mptcp: sysctl: add available_path_managers

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

Signed-off-by: Geliang Tang <[email protected]>

Author: Geliang Tang

Documentation/networking/mptcp-sysctl.rst

@@ -89,6 +89,10 @@ path_manager - STRING
 
 	Default: "in-kernel"
 
+available_path_managers - STRING
+	Shows the available path managers choices that are registered. More
+        path managers may be available, but not loaded.
+
 scheduler - STRING
 	Select the scheduler of your choice.
 

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 {
 	int (*created)(struct mptcp_sock *msk);

net/mptcp/ctrl.c

@@ -136,6 +136,24 @@ static int proc_path_manager(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 int mptcp_set_scheduler(char *scheduler, const char *name)
 {
 	struct mptcp_sched_ops *sched;
@@ -252,6 +270,12 @@ 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,
+	},
 	{
 		.procname = "scheduler",
 		.maxlen	= MPTCP_SCHED_NAME_MAX,
@@ -304,6 +328,7 @@ static int mptcp_pernet_new_table(struct net *net, struct mptcp_pernet *pernet)
 	table[i++].data = &pernet->allow_join_initial_addr_port;
 	table[i++].data = &pernet->stale_loss_cnt;
 	table[i++].data = &pernet->path_manager;
+	i++; /* table[i] is for available_path_managers which is read-only info */
 	table[i++].data = &pernet->scheduler;
 	i++; /* table[i] is for available_schedulers which is read-only info */
 	table[i++].data = &pernet->close_timeout;

net/mptcp/pm.c

@@ -673,6 +673,26 @@ struct mptcp_pm_ops *mptcp_pm_find(const char *name)
 	return NULL;
 }
 
+/* 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;
+	size_t offs = 0;
+
+	rcu_read_lock();
+	list_for_each_entry_rcu(pm, &mptcp_pm_list, list) {
+		offs += snprintf(buf + offs, maxlen - offs,
+				 "%s%s",
+				 offs == 0 ? "" : " ", pm->name);
+
+		if (WARN_ON_ONCE(offs >= maxlen))
+			break;
+	}
+	rcu_read_unlock();
+}
+
 int mptcp_pm_validate(struct mptcp_pm_ops *pm)
 {
 	if (!pm->get_local_id || !pm->get_priority) {

net/mptcp/protocol.h

@@ -1050,6 +1050,7 @@ void mptcp_pm_remove_addr_entry(struct mptcp_sock *msk,
 extern struct mptcp_pm_ops mptcp_in_kernel_pm;
 
 struct mptcp_pm_ops *mptcp_pm_find(const char *name);
+void mptcp_pm_get_available(char *buf, size_t maxlen);
 int mptcp_pm_validate(struct mptcp_pm_ops *pm);
 int mptcp_pm_register(struct mptcp_pm_ops *pm);
 void mptcp_pm_unregister(struct mptcp_pm_ops *pm);