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Check hopcount is correctly incremented by 1 

Extract RFC3315 about hop-count :
20.1.2. Relaying a Message from a Relay Agent

   If the message received by the relay agent is a Relay-forward message
   and the hop-count in the message is greater than or equal to
   HOP_COUNT_LIMIT, the relay agent discards the received message.

   The relay agent copies the source address from the IP datagram in
   which the message was received from the client into the peer-address
   field in the Relay-forward message and sets the hop-count field to
   the value of the hop-count field in the received message incremented
   by 1.

Bug:10449
Change-Id: Ifb94e7c54c0a26714fc543862d4358d3e60c2676
Reviewed-on: https://code.wireshark.org/review/4017
Reviewed-by: Michael Mann <mmann78@netscape.net>
Petri-Dish: Michael Mann <mmann78@netscape.net>
Tested-by: Petri Dish Buildbot <buildbot-no-reply@wireshark.org>
Reviewed-by: Evan Huus <eapache@gmail.com>
This commit is contained in:
Jérôme LAFORGE 2014-09-07 16:35:10 +02:00 committed by Evan Huus
parent cf8f11f678
commit 00a244445d
1 changed files with 16 additions and 6 deletions
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22
epan/dissectors/packet-dhcpv6.c
View File

@ -725,8 +725,14 @@ static value_string_ext eue_capabilities_encoding_ext = VALUE_STRING_EXT_INIT(eu
typedef struct hopcount_info_t {
guint8 hopcount;
proto_item *pi;
gboolean relay_message_previously_detected;
} hopcount_info;
static void
initialize_hopount_info(hopcount_info *hpi) {
memset(hpi, 0, sizeof(hopcount_info));
}
static void
dissect_dhcpv6(tvbuff_t *tvb, packet_info *pinfo, proto_tree *tree,
gboolean downstream, int off, int eoff, hopcount_info hpi);
@ -1927,6 +1933,8 @@ dissect_dhcpv6(tvbuff_t *tvb, packet_info *pinfo, proto_tree *tree,
if ((msgtype == RELAY_FORW) || (msgtype == RELAY_REPLY)) {
const guint8 previous_hopcount = hpi.hopcount;
proto_item *previous_pi = hpi.pi;
if (tree) {
proto_tree_add_item(bp_tree, hf_dhcpv6_msgtype, tvb, off, 1, ENC_BIG_ENDIAN);
hpi.pi = proto_tree_add_item(bp_tree, hf_dhcpv6_hopcount, tvb, off + 1, 1, ENC_BIG_ENDIAN);
@ -1939,6 +1947,11 @@ dissect_dhcpv6(tvbuff_t *tvb, packet_info *pinfo, proto_tree *tree,
if (hpi.hopcount > HOP_COUNT_LIMIT) {
expert_add_info_format(pinfo, hpi.pi, &ei_dhcpv6_error_hopcount, "Hopcount (%d) exceeds the maximum limit HOP_COUNT_LIMIT (%d)", hpi.hopcount, HOP_COUNT_LIMIT);
}
/* Check hopcount is correctly incremented by 1 */
if (hpi.relay_message_previously_detected && hpi.hopcount != previous_hopcount - 1) {
expert_add_info_format(pinfo, previous_pi, &ei_dhcpv6_error_hopcount, "hopcount is not correctly incremented by 1 (expected : %d, actual : %d)", hpi.hopcount + 1, previous_hopcount);
}
hpi.relay_message_previously_detected = TRUE;
tvb_get_ipv6(tvb, off + 2, &in6);
col_append_fstr(pinfo->cinfo, COL_INFO, "L: %s ", ip6_to_str(&in6));
off += 34;
@ -1964,8 +1977,7 @@ static void
dissect_dhcpv6_downstream(tvbuff_t *tvb, packet_info *pinfo, proto_tree *tree)
{
hopcount_info hpi;
hpi.hopcount = 0;
hpi.pi = NULL;
initialize_hopount_info(&hpi);
col_set_str(pinfo->cinfo, COL_PROTOCOL, "DHCPv6");
col_clear(pinfo->cinfo, COL_INFO);
dissect_dhcpv6(tvb, pinfo, tree, TRUE, 0, tvb_reported_length(tvb), hpi);
@ -1975,8 +1987,7 @@ static void
dissect_dhcpv6_upstream(tvbuff_t *tvb, packet_info *pinfo, proto_tree *tree)
{
hopcount_info hpi;
hpi.hopcount = 0;
hpi.pi = NULL;
initialize_hopount_info(&hpi);
col_set_str(pinfo->cinfo, COL_PROTOCOL, "DHCPv6");
col_clear(pinfo->cinfo, COL_INFO);
dissect_dhcpv6(tvb, pinfo, tree, FALSE, 0, tvb_reported_length(tvb), hpi);
@ -1999,8 +2010,7 @@ dissect_dhcpv6_bulk_leasequery_pdu(tvbuff_t *tvb, packet_info *pinfo, proto_tree
guint8 msg_type;
gboolean at_end = FALSE;
hopcount_info hpi;
hpi.hopcount = 0;
hpi.pi = NULL;
initialize_hopount_info(&hpi);
col_set_str(pinfo->cinfo, COL_PROTOCOL, "DHCPv6 BulkLease");
col_clear(pinfo->cinfo, COL_INFO);