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wireshark/packet-gre.c

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/* packet-gre.c
* Routines for the Generic Routing Encapsulation (GRE) protocol
* Brad Robel-Forrest <brad.robel-forrest@watchguard.com>
*
* $Id: packet-gre.c,v 1.55 2004/01/29 03:51:25 guy Exp $
*
* Ethereal - Network traffic analyzer
* By Gerald Combs <gerald@ethereal.com>
* Copyright 1998 Gerald Combs
*
* This program is free software; you can redistribute it and/or
* modify it under the terms of the GNU General Public License
* as published by the Free Software Foundation; either version 2
* of the License, or (at your option) any later version.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program; if not, write to the Free Software
* Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
*/
#ifdef HAVE_CONFIG_H
# include "config.h"
#endif
#include <glib.h>
#include <epan/packet.h>
#include "packet-wccp.h"
#include "in_cksum.h"
#include "etypes.h"
#include "greproto.h"
#include "ipproto.h"
#include "llcsaps.h"
/*
* See RFC 1701 "Generic Routing Encapsulation (GRE)", RFC 1702
* "Generic Routing Encapsulation over IPv4 networks", RFC 2637
* "Point-to-Point Tunneling Protocol (PPTP)", RFC 2784 "Generic
* Routing Encapsulation (GRE)", and RFC 2890 "Key and Sequence
* Number Extensions to GRE".
*/
static int proto_gre = -1;
static int hf_gre_proto = -1;
static gint ett_gre = -1;
static gint ett_gre_flags = -1;
static gint ett_gre_wccp2_redirect_header = -1;
static dissector_table_t gre_dissector_table;
static dissector_handle_t data_handle;
/* bit positions for flags in header */
#define GH_B_C 0x8000
#define GH_B_R 0x4000
#define GH_B_K 0x2000
#define GH_B_S 0x1000
#define GH_B_s 0x0800
#define GH_B_RECUR 0x0700
#define GH_P_A 0x0080 /* only in special PPTPized GRE header */
#define GH_P_FLAGS 0x0078 /* only in special PPTPized GRE header */
#define GH_R_FLAGS 0x00F8
#define GH_B_VER 0x0007
static void add_flags_and_ver(proto_tree *, guint16, tvbuff_t *, int, int);
static void dissect_gre_wccp2_redirect_header(tvbuff_t *, int, proto_tree *);
static const value_string typevals[] = {
{ ETHERTYPE_PPP, "PPP" },
{ ETHERTYPE_IP, "IP" },
{ SAP_OSINL5, "OSI"},
{ GRE_WCCP, "WCCP"},
{ ETHERTYPE_IPX, "IPX"},
{ ETHERTYPE_ETHBRIDGE, "Transparent Ethernet bridging" },
{ GRE_FR, "Frame Relay"},
{ ETHERTYPE_IPv6, "IPv6" },
{ 0, NULL }
};
static void
dissect_gre(tvbuff_t *tvb, packet_info *pinfo, proto_tree *tree)
{
int offset = 0;
guint16 flags_and_ver;
guint16 type;
gboolean is_ppp = FALSE;
gboolean is_wccp2 = FALSE;
guint len = 4;
proto_item *ti;
proto_tree *gre_tree = NULL;
guint16 sre_af;
guint8 sre_length;
tvbuff_t *next_tvb;
flags_and_ver = tvb_get_ntohs(tvb, offset);
type = tvb_get_ntohs(tvb, offset + sizeof(flags_and_ver));
if (check_col(pinfo->cinfo, COL_PROTOCOL))
col_set_str(pinfo->cinfo, COL_PROTOCOL, "GRE");
if (check_col(pinfo->cinfo, COL_INFO)) {
col_add_fstr(pinfo->cinfo, COL_INFO, "Encapsulated %s",
val_to_str(type, typevals, "0x%04X (unknown)"));
}
if (flags_and_ver & GH_B_C || flags_and_ver & GH_B_R)
len += 4;
if (flags_and_ver & GH_B_K)
len += 4;
if (flags_and_ver & GH_B_S)
len += 4;
switch (type) {
case ETHERTYPE_PPP:
if (flags_and_ver & GH_P_A)
len += 4;
is_ppp = TRUE;
break;
case GRE_WCCP:
/* WCCP2 puts an extra 4 octets into the header, but uses the same
