Re: [Devel] [PATCH 1/5] net: Modify all rtnetlink methods to only work in the initial namespace

["Denis V. Lunev" <den@sw.ru>]

Eric W. Biederman wrote:
> Before I can enable rtnetlink to work in all network namespaces
> I need to be certain that something won't break.  So this
> patch deliberately disables all of the rtnletlink methods in everything
> except the initial network namespace.  After the methods have been
> audited this extra check can be disabled.
>
[...]
>  static int br_dump_ifinfo(struct sk_buff *skb, struct netlink_callback *cb)
>  {
> +	struct net *net = skb->sk->sk_net;
>  	struct net_device *dev;
>  	int idx;
>  

I've read some code today greping 'init_net.loopback_dev' and found
interesting non-trivial for me issue.

Network namespace is extracted from the packet in two different ways in
TCP. This is a socket for outgoing path and a device for incoming.
Though, there are some places called uniformly both from incoming and
outgoing path.

Typical example is netfilters. They are called uniformly all around the
code. The prototype is the following:

static unsigned int reject6_target(struct sk_buff **pskb,
                           const struct net_device *in,
                           const struct net_device *out,
                           unsigned int hooknum,
                           const struct xt_target *target,
                           const void *targinfo);

So, we are bound to the following options:
- perform additional non-uniform hacks around to place 'struct net' into
  other and other structures like xt_target
- add 7th parameter here and over
- introduce an skb_net field in the 'struct sk_buff' making all code
  uniform, at least when we have an skb

I think that this is not the last place with such a parameter list and
we should make a decision at this point when the code in not mainline yet.

As far as I understand, netfilters are not touched by the Eric and we
can face some non-trivial problems there.

So, if my point about uniformity is valid, this patchset looks wrong and
should be re-worked :(

Regards,
	Den