2 * Routines for the Generic Routing Encapsulation (GRE) protocol
3 * Brad Robel-Forrest <brad.robel-forrest@watchguard.com>
5 * $Id: packet-gre.c,v 1.54 2003/06/10 05:38:52 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.
31 #include <epan/packet.h>
32 #include "packet-wccp.h"
40 * See RFC 1701 "Generic Routing Encapsulation (GRE)", RFC 1702
41 * "Generic Routing Encapsulation over IPv4 networks", RFC 2637
42 * "Point-to-Point Tunneling Protocol (PPTP)", RFC 2784 "Generic
43 * Routing Encapsulation (GRE)", and RFC 2890 "Key and Sequence
44 * Number Extensions to GRE".
47 static int proto_gre = -1;
48 static int hf_gre_proto = -1;
50 static gint ett_gre = -1;
51 static gint ett_gre_flags = -1;
52 static gint ett_gre_wccp2_redirect_header = -1;
54 static dissector_table_t gre_dissector_table;
55 static dissector_handle_t data_handle;
57 /* bit positions for flags in header */
63 #define GH_B_RECUR 0x0700
64 #define GH_P_A 0x0080 /* only in special PPTPized GRE header */
65 #define GH_P_FLAGS 0x0078 /* only in special PPTPized GRE header */
66 #define GH_R_FLAGS 0x00F8
67 #define GH_B_VER 0x0007
69 static void add_flags_and_ver(proto_tree *, guint16, tvbuff_t *, int, int);
70 static void dissect_gre_wccp2_redirect_header(tvbuff_t *, int, proto_tree *);
72 static const value_string typevals[] = {
73 { ETHERTYPE_PPP, "PPP" },
74 { ETHERTYPE_IP, "IP" },
77 { ETHERTYPE_IPX, "IPX"},
78 { ETHERTYPE_ETHBRIDGE, "Transparent Ethernet bridging" },
79 { GRE_FR, "Frame Relay"},
84 dissect_gre(tvbuff_t *tvb, packet_info *pinfo, proto_tree *tree)
87 guint16 flags_and_ver;
89 gboolean is_ppp = FALSE;
90 gboolean is_wccp2 = FALSE;
93 proto_tree *gre_tree = NULL;
98 flags_and_ver = tvb_get_ntohs(tvb, offset);
99 type = tvb_get_ntohs(tvb, offset + sizeof(flags_and_ver));
101 if (check_col(pinfo->cinfo, COL_PROTOCOL))
102 col_set_str(pinfo->cinfo, COL_PROTOCOL, "GRE");
104 if (check_col(pinfo->cinfo, COL_INFO)) {
105 col_add_fstr(pinfo->cinfo, COL_INFO, "Encapsulated %s",
106 val_to_str(type, typevals, "0x%04X (unknown)"));
109 if (flags_and_ver & GH_B_C || flags_and_ver & GH_B_R)
111 if (flags_and_ver & GH_B_K)
113 if (flags_and_ver & GH_B_S)
118 if (flags_and_ver & GH_P_A)
124 /* WCCP2 puts an extra 4 octets into the header, but uses the same
125 encapsulation type; if it looks as if the first octet of the packet
126 isn't the beginning of an IPv4 header, assume it's WCCP2. */
127 if ((tvb_get_guint8(tvb, offset + sizeof(flags_and_ver) + sizeof(type)) & 0xF0) != 0x40) {
135 ti = proto_tree_add_protocol_format(tree, proto_gre, tvb, offset, len,
136 "Generic Routing Encapsulation (%s)",
137 val_to_str(type, typevals, "0x%04X - unknown"));
138 gre_tree = proto_item_add_subtree(ti, ett_gre);
139 add_flags_and_ver(gre_tree, flags_and_ver, tvb, offset, is_ppp);
141 offset += sizeof(flags_and_ver);
144 proto_tree_add_uint(gre_tree, hf_gre_proto, tvb, offset, sizeof(type), type);
146 offset += sizeof(type);
148 if (flags_and_ver & GH_B_C || flags_and_ver & GH_B_R) {
150 guint length, reported_length;
152 guint16 cksum, computed_cksum;
154 cksum = tvb_get_ntohs(tvb, offset);
155 length = tvb_length(tvb);
156 reported_length = tvb_reported_length(tvb);
157 if ((flags_and_ver & GH_B_C) && !pinfo->fragmented
158 && length >= reported_length) {
