tcp: metrics: Handle v6/v4-mapped sockets in tcp-metrics

A socket may be v6/v4-mapped. In that case sk->sk_family is AF_INET6,
but the IP being used is actually an IPv4-address.
Current's tcp-metrics will thus represent it as an IPv6-address:

root@server:~# ip tcp_metrics
::ffff:10.1.1.2 age 22.920sec rtt 18750us rttvar 15000us cwnd 10
10.1.1.2 age 47.970sec rtt 16250us rttvar 10000us cwnd 10

This patch modifies the tcp-metrics so that they are able to handle the
v6/v4-mapped sockets correctly.
Signed-off-by: Christoph Paasch <christoph.paasch@uclouvain.be>
Acked-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/ipv4/tcp_metrics.c

@@ -274,24 +274,32 @@ static struct tcp_metrics_block *__tcp_get_metrics_tw(struct inet_timewait_sock
 	unsigned int hash;
 	struct net *net;
 
-	saddr.family = tw->tw_family;
-	daddr.family = tw->tw_family;
-	switch (daddr.family) {
-	case AF_INET:
+	if (tw->tw_family == AF_INET) {
+		saddr.family = AF_INET;
 		saddr.addr.a4 = tw->tw_rcv_saddr;
+		daddr.family = AF_INET;
 		daddr.addr.a4 = tw->tw_daddr;
 		hash = (__force unsigned int) daddr.addr.a4;
-		break;
+	}
 #if IS_ENABLED(CONFIG_IPV6)
-	case AF_INET6:
-		*(struct in6_addr *)saddr.addr.a6 = tw->tw_v6_rcv_saddr;
-		*(struct in6_addr *)daddr.addr.a6 = tw->tw_v6_daddr;
-		hash = ipv6_addr_hash(&tw->tw_v6_daddr);
-		break;
+	else if (tw->tw_family == AF_INET6) {
+		if (ipv6_addr_v4mapped(&tw->tw_v6_daddr)) {
+			saddr.family = AF_INET;
+			saddr.addr.a4 = tw->tw_rcv_saddr;
+			daddr.family = AF_INET;
+			daddr.addr.a4 = tw->tw_daddr;
+			hash = (__force unsigned int) daddr.addr.a4;
+		} else {
+			saddr.family = AF_INET6;
+			*(struct in6_addr *)saddr.addr.a6 = tw->tw_v6_rcv_saddr;
+			daddr.family = AF_INET6;
+			*(struct in6_addr *)daddr.addr.a6 = tw->tw_v6_daddr;
+			hash = ipv6_addr_hash(&tw->tw_v6_daddr);
+		}
+	}
 #endif
-	default:
+	else
 		return NULL;
-	}
 
 	net = twsk_net(tw);
 	hash = hash_32(hash, net->ipv4.tcp_metrics_hash_log);
@@ -314,24 +322,32 @@ static struct tcp_metrics_block *tcp_get_metrics(struct sock *sk,
 	unsigned int hash;
 	struct net *net;
 
-	saddr.family = sk->sk_family;
-	daddr.family = sk->sk_family;
-	switch (daddr.family) {
-	case AF_INET:
+	if (sk->sk_family == AF_INET) {
+		saddr.family = AF_INET;
 		saddr.addr.a4 = inet_sk(sk)->inet_saddr;
+		daddr.family = AF_INET;
 		daddr.addr.a4 = inet_sk(sk)->inet_daddr;
 		hash = (__force unsigned int) daddr.addr.a4;
-		break;
+	}
 #if IS_ENABLED(CONFIG_IPV6)
-	case AF_INET6:
-		*(struct in6_addr *)saddr.addr.a6 = sk->sk_v6_rcv_saddr;
-		*(struct in6_addr *)daddr.addr.a6 = sk->sk_v6_daddr;
-		hash = ipv6_addr_hash(&sk->sk_v6_daddr);
-		break;
+	else if (sk->sk_family == AF_INET6) {
+		if (ipv6_addr_v4mapped(&sk->sk_v6_daddr)) {
+			saddr.family = AF_INET;
+			saddr.addr.a4 = inet_sk(sk)->inet_saddr;
+			daddr.family = AF_INET;
+			daddr.addr.a4 = inet_sk(sk)->inet_daddr;
+			hash = (__force unsigned int) daddr.addr.a4;
+		} else {
+			saddr.family = AF_INET6;
+			*(struct in6_addr *)saddr.addr.a6 = sk->sk_v6_rcv_saddr;
+			daddr.family = AF_INET6;
+			*(struct in6_addr *)daddr.addr.a6 = sk->sk_v6_daddr;
+			hash = ipv6_addr_hash(&sk->sk_v6_daddr);
+		}
+	}
 #endif
-	default:
+	else
 		return NULL;
-	}
 
 	net = dev_net(dst->dev);
 	hash = hash_32(hash, net->ipv4.tcp_metrics_hash_log);