From mboxrd@z Thu Jan 1 00:00:00 1970 From: Guenter Roeck Subject: Re: [PATCH net-next RFC v2] switchdev: bridge: drop hardware forwarded packets Date: Tue, 24 Mar 2015 20:10:50 -0700 Message-ID: <5512273A.2060303@roeck-us.net> References: <20150323002215.GA6074@roeck-us.net> <550F6D7D.7030403@gmail.com> <550F8102.7040701@roeck-us.net> <550F8600.2020300@gmail.com> <550F8987.5070600@roeck-us.net> <5510498D.5010001@cumulusnetworks.com> <20150324142921.GA2026@nanopsycho.orion> <20150324160126.GA17104@roeck-us.net> <5511A29F.5010006@cumulusnetworks.com> <20150324175825.GA1465@roeck-us.net> Mime-Version: 1.0 Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 7bit Cc: roopa , Jiri Pirko , John Fastabend , Andrew Lunn , David Miller , "Arad, Ronen" , Netdev To: Scott Feldman Return-path: Received: from bh-25.webhostbox.net ([208.91.199.152]:49524 "EHLO bh-25.webhostbox.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751990AbbCYDKx (ORCPT ); Tue, 24 Mar 2015 23:10:53 -0400 Received: from mailnull by bh-25.webhostbox.net with sa-checked (Exim 4.82) (envelope-from ) id 1YabiW-001nW7-Ng for netdev@vger.kernel.org; Wed, 25 Mar 2015 03:10:53 +0000 In-Reply-To: Sender: netdev-owner@vger.kernel.org List-ID: On 03/24/2015 11:14 AM, Scott Feldman wrote: > On Tue, Mar 24, 2015 at 10:58 AM, Guenter Roeck wrote: >> On Tue, Mar 24, 2015 at 10:45:03AM -0700, roopa wrote: >>> On 3/24/15, 9:01 AM, Guenter Roeck wrote: >>>> On Tue, Mar 24, 2015 at 03:29:21PM +0100, Jiri Pirko wrote: >>>>>> diff --git a/drivers/net/ethernet/rocker/rocker.c >>>>>> b/drivers/net/ethernet/rocker/rocker.c >>>>>> index aab962c..0f7217f7 100644 >>>>>> --- a/drivers/net/ethernet/rocker/rocker.c >>>>>> +++ b/drivers/net/ethernet/rocker/rocker.c >>>>>> @@ -3931,15 +3931,28 @@ unmap_frag: >>>>>> return -EMSGSIZE; >>>>>> } >>>>>> >>>>>> +static bool rocker_port_dev_check(struct net_device *dev); >>>>>> + >>>>>> static netdev_tx_t rocker_port_xmit(struct sk_buff *skb, struct >>>>>> net_device *dev) >>>>>> { >>>>>> struct rocker_port *rocker_port = netdev_priv(dev); >>>>>> struct rocker *rocker = rocker_port->rocker; >>>>>> struct rocker_desc_info *desc_info; >>>>>> struct rocker_tlv *frags; >>>>>> + struct net_device *in_dev; >>>>>> int i; >>>>>> int err; >>>>>> >>>>>> + if (rocker_port_is_bridged(rocker_port)) { >>>>>> + rcu_read_lock(); >>>>>> + in_dev = dev_get_by_index_rcu(dev_net(dev), skb->skb_iif); >>>>> Hmm, you iterate over all ports for every xmit call :/ >>>>> Would be nicer if skb_iif would be netdev poiter. Not sure it is doable. >>>>> >>>> It may be easier (and faster) to loop through all rocker ports and try to find >>>> one with the same ifindex. Then the dev_check call would not be necessary. >>>> >>> This is still overhead for every packet on the switches we support. The >>> number of ports can go close to 128 >>> (40G ports can be broken into 4x10G ports). >>> >> Agreed. Given that, and since dev_get_by_index_rcu uses a hash to find the >> device pointer, it may actually be (much) faster (and the above "iterate >> over all ports" is a bit misleading). >> >> I tested the above approach with DSA and a Marvell switch chip. It works, >> but I am a bit concerned about the per-packet overhead, especially >> in larger networks. I would prefer if there would be a means to 'catch' >> duplicate packets earlier - before they are even created, if that is >> possible. > > I'm not so concerned about the per-packet overhead. For multicast, we > have IGMP snooping. And big switches are going to have rate controls > on CPU bound traffic, so the CPU should be able to handle the > per-packet overhead with ease. > Ok, next question: Are there any legitimate reasons why a packet might be sent out on the same interface ? Examples might be packets received through a VPN or other tunnel and forwarded to the local network, or packets forwarded in L3 (for example if there are multiple L3 networks on the same link). Would skb_iif be set for such packets ? Guenter