[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>

2 files changed, 6 insertions, 5 deletions

diff --git a/net/ipv4/ipvs/ip_vs_core.c b/net/ipv4/ipvs/ip_vs_core.c
index 5fb257dd07cb..3ac7eeca04ac 100644
--- a/net/ipv4/ipvs/ip_vs_core.c
+++ b/net/ipv4/ipvs/ip_vs_core.c
@@ -22,6 +22,7 @@
  *
  * Changes:
  *      Paul `Rusty' Russell            properly handle non-linear skbs
+ *      Harald Welte                    don't use nfcache
  *
  */
 
@@ -529,7 +530,7 @@ static unsigned int ip_vs_post_routing(unsigned int hooknum,
                                        const struct net_device *out,
                                        int (*okfn)(struct sk_buff *))
 {
-        if (!((*pskb)->nfcache & NFC_IPVS_PROPERTY))
+        if (!((*pskb)->ipvs_property))
                 return NF_ACCEPT;
 
         /* The packet was sent from IPVS, exit this chain */
@@ -701,7 +702,7 @@ static int ip_vs_out_icmp(struct sk_buff **pskb, int *related)
         /* do the statistics and put it back */
         ip_vs_out_stats(cp, skb);
 
-        skb->nfcache |= NFC_IPVS_PROPERTY;
+        skb->ipvs_property = 1;
         verdict = NF_ACCEPT;
 
   out:
@@ -739,7 +740,7 @@ ip_vs_out(unsigned int hooknum, struct sk_buff **pskb,
 
         EnterFunction(11);
 
-        if (skb->nfcache & NFC_IPVS_PROPERTY)
+        if (skb->ipvs_property)
                 return NF_ACCEPT;
 
         iph = skb->nh.iph;
@@ -821,7 +822,7 @@ ip_vs_out(unsigned int hooknum, struct sk_buff **pskb,
         ip_vs_set_state(cp, IP_VS_DIR_OUTPUT, skb, pp);
         ip_vs_conn_put(cp);
 
-        skb->nfcache |= NFC_IPVS_PROPERTY;
+        skb->ipvs_property = 1;
 
         LeaveFunction(11);
         return NF_ACCEPT;
diff --git a/net/ipv4/ipvs/ip_vs_xmit.c b/net/ipv4/ipvs/ip_vs_xmit.c
index a8512a3fd08a..3b87482049cf 100644
--- a/net/ipv4/ipvs/ip_vs_xmit.c
+++ b/net/ipv4/ipvs/ip_vs_xmit.c
@@ -127,7 +127,7 @@ ip_vs_dst_reset(struct ip_vs_dest *dest)
 
 #define IP_VS_XMIT(skb, rt)                             \
 do {                                                    \
-        (skb)->nfcache |= NFC_IPVS_PROPERTY;            \
+        (skb)->ipvs_property = 1;                       \
         (skb)->ip_summed = CHECKSUM_NONE;               \
         NF_HOOK(PF_INET, NF_IP_LOCAL_OUT, (skb), NULL,  \
                 (rt)->u.dst.dev, dst_output);           \