TUN/TAP device is stuck on read

[Ramon Fried]

Hi !
I've written a TUN device in user space and it works well.
Sometimes however, it appears that connectivity stops. no packets are transferred.
I manage to produce the issue only when I run iperf for a long time for testing the throughput.

Digging deeper, it looks that the application is blocked on reading from the tun device.
I opened the verbosity of the logs in the kernel tun driver (drivers/net/tun.c) and it doesn't seem that packets arrive to it's queue.

How can I debug it further ?
I'm new to kernel network stack, and I'm looking for a way to track the packet (for instance ping) through the stack until it reaches the queue in the tun driver.

IE.	

$ ping 10.0.0.2

I should be able to trace that ICMP packet all along the way to understand where it was dropped.


BTW - 
The network statics in ifconfig don't show any drop of packets.

Thanks A lot.