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 5.15-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-5.15 subdirectory. If you, or anyone else, feels it should not be added to the stable tree, please let <stable@xxxxxxxxxxxxxxx> know about it. commit e1caa9d4e5228f86e5ce76f712cbc95844be8308 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 43ea8cfd374bb..7ff0da5f998a0 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;