netdev - [PATCH net-next (v2, reword)] neigh: Keep neighbour cache entries if number of them is small enough.

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [thread-next>] [day] [month] [year] [list]

Message-ID: <50FEAE25.4040008@linux-ipv6.org>
Date:	Wed, 23 Jan 2013 00:20:05 +0900
From:	YOSHIFUJI Hideaki <yoshfuji@...ux-ipv6.org>
To:	davem@...emloft.net, netdev@...r.kernel.org
CC:	yoshfuji@...ux-ipv6.org
Subject: [PATCH net-next (v2, reword)] neigh: Keep neighbour cache entries
 if number of them is small enough.

Since we have removed NCE (Neighbour Cache Entry) reference from
routing entries, the only refcnt holders of an NCE are its timer
(if running) and its owner table, in usual cases.  As a result,
neigh_periodic_work() purges NCEs over and over again even for
gateways.

It does not make sense to purge entries, if number of them is
very small, so keep them.  The minimum number of entries to keep
is specified by gc_thresh1.

Signed-off-by: YOSHIFUJI Hideaki <yoshfuji@...ux-ipv6.org>
---
 Documentation/networking/ip-sysctl.txt |    5 +++++
 net/core/neighbour.c                   |    4 ++++
 2 files changed, 9 insertions(+)

diff --git a/Documentation/networking/ip-sysctl.txt b/Documentation/networking/ip-sysctl.txt
index 4976564..19ac180 100644
--- a/Documentation/networking/ip-sysctl.txt
+++ b/Documentation/networking/ip-sysctl.txt
@@ -26,6 +26,11 @@ route/max_size - INTEGER
 	Maximum number of routes allowed in the kernel.  Increase
 	this when using large numbers of interfaces and/or routes.
 
+neigh/default/gc_thresh1 - INTEGER
+	Minimum number of entries to keep.  Garbage collector will not
+	purge entries if there are fewer than this number.
+	Default: 256
+
 neigh/default/gc_thresh3 - INTEGER
 	Maximum number of neighbor entries allowed.  Increase this
 	when using large numbers of interfaces and when communicating
diff --git a/net/core/neighbour.c b/net/core/neighbour.c
index c815f28..7bd0eed 100644
--- a/net/core/neighbour.c
+++ b/net/core/neighbour.c
@@ -778,6 +778,9 @@ static void neigh_periodic_work(struct work_struct *work)
 	nht = rcu_dereference_protected(tbl->nht,
 					lockdep_is_held(&tbl->lock));
 
+	if (atomic_read(&tbl->entries) < tbl->gc_thresh1)
+		goto out;
+
 	/*
 	 *	periodically recompute ReachableTime from random function
 	 */
@@ -832,6 +835,7 @@ next_elt:
 		nht = rcu_dereference_protected(tbl->nht,
 						lockdep_is_held(&tbl->lock));
 	}
+out:
 	/* Cycle through all hash buckets every base_reachable_time/2 ticks.
 	 * ARP entry timeouts range from 1/2 base_reachable_time to 3/2
 	 * base_reachable_time.
-- 
1.7.9.5

--
To unsubscribe from this list: send the line "unsubscribe netdev" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html