2 * Routines for Token-Ring packet disassembly
3 * Gilbert Ramirez <gram@xiexie.org>
5 * $Id: packet-tr.c,v 1.54 2001/01/03 10:34:41 guy 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>
39 #include "packet-tr.h"
40 #include "packet-llc.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 (<--)" },
119 static dissector_handle_t trmac_handle;
120 static dissector_handle_t llc_handle;
123 * DODGY LINUX HACK DODGY LINUX HACK
124 * Linux 2.0.x always passes frames to the Token Ring driver for transmission with
125 * 18 bytes padding for source routing information. Some drivers copy the first
126 * (18 - srlen) bytes up the frame (18 - srlen) bytes thus removing the padding.
127 * Other drivers just make a copy of the entire frame and then hack about with it
128 * so the frame the sniffer gets is fine (just has extra sr routing).
129 * In the first instance (driver hacking frame in situ) the sniffer gets a garbled
131 * This function trys to detect this and returns the offset of where
132 * the frame really starts.
133 * This only detects frames that we have sent ourselves so if we are packet sniffing
134 * on the machine we are watching this is useful.
135 * Compare offset 0 with offset x+1 for a length of x bytes for all value of x = 1 to 18
136 * if match then Linux driver has done in situ source route compression of the crappy
137 * Linux 2.0.x frame so the beginning of the real frame is x bytes in.
138 * (And this real frame x bytes in looks like a proper TR frame that goes on the wire
139 * with none of the Linux idiosyncrasies).
141 int check_for_old_linux_tvb(tvbuff_t *tvb)
146 /* Restrict our looping to the boundaries of the frame */
147 bytes = tvb_length(tvb);
152 data = tvb_get_ptr(tvb, 0, bytes);
154 for(x = 1; x <= bytes-1 ;x++)
156 if (memcmp(&data[0], &data[x], x) == 0)
164 int check_for_old_linux(const u_char * pd)
169 if (memcmp(&pd[0],&pd[x],x) == 0)
179 add_ring_bridge_pairs(int rcf_len, tvbuff_t*, proto_tree *tree);
182 capture_tr(const u_char *pd, int offset, packet_counts *ld) {
184 int source_routed = 0;
187 guint8 trn_rif_bytes;
188 guint8 actual_rif_bytes;
191 /* The trn_hdr struct, as separate variables */
192 guint8 trn_fc; /* field control field */
193 const guint8 *trn_shost; /* source host */
195 if (!BYTES_ARE_IN_FRAME(offset, TR_MIN_HEADER_LEN)) {
200 if ((x = check_for_old_linux(pd)))
202 /* Actually packet starts x bytes into what we have got but with all
203 source routing compressed
205 /* pd = &pd[x]; */ offset+=x;
209 trn_fc = pd[offset + 1];
210 trn_shost = &pd[offset + 8];
212 frame_type = (trn_fc & 192) >> 6;
214 /* if the high bit on the first byte of src hwaddr is 1, then
215 this packet is source-routed */
216 source_routed = trn_shost[0] & 128;
218 trn_rif_bytes = pd[offset + 14] & 31;
220 /* the Linux 2.0 TR code strips source-route bits in
221 * order to test for SR. This can be removed from most
222 * packets with oltr, but not all. So, I try to figure out
223 * which packets should have been SR here. I'll check to
224 * see if there's a SNAP or IPX field right after
227 if (!source_routed && trn_rif_bytes > 0) {
228 if (pd[offset + 0x0e] != pd[offset + 0x0f]) {
229 first2_sr = pntohs(&pd[offset + 0xe0 + trn_rif_bytes]);
231 (first2_sr == 0xaaaa &&
