[NETFILTER]: nfnetlink_log: fix sending of multipart messages

The following patch fixes the handling of netlink packets containing
multiple messages.

As exposed during netfilter workshop, nfnetlink_log was overwritten the
message type of the last message (setting it to MSG_DONE) in a multipart
packet. The consequence was libnfnetlink to ignore the last message in the
packet.

The following patch adds a supplementary message (with type MSG_DONE) af
the end of the netlink skb.

Signed-off-by: Eric Leblond <eric@inl.fr>
Signed-off-by: Patrick McHardy <kaber@trash.net>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 7 insertions, 6 deletions

diff --git a/net/netfilter/nfnetlink_log.c b/net/netfilter/nfnetlink_log.c
index e185a5b55913..2351533a8507 100644
--- a/net/netfilter/nfnetlink_log.c
+++ b/net/netfilter/nfnetlink_log.c
@@ -58,7 +58,6 @@ struct nfulnl_instance {
 
         unsigned int qlen;              /* number of nlmsgs in skb */
         struct sk_buff *skb;            /* pre-allocatd skb */
-        struct nlmsghdr *lastnlh;       /* netlink header of last msg in skb */
         struct timer_list timer;
         int peer_pid;                   /* PID of the peer process */
 
@@ -345,10 +344,12 @@ static struct sk_buff *nfulnl_alloc_skb(unsigned int inst_size,
 static int
 __nfulnl_send(struct nfulnl_instance *inst)
 {
-        int status;
+        int status = -1;
 
         if (inst->qlen > 1)
-                inst->lastnlh->nlmsg_type = NLMSG_DONE;
+                NLMSG_PUT(inst->skb, 0, 0,
+                          NLMSG_DONE,
+                          sizeof(struct nfgenmsg));
 
         status = nfnetlink_unicast(inst->skb, inst->peer_pid, MSG_DONTWAIT);
         if (status < 0) {
@@ -358,8 +359,8 @@ __nfulnl_send(struct nfulnl_instance *inst)
 
         inst->qlen = 0;
         inst->skb = NULL;
-        inst->lastnlh = NULL;
 
+nlmsg_failure:
         return status;
 }
 
@@ -538,7 +539,6 @@ __build_packet_message(struct nfulnl_instance *inst,
         }
 
         nlh->nlmsg_len = inst->skb->tail - old_tail;
-        inst->lastnlh = nlh;
         return 0;
 
 nlmsg_failure:
@@ -644,7 +644,8 @@ nfulnl_log_packet(unsigned int pf,
         }
 
         if (inst->qlen >= qthreshold ||
-            (inst->skb && size > skb_tailroom(inst->skb))) {
+            (inst->skb && size >
+             skb_tailroom(inst->skb) - sizeof(struct nfgenmsg))) {
                 /* either the queue len is too high or we don't have
                  * enough room in the skb left. flush to userspace. */
                 UDEBUG("flushing old skb\n");