[PATCH net] neigh: fix ARP retransmit timer guard

[PATCH net] neigh: fix ARP retransmit timer guard

[Hangbin Liu]

In commit 19e16d220f0a ("neigh: support smaller retrans_time settting")
we add more accurate control for ARP and NS. But for ARP I forgot to
update the latest guard in neigh_timer_handler(), then the next
retransmit would be reset to jiffies + HZ/2 if we set the retrans_time
less than 500ms. Fix it by setting the time_before() check to HZ/100.

IPv6 does not have this issue.

Reported-by: Jianwen Ji <jiji@redhat.com>
Fixes: 19e16d220f0a ("neigh: support smaller retrans_time settting")
Signed-off-by: Hangbin Liu <liuhangbin@gmail.com>
---
 net/core/neighbour.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/net/core/neighbour.c b/net/core/neighbour.c
index 116139233d57..dbe0c6ead773 100644
--- a/net/core/neighbour.c
+++ b/net/core/neighbour.c
@@ -1082,8 +1082,8 @@ static void neigh_timer_handler(struct timer_list *t)
 	}
 
 	if (neigh->nud_state & NUD_IN_TIMER) {
-		if (time_before(next, jiffies + HZ/2))
-			next = jiffies + HZ/2;
+		if (time_before(next, jiffies + HZ/100))
+			next = jiffies + HZ/100;
 		if (!mod_timer(&neigh->timer, next))
 			neigh_hold(neigh);
 	}
-- 
2.25.4

Re: [PATCH net] neigh: fix ARP retransmit timer guard

[David Miller]

From: Hangbin Liu <liuhangbin@gmail.com>
Date: Thu, 28 May 2020 15:15:13 +0800

> In commit 19e16d220f0a ("neigh: support smaller retrans_time settting")
> we add more accurate control for ARP and NS. But for ARP I forgot to
> update the latest guard in neigh_timer_handler(), then the next
> retransmit would be reset to jiffies + HZ/2 if we set the retrans_time
> less than 500ms. Fix it by setting the time_before() check to HZ/100.
> 
> IPv6 does not have this issue.
> 
> Reported-by: Jianwen Ji <jiji@redhat.com>
> Fixes: 19e16d220f0a ("neigh: support smaller retrans_time settting")
> Signed-off-by: Hangbin Liu <liuhangbin@gmail.com>

Applied, thank you.