netdev - Re: routing PF

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Message-Id: <200809221704.09530.remi.denis-courmont@nokia.com>
Date:	Mon, 22 Sep 2008 17:04:09 +0300
From:	"Rémi Denis-Courmont" 
	<remi.denis-courmont@...ia.com>
To:	ext Raúl Hernández <rauhersu@...il.com>
Cc:	netdev@...r.kernel.org
Subject: Re: routing PF_PACKET sockets

On Monday 22 September 2008 16:39:59 ext Raúl Hernández, you wrote:
> Just to clarify it a bit more; Suppose that a user app has two
> PF_PACKET sockets (SOCK_RAW) over eth0 and eth1 (to ensure redundancy)
> to send data to the network. In case eth0 is down, it would be
> useless, for example, move the routing table entries which reference
> eth0 to eth1 as the app which sends data to the network bypasses any
> routing policy (I think this would do if my app used standard tcp
> sockets).

If eth0 really goes down, your eth0 socket will receive ENETDOWN error.

Routing tables entries for a down interface are automatically disabled, but 
you would not care since your PF_PACKET sockets bypass these.

-- 
Rémi Denis-Courmont
Maemo Software, Nokia Devices R&D
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