[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>

include/linux/netlink.h

@@ -156,7 +156,7 @@ struct netlink_notify
 };
 
 static __inline__ struct nlmsghdr *
-__nlmsg_put(struct sk_buff *skb, u32 pid, u32 seq, int type, int len)
+__nlmsg_put(struct sk_buff *skb, u32 pid, u32 seq, int type, int len, int flags)
 {
 	struct nlmsghdr *nlh;
 	int size = NLMSG_LENGTH(len);
@@ -164,20 +164,23 @@ __nlmsg_put(struct sk_buff *skb, u32 pid, u32 seq, int type, int len)
 	nlh = (struct nlmsghdr*)skb_put(skb, NLMSG_ALIGN(size));
 	nlh->nlmsg_type = type;
 	nlh->nlmsg_len = size;
-	nlh->nlmsg_flags = 0;
+	nlh->nlmsg_flags = flags;
 	nlh->nlmsg_pid = pid;
 	nlh->nlmsg_seq = seq;
 	return nlh;
 }
 
-#define NLMSG_PUT(skb, pid, seq, type, len) \
+#define NLMSG_NEW(skb, pid, seq, type, len, flags) \
 ({	if (skb_tailroom(skb) < (int)NLMSG_SPACE(len)) \
 		goto nlmsg_failure; \
-	__nlmsg_put(skb, pid, seq, type, len); })
+	__nlmsg_put(skb, pid, seq, type, len, flags); })
+
+#define NLMSG_PUT(skb, pid, seq, type, len) \
+	NLMSG_NEW(skb, pid, seq, type, len, 0)
 
-#define NLMSG_PUT_ANSWER(skb, cb, type, len) \
-	NLMSG_PUT(skb, NETLINK_CB((cb)->skb).pid, \
-		  (cb)->nlh->nlmsg_seq, type, len)
+#define NLMSG_NEW_ANSWER(skb, cb, type, len, flags) \
+	NLMSG_NEW(skb, NETLINK_CB((cb)->skb).pid, \
+		  (cb)->nlh->nlmsg_seq, type, len, flags)
 
 #define NLMSG_END(skb, nlh) \
 ({	(nlh)->nlmsg_len = (skb)->tail - (unsigned char *) (nlh); \

net/core/neighbour.c

@@ -1590,8 +1590,8 @@ static int neightbl_fill_info(struct neigh_table *tbl, struct sk_buff *skb,
 	struct nlmsghdr *nlh;
 	struct ndtmsg *ndtmsg;
 
-	nlh = NLMSG_PUT_ANSWER(skb, cb, RTM_NEWNEIGHTBL, sizeof(struct ndtmsg));
-	nlh->nlmsg_flags |= NLM_F_MULTI;
+	nlh = NLMSG_NEW_ANSWER(skb, cb, RTM_NEWNEIGHTBL, sizeof(struct ndtmsg),
+			       NLM_F_MULTI);
 
 	ndtmsg = NLMSG_DATA(nlh);
 
@@ -1675,8 +1675,8 @@ static int neightbl_fill_param_info(struct neigh_table *tbl,
 	struct ndtmsg *ndtmsg;
 	struct nlmsghdr *nlh;
 
-	nlh = NLMSG_PUT_ANSWER(skb, cb, RTM_NEWNEIGHTBL, sizeof(struct ndtmsg));
-	nlh->nlmsg_flags |= NLM_F_MULTI;
+	nlh = NLMSG_NEW_ANSWER(skb, cb, RTM_NEWNEIGHTBL, sizeof(struct ndtmsg),
+			       NLM_F_MULTI);
 
 	ndtmsg = NLMSG_DATA(nlh);
 

net/netlink/af_netlink.c

@@ -1095,8 +1095,7 @@ static int netlink_dump(struct sock *sk)
 		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 @@ static int netlink_dump(struct sock *sk)
 
 	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 @@ void netlink_ack(struct sk_buff *in_skb, struct nlmsghdr *nlh, int err)
 	}
 
 	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));