232 pd[offset + 0x10 + trn_rif_bytes] == 0x03) ||
234 first2_sr == 0xe0e0 ||
235 first2_sr == 0xe0aa ) {
243 actual_rif_bytes = trn_rif_bytes;
247 actual_rif_bytes = 0;
250 /* this is a silly hack for Linux 2.0.x. Read the comment below,
251 in front of the other #ifdef linux. If we're sniffing our own NIC,
252 we get a full RIF, sometimes with garbage */
253 if ((source_routed && trn_rif_bytes == 2 && frame_type == 1) ||
254 (!source_routed && frame_type == 1)) {
255 /* look for SNAP or IPX only */
256 if ( (pd[offset + 0x20] == 0xaa && pd[offset + 0x21] == 0xaa && pd[offset + 0x22] == 03) ||
257 (pd[offset + 0x20] == 0xe0 && pd[offset + 0x21] == 0xe0) ) {
258 actual_rif_bytes = 18;
260 pd[offset + 0x23] == 0 &&
261 pd[offset + 0x24] == 0 &&
262 pd[offset + 0x25] == 0 &&
263 pd[offset + 0x26] == 0x00 &&
264 pd[offset + 0x27] == 0x11) {
266 actual_rif_bytes = 18;
268 /* Linux 2.0.x also requires drivers pass up a fake SNAP and LLC header before th
269 real LLC hdr for all Token Ring frames that arrive with DSAP and SSAP != 0xAA
270 (i.e. for non SNAP frames e.g. for Netware frames)
271 the fake SNAP header has the ETH_P_TR_802_2 ether type (0x0011) and the protocol id
272 bytes as zero frame looks like :-
273 TR Header | Fake LLC | Fake SNAP | Wire LLC | Rest of data */
274 offset += 8; /* Skip fake LLC and SNAP */
278 offset += actual_rif_bytes + TR_MIN_HEADER_LEN;
280 /* The package is either MAC or LLC */
281 switch (frame_type) {
287 capture_llc(pd, offset, ld);
290 /* non-MAC, non-LLC, i.e., "Reserved" */
298 dissect_tr(tvbuff_t *tvb, packet_info *pinfo, proto_tree *tree)
300 proto_tree *tr_tree, *bf_tree;
306 volatile int fixoffset = 0;
307 volatile int source_routed = 0;
308 volatile guint8 trn_rif_bytes;
309 volatile guint8 actual_rif_bytes;
310 volatile guint8 c1_nonsr;
311 volatile guint8 c2_nonsr;
312 volatile guint16 first2_sr;
313 tvbuff_t *volatile tr_tvb;
315 /* The trn_hdr struct, as separate variables */
316 guint8 trn_ac; /* access control field */
317 guint8 trn_fc; /* field control field */
318 const guint8 *trn_dhost; /* destination host */
319 const guint8 *trn_shost; /* source host */
321 /* non-source-routed version of source addr */
322 static guint8 trn_shost_nonsr[6];
325 /* Token-Ring Strings */
326 char *fc[] = { "MAC", "LLC", "Reserved", "Unknown" };
328 CHECK_DISPLAY_AS_DATA(proto_tr, tvb, pinfo, tree);
330 pinfo->current_proto = "Token-Ring";
332 if (check_col(pinfo->fd, COL_PROTOCOL))
333 col_set_str(pinfo->fd, COL_PROTOCOL, "TR");
335 if ((x = check_for_old_linux_tvb((tvbuff_t*) tvb))) {
336 /* Actually packet starts x bytes into what we have got but with all
337 source routing compressed. See comment above */
338 tr_tvb = tvb_new_subset((tvbuff_t*) tvb, x, -1, -1);
345 trn_fc = tvb_get_guint8(tr_tvb, 1);
346 trn_dhost = tvb_get_ptr(tr_tvb, 2, 6);
347 trn_shost = tvb_get_ptr(tr_tvb, 8, 6);
350 memcpy(trn_shost_nonsr, trn_shost, 6);
351 trn_shost_nonsr[0] &= 127;
352 frame_type = (trn_fc & 192) >> 6;
354 if (check_col(pinfo->fd, COL_INFO))
355 col_add_fstr(pinfo->fd, COL_INFO, "Token-Ring %s", fc[frame_type]);
357 /* if the high bit on the first byte of src hwaddr is 1, then
358 this packet is source-routed */
359 source_routed = trn_shost[0] & 128;
