[NETFILTER]: reduce netfilter sk_buff enlargement

As discussed at netconf'05, we're trying to save every bit in sk_buff.
The patch below makes sk_buff 8 bytes smaller.  I did some basic
testing on my notebook and it seems to work.

The only real in-tree user of nfcache was IPVS, who only needs a
single bit.  Unfortunately I couldn't find some other free bit in
sk_buff to stuff that bit into, so I introduced a separate field for
them.  Maybe the IPVS guys can resolve that to further save space.

Initially I wanted to shrink pkt_type to three bits (PACKET_HOST and
alike are only 6 values defined), but unfortunately the bluetooth code
overloads pkt_type :(

The conntrack-event-api (out-of-tree) uses nfcache, but Rusty just
came up with a way how to do it without any skb fields, so it's safe
to remove it.

- remove all never-implemented 'nfcache' code
- don't have ipvs code abuse 'nfcache' field. currently get's their own
  compile-conditional skb->ipvs_property field.  IPVS maintainers can
  decide to move this bit elswhere, but nfcache needs to die.
- remove skb->nfcache field to save 4 bytes
- move skb->nfctinfo into three unused bits to save further 4 bytes

Signed-off-by: Harald Welte <laforge@netfilter.org>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 2 insertions, 14 deletions

diff --git a/net/ipv6/ip6_output.c b/net/ipv6/ip6_output.c
index ae652ca..590d2b7 100644
--- a/net/ipv6/ip6_output.c
+++ b/net/ipv6/ip6_output.c
@@ -185,19 +185,6 @@ int ip6_route_me_harder(struct sk_buff *skb)
 }
 #endif
 
-static inline int ip6_maybe_reroute(struct sk_buff *skb)
-{
-#ifdef CONFIG_NETFILTER
-	if (skb->nfcache & NFC_ALTERED){
-		if (ip6_route_me_harder(skb) != 0){
-			kfree_skb(skb);
-			return -EINVAL;
-		}
-	}
-#endif /* CONFIG_NETFILTER */
-	return dst_output(skb);
-}
-
 /*
  *	xmit an sk_buff (used by TCP)
  */
@@ -266,7 +253,8 @@ int ip6_xmit(struct sock *sk, struct sk_buff *skb, struct flowi *fl,
 	mtu = dst_mtu(dst);
 	if ((skb->len <= mtu) || ipfragok) {
 		IP6_INC_STATS(IPSTATS_MIB_OUTREQUESTS);
-		return NF_HOOK(PF_INET6, NF_IP6_LOCAL_OUT, skb, NULL, dst->dev, ip6_maybe_reroute);
+		return NF_HOOK(PF_INET6, NF_IP6_LOCAL_OUT, skb, NULL, dst->dev,
+				dst_output);
 	}
 
 	if (net_ratelimit())