6.6-stable review patch. If anyone has any objections, please let me know.
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From: Paolo Abeni pabeni@redhat.com
commit 2ea6190f42d0416a4310e60a7fcb0b49fcbbd4fb upstream.
The MPTCP protocol usually schedule the retransmission timer only when there is some chances for such retransmissions to happen.
With a notable exception: __mptcp_push_pending() currently schedule such timer unconditionally, potentially leading to unnecessary rtx timer expiration.
The issue is present since the blamed commit below but become easily reproducible after commit 27b0e701d387 ("mptcp: drop bogus optimization in __mptcp_check_push()")
Fixes: 33d41c9cd74c ("mptcp: more accurate timeout") Cc: stable@vger.kernel.org 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 Link: https://patch.msgid.link/20251205-net-mptcp-misc-fixes-6-19-rc1-v1-3-9e4781a... Signed-off-by: Jakub Kicinski kuba@kernel.org Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- net/mptcp/protocol.c | 15 +++++++++------ 1 file changed, 9 insertions(+), 6 deletions(-)
--- a/net/mptcp/protocol.c +++ b/net/mptcp/protocol.c @@ -1630,7 +1630,7 @@ void __mptcp_push_pending(struct sock *s struct mptcp_sendmsg_info info = { .flags = flags, }; - bool do_check_data_fin = false; + bool copied = false; int push_count = 1;
while (mptcp_send_head(sk) && (push_count > 0)) { @@ -1672,7 +1672,7 @@ void __mptcp_push_pending(struct sock *s push_count--; continue; } - do_check_data_fin = true; + copied = true; } } } @@ -1681,11 +1681,14 @@ void __mptcp_push_pending(struct sock *s if (ssk) mptcp_push_release(ssk, &info);
- /* ensure the rtx timer is running */ - if (!mptcp_rtx_timer_pending(sk)) - mptcp_reset_rtx_timer(sk); - if (do_check_data_fin) + /* Avoid scheduling the rtx timer if no data has been pushed; the timer + * will be updated on positive acks by __mptcp_cleanup_una(). + */ + if (copied) { + if (!mptcp_rtx_timer_pending(sk)) + mptcp_reset_rtx_timer(sk); mptcp_check_send_data_fin(sk); + } }
static void __mptcp_subflow_push_pending(struct sock *sk, struct sock *ssk, bool first)