encapsulation type; if it looks as if the first octet of the packet
isn't the beginning of an IPv4 header, assume it's WCCP2. */
if ((tvb_get_guint8(tvb, offset + sizeof(flags_and_ver) + sizeof(type)) & 0xF0) != 0x40) {
len += 4;
is_wccp2 = TRUE;
}
break;
}
if (tree) {
ti = proto_tree_add_protocol_format(tree, proto_gre, tvb, offset, len,
"Generic Routing Encapsulation (%s)",
val_to_str(type, typevals, "0x%04X - unknown"));
gre_tree = proto_item_add_subtree(ti, ett_gre);
add_flags_and_ver(gre_tree, flags_and_ver, tvb, offset, is_ppp);
}
offset += sizeof(flags_and_ver);
if (tree) {
proto_tree_add_uint(gre_tree, hf_gre_proto, tvb, offset, sizeof(type), type);
}
offset += sizeof(type);
if (flags_and_ver & GH_B_C || flags_and_ver & GH_B_R) {
if (tree) {
guint length, reported_length;
vec_t cksum_vec[1];
guint16 cksum, computed_cksum;
cksum = tvb_get_ntohs(tvb, offset);
length = tvb_length(tvb);
reported_length = tvb_reported_length(tvb);
if ((flags_and_ver & GH_B_C) && !pinfo->fragmented
&& length >= reported_length) {
/* The Checksum Present bit is set, and the packet isn't part of a
fragmented datagram and isn't truncated, so we can checksum it. */
cksum_vec[0].ptr = tvb_get_ptr(tvb, 0, reported_length);
cksum_vec[0].len = reported_length;
computed_cksum = in_cksum(cksum_vec, 1);
if (computed_cksum == 0) {
proto_tree_add_text(gre_tree, tvb, offset, 2,
"Checksum: 0x%04x (correct)", cksum);
} else {
proto_tree_add_text(gre_tree, tvb, offset, 2,
"Checksum: 0x%04x (incorrect, should be 0x%04x)",
cksum, in_cksum_shouldbe(cksum, computed_cksum));
}
} else {
proto_tree_add_text(gre_tree, tvb, offset, 2,
"Checksum: 0x%04x", cksum);
}
}
offset += 2;
}
if (flags_and_ver & GH_B_C || flags_and_ver & GH_B_R) {
if (tree) {
proto_tree_add_text(gre_tree, tvb, offset, 2,
"Offset: %u", tvb_get_ntohs(tvb, offset));
}
offset += 2;
}
if (flags_and_ver & GH_B_K) {
if (is_ppp) {
if (tree) {
proto_tree_add_text(gre_tree, tvb, offset, 2,
"Payload length: %u", tvb_get_ntohs(tvb, offset));
}
offset += 2;
if (tree) {
proto_tree_add_text(gre_tree, tvb, offset, 2,
"Call ID: %u", tvb_get_ntohs(tvb, offset));
}
offset += 2;
}
else {
if (tree) {
proto_tree_add_text(gre_tree, tvb, offset, 4,
"Key: %u", tvb_get_ntohl(tvb, offset));
}
offset += 4;
}
}
if (flags_and_ver & GH_B_S) {
if (tree) {
proto_tree_add_text(gre_tree, tvb, offset, 4,
"Sequence number: %u", tvb_get_ntohl(tvb, offset));
}
offset += 4;
}
if (is_ppp && flags_and_ver & GH_P_A) {
if (tree) {
proto_tree_add_text(gre_tree, tvb, offset, 4,
"Acknowledgement number: %u", tvb_get_ntohl(tvb, offset));
}
offset += 4;
}
if (flags_and_ver & GH_B_R) {
for (;;) {
sre_af = tvb_get_ntohs(tvb, offset);
if (tree) {
proto_tree_add_text(gre_tree, tvb, offset, sizeof(guint16),
"Address family: %u", sre_af);
}
offset += sizeof(guint16);
if (tree) {
proto_tree_add_text(gre_tree, tvb, offset, 1,
"SRE offset: %u", tvb_get_guint8(tvb, offset));
}
offset += sizeof(guint8);
sre_length = tvb_get_guint8(tvb, offset);
if (tree) {
proto_tree_add_text(gre_tree, tvb, offset, sizeof(guint8),
"SRE length: %u", sre_length);
}
offset += sizeof(guint8);
if (sre_af == 0 && sre_length == 0)
break;
offset += sre_length;
}
}
if (type == GRE_WCCP) {
if (is_wccp2) {
if (tree)
dissect_gre_wccp2_redirect_header(tvb, offset, gre_tree);
offset += 4;
}
}
/* If the S bit is not set, this packet might not have a payload, so
check whether there's any data left, first.
