netdev - Re: TCP-MD5 checksum failure on x86

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Message-ID: <1273245486.2261.76.camel@edumazet-laptop>
Date:	Fri, 07 May 2010 17:18:06 +0200
From:	Eric Dumazet <eric.dumazet@...il.com>
To:	Bhaskar Dutta <bhaskie@...il.com>
Cc:	Stephen Hemminger <shemminger@...tta.com>,
	Ben Hutchings <bhutchings@...arflare.com>,
	netdev@...r.kernel.org, David Miller <davem@...emloft.net>
Subject: Re: TCP-MD5 checksum failure on x86_64 SMP

OK, I found the second problem.

if/when IP route cache is invalidated, ip_queue_xmit() has to refetch a
route and calls sk_setup_caps(sk, &rt->u.dst), destroying the 

sk->sk_route_caps &= ~NETIF_F_GSO_MASK

that MD5 desesperatly try to make all over its way (from
tcp_transmit_skb() for example)

So we send few bad packets, and everything is fine when
tcp_transmit_skb() is called again.

You get many errors on remote peer if you do

ip route flush cache



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