[v6,1/2] netfilter: add new sysctl toggle for lightweight tunnel netfilter hooks

diff --git a/Documentation/networking/nf_conntrack-sysctl.rst b/Documentation/networking/nf_conntrack-sysctl.rst
index 024d784157c8..34ca762ea56f 100644
--- a/Documentation/networking/nf_conntrack-sysctl.rst
+++ b/Documentation/networking/nf_conntrack-sysctl.rst
@@ -184,6 +184,13 @@  nf_conntrack_gre_timeout_stream - INTEGER (seconds)
 	This extended timeout will be used in case there is an GRE stream
 	detected.
 
+nf_hooks_lwtunnel - BOOLEAN
+	- 0 - disabled (default)
+	- not 0 - enabled
+
+	If this option is enabled, the lightweight tunnel netfilter hooks are
+	enabled. This option cannot be disabled once it is enabled.
+
 nf_flowtable_tcp_timeout - INTEGER (seconds)
         default 30
 
diff --git a/include/net/lwtunnel.h b/include/net/lwtunnel.h
index 05cfd6ff6528..6f15e6fa154e 100644
--- a/include/net/lwtunnel.h
+++ b/include/net/lwtunnel.h
@@ -51,6 +51,9 @@  struct lwtunnel_encap_ops {
 };
 
 #ifdef CONFIG_LWTUNNEL
+
+DECLARE_STATIC_KEY_FALSE(nf_hooks_lwtunnel_enabled);
+
 void lwtstate_free(struct lwtunnel_state *lws);
 
 static inline struct lwtunnel_state *
diff --git a/include/net/netfilter/nf_hooks_lwtunnel.h b/include/net/netfilter/nf_hooks_lwtunnel.h
new file mode 100644
index 000000000000..f10ee2ccbdc8
--- /dev/null
+++ b/include/net/netfilter/nf_hooks_lwtunnel.h
@@ -0,0 +1,15 @@ 
+#include <linux/sysctl.h>
+#include <linux/types.h>
+
+#ifdef CONFIG_LWTUNNEL
+int nf_hooks_lwtunnel_sysctl_handler(struct ctl_table *table, int write,
+					 void *buffer, size_t *lenp,
+					 loff_t *ppos);
+#else
+int nf_hooks_lwtunnel_sysctl_handler(struct ctl_table *table, int write,
+					 void *buffer, size_t *lenp,
+					 loff_t *ppos)
+{
+    return 0;
+}
+#endif
diff --git a/net/core/lwtunnel.c b/net/core/lwtunnel.c
index 8ec7d13d2860..3e6960b455e1 100644
--- a/net/core/lwtunnel.c
+++ b/net/core/lwtunnel.c
@@ -23,6 +23,9 @@ 
 #include <net/ip6_fib.h>
 #include <net/rtnh.h>
 
+DEFINE_STATIC_KEY_FALSE(nf_hooks_lwtunnel_enabled);
+EXPORT_SYMBOL_GPL(nf_hooks_lwtunnel_enabled);
+
 #ifdef CONFIG_MODULES
 
 static const char *lwtunnel_encap_str(enum lwtunnel_encap_types encap_type)
diff --git a/net/netfilter/Makefile b/net/netfilter/Makefile
index 049890e00a3d..aab20e575ecd 100644
--- a/net/netfilter/Makefile
+++ b/net/netfilter/Makefile
@@ -212,3 +212,6 @@  obj-$(CONFIG_IP_SET) += ipset/
 
 # IPVS
 obj-$(CONFIG_IP_VS) += ipvs/
+
+# lwtunnel
+obj-$(CONFIG_LWTUNNEL) += nf_hooks_lwtunnel.o
diff --git a/net/netfilter/nf_conntrack_standalone.c b/net/netfilter/nf_conntrack_standalone.c
index e84b499b7bfa..7e0d956da51d 100644
--- a/net/netfilter/nf_conntrack_standalone.c
+++ b/net/netfilter/nf_conntrack_standalone.c
@@ -22,6 +22,9 @@ 
 #include <net/netfilter/nf_conntrack_acct.h>
 #include <net/netfilter/nf_conntrack_zones.h>
 #include <net/netfilter/nf_conntrack_timestamp.h>
+#ifdef CONFIG_LWTUNNEL
+#include <net/netfilter/nf_hooks_lwtunnel.h>
+#endif
 #include <linux/rculist_nulls.h>
 