XXX - the S bit isn't in RFC 2784, which deprecates that bit
and some other bits in RFC 1701 and says that they should be
zero for RFC 2784-compliant GRE; as such, the absence of the
S bit doesn't necessarily mean there's no payload. */
if (!(flags_and_ver & GH_B_S)) {
if (tvb_reported_length_remaining(tvb, offset) <= 0)
return; /* no payload */
}
next_tvb = tvb_new_subset(tvb, offset, -1, -1);
if (!dissector_try_port(gre_dissector_table, type, next_tvb, pinfo, tree))
call_dissector(data_handle,next_tvb, pinfo, gre_tree);
}
static void
add_flags_and_ver(proto_tree *tree, guint16 flags_and_ver, tvbuff_t *tvb,
int offset, int is_ppp)
{
proto_item * ti;
proto_tree * fv_tree;
int nbits = sizeof(flags_and_ver) * 8;
ti = proto_tree_add_text(tree, tvb, offset, 2,
"Flags and version: %#04x", flags_and_ver);
fv_tree = proto_item_add_subtree(ti, ett_gre_flags);
proto_tree_add_text(fv_tree, tvb, offset, sizeof(flags_and_ver), "%s",
decode_boolean_bitfield(flags_and_ver, GH_B_C, nbits,
"Checksum", "No checksum"));
proto_tree_add_text(fv_tree, tvb, offset, sizeof(flags_and_ver), "%s",
decode_boolean_bitfield(flags_and_ver, GH_B_R, nbits,
"Routing", "No routing"));
proto_tree_add_text(fv_tree, tvb, offset, sizeof(flags_and_ver), "%s",
decode_boolean_bitfield(flags_and_ver, GH_B_K, nbits,
"Key", "No key"));
proto_tree_add_text(fv_tree, tvb, offset, sizeof(flags_and_ver), "%s",
decode_boolean_bitfield(flags_and_ver, GH_B_S, nbits,
"Sequence number", "No sequence number"));
proto_tree_add_text(fv_tree, tvb, offset, sizeof(flags_and_ver), "%s",
decode_boolean_bitfield(flags_and_ver, GH_B_s, nbits,
"Strict source route", "No strict source route"));
proto_tree_add_text(fv_tree, tvb, offset, sizeof(flags_and_ver), "%s",
decode_numeric_bitfield(flags_and_ver, GH_B_RECUR, nbits,
"Recursion control: %u"));
if (is_ppp) {
proto_tree_add_text(fv_tree, tvb, offset, sizeof(flags_and_ver), "%s",
decode_boolean_bitfield(flags_and_ver, GH_P_A, nbits,
"Acknowledgment number", "No acknowledgment number"));
proto_tree_add_text(fv_tree, tvb, offset, sizeof(flags_and_ver), "%s",
decode_numeric_bitfield(flags_and_ver, GH_P_FLAGS, nbits,
"Flags: %u"));
}
else {
proto_tree_add_text(fv_tree, tvb, offset, sizeof(flags_and_ver), "%s",
decode_numeric_bitfield(flags_and_ver, GH_R_FLAGS, nbits,
"Flags: %u"));
}
proto_tree_add_text(fv_tree, tvb, offset, sizeof(flags_and_ver), "%s",
decode_numeric_bitfield(flags_and_ver, GH_B_VER, nbits,
"Version: %u"));
}
static void
dissect_gre_wccp2_redirect_header(tvbuff_t *tvb, int offset, proto_tree *tree)
{
proto_item * ti;
proto_tree * rh_tree;
guint8 rh_flags;
ti = proto_tree_add_text(tree, tvb, offset, 4, "Redirect header");
rh_tree = proto_item_add_subtree(ti, ett_gre_wccp2_redirect_header);
rh_flags = tvb_get_guint8(tvb, offset);
proto_tree_add_text(rh_tree, tvb, offset, 1, "%s",
decode_boolean_bitfield(rh_flags, 0x80, 8,
"Dynamic service", "Well-known service"));
proto_tree_add_text(rh_tree, tvb, offset, 1, "%s",
decode_boolean_bitfield(rh_flags, 0x40, 8,
"Alternative bucket used", "Alternative bucket not used"));
proto_tree_add_text(rh_tree, tvb, offset + 1, 1, "Service ID: %s",
val_to_str(tvb_get_guint8(tvb, offset + 1), service_id_vals, "Unknown (0x%02X)"));
if (rh_flags & 0x40)
proto_tree_add_text(rh_tree, tvb, offset + 2, 1, "Alternative bucket index: %u",
tvb_get_guint8(tvb, offset + 2));
proto_tree_add_text(rh_tree, tvb, offset + 3, 1, "Primary bucket index: %u",
tvb_get_guint8(tvb, offset + 3));
}
void
proto_register_gre(void)
{
static hf_register_info hf[] = {
{ &hf_gre_proto,
{ "Protocol Type", "gre.proto", FT_UINT16, BASE_HEX, VALS(typevals), 0x0,
"The protocol that is GRE encapsulated", HFILL }
},
};
static gint *ett[] = {
&ett_gre,
&ett_gre_flags,
&ett_gre_wccp2_redirect_header,
};
proto_gre = proto_register_protocol("Generic Routing Encapsulation",
"GRE", "gre");
proto_register_field_array(proto_gre, hf, array_length(hf));
proto_register_subtree_array(ett, array_length(ett));
/* subdissector code */
gre_dissector_table = register_dissector_table("gre.proto",
"GRE protocol type", FT_UINT16, BASE_HEX);
}
void
proto_reg_handoff_gre(void)
{
dissector_handle_t gre_handle;
gre_handle = create_dissector_handle(dissect_gre, proto_gre);
dissector_add("ip.proto", IP_PROTO_GRE, gre_handle);
data_handle = find_dissector("data");
}
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