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Check the checksum on GRE packets, if possible and if the Checksum 

Present flag is set.

svn path=/trunk/; revision=2761
This commit is contained in:
Guy Harris 2000-12-15 00:03:09 +00:00
parent 0f68b651b1
commit ada46b7434
1 changed files with 32 additions and 7 deletions
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39
packet-gre.c
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@ -2,7 +2,7 @@
* Routines for the Generic Routing Encapsulation (GRE) protocol
* Brad Robel-Forrest <brad.robel-forrest@watchguard.com>
*
* $Id: packet-gre.c,v 1.31 2000/11/29 07:42:35 guy Exp $
* $Id: packet-gre.c,v 1.32 2000/12/15 00:03:09 guy Exp $
*
* Ethereal - Network traffic analyzer
* By Gerald Combs <gerald@zing.org>
@ -40,6 +40,7 @@
#include "packet-ip.h"
#include "packet-ipx.h"
#include "packet-wccp.h"
#include "in_cksum.h"
static int proto_gre = -1;
static int hf_gre_proto = -1;
@ -98,12 +99,12 @@ dissect_gre(tvbuff_t *tvb, packet_info *pinfo, proto_tree *tree)
if (check_col(pinfo->fd, COL_PROTOCOL))
col_set_str(pinfo->fd, COL_PROTOCOL, "GRE");
if (check_col(pinfo->fd, COL_INFO)) {
col_add_fstr(pinfo->fd, COL_INFO, "Encapsulated %s",
val_to_str(type, typevals, "0x%04X (unknown)"));
}
if (tree) {
gboolean is_ppp = FALSE;
gboolean is_wccp2 = FALSE;
@ -147,10 +148,34 @@ dissect_gre(tvbuff_t *tvb, packet_info *pinfo, proto_tree *tree)
offset += sizeof(type);
if (flags_and_ver & GH_B_C || flags_and_ver & GH_B_R) {
guint16 checksum = tvb_get_ntohs(tvb, offset);
proto_tree_add_text(gre_tree, tvb, offset, sizeof(checksum),
"Checksum: %u", checksum);
offset += sizeof(checksum);
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, sizeof(cksum),
"Checksum: 0x%04x (correct)", cksum);
} else {
proto_tree_add_text(gre_tree, tvb, offset, sizeof(cksum),
"Checksum: 0x%04x (incorrect, should be 0x%04x)",
cksum, in_cksum_shouldbe(cksum, computed_cksum));
}
} else {
proto_tree_add_text(gre_tree, tvb, offset, sizeof(cksum),
"Checksum: 0x%04x", cksum);
}
offset += sizeof(cksum);
}
if (flags_and_ver & GH_B_C || flags_and_ver & GH_B_R) {