2 * Routines for the Generic Routing Encapsulation (GRE) protocol
3 * Brad Robel-Forrest <brad.robel-forrest@watchguard.com>
5 * $Id: packet-gre.c,v 1.50 2002/01/21 07:36:34 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>
34 #ifdef HAVE_NETINET_IN_H
35 #include <netinet/in.h>
38 #include <epan/packet.h>
39 #include "packet-wccp.h"
46 * See RFC 1701 "Generic Routing Encapsulation (GRE)", RFC 1702
47 * "Generic Routing Encapsulation over IPv4 networks", RFC 2637
48 * "Point-to-Point Tunneling Protocol (PPTP)", RFC 2784 "Generic
49 * Routing Encapsulation (GRE)", and RFC 2890 "Key and Sequence
50 * Number Extensions to GRE".
53 static int proto_gre = -1;
54 static int hf_gre_proto = -1;
56 static gint ett_gre = -1;
57 static gint ett_gre_flags = -1;
58 static gint ett_gre_wccp2_redirect_header = -1;
60 static dissector_table_t gre_dissector_table;
61 static dissector_handle_t data_handle;
63 /* bit positions for flags in header */
69 #define GH_B_RECUR 0x0700
70 #define GH_P_A 0x0080 /* only in special PPTPized GRE header */
71 #define GH_P_FLAGS 0x0078 /* only in special PPTPized GRE header */
72 #define GH_R_FLAGS 0x00F8
73 #define GH_B_VER 0x0007
75 static void add_flags_and_ver(proto_tree *, guint16, tvbuff_t *, int, int);
76 static void dissect_gre_wccp2_redirect_header(tvbuff_t *, int, proto_tree *);
78 static const value_string typevals[] = {
79 { ETHERTYPE_PPP, "PPP" },
80 { ETHERTYPE_IP, "IP" },
82 { ETHERTYPE_IPX, "IPX"},
83 { ETHERTYPE_ETHBRIDGE, "Transparent Ethernet bridging" },
84 { GRE_FR, "Frame Relay"},
89 dissect_gre(tvbuff_t *tvb, packet_info *pinfo, proto_tree *tree)
92 guint16 flags_and_ver;
94 gboolean is_ppp = FALSE;
95 gboolean is_wccp2 = FALSE;
98 proto_tree *gre_tree = NULL;
103 flags_and_ver = tvb_get_ntohs(tvb, offset);
104 type = tvb_get_ntohs(tvb, offset + sizeof(flags_and_ver));
106 if (check_col(pinfo->cinfo, COL_PROTOCOL))
107 col_set_str(pinfo->cinfo, COL_PROTOCOL, "GRE");
109 if (check_col(pinfo->cinfo, COL_INFO)) {
110 col_add_fstr(pinfo->cinfo, COL_INFO, "Encapsulated %s",
111 val_to_str(type, typevals, "0x%04X (unknown)"));
114 if (flags_and_ver & GH_B_C || flags_and_ver & GH_B_R)
116 if (flags_and_ver & GH_B_K)
118 if (flags_and_ver & GH_B_S)
123 if (flags_and_ver & GH_P_A)
129 /* WCCP2 puts an extra 4 octets into the header, but uses the same
130 encapsulation type; if it looks as if the first octet of the packet
131 isn't the beginning of an IPv4 header, assume it's WCCP2. */
132 if ((tvb_get_guint8(tvb, offset + sizeof(flags_and_ver) + sizeof(type)) & 0xF0) != 0x40) {
140 ti = proto_tree_add_protocol_format(tree, proto_gre, tvb, offset, len,
141 "Generic Routing Encapsulation (%s)",
142 val_to_str(type, typevals, "0x%04X - unknown"));
143 gre_tree = proto_item_add_subtree(ti, ett_gre);
144 add_flags_and_ver(gre_tree, flags_and_ver, tvb, offset, is_ppp);
146 offset += sizeof(flags_and_ver);
149 proto_tree_add_uint(gre_tree, hf_gre_proto, tvb, offset, sizeof(type), type);
151 offset += sizeof(type);
153 if (flags_and_ver & GH_B_C || flags_and_ver & GH_B_R) {
155 guint length, reported_length;
157 guint16 cksum, computed_cksum;
159 cksum = tvb_get_ntohs(tvb, offset);
160 length = tvb_length(tvb);
161 reported_length = tvb_reported_length(tvb);
162 if ((flags_and_ver & GH_B_C) && !pinfo->fragmented