361 trn_rif_bytes = tvb_get_guint8(tr_tvb, 14) & 31;
363 /* the Linux 2.0 TR code strips source-route bits in
364 * order to test for SR. This can be removed from most
365 * packets with oltr, but not all. So, I try to figure out
366 * which packets should have been SR here. I'll check to
367 * see if there's a SNAP or IPX field right after
370 if (!source_routed && trn_rif_bytes > 0) {
373 c1_nonsr = tvb_get_guint8(tr_tvb, 14);
374 c2_nonsr = tvb_get_guint8(tr_tvb, 15);
376 if (c1_nonsr != c2_nonsr) {
378 first2_sr = tvb_get_ntohs(tr_tvb, trn_rif_bytes + 0x0e);
380 if ( ( first2_sr == 0xaaaa &&
381 tvb_get_guint8(tr_tvb, trn_rif_bytes + 0x10) == 0x03) ||
383 first2_sr == 0xe0e0 ||
384 first2_sr == 0xe0aa ) {
391 /* We had no information beyond the TR header. Just assume
392 * this is a normal (non-Linux) TR header. */
399 actual_rif_bytes = trn_rif_bytes;
403 actual_rif_bytes = 0;
406 /* this is a silly hack for Linux 2.0.x. Read the comment below,
407 in front of the other #ifdef linux. If we're sniffing our own NIC,
408 we get a full RIF, sometimes with garbage */
410 if ((source_routed && trn_rif_bytes == 2 && frame_type == 1) ||
411 (!source_routed && frame_type == 1)) {
412 /* look for SNAP or IPX only */
414 (tvb_get_ntohs(tr_tvb, 0x20) == 0xaaaa &&
415 tvb_get_guint8(tr_tvb, 0x22) == 0x03)
417 tvb_get_ntohs(tr_tvb, 0x20) == 0xe0e0 ) {
419 actual_rif_bytes = 18;
422 tvb_get_ntohl(tr_tvb, 0x23) == 0 &&
423 tvb_get_guint8(tr_tvb, 0x27) == 0x11) {
425 actual_rif_bytes = 18;
427 /* Linux 2.0.x also requires drivers pass up a fake SNAP and LLC header before th
428 real LLC hdr for all Token Ring frames that arrive with DSAP and SSAP != 0xAA
429 (i.e. for non SNAP frames e.g. for Netware frames)
430 the fake SNAP header has the ETH_P_TR_802_2 ether type (0x0011) and the protocol id
431 bytes as zero frame looks like :-
432 TR Header | Fake LLC | Fake SNAP | Wire LLC | Rest of data */
433 fixoffset += 8; /* Skip fake LLC and SNAP */
438 /* We had no information beyond the TR header. Just assume
439 * this is a normal (non-Linux) TR header. */
445 /* XXX - copy it to some buffer associated with "pi", rather than
446 just making "trn_shost_nonsr" static? */
447 SET_ADDRESS(&pi.dl_src, AT_ETHER, 6, trn_shost_nonsr);
448 SET_ADDRESS(&pi.src, AT_ETHER, 6, trn_shost_nonsr);
449 SET_ADDRESS(&pi.dl_dst, AT_ETHER, 6, trn_dhost);
450 SET_ADDRESS(&pi.dst, AT_ETHER, 6, trn_dhost);
452 /* protocol analysis tree */
454 /* Create Token-Ring Tree */
455 ti = proto_tree_add_item(tree, proto_tr, tr_tvb, 0, TR_MIN_HEADER_LEN + actual_rif_bytes, FALSE);
456 tr_tree = proto_item_add_subtree(ti, ett_token_ring);
458 /* Create the Access Control bitfield tree */
459 trn_ac = tvb_get_guint8(tr_tvb, 0);
460 ti = proto_tree_add_uint(tr_tree, hf_tr_ac, tr_tvb, 0, 1, trn_ac);
461 bf_tree = proto_item_add_subtree(ti, ett_token_ring_ac);
463 proto_tree_add_uint(bf_tree, hf_tr_priority, tr_tvb, 0, 1, trn_ac);
464 proto_tree_add_boolean(bf_tree, hf_tr_frame, tr_tvb, 0, 1, trn_ac);
465 proto_tree_add_uint(bf_tree, hf_tr_monitor_cnt, tr_tvb, 0, 1, trn_ac);
466 proto_tree_add_uint(bf_tree, hf_tr_priority_reservation, tr_tvb, 0, 1, trn_ac);
468 /* Create the Frame Control bitfield tree */
