2 * Routines for Token-Ring packet disassembly
3 * Gilbert Ramirez <gram@xiexie.org>
5 * $Id: packet-tr.c,v 1.47 2000/10/17 11:05:23 gram Exp $
7 * Ethereal - Network traffic analyzer
8 * By Gerald Combs <gerald@zing.org>
9 * Copyright 1998 Gerald Combs
12 * This program is free software; you can redistribute it and/or
13 * modify it under the terms of the GNU General Public License
14 * as published by the Free Software Foundation; either version 2
15 * of the License, or (at your option) any later version.
17 * This program is distributed in the hope that it will be useful,
18 * but WITHOUT ANY WARRANTY; without even the implied warranty of
19 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
20 * GNU General Public License for more details.
22 * You should have received a copy of the GNU General Public License
23 * along with this program; if not, write to the Free Software
24 * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
31 #ifdef HAVE_SYS_TYPES_H
32 # include <sys/types.h>
38 #include "packet-tr.h"
39 #include "packet-llc.h"
40 #include "packet-trmac.h"
42 static int proto_tr = -1;
43 static int hf_tr_dst = -1;
44 static int hf_tr_src = -1;
45 static int hf_tr_addr = -1;
46 static int hf_tr_sr = -1;
47 static int hf_tr_ac = -1;
48 static int hf_tr_priority = -1;
49 static int hf_tr_frame = -1;
50 static int hf_tr_monitor_cnt = -1;
51 static int hf_tr_priority_reservation = -1;
52 static int hf_tr_fc = -1;
53 static int hf_tr_fc_type = -1;
54 static int hf_tr_fc_pcf = -1;
55 static int hf_tr_rif_bytes = -1;
56 static int hf_tr_broadcast = -1;
57 static int hf_tr_max_frame_size = -1;
58 static int hf_tr_direction = -1;
59 static int hf_tr_rif = -1;
60 static int hf_tr_rif_ring = -1;
61 static int hf_tr_rif_bridge = -1;
63 static gint ett_token_ring = -1;
64 static gint ett_token_ring_ac = -1;
65 static gint ett_token_ring_fc = -1;
67 #define TR_MIN_HEADER_LEN 14
68 #define TR_MAX_HEADER_LEN 32
70 static const true_false_string ac_truth = { "Frame", "Token" };
72 static const value_string pcf_vals[] = {
73 { 0, "Normal buffer" },
74 { 1, "Express buffer" },
78 { 5, "Active Monitor Present" },
79 { 6, "Standby Monitor Present" },
83 static const value_string frame_vals[] = {
90 static const value_string broadcast_vals[] = {
91 { 0 << 5, "Non-broadcast" },
92 { 1 << 5, "Non-broadcast" },
93 { 2 << 5, "Non-broadcast" },
94 { 3 << 5, "Non-broadcast" },
95 { 4 << 5, "All-routes broadcast" },
96 { 5 << 5, "All-routes broadcast" },
97 { 6 << 5, "Single-route broadcast" },
98 { 7 << 5, "Single-route broadcast" },
102 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 (<--)" },
120 * DODGY LINUX HACK DODGY LINUX HACK
121 * Linux 2.0.x always passes frames to the Token Ring driver for transmission with
122 * 18 bytes padding for source routing information. Some drivers copy the first
123 * (18 - srlen) bytes up the frame (18 - srlen) bytes thus removing the padding.
124 * Other drivers just make a copy of the entire frame and then hack about with it
125 * so the frame the sniffer gets is fine (just has extra sr routing).
126 * In the first instance (driver hacking frame in situ) the sniffer gets a garbled
128 * This function trys to detect this and returns the offset of where
129 * the frame really starts.
130 * This only detects frames that we have sent ourselves so if we are packet sniffing
131 * on the machine we are watching this is useful.
132 * Compare offset 0 with offset x+1 for a length of x bytes for all value of x = 1 to 18
133 * if match then Linux driver has done in situ source route compression of the crappy
134 * Linux 2.0.x frame so the beginning of the real frame is x bytes in.
