nfnetlink_queue interfering with ioctl calls

nfnetlink_queue interfering with ioctl calls

[Roger Sala]

Hi

I tried posting this to the netfilter users list but I didn't get any 
response.  Maybe its a question for the devs?

I have code that makes the SIOCGARP ioctl call that works correctly 
(i.e. it either returns successfully when it finds a match in the arp 
cache or it returns -1).  However when I integrate that same code with 
nfnetlink_queue code it no longer works as expected (i.e. it returns 
successfully (0) when the address is not found in the arp cache and it 
doesn't copy anything into the struct arpreq).  I searched the archives 
and didn't see anything about this.  Does anyone have any idea what 
could be causing this?

Re: nfnetlink_queue interfering with ioctl calls

[Roger Sala]

On 08/13/2010 10:10 AM, Roger Sala wrote:
> Hi
>
> I have code that makes the SIOCGARP ioctl call that works correctly 
> (i.e. it either returns successfully when it finds a match in the arp 
> cache or it returns -1).  However when I integrate that same code with 
> nfnetlink_queue code it no longer works as expected (i.e. it returns 
> successfully (0) whether or not the address was found in the arp cache 
> and it doesn't copy the mac address into the struct arpreq).  I 
> searched the archives and didn't see anything about this.  Does anyone 
> have any idea what could be causing this?
>
>
Correction: the code actually does behave as expected if the address 
actually is in the arp cache.  It is only when it is not there that it's 
return value indicates success and nothing is copied into the struct 
arpreq.  The same code, on the same machine, running at the same time 
works as expected when not linked in with the nfnetlink_queue code.

nfnetlink_queue interfering with ioctl calls

[Roger Sala]

Hi

I have code that makes the SIOCGARP ioctl call that works correctly 
(i.e. it either returns successfully when it finds a match in the arp 
cache or it returns -1).  However when I integrate that same code with 
nfnetlink_queue code it no longer works as expected (i.e. it returns 
successfully (0) whether or not the address was found in the arp cache 
and it doesn't copy the mac address into the struct arpreq).  I searched 
the archives and didn't see anything about this.  Does anyone have any 
idea what could be causing this?

I'm running ...

# uname -a
Linux bugsbunny 2.6.30.9-102.fc11.i686.PAE #1 SMP Fri Dec 4 00:19:26 EST 
2009 i686 i686 i386 GNU/Linux

... and these two modules get loaded when the nfnetlink_queue code gets 
initialized ...

# /sbin/lsmod
Module                     Size  Used by
nfnetlink_queue       7548  1
nfnetlink                   3760  2 nfnetlink_queue

Thanks