netdev - Re: macvtap: Limit packet queue length

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Message-Id: <201007230928.09064.arnd@arndb.de>
Date:	Fri, 23 Jul 2010 09:28:08 +0200
From:	Arnd Bergmann <arnd@...db.de>
To:	David Miller <davem@...emloft.net>
Cc:	herbert@...dor.apana.org.au, mashirle@...ibm.com,
	netdev@...r.kernel.org, mwagner@...hat.com
Subject: Re: macvtap: Limit packet queue length

On Thursday 22 July 2010, David Miller wrote:
> From: Herbert Xu <herbert@...dor.apana.org.au>
> Date: Fri, 23 Jul 2010 00:07:31 +0800
> 
> > On Thu, Jul 22, 2010 at 08:59:58AM -0700, Shirley Ma wrote:
> >> On Thu, 2010-07-22 at 14:41 +0800, Herbert Xu wrote:
> >> >  {
> >> >         struct macvtap_queue *q = macvtap_get_queue(dev, skb);
> >> >         if (!q)
> >> > -               return -ENOLINK;
> >> > +               goto drop;
> >> > +
> >> > +       if (skb_queue_len(&q->sk.sk_receive_queue) >=
> >> > dev->tx_queue_len)
> >> > +               goto drop;
> >> > 
> >> 
> >> Do we need to orphan skb here, just like tun?
> > 
> > We could, but that is orthogonal to the problem at hand so feel
> > free to do that in another patch.
> 
> These days, the stack pre-orphans all packets sent to ->ndo_start_xmit()
> in dev_hard_start_xmit() as long as socket based TX timestamping is not
> active for the packet.

But this is the receive path, not transmit, so a packet coming from an
external NIC never goes through dev_hard_start_xmit.

	Arnd
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