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netfilter: nfnetlink_queue: honor NFQA_CFG_F_FAIL_OPEN when netlink unicast fails 

When netlink unicast fails to deliver the message to userspace, we
should also check if the NFQA_CFG_F_FAIL_OPEN flag is set so we reinject
the packet back to the stack.

I think the user expects no packet drops when this flag is set due to
queueing to userspace errors, no matter if related to the internal queue
or when sending the netlink message to userspace.

The userspace application will still get the ENOBUFS error via recvmsg()
so the user still knows that, with the current configuration that is in
place, the userspace application is not consuming the messages at the
pace that the kernel needs.

Reported-by: "Yigal Reiss (yreiss)" <yreiss@cisco.com>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
Tested-by: "Yigal Reiss (yreiss)" <yreiss@cisco.com>
This commit is contained in:
Pablo Neira Ayuso 2016-03-23 12:58:01 +01:00
parent 54d83fc74a
commit 931401137f
1 changed files with 6 additions and 1 deletions
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7
net/netfilter/nfnetlink_queue.c
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@ -582,7 +582,12 @@ __nfqnl_enqueue_packet(struct net *net, struct nfqnl_instance *queue,
/* nfnetlink_unicast will either free the nskb or add it to a socket */
err = nfnetlink_unicast(nskb, net, queue->peer_portid, MSG_DONTWAIT);
if (err < 0) {
queue->queue_user_dropped++;
if (queue->flags & NFQA_CFG_F_FAIL_OPEN) {
failopen = 1;
err = 0;
} else {
queue->queue_user_dropped++;
}
goto err_out_unlock;
}