159 /* The Checksum Present bit is set, and the packet isn't part of a
160 fragmented datagram and isn't truncated, so we can checksum it. */
162 cksum_vec[0].ptr = tvb_get_ptr(tvb, 0, reported_length);
163 cksum_vec[0].len = reported_length;
164 computed_cksum = in_cksum(cksum_vec, 1);
165 if (computed_cksum == 0) {
166 proto_tree_add_text(gre_tree, tvb, offset, 2,
167 "Checksum: 0x%04x (correct)", cksum);
169 proto_tree_add_text(gre_tree, tvb, offset, 2,
170 "Checksum: 0x%04x (incorrect, should be 0x%04x)",
171 cksum, in_cksum_shouldbe(cksum, computed_cksum));
174 proto_tree_add_text(gre_tree, tvb, offset, 2,
175 "Checksum: 0x%04x", cksum);
181 if (flags_and_ver & GH_B_C || flags_and_ver & GH_B_R) {
183 proto_tree_add_text(gre_tree, tvb, offset, 2,
184 "Offset: %u", tvb_get_ntohs(tvb, offset));
189 if (flags_and_ver & GH_B_K) {
192 proto_tree_add_text(gre_tree, tvb, offset, 2,
193 "Payload length: %u", tvb_get_ntohs(tvb, offset));
197 proto_tree_add_text(gre_tree, tvb, offset, 2,
198 "Call ID: %u", tvb_get_ntohs(tvb, offset));
204 proto_tree_add_text(gre_tree, tvb, offset, 4,
205 "Key: %u", tvb_get_ntohl(tvb, offset));
211 if (flags_and_ver & GH_B_S) {
213 proto_tree_add_text(gre_tree, tvb, offset, 4,
214 "Sequence number: %u", tvb_get_ntohl(tvb, offset));
219 if (is_ppp && flags_and_ver & GH_P_A) {
221 proto_tree_add_text(gre_tree, tvb, offset, 4,
222 "Acknowledgement number: %u", tvb_get_ntohl(tvb, offset));
227 if (flags_and_ver & GH_B_R) {
229 sre_af = tvb_get_ntohs(tvb, offset);
231 proto_tree_add_text(gre_tree, tvb, offset, sizeof(guint16),
232 "Address family: %u", sre_af);
234 offset += sizeof(guint16);
236 proto_tree_add_text(gre_tree, tvb, offset, 1,
237 "SRE offset: %u", tvb_get_guint8(tvb, offset));
239 offset += sizeof(guint8);
240 sre_length = tvb_get_guint8(tvb, offset);
242 proto_tree_add_text(gre_tree, tvb, offset, sizeof(guint8),
243 "SRE length: %u", sre_length);
245 offset += sizeof(guint8);
246 if (sre_af == 0 && sre_length == 0)
248 offset += sre_length;
252 if (type == GRE_WCCP) {
255 dissect_gre_wccp2_redirect_header(tvb, offset, gre_tree);
260 /* If the S bit is not set, this packet might not have a payload, so
261 check whether there's any data left, first.
263 XXX - the S bit isn't in RFC 2784, which deprecates that bit
264 and some other bits in RFC 1701 and says that they should be
265 zero for RFC 2784-compliant GRE; as such, the absence of the
266 S bit doesn't necessarily mean there's no payload. */
267 if (!(flags_and_ver & GH_B_S)) {
268 if (tvb_reported_length_remaining(tvb, offset) <= 0)
269 return; /* no payload */
271 next_tvb = tvb_new_subset(tvb, offset, -1, -1);
272 if (!dissector_try_port(gre_dissector_table, type, next_tvb, pinfo, tree))
273 call_dissector(data_handle,next_tvb, pinfo, gre_tree);
277 add_flags_and_ver(proto_tree *tree, guint16 flags_and_ver, tvbuff_t *tvb,
278 int offset, int is_ppp)
281 proto_tree * fv_tree;
282 int nbits = sizeof(flags_and_ver) * 8;
284 ti = proto_tree_add_text(tree, tvb, offset, 2,
285 "Flags and version: %#04x", flags_and_ver);
286 fv_tree = proto_item_add_subtree(ti, ett_gre_flags);
288 proto_tree_add_text(fv_tree, tvb, offset, sizeof(flags_and_ver), "%s",
289 decode_boolean_bitfield(flags_and_ver, GH_B_C, nbits,
290 "Checksum", "No checksum"));
