Subject: [PATCH 31/38] tipc: allow to build NACK message in link timeout function

From: Tung Nguyen <[email-masked]>
Date: Tue, 21 Jul 2020 08:57:05 +0700

[ Upstream commit 6ef9dcb78046b346b5508ca1659848b136a343c2 ]

Commit 02288248b051 ("tipc: eliminate gap indicator from ACK messages")
eliminated sending of the 'gap' indicator in regular ACK messages and
only allowed to build NACK message with enabled probe/probe_reply.
However, necessary correction for building NACK message was missed
in tipc_link_timeout() function. This leads to significant delay and
link reset (due to retransmission failure) in lossy environment.

This commit fixes it by setting the 'probe' flag to 'true' when
the receive deferred queue is not empty. As a result, NACK message
will be built to send back to another peer.

Fixes: 02288248b051 ("tipc: eliminate gap indicator from ACK messages")
Acked-by: Jon Maloy <[email-masked]>
Signed-off-by: Tung Nguyen <[email-masked]>
Signed-off-by: David S. Miller <[email-masked]>
---
 net/tipc/link.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/net/tipc/link.c b/net/tipc/link.c
index d4675e922a8f..e18369201a15 100644
--- a/net/tipc/link.c
+++ b/net/tipc/link.c
@@ -813,11 +813,11 @@ int tipc_link_timeout(struct tipc_link *l, struct sk_buff_head *xmitq)
 		state |= l->bc_rcvlink->rcv_unacked;
 		state |= l->rcv_unacked;
 		state |= !skb_queue_empty(&l->transmq);
-		state |= !skb_queue_empty(&l->deferdq);
 		probe = mstate->probing;
 		probe |= l->silent_intv_cnt;
 		if (probe || mstate->monitoring)
 			l->silent_intv_cnt++;
+		probe |= !skb_queue_empty(&l->deferdq);
 		if (l->snd_nxt == l->checkpoint) {
 			tipc_link_update_cwin(l, 0, 0);
 			probe = true;
-- 
2.26.2