From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:51271) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1ZJdLY-0006Lc-7k for qemu-devel@nongnu.org; Mon, 27 Jul 2015 04:01:17 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1ZJdLU-0002zq-IE for qemu-devel@nongnu.org; Mon, 27 Jul 2015 04:01:16 -0400 Received: from mx1.redhat.com ([209.132.183.28]:59893) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1ZJdLU-0002zX-Ay for qemu-devel@nongnu.org; Mon, 27 Jul 2015 04:01:12 -0400 Message-ID: <55B5E543.8050505@redhat.com> Date: Mon, 27 Jul 2015 16:01:07 +0800 From: Jason Wang MIME-Version: 1.0 References: <55AF75E6.6070909@cn.fujitsu.com> <1437562536-20414-1-git-send-email-yanghy@cn.fujitsu.com> <55B082BE.2020703@redhat.com> <55B5C14F.5030808@cn.fujitsu.com> <55B5D214.5030506@redhat.com> <55B5D727.8010806@cn.fujitsu.com> <55B5DE34.9050409@redhat.com> <55B5E1A4.9010100@cn.fujitsu.com> In-Reply-To: <55B5E1A4.9010100@cn.fujitsu.com> Content-Type: text/plain; charset=windows-1252 Content-Transfer-Encoding: 7bit Subject: Re: [Qemu-devel] [PATCH] RFC/net: Add a net filter List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Yang Hongyang , qemu-devel@nongnu.org Cc: thuth@redhat.com, stefanha@redhat.com On 07/27/2015 03:45 PM, Yang Hongyang wrote: > On 07/27/2015 03:31 PM, Jason Wang wrote: >> >> >> On 07/27/2015 03:00 PM, Yang Hongyang wrote: >>> >>> >>> On 07/27/2015 02:39 PM, Jason Wang wrote: >>>> >>>> >>>> On 07/27/2015 01:27 PM, Yang Hongyang wrote: >>>>> On 07/23/2015 01:59 PM, Jason Wang wrote: >>>>>> >>>>>> >>>>>> On 07/22/2015 06:55 PM, Yang Hongyang wrote: >>>>>>> This patch add a net filter between network backend and NIC >>>>>>> devices. >>>>>>> All packets will pass by this filter. >>>>>>> TODO: >>>>>>> multiqueue support. >>>>>>> plugin support. >>>>>>> >>>>>>> +--------------+ +-------------+ >>>>>>> +----------+ | filter | |frontend(NIC)| >>>>>>> | real | | | | | >>>>>>> | network <--+backend <-------+ | >>>>>>> | backend | | peer +-------> peer | >>>>>>> +----------+ +--------------+ +-------------+ >>>>>>> >>>>>>> Usage: >>>>>>> -netdev tap,id=bn0 # you can use whatever backend as needed >>>>>>> -netdev filter,id=f0,backend=bn0,plugin=dump >>>>>>> -device e1000,netdev=f0 >>>>>>> >>>>>>> Signed-off-by: Yang Hongyang >>>>>> >>>>>> Hi: >>>>>> >>>>>> Several questions: >>>>>> >>>>>> - Looks like we can do more than filter, so may be something like >>>>>> traffic control or other is more suitable? >>>>> >>>>> The filter is just a transparent proxy of a backend if no filter >>>>> plugin >>>>> is inserted. It just by pass all packets. Capture all traffic is the >>>>> purpose >>>>> of the filter. As long as we have an entry to capture all packets, we >>>>> can do more, this is what a filter plugin will do. There are some use >>>>> cases >>>>> I can think of: >>>>> - dump, by using filter, we can dump either output/input packets. >>>>> - buffer, to buffer/release packets, this feature can be used when >>>>> using >>>>> macrocheckpoing. Or other Remus like VM FT solutions. You >>>>> can >>>>> also supply an interval to a buffer plugin, which will >>>>> release >>>>> packets by interval. >>>> >>>> This sounds like traffic shaping. >>>> >>>>> May be other use cases based on this special backend. >>>>> >>>>>> - What's the advantages of introducing a new type of netdev? As far >>>>>> as I >>>>>> can see, just replace the dump function in Tomas' series with a >>>>>> configurable function pointer will do the trick? (Probably with some >>>>>> monitor commands). And then you won't even need to deal with vnet >>>>>> hder >>>>>> and offload stuffs? >>>>> >>>>> I think dump function focus on every netdev, it adds an >>>>> dump_enabled to >>>>> NetClientState, and dump the packet when the netdev receive been >>>>> called, >>>>> This filter function more focus on packets between backend/frontend, >>>>> it's kind of an injection to the network packets flow. >>>>> So the semantics are different I think. >>>> >>>> Yes, their functions are different. But the packet paths are similar, >>>> both require the packets go through themselves before reaching the >>>> peers. So simply passing the packets to the filter function before >>>> calling nc->info->receive{_raw}() in qemu_deliver_packet() will also >>>> work? >>> >>> I think this won't work for the buffer case? If we want the buffer case >>> to work under this, we should modify the generic netdev layer code, to >>> check the return value of the filter function call. >> >> But checking return value is rather simpler than a new netdev type, >> isn't it? > > But how to implement a plugin which suppose to do the actual work on > the packets? Well, the filter get the packets, so it can do everything it wants. > how to configure params related to the plugin? different > plugins may need different params, implement as another netdev? I belive qmp can do this? something like -filter dump,id=f0,len=10000? > >> >>> And it is not as >>> extensible as we abstract the filter function to a netdev, We can >>> flexibly add/remove/change filter plugins on the fly. >> >> I don't see why we lose the flexibility like what I suggested. Actually, >> implement it through a netdev will complex this. E.g: >> >> -netdev tap,id=bn0 # you can use whatever backend as needed >> -netdev filter,id=f0,backend=bn0,plugin=dump >> -device e1000,netdev=f0 >> >> How did you remove filter id=f0? Looks like you need also remove >> e1000 nic? > > No, when remove filter, we restore the connection between network > backend and > NIC. Just like filter does not ever exists. But e1000's peer is f0. You mean you will modify the peer pointer during filter removing? Sounds scary. > >> >> >> >> . >> >