netdev - [net 1/1] tipc: initialize broadcast link stale counter correctly

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Message-ID: <1539288149-24122-1-git-send-email-jon.maloy@ericsson.com>
Date:   Thu, 11 Oct 2018 22:02:29 +0200
From:   Jon Maloy <jon.maloy@...csson.com>
To:     <davem@...emloft.net>, <netdev@...r.kernel.org>
CC:     <gordan.mihaljevic@...tech.com.au>, <tung.q.nguyen@...tech.com.au>,
        <hoang.h.le@...tech.com.au>, <jon.maloy@...csson.com>,
        <canh.d.luu@...tech.com.au>, <ying.xue@...driver.com>,
        <tipc-discussion@...ts.sourceforge.net>
Subject: [net  1/1] tipc: initialize broadcast link stale counter correctly

In the commit referred to below we added link tolerance as an additional
criteria for declaring broadcast transmission "stale" and resetting the
unicast links to the affected node.

Unfortunately, this 'improvement' introduced two bugs, which each and
one alone cause only limited problems, but combined lead to seemingly
stochastic unicast link resets, depending on the amount of broadcast
traffic transmitted.

The first issue, a missing initialization of the 'tolerance' field of
the receiver broadcast link, was recently fixed by commit 047491ea334a
("tipc: set link tolerance correctly in broadcast link").

Ths second issue, where we omit to reset the 'stale_cnt' field of
the same link after a 'stale' period is over, leads to this counter
accumulating over time, and in the absence of the 'tolerance' criteria
leads to the above described symptoms. This commit adds the missing
initialization.

Fixes: a4dc70d46cf1 ("tipc: extend link reset criteria for stale packet
retransmission")

Signed-off-by: Jon Maloy <jon.maloy@...csson.com>
---
 net/tipc/link.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/net/tipc/link.c b/net/tipc/link.c
index f6552e4..201c3b5 100644
--- a/net/tipc/link.c
+++ b/net/tipc/link.c
@@ -1041,6 +1041,7 @@ static int tipc_link_retrans(struct tipc_link *l, struct tipc_link *r,
 	if (r->last_retransm != buf_seqno(skb)) {
 		r->last_retransm = buf_seqno(skb);
 		r->stale_limit = jiffies + msecs_to_jiffies(r->tolerance);
+		r->stale_cnt = 0;
 	} else if (++r->stale_cnt > 99 && time_after(jiffies, r->stale_limit)) {
 		link_retransmit_failure(l, skb);
 		if (link_is_bc_sndlink(l))
-- 
2.1.4