net: Return errno in sk->sk_prot->get_port().

Bugzilla: https://bugzilla.redhat.com/show_bug.cgi?id=2166482
Tested: vs bz reproducer
Conflicts: different context in inet_csk_get_port and udp_lib_get_port,\
  as rhel-9 lacks the upstream commit 08eaef9 ("tcp: Clean up \
  some functions.") and upstream commit 919dfa0 ("udp: Clean up \
  some functions.")

Upstream commit:
commit 7a7160e
Author: Kuniyuki Iwashima <kuniyu@amazon.com>
Date:   Fri Nov 18 10:25:06 2022 -0800

    net: Return errno in sk->sk_prot->get_port().

    We assume the correct errno is -EADDRINUSE when sk->sk_prot->get_port()
    fails, so some ->get_port() functions return just 1 on failure and the
    callers return -EADDRINUSE instead.

    However, mptcp_get_port() can return -EINVAL.  Let's not ignore the error.

    Note the only exception is inet_autobind(), all of whose callers return
    -EAGAIN instead.

    Fixes: cec37a6 ("mptcp: Handle MP_CAPABLE options for outgoing connections")
    Signed-off-by: Kuniyuki Iwashima <kuniyu@amazon.com>
    Signed-off-by: David S. Miller <davem@davemloft.net>

Signed-off-by: Paolo Abeni <pabeni@redhat.com>

Author: Paolo Abeni

net/ipv4/af_inet.c

@@ -525,9 +525,9 @@ int __inet_bind(struct sock *sk, struct sockaddr *uaddr, int addr_len,
 	/* Make sure we are allowed to bind here. */
 	if (snum || !(inet->bind_address_no_port ||
 		      (flags & BIND_FORCE_ADDRESS_NO_PORT))) {
-		if (sk->sk_prot->get_port(sk, snum)) {
+		err = sk->sk_prot->get_port(sk, snum);
+		if (err) {
 			inet->inet_saddr = inet->inet_rcv_saddr = 0;
-			err = -EADDRINUSE;
 			goto out_release_sock;
 		}
 		if (!(flags & BIND_FROM_BPF)) {

net/ipv4/inet_connection_sock.c

@@ -367,7 +367,7 @@ int inet_csk_get_port(struct sock *sk, unsigned short snum)
 {
 	bool reuse = sk->sk_reuse && sk->sk_state != TCP_LISTEN;
 	struct inet_hashinfo *hinfo = sk->sk_prot->h.hashinfo;
-	int ret = 1, port = snum;
+	int ret = -EADDRINUSE, port = snum;
 	struct inet_bind_hashbucket *head;
 	struct net *net = sock_net(sk);
 	struct inet_bind_bucket *tb = NULL;
@@ -1054,7 +1054,7 @@ int inet_csk_listen_start(struct sock *sk, int backlog)
 {
 	struct inet_connection_sock *icsk = inet_csk(sk);
 	struct inet_sock *inet = inet_sk(sk);
-	int err = -EADDRINUSE;
+	int err;
 
 	err = inet_ulp_can_listen(sk);
 	if (unlikely(err))
@@ -1074,7 +1074,8 @@ int inet_csk_listen_start(struct sock *sk, int backlog)
 	 * after validation is complete.
 	 */
 	inet_sk_state_store(sk, TCP_LISTEN);
-	if (!sk->sk_prot->get_port(sk, inet->inet_num)) {
+	err = sk->sk_prot->get_port(sk, inet->inet_num);
+	if (!err) {
 		inet->inet_sport = htons(inet->inet_num);
 
 		sk_dst_reset(sk);

net/ipv4/ping.c

@@ -142,7 +142,7 @@ int ping_get_port(struct sock *sk, unsigned short ident)
 
 fail:
 	spin_unlock(&ping_table.lock);
-	return 1;
+	return -EADDRINUSE;
 }
 EXPORT_SYMBOL_GPL(ping_get_port);
 

net/ipv4/udp.c

@@ -234,8 +234,8 @@ int udp_lib_get_port(struct sock *sk, unsigned short snum,
 {
 	struct udp_hslot *hslot, *hslot2;
 	struct udp_table *udptable = sk->sk_prot->h.udp_table;
-	int    error = 1;
 	struct net *net = sock_net(sk);
+	int error = -EADDRINUSE;
 
 	if (!snum) {
 		int low, high, remaining;

net/ipv6/af_inet6.c

@@ -411,10 +411,10 @@ static int __inet6_bind(struct sock *sk, struct sockaddr *uaddr, int addr_len,
 	/* Make sure we are allowed to bind here. */
 	if (snum || !(inet->bind_address_no_port ||
 		      (flags & BIND_FORCE_ADDRESS_NO_PORT))) {
-		if (sk->sk_prot->get_port(sk, snum)) {
+		err = sk->sk_prot->get_port(sk, snum);
+		if (err) {
 			sk->sk_ipv6only = saved_ipv6only;
 			inet_reset_saddr(sk);
-			err = -EADDRINUSE;
 			goto out;
 		}
 		if (!(flags & BIND_FROM_BPF)) {