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On at least one capture, the PIM checksum appears to be correct, so 

add code to check it - I've no idea what's going on with the other
captures where it's not correct, but those captures have a different
(and apparently incorrect) checksum for packets with the *exact same
contents* (other than the checksum) as the PIM packet in the capture
where the checksum is correct, so perhaps those packets actually had bad
checksums.

svn path=/trunk/; revision=3004
This commit is contained in:
Guy Harris 2001-02-08 08:38:58 +00:00
parent d59ab05745
commit 6742f8bec9
1 changed files with 52 additions and 16 deletions
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68
packet-pim.c
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@ -2,7 +2,7 @@
* Routines for PIM disassembly
* (c) Copyright Jun-ichiro itojun Hagino <itojun@itojun.org>
*
* $Id: packet-pim.c,v 1.23 2001/01/22 03:33:45 guy Exp $
* $Id: packet-pim.c,v 1.24 2001/02/08 08:38:58 guy Exp $
*
* Ethereal - Network traffic analyzer
* By Gerald Combs <gerald@zing.org>
@ -46,6 +46,7 @@
#include "packet.h"
#include "packet-ip.h"
#include "packet-ipv6.h"
#include "in_cksum.h"
#define PIM_TYPE(x) ((x) & 0x0f)
#define PIM_VER(x) (((x) & 0xf0) >> 4)
@ -188,7 +189,9 @@ static void
dissect_pim(tvbuff_t *tvb, packet_info *pinfo, proto_tree *tree) {
int offset = 0;
guint8 pim_typever;
guint16 pim_cksum;
guint length, pim_length;
guint16 pim_cksum, computed_cksum;
vec_t cksum_vec[1];
static const value_string type1vals[] = {
{ 0, "Query" },
{ 1, "Register" },
@ -256,21 +259,54 @@ dissect_pim(tvbuff_t *tvb, packet_info *pinfo, proto_tree *tree) {
PIM_TYPE(pim_typever),
"Type: %s (%u)", typestr, PIM_TYPE(pim_typever));
/*
* XXX - RFC 2362 says that this is "the 16-bit one's complement
* of the one's complement sum of the entire PIM message,
* (excluding the data portion in the Register message). For
* computing the checksum, the checksum field is zeroed."
*
* As I read that, it translates as "this is the IP checksum
* of everything in the PIM packet except for the data portion
* in the Register message" - but, in at least one IPv6
* capture, that doesn't appear to be the case; perhaps it's
* different for PIM-over-IPv6.
*/
pim_cksum = tvb_get_ntohs(tvb, offset + 2);
proto_tree_add_uint(pim_tree, hf_pim_cksum, tvb,
offset + 2, 2, pim_cksum);
length = tvb_length(tvb);
if (PIM_VER(pim_typever) == 2) {
/*
* Well, it's PIM v2, so we can check whether this is a Register
* mesage, and thus can figure out how much to checksum.
*/
if (PIM_TYPE(pim_typever) == 1) {
/*
* Register message - the PIM header is 8 bytes long.
*/
pim_length = 8;
} else {
/*
* Other message - checksum the entire packet.
*/
pim_length = tvb_reported_length(tvb);
}
} else {
/*
* We don't know what type of message this is, so say that
* the length is 0, to force it not to be checksummed.
*/
pim_length = 0;
}
if (!pinfo->fragmented && length >= pim_length) {
/*
* 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, pim_length);
cksum_vec[0].len = pim_length;
computed_cksum = in_cksum(&cksum_vec[0], 1);
if (computed_cksum == 0) {
proto_tree_add_uint_format(pim_tree, hf_pim_cksum, tvb,
offset + 2, 2, pim_cksum,
"Checksum: 0x%04x (correct)",
pim_cksum);
} else {
proto_tree_add_uint_format(pim_tree, hf_pim_cksum, tvb,
offset + 2, 2, pim_cksum,
"Checksum: 0x%04x (incorrect, should be 0x%04x)",
pim_cksum, in_cksum_shouldbe(pim_cksum, computed_cksum));
}
} else {
proto_tree_add_uint(pim_tree, hf_pim_cksum, tvb,
offset + 2, 2, pim_cksum);
}
offset += 4;