This is a note to let you know that I've just added the patch titled
tipc: fix incorrect increasing of link window
to the 5.6-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
tipc-fix-incorrect-increasing-of-link-window.patch
and it can be found in the queue-5.6 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
commit 3d088b18cce20272bc4ebb1bbc52aa7379547d07
Author: Tuong Lien <tuong.t.lien@xxxxxxxxxxxxxx>
Date: Wed Apr 15 18:34:49 2020 +0700
tipc: fix incorrect increasing of link window
commit edadedf1c5b4e4404192a0a4c3c0c05e3b7672ab upstream.
In commit 16ad3f4022bb ("tipc: introduce variable window congestion
control"), we allow link window to change with the congestion avoidance
algorithm. However, there is a bug that during the slow-start if packet
retransmission occurs, the link will enter the fast-recovery phase, set
its window to the 'ssthresh' which is never less than 300, so the link
window suddenly increases to that limit instead of decreasing.
Consequently, two issues have been observed:
- For broadcast-link: it can leave a gap between the link queues that a
new packet will be inserted and sent before the previous ones, i.e. not
in-order.
- For unicast: the algorithm does not work as expected, the link window
jumps to the slow-start threshold whereas packet retransmission occurs.
This commit fixes the issues by avoiding such the link window increase,
but still decreasing if the 'ssthresh' is lowered.
Fixes: 16ad3f4022bb ("tipc: introduce variable window congestion control")
Acked-by: Jon Maloy <jmaloy@xxxxxxxxxx>
Signed-off-by: Tuong Lien <tuong.t.lien@xxxxxxxxxxxxxx>
Signed-off-by: David S. Miller <davem@xxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
diff --git a/net/tipc/link.c b/net/tipc/link.c
index 467c53a1fb5cf..d4675e922a8f7 100644
--- a/net/tipc/link.c
+++ b/net/tipc/link.c
@@ -1065,7 +1065,7 @@ static void tipc_link_update_cwin(struct tipc_link *l, int released,
/* Enter fast recovery */
if (unlikely(retransmitted)) {
l->ssthresh = max_t(u16, l->window / 2, 300);
- l->window = l->ssthresh;
+ l->window = min_t(u16, l->ssthresh, l->window);
return;
}
/* Enter slow start */
