From: David S. Miller <davem@davemloft.net>
Date: Thu, 28 Jun 2012 10:59:11 +0000 (-0700)
Subject: ipv4: Create and use fib_compute_spec_dst() helper.
X-Git-Tag: v3.6-rc1~125^2~357
X-Git-Url: http://git.openpandora.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=35ebf65e851c6d9731abc6362b189858eb59f4d3;p=pandora-kernel.git

ipv4: Create and use fib_compute_spec_dst() helper.

The specific destination is the host we direct unicast replies to.
Usually this is the original packet source address, but if we are
responding to a multicast or broadcast packet we have to use something
different.

Specifically we must use the source address we would use if we were to
send a packet to the unicast source of the original packet.

The routing cache precomputes this value, but we want to remove that
precomputation because it creates a hard dependency on the expensive
rpfilter source address validation which we'd like to make cheaper.

There are only three places where this matters:

1) ICMP replies.

2) pktinfo CMSG

3) IP options

Now there will be no real users of rt->rt_spec_dst and we can simply
remove it altogether.

Signed-off-by: David S. Miller <davem@davemloft.net>
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