subflow: wake parent mptcp socket on subflow state change

We need to wakeup readers blocking for POLLIN, as no
more data will arrive they will never be awoken otherwise.

This is needed at least until proper MPTCP-Level fin/reset
signalling gets added.

Signed-off-by: Florian Westphal <[email protected]>

net/mptcp/subflow.c

@@ -722,6 +722,28 @@ static struct mptcp_subflow_context *subflow_create_ctx(struct sock *sk,
 	return ctx;
 }
 
+static void __subflow_state_change(struct sock *sk)
+{
+	struct socket_wq *wq;
+
+	rcu_read_lock();
+	wq = rcu_dereference(sk->sk_wq);
+	if (skwq_has_sleeper(wq))
+		wake_up_interruptible_all(&wq->wait);
+	rcu_read_unlock();
+}
+
+static void subflow_state_change(struct sock *sk)
+{
+	struct mptcp_subflow_context *subflow = mptcp_subflow_ctx(sk);
+	struct sock *parent = subflow->conn;
+
+	__subflow_state_change(sk);
+
+	if (parent)
+		__subflow_state_change(parent);
+}
+
 static int subflow_ulp_init(struct sock *sk)
 {
 	struct inet_connection_sock *icsk = inet_csk(sk);
@@ -750,6 +772,7 @@ static int subflow_ulp_init(struct sock *sk)
 	ctx->tcp_sk_data_ready = sk->sk_data_ready;
 	sk->sk_data_ready = subflow_data_ready;
 	sk->sk_write_space = subflow_write_space;
+	sk->sk_state_change = subflow_state_change;
 out:
 	return err;
 }