This is a note to let you know that I've just added the patch titled
netfilter: conntrack: adopt safer max chain length
to the 6.2-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
netfilter-conntrack-adopt-safer-max-chain-length.patch
and it can be found in the queue-6.2 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
commit 786e9ae0a309262ce17a5c4da808e27dc58892e7
Author: Eric Dumazet <edumazet@xxxxxxxxxx>
Date: Tue Mar 7 05:22:54 2023 +0000
netfilter: conntrack: adopt safer max chain length
[ Upstream commit c77737b736ceb50fdf150434347dbd81ec76dbb1 ]
Customers using GKE 1.25 and 1.26 are facing conntrack issues
root caused to commit c9c3b6811f74 ("netfilter: conntrack: make
max chain length random").
Even if we assume Uniform Hashing, a bucket often reachs 8 chained
items while the load factor of the hash table is smaller than 0.5
With a limit of 16, we reach load factors of 3.
With a limit of 32, we reach load factors of 11.
With a limit of 40, we reach load factors of 15.
With a limit of 50, we reach load factors of 24.
This patch changes MIN_CHAINLEN to 50, to minimize risks.
Ideally, we could in the future add a cushion based on expected
load factor (2 * nf_conntrack_max / nf_conntrack_buckets),
because some setups might expect unusual values.
Fixes: c9c3b6811f74 ("netfilter: conntrack: make max chain length random")
Signed-off-by: Eric Dumazet <edumazet@xxxxxxxxxx>
Signed-off-by: Pablo Neira Ayuso <pablo@xxxxxxxxxxxxx>
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
diff --git a/net/netfilter/nf_conntrack_core.c b/net/netfilter/nf_conntrack_core.c
index ead11a9c261f3..19e3afb23fdaf 100644
--- a/net/netfilter/nf_conntrack_core.c
+++ b/net/netfilter/nf_conntrack_core.c
@@ -96,8 +96,8 @@ static DEFINE_MUTEX(nf_conntrack_mutex);
#define GC_SCAN_MAX_DURATION msecs_to_jiffies(10)
#define GC_SCAN_EXPIRED_MAX (64000u / HZ)
-#define MIN_CHAINLEN 8u
-#define MAX_CHAINLEN (32u - MIN_CHAINLEN)
+#define MIN_CHAINLEN 50u
+#define MAX_CHAINLEN (80u - MIN_CHAINLEN)
static struct conntrack_gc_work conntrack_gc_work;
