Re: Buffering and libnetfilter

[Kristian Evensen <kristian.evensen@gmail.com>]

Hello again,

After doing some more debugging, I have come a bit closer to answering 
my question. However, there is one thing still puzzling me.

I wrote a small application that uses select to multiplex between stdin 
and the kernelsocket. When a netfilter-packet arrives, the packet_id is 
registered in a list and the callback function returns 1. The user can 
input the id of the packet he or she wants to have sent, and I use 
nfq_set_verdict to allow the packet to continue its journey through the 
kernel.

When using this application, the same as with the test application 
occurs. If I don't allow any packets to continue through the kernel, 
netfilter_queue stops delivering new packets to the application after a 
little while (recv/select just blocks). However, when I input a corret 
id and allow the kernel to continue sending a packet, netfilter 
deliveres a new packet immideatly (where packet_id == 
prev_highest_packet_id + 1). So, my question now is, why do 
netfilter_queue stop delivering new packets in the first place? I have 
tried both tweaking the queue lenght (using nfnl_recv_bufsiz) and 
setting it to extremely high values, and played around with the 
proc-variables that control network memory consumption.

Thanks in advance for any help,
Kristian