genetlink: Add genl_notify()

Open vSwitch uses Generic Netlink interface for communication
between userspace and kernel module. genl_notify() is used
for sending notification back to userspace.

genl_notify() is analogous to rtnl_notify() but uses genl_sock
instead of rtnl.
Signed-off-by: Pravin B Shelar <pshelar@nicira.com>
Signed-off-by: Jesse Gross <jesse@nicira.com>

include/net/genetlink.h

@@ -128,6 +128,8 @@ extern int genl_register_mc_group(struct genl_family *family,
 				  struct genl_multicast_group *grp);
 extern void genl_unregister_mc_group(struct genl_family *family,
 				     struct genl_multicast_group *grp);
+extern void genl_notify(struct sk_buff *skb, struct net *net, u32 pid,
+			u32 group, struct nlmsghdr *nlh, gfp_t flags);
 
 /**
  * genlmsg_put - Add generic netlink header to netlink message

net/netlink/genetlink.c

@@ -946,3 +946,16 @@ int genlmsg_multicast_allns(struct sk_buff *skb, u32 pid, unsigned int group,
 	return genlmsg_mcast(skb, pid, group, flags);
 }
 EXPORT_SYMBOL(genlmsg_multicast_allns);
+
+void genl_notify(struct sk_buff *skb, struct net *net, u32 pid, u32 group,
+		 struct nlmsghdr *nlh, gfp_t flags)
+{
+	struct sock *sk = net->genl_sock;
+	int report = 0;
+
+	if (nlh)
+		report = nlmsg_report(nlh);
+
+	nlmsg_notify(sk, skb, pid, group, report, flags);
+}
+EXPORT_SYMBOL(genl_notify);