Eric Dumazet wrote:
> On Wed, 31 Oct 2007 22:19:43 +0300
> Pavel Emelyanov <xemul@openvz.org> wrote:
> 
>> Currently we have the NET_NS config option, but the only change it 
>> makes is just return ERR_PTR(-EINVAL) inside the cloning call thus
>> introducing a bunch of a dead code and making the reference counting
>> unneeded. This is not very good.
>>
>> So clean the net_namespace.c to fix this.
>>
>> I have sent a set of patches to Andrew to make similar thing for
>> other namespaces, which introduces the NAMESPACES option to turn
>> all the namespaces off at once (to make embedded people suffer
>> less). So after that stuff is in, there will be some more patches 
>> to tie all this together.
>>
>> What is to be done after this set is to make the register_pernet_xxx
>> stuff smaller. Currently this code weights approximately 500 bytes, 
>> so it worths reducing it, but I haven't found a good solution yet.
> 
> Definitly wanted here. Thank you.
> One more refcounting on each socket creation/deletion was expensive.
> 
> Maybe we can add a macro to get nd_net from a "struct net_device"
> so that every instance of
> 
> if (dev->nd_net != &init_net)
>     goto drop;
> 
> can also be optimized away if !CONFIG_NET_NS
> 
> extern inline netdev_get_ns(struct netdevice *dev)
> {
> #ifdef CONFIG_NET_NS
> 	return dev->nd_net;
> #else
> 	return &init_net;
> #endif
> }

Or something like:

#ifdef CONFIG_NET_NS
static inline int init_net_dev(struct net_device *dev)
{
	return dev->nd_net == &init_net;
}
#else
static inline int init_net_dev(struct net_device *dev)
{
	return 1;
}
#endif


By the way, this kind of test will disappear when the network namespace 
will be complete and take into account the differents protocols.