diff options
| -rw-r--r-- | epan/dissectors/packet-ip.c | 25 |
1 files changed, 15 insertions, 10 deletions
diff --git a/epan/dissectors/packet-ip.c b/epan/dissectors/packet-ip.c index 3ac36dc8c0..c6e05a6ab3 100644 --- a/epan/dissectors/packet-ip.c +++ b/epan/dissectors/packet-ip.c @@ -382,6 +382,10 @@ static gint ett_icmp_mpls_stack_object = -1; #define is_a_local_network_control_block_addr(addr) \ ((addr & 0xffffff00) == 0xe0000000) +/* Return true if the address is in the 224.0.0.0/4 network block */ +#define is_a_multicast_addr(addr) \ + ((addr & 0xf0000000) == 0xe0000000) + /* * defragmentation of IPv4 */ @@ -1422,19 +1426,20 @@ dissect_ip(tvbuff_t *tvb, packet_info *pinfo, proto_tree *parent_tree) tap_queue_packet(ip_tap, pinfo, iph); - /* If an IP is destined for a IP address in the Local Network Control Block + /* If an IP is destined for an IP address in the Local Network Control Block * (e.g. 224.0.0.0/24), the packet should never be routed and the TTL would - * be expected to be 1. (see RFC 3171) So only flag a low TTL if the - * packet is not destined to a 224.0.0.0/24 address. For packets sent to - * 224.0.0.0/24, flag a TTL greater than 1. + * be expected to be 1. (see RFC 3171) Flag a TTL greater than 1. + * + * Flag a low TTL if the packet is not destined for a multicast address + * (e.g. 224.0.0.0/4). */ - if (!is_a_local_network_control_block_addr(dst32)) { - if(ttl < 5) { - expert_add_info_format(pinfo, ttl_item, PI_SEQUENCE, PI_NOTE, "\"Time To Live\" only %u", ttl); + if (is_a_local_network_control_block_addr(dst32)) { + if (ttl != 1) { + expert_add_info_format(pinfo, ttl_item, PI_SEQUENCE, PI_NOTE, + "\"Time To Live\" > 1 for a packet sent to the Local Network Control Block (see RFC 3171)"); } - } else if(ttl > 1) { - expert_add_info_format(pinfo, ttl_item, PI_SEQUENCE, PI_NOTE, - "\"Time To Live\" > 1 for a packet sent to the Local Network Control Block (see RFC 3171)"); + } else if (!is_a_multicast_addr(dst32) && ttl < 5) { + expert_add_info_format(pinfo, ttl_item, PI_SEQUENCE, PI_NOTE, "\"Time To Live\" only %u", ttl); } if (tree) { |