net: ensure unbound stream socket to be chosen when not in a VRF

The commit a04a480d43 ("net: Require exact match for TCP socket
lookups if dif is l3mdev") only ensures that the correct socket is
selected for packets in a VRF. However, there is no guarantee that
the unbound socket will be selected for packets when not in a VRF.
By checking for a device match in compute_score() also for the case
when there is no bound device and attaching a score to this, the
unbound socket is selected. And if a failure is returned when there
is no device match, this ensures that bound sockets are never selected,
even if there is no unbound socket.

Signed-off-by: Mike Manning <mmanning@vyatta.att-mail.com>
Reviewed-by: David Ahern <dsahern@gmail.com>
Tested-by: David Ahern <dsahern@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

include/net/inet_hashtables.h

@@ -189,6 +189,17 @@ static inline void inet_ehash_locks_free(struct inet_hashinfo *hashinfo)
 	hashinfo->ehash_locks = NULL;
 }
 
+static inline bool inet_sk_bound_dev_eq(struct net *net, int bound_dev_if,
+					int dif, int sdif)
+{
+#if IS_ENABLED(CONFIG_NET_L3_MASTER_DEV)
+	return inet_bound_dev_eq(!!net->ipv4.sysctl_tcp_l3mdev_accept,
+				 bound_dev_if, dif, sdif);
+#else
+	return inet_bound_dev_eq(true, bound_dev_if, dif, sdif);
+#endif
+}
+
 struct inet_bind_bucket *
 inet_bind_bucket_create(struct kmem_cache *cachep, struct net *net,
 			struct inet_bind_hashbucket *head,

include/net/inet_sock.h

@@ -143,6 +143,14 @@ static inline int inet_sk_bound_l3mdev(const struct sock *sk)
 	return 0;
 }
 
+static inline bool inet_bound_dev_eq(bool l3mdev_accept, int bound_dev_if,
+				     int dif, int sdif)
+{
+	if (!bound_dev_if)
+		return !sdif || l3mdev_accept;
+	return bound_dev_if == dif || bound_dev_if == sdif;
+}
+
 struct inet_cork {
 	unsigned int		flags;
 	__be32			addr;

net/ipv4/inet_hashtables.c

@@ -235,6 +235,7 @@ static inline int compute_score(struct sock *sk, struct net *net,
 {
 	int score = -1;
 	struct inet_sock *inet = inet_sk(sk);
+	bool dev_match;
 
 	if (net_eq(sock_net(sk), net) && inet->inet_num == hnum &&
 			!ipv6_only_sock(sk)) {
@@ -245,15 +246,12 @@ static inline int compute_score(struct sock *sk, struct net *net,
 				return -1;
 			score += 4;
 		}
-		if (sk->sk_bound_dev_if || exact_dif) {
+		dev_match = inet_sk_bound_dev_eq(net, sk->sk_bound_dev_if,
-			bool dev_match = (sk->sk_bound_dev_if == dif ||
+						 dif, sdif);
-					  sk->sk_bound_dev_if == sdif);
+		if (!dev_match)
+			return -1;
+		score += 4;
 
-			if (!dev_match)
-				return -1;
-			if (sk->sk_bound_dev_if)
-				score += 4;
-		}
 		if (sk->sk_incoming_cpu == raw_smp_processor_id())
 			score++;
 	}

net/ipv6/inet6_hashtables.c

@@ -99,6 +99,7 @@ static inline int compute_score(struct sock *sk, struct net *net,
 				const int dif, const int sdif, bool exact_dif)
 {
 	int score = -1;
+	bool dev_match;
 
 	if (net_eq(sock_net(sk), net) && inet_sk(sk)->inet_num == hnum &&
 	    sk->sk_family == PF_INET6) {
@@ -109,15 +110,12 @@ static inline int compute_score(struct sock *sk, struct net *net,
 				return -1;
 			score++;
 		}
-		if (sk->sk_bound_dev_if || exact_dif) {
+		dev_match = inet_sk_bound_dev_eq(net, sk->sk_bound_dev_if,
-			bool dev_match = (sk->sk_bound_dev_if == dif ||
+						 dif, sdif);
-					  sk->sk_bound_dev_if == sdif);
+		if (!dev_match)
+			return -1;
+		score++;
 
-			if (!dev_match)
-				return -1;
-			if (sk->sk_bound_dev_if)
-				score++;
-		}
 		if (sk->sk_incoming_cpu == raw_smp_processor_id())
 			score++;
 	}