[SK_BUFF]: Convert skb->tail to sk_buff_data_t

So that it is also an offset from skb->head, reduces its size from 8 to 4 bytes
on 64bit architectures, allowing us to combine the 4 bytes hole left by the
layer headers conversion, reducing struct sk_buff size to 256 bytes, i.e. 4
64byte cachelines, and since the sk_buff slab cache is SLAB_HWCACHE_ALIGN...
:-)

Many calculations that previously required that skb->{transport,network,
mac}_header be first converted to a pointer now can be done directly, being
meaningful as offsets or pointers.

Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 2 insertions, 2 deletions

diff --git a/net/ipv6/mip6.c b/net/ipv6/mip6.c
index f0288e92fb52..6ed763ee6785 100644
--- a/net/ipv6/mip6.c
+++ b/net/ipv6/mip6.c
@@ -260,7 +260,7 @@ static int mip6_destopt_offset(struct xfrm_state *x, struct sk_buff *skb,
         struct ipv6_opt_hdr *exthdr =
                                    (struct ipv6_opt_hdr *)(ipv6_hdr(skb) + 1);
         const unsigned char *nh = skb_network_header(skb);
-        unsigned int packet_len = skb->tail - nh;
+        unsigned int packet_len = skb->tail - skb->network_header;
         int found_rhdr = 0;
 
         *nexthdr = &ipv6_hdr(skb)->nexthdr;
@@ -392,7 +392,7 @@ static int mip6_rthdr_offset(struct xfrm_state *x, struct sk_buff *skb,
         struct ipv6_opt_hdr *exthdr =
                                    (struct ipv6_opt_hdr *)(ipv6_hdr(skb) + 1);
         const unsigned char *nh = skb_network_header(skb);
-        unsigned int packet_len = skb->tail - nh;
+        unsigned int packet_len = skb->tail - skb->network_header;
         int found_rhdr = 0;
 
         *nexthdr = &ipv6_hdr(skb)->nexthdr;