[Qemu-devel] Re: [PATCH 0/8] vlan cleanup

[Markus Armbruster]

Miguel Di Ciurcio Filho <address@hidden> writes:

> On Tue, Jul 13, 2010 at 3:16 AM, Jan Kiszka <address@hidden> wrote:
>> Miguel Di Ciurcio Filho wrote:
>>> This series removes the vlan stuff without mercy. I've tried to make the 
>>> steps
>>> as small as possible, but the last one is huge. I did some basic tests and
>>> networking is still working, so reviews are welcome :-D
>>
>> Sorry, this is a bit too rude. This not only removes the vlan model,
>> something one may talk about, but also the innocent socket back-ends and
>> the useful pcap dump support.
>>
>> Socket back-ends allow quick and easy unprivileged inter-VM network
>> setups. Nothing for production systems, but useful for testing purposes
>> on boxes where taps are not allowed or unhandy to configure.
>>
>
> I agree that it might be handy sometimes, but one could use VDE for
> that too. Runs on user-space and can be tunneled over SSH or netcat
> [1].
> Another option would be to make the socket backend properly work as a
> netdev, so one could directly connect guest NICs on different hosts,
> but on a 1:1 relationship.
>
>> The dump client helps to debug user mode guest networks, namely slirp
>> which you did not remove. If that should become the only use case for
>> vlans with more than 2 nodes, we could think about making it a special
>> feature of backend devices.
>>
>
> socket and dump are only used when the vlan backends are concerned, so
> they don't have any useful meaning outside of that.
>
> How about add dump hooks on backends? I don't think network backends
> need to be stackable like block devices, thought.

Yes, add a dump hook in net.c for netdev in all the places where a dump
backend on a VLAN gets invoked.

>> I'm open for cleanups here, but they do require a bit mercy - and should
>> also mention the reason.
>>
>
> Well, basically there is a lot of "if (vlan) else if (peer)". While
> discussing the query-netdev QMP command, no one has shown any love
> about the vlan stuff at all, quite the contrary and it was kept out of
> the protocol.

Others are more knowledgable about that than I am, but here's my
understanding.  VLANs can't be accelerated.  1:1 connection (netdev) is
almost always just fine.  If you need a virtual LAN, there are better
tools to build it than QEMU.

> Regards,
>
> Miguel
>
> [1] http://wiki.virtualsquare.org/index.php/VDE#vde_plug