linux-kernel - [PATCH v2] nf_conntrack: sysctl: expose gc worker scan interval via sysctl

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Message-Id: <20250430064342.62592-1-vimal.agrawal@sophos.com>
Date: Wed, 30 Apr 2025 06:43:42 +0000
From: avimalin@...il.com
To: vimal.agrawal@...hos.com,
	linux-kernel@...r.kernel.org,
	pablo@...filter.org,
	netfilter-devel@...r.kernel.org,
	fw@...len.de,
	anirudh.gupta@...hos.com
Subject: [PATCH v2] nf_conntrack: sysctl: expose gc worker scan interval via sysctl

From: Vimal Agrawal <vimal.agrawal@...hos.com>

Default initial gc scan interval of 60 secs is too long for system
with low number of conntracks causing delay in conntrack deletion.
It is affecting userspace which are replying on timely arrival of
conntrack destroy event. So it is better that this is controlled
through sysctl

Fixes: 2aa192757005 ("netfilter: conntrack: revisit the gc initial rescheduling bias")
Signed-off-by: Vimal Agrawal <vimal.agrawal@...hos.com>
Reviewed-by: Florian Westphal <fw@...len.de>
Reviewed-by: Anirudh Gupta <anirudh.gupta@...hos.com>
---
v2: Don't allow non-init_net ns to alter this global sysctl

 include/net/netfilter/nf_conntrack.h    | 1 +
 net/netfilter/nf_conntrack_core.c       | 4 +++-
 net/netfilter/nf_conntrack_standalone.c | 9 +++++++++
 3 files changed, 13 insertions(+), 1 deletion(-)

diff --git a/include/net/netfilter/nf_conntrack.h b/include/net/netfilter/nf_conntrack.h
index 3f02a45773e8..eaf1933687b2 100644
--- a/include/net/netfilter/nf_conntrack.h
+++ b/include/net/netfilter/nf_conntrack.h
@@ -321,6 +321,7 @@ extern struct hlist_nulls_head *nf_conntrack_hash;
 extern unsigned int nf_conntrack_htable_size;
 extern seqcount_spinlock_t nf_conntrack_generation;
 extern unsigned int nf_conntrack_max;
+extern unsigned int nf_conntrack_gc_scan_interval_init;
 
 /* must be called with rcu read lock held */
 static inline void
diff --git a/net/netfilter/nf_conntrack_core.c b/net/netfilter/nf_conntrack_core.c
index 7f8b245e287a..d7e03c29765a 100644
--- a/net/netfilter/nf_conntrack_core.c
+++ b/net/netfilter/nf_conntrack_core.c
@@ -204,6 +204,8 @@ EXPORT_SYMBOL_GPL(nf_conntrack_htable_size);
 
 unsigned int nf_conntrack_max __read_mostly;
 EXPORT_SYMBOL_GPL(nf_conntrack_max);
+__read_mostly unsigned int nf_conntrack_gc_scan_interval_init = GC_SCAN_INTERVAL_INIT;
+EXPORT_SYMBOL_GPL(nf_conntrack_gc_scan_interval_init);
 seqcount_spinlock_t nf_conntrack_generation __read_mostly;
 static siphash_aligned_key_t nf_conntrack_hash_rnd;
 
@@ -1513,7 +1515,7 @@ static void gc_worker(struct work_struct *work)
 		nf_conntrack_max95 = nf_conntrack_max / 100u * 95u;
 
 	if (i == 0) {
-		gc_work->avg_timeout = GC_SCAN_INTERVAL_INIT;
+		gc_work->avg_timeout = nf_conntrack_gc_scan_interval_init;
 		gc_work->count = GC_SCAN_INITIAL_COUNT;
 		gc_work->start_time = start_time;
 	}
diff --git a/net/netfilter/nf_conntrack_standalone.c b/net/netfilter/nf_conntrack_standalone.c
index 2f666751c7e7..bdbf37a938bb 100644
--- a/net/netfilter/nf_conntrack_standalone.c
+++ b/net/netfilter/nf_conntrack_standalone.c
@@ -559,6 +559,7 @@ enum nf_ct_sysctl_index {
 #ifdef CONFIG_NF_CONNTRACK_TIMESTAMP
 	NF_SYSCTL_CT_TIMESTAMP,
 #endif
+	NF_SYSCTL_CT_GC_SCAN_INTERVAL_INIT,
 	NF_SYSCTL_CT_PROTO_TIMEOUT_GENERIC,
 	NF_SYSCTL_CT_PROTO_TIMEOUT_TCP_SYN_SENT,
 	NF_SYSCTL_CT_PROTO_TIMEOUT_TCP_SYN_RECV,
@@ -691,6 +692,13 @@ static struct ctl_table nf_ct_sysctl_table[] = {
 		.extra2 	= SYSCTL_ONE,
 	},
 #endif
+	[NF_SYSCTL_CT_GC_SCAN_INTERVAL_INIT] = {
+		.procname	= "nf_conntrack_gc_scan_interval_init",
+		.data		= &nf_conntrack_gc_scan_interval_init,
+		.maxlen		= sizeof(unsigned int),
+		.mode		= 0644,
+		.proc_handler	= proc_dointvec_jiffies,
+	},
 	[NF_SYSCTL_CT_PROTO_TIMEOUT_GENERIC] = {
 		.procname	= "nf_conntrack_generic_timeout",
 		.maxlen		= sizeof(unsigned int),
@@ -1090,6 +1098,7 @@ static int nf_conntrack_standalone_init_sysctl(struct net *net)
 		table[NF_SYSCTL_CT_MAX].mode = 0444;
 		table[NF_SYSCTL_CT_EXPECT_MAX].mode = 0444;
 		table[NF_SYSCTL_CT_BUCKETS].mode = 0444;
+		table[NF_SYSCTL_CT_GC_SCAN_INTERVAL_INIT].mode = 0444;
 	}
 
 	cnet->sysctl_header = register_net_sysctl_sz(net, "net/netfilter",
-- 
2.17.1