netdev - Re: [PATCH net] ipv4/icmp: redirect messages can use the ingress daddr as source

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Message-Id: <20151012.193815.2255829332660714250.davem@davemloft.net>
Date:	Mon, 12 Oct 2015 19:38:15 -0700 (PDT)
From:	David Miller <davem@...emloft.net>
To:	pabeni@...hat.com
Cc:	netdev@...r.kernel.org, corbet@....net, kuznet@....inr.ac.ru,
	jmorris@...ei.org, yoshfuji@...ux-ipv6.org, kaber@...sh.net
Subject: Re: [PATCH net] ipv4/icmp: redirect messages can use the ingress
 daddr as source

From: Paolo Abeni <pabeni@...hat.com>
Date: Fri,  9 Oct 2015 14:34:31 +0200

> This patch allows configuring how the source address of ICMP
> redirect messages is selected; by default the old behaviour is
> retained, while setting icmp_redirects_use_orig_daddr force the
> usage of the destination address of the packet that caused the
> redirect.
> 
> The new behaviour fits closely the RFC 5798 section 8.1.1, and fix the
> following scenario:
> 
> Two machines are set up with VRRP to act as routers out of a subnet,
> they have IPs x.x.x.1/24 and x.x.x.2/24, with VRRP holding on to
> x.x.x.254/24.
> 
> If a host in said subnet needs to get an ICMP redirect from the VRRP
> router, i.e. to reach a destination behind a different gateway, the
> source IP in the ICMP redirect is chosen as the primary IP on the
> interface that the packet arrived at, i.e. x.x.x.1 or x.x.x.2.
> 
> The host will then ignore said redirect, due to RFC 1122 section 3.2.2.2,
> and will continue to use the wrong next-op.
> 
> Signed-off-by: Paolo Abeni <pabeni@...hat.com>

Applied to net-next, thanks.
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