From mboxrd@z Thu Jan  1 00:00:00 1970
From: David Miller <davem@davemloft.net>
Subject: Re: problem of "ipv4: revert Set rt->rt_iif more sanely on output
 routes."
Date: Wed, 06 Apr 2011 22:34:00 -0700 (PDT)
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From: OGAWA Hirofumi <hirofumi@mail.parknet.co.jp>
Date: Thu, 07 Apr 2011 13:31:06 +0900

> I'm not pretty sure though, output message is
> 
> 	ip_finish_output2: No header cache and no neighbour!
> 
> I'm not debugging this though,
> 
> static inline bool rt_is_output_route(struct rtable *rt)
> {
> 	return rt->rt_iif == 0;
> }
> 
> from review I guess the above is one of cause.

arp_bind_neighbour() is only called if rt_is_output_route() is true
or route is unicast.

If packet is sent using a route for which arp_bind_neighbour() has not
been called, you will see that warning message.