mptcp: do not wakeup listener for MPJ subflows

MPJ subflows are not exposed as fds to user spaces. As such, incoming MPJ subflows are removed from the accept queue by tcp_check_req()/tcp_get_cookie_sock(). Later tcp_child_process() invokes subflow_data_ready() on the parent socket regardless of the subflow kind, leading to poll wakeups even if the later accept will block. Address the issue double checking the queue state before waking the user-space. Closes: #164 Reported-by: Dr. David Alan Gilbert <[email protected]> Fixes: f296234 ("mptcp: Add handling of incoming MP_JOIN requests") Reviewed-by: Mat Martineau <[email protected]> Signed-off-by: Paolo Abeni <[email protected]>
multipath-tcp · Feb 23, 2021 · d1581f4 · d1581f4
1 parent b578f6c
commit d1581f4
Showing 1 changed file with 6 additions and 0 deletions.
diff --git a/net/mptcp/subflow.c b/net/mptcp/subflow.c
@@ -1096,6 +1096,12 @@ static void subflow_data_ready(struct sock *sk)
 
 	msk = mptcp_sk(parent);
 	if (state & TCPF_LISTEN) {
+		/* MPJ subflow are removed from accept queue before reaching here,
+		 * avoid stray wakeups
+		 */
+		if (reqsk_queue_empty(&inet_csk(sk)->icsk_accept_queue))
+			return;
+
 		set_bit(MPTCP_DATA_READY, &msk->flags);
 		parent->sk_data_ready(parent);
 		return;