forked from osmocom/wireshark
Check the checksum on GRE packets, if possible and if the Checksum
Present flag is set. svn path=/trunk/; revision=2761
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parent
0f68b651b1
commit
ada46b7434
35
packet-gre.c
35
packet-gre.c
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@ -2,7 +2,7 @@
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* Routines for the Generic Routing Encapsulation (GRE) protocol
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* Brad Robel-Forrest <brad.robel-forrest@watchguard.com>
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*
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* $Id: packet-gre.c,v 1.31 2000/11/29 07:42:35 guy Exp $
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* $Id: packet-gre.c,v 1.32 2000/12/15 00:03:09 guy Exp $
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*
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* Ethereal - Network traffic analyzer
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* By Gerald Combs <gerald@zing.org>
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@ -40,6 +40,7 @@
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#include "packet-ip.h"
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#include "packet-ipx.h"
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#include "packet-wccp.h"
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#include "in_cksum.h"
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static int proto_gre = -1;
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static int hf_gre_proto = -1;
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@ -147,10 +148,34 @@ dissect_gre(tvbuff_t *tvb, packet_info *pinfo, proto_tree *tree)
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offset += sizeof(type);
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if (flags_and_ver & GH_B_C || flags_and_ver & GH_B_R) {
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guint16 checksum = tvb_get_ntohs(tvb, offset);
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proto_tree_add_text(gre_tree, tvb, offset, sizeof(checksum),
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"Checksum: %u", checksum);
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offset += sizeof(checksum);
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guint length, reported_length;
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vec_t cksum_vec[1];
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guint16 cksum, computed_cksum;
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cksum = tvb_get_ntohs(tvb, offset);
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length = tvb_length(tvb);
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reported_length = tvb_reported_length(tvb);
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if ((flags_and_ver & GH_B_C) && !pinfo->fragmented
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&& length >= reported_length) {
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/* The Checksum Present bit is set, and the packet isn't part of a
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fragmented datagram and isn't truncated, so we can checksum it. */
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cksum_vec[0].ptr = tvb_get_ptr(tvb, 0, reported_length);
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cksum_vec[0].len = reported_length;
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computed_cksum = in_cksum(cksum_vec, 1);
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if (computed_cksum == 0) {
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proto_tree_add_text(gre_tree, tvb, offset, sizeof(cksum),
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"Checksum: 0x%04x (correct)", cksum);
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} else {
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proto_tree_add_text(gre_tree, tvb, offset, sizeof(cksum),
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"Checksum: 0x%04x (incorrect, should be 0x%04x)",
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cksum, in_cksum_shouldbe(cksum, computed_cksum));
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}
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} else {
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proto_tree_add_text(gre_tree, tvb, offset, sizeof(cksum),
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"Checksum: 0x%04x", cksum);
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}
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offset += sizeof(cksum);
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}
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if (flags_and_ver & GH_B_C || flags_and_ver & GH_B_R) {
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