Re: unregister_netdevice with negative refcnt error while using NFQUEUE with ebtables mark

[Patrick McHardy <kaber@trash.net>]

Jay Manni wrote:
> I have a bridge br0, with a couple of tap interfaces tap0, tap1 etc as part of it. I use the following ebtables rules to mark packets originating from a bridge port and destined to it.
> 
> ebtables -t broute -A BROUTING -i tap0 -p ipv4 -j mark --mark-set 10
> ebtables -t nat    -A POSTROUTING -o tap0 -p ipv4 -j mark --mark-set 20
> 
> Then the following iptables rules to send them to an NFQUEUE
> 
> iptables -t mangle -A PREROUTING  -m mark --mark 10 -j NFQUEUE --queue 5
> iptables -t mangle -A POSTROUTING -m mark --mark 20 -j NFQUEUE --queue 5 
> 
> The tap interfaces do not have any ip address configured.
> 
> Based on the detailed packet flow picture at http://ebtables.sourceforge.net/br_fw_ia/PacketFlow.png, I figured that the above rules would get me all the packets for the tap interface in question.
> 
> The process which attaches to NFQUEUE 5 does receive all the packets, and sets a verdict of NF_ACCEPT for each packet. However when I try to free the interfaces after it is done, I notice that the tap device has a negative refcnt.


I can't find the problem. Is there any relation between the number
of packets queued and the final refcount value?