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Re: [Qemu-devel] [QEMU] net: adapt dump to support the new syntax


From: Zhi Yong Wu
Subject: Re: [Qemu-devel] [QEMU] net: adapt dump to support the new syntax
Date: Fri, 17 Feb 2012 14:54:02 +0800

I would like to know if some one is playing around with the patchset.

If yes, can any one make one response? I am very interested in rebasing
it, and then playing with it.

On Tue, Jan 24, 2012 at 6:42 PM, Stefan Hajnoczi <address@hidden> wrote:
> On Tue, Jan 24, 2012 at 6:22 PM, Benjamin <address@hidden> wrote:
>> Hello Stefan,
>
> Hi,
> Please send QEMU development emails to the mailing list so others can
> help or we can avoid duplicating work in case someone else is already
> looking into this.  I have CCed the mailing list.
>
>> I've seen your blog and I hope you can help me address the issue of
>> -net dump not being compatible with the new -netdev syntax.
>
> The reason is because packet capture is implemented as a net client -
> it receives packets on the "VLAN" and writes them to the pcap file.
> In the -netdev model each client has a peer (another net client that
> is communicates with).  So it's not possible to plug the "dump" net
> client together with an emulated NIC client and a host tap client, for
> example.  Since "VLANs" broadcast packets to all attached net clients
> it works there.
>
>> I think it is possible to achieve but I've had a lot of trouble
>> understanding the code, VLANs are everywhere and even though the new
>> syntax doesn't use them it looks like the code still uses a VLAN logic.
>>
>> Before I really start to get serious about this task, do you have any
>> advice or recommendation?
>
> I refactored the network subsystem to drop the "VLAN" concept a while
> back but never got around to submitting the patches:
>
> http://repo.or.cz/w/qemu/stefanha.git/shortlog/refs/heads/vlan-hub
>
> This branch completely removes the "VLAN" feature.  Instead it
> introduces hubs, which are net clients that have multiple ports and
> broadcast packets between them.  This allows you to achieve the same
> behavior as "VLANs" except we remove all the hardcoded special cases
> in the net subsystem and instead push that feature out into the hub
> net client.
>
> If you rebase the vlan-hub branch onto a recent qemu.git, then you can
> use -netdev syntax to create an emulated NIC, host device, dump
> device, and a hub.  The three clients must be attached to the hub.
>
> I think the code is already there, it should work.  I didn't submit
> this because I wanted to implement automated tests to ensure that
> these changes don't brake the old syntax for "VLANs".
>
> Feel free to play around with the vlan-hub branch, test it, and push
> it upstream along with changes that you make.
>
> Stefan
>



-- 
Regards,

Zhi Yong Wu



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