163 && length >= reported_length) {
164 /* The Checksum Present bit is set, and the packet isn't part of a
165 fragmented datagram and isn't truncated, so we can checksum it. */
167 cksum_vec[0].ptr = tvb_get_ptr(tvb, 0, reported_length);
168 cksum_vec[0].len = reported_length;
169 computed_cksum = in_cksum(cksum_vec, 1);
170 if (computed_cksum == 0) {
171 proto_tree_add_text(gre_tree, tvb, offset, 2,
172 "Checksum: 0x%04x (correct)", cksum);
174 proto_tree_add_text(gre_tree, tvb, offset, 2,
175 "Checksum: 0x%04x (incorrect, should be 0x%04x)",
176 cksum, in_cksum_shouldbe(cksum, computed_cksum));
179 proto_tree_add_text(gre_tree, tvb, offset, 2,
180 "Checksum: 0x%04x", cksum);
186 if (flags_and_ver & GH_B_C || flags_and_ver & GH_B_R) {
188 proto_tree_add_text(gre_tree, tvb, offset, 2,
189 "Offset: %u", tvb_get_ntohs(tvb, offset));
194 if (flags_and_ver & GH_B_K) {
197 proto_tree_add_text(gre_tree, tvb, offset, 2,
198 "Payload length: %u", tvb_get_ntohs(tvb, offset));
202 proto_tree_add_text(gre_tree, tvb, offset, 2,
203 "Call ID: %u", tvb_get_ntohs(tvb, offset));
209 proto_tree_add_text(gre_tree, tvb, offset, 4,
210 "Key: %u", tvb_get_ntohl(tvb, offset));
216 if (flags_and_ver & GH_B_S) {
218 proto_tree_add_text(gre_tree, tvb, offset, 4,
219 "Sequence number: %u", tvb_get_ntohl(tvb, offset));
224 if (is_ppp && flags_and_ver & GH_P_A) {
226 proto_tree_add_text(gre_tree, tvb, offset, 4,
227 "Acknowledgement number: %u", tvb_get_ntohl(tvb, offset));
232 if (flags_and_ver & GH_B_R) {
234 sre_af = tvb_get_ntohs(tvb, offset);
236 proto_tree_add_text(gre_tree, tvb, offset, sizeof(guint16),
237 "Address family: %u", sre_af);
239 offset += sizeof(guint16);
241 proto_tree_add_text(gre_tree, tvb, offset, 1,
242 "SRE offset: %u", tvb_get_guint8(tvb, offset));
244 offset += sizeof(guint8);
245 sre_length = tvb_get_guint8(tvb, offset);
247 proto_tree_add_text(gre_tree, tvb, offset, sizeof(guint8),
248 "SRE length: %u", sre_length);
250 offset += sizeof(guint8);
251 if (sre_af == 0 && sre_length == 0)
253 offset += sre_length;
257 if (type == GRE_WCCP) {
260 dissect_gre_wccp2_redirect_header(tvb, offset, gre_tree);
265 /* If the S bit is not set, this packet might not have a payload, so
266 check whether there's any data left, first.
268 XXX - the S bit isn't in RFC 2784, which deprecates that bit
269 and some other bits in RFC 1701 and says that they should be
270 zero for RFC 2784-compliant GRE; as such, the absence of the
271 S bit doesn't necessarily mean there's no payload. */
272 if (!(flags_and_ver & GH_B_S)) {
273 if (tvb_reported_length_remaining(tvb, offset) <= 0)
274 return; /* no payload */
276 next_tvb = tvb_new_subset(tvb, offset, -1, -1);
277 if (!dissector_try_port(gre_dissector_table, type, next_tvb, pinfo, tree))
278 call_dissector(data_handle,next_tvb, pinfo, gre_tree);
282 add_flags_and_ver(proto_tree *tree, guint16 flags_and_ver, tvbuff_t *tvb,
283 int offset, int is_ppp)
286 proto_tree * fv_tree;
287 int nbits = sizeof(flags_and_ver) * 8;
289 ti = proto_tree_add_text(tree, tvb, offset, 2,
290 "Flags and version: %#04x", flags_and_ver);
291 fv_tree = proto_item_add_subtree(ti, ett_gre_flags);
293 proto_tree_add_text(fv_tree, tvb, offset, sizeof(flags_and_ver), "%s",
294 decode_boolean_bitfield(flags_and_ver, GH_B_C, nbits,
