From: Paolo Abeni pabeni@redhat.com
When __mptcp_retrans() kicks-in, it schedules one or more subflows for retransmission, but such subflows could be actually left alone if there is no more data to retransmit and/or in case of concurrent fallback.
Scheduled subflows could be processed much later in time, i.e. when new data will be transmitted, leading to bad subflow selection.
Explicitly clear all scheduled subflows before leaving the retransmission function.
Fixes: ee2708aedad0 ("mptcp: use get_retrans wrapper") Cc: stable@vger.kernel.org Reported-by: Filip Pokryvka fpokryvk@redhat.com Signed-off-by: Paolo Abeni pabeni@redhat.com Reviewed-by: Matthieu Baerts (NGI0) matttbe@kernel.org Signed-off-by: Matthieu Baerts (NGI0) matttbe@kernel.org --- net/mptcp/protocol.c | 13 +++++++++++-- 1 file changed, 11 insertions(+), 2 deletions(-)
diff --git a/net/mptcp/protocol.c b/net/mptcp/protocol.c index 33b5dce431c2..8abb425d8b5f 100644 --- a/net/mptcp/protocol.c +++ b/net/mptcp/protocol.c @@ -2665,7 +2665,7 @@ static void __mptcp_retrans(struct sock *sk) }
if (!mptcp_send_head(sk)) - return; + goto clear_scheduled;
goto reset_timer; } @@ -2696,7 +2696,7 @@ static void __mptcp_retrans(struct sock *sk) if (__mptcp_check_fallback(msk)) { spin_unlock_bh(&msk->fallback_lock); release_sock(ssk); - return; + goto clear_scheduled; }
while (info.sent < info.limit) { @@ -2728,6 +2728,15 @@ static void __mptcp_retrans(struct sock *sk)
if (!mptcp_rtx_timer_pending(sk)) mptcp_reset_rtx_timer(sk); + +clear_scheduled: + /* If no rtx data was available or in case of fallback, there + * could be left-over scheduled subflows; clear them all + * or later xmit could use bad ones + */ + mptcp_for_each_subflow(msk, subflow) + if (READ_ONCE(subflow->scheduled)) + mptcp_subflow_set_scheduled(subflow, false); }
/* schedule the timeout timer for the relevant event: either close timeout
--- base-commit: 4fe5a00ec70717a7f1002d8913ec6143582b3c8e change-id: 20251125-net-mptcp-clear-sched-rtx-a4eba7e4d5e1
Best regards,