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mptcp: schedule rtx timer only after pushing data

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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 27b0e701d3 ("mptcp: drop bogus optimization
in __mptcp_check_push()")

Fixes: 33d41c9cd7 ("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-v1-3-9e4781a6c1b8@kernel.org
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
This commit is contained in:
Paolo Abeni
2025-12-05 19:55:16 +01:00
committed by Jakub Kicinski
parent 29f4801e9c
commit 2ea6190f42
1 changed files with 9 additions and 6 deletions
Download Patch File Download Diff File Expand all files Collapse all files

15
net/mptcp/protocol.c
View File

@@ -1623,7 +1623,7 @@ void __mptcp_push_pending(struct sock *sk, unsigned int flags)
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)) {
@@ -1665,7 +1665,7 @@ void __mptcp_push_pending(struct sock *sk, unsigned int flags)
push_count--;
continue;
}
do_check_data_fin = true;
copied = true;
}
}
}
@@ -1674,11 +1674,14 @@ void __mptcp_push_pending(struct sock *sk, unsigned int flags)
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)