netdev - Re: [PATCH net-next] ipv4: introduce ip_dst_mtu_secure and protect forwarding path against pmtu spoofing

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Message-ID: <20140102175717.GG22494@order.stressinduktion.org>
Date:	Thu, 2 Jan 2014 18:57:17 +0100
From:	Hannes Frederic Sowa <hannes@...essinduktion.org>
To:	David Miller <davem@...emloft.net>
Cc:	johnwheffner@...il.com, netdev@...r.kernel.org,
	eric.dumazet@...il.com
Subject: Re: [PATCH net-next] ipv4: introduce ip_dst_mtu_secure and protect forwarding path against pmtu spoofing

On Thu, Dec 19, 2013 at 02:30:12PM -0500, David Miller wrote:
> No end host should have rp_filter on.  It unnecessarily makes our
> routing lookups much more expensive for zero gain on an end host.  But
> people convinced the distributions that turning it on everywhere by
> default was a good idea and it stuck.

Just was thinking about that again when reading the quote on lwn:

Maybe distributions just wanted to be always on the safe side.  As there
is no easy conditional system to enable rp_filter in case a user enables
forwarding, maybe something like

rp_filter:
0 - disable
1 - enable only in case of forwarding
2 - always enable

could be helpful?

I guess it is too late to change this.

Greetings,

  Hannes

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