conntrack thinks that ICMPv6 Echo reply to ICMPv6 Echo request sent to IPv6 multicast address is INVALID

Hi all,

1) I have two virtual machines with interfaces on the same link:
A) fe80::5054:ff:fe09:e0b9/64
B) fe80::5054:ff:fe80:d951/64

2) I set up IPv6 packet filter on A with ip6tables:

# ip6tables -F
# ip6tables -A INPUT -m conntrack --ctstate INVALID -j REJECT --reject-with icmp6-adm-prohibited
# ip6tables -A INPUT -p ipv6-icmp -j ACCEPT
# ip6tables -A INPUT -j REJECT --reject-with icmp6-adm-prohibited

3) ping6 B from A:

# ping6 -I eth2 fe80::5054:ff:fe80:d951
PING fe80::5054:ff:fe80:d951(fe80::5054:ff:fe80:d951) from
fe80::5054:ff:fe09:e0b9 eth2: 56 data bytes
64 bytes from fe80::5054:ff:fe80:d951: icmp_seq=1 ttl=64 time=0.265 ms
<OK>

4) ping6 'all nodes' from A:

# ping6 -I eth2 ff02::1
PING ff02::1(ff02::1) from fe80::5054:ff:fe09:e0b9 eth2: 56 data bytes
<no response, reply is rejected>

5) remove the first line from ip6tables

# ip6tables -D INPUT 1

6) ping6 'all nodes' from A:

# ping6 -I eth2 ff02::1
PING ff02::1(ff02::1) from fe80::5054:ff:fe09:e0b9 eth2: 56 data bytes
64 bytes from fe80::5054:ff:fe09:e0b9: icmp_seq=1 ttl=64 time=0.072 ms
64 bytes from fe80::5054:ff:fe80:d951: icmp_seq=1 ttl=64 time=0.318 ms (DUP!)
<OK>

I see this with kernels 2.6.32 and 3.3.0.
Is it a known bug or my misunderstanding ?

thanks
--
Jiri

I think that your *problem* is...

When you ping to all nodes, the target address is one, but the response is other (the same occur in ipv4 when you ping multcast address). The conntrack table cant map the real nodes in this type of request. So, to conntrack view its *invalid*!

INHO, to do this i think that you need allow icmp for individual address before REJECT.

2012/3/23 Jiri Popelka <[email protected]>: