ieee802154: add two nl802154 helpers

Add two nl802154 helpers: one for starting a reply message, one for sending.
Signed-off-by: Dmitry Eremin-Solenikov <dbaryshkov@gmail.com>

net/ieee802154/ieee802154.h

@@ -38,8 +38,13 @@ void __exit ieee802154_nl_exit(void);
 		.dumpit	= _dump,			\
 	}
 
+struct genl_info;
+
 struct sk_buff *ieee802154_nl_create(int flags, u8 req);
 int ieee802154_nl_mcast(struct sk_buff *msg, unsigned int group);
+struct sk_buff *ieee802154_nl_new_reply(struct genl_info *info,
+		int flags, u8 req);
+int ieee802154_nl_reply(struct sk_buff *msg, struct genl_info *info);
 
 extern struct genl_family nl802154_family;
 int nl802154_mac_register(void);

net/ieee802154/netlink.c

@@ -75,6 +75,39 @@ int ieee802154_nl_mcast(struct sk_buff *msg, unsigned int group)
 	return -ENOBUFS;
 }
 
+struct sk_buff *ieee802154_nl_new_reply(struct genl_info *info,
+		int flags, u8 req)
+{
+	void *hdr;
+	struct sk_buff *msg = nlmsg_new(NLMSG_GOODSIZE, GFP_ATOMIC);
+
+	if (!msg)
+		return NULL;
+
+	hdr = genlmsg_put_reply(msg, info,
+			&nl802154_family, flags, req);
+	if (!hdr) {
+		nlmsg_free(msg);
+		return NULL;
+	}
+
+	return msg;
+}
+
+int ieee802154_nl_reply(struct sk_buff *msg, struct genl_info *info)
+{
+	/* XXX: nlh is right at the start of msg */
+	void *hdr = genlmsg_data(NLMSG_DATA(msg->data));
+
+	if (genlmsg_end(msg, hdr) < 0)
+		goto out;
+
+	return genlmsg_reply(msg, info);
+out:
+	nlmsg_free(msg);
+	return -ENOBUFS;
+}
+
 int __init ieee802154_nl_init(void)
 {
 	int rc;