469 ti = proto_tree_add_uint(tr_tree, hf_tr_fc, tr_tvb, 1, 1, trn_fc);
470 bf_tree = proto_item_add_subtree(ti, ett_token_ring_fc);
472 proto_tree_add_uint(bf_tree, hf_tr_fc_type, tr_tvb, 1, 1, trn_fc);
473 proto_tree_add_uint(bf_tree, hf_tr_fc_pcf, tr_tvb, 1, 1, trn_fc);
474 proto_tree_add_ether(tr_tree, hf_tr_dst, tr_tvb, 2, 6, trn_dhost);
475 proto_tree_add_ether(tr_tree, hf_tr_src, tr_tvb, 8, 6, trn_shost);
476 proto_tree_add_ether_hidden(tr_tree, hf_tr_addr, tr_tvb, 2, 6, trn_dhost);
477 proto_tree_add_ether_hidden(tr_tree, hf_tr_addr, tr_tvb, 8, 6, trn_shost);
479 proto_tree_add_boolean(tr_tree, hf_tr_sr, tr_tvb, 8, 1, source_routed);
481 /* non-source-routed version of src addr */
482 proto_tree_add_ether_hidden(tr_tree, hf_tr_src, tr_tvb, 8, 6, trn_shost_nonsr);
486 rcf1 = tvb_get_guint8(tr_tvb, 14);
487 proto_tree_add_uint(tr_tree, hf_tr_rif_bytes, tr_tvb, 14, 1, trn_rif_bytes);
488 proto_tree_add_uint(tr_tree, hf_tr_broadcast, tr_tvb, 14, 1, rcf1 & 224);
491 rcf2 = tvb_get_guint8(tr_tvb, 15);
492 proto_tree_add_uint(tr_tree, hf_tr_max_frame_size, tr_tvb, 15, 1, rcf2 & 112);
493 proto_tree_add_uint(tr_tree, hf_tr_direction, tr_tvb, 15, 1, rcf2 & 128);
495 /* if we have more than 2 bytes of RIF, then we have
497 if (trn_rif_bytes > 2) {
498 add_ring_bridge_pairs(trn_rif_bytes, tr_tvb, tr_tree);
502 /* Linux 2.0.x has a problem in that the 802.5 code creates
503 an emtpy full (18-byte) RIF area. It's up to the tr driver to
504 either fill it in or remove it before sending the bytes out
505 to the wire. If you run tcpdump on a Linux 2.0.x machine running
506 token-ring, tcpdump will capture these 18 filler bytes. They
507 are filled with garbage. The best way to detect this problem is
508 to know the src hwaddr of the machine from which you were running
509 tcpdump. W/o that, however, I'm guessing that DSAP == SSAP if the
510 frame type is LLC. It's very much a hack. */
511 if (actual_rif_bytes > trn_rif_bytes) {
512 proto_tree_add_text(tr_tree, tr_tvb, TR_MIN_HEADER_LEN + trn_rif_bytes, actual_rif_bytes - trn_rif_bytes,
513 "Empty RIF from Linux 2.0.x driver. The sniffing NIC "
514 "is also running a protocol stack.");
517 proto_tree_add_text(tr_tree, tr_tvb, TR_MIN_HEADER_LEN + 18,8,"Linux 2.0.x fake LLC and SNAP header");
521 next_tvb = tvb_new_subset(tr_tvb, TR_MIN_HEADER_LEN + actual_rif_bytes + fixoffset, -1, -1);
523 /* The package is either MAC or LLC */
524 switch (frame_type) {
527 call_dissector(trmac_handle, next_tvb, pinfo, tree);
530 call_dissector(llc_handle, next_tvb, pinfo, tree);
533 /* non-MAC, non-LLC, i.e., "Reserved" */
534 dissect_data(next_tvb, 0, pinfo, tree);
539 /* this routine is taken from the Linux net/802/tr.c code, which shows
540 ring-bridge pairs in the /proc/net/tr_rif virtual file. */
542 add_ring_bridge_pairs(int rcf_len, tvbuff_t *tvb, proto_tree *tree)
545 int segment, brdgnmb, unprocessed_rif;
548 #define RIF_OFFSET 16
549 #define RIF_BYTES_TO_PROCESS 30
551 char buffer[3 + (RIF_BYTES_TO_PROCESS / 2) * 6 + 1];
553 /* Only process so many bytes of RIF, as per TR spec, and not overflow
554 * static buffer above */
555 unprocessed_rif = rcf_len - RIF_BYTES_TO_PROCESS;
556 rcf_len = MIN(rcf_len, RIF_BYTES_TO_PROCESS);
558 /* Ignore the 2 RCF bytes, since they don't make up the ring/bride pairs */
