inet: returns a bool from inet_sk_get_local_port_range()

Change inet_sk_get_local_port_range() to return a boolean,
telling the callers if the port range was provided by
IP_LOCAL_PORT_RANGE socket option.

Adds documentation while we are at it.

Signed-off-by: Eric Dumazet <edumazet@google.com>
Reviewed-by: Kuniyuki Iwashima <kuniyu@amazon.com>
Link: https://lore.kernel.org/r/20231214192939.1962891-2-edumazet@google.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

include/net/ip.h

@@ -356,7 +356,7 @@ static inline void inet_get_local_port_range(const struct net *net, int *low, in
 	*low = range & 0xffff;
 	*high = range >> 16;
 }
-void inet_sk_get_local_port_range(const struct sock *sk, int *low, int *high);
+bool inet_sk_get_local_port_range(const struct sock *sk, int *low, int *high);
 
 #ifdef CONFIG_SYSCTL
 static inline bool inet_is_local_reserved_port(struct net *net, unsigned short port)

net/ipv4/inet_connection_sock.c

@@ -117,16 +117,25 @@ bool inet_rcv_saddr_any(const struct sock *sk)
 	return !sk->sk_rcv_saddr;
 }
 
-void inet_sk_get_local_port_range(const struct sock *sk, int *low, int *high)
+/**
+ *	inet_sk_get_local_port_range - fetch ephemeral ports range
+ *	@sk: socket
+ *	@low: pointer to low port
+ *	@high: pointer to high port
+ *
+ *	Fetch netns port range (/proc/sys/net/ipv4/ip_local_port_range)
+ *	Range can be overridden if socket got IP_LOCAL_PORT_RANGE option.
+ *	Returns true if IP_LOCAL_PORT_RANGE was set on this socket.
+ */
+bool inet_sk_get_local_port_range(const struct sock *sk, int *low, int *high)
 {
-	const struct inet_sock *inet = inet_sk(sk);
-	const struct net *net = sock_net(sk);
 	int lo, hi, sk_lo, sk_hi;
+	bool local_range = false;
 	u32 sk_range;
 
-	inet_get_local_port_range(net, &lo, &hi);
+	inet_get_local_port_range(sock_net(sk), &lo, &hi);
 
-	sk_range = READ_ONCE(inet->local_port_range);
+	sk_range = READ_ONCE(inet_sk(sk)->local_port_range);
 	if (unlikely(sk_range)) {
 		sk_lo = sk_range & 0xffff;
 		sk_hi = sk_range >> 16;
@@ -135,10 +144,12 @@ void inet_sk_get_local_port_range(const struct sock *sk, int *low, int *high)
 			lo = sk_lo;
 		if (lo <= sk_hi && sk_hi <= hi)
 			hi = sk_hi;
+		local_range = true;
 	}
 
 	*low = lo;
 	*high = hi;
+	return local_range;
 }
 EXPORT_SYMBOL(inet_sk_get_local_port_range);