[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, 1 deletions

diff --git a/net/ipv6/icmp.c b/net/ipv6/icmp.c
index d3edc3cf1ce..e94992ab92e 100644
--- a/net/ipv6/icmp.c
+++ b/net/ipv6/icmp.c
@@ -317,7 +317,8 @@ void icmpv6_send(struct sk_buff *skb, int type, int code, __u32 info,
         int hlimit, tclass;
         int err = 0;
 
-        if ((u8*)hdr < skb->head || (u8*)(hdr+1) > skb->tail)
+        if ((u8 *)hdr < skb->head ||
+            (skb->network_header + sizeof(*hdr)) > skb->tail)
                 return;
 
         /*