linux-kernel - Re: [patch 23/32] IPV4: Correct rp

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Message-Id: <E1HwpdD-0008Il-00@gondolin.me.apana.org.au>
Date:	Sat, 09 Jun 2007 11:20:43 +1000
From:	Herbert Xu <herbert@...dor.apana.org.au>
To:	chrisw@...s-sol.org (Chris Wright)
Cc:	linux-kernel@...r.kernel.org, davem@...emloft.net,
	netdev@...r.kernel.org
Subject: Re: [patch 23/32] IPV4: Correct rp_filter help text.

Chris Wright <chrisw@...s-sol.org> wrote:
> 
> --- linux-2.6.20.13.orig/net/ipv4/Kconfig
> +++ linux-2.6.20.13/net/ipv4/Kconfig
> @@ -43,11 +43,11 @@ config IP_ADVANCED_ROUTER
>          asymmetric routing (packets from you to a host take a different path
>          than packets from that host to you) or if you operate a non-routing
>          host which has several IP addresses on different interfaces. To turn
> -         rp_filter off use:
> +         rp_filter on use:
> 
> -         echo 0 > /proc/sys/net/ipv4/conf/<device>/rp_filter
> +         echo 1 > /proc/sys/net/ipv4/conf/<device>/rp_filter
>          or
> -         echo 0 > /proc/sys/net/ipv4/conf/all/rp_filter
> +         echo 1 > /proc/sys/net/ipv4/conf/all/rp_filter

BTW, this documentation is actually wrong.  You can't enable rp_filter
on all interfaces with

	echo 1 > /proc/sys/net/ipv4/conf/all/rp_filter

You must do that in conjunction with

	echo 1 > /proc/sys/net/ipv4/conf/<device>/rp_filter

for it to work for <device>.

This is really counter-intuitive but it's apparently how it's always
worked.

Cheers,
-- 
Visit Openswan at http://www.openswan.org/
Email: Herbert Xu ~{PmV>HI~} <herbert@...dor.apana.org.au>
Home Page: http://gondor.apana.org.au/~herbert/
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