From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 27C6CC6FD1F for ; Tue, 7 Mar 2023 10:04:40 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231148AbjCGKEi (ORCPT ); Tue, 7 Mar 2023 05:04:38 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:40406 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231128AbjCGKEf (ORCPT ); Tue, 7 Mar 2023 05:04:35 -0500 Received: from mail.netfilter.org (mail.netfilter.org [217.70.188.207]) by lindbergh.monkeyblade.net (Postfix) with ESMTP id 29073392B2; Tue, 7 Mar 2023 02:04:33 -0800 (PST) From: Pablo Neira Ayuso To: netfilter-devel@vger.kernel.org Cc: davem@davemloft.net, netdev@vger.kernel.org, kuba@kernel.org, pabeni@redhat.com, edumazet@google.com Subject: [PATCH net 3/3] netfilter: conntrack: adopt safer max chain length Date: Tue, 7 Mar 2023 11:04:24 +0100 Message-Id: <20230307100424.2037-4-pablo@netfilter.org> X-Mailer: git-send-email 2.30.2 In-Reply-To: <20230307100424.2037-1-pablo@netfilter.org> References: <20230307100424.2037-1-pablo@netfilter.org> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: netfilter-devel@vger.kernel.org From: Eric Dumazet 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 Signed-off-by: Pablo Neira Ayuso --- net/netfilter/nf_conntrack_core.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) diff --git a/net/netfilter/nf_conntrack_core.c b/net/netfilter/nf_conntrack_core.c index 7250082e7de5..c6a6a6099b4e 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; -- 2.30.2