295 "Checksum", "No checksum"));
296 proto_tree_add_text(fv_tree, tvb, offset, sizeof(flags_and_ver), "%s",
297 decode_boolean_bitfield(flags_and_ver, GH_B_R, nbits,
298 "Routing", "No routing"));
299 proto_tree_add_text(fv_tree, tvb, offset, sizeof(flags_and_ver), "%s",
300 decode_boolean_bitfield(flags_and_ver, GH_B_K, nbits,
302 proto_tree_add_text(fv_tree, tvb, offset, sizeof(flags_and_ver), "%s",
303 decode_boolean_bitfield(flags_and_ver, GH_B_S, nbits,
304 "Sequence number", "No sequence number"));
305 proto_tree_add_text(fv_tree, tvb, offset, sizeof(flags_and_ver), "%s",
306 decode_boolean_bitfield(flags_and_ver, GH_B_s, nbits,
307 "Strict source route", "No strict source route"));
308 proto_tree_add_text(fv_tree, tvb, offset, sizeof(flags_and_ver), "%s",
309 decode_numeric_bitfield(flags_and_ver, GH_B_RECUR, nbits,
310 "Recursion control: %u"));
312 proto_tree_add_text(fv_tree, tvb, offset, sizeof(flags_and_ver), "%s",
313 decode_boolean_bitfield(flags_and_ver, GH_P_A, nbits,
314 "Acknowledgment number", "No acknowledgment number"));
315 proto_tree_add_text(fv_tree, tvb, offset, sizeof(flags_and_ver), "%s",
316 decode_numeric_bitfield(flags_and_ver, GH_P_FLAGS, nbits,
320 proto_tree_add_text(fv_tree, tvb, offset, sizeof(flags_and_ver), "%s",
321 decode_numeric_bitfield(flags_and_ver, GH_R_FLAGS, nbits,
325 proto_tree_add_text(fv_tree, tvb, offset, sizeof(flags_and_ver), "%s",
326 decode_numeric_bitfield(flags_and_ver, GH_B_VER, nbits,
331 dissect_gre_wccp2_redirect_header(tvbuff_t *tvb, int offset, proto_tree *tree)
334 proto_tree * rh_tree;
337 ti = proto_tree_add_text(tree, tvb, offset, 4, "Redirect header");
338 rh_tree = proto_item_add_subtree(ti, ett_gre_wccp2_redirect_header);
340 rh_flags = tvb_get_guint8(tvb, offset);
341 proto_tree_add_text(rh_tree, tvb, offset, 1, "%s",
342 decode_boolean_bitfield(rh_flags, 0x80, 8,
343 "Dynamic service", "Well-known service"));
344 proto_tree_add_text(rh_tree, tvb, offset, 1, "%s",
345 decode_boolean_bitfield(rh_flags, 0x40, 8,
346 "Alternative bucket used", "Alternative bucket not used"));
348 proto_tree_add_text(rh_tree, tvb, offset + 1, 1, "Service ID: %s",
349 val_to_str(tvb_get_guint8(tvb, offset + 1), service_id_vals, "Unknown (0x%02X)"));
351 proto_tree_add_text(rh_tree, tvb, offset + 2, 1, "Alternative bucket index: %u",
352 tvb_get_guint8(tvb, offset + 2));
353 proto_tree_add_text(rh_tree, tvb, offset + 3, 1, "Primary bucket index: %u",
354 tvb_get_guint8(tvb, offset + 3));
358 proto_register_gre(void)
360 static hf_register_info hf[] = {
362 { "Protocol Type", "gre.proto", FT_UINT16, BASE_HEX, VALS(typevals), 0x0,
363 "The protocol that is GRE encapsulated", HFILL }
366 static gint *ett[] = {
369 &ett_gre_wccp2_redirect_header,
372 proto_gre = proto_register_protocol("Generic Routing Encapsulation",
374 proto_register_field_array(proto_gre, hf, array_length(hf));
375 proto_register_subtree_array(ett, array_length(ett));
377 /* subdissector code */
378 gre_dissector_table = register_dissector_table("gre.proto",
379 "GRE protocol type", FT_UINT16, BASE_HEX);
383 proto_reg_handoff_gre(void)
385 dissector_handle_t gre_handle;
387 gre_handle = create_dissector_handle(dissect_gre, proto_gre);
388 dissector_add("ip.proto", IP_PROTO_GRE, gre_handle);
389 data_handle = find_dissector("data");