inet: add IPv6 support to sk_ehashfn()

Intent is to converge IPv4 & IPv6 inet_hash functions to
factorize code.

IPv4 sockets initialize sk_rcv_saddr and sk_v6_daddr
in this patch, thanks to new sk_daddr_set() and sk_rcv_saddr_set()
helpers.

__inet6_hash can now use sk_ehashfn() instead of a private
inet6_sk_ehashfn() and will simply use __inet_hash() in a
following patch.

Signed-off-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/net/ipv6/tcp_ipv6.c b/net/ipv6/tcp_ipv6.c
index e4761b2..5546df0 100644
--- a/net/ipv6/tcp_ipv6.c
+++ b/net/ipv6/tcp_ipv6.c
@@ -233,11 +233,8 @@
 			tp->af_specific = &tcp_sock_ipv6_specific;
 #endif
 			goto failure;
-		} else {
-			ipv6_addr_set_v4mapped(inet->inet_saddr, &np->saddr);
-			ipv6_addr_set_v4mapped(inet->inet_rcv_saddr,
-					       &sk->sk_v6_rcv_saddr);
 		}
+		np->saddr = sk->sk_v6_rcv_saddr;
 
 		return err;
 	}
@@ -1078,11 +1075,7 @@
 
 		memcpy(newnp, np, sizeof(struct ipv6_pinfo));
 
-		ipv6_addr_set_v4mapped(newinet->inet_daddr, &newsk->sk_v6_daddr);
-
-		ipv6_addr_set_v4mapped(newinet->inet_saddr, &newnp->saddr);
-
-		newsk->sk_v6_rcv_saddr = newnp->saddr;
+		newnp->saddr = newsk->sk_v6_rcv_saddr;
 
 		inet_csk(newsk)->icsk_af_ops = &ipv6_mapped;
 		newsk->sk_backlog_rcv = tcp_v4_do_rcv;