From mboxrd@z Thu Jan 1 00:00:00 1970 From: Jarek Poplawski Subject: Re: [PATCH v2 2/3] net_sched: Add accessor function for packet length for qdiscs Date: Fri, 25 Jul 2008 12:08:49 +0000 Message-ID: <20080725120849.GA25369@ff.dom.local> References: <20080725.035712.33516738.davem@davemloft.net> <20080725113757.GC10399@ff.dom.local> <20080725115355.GD10399@ff.dom.local> <20080725.045215.10253476.davem@davemloft.net> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: jussi.kivilinna@mbnet.fi, kaber@trash.net, netdev@vger.kernel.org To: David Miller Return-path: Received: from ik-out-1112.google.com ([66.249.90.181]:30064 "EHLO ik-out-1112.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752350AbYGYMDm (ORCPT ); Fri, 25 Jul 2008 08:03:42 -0400 Received: by ik-out-1112.google.com with SMTP id c28so2656834ika.5 for ; Fri, 25 Jul 2008 05:03:41 -0700 (PDT) Content-Disposition: inline In-Reply-To: <20080725.045215.10253476.davem@davemloft.net> Sender: netdev-owner@vger.kernel.org List-ID: On Fri, Jul 25, 2008 at 04:52:15AM -0700, David Miller wrote: > From: Jarek Poplawski > Date: Fri, 25 Jul 2008 11:53:55 +0000 > > > On Fri, Jul 25, 2008 at 11:37:57AM +0000, Jarek Poplawski wrote: > > > > As a matter of fact it's a good example: in your patch we have this: > > > > + ret = cl->un.leaf.q->enqueue(skb, cl->un.leaf.q); > > + if (ret == NET_XMIT_DROP) { > > + sch->qstats.drops++; > > + cl->qstats.drops++; > > + } else { > > + cl->bstats.packets += > > + skb_is_gso(skb)?skb_shinfo(skb)->gso_segs:1; > > + cl->bstats.bytes += skb->len; > > > > So, if something works like noop_enqueue() and returns NET_XMIT_CN > > here, we're just using skb after kfree... > > noop_enqueue() can only be a root qdisc, never a leaf hanging off of a > class OK, sfq does the same. > What TCP depends upon is that DROP means DROP, and that the > packet never reached the device and has been freed. IMHO, TCP should depend on it's skb "refcount". A qdisc, after passing skb to other qdisc shouldn't depend on TCP's "refcount" because not everything has to work like TCP. Jarek P.