netdev - Re: TCP fast retransmit

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Date:	Fri, 09 Dec 2011 17:31:04 +0100
From:	Eric Dumazet <eric.dumazet@...il.com>
To:	"Esztermann, Ansgar" <Ansgar.Esztermann@...-bpc.mpg.de>
Cc:	"netdev@...r.kernel.org" <netdev@...r.kernel.org>
Subject: Re: TCP fast retransmit

Le vendredi 09 décembre 2011 à 17:17 +0100, Esztermann, Ansgar a écrit :
> On Dec 9, 2011, at 15:43 , Eric Dumazet wrote:
> 
> > It seems you have a lot of packet reorders.
> > 
> > Are you using multipath or some channel bonding ?
> 
> Not that I am aware of (i.e. not on our end). However, the connection
> will probably routed through a firewall. I will have to check if it is
> configured to avoid reordering.
> 

Is it a linux based firewall ?

I suspect this firewall terminates a tunnel ?

If so, make sure network interrupts are handled by the same cpu.

(because tunneling means calling netif_rx() : This can be the reason for
Out Of Order packets, if next hardware interrupt is delivered to another
cpu)

We really should call netif_receive_skb() for the first tunnel level to
avoid this...



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