[PATCH net-next 11/12] mptcp: sysctl: add available_path_managers

["Matthieu Baerts (NGI0)" <matttbe@kernel.org>]

From: Geliang Tang <tanggeliang@kylinos.cn>

Similarly to net.mptcp.available_schedulers, this patch adds a new one
net.mptcp.available_path_managers to list the available path managers.

Signed-off-by: Geliang Tang <tanggeliang@kylinos.cn>
Reviewed-by: Matthieu Baerts (NGI0) <matttbe@kernel.org>
Signed-off-by: Matthieu Baerts (NGI0) <matttbe@kernel.org>
---
 Documentation/networking/mptcp-sysctl.rst |  4 ++++
 include/net/mptcp.h                       |  2 ++
 net/mptcp/ctrl.c                          | 25 +++++++++++++++++++++++++
 net/mptcp/pm.c                            | 19 +++++++++++++++++++
 net/mptcp/protocol.h                      |  1 +
 5 files changed, 51 insertions(+)

diff --git a/Documentation/networking/mptcp-sysctl.rst b/Documentation/networking/mptcp-sysctl.rst
index b78a2254d4523e0c0fa09338d4b676da18f82d97..5bfab01eff5a9db89e1484787953241c16e147cf 100644
--- a/Documentation/networking/mptcp-sysctl.rst
+++ b/Documentation/networking/mptcp-sysctl.rst
@@ -30,6 +30,10 @@ allow_join_initial_addr_port - BOOLEAN
 
 	Default: 1
 
+available_path_managers - STRING
+	Shows the available path managers choices that are registered. More
+	path managers may be available, but not loaded.
+
 available_schedulers - STRING
 	Shows the available schedulers choices that are registered. More packet
 	schedulers may be available, but not loaded.
diff --git a/include/net/mptcp.h b/include/net/mptcp.h
index 645d15695e3f5ec4b945bb543630f3dcc54453f2..bfbad695951cf664af4d05390104883268b6bcd2 100644
--- a/include/net/mptcp.h
+++ b/include/net/mptcp.h
@@ -123,6 +123,8 @@ struct mptcp_sched_ops {
 } ____cacheline_aligned_in_smp;
 
 #define MPTCP_PM_NAME_MAX	16
+#define MPTCP_PM_MAX		128
+#define MPTCP_PM_BUF_MAX	(MPTCP_PM_NAME_MAX * MPTCP_PM_MAX)
 
 struct mptcp_pm_ops {
 	char			name[MPTCP_PM_NAME_MAX];
diff --git a/net/mptcp/ctrl.c b/net/mptcp/ctrl.c
index 4d8b31f32eb50347d10db792f084e43c93f687c6..d9290c5bb6c7956ca98319259f92b812680f74f7 100644
--- a/net/mptcp/ctrl.c
+++ b/net/mptcp/ctrl.c
@@ -253,6 +253,24 @@ static int proc_pm_type(const struct ctl_table *ctl, int write,
 	return ret;
 }
 
+static int proc_available_path_managers(const struct ctl_table *ctl,
+					int write, void *buffer,
+					size_t *lenp, loff_t *ppos)
+{
+	struct ctl_table tbl = { .maxlen = MPTCP_PM_BUF_MAX, };
+	int ret;
+
+	tbl.data = kmalloc(tbl.maxlen, GFP_USER);
+	if (!tbl.data)
+		return -ENOMEM;
+
+	mptcp_pm_get_available(tbl.data, MPTCP_PM_BUF_MAX);
+	ret = proc_dostring(&tbl, write, buffer, lenp, ppos);
+	kfree(tbl.data);
+
+	return ret;
+}
+
 static struct ctl_table mptcp_sysctl_table[] = {
 	{
 		.procname = "enabled",
@@ -338,6 +356,12 @@ static struct ctl_table mptcp_sysctl_table[] = {
 		.mode = 0644,
 		.proc_handler = proc_path_manager,
 	},
+	{
+		.procname = "available_path_managers",
+		.maxlen	= MPTCP_PM_BUF_MAX,
+		.mode = 0444,
+		.proc_handler = proc_available_path_managers,
+	},
 };
 
 static int mptcp_pernet_new_table(struct net *net, struct mptcp_pernet *pernet)
@@ -364,6 +388,7 @@ static int mptcp_pernet_new_table(struct net *net, struct mptcp_pernet *pernet)
 	table[9].data = &pernet->blackhole_timeout;
 	table[10].data = &pernet->syn_retrans_before_tcp_fallback;
 	table[11].data = &pernet->path_manager;
+	/* table[12] is for available_path_managers which is read-only info */
 
 	hdr = register_net_sysctl_sz(net, MPTCP_SYSCTL_PATH, table,
 				     ARRAY_SIZE(mptcp_sysctl_table));
diff --git a/net/mptcp/pm.c b/net/mptcp/pm.c
index 3896f21a46bd7f6912d2ffe22a3984ba97923021..18b19dbccbba72916b2f666600a2bc8993ebd1df 100644
--- a/net/mptcp/pm.c
+++ b/net/mptcp/pm.c
@@ -1070,3 +1070,22 @@ void mptcp_pm_unregister(struct mptcp_pm_ops *pm_ops)
 	list_del_rcu(&pm_ops->list);
 	spin_unlock(&mptcp_pm_list_lock);
 }
+
+/* Build string with list of available path manager values.
+ * Similar to tcp_get_available_congestion_control()
+ */
+void mptcp_pm_get_available(char *buf, size_t maxlen)
+{
+	struct mptcp_pm_ops *pm_ops;
+	size_t offs = 0;
+
+	rcu_read_lock();
+	list_for_each_entry_rcu(pm_ops, &mptcp_pm_list, list) {
+		offs += snprintf(buf + offs, maxlen - offs, "%s%s",
+				 offs == 0 ? "" : " ", pm_ops->name);
+
+		if (WARN_ON_ONCE(offs >= maxlen))
+			break;
+	}
+	rcu_read_unlock();
+}
diff --git a/net/mptcp/protocol.h b/net/mptcp/protocol.h
index 818c2c648677c255a00d668ab9b7406f0731fcf8..d409586b5977f93bff14fffd83b1d3020d57353b 100644
--- a/net/mptcp/protocol.h
+++ b/net/mptcp/protocol.h
@@ -1058,6 +1058,7 @@ struct mptcp_pm_ops *mptcp_pm_find(const char *name);
 int mptcp_pm_register(struct mptcp_pm_ops *pm_ops);
 void mptcp_pm_unregister(struct mptcp_pm_ops *pm_ops);
 int mptcp_pm_validate(struct mptcp_pm_ops *pm_ops);
+void mptcp_pm_get_available(char *buf, size_t maxlen);
 
 void mptcp_userspace_pm_free_local_addr_list(struct mptcp_sock *msk);
 

-- 
2.48.1