Re: Waiting for user space response in Kernel Mode

[Pablo Neira Ayuso <pablo@eurodev.net>]

Guru Prasad wrote:
> I am a newbie to Kernel and Netfilter development.
>   
> When a new connection with specific parameters (for
> example a certain destination IP address) is created,
> I would like to indicate this event to a daemon
> process in user space which takes some decision before
> proceeding. I detect this event from 
> ip_conntrack_netlink.c in the following function.
>   
>   int ctnetlink_conntrack_event(struct notifier_block 
> *this,                                     
> unsigned long events, void *ptr) -->    "if (events & 
> (IPCT_NEW | 
> IPCT_RELATED)) {"
>   
> When I detect a new connection,I tried to use
> Wait_queues and call schedule() so that I could wait
> on this process before receiving response from user
> space, but using this mechanism leads to crashes. It
> seems that one can only use this mechanism (wait
> queues and schedule)  when a process is executing in
> the context of a user space application.  

Yes, ctnetlink_conntrack_event is always called from interrupt context.
Don't do that in kernelspace. Use libnetfilter_conntrack and work in
userspace please.

-- 
Pablo