Hi all,
I am writing a kernel module that hooks into netfilter.
netfilter_ops.hook = main_hook;
netfilter_ops.pf = PF_INET;
netfilter_ops.hooknum = NF_IP_PRE_ROUTING;
netfilter_ops.priority = NF_IP_PRI_FIRST;
nf_register_hook(&netfilter_ops);

In the main_hook function, I needs to put the process to sleep and
will be woken up by another process because the decision to Accept or
Deny a packet depends on a process running in the user space. However,
all sleeping mechanisms I tried cause the kernel hang. I tried msleep,
wait_event_interrupt,wait_event_interrupt_timeout,... (of course I
have a process to wake up the main_hook process). I tested these
sleeping machenisms in different modules and they worked fine. My
question is can we make the process sleep in the main_hook function
without causing the kernel hang and how to do it?
Thank you very much.
Tung.

From what I know you can't do this this way. I'd rather place the packet on some list and continue the main loop. Then, after you receive the decision, you can find the right packet and perform the desired action.

Also, note that packets can be received very fast and your application may be simply too slow to pass decision in real-time!