Bug in Netfiler_queue when using small packets in 100Mb traffic

Bug in Netfiler_queue when using small packets in 100Mb traffic

[VPF]

Hi, I encountered a problem with the example nfqnl_test.c when I sent
100Mb/s of <200ko packets. The program stopped running quickly and
printed "unbinding from queue 0". It appears that the call recv(fd,
buf, sizeof(buf), 0) returns an error after a few packets. (errno 105
: No buffer space available).

Do you see any solution to this problem?

Re: Bug in Netfiler_queue when using small packets in 100Mb traffic

[Eric Leblond]

Hi,

Le samedi 03 janvier 2009 à 15:38 +0100, VPF a écrit :
> Hi, I encountered a problem with the example nfqnl_test.c when I sent
> 100Mb/s of <200ko packets. The program stopped running quickly and
> printed "unbinding from queue 0". It appears that the call recv(fd,
> buf, sizeof(buf), 0) returns an error after a few packets. (errno 105
> : No buffer space available).
> 
> Do you see any solution to this problem?

This problem is well known. This is linked with the size of the
nfnetlink buffer. The buffer is too small to contains the data when
trafic is high. A typical workaround is to increase this size. 

It can be done by using the nfnl_rcvbufsiz(). The code should looks
like:
 nfnl_rcvbufsiz(nfq_nfnlh(h), SIZE);

This workaround may not be sufficient and in this case a unbinding,
rebinding of the queue is needed.

BR,
-- 
Eric Leblond <eleblond@inl.fr>
INL: http://www.inl.fr/
NuFW: http://www.nufw.org/
EdenWall: http://www.edenwall.com/

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Re: Bug in Netfiler_queue when using small packets in 100Mb traffic

[Eric Leblond]

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Hi,

Le samedi 03 janvier 2009 à 15:38 +0100, VPF a écrit :
> Hi, I encountered a problem with the example nfqnl_test.c when I sent
> 100Mb/s of <200ko packets. The program stopped running quickly and
> printed "unbinding from queue 0". It appears that the call recv(fd,
> buf, sizeof(buf), 0) returns an error after a few packets. (errno 105
> : No buffer space available).
> 
> Do you see any solution to this problem?

This problem is well known. This is linked with the size of the
nfnetlink buffer. The buffer is too small to contains the data when
trafic is high. A typical workaround is to increase this size. 

It can be done by using the nfnl_rcvbufsiz(). The code should looks
like:
 nfnl_rcvbufsiz(nfq_nfnlh(h), SIZE);

This workaround may not be sufficient and in this case a unbinding,
rebinding of the queue is needed.

BR,
-- 
Eric Leblond <eleblond@inl.fr>
INL: http://www.inl.fr/
NuFW: http://www.nufw.org/
EdenWall: http://www.edenwall.com/

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