mptcp: add mptcp_validate_scheduler helper

New interface .validate is added in struct bpf_struct_ops recently, this
patch implements it as a new helper mptcp_validate_scheduler() for struct
mptcp_sched_ops.

In this helper, check whether the required ops "get_subflow" of struct
mptcp_sched_ops has been implemented.

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

Author: Geliang Tang

net/mptcp/protocol.h

@@ -740,6 +740,7 @@ void mptcp_info2sockaddr(const struct mptcp_addr_info *info,
 			 struct sockaddr_storage *addr,
 			 unsigned short family);
 struct mptcp_sched_ops *mptcp_sched_find(const char *name);
+int mptcp_validate_scheduler(struct mptcp_sched_ops *sched);
 int mptcp_register_scheduler(struct mptcp_sched_ops *sched);
 void mptcp_unregister_scheduler(struct mptcp_sched_ops *sched);
 void mptcp_sched_init(void);

net/mptcp/sched.c

@@ -82,10 +82,23 @@ void mptcp_get_available_schedulers(char *buf, size_t maxlen)
 	rcu_read_unlock();
 }
 
-int mptcp_register_scheduler(struct mptcp_sched_ops *sched)
+int mptcp_validate_scheduler(struct mptcp_sched_ops *sched)
 {
-	if (!sched->get_send)
+	if (!sched->get_send) {
+		pr_err("%s does not implement required ops\n", sched->name);
 		return -EINVAL;
+	}
+
+	return 0;
+}
+
+int mptcp_register_scheduler(struct mptcp_sched_ops *sched)
+{
+	int ret;
+
+	ret = mptcp_validate_scheduler(sched);
+	if (ret)
+		return ret;
 
 	spin_lock(&mptcp_sched_list_lock);
 	if (mptcp_sched_find(sched->name)) {