ECMP is not flow-based for forwarded traffic >5.4.x

[Lars Ekman G]

Hi,

>From somewhere between 5.4.35 and 5.5.7 flow-based ECMP for forwarded traffic has stopped working.
The fault is still present in 5.6.4 and t is present both for ipv4 and ipv6.

Ecmp is setup with (or corresponding ipv6);

        ip route add 10.0.0.0/24 \
                nexthop via 192.168.1.1 \
                nexthop via 192.168.1.2 \
                nexthop via 192.168.1.3 \
                nexthop via 192.168.1.4

Packets are routed flow-based from the machine where this route is set (local works), but traffic forwarded through this
machine is distributed packet-based. This is used as a primitive load-balancer and TCP connections fails.

Forwarded traffic is distributed flow-based in 5.4.35 and everything works. I might have missed some new config
setting in 5.5.x. Sysctls;

# cat /proc/sys/net/ipv4/fib_multipath_hash_policy
1
# cat /proc/sys/net/ipv6/fib_multipath_hash_policy
0


Best Regards,
Lars Ekman