netfilter: nf_conntrack: constify sk_buff argument to nf_ct_attach()

Signed-off-by: Patrick McHardy <kaber@trash.net>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
diff --git a/net/netfilter/core.c b/net/netfilter/core.c
index 2217363..593b16e 100644
--- a/net/netfilter/core.c
+++ b/net/netfilter/core.c
@@ -234,12 +234,13 @@
 /* This does not belong here, but locally generated errors need it if connection
    tracking in use: without this, connection may not be in hash table, and hence
    manufactured ICMP or RST packets will not be associated with it. */
-void (*ip_ct_attach)(struct sk_buff *, struct sk_buff *) __rcu __read_mostly;
+void (*ip_ct_attach)(struct sk_buff *, const struct sk_buff *)
+		__rcu __read_mostly;
 EXPORT_SYMBOL(ip_ct_attach);
 
-void nf_ct_attach(struct sk_buff *new, struct sk_buff *skb)
+void nf_ct_attach(struct sk_buff *new, const struct sk_buff *skb)
 {
-	void (*attach)(struct sk_buff *, struct sk_buff *);
+	void (*attach)(struct sk_buff *, const struct sk_buff *);
 
 	if (skb->nfct) {
 		rcu_read_lock();