 static bool enable_hooks __read_mostly;
@@ -612,6 +615,9 @@  enum nf_ct_sysctl_index {
 	NF_SYSCTL_CT_PROTO_TIMEOUT_GRE,
 	NF_SYSCTL_CT_PROTO_TIMEOUT_GRE_STREAM,
 #endif
+#ifdef CONFIG_LWTUNNEL
+	NF_SYSCTL_CT_LWTUNNEL,
+#endif
 
 	__NF_SYSCTL_CT_LAST_SYSCTL,
 };
@@ -958,6 +964,15 @@  static struct ctl_table nf_ct_sysctl_table[] = {
 		.mode           = 0644,
 		.proc_handler   = proc_dointvec_jiffies,
 	},
+#endif
+#ifdef CONFIG_LWTUNNEL
+	[NF_SYSCTL_CT_LWTUNNEL] = {
+		.procname	= "nf_hooks_lwtunnel",
+		.data		= NULL,
+		.maxlen		= sizeof(int),
+		.mode		= 0644,
+		.proc_handler	= nf_hooks_lwtunnel_sysctl_handler,
+	},
 #endif
 	{}
 };
diff --git a/net/netfilter/nf_hooks_lwtunnel.c b/net/netfilter/nf_hooks_lwtunnel.c
new file mode 100644
index 000000000000..15b79469048f
--- /dev/null
+++ b/net/netfilter/nf_hooks_lwtunnel.c
@@ -0,0 +1,66 @@ 
+// SPDX-License-Identifier: GPL-2.0
+
+#include <linux/sysctl.h>
+#include <net/lwtunnel.h>
+#include <net/netfilter/nf_hooks_lwtunnel.h>
+
+static inline int nf_hooks_lwtunnel_get(void)
+{
+	if (static_branch_unlikely(&nf_hooks_lwtunnel_enabled))
+		return 1;
+	else
+		return 0;
+}
+
+static inline int nf_hooks_lwtunnel_set(int enable)
+{
+	if (static_branch_unlikely(&nf_hooks_lwtunnel_enabled)) {
+		if (!enable)
+			return -EBUSY;
+	} else if (enable) {
+		static_branch_enable(&nf_hooks_lwtunnel_enabled);
+	}
+
+	return 0;
+}
+
+#ifdef CONFIG_SYSCTL
+
+int nf_hooks_lwtunnel_sysctl_handler(struct ctl_table *table, int write,
+					 void *buffer, size_t *lenp,
+					 loff_t *ppos)
+{
+	int proc_nf_hooks_lwtunnel_enabled = 0;
+	struct ctl_table tmp = {
+		.procname = table->procname,
+		.data = &proc_nf_hooks_lwtunnel_enabled,
+		.maxlen = sizeof(int),
+		.mode = table->mode,
+		.extra1 = SYSCTL_ZERO,
+		.extra2 = SYSCTL_ONE,
+	};
+	int ret;
+
+	if (!write)
+		proc_nf_hooks_lwtunnel_enabled = nf_hooks_lwtunnel_get();
+
+	ret = proc_dointvec_minmax(&tmp, write, buffer, lenp, ppos);
+
+	if (write && ret == 0)
+		ret = nf_hooks_lwtunnel_set(proc_nf_hooks_lwtunnel_enabled);
+
+	return ret;
+}
+EXPORT_SYMBOL_GPL(nf_hooks_lwtunnel_sysctl_handler);
+
+#else // CONFIG_SYSCTL
+
+int nf_hooks_lwtunnel_sysctl_handler(struct ctl_table *table, int write,
+					 void *buffer, size_t *lenp,
+					 loff_t *ppos)
+{
+	return 0;
+}
+EXPORT_SYMBOL_GPL(nf_hooks_lwtunnel_sysctl_handler);
+
+#endif