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From: Geliang Tang <geliang@kernel.org>
To: mptcp@lists.linux.dev
Cc: Geliang Tang <tanggeliang@kylinos.cn>
Subject: [PATCH mptcp-next v7 02/11] mptcp: sysctl: new sysctl to set path
 manager by name
Date: Mon,  3 Mar 2025 12:22:50 +0800
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From: Geliang Tang <tanggeliang@kylinos.cn>

A new net.mptcp.path_manager sysctl is added to determine which path
manager will be used by each newly-created MPTCP socket by setting the
name of it.

This sysctl makes the old one "pm_type" deprecated.

Signed-off-by: Geliang Tang <tanggeliang@kylinos.cn>
---
 Documentation/networking/mptcp-sysctl.rst | 22 ++++++++++
 net/mptcp/ctrl.c                          | 50 +++++++++++++++++++++++
 net/mptcp/protocol.h                      |  1 +
 3 files changed, 73 insertions(+)

diff --git a/Documentation/networking/mptcp-sysctl.rst b/Documentation/netw=
orking/mptcp-sysctl.rst
index 03e1d3610333..5f6c02c12f5b 100644
--- a/Documentation/networking/mptcp-sysctl.rst
+++ b/Documentation/networking/mptcp-sysctl.rst
@@ -72,6 +72,26 @@ enabled - BOOLEAN
=20
 	Default: 1 (enabled)
=20
+path_manager - STRING
+	Set the default path manager name to use for each new MPTCP
+	socket. In-kernel path management will control subflow
+	connections and address advertisements according to
+	per-namespace values configured over the MPTCP netlink
+	API. Userspace path management puts per-MPTCP-connection subflow
+	connection decisions and address advertisements under control of
+	a privileged userspace program, at the cost of more netlink
+	traffic to propagate all of the related events and commands.
+	User-defined BPF-based path managers can also be set via this
+	sysctl.
+
+	This is a per-namespace sysctl.
+
+	* "kernel"          - In-kernel path manager
+	* "userspace"       - Userspace path manager
+	* all other strings - BPF-based path managers
+
+	Default: "kernel"
+
 pm_type - INTEGER
 	Set the default path manager type to use for each new MPTCP
 	socket. In-kernel path management will control subflow
@@ -84,6 +104,8 @@ pm_type - INTEGER
=20
 	This is a per-namespace sysctl.
=20
+	(Deprecated, use path_manager instead.).
+
 	* 0 - In-kernel path manager
 	* 1 - Userspace path manager
=20
diff --git a/net/mptcp/ctrl.c b/net/mptcp/ctrl.c
index be6c0237e10b..d64e6b4f6d1d 100644
--- a/net/mptcp/ctrl.c
+++ b/net/mptcp/ctrl.c
@@ -39,6 +39,7 @@ struct mptcp_pernet {
 	u8 allow_join_initial_addr_port;
 	u8 pm_type;
 	char scheduler[MPTCP_SCHED_NAME_MAX];
+	char path_manager[MPTCP_PM_NAME_MAX];
 };
=20
 static struct mptcp_pernet *mptcp_get_pernet(const struct net *net)
@@ -83,6 +84,11 @@ int mptcp_get_pm_type(const struct net *net)
 	return mptcp_get_pernet(net)->pm_type;
 }
=20
+const char *mptcp_get_path_manager(const struct net *net)
+{
+	return mptcp_get_pernet(net)->path_manager;
+}
+
 const char *mptcp_get_scheduler(const struct net *net)
 {
 	return mptcp_get_pernet(net)->scheduler;
@@ -101,6 +107,7 @@ static void mptcp_pernet_set_defaults(struct mptcp_pern=
et *pernet)
 	pernet->stale_loss_cnt =3D 4;
 	pernet->pm_type =3D MPTCP_PM_TYPE_KERNEL;
 	strscpy(pernet->scheduler, "default", sizeof(pernet->scheduler));
+	strscpy(pernet->path_manager, "kernel", sizeof(pernet->path_manager));
 }
=20
 #ifdef CONFIG_SYSCTL
@@ -174,6 +181,42 @@ static int proc_blackhole_detect_timeout(const struct =
ctl_table *table,
 	return ret;
 }
=20
+static int mptcp_set_path_manager(char *path_manager, const char *name)
+{
+	struct mptcp_pm_ops *pm;
+	int ret =3D 0;
+
+	rcu_read_lock();
+	pm =3D mptcp_pm_find(name);
+	if (pm)
+		strscpy(path_manager, name, MPTCP_PM_NAME_MAX);
+	else
+		ret =3D -ENOENT;
+	rcu_read_unlock();
+
+	return ret;
+}
+
+static int proc_path_manager(const struct ctl_table *ctl, int write,
+			     void *buffer, size_t *lenp, loff_t *ppos)
+{
+	char (*path_manager)[MPTCP_PM_NAME_MAX] =3D ctl->data;
+	char val[MPTCP_PM_NAME_MAX];
+	const struct ctl_table tbl =3D {
+		.data =3D val,
+		.maxlen =3D MPTCP_PM_NAME_MAX,
+	};
+	int ret;
+
+	strscpy(val, *path_manager, MPTCP_PM_NAME_MAX);
+
+	ret =3D proc_dostring(&tbl, write, buffer, lenp, ppos);
+	if (write && ret =3D=3D 0)
+		ret =3D mptcp_set_path_manager(*path_manager, val);
+
+	return ret;
+}
+
 static struct ctl_table mptcp_sysctl_table[] =3D {
 	{
 		.procname =3D "enabled",
@@ -253,6 +296,12 @@ static struct ctl_table mptcp_sysctl_table[] =3D {
 		.mode =3D 0644,
 		.proc_handler =3D proc_dou8vec_minmax,
 	},
+	{
+		.procname =3D "path_manager",
+		.maxlen	=3D MPTCP_PM_NAME_MAX,
+		.mode =3D 0644,
+		.proc_handler =3D proc_path_manager,
+	},
 };
=20
 static int mptcp_pernet_new_table(struct net *net, struct mptcp_pernet *pe=
rnet)
@@ -278,6 +327,7 @@ static int mptcp_pernet_new_table(struct net *net, stru=
ct mptcp_pernet *pernet)
 	table[8].data =3D &pernet->close_timeout;
 	table[9].data =3D &pernet->blackhole_timeout;
 	table[10].data =3D &pernet->syn_retrans_before_tcp_fallback;
+	table[11].data =3D &pernet->path_manager;
=20
 	hdr =3D register_net_sysctl_sz(net, MPTCP_SYSCTL_PATH, table,
 				     ARRAY_SIZE(mptcp_sysctl_table));
diff --git a/net/mptcp/protocol.h b/net/mptcp/protocol.h
index 090592c108d6..737f148770e3 100644
--- a/net/mptcp/protocol.h
+++ b/net/mptcp/protocol.h
@@ -694,6 +694,7 @@ int mptcp_allow_join_id0(const struct net *net);
 unsigned int mptcp_stale_loss_cnt(const struct net *net);
 unsigned int mptcp_close_timeout(const struct sock *sk);
 int mptcp_get_pm_type(const struct net *net);
+const char *mptcp_get_path_manager(const struct net *net);
 const char *mptcp_get_scheduler(const struct net *net);
=20
 void mptcp_active_disable(struct sock *sk);
--=20
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