135 * (And this real frame x bytes in looks like a proper TR frame that goes on the wire
136 * with none of the Linux idiosyncrasies).
138 int check_for_old_linux_tvb(tvbuff_t *tvb)
143 /* Restrict our looping to the boundaries of the frame */
144 bytes = tvb_length(tvb);
149 data = tvb_get_ptr(tvb, 0, bytes);
151 for(x = 1; x <= bytes-1 ;x++)
153 if (memcmp(&data[0], &data[x], x) == 0)
161 int check_for_old_linux(const u_char * pd)
166 if (memcmp(&pd[0],&pd[x],x) == 0)
176 add_ring_bridge_pairs(int rcf_len, tvbuff_t*, proto_tree *tree);
179 capture_tr(const u_char *pd, int offset, packet_counts *ld) {
181 int source_routed = 0;
184 guint8 trn_rif_bytes;
185 guint8 actual_rif_bytes;
188 /* The trn_hdr struct, as separate variables */
189 guint8 trn_fc; /* field control field */
190 const guint8 *trn_shost; /* source host */
192 if (!BYTES_ARE_IN_FRAME(offset, TR_MIN_HEADER_LEN)) {
197 if ((x = check_for_old_linux(pd)))
199 /* Actually packet starts x bytes into what we have got but with all
200 source routing compressed
202 /* pd = &pd[x]; */ offset+=x;
206 trn_fc = pd[offset + 1];
207 trn_shost = &pd[offset + 8];
209 frame_type = (trn_fc & 192) >> 6;
211 /* if the high bit on the first byte of src hwaddr is 1, then
212 this packet is source-routed */
213 source_routed = trn_shost[0] & 128;
215 trn_rif_bytes = pd[offset + 14] & 31;
217 /* the Linux 2.0 TR code strips source-route bits in
218 * order to test for SR. This can be removed from most
219 * packets with oltr, but not all. So, I try to figure out
220 * which packets should have been SR here. I'll check to
221 * see if there's a SNAP or IPX field right after
224 if (!source_routed && trn_rif_bytes > 0) {
225 if (pd[offset + 0x0e] != pd[offset + 0x0f]) {
226 first2_sr = pntohs(&pd[offset + 0xe0 + trn_rif_bytes]);
228 (first2_sr == 0xaaaa &&
229 pd[offset + 0x10 + trn_rif_bytes] == 0x03) ||
231 first2_sr == 0xe0e0 ||
232 first2_sr == 0xe0aa ) {
240 actual_rif_bytes = trn_rif_bytes;
244 actual_rif_bytes = 0;
247 /* this is a silly hack for Linux 2.0.x. Read the comment below,
248 in front of the other #ifdef linux. If we're sniffing our own NIC,
249 we get a full RIF, sometimes with garbage */
250 if ((source_routed && trn_rif_bytes == 2 && frame_type == 1) ||
251 (!source_routed && frame_type == 1)) {
252 /* look for SNAP or IPX only */
253 if ( (pd[offset + 0x20] == 0xaa && pd[offset + 0x21] == 0xaa && pd[offset + 0x22] == 03) ||
254 (pd[offset + 0x20] == 0xe0 && pd[offset + 0x21] == 0xe0) ) {
255 actual_rif_bytes = 18;
257 pd[offset + 0x23] == 0 &&
258 pd[offset + 0x24] == 0 &&
259 pd[offset + 0x25] == 0 &&
260 pd[offset + 0x26] == 0x00 &&
261 pd[offset + 0x27] == 0x11) {
263 actual_rif_bytes = 18;
265 /* Linux 2.0.x also requires drivers pass up a fake SNAP and LLC header before th
266 real LLC hdr for all Token Ring frames that arrive with DSAP and SSAP != 0xAA
267 (i.e. for non SNAP frames e.g. for Netware frames)
268 the fake SNAP header has the ETH_P_TR_802_2 ether type (0x0011) and the protocol id
269 bytes as zero frame looks like :-
270 TR Header | Fake LLC | Fake SNAP | Wire LLC | Rest of data */
271 offset += 8; /* Skip fake LLC and SNAP */
275 offset += actual_rif_bytes + TR_MIN_HEADER_LEN;
277 /* The package is either MAC or LLC */
278 switch (frame_type) {
284 capture_llc(pd, offset, ld);
287 /* non-MAC, non-LLC, i.e., "Reserved" */
295 dissect_tr(tvbuff_t *tvb, packet_info *pinfo, proto_tree *tree)
297 proto_tree *tr_tree, *bf_tree;
303 volatile int fixoffset = 0;
304 volatile int source_routed = 0;
305 volatile guint8 trn_rif_bytes;
306 volatile guint8 actual_rif_bytes;
307 volatile guint8 c1_nonsr;
308 volatile guint8 c2_nonsr;
309 volatile guint16 first2_sr;
311 /* I make tr_tvb static because I need to set it before any TRY block.
