ipv6: raw: preserve const qualifier in raw6_sk()

We can change raw6_sk() to propagate its argument const qualifier,
thanks to container_of_const().
Signed-off-by: Eric Dumazet <edumazet@google.com>
Reviewed-by: Simon Horman <simon.horman@corigine.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

include/linux/ipv6.h

@@ -336,10 +336,7 @@ static inline struct ipv6_pinfo *inet6_sk(const struct sock *__sk)
 	return sk_fullsock(__sk) ? inet_sk(__sk)->pinet6 : NULL;
 }
 
-static inline struct raw6_sock *raw6_sk(const struct sock *sk)
-{
-	return (struct raw6_sock *)sk;
-}
+#define raw6_sk(ptr) container_of_const(ptr, struct raw6_sock, inet.sk)
 
 #define ipv6_only_sock(sk)	(sk->sk_ipv6only)
 #define ipv6_sk_rxinfo(sk)	((sk)->sk_family == PF_INET6 && \