Re: [Lse-tech] Re: A common layer for Accounting packages

jamal
2005-02-28T13:41:59Z

netlink broadcast or a wrapper around it.
Why even bother doing the check with netlink_has_listeners()?

cheers,
jamal

On Mon, 2005-02-28 at 08:20, Thomas Graf wrote:
> > Havent seen the beginnings of this thread. But whatever you are trying
> > to do seems to suggest some complexity that you are trying to
> > workaround. What was wrong with just going ahead and just always
> > invoking your netlink_send()?
>
> I guess parts of the wheel are broken and need to be reinvented ;->
>
> > If there are nobody in user space (or kernel) listening, it wont go anywhere.
>
> Additional you may want to extend netlink a bit to check whether
> there is a listener before creating the messages. The method to do so
> depends on whether you use netlink_send() or netlink_brodacast(). The
> latter is more flexiable because you can add more groups later on
> and the userspace applications can decicde which ones they want to
> listen to. Both methods handle dying clients perfectly fine, the
> association to the netlink socket gets destroyed as soon as the socket
> is closed. Therefore you can simply check mc_list of the netlink
> protocol you use to see if there are any listeners registered:
>
> static inline int netlink_has_listeners(struct sock *sk)
> {
> int ret;
>
> read_lock(&nl_table_lock);
> ret = list_empty(&nl_table[sk->sk_protocol].mc_list)
> read_unlock(&nl_table_lock);
>
> return !ret;
> }
>
> This is simplified and ignores the actual group assignments, i.e. you
> might want to extend it to have it check if there are listeners for
> a certain group.
>