ipv6: constify rt6_nexthop()

There is no functional change in this patch, it only prepares the next one.

rt6_nexthop() will be used by ip6_dst_lookup_neigh(), which uses const
variables.

Signed-off-by: Nicolas Dichtel <[e-mail]>
Reported-by: kbuild test robot <[e-mail]>
Acked-by: Nick Desaulniers <[e-mail]>
Signed-off-by: David S. Miller <[e-mail]>

drivers/net/vrf.c

···
 {
 	struct dst_entry *dst = skb_dst(skb);
 	struct net_device *dev = dst->dev;
+	const struct in6_addr *nexthop;
 	struct neighbour *neigh;
-	struct in6_addr *nexthop;
 	int ret;
 
 	nf_reset(skb);

include/net/ip6_route.h

···
 	       inet6_sk(sk)->pmtudisc == IPV6_PMTUDISC_OMIT;
 }
 
-static inline struct in6_addr *rt6_nexthop(struct rt6_info *rt,
-					   struct in6_addr *daddr)
+static inline const struct in6_addr *rt6_nexthop(const struct rt6_info *rt,
+						 const struct in6_addr *daddr)
 {
 	if (rt->rt6i_flags & RTF_GATEWAY)
 		return &rt->rt6i_gateway;

net/bluetooth/6lowpan.c

···
 						  struct in6_addr *daddr,
 						  struct sk_buff *skb)
 {
-	struct lowpan_peer *peer;
-	struct in6_addr *nexthop;
 	struct rt6_info *rt = (struct rt6_info *)skb_dst(skb);
 	int count = atomic_read(&dev->peer_count);
+	const struct in6_addr *nexthop;
+	struct lowpan_peer *peer;
 
 	BT_DBG("peers %d addr %pI6c rt %p", count, daddr, rt);
 

net/ipv6/ip6_output.c

···
 {
 	struct dst_entry *dst = skb_dst(skb);
 	struct net_device *dev = dst->dev;
+	const struct in6_addr *nexthop;
 	struct neighbour *neigh;
-	struct in6_addr *nexthop;
 	int ret;
 
 	if (ipv6_addr_is_multicast(&ipv6_hdr(skb)->daddr)) {

net/netfilter/nf_flow_table_ip.c

···
 	struct nf_flowtable *flow_table = priv;
 	struct flow_offload_tuple tuple = {};
 	enum flow_offload_tuple_dir dir;
+	const struct in6_addr *nexthop;
 	struct flow_offload *flow;
 	struct net_device *outdev;
-	struct in6_addr *nexthop;
 	struct ipv6hdr *ip6h;
 	struct rt6_info *rt;