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 D93A7C43217 for ; Tue, 10 May 2022 12:24:09 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S241754AbiEJM2D (ORCPT ); Tue, 10 May 2022 08:28:03 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:49332 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S241687AbiEJMZ7 (ORCPT ); Tue, 10 May 2022 08:25:59 -0400 Received: from mail.netfilter.org (mail.netfilter.org [217.70.188.207]) by lindbergh.monkeyblade.net (Postfix) with ESMTP id 4366091365; Tue, 10 May 2022 05:22:02 -0700 (PDT) From: Pablo Neira Ayuso To: netfilter-devel@vger.kernel.org Cc: davem@davemloft.net, netdev@vger.kernel.org, kuba@kernel.org Subject: [PATCH net-next 12/17] netfilter: nfnetlink: allow to detect if ctnetlink listeners exist Date: Tue, 10 May 2022 14:21:45 +0200 Message-Id: <20220510122150.92533-13-pablo@netfilter.org> X-Mailer: git-send-email 2.30.2 In-Reply-To: <20220510122150.92533-1-pablo@netfilter.org> References: <20220510122150.92533-1-pablo@netfilter.org> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: netdev@vger.kernel.org From: Florian Westphal At this time, every new conntrack gets the 'event cache extension' enabled for it. This is because the 'net.netfilter.nf_conntrack_events' sysctl defaults to 1. Changing the default to 0 means that commands that rely on the event notification extension, e.g. 'conntrack -E' or conntrackd, stop working. We COULD detect if there is a listener by means of 'nfnetlink_has_listeners()' and only add the extension if this is true. The downside is a dependency from conntrack module to nfnetlink module. This adds a different way: inc/dec a counter whenever a ctnetlink group is being (un)subscribed and toggle a flag in struct net. Next patches will take advantage of this and will only add the event extension if the flag is set. Signed-off-by: Florian Westphal Signed-off-by: Pablo Neira Ayuso --- include/net/netns/conntrack.h | 1 + net/netfilter/nfnetlink.c | 40 ++++++++++++++++++++++++++++++++--- 2 files changed, 38 insertions(+), 3 deletions(-) diff --git a/include/net/netns/conntrack.h b/include/net/netns/conntrack.h index a71cfd4e2f21..0677cd3de034 100644 --- a/include/net/netns/conntrack.h +++ b/include/net/netns/conntrack.h @@ -95,6 +95,7 @@ struct nf_ip_net { struct netns_ct { #ifdef CONFIG_NF_CONNTRACK_EVENTS + bool ctnetlink_has_listener; bool ecache_dwork_pending; #endif u8 sysctl_log_invalid; /* Log invalid packets */ diff --git a/net/netfilter/nfnetlink.c b/net/netfilter/nfnetlink.c index 7e2c8dd01408..ad3bbe34ca88 100644 --- a/net/netfilter/nfnetlink.c +++ b/net/netfilter/nfnetlink.c @@ -45,6 +45,7 @@ MODULE_DESCRIPTION("Netfilter messages via netlink socket"); static unsigned int nfnetlink_pernet_id __read_mostly; struct nfnl_net { + unsigned int ctnetlink_listeners; struct sock *nfnl; }; @@ -654,7 +655,6 @@ static void nfnetlink_rcv(struct sk_buff *skb) netlink_rcv_skb(skb, nfnetlink_rcv_msg); } -#ifdef CONFIG_MODULES static int nfnetlink_bind(struct net *net, int group) { const struct nfnetlink_subsystem *ss; @@ -670,9 +670,44 @@ static int nfnetlink_bind(struct net *net, int group) rcu_read_unlock(); if (!ss) request_module_nowait("nfnetlink-subsys-%d", type); + +#ifdef CONFIG_NF_CONNTRACK_EVENTS + if (type == NFNL_SUBSYS_CTNETLINK) { + struct nfnl_net *nfnlnet = nfnl_pernet(net); + + nfnl_lock(NFNL_SUBSYS_CTNETLINK); + + if (WARN_ON_ONCE(nfnlnet->ctnetlink_listeners == UINT_MAX)) { + nfnl_unlock(NFNL_SUBSYS_CTNETLINK); + return -EOVERFLOW; + } + + nfnlnet->ctnetlink_listeners++; + if (nfnlnet->ctnetlink_listeners == 1) + WRITE_ONCE(net->ct.ctnetlink_has_listener, true); + nfnl_unlock(NFNL_SUBSYS_CTNETLINK); + } +#endif return 0; } + +static void nfnetlink_unbind(struct net *net, int group) +{ +#ifdef CONFIG_NF_CONNTRACK_EVENTS + int type = nfnl_group2type[group]; + + if (type == NFNL_SUBSYS_CTNETLINK) { + struct nfnl_net *nfnlnet = nfnl_pernet(net); + + nfnl_lock(NFNL_SUBSYS_CTNETLINK); + WARN_ON_ONCE(nfnlnet->ctnetlink_listeners == 0); + nfnlnet->ctnetlink_listeners--; + if (nfnlnet->ctnetlink_listeners == 0) + WRITE_ONCE(net->ct.ctnetlink_has_listener, false); + nfnl_unlock(NFNL_SUBSYS_CTNETLINK); + } #endif +} static int __net_init nfnetlink_net_init(struct net *net) { @@ -680,9 +715,8 @@ static int __net_init nfnetlink_net_init(struct net *net) struct netlink_kernel_cfg cfg = { .groups = NFNLGRP_MAX, .input = nfnetlink_rcv, -#ifdef CONFIG_MODULES .bind = nfnetlink_bind, -#endif + .unbind = nfnetlink_unbind, }; nfnlnet->nfnl = netlink_kernel_create(net, NETLINK_NETFILTER, &cfg); -- 2.30.2