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Re: [Qemu-devel] [PATCH v3 00/16] net: hub-based networking
From: |
Markus Armbruster |
Subject: |
Re: [Qemu-devel] [PATCH v3 00/16] net: hub-based networking |
Date: |
Fri, 25 May 2012 13:18:35 +0200 |
User-agent: |
Gnus/5.13 (Gnus v5.13) Emacs/23.3 (gnu/linux) |
Stefan Hajnoczi <address@hidden> writes:
> On Thu, May 24, 2012 at 05:53:21PM -0300, Luiz Capitulino wrote:
>> On Fri, 25 May 2012 01:59:06 +0800
>> address@hidden wrote:
>>
>> > From: Zhi Yong Wu <address@hidden>
>> >
>> > The patchset implements network hub stead of vlan. The main work was done
>> > by stefan, and i rebased it to latest QEMU upstream, did some testings and
>> > am responsible for pushing it to QEMU upstream.
>>
>> Honest question: does it really pay off to have this in qemu vs. using one of
>> the externaly available solutions?
>
> For typical KVM setups this feature will be unused.
>
> However, the legacy QEMU "vlan" feature does have a few uses:
>
> 1. It's how the "dump" netdev can be connected up with a guest NIC and
> host netdev. Create a hub, attach the guest NIC, attach the host
> netdev, and attach the dump netdev. This allows the dump netdev to
> see all traffic.
>
> 2. It lets you build virtual network segments. Several point-to-point
> connections can be brought together. Start 3 VMs connected by the
> "socket" netdev and have one of them use a hub. This may be
> inefficient but I wouldn't be surprised if there are people out there
> doing this.
Those people will find other, superior ways to do this once this
inefficient way is gone. We'd do them a favour, I'd say ;)
> The point of this patch series is to remove the special-case net.c code
> for the legacy "vlan" feature. Today's code makes it harder to
> implement a clean QOM model and is a burden for the net subsystem in
> general. This series takes the vlan functionality and puts it into a
> normal netdev - it extracts the feature from net.c.
Welcome improvement, but...
> (If we didn't care about backwards compatibility we could just drop
> vlans completely and rewrite the "dump" netdev to hook into the net.h
> API somehow.)
... is backward compatiblity really worth the extra net client?
Please excuse my ignorant question (I haven't studied the series): what
kind of backward compatiblity exactly do we get here? Command line:
-net option vlan still works? Or just semantic: whatever you could do
with vlans you can now do with hubs?
In case it's the latter: well, whatever you could do with vlans you can
already do with external software, can't you? Why is it worthwhile to
provide yet another way within QEMU?
[Qemu-devel] [PATCH v3 12/16] net: Rename qemu_del_vlan_client() to qemu_del_net_client(), zwu . kernel, 2012/05/24
Re: [Qemu-devel] [PATCH v3 00/16] net: hub-based networking, Luiz Capitulino, 2012/05/24
- Re: [Qemu-devel] [PATCH v3 00/16] net: hub-based networking, Zhi Yong Wu, 2012/05/24
- Re: [Qemu-devel] [PATCH v3 00/16] net: hub-based networking, Stefan Hajnoczi, 2012/05/25
- Re: [Qemu-devel] [PATCH v3 00/16] net: hub-based networking,
Markus Armbruster <=
- Re: [Qemu-devel] [PATCH v3 00/16] net: hub-based networking, Stefan Hajnoczi, 2012/05/25
- Re: [Qemu-devel] [PATCH v3 00/16] net: hub-based networking, Markus Armbruster, 2012/05/25
- Re: [Qemu-devel] [PATCH v3 00/16] net: hub-based networking, Luiz Capitulino, 2012/05/25
- Re: [Qemu-devel] [PATCH v3 00/16] net: hub-based networking, Paolo Bonzini, 2012/05/25
- Re: [Qemu-devel] [PATCH v3 00/16] net: hub-based networking, Luiz Capitulino, 2012/05/25
- Re: [Qemu-devel] [PATCH v3 00/16] net: hub-based networking, Paolo Bonzini, 2012/05/25
- Re: [Qemu-devel] [PATCH v3 00/16] net: hub-based networking, Luiz Capitulino, 2012/05/25
- Re: [Qemu-devel] [PATCH v3 00/16] net: hub-based networking, Paolo Bonzini, 2012/05/25
- Re: [Qemu-devel] [PATCH v3 00/16] net: hub-based networking, Luiz Capitulino, 2012/05/25
- Re: [Qemu-devel] [PATCH v3 00/16] net: hub-based networking, Paolo Bonzini, 2012/05/25