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mptcp: do not wakeup listener for MPJ subflows
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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 <dgilbert@redhat.com>
Fixes: f296234 ("mptcp: Add handling of incoming MP_JOIN requests")
Reviewed-by: Mat Martineau <mathew.j.martineau@linux.intel.com>
Signed-off-by: Paolo Abeni <pabeni@redhat.com>
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Paolo Abeni authored and jenkins-tessares committed Feb 23, 2021
1 parent 90faeb6 commit 7e873cb
Showing 1 changed file with 6 additions and 0 deletions.
6 changes: 6 additions & 0 deletions net/mptcp/subflow.c
Original file line number Diff line number Diff line change
Expand Up @@ -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;
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