From mboxrd@z Thu Jan 1 00:00:00 1970 From: Tobias Waldekranz Subject: Re: Deliver skbs to intermediate interfaces, when using cascaded rx-handlers Date: Mon, 24 Feb 2014 08:22:23 +0100 Message-ID: <20140224072223.GA20295@gmail.com> References: <20140221100158.GA19594@gmail.com> <20140221171034.GA2488@localhost.localdomain> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii To: netdev@vger.kernel.org Return-path: Received: from mail-la0-f52.google.com ([209.85.215.52]:34247 "EHLO mail-la0-f52.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751508AbaBXHWv (ORCPT ); Mon, 24 Feb 2014 02:22:51 -0500 Received: by mail-la0-f52.google.com with SMTP id c6so5188382lan.11 for ; Sun, 23 Feb 2014 23:22:50 -0800 (PST) Received: from gmail.com ([213.132.98.41]) by mx.google.com with ESMTPSA id jf8sm17625949lbc.8.2014.02.23.23.22.49 for (version=TLSv1.2 cipher=RC4-SHA bits=128/128); Sun, 23 Feb 2014 23:22:49 -0800 (PST) Content-Disposition: inline In-Reply-To: <20140221171034.GA2488@localhost.localdomain> Sender: netdev-owner@vger.kernel.org List-ID: On Fri, Feb 21, 2014 at 02:10:35PM -0300, Flavio Leitner wrote: > On Fri, Feb 21, 2014 at 11:01:58AM +0100, Tobias Waldekranz wrote: > > I have a system with the following configuration: > > > > * eth0 is a regular Ethernet MAC, connected to a hardware switch. > > * port[1-4] are the in-kernel representation of the switch. > > * team0 is a regular team-interface which bonds port1 and port2. > > > > +-------+ > > | team0 | > > +---+---+ > > | > > +----+----+ > > | | > > +---+---+ +---+---+ +-------+ +-------+ > > | port1 | | port2 | | port3 | | port4 | > > +---+---+ +---+---+ +---+---+ +---+---+ > > | | | | > > +---------+----+----+---------+ > > | > > +---+---+ > > | eth0 | > > +-------+ > > > > Both the switch and the team driver attaches rx-handlers to their > > lower layers. The problem is that team expects LACP frames that > > are intercepted by team0, to also be delivered to the port interface > > by __netif_receive_skb_core (in the final iteration of the registered > > protocols). However in this case, when two rx-handlers are cascaded, > > the skb will be delivered to eth0, since that is the original device > > (orig_dev). > > Indeed. It is not possible to update orig_dev, so it is stuck > on eth0 regardless of all the stacked interfaces. > > > There are a few ways this can be solved as far as i can see: > > > > 1. Introduce a new rx-handler return code that specifies that > > skb->dev has been altered, like RX_HANDLER_ANOTHER, and that we > > also want to change orig_dev to this new device. > > But then you need to know which rx-handler will run next, because > the orig_dev might still be implicit wanted. The next rx-handler is resolved by looking at skb->dev->rx_handler, so that shouldn't be a problem. Or am I missing something? > > > 2. Change the switch driver to return RX_HANDLER_CONSUMED and then > > queue the skb all over again, though I am afraid that this will eat > > some cycles. > > Before queue again, you need to update skb->dev, right? This seems > similar to (1). Exactly. It is very similar. The difference is that I would have to call netif_rx and go through a lot of code again, instead of taking the fast path via the another_round-loop in __netif_receive_skb_core. > > > 3. Keep track of all traversed interfaces and change the final > > protocol iteration to deliver the skb to all intermediate devices. > > That's what I thought too. Ok, so if I provide such a patch, you think it would have a good chance of getting accepted? What are the performance implications of deliver_skb-ing the packet to each intermediate layer? Considering that most of those packets will probably not be of interest to anyone. > > fbl -- Thanks - wkz