From mboxrd@z Thu Jan 1 00:00:00 1970 From: "Samudrala, Sridhar" Subject: Re: [patch net-next 0/9] net: sched: introduce chain templates support with offloading to mlxsw Date: Wed, 27 Jun 2018 09:46:18 -0700 Message-ID: <0272f671-802b-30b6-6ca2-2ffc1e205664@intel.com> References: <20180625210148.9386-1-jiri@resnulli.us> <20180625215850.001276b8@cakuba.netronome.com> <20180626064355.GQ2161@nanopsycho> <20180626071217.GR2161@nanopsycho> <20180626141858.7f18730f@cakuba.netronome.com> <20180627075017.GA2007@nanopsycho> Mime-Version: 1.0 Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 8bit Cc: Linux Netdev List , David Miller , Jamal Hadi Salim , Cong Wang , Simon Horman , John Hurley , David Ahern , mlxsw@mellanox.com To: Jiri Pirko , Jakub Kicinski Return-path: Received: from mga18.intel.com ([134.134.136.126]:43320 "EHLO mga18.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932837AbeF0QqV (ORCPT ); Wed, 27 Jun 2018 12:46:21 -0400 In-Reply-To: <20180627075017.GA2007@nanopsycho> Content-Language: en-US Sender: netdev-owner@vger.kernel.org List-ID: On 6/27/2018 12:50 AM, Jiri Pirko wrote: > Tue, Jun 26, 2018 at 11:18:58PM CEST, jakub.kicinski@netronome.com wrote: >> On Tue, 26 Jun 2018 09:12:17 +0200, Jiri Pirko wrote: >>> Tue, Jun 26, 2018 at 09:00:45AM CEST, jakub.kicinski@netronome.com wrote: >>>> On Mon, Jun 25, 2018 at 11:43 PM, Jiri Pirko wrote: >>>>> Tue, Jun 26, 2018 at 06:58:50AM CEST, jakub.kicinski@netronome.com wrote: >>>>>> On Mon, 25 Jun 2018 23:01:39 +0200, Jiri Pirko wrote: >>>>>>> From: Jiri Pirko >>>>>>> >>>>>>> For the TC clsact offload these days, some of HW drivers need >>>>>>> to hold a magic ball. The reason is, with the first inserted rule inside >>>>>>> HW they need to guess what fields will be used for the matching. If >>>>>>> later on this guess proves to be wrong and user adds a filter with a >>>>>>> different field to match, there's a problem. Mlxsw resolves it now with >>>>>>> couple of patterns. Those try to cover as many match fields as possible. >>>>>>> This aproach is far from optimal, both performance-wise and scale-wise. >>>>>>> Also, there is a combination of filters that in certain order won't >>>>>>> succeed. >>>>>>> >>>>>>> Most of the time, when user inserts filters in chain, he knows right away >>>>>>> how the filters are going to look like - what type and option will they >>>>>>> have. For example, he knows that he will only insert filters of type >>>>>>> flower matching destination IP address. He can specify a template that >>>>>>> would cover all the filters in the chain. >>>>>> Perhaps it's lack of sleep, but this paragraph threw me a little off >>>>>> the track. IIUC the goal of this set is to provide a way to inform the >>>>>> HW about expected matches before any rule is programmed into the HW. >>>>>> Not before any rule is added to a particular chain. One can just use >>>>>> the first rule in the chain to make a guess about the chain, but thanks >>>>>> to this set user can configure *all* chains before any rules are added. >>>>> The template is per-chain. User can use template for chain x and >>>>> not-use it for chain y. Up to him. >>>> Makes sense. >>>> >>>> I can't help but wonder if it'd be better to associate the >>>> constraints/rules with chains instead of creating a new "template" >>>> object. It seems more natural to create a chain with specific >>>> constraints in place than add and delete template of which there can >>>> be at most one to a chain... Perhaps that's more about the user space >>>> tc command line. Anyway, not a strong objection, just a thought. >>> Hmm. I don't think it is good idea. User should see the template in a >>> "show" command per chain. We would have to have 2 show commands, one to >>> list the template objects and one to list templates per chains. It makes >>> things more complicated for no good reason. I think that this simple >>> chain-lock is easier and serves the purpose. >> Hm, I think the dump is fine, what I was thinking about was: >> >> # tc chain add dev dummy0 ingress chain_index 22 \ >> ^^^^^ >> template proto ip \ >> ^^^^^^^^ >> flower dst_mac 00:00:00:00:00:00/00:00:00:00:FF:FF > Okay, I got it. I see 2 issues. > 1) user might expect to add a chain without the template. But that does > not make sense really. Chains are created/deleted implicitly > according to refcount. > 2) there is not chain object like this available to user. Adding it just > for template looks odd. Also, the "filter" and "template" are very > much alike. They both are added to a chain, they both implicitly > create chain if it does not exist, etc. > > if you don't like "tc filter template add dev dummy0 ingress", how > about: > "tc template add dev dummy0 ingress ..." > "tc template add dev dummy0 ingress chain 22 ..." > that makes more sense I think. Isn't it possible to avoid introducing another keyword 'template', Can't we just do       tc chain add dev dummy0 ingress flower chain_index 0 to create a chain that takes any types of flower rules with index 0 and      tc chain add dev dummy0 ingress flower chain_index 22 dst_mac 00:00:00:00:00:00/00:00:00:00:FF:FF tc chain add dev dummy0 ingress flower chain_index 23 dst_ip 192.168.0.0/16 to create 2 chains 22 and 23 that allow rules with specific fields. To create a chain that takes decap rules like  filter protocol ip pref 2 flower chain 25 handle 0x2 dst_mac fe:24:9a:23:4c:5c src_mac ce:1d:58:eb:a0:35 eth_type ipv4 enc_dst_ip 192.168.100.20 enc_src_ip 192.168.100.22 enc_key_id 100 enc_dst_port 4789 can we create a chain using this format tc chain add dev dummy0 ingress flower chain_index 25 dst_mac 00:00:00:00:00:00/FF:FF:FF:FF:FF:FF src_mac 00:00:00:00:00:00/FF:FF:FF:FF:FF:FF enc_dst_ip 192.168.100.0/24 enc_src_ip 192.168.100.0/24 eth_type ipv4/arp enc_key_id 0/ffff enc_dst_port 0/ffff When adding a filter to a pre-defined chain, does the filter need to specify all the fields that are included in the chain's template? > > >> instead of: >> >> # tc filter template add dev dummy0 ingress \ >> ^^^^^^^^^^^^^^^ >> proto ip chain_index 22 \ >> flower dst_mac 00:00:00:00:00:00/00:00:00:00:FF:FF >> >> And then delete becomes: >> >> # tc chain del dev dummy0 ingress chain_index 22 >> Error: The chain is not empty. >> >> The fact that template is very much like a filter is sort of an >> implementation detail, from user perspective it may be more intuitive >> to model template as an attribute of the chain, not a filter object >> added to a chain. >> >> But I could well be the only person who feels that way :)