Because the IPsec output function xfrm_output_resume does its
own dst_output call it should always call __ip_local_output
instead of ip_local_output as the latter may invoke dst_output
directly.  Otherwise the return values from nf_hook and dst_output
may clash as they both use the value 1 but for different purposes.

When that clash occurs this can cause a packet to be used after
it has been freed which usually leads to a crash.  Because the
offending value is only returned from dst_output with qdiscs
such as HTB, this bug is normally not visible.

Thanks to Marco Berizzi for his perseverance in tracking this
down.
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
Signed-off-by: David S. Miller <davem@davemloft.net>