From: Geliang Tang <tanggeliang@kylinos.cn>

In order to allow users to develop their own BPF-based path manager,
this patch defines a struct ops "mptcp_pm_ops" for a userspace path
manager, which contains a set of interfaces.

Add a set of functions to register, unregister, find and validate a
given struct ops.

Signed-off-by: Geliang Tang <tanggeliang@kylinos.cn>
---
 include/net/mptcp.h  | 32 ++++++++++++++++++++++++
 net/mptcp/pm.c       | 59 ++++++++++++++++++++++++++++++++++++++++++++
 net/mptcp/protocol.h |  5 ++++
 3 files changed, 96 insertions(+)

diff --git a/include/net/mptcp.h b/include/net/mptcp.h
index 72d6e6597add..d629da5f8e8b 100644
--- a/include/net/mptcp.h
+++ b/include/net/mptcp.h
@@ -14,6 +14,7 @@
 
 struct mptcp_info;
 struct mptcp_sock;
+struct mptcp_pm_addr_entry;
 struct seq_file;
 
 /* MPTCP sk_buff extension data */
@@ -121,6 +122,37 @@ struct mptcp_sched_ops {
 	void (*release)(struct mptcp_sock *msk);
 } ____cacheline_aligned_in_smp;
 
+struct mptcp_pm_ops {
+	int (*created)(struct mptcp_sock *msk);
+	int (*established)(struct mptcp_sock *msk);
+	int (*closed)(struct mptcp_sock *msk);
+	int (*address_announced)(struct mptcp_sock *msk,
+				 struct mptcp_pm_addr_entry *local);
+	int (*address_removed)(struct mptcp_sock *msk, u8 id);
+	int (*subflow_established)(struct mptcp_sock *msk,
+				   struct mptcp_pm_addr_entry *local,
+				   struct mptcp_addr_info *remote);
+	int (*subflow_closed)(struct mptcp_sock *msk,
+			      struct mptcp_pm_addr_entry *local,
+			      struct mptcp_addr_info *remote);
+	int (*get_local_id)(struct mptcp_sock *msk,
+			    struct mptcp_pm_addr_entry *skc);
+	bool (*get_priority)(struct mptcp_sock *msk,
+			     struct mptcp_addr_info *skc);
+	int (*set_priority)(struct mptcp_sock *msk,
+			    struct mptcp_pm_addr_entry *local,
+			    struct mptcp_addr_info *remote);
+	int (*listener_created)(struct mptcp_sock *msk);
+	int (*listener_closed)(struct mptcp_sock *msk);
+
+	u8			type;
+	struct module		*owner;
+	struct list_head	list;
+
+	void (*init)(struct mptcp_sock *msk);
+	void (*release)(struct mptcp_sock *msk);
+} ____cacheline_aligned_in_smp;
+
 #ifdef CONFIG_MPTCP
 void mptcp_init(void);
 
diff --git a/net/mptcp/pm.c b/net/mptcp/pm.c
index 16cacce6c10f..344bc477c502 100644
--- a/net/mptcp/pm.c
+++ b/net/mptcp/pm.c
@@ -6,12 +6,17 @@
 #define pr_fmt(fmt) "MPTCP: " fmt
 
 #include <linux/kernel.h>
+#include <linux/rculist.h>
+#include <linux/spinlock.h>
 #include <net/mptcp.h>
 #include "protocol.h"
 
 #include "mib.h"
 #include "mptcp_pm_gen.h"
 
+static DEFINE_SPINLOCK(mptcp_pm_list_lock);
+static LIST_HEAD(mptcp_pm_list);
+
 /* path manager command handlers */
 
 int mptcp_pm_announce_addr(struct mptcp_sock *msk,
@@ -644,3 +649,57 @@ void __init mptcp_pm_init(void)
 {
 	mptcp_pm_nl_init();
 }
+
+/* Must be called with rcu read lock held */
+struct mptcp_pm_ops *mptcp_pm_find(enum mptcp_pm_type type)
+{
+	struct mptcp_pm_ops *pm;
+
+	list_for_each_entry_rcu(pm, &mptcp_pm_list, list) {
+		if (pm->type == type)
+			return pm;
+	}
+
+	return NULL;
+}
+
+int mptcp_pm_validate(struct mptcp_pm_ops *pm)
+{
+	if (!pm->created && !pm->established && !pm->closed &&
+	    !pm->address_announced && !pm->address_removed &&
+	    !pm->subflow_established && !pm->subflow_closed &&
+	    !pm->get_local_id && !pm->get_priority && !pm->set_priority &&
+	    !pm->listener_created && !pm->listener_closed) {
+		pr_err("%u does not implement required ops\n", pm->type);
+		return -EINVAL;
+	}
+
+	return 0;
+}
+
+int mptcp_pm_register(struct mptcp_pm_ops *pm)
+{
+	int ret;
+
+	ret = mptcp_pm_validate(pm);
+	if (ret)
+		return ret;
+
+	spin_lock(&mptcp_pm_list_lock);
+	if (mptcp_pm_find(pm->type)) {
+		spin_unlock(&mptcp_pm_list_lock);
+		return -EEXIST;
+	}
+	list_add_tail_rcu(&pm->list, &mptcp_pm_list);
+	spin_unlock(&mptcp_pm_list_lock);
+
+	pr_debug("userspace_pm type %u registered\n", pm->type);
+	return 0;
+}
+
+void mptcp_pm_unregister(struct mptcp_pm_ops *pm)
+{
+	spin_lock(&mptcp_pm_list_lock);
+	list_del_rcu(&pm->list);
+	spin_unlock(&mptcp_pm_list_lock);
+}
diff --git a/net/mptcp/protocol.h b/net/mptcp/protocol.h
index bac5c925a72f..93445c24de93 100644
--- a/net/mptcp/protocol.h
+++ b/net/mptcp/protocol.h
@@ -1047,6 +1047,11 @@ int mptcp_pm_remove_addr(struct mptcp_sock *msk, const struct mptcp_rm_list *rm_
 void mptcp_pm_remove_addr_entry(struct mptcp_sock *msk,
 				struct mptcp_pm_addr_entry *entry);
 
+struct mptcp_pm_ops *mptcp_pm_find(enum mptcp_pm_type type);
+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);
+
 void mptcp_free_local_addr_list(struct mptcp_sock *msk);
 
 void mptcp_event(enum mptcp_event_type type, const struct mptcp_sock *msk,
-- 
2.43.0