[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, 5 insertions, 5 deletions

diff --git a/include/linux/skbuff.h b/include/linux/skbuff.h
index 2e40f4c9f7a..4b929c3c1a9 100644
--- a/include/linux/skbuff.h
+++ b/include/linux/skbuff.h
@@ -190,7 +190,6 @@ struct skb_shared_info {
  *      @end: End pointer
  *      @destructor: Destruct function
  *      @nfmark: Can be used for communication between hooks
- *      @nfcache: Cache info
  *      @nfct: Associated connection, if any
  *      @nfctinfo: Relationship of this skb to the connection
  *      @nf_bridge: Saved data about a bridged frame - see br_netfilter.c
@@ -252,17 +251,18 @@ struct sk_buff {
         __u8                    local_df:1,
                                 cloned:1,
                                 ip_summed:2,
-                                nohdr:1;
-                                /* 3 bits spare */
+                                nohdr:1,
+                                nfctinfo:3;
         __u8                    pkt_type;
         __be16                  protocol;
 
         void                    (*destructor)(struct sk_buff *skb);
 #ifdef CONFIG_NETFILTER
         __u32                   nfmark;
-        __u32                   nfcache;
-        __u32                   nfctinfo;
         struct nf_conntrack     *nfct;
+#if defined(CONFIG_IP_VS) || defined(CONFIG_IP_VS_MODULE)
+        __u8                    ipvs_property:1;
+#endif
 #ifdef CONFIG_BRIDGE_NETFILTER
         struct nf_bridge_info   *nf_bridge;
 #endif