xfrm: Separate ESP handling from segmentation for GRO packets.

We change the ESP GSO handlers to only segment the packets.
The ESP handling and encryption is defered to validate_xmit_xfrm()
where this is done for non GRO packets too. This makes the code
more robust and prepares for asynchronous crypto handling.

Signed-off-by: Steffen Klassert <steffen.klassert@secunet.com>
diff --git a/net/ipv4/xfrm4_mode_tunnel.c b/net/ipv4/xfrm4_mode_tunnel.c
index 7d885a4..8affc6d 100644
--- a/net/ipv4/xfrm4_mode_tunnel.c
+++ b/net/ipv4/xfrm4_mode_tunnel.c
@@ -105,18 +105,15 @@ static struct sk_buff *xfrm4_mode_tunnel_gso_segment(struct xfrm_state *x,
 {
 	__skb_push(skb, skb->mac_len);
 	return skb_mac_gso_segment(skb, features);
-
 }
 
 static void xfrm4_mode_tunnel_xmit(struct xfrm_state *x, struct sk_buff *skb)
 {
 	struct xfrm_offload *xo = xfrm_offload(skb);
 
-	if (xo->flags & XFRM_GSO_SEGMENT) {
-		skb->network_header = skb->network_header - x->props.header_len;
+	if (xo->flags & XFRM_GSO_SEGMENT)
 		skb->transport_header = skb->network_header +
 					sizeof(struct iphdr);
-	}
 
 	skb_reset_mac_len(skb);
 	pskb_pull(skb, skb->mac_len + x->props.header_len);