[NETFILTER]: nf_{conntrack,nat}_proto_gre: annotate with const

Signed-off-by: Jan Engelhardt <jengelh@computergmbh.de>
Signed-off-by: Patrick McHardy <kaber@trash.net>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/ipv4/netfilter/nf_nat_proto_gre.c

@@ -104,7 +104,7 @@ gre_manip_pkt(struct sk_buff *skb, unsigned int iphdroff,
 {
 	struct gre_hdr *greh;
 	struct gre_hdr_pptp *pgreh;
-	struct iphdr *iph = (struct iphdr *)(skb->data + iphdroff);
+	const struct iphdr *iph = (struct iphdr *)(skb->data + iphdroff);
 	unsigned int hdroff = iphdroff + iph->ihl * 4;
 
 	/* pgreh includes two optional 32bit fields which are not required

net/netfilter/nf_conntrack_proto_gre.c

@@ -161,9 +161,11 @@ static int gre_pkt_to_tuple(const struct sk_buff *skb,
 			   unsigned int dataoff,
 			   struct nf_conntrack_tuple *tuple)
 {
-	struct gre_hdr_pptp _pgrehdr, *pgrehdr;
+	const struct gre_hdr_pptp *pgrehdr;
+	struct gre_hdr_pptp _pgrehdr;
 	__be16 srckey;
-	struct gre_hdr _grehdr, *grehdr;
+	const struct gre_hdr *grehdr;
+	struct gre_hdr _grehdr;
 
 	/* first only delinearize old RFC1701 GRE header */
 	grehdr = skb_header_pointer(skb, dataoff, sizeof(_grehdr), &_grehdr);