[GENL]: Add genlmsg_reply() to simply unicast replies to requests

A generic netlink user has no interest in knowing how to
address the source of the original request.

Signed-off-by: Thomas Graf <tgraf@suug.ch>
Acked-by: Paul Moore <paul.moore@hp.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

include/net/genetlink.h

@@ -149,6 +149,16 @@ static inline int genlmsg_unicast(struct sk_buff *skb, u32 pid)
 	return nlmsg_unicast(genl_sock, skb, pid);
 }
 
+/**
+ * genlmsg_reply - reply to a request
+ * @skb: netlink message to be sent back
+ * @info: receiver information
+ */
+static inline int genlmsg_reply(struct sk_buff *skb, struct genl_info *info)
+{
+	return genlmsg_unicast(skb, info->snd_pid);
+}
+
 /**
  * gennlmsg_data - head of message payload
  * @gnlh: genetlink messsage header