[NETLINK]: Introduce NLMSG_NEW macro to better handle netlink flags

Introduces a new macro NLMSG_NEW which extends NLMSG_PUT but takes
a flags argument. NLMSG_PUT stays there for compatibility but now
calls NLMSG_NEW with flags == 0. NLMSG_PUT_ANSWER is renamed to
NLMSG_NEW_ANSWER which now also takes a flags argument.

Also converts the users of NLMSG_PUT_ANSWER to use NLMSG_NEW_ANSWER
and fixes the two direct users of __nlmsg_put to either provide
the flags or use NLMSG_NEW(_ANSWER).

Signed-off-by: Thomas Graf <tgraf@suug.ch>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/net/netlink/af_netlink.c b/net/netlink/af_netlink.c
index e41ce45..70bcd47 100644
--- a/net/netlink/af_netlink.c
+++ b/net/netlink/af_netlink.c
@@ -1095,8 +1095,7 @@
 		return 0;
 	}
 
-	nlh = __nlmsg_put(skb, NETLINK_CB(cb->skb).pid, cb->nlh->nlmsg_seq, NLMSG_DONE, sizeof(int));
-	nlh->nlmsg_flags |= NLM_F_MULTI;
+	nlh = NLMSG_NEW_ANSWER(skb, cb, NLMSG_DONE, sizeof(len), NLM_F_MULTI);
 	memcpy(NLMSG_DATA(nlh), &len, sizeof(len));
 	skb_queue_tail(&sk->sk_receive_queue, skb);
 	sk->sk_data_ready(sk, skb->len);
@@ -1107,6 +1106,9 @@
 
 	netlink_destroy_callback(cb);
 	return 0;
+
+nlmsg_failure:
+	return -ENOBUFS;
 }
 
 int netlink_dump_start(struct sock *ssk, struct sk_buff *skb,
@@ -1178,7 +1180,7 @@
 	}
 
 	rep = __nlmsg_put(skb, NETLINK_CB(in_skb).pid, nlh->nlmsg_seq,
-			  NLMSG_ERROR, sizeof(struct nlmsgerr));
+			  NLMSG_ERROR, sizeof(struct nlmsgerr), 0);
 	errmsg = NLMSG_DATA(rep);
 	errmsg->error = err;
 	memcpy(&errmsg->msg, nlh, err ? nlh->nlmsg_len : sizeof(struct nlmsghdr));