[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>

3 files changed, 19 insertions, 14 deletions

diff --git a/include/linux/netlink.h b/include/linux/netlink.h
index 8d1cb419a930..e38407a23d04 100644
--- a/include/linux/netlink.h
+++ b/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); \
diff --git a/net/core/neighbour.c b/net/core/neighbour.c
index 2296a145fb78..0fb742e228cc 100644
--- a/net/core/neighbour.c
+++ b/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);
 
diff --git a/net/netlink/af_netlink.c b/net/netlink/af_netlink.c
index e41ce458c2a9..70bcd4744d93 100644
--- a/net/netlink/af_netlink.c
+++ b/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));