netdev - [net-next 1/1] tipc: simplify stale link failure criteria

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Date:   Tue, 25 Jun 2019 17:36:43 +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-next  1/1] tipc: simplify stale link failure criteria

In commit a4dc70d46cf1 ("tipc: extend link reset criteria for stale
packet retransmission") we made link retransmission failure events
dependent on the link tolerance, and not only of the number of failed
retransmission attempts, as we did earlier. This works well. However,
keeping the original, additional criteria of 99 failed retransmissions
is now redundant, and may in some cases lead to failure detection
times in the order of minutes instead of the expected 1.5 sec link
tolerance value.

We now remove this criteria altogether.

Acked-by: Ying Xue <ying.xue@...driver.com>
Signed-off-by: Jon Maloy <jon.maloy@...csson.com>
---
 net/tipc/link.c | 9 ++-------
 1 file changed, 2 insertions(+), 7 deletions(-)

diff --git a/net/tipc/link.c b/net/tipc/link.c
index bcfb0a4..af50b53 100644
--- a/net/tipc/link.c
+++ b/net/tipc/link.c
@@ -107,7 +107,6 @@ struct tipc_stats {
  * @backlogq: queue for messages waiting to be sent
  * @snt_nxt: next sequence number to use for outbound messages
  * @prev_from: sequence number of most previous retransmission request
- * @stale_cnt: counter for number of identical retransmit attempts
  * @stale_limit: time when repeated identical retransmits must force link reset
  * @ackers: # of peers that needs to ack each packet before it can be released
  * @acked: # last packet acked by a certain peer. Used for broadcast.
@@ -167,7 +166,6 @@ struct tipc_link {
 	u16 snd_nxt;
 	u16 prev_from;
 	u16 window;
-	u16 stale_cnt;
 	unsigned long stale_limit;
 
 	/* Reception */
@@ -910,7 +908,6 @@ void tipc_link_reset(struct tipc_link *l)
 	l->acked = 0;
 	l->silent_intv_cnt = 0;
 	l->rst_cnt = 0;
-	l->stale_cnt = 0;
 	l->bc_peer_is_up = false;
 	memset(&l->mon_state, 0, sizeof(l->mon_state));
 	tipc_link_reset_stats(l);
@@ -1068,8 +1065,7 @@ static bool link_retransmit_failure(struct tipc_link *l, struct tipc_link *r,
 	if (r->prev_from != from) {
 		r->prev_from = from;
 		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)) {
+	} else if (time_after(jiffies, r->stale_limit)) {
 		pr_warn("Retransmission failure on link <%s>\n", l->name);
 		link_print(l, "State of link ");
 		pr_info("Failed msg: usr %u, typ %u, len %u, err %u\n",
@@ -1515,7 +1511,6 @@ int tipc_link_rcv(struct tipc_link *l, struct sk_buff *skb,
 
 		/* Forward queues and wake up waiting users */
 		if (likely(tipc_link_release_pkts(l, msg_ack(hdr)))) {
-			l->stale_cnt = 0;
 			tipc_link_advance_backlog(l, xmitq);
 			if (unlikely(!skb_queue_empty(&l->wakeupq)))
 				link_prepare_wakeup(l);
@@ -2584,7 +2579,7 @@ int tipc_link_dump(struct tipc_link *l, u16 dqueues, char *buf)
 	i += scnprintf(buf + i, sz - i, " %u", l->silent_intv_cnt);
 	i += scnprintf(buf + i, sz - i, " %u", l->rst_cnt);
 	i += scnprintf(buf + i, sz - i, " %u", l->prev_from);
-	i += scnprintf(buf + i, sz - i, " %u", l->stale_cnt);
+	i += scnprintf(buf + i, sz - i, " %u", 0);
 	i += scnprintf(buf + i, sz - i, " %u", l->acked);
 
 	list = &l->transmq;
-- 
2.1.4