netfilter: conntrack: allow increasing bucket size via sysctl too

No need to restrict this to module parameter.

We export a copy of the real hash size -- when user alters the value we
allocate the new table, copy entries etc before we update the real size
to the requested one.

This is also needed because the real size is used by concurrent readers
and cannot be changed without synchronizing the conntrack generation
seqcnt.

We only allow changing this value from the initial net namespace.

Tested using http-client-benchmark vs. httpterm with concurrent

while true;do
 echo $RANDOM > /proc/sys/net/netfilter/nf_conntrack_buckets
done

Signed-off-by: Florian Westphal <fw@strlen.de>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>

1 files changed, 31 insertions, 5 deletions

diff --git a/net/netfilter/nf_conntrack_standalone.c b/net/netfilter/nf_conntrack_standalone.c
index f87e84ebcec3a..a0cc1919f0814 100644
--- a/net/netfilter/nf_conntrack_standalone.c
+++ b/net/netfilter/nf_conntrack_standalone.c
@@ -434,8 +434,29 @@ static void nf_conntrack_standalone_fini_proc(struct net *net)
 
 #ifdef CONFIG_SYSCTL
 /* Log invalid packets of a given protocol */
-static int log_invalid_proto_min = 0;
-static int log_invalid_proto_max = 255;
+static int log_invalid_proto_min __read_mostly;
+static int log_invalid_proto_max __read_mostly = 255;
+
+/* size the user *wants to set */
+static unsigned int nf_conntrack_htable_size_user __read_mostly;
+
+static int
+nf_conntrack_hash_sysctl(struct ctl_table *table, int write,
+			 void __user *buffer, size_t *lenp, loff_t *ppos)
+{
+	int ret;
+
+	ret = proc_dointvec(table, write, buffer, lenp, ppos);
+	if (ret < 0 || !write)
+		return ret;
+
+	/* update ret, we might not be able to satisfy request */
+	ret = nf_conntrack_hash_resize(nf_conntrack_htable_size_user);
+
+	/* update it to the actual value used by conntrack */
+	nf_conntrack_htable_size_user = nf_conntrack_htable_size;
+	return ret;
+}
 
 static struct ctl_table_header *nf_ct_netfilter_header;
 
@@ -456,10 +477,10 @@ static struct ctl_table nf_ct_sysctl_table[] = {
 	},
 	{
 		.procname       = "nf_conntrack_buckets",
-		.data           = &nf_conntrack_htable_size,
+		.data           = &nf_conntrack_htable_size_user,
 		.maxlen         = sizeof(unsigned int),
-		.mode           = 0444,
-		.proc_handler   = proc_dointvec,
+		.mode           = 0644,
+		.proc_handler   = nf_conntrack_hash_sysctl,
 	},
 	{
 		.procname	= "nf_conntrack_checksum",
@@ -517,6 +538,9 @@ static int nf_conntrack_standalone_init_sysctl(struct net *net)
 	if (net->user_ns != &init_user_ns)
 		table[0].procname = NULL;
 
+	if (!net_eq(&init_net, net))
+		table[2].mode = 0444;
+
 	net->ct.sysctl_header = register_net_sysctl(net, "net/netfilter", table);
 	if (!net->ct.sysctl_header)
 		goto out_unregister_netfilter;
@@ -606,6 +630,8 @@ static int __init nf_conntrack_standalone_init(void)
 		ret = -ENOMEM;
 		goto out_sysctl;
 	}
+
+	nf_conntrack_htable_size_user = nf_conntrack_htable_size;
 #endif
 
 	ret = register_pernet_subsys(&nf_conntrack_net_ops);