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 <nicolas.dichtel@6wind.com>
Reported-by: kbuild test robot <lkp@intel.com>
Acked-by: Nick Desaulniers <ndesaulniers@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/vrf.c

@@ -350,8 +350,8 @@ static int vrf_finish_output6(struct net *net, struct sock *sk,
 {
 	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

@@ -262,8 +262,8 @@ static inline bool ip6_sk_ignore_df(const struct sock *sk)
 	       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

@@ -160,10 +160,10 @@ static inline struct lowpan_peer *peer_lookup_dst(struct lowpan_btle_dev *dev,
 						  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

@@ -59,8 +59,8 @@ static int ip6_finish_output2(struct net *net, struct sock *sk, struct sk_buff *
 {
 	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

@@ -439,9 +439,9 @@ nf_flow_offload_ipv6_hook(void *priv, struct sk_buff *skb,
 	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;