ipq and nf_queue compatibility

[Patrick McHardy]

robert wrote:
> Hello,
> 
> I am porting a program that uses IPQ to NF_QUEUE, and the port went 
> very smoothly, but I noticed that if I run the nfqueue version once, 
> the ipq version stops working.  The NF_QUEUE version always works,  but
> the other one simple stops functioning.  Is there a known 
> incompatibility between the two?  Or perhaps is there some global  state
> that I need to cleanup inside of the NFQUEUE version before I  execute
> the IPQ version.  The kernel has both IPQ and NFQUEUE support.
> 
> This happens regardless of whether or not I call the function 
> nfq_unbind_pf on exit.  Not really sure what that function does, but  it
> was inside of nfqnl_test.c, so I tried it out.

ip_queue only registeres itself when the module is loaded,
nfnetlink_queue registeres when NFQNL_CFG_CMD_PF_BIND is
received. So once ip_queue has been unregistered it never
registeres again and doesn't receive any packets anymore.