[net-next,v3,14/19] mptcp: new sysctl to control the activation per NS

diff --git a/net/mptcp/Makefile b/net/mptcp/Makefile
index 178ae81d8b66..4e98d9edfd0a 100644
--- a/net/mptcp/Makefile
+++ b/net/mptcp/Makefile
@@ -1,4 +1,4 @@ 
 # SPDX-License-Identifier: GPL-2.0
 obj-$(CONFIG_MPTCP) += mptcp.o
 
-mptcp-y := protocol.o subflow.o options.o token.o crypto.o
+mptcp-y := protocol.o subflow.o options.o token.o crypto.o ctrl.o
diff --git a/net/mptcp/ctrl.c b/net/mptcp/ctrl.c
new file mode 100644
index 000000000000..8e39585d37f3
--- /dev/null
+++ b/net/mptcp/ctrl.c
@@ -0,0 +1,130 @@ 
+// SPDX-License-Identifier: GPL-2.0
+/* Multipath TCP
+ *
+ * Copyright (c) 2019, Tessares SA.
+ */
+
+#include <linux/sysctl.h>
+
+#include <net/net_namespace.h>
+#include <net/netns/generic.h>
+
+#include "protocol.h"
+
+#define MPTCP_SYSCTL_PATH "net/mptcp"
+
+static int mptcp_pernet_id;
+struct mptcp_pernet {
+	struct ctl_table_header *ctl_table_hdr;
+
+	int mptcp_enabled;
+};
+
+static struct mptcp_pernet *mptcp_get_pernet(struct net *net)
+{
+	return net_generic(net, mptcp_pernet_id);
+}
+
+int mptcp_is_enabled(struct net *net)
+{
+	return mptcp_get_pernet(net)->mptcp_enabled;
+}
+
+static struct ctl_table mptcp_sysctl_table[] = {
+	{
+		.procname = "enabled",
+		.maxlen = sizeof(int),
+		.mode = 0644,
+		/* users with CAP_NET_ADMIN or root (not and) can change this
+		 * value, same as other sysctl or the 'net' tree.
+		 */
+		.proc_handler = proc_dointvec,
+	},
+	{}
+};
+
+static void mptcp_pernet_set_defaults(struct mptcp_pernet *pernet)
+{
+	pernet->mptcp_enabled = 1;
+}
+
+static int mptcp_pernet_new_table(struct net *net, struct mptcp_pernet *pernet)
+{
+	struct ctl_table_header *hdr;
+	struct ctl_table *table;
+
+	table = mptcp_sysctl_table;
+	if (!net_eq(net, &init_net)) {
+		table = kmemdup(table, sizeof(mptcp_sysctl_table), GFP_KERNEL);
+		if (!table)
+			goto err_alloc;
+	}
+
+	table[0].data = &pernet->mptcp_enabled;
+
+	hdr = register_net_sysctl(net, MPTCP_SYSCTL_PATH, table);
+	if (!hdr)
+		goto err_reg;
+
+	pernet->ctl_table_hdr = hdr;
+
+	return 0;
+
+err_reg:
+	if (!net_eq(net, &init_net))
+		kfree(table);
+err_alloc:
+	return -ENOMEM;
+}
+
+static void mptcp_pernet_del_table(struct mptcp_pernet *pernet)
+{
+	struct ctl_table *table = pernet->ctl_table_hdr->ctl_table_arg;
+
+	unregister_net_sysctl_table(pernet->ctl_table_hdr);
+
+	kfree(table);
+}
+
+static int __net_init mptcp_net_init(struct net *net)
+{
+	struct mptcp_pernet *pernet = mptcp_get_pernet(net);
+
+	mptcp_pernet_set_defaults(pernet);
+
+	return mptcp_pernet_new_table(net, pernet);
+}
+
+/* Note: the callback will only be called per extra netns */
+static void __net_exit mptcp_net_exit(struct net *net)
+{
+	struct mptcp_pernet *pernet = mptcp_get_pernet(net);
+
+	mptcp_pernet_del_table(pernet);
+}
+
+static struct pernet_operations mptcp_pernet_ops = {
+	.init = mptcp_net_init,
+	.exit = mptcp_net_exit,
+	.id = &mptcp_pernet_id,
+	.size = sizeof(struct mptcp_pernet),
+};
+
+void __init mptcp_init(void)
+{
+	mptcp_proto_init();
+
+	if (register_pernet_subsys(&mptcp_pernet_ops) < 0)
+		panic("Failed to register MPTCP pernet subsystem.\n");
+}
+
+#if IS_ENABLED(CONFIG_MPTCP_IPV6)
+int __init mptcpv6_init(void)
+{
+	int err;
+
+	err = mptcp_proto_v6_init();
+
+	return err;
+}
+#endif
diff --git a/net/mptcp/protocol.c b/net/mptcp/protocol.c
index 0b21ae25bd0f..45e482864a19 100644
--- a/net/mptcp/protocol.c
+++ b/net/mptcp/protocol.c
@@ -522,7 +522,7 @@  static void __mptcp_close_ssk(struct sock *sk, struct sock *ssk,
 	}
 }
 
-static int mptcp_init_sock(struct sock *sk)
+static int __mptcp_init_sock(struct sock *sk)
 {
 	struct mptcp_sock *msk = mptcp_sk(sk);
 
@@ -532,6 +532,14 @@  static int mptcp_init_sock(struct sock *sk)
 	return 0;
 }
 
+static int mptcp_init_sock(struct sock *sk)
+{
+	if (!mptcp_is_enabled(sock_net(sk)))
+		return -ENOPROTOOPT;
+
+	return __mptcp_init_sock(sk);
+}
+
 static void mptcp_subflow_shutdown(struct sock *ssk, int how)
 {
 	lock_sock(ssk);
@@ -640,7 +648,7 @@  static struct sock *mptcp_accept(struct sock *sk, int flags, int *err,
 			return NULL;
 		}
 
-		mptcp_init_sock(new_mptcp_sock);
+		__mptcp_init_sock(new_mptcp_sock);
 
 		msk = mptcp_sk(new_mptcp_sock);
 		msk->remote_key = subflow->remote_key;
@@ -1078,7 +1086,7 @@  static struct inet_protosw mptcp_protosw = {
 	.flags		= INET_PROTOSW_ICSK,
 };
 
-void __init mptcp_init(void)
+void mptcp_proto_init(void)
 {
 	mptcp_prot.h.hashinfo = tcp_prot.h.hashinfo;
 	mptcp_stream_ops = inet_stream_ops;
@@ -1116,7 +1124,7 @@  static struct inet_protosw mptcp_v6_protosw = {
 	.flags		= INET_PROTOSW_ICSK,
 };
 
-int mptcpv6_init(void)
+int mptcp_proto_v6_init(void)
 {
 	int err;
 
diff --git a/net/mptcp/protocol.h b/net/mptcp/protocol.h
index 59a83eb64d37..a8fad7d78565 100644
--- a/net/mptcp/protocol.h
+++ b/net/mptcp/protocol.h
@@ -179,6 +179,9 @@  extern const struct inet_connection_sock_af_ops ipv6_specific;
 #endif
 
 void mptcp_proto_init(void);
+#if IS_ENABLED(CONFIG_MPTCP_IPV6)
+int mptcp_proto_v6_init(void);
+#endif
 
 struct mptcp_read_arg {
 	struct msghdr *msg;