Suggestion to Improve delivery to local destinations

["Narik Alatees" <yedok@hotmail.com>]

Currently ip_route_output_slow() sets rth->u.dst.output = ip_output; And 
then there is this line in the same function:

if (flags & RTCF_LOCAL) {
               rth->u.dst.input = ip_local_deliver;
               rth->rt_spec_dst = fl.fl4_dst;
}

Basically what this means is that when the user calls skb->dst->output(), 
neighbour resolution would be implicitly performed. And at the time of 
actually sending an ARP request for link layer address the transmission is 
bypassed (due to the check in neigh_event_send()) and a dummy neighbour 
entry for the loopback device is constructured.

I propose that in the above code fragment rth->u.dst.output be changed to 
ip_dev_loopback_xmit() (much like what happens inside of ip_mc_output()). I 
think this would _significantly_ improve performance in the 
delivery-to-local-destination case. What do you think?

tx
yedok

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