netdev - Re: [PATCH net-next 2/2] mac802154: don't deliver packets to devices that are down

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Date:	Tue, 10 Jun 2014 17:32:26 +0200
From:	Phoebe Buckheister <phoebe.buckheister@...m.fraunhofer.de>
To:	Eric Dumazet <eric.dumazet@...il.com>
Cc:	netdev@...r.kernel.org, linux-zigbee-devel@...ts.sourceforge.net,
	davem@...emloft.net
Subject: Re: [PATCH net-next 2/2] mac802154: don't deliver packets to
 devices that are down

On Tue, 10 Jun 2014 08:26:01 -0700
Eric Dumazet <eric.dumazet@...il.com> wrote:

> On Tue, 2014-06-10 at 17:08 +0200, Phoebe Buckheister wrote:
> > Only one WPAN devices can be active at any given time, so only
> > deliver packets to that one interface that is actually up.
> > 
> > Signed-off-by: Phoebe Buckheister
> > <phoebe.buckheister@...m.fraunhofer.de> ---
> >  net/mac802154/wpan.c |   12 +++++++-----
> >  1 file changed, 7 insertions(+), 5 deletions(-)
> > 
> > diff --git a/net/mac802154/wpan.c b/net/mac802154/wpan.c
> > index c8cfd54..1ba648e 100644
> > --- a/net/mac802154/wpan.c
> > +++ b/net/mac802154/wpan.c
> > @@ -567,7 +567,6 @@ static int mac802154_parse_frame_start(struct
> > sk_buff *skb, void mac802154_wpans_rx(struct mac802154_priv *priv,
> > struct sk_buff *skb) {
> >  	int ret;
> > -	struct sk_buff *sskb;
> >  	struct mac802154_sub_if_data *sdata;
> >  	struct ieee802154_hdr hdr;
> >  
> > @@ -579,12 +578,15 @@ void mac802154_wpans_rx(struct mac802154_priv
> > *priv, struct sk_buff *skb) 
> >  	rcu_read_lock();
> >  	list_for_each_entry_rcu(sdata, &priv->slaves, list) {
> > -		if (sdata->type != IEEE802154_DEV_WPAN)
> > +		if (sdata->type != IEEE802154_DEV_WPAN ||
> > +		    !netif_running(sdata->dev))
> >  			continue;
> >  
> > -		sskb = skb_clone(skb, GFP_ATOMIC);
> > -		if (sskb)
> > -			mac802154_subif_frame(sdata, sskb, &hdr);
> > +		skb = skb_clone(skb, GFP_ATOMIC);
> > +		if (skb)
> > +			mac802154_subif_frame(sdata, skb, &hdr);
> > +
> > +		break;
> >  	}
> >  	rcu_read_unlock();
> >  }
> 
> If this is really the case, do not clone the skb, and fix
> mac802154_subif_rx().
> 
> (mac802154_wpans_rx() would always consume the skb)

That's also possible, I guess. mac802154_wpans_rx is the last call,
after all, and I didn't want to muck with that part of the stack too
much (it's already convoluted and not entirely clear). Monitor devices
will still have to clone their skb though - and they as well could
benefit from not queueing packets to inactive devices.

I'll change and resend.
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