "Maximum Frame Size", "tr.max_frame_size", FT_UINT8, BASE_DEC, VALS(max_frame_size_vals),
647 { "Direction", "tr.direction", FT_UINT8, BASE_DEC, VALS(direction_vals), 0x0,
648 "Direction of RIF", HFILL }},
651 { "Ring-Bridge Pairs", "tr.rif", FT_STRING, BASE_NONE, NULL, 0x0,
652 "String representing Ring-Bridge Pairs", HFILL }},
655 { "RIF Ring", "tr.rif.ring", FT_UINT16, BASE_HEX, NULL, 0x0,
659 { "RIF Bridge", "tr.rif.bridge", FT_UINT8, BASE_HEX, NULL, 0x0,
662 static gint *ett[] = {
668 proto_tr = proto_register_protocol("Token-Ring", "Token-Ring", "tr");
669 proto_register_field_array(proto_tr, hf, array_length(hf));
670 proto_register_subtree_array(ett, array_length(ett));
671 register_dissector("tr", dissect_tr, proto_tr);
675 proto_reg_handoff_tr(void)
677 dissector_handle_t tr_handle;
680 * Get handles for the TR MAC and LLC dissectors.
682 trmac_handle = find_dissector("trmac");
683 llc_handle = find_dissector("llc");
684 data_handle = find_dissector("data");
686 tr_handle = find_dissector("tr");
687 dissector_add("wtap_encap", WTAP_ENCAP_TOKEN_RING, tr_handle);