NETLINK: Add unicast release notifier.

include/linux/netlink.h

@@ -110,6 +110,8 @@ extern int netlink_unicast(struct sock *ssk, struct sk_buff *skb, __u32 pid, int
 extern void netlink_broadcast(struct sock *ssk, struct sk_buff *skb, __u32 pid,
 			      __u32 group, int allocation);
 extern void netlink_set_err(struct sock *ssk, __u32 pid, __u32 group, int code);
+extern int netlink_register_notifier(struct notifier_block *nb);
+extern int netlink_unregister_notifier(struct notifier_block *nb);
 
 /*
  *	skb should fit one page. This choice is good for headerless malloc.
@@ -129,6 +131,12 @@ struct netlink_callback
 	long		args[4];
 };
 
+struct netlink_notify
+{
+	int pid;
+	int protocol;
+};
+
 static __inline__ struct nlmsghdr *
 __nlmsg_put(struct sk_buff *skb, u32 pid, u32 seq, int type, int len)
 {

include/linux/notifier.h

@@ -58,5 +58,7 @@ extern int notifier_call_chain(struct notifier_block **n, unsigned long val, voi
 #define SYS_HALT	0x0002	/* Notify of system halt */
 #define SYS_POWER_OFF	0x0003	/* Notify of system power off */
 
+#define NETLINK_URELEASE	0x0001	/* Unicast netlink socket released */
+
 #endif /* __KERNEL__ */
 #endif /* _LINUX_NOTIFIER_H */

net/netlink/af_netlink.c

@@ -41,6 +41,7 @@
 #include <linux/rtnetlink.h>
 #include <linux/proc_fs.h>
 #include <linux/smp_lock.h>
+#include <linux/notifier.h>
 #include <net/sock.h>
 #include <net/scm.h>
 
@@ -81,6 +82,8 @@ atomic_t netlink_sock_nr;
 static rwlock_t nl_table_lock = RW_LOCK_UNLOCKED;
 static atomic_t nl_table_users = ATOMIC_INIT(0);
 
+static struct notifier_block *netlink_chain;
+
 static void netlink_sock_destruct(struct sock *sk)
 {
 	skb_queue_purge(&sk->receive_queue);
@@ -276,6 +279,12 @@ static int netlink_release(struct socket *sock)
 
 	skb_queue_purge(&sk->write_queue);
 
+	if (sk->protinfo.af_netlink->pid && !sk->protinfo.af_netlink->groups) {
+		struct netlink_notify n = { protocol:sk->protocol,
+		                            pid:sk->protinfo.af_netlink->pid };
+		notifier_call_chain(&netlink_chain, NETLINK_URELEASE, &n);
+	}	
+	
 	sock_put(sk);
 	return 0;
 }
@@ -967,6 +976,16 @@ static int netlink_read_proc(char *buffer, char **start, off_t offset,
 }
 #endif
 
+int netlink_register_notifier(struct notifier_block *nb)
+{
+	return notifier_chain_register(&netlink_chain, nb);
+}
+
+int netlink_unregister_notifier(struct notifier_block *nb)
+{
+	return notifier_chain_unregister(&netlink_chain, nb);
+}
+                
 struct proto_ops netlink_ops = {
 	family:		PF_NETLINK,
 

net/netsyms.c

@@ -402,6 +402,8 @@ EXPORT_SYMBOL(netlink_unicast);
 EXPORT_SYMBOL(netlink_kernel_create);
 EXPORT_SYMBOL(netlink_dump_start);
 EXPORT_SYMBOL(netlink_ack);
+EXPORT_SYMBOL(netlink_register_notifier);
+EXPORT_SYMBOL(netlink_unregister_notifier);
 #if defined(CONFIG_NETLINK_DEV) || defined(CONFIG_NETLINK_DEV_MODULE)
 EXPORT_SYMBOL(netlink_attach);
 EXPORT_SYMBOL(netlink_detach);