Re: [PATCH net] ipv4: reset fnhe_mtu_locked after cache route flushed

[David Miller <davem@davemloft.net>]

From: Hangbin Liu <liuhangbin@gmail.com>
Date: Wed,  9 May 2018 18:06:44 +0800

> After route cache is flushed via ipv4_sysctl_rtcache_flush(), we forget
> to reset fnhe_mtu_locked in rt_bind_exception(). When pmtu is updated
> in __ip_rt_update_pmtu(), it will return directly since the pmtu is
> still locked. e.g.
> 
> + ip netns exec client ping 10.10.1.1 -c 1 -s 1400 -M do
> PING 10.10.1.1 (10.10.1.1) 1400(1428) bytes of data.
> From 10.10.0.254 icmp_seq=1 Frag needed and DF set (mtu = 0)
> 
> --- 10.10.1.1 ping statistics ---
> 1 packets transmitted, 0 received, +1 errors, 100% packet loss, time 0ms
> 
> + ip netns exec client ip route get 10.10.1.1
> 10.10.1.1 via 10.10.0.254 dev veth0_c src 10.10.0.1 uid 0
>     cache expires 599sec mtu lock 552
> + ip netns exec client ip route flush cache
> + ip netns exec client ip route get 10.10.1.1
> 10.10.1.1 via 10.10.0.254 dev veth0_c src 10.10.0.1 uid 0
>     cache
> + ip netns exec client ping 10.10.1.1 -c 1 -s 1400 -M do
> PING 10.10.1.1 (10.10.1.1) 1400(1428) bytes of data.
> ping: local error: Message too long, mtu=576
> 
> --- 10.10.1.1 ping statistics ---
> 1 packets transmitted, 0 received, +1 errors, 100% packet loss, time 0ms
> 
> + ip netns exec client ip route get 10.10.1.1
> 10.10.1.1 via 10.10.0.254 dev veth0_c src 10.10.0.1 uid 0
>     cache
> 
> Fixes: d52e5a7e7ca49 ("ipv4: lock mtu in fnhe when received PMTU < net.ipv4.route.min_pmtu")
> Reported-by: Jianlin Shi <jishi@redhat.com>
> Reviewed-by: Stefano Brivio <sbrivio@redhat.com>
> Signed-off-by: Hangbin Liu <liuhangbin@gmail.com>

Applied.