mptcp: create first subflow at msk creation time

This cleans the code a bit and makes the behavior more consistent.
Signed-off-by: NPaolo Abeni <pabeni@redhat.com>
Signed-off-by: NDavide Caratti <dcaratti@redhat.com>
Reviewed-by: NMat Martineau <mathew.j.martineau@linux.intel.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

net/mptcp/protocol.c

@@ -86,32 +86,16 @@ static struct socket *__mptcp_tcp_fallback(struct mptcp_sock *msk)
 	return msk->subflow;
 }
 
-static bool __mptcp_can_create_subflow(const struct mptcp_sock *msk)
-{
-	return !msk->first;
-}
-
-static struct socket *__mptcp_socket_create(struct mptcp_sock *msk, int state)
+static int __mptcp_socket_create(struct mptcp_sock *msk)
 {
 	struct mptcp_subflow_context *subflow;
 	struct sock *sk = (struct sock *)msk;
 	struct socket *ssock;
 	int err;
 
-	ssock = __mptcp_tcp_fallback(msk);
-	if (unlikely(ssock))
-		return ssock;
-
-	ssock = __mptcp_nmpc_socket(msk);
-	if (ssock)
-		goto set_state;
-
-	if (!__mptcp_can_create_subflow(msk))
-		return ERR_PTR(-EINVAL);
-
 	err = mptcp_subflow_create_socket(sk, &ssock);
 	if (err)
-		return ERR_PTR(err);
+		return err;
 
 	msk->first = ssock->sk;
 	msk->subflow = ssock;
@@ -124,10 +108,7 @@ static struct socket *__mptcp_socket_create(struct mptcp_sock *msk, int state)
 	 */
 	RCU_INIT_POINTER(msk->first->sk_wq, &sk->sk_socket->wq);
 
-set_state:
-	if (state != MPTCP_SAME_STATE)
-		inet_sk_state_store(sk, state);
-	return ssock;
+	return 0;
 }
 
 static void __mptcp_move_skb(struct mptcp_sock *msk, struct sock *ssk,
@@ -1255,6 +1236,10 @@ static int mptcp_init_sock(struct sock *sk)
 	if (ret)
 		return ret;
 
+	ret = __mptcp_socket_create(mptcp_sk(sk));
+	if (ret)
+		return ret;
+
 	sk_sockets_allocated_inc(sk);
 	sk->sk_sndbuf = sock_net(sk)->ipv4.sysctl_tcp_wmem[2];
 
@@ -1744,9 +1729,9 @@ static int mptcp_bind(struct socket *sock, struct sockaddr *uaddr, int addr_len)
 	int err;
 
 	lock_sock(sock->sk);
-	ssock = __mptcp_socket_create(msk, MPTCP_SAME_STATE);
-	if (IS_ERR(ssock)) {
-		err = PTR_ERR(ssock);
+	ssock = __mptcp_nmpc_socket(msk);
+	if (!ssock) {
+		err = -EINVAL;
 		goto unlock;
 	}
 
@@ -1776,13 +1761,14 @@ static int mptcp_stream_connect(struct socket *sock, struct sockaddr *uaddr,
 		goto do_connect;
 	}
 
-	mptcp_token_destroy(msk);
-	ssock = __mptcp_socket_create(msk, TCP_SYN_SENT);
-	if (IS_ERR(ssock)) {
-		err = PTR_ERR(ssock);
+	ssock = __mptcp_nmpc_socket(msk);
+	if (!ssock) {
+		err = -EINVAL;
 		goto unlock;
 	}
 
+	mptcp_token_destroy(msk);
+	inet_sk_state_store(sock->sk, TCP_SYN_SENT);
 	subflow = mptcp_subflow_ctx(ssock->sk);
 #ifdef CONFIG_TCP_MD5SIG
 	/* no MPTCP if MD5SIG is enabled on this socket or we may run out of
@@ -1820,13 +1806,14 @@ static int mptcp_listen(struct socket *sock, int backlog)
 	pr_debug("msk=%p", msk);
 
 	lock_sock(sock->sk);
-	mptcp_token_destroy(msk);
-	ssock = __mptcp_socket_create(msk, TCP_LISTEN);
-	if (IS_ERR(ssock)) {
-		err = PTR_ERR(ssock);
+	ssock = __mptcp_nmpc_socket(msk);
+	if (!ssock) {
+		err = -EINVAL;
 		goto unlock;
 	}
 
+	mptcp_token_destroy(msk);
+	inet_sk_state_store(sock->sk, TCP_LISTEN);
 	sock_set_flag(sock->sk, SOCK_RCU_FREE);
 
 	err = ssock->ops->listen(ssock, backlog);