[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>

4 files changed, 4 insertions, 19 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())
diff --git a/net/ipv6/netfilter/ip6_queue.c b/net/ipv6/netfilter/ip6_queue.c
index a16df5b..83ccedc 100644
--- a/net/ipv6/netfilter/ip6_queue.c
+++ b/net/ipv6/netfilter/ip6_queue.c
@@ -388,7 +388,6 @@ ipq_mangle_ipv6(ipq_verdict_msg_t *v, struct ipq_queue_entry *e)
 		return -ENOMEM;
 	memcpy(e->skb->data, v->payload, v->data_len);
 	e->skb->ip_summed = CHECKSUM_NONE;
-	e->skb->nfcache |= NFC_ALTERED;
 
 	/*
 	 * Extra routing may needed on local out, as the QUEUE target never
diff --git a/net/ipv6/netfilter/ip6_tables.c b/net/ipv6/netfilter/ip6_tables.c
index 7303451..41a67cf 100644
--- a/net/ipv6/netfilter/ip6_tables.c
+++ b/net/ipv6/netfilter/ip6_tables.c
@@ -401,7 +401,6 @@ ip6t_do_table(struct sk_buff **pskb,
 	do {
 		IP_NF_ASSERT(e);
 		IP_NF_ASSERT(back);
-		(*pskb)->nfcache |= e->nfcache;
 		if (ip6_packet_match(*pskb, indev, outdev, &e->ipv6,
 			&protoff, &offset)) {
 			struct ip6t_entry_target *t;
diff --git a/net/ipv6/netfilter/ip6t_MARK.c b/net/ipv6/netfilter/ip6t_MARK.c
index d09ceb0..81924fc 100644
--- a/net/ipv6/netfilter/ip6t_MARK.c
+++ b/net/ipv6/netfilter/ip6t_MARK.c
@@ -28,10 +28,9 @@ target(struct sk_buff **pskb,
 {
 	const struct ip6t_mark_target_info *markinfo = targinfo;
 
-	if((*pskb)->nfmark != markinfo->mark) {
+	if((*pskb)->nfmark != markinfo->mark)
 		(*pskb)->nfmark = markinfo->mark;
-		(*pskb)->nfcache |= NFC_ALTERED;
-	}
+
 	return IP6T_CONTINUE;
 }