561 for(j = 1; j < rcf_len - 1; j += 2) {
563 segment = tvb_get_ntohs(tvb, RIF_OFFSET) >> 4;
564 size = sprintf(buffer, "%03X",segment);
565 proto_tree_add_uint_hidden(tree, hf_tr_rif_ring, tvb, TR_MIN_HEADER_LEN + 2, 2, segment);
568 segment = tvb_get_ntohs(tvb, RIF_OFFSET + 1 + j) >> 4;
569 brdgnmb = tvb_get_guint8(tvb, RIF_OFFSET + j) & 0x0f;
570 size = sprintf(buffer+buff_offset, "-%01X-%03X",brdgnmb,segment);
571 proto_tree_add_uint_hidden(tree, hf_tr_rif_ring, tvb, TR_MIN_HEADER_LEN + 3 + j, 2, segment);
572 proto_tree_add_uint_hidden(tree, hf_tr_rif_bridge, tvb, TR_MIN_HEADER_LEN + 2 + j, 1, brdgnmb);
575 proto_tree_add_string(tree, hf_tr_rif, tvb, TR_MIN_HEADER_LEN + 2, rcf_len, buffer);
577 if (unprocessed_rif > 0) {
578 proto_tree_add_text(tree, tvb, TR_MIN_HEADER_LEN + RIF_BYTES_TO_PROCESS, unprocessed_rif,
579 "Extra RIF bytes beyond spec: %d", unprocessed_rif);
584 proto_register_tr(void)
586 static hf_register_info hf[] = {
588 { "Access Control", "tr.ac", FT_UINT8, BASE_HEX, NULL, 0x0,
592 { "Priority", "tr.priority", FT_UINT8, BASE_DEC, NULL, 0xe0,
596 { "Frame", "tr.frame", FT_BOOLEAN, 8, TFS(&ac_truth), 0x10,
599 { &hf_tr_monitor_cnt,
600 { "Monitor Count", "tr.monitor_cnt", FT_UINT8, BASE_DEC, NULL, 0x08,
603 { &hf_tr_priority_reservation,
604 { "Priority Reservation","tr.priority_reservation", FT_UINT8, BASE_DEC, NULL, 0x07,
608 { "Frame Control", "tr.fc", FT_UINT8, BASE_HEX, NULL, 0x0,
612 { "Frame Type", "tr.frame_type", FT_UINT8, BASE_DEC, VALS(frame_vals), 0xc0,
616 { "Frame PCF", "tr.frame_pcf", FT_UINT8, BASE_DEC, VALS(pcf_vals), 0x0f,
620 { "Destination", "tr.dst", FT_ETHER, BASE_NONE, NULL, 0x0,
621 "Destination Hardware Address" }},
624 { "Source", "tr.src", FT_ETHER, BASE_NONE, NULL, 0x0,
625 "Source Hardware Address" }},
628 { "Source or Destination Address", "tr.addr", FT_ETHER, BASE_NONE, NULL, 0x0,
629 "Source or Destination Hardware Address" }},
632 { "Source Routed", "tr.sr", FT_BOOLEAN, BASE_NONE, NULL, 0x0,
636 { "RIF Bytes", "tr.rif_bytes", FT_UINT8, BASE_DEC, NULL, 0x0,
637 "Number of bytes in Routing Information Fields, including "
638 "the two bytes of Routing Control Field" }},
641 { "Broadcast Type", "tr.broadcast", FT_UINT8, BASE_DEC, VALS(broadcast_vals), 0x0,
642 "Type of Token-Ring Broadcast" }},
644 { &hf_tr_max_frame_size,
645 { "Maximum Frame Size", "tr.max_frame_size", FT_UINT8, BASE_DEC, VALS(max_frame_size_vals),
650 { "Direction", "tr.direction", FT_UINT8, BASE_DEC, VALS(direction_vals), 0x0,
651 "Direction of RIF" }},
654 { "Ring-Bridge Pairs", "tr.rif", FT_STRING, BASE_NONE, NULL, 0x0,
655 "String representing Ring-Bridge Pairs" }},
658 { "RIF Ring", "tr.rif.ring", FT_UINT16, BASE_HEX, NULL, 0x0,
662 { "RIF Bridge", "tr.rif.bridge", FT_UINT8, BASE_HEX, NULL, 0x0,
665 static gint *ett[] = {
671 proto_tr = proto_register_protocol("Token-Ring", "Token-Ring", "tr");
672 proto_register_field_array(proto_tr, hf, array_length(hf));
673 proto_register_subtree_array(ett, array_length(ett));
677 proto_reg_handoff_tr(void)
680 * Get handles for the TR MAC and LLC dissectors.
682 trmac_handle = find_dissector("trmac");
683 llc_handle = find_dissector("llc");
685 dissector_add("wtap_encap", WTAP_ENCAP_TOKEN_RING, dissect_tr);