tcp: Save v4 address as v4-mapped-v6 in inet_bind2_bucket.v6_rcv_saddr.

In bhash2, IPv4/IPv6 addresses are saved in two union members,
which complicate address checks in inet_bind2_bucket_addr_match()
and inet_bind2_bucket_match_addr_any() considering uninitialised
memory and v4-mapped-v6 conflicts.

Let's simplify that by saving IPv4 address as v4-mapped-v6 address
and defining tb2.rcv_saddr as tb2.v6_rcv_saddr.s6_addr32[3].

Then, we can compare v6 address as is, and after checking v4-mapped-v6,
we can compare v4 address easily.  Also, we can remove tb2->family.

Note these functions will be further refactored in the next patch.

Signed-off-by: Kuniyuki Iwashima <kuniyu@amazon.com>
Reviewed-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

Author: q2ven

include/net/inet_hashtables.h

@@ -96,14 +96,11 @@ struct inet_bind2_bucket {
 	int			l3mdev;
 	unsigned short		port;
 #if IS_ENABLED(CONFIG_IPV6)
-	unsigned short		family;
-#endif
-	union {
-#if IS_ENABLED(CONFIG_IPV6)
-		struct in6_addr		v6_rcv_saddr;
+	struct in6_addr		v6_rcv_saddr;
+#define rcv_saddr		v6_rcv_saddr.s6_addr32[3]
+#else
+	__be32			rcv_saddr;
 #endif
-		__be32			rcv_saddr;
-	};
 	/* Node in the bhash2 inet_bind_hashbucket chain */
 	struct hlist_node	node;
 	/* List of sockets hashed to this bucket */

include/net/ipv6.h

@@ -784,11 +784,6 @@ static inline bool ipv6_addr_v4mapped(const struct in6_addr *a)
 					cpu_to_be32(0x0000ffff))) == 0UL;
 }
 
-static inline bool ipv6_addr_v4mapped_any(const struct in6_addr *a)
-{
-	return ipv6_addr_v4mapped(a) && ipv4_is_zeronet(a->s6_addr32[3]);
-}
-
 static inline bool ipv6_addr_v4mapped_loopback(const struct in6_addr *a)
 {
 	return ipv6_addr_v4mapped(a) && ipv4_is_loopback(a->s6_addr32[3]);

net/ipv4/inet_hashtables.c

@@ -110,12 +110,13 @@ static void inet_bind2_bucket_init(struct inet_bind2_bucket *tb,
 	tb->l3mdev    = l3mdev;
 	tb->port      = port;
 #if IS_ENABLED(CONFIG_IPV6)
-	tb->family    = sk->sk_family;
 	if (sk->sk_family == AF_INET6)
 		tb->v6_rcv_saddr = sk->sk_v6_rcv_saddr;
 	else
+		ipv6_addr_set_v4mapped(sk->sk_rcv_saddr, &tb->v6_rcv_saddr);
+#else
+	tb->rcv_saddr = sk->sk_rcv_saddr;
 #endif
-		tb->rcv_saddr = sk->sk_rcv_saddr;
 	INIT_HLIST_HEAD(&tb->owners);
 	INIT_HLIST_HEAD(&tb->deathrow);
 	hlist_add_head(&tb->node, &head->chain);
@@ -149,17 +150,11 @@ static bool inet_bind2_bucket_addr_match(const struct inet_bind2_bucket *tb2,
 					 const struct sock *sk)
 {
 #if IS_ENABLED(CONFIG_IPV6)
-	if (sk->sk_family == AF_INET6) {
-		if (tb2->family == AF_INET6)
-			return ipv6_addr_equal(&tb2->v6_rcv_saddr, &sk->sk_v6_rcv_saddr);
-
-		return ipv6_addr_v4mapped(&sk->sk_v6_rcv_saddr) &&
-			sk->sk_v6_rcv_saddr.s6_addr32[3] == tb2->rcv_saddr;
-	}
+	if (sk->sk_family == AF_INET6)
+		return ipv6_addr_equal(&tb2->v6_rcv_saddr, &sk->sk_v6_rcv_saddr);
 
-	if (tb2->family == AF_INET6)
-		return ipv6_addr_v4mapped(&tb2->v6_rcv_saddr) &&
-			tb2->v6_rcv_saddr.s6_addr32[3] == sk->sk_rcv_saddr;
+	if (!ipv6_addr_v4mapped(&tb2->v6_rcv_saddr))
+		return false;
 #endif
 	return tb2->rcv_saddr == sk->sk_rcv_saddr;
 }
@@ -836,16 +831,21 @@ bool inet_bind2_bucket_match_addr_any(const struct inet_bind2_bucket *tb, const
 
 #if IS_ENABLED(CONFIG_IPV6)
 	if (sk->sk_family == AF_INET6) {
-		if (tb->family == AF_INET6)
-			return ipv6_addr_any(&tb->v6_rcv_saddr);
+		if (ipv6_addr_any(&tb->v6_rcv_saddr))
+			return true;
+
+		if (!ipv6_addr_v4mapped(&tb->v6_rcv_saddr))
+			return false;
 
 		return ipv6_addr_v4mapped(&sk->sk_v6_rcv_saddr) &&
 			tb->rcv_saddr == 0;
 	}
 
-	if (tb->family == AF_INET6)
-		return ipv6_addr_any(&tb->v6_rcv_saddr) ||
-			ipv6_addr_v4mapped_any(&tb->v6_rcv_saddr);
+	if (ipv6_addr_any(&tb->v6_rcv_saddr))
+		return true;
+
+	if (!ipv6_addr_v4mapped(&tb->v6_rcv_saddr))
+		return false;
 #endif
 	return tb->rcv_saddr == 0;
 }