312 * If tr_tvb were not static, the possibility exists that the value
313 * I give to tr_tvb would be clobbered. */
314 static tvbuff_t *tr_tvb = NULL;
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 CHECK_DISPLAY_AS_DATA(proto_tr, tvb, pinfo, tree);
331 pinfo->current_proto = "Token-Ring";
333 if (check_col(pinfo->fd, COL_PROTOCOL))
334 col_add_str(pinfo->fd, COL_PROTOCOL, "TR");
336 if ((x = check_for_old_linux_tvb((tvbuff_t*) tvb))) {
337 /* Actually packet starts x bytes into what we have got but with all
338 source routing compressed. See comment above */
339 tr_tvb = tvb_new_subset((tvbuff_t*) tvb, x, -1, -1);
346 trn_fc = tvb_get_guint8(tr_tvb, 1);
347 trn_dhost = tvb_get_ptr(tr_tvb, 2, 6);
348 trn_shost = tvb_get_ptr(tr_tvb, 8, 6);
351 memcpy(trn_shost_nonsr, trn_shost, 6);
352 trn_shost_nonsr[0] &= 127;
353 frame_type = (trn_fc & 192) >> 6;
355 if (check_col(pinfo->fd, COL_INFO))
356 col_add_fstr(pinfo->fd, COL_INFO, "Token-Ring %s", fc[frame_type]);
358 /* if the high bit on the first byte of src hwaddr is 1, then
359 this packet is source-routed */
360 source_routed = trn_shost[0] & 128;
362 trn_rif_bytes = tvb_get_guint8(tr_tvb, 14) & 31;
364 /* the Linux 2.0 TR code strips source-route bits in
365 * order to test for SR. This can be removed from most
366 * packets with oltr, but not all. So, I try to figure out
367 * which packets should have been SR here. I'll check to
368 * see if there's a SNAP or IPX field right after
371 if (!source_routed && trn_rif_bytes > 0) {
374 c1_nonsr = tvb_get_guint8(tr_tvb, 14);
375 c2_nonsr = tvb_get_guint8(tr_tvb, 15);
377 if (c1_nonsr != c2_nonsr) {
379 first2_sr = tvb_get_ntohs(tr_tvb, trn_rif_bytes + 0x0e);
381 if ( ( first2_sr == 0xaaaa &&
382 tvb_get_guint8(tr_tvb, trn_rif_bytes + 0x10) == 0x03) ||
384 first2_sr == 0xe0e0 ||
385 first2_sr == 0xe0aa ) {
392 /* We had no information beyond the TR header. Just assume
393 * this is a normal (non-Linux) TR header. */
400 actual_rif_bytes = trn_rif_bytes;
404 actual_rif_bytes = 0;
407 /* this is a silly hack for Linux 2.0.x. Read the comment below,
408 in front of the other #ifdef linux. If we're sniffing our own NIC,
409 we get a full RIF, sometimes with garbage */
411 if ((source_routed && trn_rif_bytes == 2 && frame_type == 1) ||
412 (!source_routed && frame_type == 1)) {
413 /* look for SNAP or IPX only */
415 (tvb_get_ntohs(tr_tvb, 0x20) == 0xaaaa &&
416 tvb_get_guint8(tr_tvb, 0x22) == 0x03)
418 tvb_get_ntohs(tr_tvb, 0x20) == 0xe0e0 ) {
420 actual_rif_bytes = 18;
423 tvb_get_ntohl(tr_tvb, 0x23) == 0 &&
424 tvb_get_guint8(tr_tvb, 0x27) == 0x11) {
426 actual_rif_bytes = 18;
