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| author | Guy Harris <guy@alum.mit.edu> | 2000-12-15 00:03:09 +0000 |
|---|---|---|
| committer | Guy Harris <guy@alum.mit.edu> | 2000-12-15 00:03:09 +0000 |
| commit | ada46b7434203bbe2891beecddeb13310e1bc5fb (patch) | |
| tree | ef536d0b2fe5a8302ad32d66ece553d03946205e /packet-gre.c | |
| parent | 0f68b651b12772ec1a18ea24b43d55dfef2afe6d (diff) | |
| download | wireshark-ada46b7434203bbe2891beecddeb13310e1bc5fb.tar.gz wireshark-ada46b7434203bbe2891beecddeb13310e1bc5fb.tar.bz2 wireshark-ada46b7434203bbe2891beecddeb13310e1bc5fb.zip | |
Check the checksum on GRE packets, if possible and if the Checksum
Present flag is set.
svn path=/trunk/; revision=2761
Diffstat (limited to 'packet-gre.c')
| -rw-r--r-- | packet-gre.c | 39 |
1 files changed, 32 insertions, 7 deletions
diff --git a/packet-gre.c b/packet-gre.c index f49951b5df..5271720cf2 100644 --- a/packet-gre.c +++ b/packet-gre.c @@ -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) { |