291 proto_tree_add_text(fv_tree, tvb, offset, sizeof(flags_and_ver), "%s",
292 decode_boolean_bitfield(flags_and_ver, GH_B_R, nbits,
293 "Routing", "No routing"));
294 proto_tree_add_text(fv_tree, tvb, offset, sizeof(flags_and_ver), "%s",
295 decode_boolean_bitfield(flags_and_ver, GH_B_K, nbits,
297 proto_tree_add_text(fv_tree, tvb, offset, sizeof(flags_and_ver), "%s",
298 decode_boolean_bitfield(flags_and_ver, GH_B_S, nbits,
299 "Sequence number", "No sequence number"));
300 proto_tree_add_text(fv_tree, tvb, offset, sizeof(flags_and_ver), "%s",
301 decode_boolean_bitfield(flags_and_ver, GH_B_s, nbits,
302 "Strict source route", "No strict source route"));
303 proto_tree_add_text(fv_tree, tvb, offset, sizeof(flags_and_ver), "%s",
304 decode_numeric_bitfield(flags_and_ver, GH_B_RECUR, nbits,
305 "Recursion control: %u"));
307 proto_tree_add_text(fv_tree, tvb, offset, sizeof(flags_and_ver), "%s",
308 decode_boolean_bitfield(flags_and_ver, GH_P_A, nbits,
309 "Acknowledgment number", "No acknowledgment number"));
310 proto_tree_add_text(fv_tree, tvb, offset, sizeof(flags_and_ver), "%s",
311 decode_numeric_bitfield(flags_and_ver, GH_P_FLAGS, nbits,
315 proto_tree_add_text(fv_tree, tvb, offset, sizeof(flags_and_ver), "%s",
316 decode_numeric_bitfield(flags_and_ver, GH_R_FLAGS, nbits,
320 proto_tree_add_text(fv_tree, tvb, offset, sizeof(flags_and_ver), "%s",
321 decode_numeric_bitfield(flags_and_ver, GH_B_VER, nbits,
326 dissect_gre_wccp2_redirect_header(tvbuff_t *tvb, int offset, proto_tree *tree)
329 proto_tree * rh_tree;
332 ti = proto_tree_add_text(tree, tvb, offset, 4, "Redirect header");
333 rh_tree = proto_item_add_subtree(ti, ett_gre_wccp2_redirect_header);
335 rh_flags = tvb_get_guint8(tvb, offset);
336 proto_tree_add_text(rh_tree, tvb, offset, 1, "%s",
337 decode_boolean_bitfield(rh_flags, 0x80, 8,
338 "Dynamic service", "Well-known service"));
339 proto_tree_add_text(rh_tree, tvb, offset, 1, "%s",
340 decode_boolean_bitfield(rh_flags, 0x40, 8,
341 "Alternative bucket used", "Alternative bucket not used"));
343 proto_tree_add_text(rh_tree, tvb, offset + 1, 1, "Service ID: %s",
344 val_to_str(tvb_get_guint8(tvb, offset + 1), service_id_vals, "Unknown (0x%02X)"));
346 proto_tree_add_text(rh_tree, tvb, offset + 2, 1, "Alternative bucket index: %u",
347 tvb_get_guint8(tvb, offset + 2));
348 proto_tree_add_text(rh_tree, tvb, offset + 3, 1, "Primary bucket index: %u",
349 tvb_get_guint8(tvb, offset + 3));
353 proto_register_gre(void)
355 static hf_register_info hf[] = {
357 { "Protocol Type", "gre.proto", FT_UINT16, BASE_HEX, VALS(typevals), 0x0,
358 "The protocol that is GRE encapsulated", HFILL }
361 static gint *ett[] = {
364 &ett_gre_wccp2_redirect_header,
367 proto_gre = proto_register_protocol("Generic Routing Encapsulation",
369 proto_register_field_array(proto_gre, hf, array_length(hf));
370 proto_register_subtree_array(ett, array_length(ett));
372 /* subdissector code */
373 gre_dissector_table = register_dissector_table("gre.proto",
374 "GRE protocol type", FT_UINT16, BASE_HEX);
378 proto_reg_handoff_gre(void)
380 dissector_handle_t gre_handle;
382 gre_handle = create_dissector_handle(dissect_gre, proto_gre);
383 dissector_add("ip.proto", IP_PROTO_GRE, gre_handle);
384 data_handle = find_dissector("data");