net: cleanup and document skb fclone layout

Lets use a proper structure to clearly document and implement
skb fast clones.

Then, we might experiment more easily alternative layouts.

This patch adds a new skb_fclone_busy() helper, used by tcp and xfrm,
to stop leaking of implementation details.

Signed-off-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 1 insertions, 3 deletions

diff --git a/net/xfrm/xfrm_policy.c b/net/xfrm/xfrm_policy.c
index f623dca6ce30..4c4e457e7888 100644
--- a/net/xfrm/xfrm_policy.c
+++ b/net/xfrm/xfrm_policy.c
@@ -1961,10 +1961,8 @@ static int xdst_queue_output(struct sock *sk, struct sk_buff *skb)
         struct xfrm_dst *xdst = (struct xfrm_dst *) dst;
         struct xfrm_policy *pol = xdst->pols[0];
         struct xfrm_policy_queue *pq = &pol->polq;
-        const struct sk_buff *fclone = skb + 1;
 
-        if (unlikely(skb->fclone == SKB_FCLONE_ORIG &&
-                     fclone->fclone == SKB_FCLONE_CLONE)) {
+        if (unlikely(skb_fclone_busy(skb))) {
                 kfree_skb(skb);
                 return 0;
         }