[tipc-discussion] [net v1 1/1] tipc: allow to build NACK message in link timeout function

[tipc-discussion] [net v1 1/1] tipc: allow to build NACK message in link timeout function

[Tung Nguyen]

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: commit 02288248b051 ("tipc: eliminate gap indicator from ACK messages")
Acked-by: Jon Maloy <jmaloy@redhat.com>
Signed-off-by: Tung Nguyen <tung.q.nguyen@dektech.com.au>
---
 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 263d950e70e9..d40f8e5b7683 100644
--- a/net/tipc/link.c
+++ b/net/tipc/link.c
@@ -827,11 +827,11 @@ 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;
-- 
2.17.1

Re: [tipc-discussion] [net v1 1/1] tipc: allow to build NACK message in link timeout function

[David Miller]

From: Tung Nguyen <tung.q.nguyen@dektech.com.au>
Date: Tue, 21 Jul 2020 08:57:05 +0700

> 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: commit 02288248b051 ("tipc: eliminate gap indicator from ACK messages")

"commit" doesn't belong here, I removed it when I applied your patch.

> Acked-by: Jon Maloy <jmaloy@redhat.com>
> Signed-off-by: Tung Nguyen <tung.q.nguyen@dektech.com.au>

Applied and queued up for -stable, thanks.