the
packet is locally generated there is no inbound interface and
the sysctl should not apply.

The option actually seems to be unfixable broken, on the path
after ip_output() skb->dev points to the outgoing device and
we don't know the incoming device anymore, so its going to do
the absolute wrong thing and pick the address of the outgoing
interface. Add a comment about this.

Reported by Curtis Doty <Curtis@GreenKey.net>.

Signed-off-by: Patrick McHardy <kaber@trash.net>
Signed-off-by: David S. Miller <davem@davemloft.net>