Re: PIM-SM namespace changes

[Pavel Emelyanov <xemul@openvz.org>]

David Miller wrote:
> From: Tom Goff <thomas.goff@boeing.com>
> Date: Tue, 19 May 2009 17:43:44 -0700
> 
>> For protocol registration I see three basic approaches for using PIM
>> with namespaces:
>>
>>   - unconditionally add PIM when multicast routing is initialized
>>     (maybe only ifdef CONFIG_NET_NS, otherwise preserve the current
>>     behavior)
>>
>>   - keep a count of the number of namespaces that have enabled PIM and
>>     add/delete PIM when transitioning from/to zero
>>
>>   - make all or some protocol registration per network namespace
>>
>> There are obviously tradeoffs and I would appreciate any
>> comments/suggestions on alternatives that allow namespace use of
>> dynamically enabled protocols.
> 
> Ok, I'm willing to accept your current approach for now, let's
> see what falls out of this.  Patch applied, thanks.
> 
> Doing the enabling per-namespace is complexity for an unknown
> gain.  I don't even know what the benefit could be for how we
> behaved previously.
> 
> Anyone know?

Well, maybe I do :)

I haven't thought much about per-namespace protocols, but I think, that
it makes sense to enable/disable at least virtual devices (tunnels and
vlans currently) per-namespace.

Not every namespace really needs this big amount of functionality and
saving sizeof(struct net_device) + private - the fallback devices each
tunnel creates, and this is somewhat around 4Kb each - sounds good.

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