ipv4 regression in 2.6.31 ?

[Stephan von Krawczynski <skraw@ithnet.com>]

Hello all,

today we experienced some sort of regression in 2.6.31 ipv4 implementation, or
at least some incompatibility with former 2.6.30.X kernels.

We have the following situation:

                                       ---------- vlan1@eth0 192.168.2.1/24
                                      /
host A 192.168.1.1/24 eth0  -------<router>            host B
                                      \
                                       ---------- eth1 192.168.3.1/24


Now, if you route 192.168.1.0/24 via interface vlan1@eth0 on host B and let
host A ping 192.168.2.1 everything works. But if you route 192.168.1.0/24 via
interface eth1 on host B and let host A ping 192.168.2.1 you get no reply.
With tcpdump we see the icmp packets arrive at vlan1@eth0, but no icmp echo
reply being generated neither on vlan1 nor eth1.
Kernels 2.6.30.X and below do not show this behaviour.
Is this intended? Do we need to reconfigure something to restore the old
behaviour?

-- 
Regards,
Stephan