Re: libnetfilter_conntrack, nfct_catch returns ENOBUFS

[Pablo Neira Ayuso <pablo@netfilter.org>]

fabien.marotte@mindspeed.com wrote:
> I develop an application using libnetfilter_conntrack to catch events 
> happening in the conntrack system.
> I am currently testing the robustness of my application using ab tool 
> (connection stress).
> 
> libnetfilter_conntrack version is 0.50. I use the new API.
> My callback catching the events always returns NFCT_CB_CONTINUE meaning 
> that ncft_catch should never returns.
> 
> But with 20 (and more) TCP  connections opening simultaneously, nfct_catch 
> returns. The error code in errno is 105. Seems to be ENOBUFS.
> 
> Looking at the code, I see the comment "ENOBUFS is returned in case that 
> nfnetlink is exhausted".
> 
> I am very surprised to have memory issues with so few connections.

So am I. Could you post the code?

> Could you explain me why this error occurs ? Is this a kernel error 
> propagated in user space or is this a user space error ?

Default buffer size in your system? cat /proc/sys/net/core/rmem_default

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