[PATCH v1 net 1/6] rtnetlink: Add bulk registration helpers for rtnetlink message handlers.

[Kuniyuki Iwashima <kuniyu@amazon.com>]

Before commit addf9b90de22 ("net: rtnetlink: use rcu to free rtnl message
handlers"), once rtnl_msg_handlers[protocol] was allocated, the following
rtnl_register_module() for the same protocol never failed.

However, after the commit, rtnl_msg_handler[protocol][msgtype] needs to
be allocated in each rtnl_register_module(), so each call could fail.

Many callers of rtnl_register_module() do not handle the returned error,
and we need to add many error handlings.

To handle that easily, let's add wrapper functions for bulk registration
of rtnetlink message handlers.

Signed-off-by: Kuniyuki Iwashima <kuniyu@amazon.com>
---
 include/net/rtnetlink.h | 19 +++++++++++++++++++
 net/core/rtnetlink.c    | 30 ++++++++++++++++++++++++++++++
 2 files changed, 49 insertions(+)

diff --git a/include/net/rtnetlink.h b/include/net/rtnetlink.h
index b45d57b5968a..b6b91898dc13 100644
--- a/include/net/rtnetlink.h
+++ b/include/net/rtnetlink.h
@@ -29,6 +29,14 @@ static inline enum rtnl_kinds rtnl_msgtype_kind(int msgtype)
 	return msgtype & RTNL_KIND_MASK;
 }
 
+struct rtnl_msg_handler {
+	int protocol;
+	int msgtype;
+	rtnl_doit_func doit;
+	rtnl_dumpit_func dumpit;
+	int flags;
+};
+
 void rtnl_register(int protocol, int msgtype,
 		   rtnl_doit_func, rtnl_dumpit_func, unsigned int flags);
 int rtnl_register_module(struct module *owner, int protocol, int msgtype,
@@ -36,6 +44,17 @@ int rtnl_register_module(struct module *owner, int protocol, int msgtype,
 int rtnl_unregister(int protocol, int msgtype);
 void rtnl_unregister_all(int protocol);
 
+int __rtnl_register_many(struct module *owner,
+			 struct rtnl_msg_handler *handlers, int n);
+void __rtnl_unregister_many(struct rtnl_msg_handler *handlers, int n);
+
+#define rtnl_register_many(handlers)						\
+	__rtnl_register_many(NULL, handlers, ARRAY_SIZE(handlers))
+#define rtnl_register_module_many(handlers)					\
+	__rtnl_register_many(THIS_MODULE, handlers, ARRAY_SIZE(handlers))
+#define rtnl_unregister_many(handlers)						\
+	__rtnl_unregister_many(handlers, ARRAY_SIZE(handlers))
+
 static inline int rtnl_msg_family(const struct nlmsghdr *nlh)
 {
 	if (nlmsg_len(nlh) >= sizeof(struct rtgenmsg))
diff --git a/net/core/rtnetlink.c b/net/core/rtnetlink.c
index f0a520987085..1fac9e786315 100644
--- a/net/core/rtnetlink.c
+++ b/net/core/rtnetlink.c
@@ -384,6 +384,36 @@ void rtnl_unregister_all(int protocol)
 }
 EXPORT_SYMBOL_GPL(rtnl_unregister_all);
 
+int __rtnl_register_many(struct module *owner,
+			 struct rtnl_msg_handler *handlers, int n)
+{
+	struct rtnl_msg_handler *handler;
+	int i, err;
+
+	for (i = 0, handler = handlers; i < n; i++, handler++) {
+		err = rtnl_register_internal(owner, handler->protocol,
+					     handler->msgtype, handler->doit,
+					     handler->dumpit, handler->flags);
+		if (err) {
+			__rtnl_unregister_many(handlers, i);
+			break;
+		}
+	}
+
+	return err;
+}
+EXPORT_SYMBOL_GPL(__rtnl_register_many);
+
+void __rtnl_unregister_many(struct rtnl_msg_handler *handlers, int n)
+{
+	struct rtnl_msg_handler *handler;
+	int i;
+
+	for (i = n - 1, handler = handlers + n - 1; i >= 0; i--, handler--)
+		rtnl_unregister(handler->protocol, handler->msgtype);
+}
+EXPORT_SYMBOL_GPL(__rtnl_unregister_many);
+
 static LIST_HEAD(link_ops);
 
 static const struct rtnl_link_ops *rtnl_link_ops_get(const char *kind)
-- 
2.30.2