428 /* Linux 2.0.x also requires drivers pass up a fake SNAP and LLC header before th
429 real LLC hdr for all Token Ring frames that arrive with DSAP and SSAP != 0xAA
430 (i.e. for non SNAP frames e.g. for Netware frames)
431 the fake SNAP header has the ETH_P_TR_802_2 ether type (0x0011) and the protocol id
432 bytes as zero frame looks like :-
433 TR Header | Fake LLC | Fake SNAP | Wire LLC | Rest of data */
434 fixoffset += 8; /* Skip fake LLC and SNAP */
439 /* We had no information beyond the TR header. Just assume
440 * this is a normal (non-Linux) TR header. */
446 /* XXX - copy it to some buffer associated with "pi", rather than
447 just making "trn_shost_nonsr" static? */
448 SET_ADDRESS(&pi.dl_src, AT_ETHER, 6, trn_shost_nonsr);
449 SET_ADDRESS(&pi.src, AT_ETHER, 6, trn_shost_nonsr);
450 SET_ADDRESS(&pi.dl_dst, AT_ETHER, 6, trn_dhost);
451 SET_ADDRESS(&pi.dst, AT_ETHER, 6, trn_dhost);
453 /* protocol analysis tree */
455 /* Create Token-Ring Tree */
456 ti = proto_tree_add_item(tree, proto_tr, tr_tvb, 0, TR_MIN_HEADER_LEN + actual_rif_bytes, FALSE);
457 tr_tree = proto_item_add_subtree(ti, ett_token_ring);
459 /* Create the Access Control bitfield tree */
460 trn_ac = tvb_get_guint8(tr_tvb, 0);
461 ti = proto_tree_add_uint(tr_tree, hf_tr_ac, tr_tvb, 0, 1, trn_ac);
462 bf_tree = proto_item_add_subtree(ti, ett_token_ring_ac);
464 proto_tree_add_uint(bf_tree, hf_tr_priority, tr_tvb, 0, 1, trn_ac);
465 proto_tree_add_boolean(bf_tree, hf_tr_frame, tr_tvb, 0, 1, trn_ac);
466 proto_tree_add_uint(bf_tree, hf_tr_monitor_cnt, tr_tvb, 0, 1, trn_ac);
467 proto_tree_add_uint(bf_tree, hf_tr_priority_reservation, tr_tvb, 0, 1, trn_ac);
469 /* Create the Frame Control bitfield tree */
470 ti = proto_tree_add_uint(tr_tree, hf_tr_fc, tr_tvb, 1, 1, trn_fc);
471 bf_tree = proto_item_add_subtree(ti, ett_token_ring_fc);
473 proto_tree_add_uint(bf_tree, hf_tr_fc_type, tr_tvb, 1, 1, trn_fc);
474 proto_tree_add_uint(bf_tree, hf_tr_fc_pcf, tr_tvb, 1, 1, trn_fc);
475 proto_tree_add_ether(tr_tree, hf_tr_dst, tr_tvb, 2, 6, trn_dhost);
476 proto_tree_add_ether(tr_tree, hf_tr_src, tr_tvb, 8, 6, trn_shost);
477 proto_tree_add_ether_hidden(tr_tree, hf_tr_addr, tr_tvb, 2, 6, trn_dhost);
478 proto_tree_add_ether_hidden(tr_tree, hf_tr_addr, tr_tvb, 8, 6, trn_shost);
480 proto_tree_add_boolean(tr_tree, hf_tr_sr, tr_tvb, 8, 1, source_routed);
482 /* non-source-routed version of src addr */
483 proto_tree_add_ether_hidden(tr_tree, hf_tr_src, tr_tvb, 8, 6, trn_shost_nonsr);
487 rcf1 = tvb_get_guint8(tr_tvb, 14);
488 proto_tree_add_uint(tr_tree, hf_tr_rif_bytes, tr_tvb, 14, 1, trn_rif_bytes);
489 proto_tree_add_uint(tr_tree, hf_tr_broadcast, tr_tvb, 14, 1, rcf1 & 224);
