Support multicast at the KNI interfaces

[AltraMayor]

Some ASes would prefer to run OSPF and BGP on BIRD on Gatekeeper servers, and OSPF relies on multicast.

Here's the log of two of OSPF's packets:

[2022-11-26 14:38:27] GK/5: acl: a packet failed to match any ACL rules, the whole packet is dumped below:
dump mbuf at 0x21ffd49b00, iova=0x21ffd49b98, buf_len=2176
pkt_len=62, ol_flags=0x182, nb_segs=1, port=0, ptype=0x290
segment at 0x21ffd49b00, data=0x21ffd49c18, len=62, off=128, refcnt=1
Dump data at [0x21ffd49c18], len=62
00000000: 6C B3 11 21 7E 84 60 12 3C 41 F9 42 08 00 45 00 | l..!~.`.<A.B..E.
00000010: 00 30 04 06 00 00 FF 11 A1 B3 0A 00 01 01 0A 00 | .0..............
00000020: 01 03 75 E3 75 E3 00 1C FD D0 00 00 00 14 00 00 | ..u.u...........
00000030: 00 06 00 00 00 01 00 00 00 00 00 00 00 00 | ..............
[2022-11-26 14:38:30] GK/5: acl: a packet failed to match any ACL rules, the whole packet is dumped below:
dump mbuf at 0x21ffb1e8c0, iova=0x21ffb1e958, buf_len=2176
pkt_len=62, ol_flags=0x182, nb_segs=1, port=1, ptype=0x290
segment at 0x21ffb1e8c0, data=0x21ffb1e9d8, len=62, off=128, refcnt=1
Dump data at [0x21ffb1e9d8], len=62
00000000: 6C B3 11 21 7E 86 98 44 CE F8 79 D2 08 00 45 00 | l..!~..D..y...E.
00000010: 00 30 04 06 00 00 FF 11 8B 98 0A 0B 0C 08 0A 0B | .0..............
00000020: 0C 01 75 E3 75 E3 00 1C E7 B5 00 00 00 14 00 00 | ..u.u...........
00000030: 00 06 00 00 00 01 00 00 00 00 00 00 00 00 | ..............

Reference links:

Intel Ethernet Controller X710/XXV710/XL710 Adapters Dynamic Device Personalization: IPv4 Multicast

Open Shortest Path First (OSPF) protocol States