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/xfrm/xfrm_state.c b/net/xfrm/xfrm_state.c
index dd78536..d70f85e 100644
--- a/net/xfrm/xfrm_state.c
+++ b/net/xfrm/xfrm_state.c
@@ -1036,15 +1036,15 @@
 
 		case AF_INET6:
 			ipv6_addr_copy((struct in6_addr *)x->sel.daddr.a6,
-				       (struct in6_addr *)daddr);
+				       (const struct in6_addr *)daddr);
 			ipv6_addr_copy((struct in6_addr *)x->sel.saddr.a6,
-				       (struct in6_addr *)saddr);
+				       (const struct in6_addr *)saddr);
 			x->sel.prefixlen_d = 128;
 			x->sel.prefixlen_s = 128;
 			ipv6_addr_copy((struct in6_addr *)x->props.saddr.a6,
-				       (struct in6_addr *)saddr);
+				       (const struct in6_addr *)saddr);
 			ipv6_addr_copy((struct in6_addr *)x->id.daddr.a6,
-				       (struct in6_addr *)daddr);
+				       (const struct in6_addr *)daddr);
 			break;
 		}
 
@@ -2092,8 +2092,8 @@
 static void xfrm_audit_helper_pktinfo(struct sk_buff *skb, u16 family,
 				      struct audit_buffer *audit_buf)
 {
-	struct iphdr *iph4;
-	struct ipv6hdr *iph6;
+	const struct iphdr *iph4;
+	const struct ipv6hdr *iph6;
 
 	switch (family) {
 	case AF_INET: