mptcp: mptcp: avoid additional indirection in mptcp_bind()

We are going to remove the first subflow socket soon, so avoid
the additional indirection via at bind() time. Instead call directly
the recently introduced helpers on the first subflow sock.

Signed-off-by: Paolo Abeni <[e-mail]>
Reviewed-by: Mat Martineau <[e-mail]>
Signed-off-by: Matthieu Baerts <[e-mail]>
Signed-off-by: David S. Miller <[e-mail]>

net/mptcp/protocol.c

···
 static int mptcp_bind(struct socket *sock, struct sockaddr *uaddr, int addr_len)
 {
 	struct mptcp_sock *msk = mptcp_sk(sock->sk);
+	struct sock *ssk, *sk = sock->sk;
 	struct socket *ssock;
-	int err;
+	int err = -EINVAL;
 
-	lock_sock(sock->sk);
+	lock_sock(sk);
 	ssock = __mptcp_nmpc_socket(msk);
 	if (IS_ERR(ssock)) {
 		err = PTR_ERR(ssock);
 		goto unlock;
 	}
 
-	err = READ_ONCE(ssock->ops)->bind(ssock, uaddr, addr_len);
+	ssk = msk->first;
+	if (sk->sk_family == AF_INET)
+		err = inet_bind_sk(ssk, uaddr, addr_len);
+#if IS_ENABLED(CONFIG_MPTCP_IPV6)
+	else if (sk->sk_family == AF_INET6)
+		err = inet6_bind_sk(ssk, uaddr, addr_len);
+#endif
 	if (!err)
-		mptcp_copy_inaddrs(sock->sk, ssock->sk);
+		mptcp_copy_inaddrs(sk, ssk);
 
 unlock:
-	release_sock(sock->sk);
+	release_sock(sk);
 	return err;
 }