inet: constify ip headers and in6_addr

Add const qualifiers to structs iphdr, ipv6hdr and in6_addr pointers
where possible, to make code intention more obvious.

Signed-off-by: Eric Dumazet <eric.dumazet@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/net/ipv6/icmp.c b/net/ipv6/icmp.c
index 83cb4f9..1190041 100644
--- a/net/ipv6/icmp.c
+++ b/net/ipv6/icmp.c
@@ -372,7 +372,7 @@
 	struct ipv6hdr *hdr = ipv6_hdr(skb);
 	struct sock *sk;
 	struct ipv6_pinfo *np;
-	struct in6_addr *saddr = NULL;
+	const struct in6_addr *saddr = NULL;
 	struct dst_entry *dst;
 	struct icmp6hdr tmp_hdr;
 	struct flowi6 fl6;
@@ -521,7 +521,7 @@
 	struct sock *sk;
 	struct inet6_dev *idev;
 	struct ipv6_pinfo *np;
-	struct in6_addr *saddr = NULL;
+	const struct in6_addr *saddr = NULL;
 	struct icmp6hdr *icmph = icmp6_hdr(skb);
 	struct icmp6hdr tmp_hdr;
 	struct flowi6 fl6;
@@ -645,8 +645,8 @@
 {
 	struct net_device *dev = skb->dev;
 	struct inet6_dev *idev = __in6_dev_get(dev);
-	struct in6_addr *saddr, *daddr;
-	struct ipv6hdr *orig_hdr;
+	const struct in6_addr *saddr, *daddr;
+	const struct ipv6hdr *orig_hdr;
 	struct icmp6hdr *hdr;
 	u8 type;