Re: [PATCH 1/4] [NETLINK]: Handle NLM_F_ECHO in netlink_rcv_skb()

[Thomas Graf <tgraf@suug.ch>]

* Alexey Kuznetsov <kuznet@ms2.inr.ac.ru> 2006-08-10 19:51
> > This patch handles NLM_F_ECHO in netlink_rcv_skb() to
> > handle it in a central point. Most subsystems currently
> > interpret NLM_F_ECHO as to just unicast events to the
> > originator of the change while the real meaning of the
> > flag is to echo the request.
> 
> Do not you think it is useless to echo something back to originator,
> who just sent it?
> 
> Actually, the sense of NLM_F_ECHO was to tell user what happened due to
> his request. The answer is not original request, which can contain
> some incomplete fields etc., but full information about object
> deleted/added/changed. Moreover, the feedback can contain several
> messages (though accurately it is done only in net/sched/), f.e. when
> the request triggered deletion of one object and addition of another.
> 
> Obviously, it cannot be done in a central place.
> 
> Normally, it is not needed, "ip route add" does not tell user, what
> actually was done, so that it suppresses echo. But for multistage
> operation it is absolutely necessary: the answer contains f.e. auto-allocated
> handles, which should be given in subsequent requests.

What's wrong with listening to the notification for that purpose?