+struct rtnl_link *rtnl_msg_handlers[NPROTO];
+
+static inline int rtm_msgindex(int msgtype)
+{
+ int msgindex = msgtype - RTM_BASE;
+
+ /*
+ * msgindex < 0 implies someone tried to register a netlink
+ * control code. msgindex >= RTM_NR_MSGTYPES may indicate that
+ * the message type has not been added to linux/rtnetlink.h
+ */
+ BUG_ON(msgindex < 0 || msgindex >= RTM_NR_MSGTYPES);
+
+ return msgindex;
+}
+
+static rtnl_doit_func rtnl_get_doit(int protocol, int msgindex)
+{
+ struct rtnl_link *tab;
+
+ tab = rtnl_msg_handlers[protocol];
+ if (tab == NULL || tab->doit == NULL)
+ tab = rtnl_msg_handlers[PF_UNSPEC];
+
+ return tab ? tab->doit : NULL;
+}
+
+static rtnl_dumpit_func rtnl_get_dumpit(int protocol, int msgindex)
+{
+ struct rtnl_link *tab;
+
+ tab = rtnl_msg_handlers[protocol];
+ if (tab == NULL || tab->dumpit == NULL)
+ tab = rtnl_msg_handlers[PF_UNSPEC];
+
+ return tab ? tab->dumpit : NULL;
+}
+
+/**
+ * __rtnl_register - Register a rtnetlink message type
+ * @protocol: Protocol family or PF_UNSPEC
+ * @msgtype: rtnetlink message type
+ * @doit: Function pointer called for each request message
+ * @dumpit: Function pointer called for each dump request (NLM_F_DUMP) message
+ *
+ * Registers the specified function pointers (at least one of them has
+ * to be non-NULL) to be called whenever a request message for the
+ * specified protocol family and message type is received.
+ *
+ * The special protocol family PF_UNSPEC may be used to define fallback
+ * function pointers for the case when no entry for the specific protocol
+ * family exists.
+ *
+ * Returns 0 on success or a negative error code.
+ */
+int __rtnl_register(int protocol, int msgtype,
+ rtnl_doit_func doit, rtnl_dumpit_func dumpit)
+{
+ struct rtnl_link *tab;
+ int msgindex;
+
+ BUG_ON(protocol < 0 || protocol >= NPROTO);
+ msgindex = rtm_msgindex(msgtype);
+
+ tab = rtnl_msg_handlers[protocol];
+ if (tab == NULL) {
+ tab = kcalloc(RTM_NR_MSGTYPES, sizeof(*tab), GFP_KERNEL);
+ if (tab == NULL)
+ return -ENOBUFS;
+
+ rtnl_msg_handlers[protocol] = tab;
+ }
+
+ if (doit)
+ tab[msgindex].doit = doit;
+
+ if (dumpit)
+ tab[msgindex].dumpit = dumpit;
+
+ return 0;
+}
+
+EXPORT_SYMBOL_GPL(__rtnl_register);
+
+/**
+ * rtnl_register - Register a rtnetlink message type
+ *
+ * Identical to __rtnl_register() but panics on failure. This is useful
+ * as failure of this function is very unlikely, it can only happen due
+ * to lack of memory when allocating the chain to store all message
+ * handlers for a protocol. Meant for use in init functions where lack
+ * of memory implies no sense in continueing.
+ */
+void rtnl_register(int protocol, int msgtype,
+ rtnl_doit_func doit, rtnl_dumpit_func dumpit)
+{
+ if (__rtnl_register(protocol, msgtype, doit, dumpit) < 0)
+ panic("Unable to register rtnetlink message handler, "
+ "protocol = %d, message type = %d\n",
+ protocol, msgtype);
+}
+
+EXPORT_SYMBOL_GPL(rtnl_register);
+
+/**
+ * rtnl_unregister - Unregister a rtnetlink message type
+ * @protocol: Protocol family or PF_UNSPEC
+ * @msgtype: rtnetlink message type
+ *
+ * Returns 0 on success or a negative error code.
+ */
+int rtnl_unregister(int protocol, int msgtype)
+{
+ int msgindex;
+
+ BUG_ON(protocol < 0 || protocol >= NPROTO);
+ msgindex = rtm_msgindex(msgtype);
+
+ if (rtnl_msg_handlers[protocol] == NULL)
+ return -ENOENT;
+
+ rtnl_msg_handlers[protocol][msgindex].doit = NULL;
+ rtnl_msg_handlers[protocol][msgindex].dumpit = NULL;
+
+ return 0;
+}
+
+EXPORT_SYMBOL_GPL(rtnl_unregister);
+
+/**
+ * rtnl_unregister_all - Unregister all rtnetlink message type of a protocol
+ * @protocol : Protocol family or PF_UNSPEC
+ *
+ * Identical to calling rtnl_unregster() for all registered message types
+ * of a certain protocol family.
+ */
+void rtnl_unregister_all(int protocol)
+{
+ BUG_ON(protocol < 0 || protocol >= NPROTO);
+
+ kfree(rtnl_msg_handlers[protocol]);
+ rtnl_msg_handlers[protocol] = NULL;
+}
+
+EXPORT_SYMBOL_GPL(rtnl_unregister_all);