netdev - Re: Flow Control and Port Mirroring Revisited

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Date:	Fri, 7 Jan 2011 07:01:12 +0900
From:	Simon Horman <horms@...ge.net.au>
To:	Eric Dumazet <eric.dumazet@...il.com>
Cc:	Rusty Russell <rusty@...tcorp.com.au>,
	virtualization@...ts.linux-foundation.org,
	Jesse Gross <jesse@...ira.com>, dev@...nvswitch.org,
	virtualization@...ts.osdl.org, netdev@...r.kernel.org,
	kvm@...r.kernel.org, "Michael S. Tsirkin" <mst@...hat.com>
Subject: Re: Flow Control and Port Mirroring Revisited

On Thu, Jan 06, 2011 at 02:28:18PM +0100, Eric Dumazet wrote:
> Le jeudi 06 janvier 2011 à 21:44 +0900, Simon Horman a écrit :
> 
> > Hi Eric !
> > 
> > Thanks for the advice. I had thought about the socket buffer but at some
> > point it slipped my mind.
> > 
> > In any case the following patch seems to implement the change that I had in
> > mind. However my discussions Michael Tsirkin elsewhere in this thread are
> > beginning to make me think that think that perhaps this change isn't the
> > best solution.
> > 
> > diff --git a/datapath/actions.c b/datapath/actions.c
> > index 5e16143..505f13f 100644
> > --- a/datapath/actions.c
> > +++ b/datapath/actions.c
> > @@ -384,7 +384,12 @@ static int do_execute_actions(struct datapath *dp, struct sk_buff *skb,
> >  
> >  	for (a = actions, rem = actions_len; rem > 0; a = nla_next(a, &rem)) {
> >  		if (prev_port != -1) {
> > -			do_output(dp, skb_clone(skb, GFP_ATOMIC), prev_port);
> > +			struct sk_buff *nskb = skb_clone(skb, GFP_ATOMIC);
> > +			if (nskb) {
> > +				if (skb->sk)
> > +					skb_set_owner_w(nskb, skb->sk);
> > +				do_output(dp, nskb, prev_port);
> > +			}
> >  			prev_port = -1;
> >  		}
> > 
> > I got a rather nasty panic without the if (skb->sk),
> > I guess some skbs don't have a socket.
> 
> Indeed, some packets are not linked to a socket.
> 
> (ARP packets for example)
> 
> Sorry, I should have mentioned it :)

Not at all, the occasional panic during hacking is good for the soul.
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