Historic Notes - RIPE-NCC/bgpdump GitHub Wiki

You might note that there are some strange loops in the code handling TABLE_DUMP_V2. The reason for this is that for one prefix, there is always only one TABLE_DUMP_V2 entry, possibly with multiple peers and atrributes. To keep output consistent, the code loops through every peer/attribute set and prints the prefix every time. As the code around the type-specific parsing usually prints out timestamps and newlines to seperate entries, this is done in these small loops too.

Also, TABLE_DUMP_V2 was not finished yet when it was added to libbgpdump. Libbgpdump supports the format as defined in draft-ietf-grow-mrt-04, with the following exceptions: - INDEX_TABLE is named PEER_INDEX_TABLE in the code - BGP4MP_STATE_CHANGE_AS4 exists, it's like BGP4MP_STATE_CHANGE with a 4-byte AS field. Note that it's subtype is mentioned in section 5.9. - RIB_GENERIC and the multicast RIBs are not supported. IPv4 and IPv6 unicast prefixes will only be read from RIB_IPV4_UNICAST and RIB_IPV6_UNICAST entries.

As RIB_GENERIC may be supported in later versions and may then also contain IPv4 or IPv6 unicast prefixes, code using the library should check the address family by reading the contents of: entry->body.mrtd_table_dump_v2_prefix.afi for AFI_IP or AFI_IP6 and *NOT* checking the contents of entry->subtype for BGPDUMP_SUBTYPE_TABLE_DUMP_V2_RIB_IPV4_UNICAST etc.

libbgpdump v1.3 and above support IPv6. Both address types are usually stored the BGPDUMP_IP_ADDRESS data structure.

IPv6 announcements and withdrawals aren't stored directly in the update data structures like their IPv4 counterparts, they are stored in a separate struct mp_info. Two convenient macros, MP_IPV6_ANNOUNCE() and MP_IPV6_WITHDRAW(), are provided to get them out.

So if for IPv4 prefixes you did something like:

    for (i = 0; i < entry->body.zebra_message.announce_count; i++) {
        do_something_with_prefix(entry->body.zebra_message.announce[i]);
    }

for IPv6 prefixes you would do this:

    struct mp_nlri *v6_announce;
    if(entry->attr->mp_info &&
       (v6_announce = MP_IPV6_ANNOUNCE(entry->attr->mp_info)) != NULL) {
        for (i = 0; i < v6_announce->prefix_count; i++) {
            do_something_with_prefix(v6_announce->nlri[i]);
        }
    }

for withdrawals, do the same using MP_IPV6_WITHDRAW().