From: Paolo Abeni <[email protected]>
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: [email protected]
Signed-off-by: Paolo Abeni <[email protected]>
Reviewed-by: Matthieu Baerts (NGI0) <[email protected]>
Signed-off-by: Matthieu Baerts (NGI0) <[email protected]>
---
net/mptcp/protocol.c | 15 +++++++++------
1 file changed, 9 insertions(+), 6 deletions(-)
diff --git a/net/mptcp/protocol.c b/net/mptcp/protocol.c
index e212c1374bd0..d8a7f7029164 100644
--- a/net/mptcp/protocol.c
+++ b/net/mptcp/protocol.c
@@ -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)
--
2.51.0
