Re: [PATCH] Disable rp_filter for IPsec packets

[David Miller <davem@davemloft.net>]

From: Michael Smith <msmith@cbnco.com>
Date: Mon, 14 Mar 2011 17:14:59 -0400

> The reverse path filter interferes with IPsec subnet-to-subnet tunnels,
> especially when the link to the IPsec peer is on an interface other than
> the one hosting the default route.
> 
> With dynamic routing, where the peer might be reachable through eth0
> today and eth1 tomorrow, it's difficult to keep rp_filter enabled unless
> fake routes to the remote subnets are configured on the interface
> currently used to reach the peer.
> 
> IPsec provides a much stronger anti-spoofing policy than rp_filter, so
> this patch disables the rp_filter for packets with a security path.
> 
> Signed-off-by: Michael Smith <msmith@cbnco.com>

First, I'm only willing to accept a patch like this to net-next-2.6
for which all of the code you are changing is radically different.

Secondly, fib_validate_source() already takes too many damn arguments.
Find another, less costly, way to pass this information down there.

Frankly, I think RPF should be disabled completely by default.  When
it doesn't do anything useful, it's making route lookups twice as
expensive as they need to be.