[IPSEC]: Set skb->data to payload in x->mode->output

This patch changes the calling convention so that on entry from
x->mode->output and before entry into x->type->output skb->data
will point to the payload instead of the IP header.

This is essentially a redistribution of skb_push/skb_pull calls
with the aim of minimising them on the common path of tunnel +
ESP.

It'll also let us use the same calling convention between IPv4
and IPv6 with the next patch.

Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 7 insertions, 6 deletions

diff --git a/net/ipv6/xfrm6_mode_beet.c b/net/ipv6/xfrm6_mode_beet.c
index d9366dfbf868..bca018d19ec6 100644
--- a/net/ipv6/xfrm6_mode_beet.c
+++ b/net/ipv6/xfrm6_mode_beet.c
@@ -29,8 +29,8 @@
  * filled in by x->type->output and the mac header will be set to the
  * nextheader field of the extension header directly preceding the
  * encapsulation header, or in its absence, that of the top IP header.
- * The value of skb->data and the network header will always point to the
- * top IP header.
+ * The value of the network header will always point to the top IP header
+ * while skb->data will point to the payload.
  */
 static int xfrm6_beet_output(struct xfrm_state *x, struct sk_buff *skb)
 {
@@ -38,16 +38,17 @@ static int xfrm6_beet_output(struct xfrm_state *x, struct sk_buff *skb)
 	u8 *prevhdr;
 	int hdr_len;
 
-	skb_push(skb, x->props.header_len);
 	iph = ipv6_hdr(skb);
 
 	hdr_len = ip6_find_1stfragopt(skb, &prevhdr);
-	memmove(skb->data, iph, hdr_len);
 
 	skb_set_mac_header(skb, (prevhdr - x->props.header_len) - skb->data);
-	skb_reset_network_header(skb);
-	skb_set_transport_header(skb, hdr_len);
+	skb_set_network_header(skb, -x->props.header_len);
+	skb_set_transport_header(skb, hdr_len - x->props.header_len);
+	__skb_pull(skb, hdr_len);
+
 	top_iph = ipv6_hdr(skb);
+	memmove(top_iph, iph, hdr_len);
 
 	ipv6_addr_copy(&top_iph->saddr, (struct in6_addr *)&x->props.saddr);
 	ipv6_addr_copy(&top_iph->daddr, (struct in6_addr *)&x->id.daddr);