netdev - Re: [RFC] netlink: add socket destruction notification

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Date:	Mon, 09 Nov 2009 14:19:15 +0100
From:	Patrick McHardy <kaber@...sh.net>
To:	Johannes Berg <johannes@...solutions.net>
CC:	netdev <netdev@...r.kernel.org>, Jouni Malinen <j@...fi>,
	Thomas Graf <tgraf@...g.ch>
Subject: Re: [RFC] netlink: add socket destruction notification

Johannes Berg wrote:
> On Mon, 2009-11-09 at 13:59 +0100, Patrick McHardy wrote:
> 
>>> Thanks for the explanation. I think we'd need the second condition
>>> removed, I don't see a reason to force a socket to not also have
>>> multicast RX if it's used for any of the purposes we're looking at this
>>> for. Guess we need to audit the callees to determine whether that's ok.
>> I've already done that. Its currently only used by netfilter
>> for which this change also makes sense.
> 
> Cool, I arrived at that conclusion too, it seemed that it would
> currently be somewhat strangely broken if you could add multicast groups
> to those sockets used there. Not sure if you can though.

I don't see anything preventing it.

>>> Can you quickly explain the difference between release and destruct?
>> release is called when the socket is closed, destruct is called
>> once all references are gone. I think with the synchonous processing
>> done nowadays they shouldn't make any difference, but release
>> should be fine in either case.
> 
> Ok, cool, thanks. Do you want me to send the change removing the
> multicast check, or would you want to do that since you audited all the
> netlink callers?

Please go ahead.

> Also, it's called URELEASE for unicast -- should we rename it to just
> RELEASE?

I think URELEASE is still fine since won't necessarily get called
for sockets that are used for pure multicast reception when using
setsockopt to bind to groups. I also have a cleanup patch removing
unneccessary nlk->pid checks from netfilter which would clash with
a rename :)
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