[Devel] Re: [PATCH 5/9] network namespaces: async socket operations

[Andrey Savochkin]

On Fri, Sep 22, 2006 at 05:33:56PM +0200, Daniel Lezcano wrote:
> Andrey Savochkin wrote:
> > Non-trivial part of socket namespaces: asynchronous events
> > should be run in proper context.
> > 
> > Signed-off-by: Andrey Savochkin <saw at swsoft.com>
> > ---
> >  af_inet.c            |   10 ++++++++++
> >  inet_timewait_sock.c |    8 ++++++++
> >  tcp_timer.c          |    9 +++++++++
> >  3 files changed, 27 insertions(+)
> > 
> > --- ./net/ipv4/af_inet.c.venssock-asyn	Mon Aug 14 17:04:07 2006
> > +++ ./net/ipv4/af_inet.c	Tue Aug 15 13:45:44 2006
> > @@ -366,10 +366,17 @@ out_rcu_unlock:
> >  int inet_release(struct socket *sock)
> >  {
> >  	struct sock *sk = sock->sk;
> > +	struct net_namespace *ns, *orig_net_ns;
> >  
> >  	if (sk) {
> >  		long timeout;
> >  
> > +		/* Need to change context here since protocol ->close
> > +		 * operation may send packets.
> > +		 */
> > +		ns = get_net_ns(sk->sk_net_ns);
> > +		push_net_ns(ns, orig_net_ns);
> > +
> 
> Is it not a race condition here ? What happens if you have a packet 
> incoming during the namespace context switching ?

All asynchronous operations (RX softirq, timers) should set their context
explicitly, and can't rely on the current context being the right one
(or a valid pointer at all).

	Andrey