492 rcf2 = tvb_get_guint8(tr_tvb, 15);
493 proto_tree_add_uint(tr_tree, hf_tr_max_frame_size, tr_tvb, 15, 1, rcf2 & 112);
494 proto_tree_add_uint(tr_tree, hf_tr_direction, tr_tvb, 15, 1, rcf2 & 128);
496 /* if we have more than 2 bytes of RIF, then we have
498 if (trn_rif_bytes > 2) {
499 add_ring_bridge_pairs(trn_rif_bytes, tr_tvb, tr_tree);
503 /* Linux 2.0.x has a problem in that the 802.5 code creates
504 an emtpy full (18-byte) RIF area. It's up to the tr driver to
505 either fill it in or remove it before sending the bytes out
506 to the wire. If you run tcpdump on a Linux 2.0.x machine running
507 token-ring, tcpdump will capture these 18 filler bytes. They
508 are filled with garbage. The best way to detect this problem is
509 to know the src hwaddr of the machine from which you were running
510 tcpdump. W/o that, however, I'm guessing that DSAP == SSAP if the
511 frame type is LLC. It's very much a hack. */
512 if (actual_rif_bytes > trn_rif_bytes) {
513 proto_tree_add_text(tr_tree, tr_tvb, TR_MIN_HEADER_LEN + trn_rif_bytes, actual_rif_bytes - trn_rif_bytes,
514 "Empty RIF from Linux 2.0.x driver. The sniffing NIC "
515 "is also running a protocol stack.");
518 proto_tree_add_text(tr_tree, tr_tvb, TR_MIN_HEADER_LEN + 18,8,"Linux 2.0.x fake LLC and SNAP header");
522 next_tvb = tvb_new_subset(tr_tvb, TR_MIN_HEADER_LEN + actual_rif_bytes + fixoffset, -1, -1);
524 /* The package is either MAC or LLC */
525 switch (frame_type) {
528 dissect_trmac(next_tvb, pinfo, tree);
531 dissect_llc(next_tvb, pinfo, tree);
534 /* non-MAC, non-LLC, i.e., "Reserved" */
535 dissect_data(next_tvb, pinfo, tree);
540 /* this routine is taken from the Linux net/802/tr.c code, which shows
541 ring-bridge pairs in the /proc/net/tr_rif virtual file. */
543 add_ring_bridge_pairs(int rcf_len, tvbuff_t *tvb, proto_tree *tree)
546 int segment, brdgnmb, unprocessed_rif;
549 #define RIF_OFFSET 16
550 #define RIF_BYTES_TO_PROCESS 30
552 char buffer[3 + (RIF_BYTES_TO_PROCESS / 2) * 6 + 1];
554 /* Only process so many bytes of RIF, as per TR spec, and not overflow
555 * static buffer above */
556 unprocessed_rif = rcf_len - RIF_BYTES_TO_PROCESS;
557 rcf_len = MIN(rcf_len, RIF_BYTES_TO_PROCESS);
559 /* Ignore the 2 RCF bytes, since they don't make up the ring/bride pairs */
562 for(j = 1; j < rcf_len - 1; j += 2) {
564 segment = tvb_get_ntohs(tvb, RIF_OFFSET) >> 4;
565 size = sprintf(buffer, "%03X",segment);
566 proto_tree_add_uint_hidden(tree, hf_tr_rif_ring, tvb, TR_MIN_HEADER_LEN + 2, 2, segment);
569 segment = tvb_get_ntohs(tvb, RIF_OFFSET + 1 + j) >> 4;
570 brdgnmb = tvb_get_guint8(tvb, RIF_OFFSET + j) & 0x0f;
571 size = sprintf(buffer+buff_offset, "-%01X-%03X",brdgnmb,segment);
572 proto_tree_add_uint_hidden(tree, hf_tr_rif_ring, tvb, TR_MIN_HEADER_LEN + 3 + j, 2, segment);
573 proto_tree_add_uint_hidden(tree, hf_tr_rif_bridge, tvb, TR_MIN_HEADER_LEN + 2 + j, 1, brdgnmb);
576 proto_tree_add_string(tree, hf_tr_rif, tvb, TR_MIN_HEADER_LEN + 2, rcf_len, buffer);
578 if (unprocessed_rif > 0) {
579 proto_tree_add_text(tree, tvb, TR_MIN_HEADER_LEN + RIF_BYTES_TO_PROCESS, unprocessed_rif,
580 "Extra RIF bytes beyond spec: %d", unprocessed_rif);
585 proto_register_tr(void)
587 static hf_register_info hf[] = {
589 { "Access Control", "tr.ac", FT_UINT8, BASE_HEX, NULL, 0x0,
593 { "Priority", "tr.priority", FT_UINT8, BASE_DEC, NULL, 0xe0,
597 { "Frame", "tr.frame", FT_BOOLEAN, 8, TFS(&ac_truth), 0x10,
600 { &hf_tr_monitor_cnt,
601 { "Monitor Count", "tr.monitor_cnt", FT_UINT8, BASE_DEC, NULL, 0x08,
604 { &hf_tr_priority_reservation,
605 { "Priority Reservation","tr.priority_reservation", FT_UINT8, BASE_DEC, NULL, 0x07,
609 { "Frame Control", "tr.fc", FT_UINT8, BASE_HEX, NULL, 0x0,
613 { "Frame Type", "tr.frame_type", FT_UINT8, BASE_DEC, VALS(frame_vals), 0xc0,
617 { "Frame PCF", "tr.frame_pcf", FT_UINT8, BASE_DEC, VALS(pcf_vals), 0x0f,
621 { "Destination", "tr.dst", FT_ETHER, BASE_NONE, NULL, 0x0,
622 "Destination Hardware Address" }},
625 { "Source", "tr.src", FT_ETHER, BASE_NONE, NULL, 0x0,
626 "Source Hardware Address" }},
629 { "Source or Destination Address", "tr.addr", FT_ETHER, BASE_NONE, NULL, 0x0,
630 "Source or Destination Hardware Address" }},
633 { "Source Routed", "tr.sr", FT_BOOLEAN, BASE_NONE, NULL, 0x0,
637 { "RIF Bytes", "tr.rif_bytes", FT_UINT8, BASE_DEC, NULL, 0x0,
638 "Number of bytes in Routing Information Fields, including "
639 "the two bytes of Routing Control Field" }},
642 { "Broadcast Type", "tr.broadcast", FT_UINT8, BASE_DEC, VALS(broadcast_vals), 0x0,
643 "Type of Token-Ring Broadcast" }},
645 { &hf_tr_max_frame_size,
646 { "Maximum Frame Size", "tr.max_frame_size", FT_UINT8, BASE_DEC, VALS(max_frame_size_vals),
651 { "Direction", "tr.direction", FT_UINT8, BASE_DEC, VALS(direction_vals), 0x0,
652 "Direction of RIF" }},
655 { "Ring-Bridge Pairs", "tr.rif", FT_STRING, BASE_NONE, NULL, 0x0,
656 "String representing Ring-Bridge Pairs" }},
659 { "RIF Ring", "tr.rif.ring", FT_UINT16, BASE_HEX, NULL, 0x0,
663 { "RIF Bridge", "tr.rif.bridge", FT_UINT8, BASE_HEX, NULL, 0x0,
666 static gint *ett[] = {
672 proto_tr = proto_register_protocol("Token-Ring", "tr");
673 proto_register_field_array(proto_tr, hf, array_length(hf));
674 proto_register_subtree_array(ett, array_length(ett));