Re: [Qemu-devel] [PATCH 0/4] net-bridge: rootless bridge support for qemu

[Alexander Graf <agraf@suse.de>]

Anthony Liguori wrote:
> Alexander Graf wrote:
>> Yeah. Worse than the "run as root" part is the "it's hard" part
>> though. I hate how I feel when I try to explain someone how to use
>> non-slirp networking :-(.
>>
>> The response to that is then usually "oh whatever, it's too
>> complicated anyways".
>
> I agree and it's a problem I would like to solve too.
>
>>> And assuming a bridge is defined named qemubr0 and the administrator
>>> has setup
>>> permissions accordingly, it will Just Work.  My hope is that
>>> distributions will
>>> do this work as part of the qemu packaging process such that for
>>> most users,
>>> the out-of-the-box experience will also Just Work.
>>
>> Yeah, that won't work as easily.
>>
>> When your customer has 2 NICs this will already break. But let's
>> imagine we only have a single NIC.
>>
>> So that NIC is a wifi card. When I set up the qemubr0 bridge for that
>> one now, how does network manager configure my wifi access? It can't
>> use the bridge device, as that doesn't have wifi extensions. It also
>> can't use the wifi device, because setting up networking on that will
>> break.
>>
>> IMHO the only customer friendly choice I see is the ugly way. The way
>> VMware and Vbox do it.
>> To make it a bit less ugly, maybe we could create some way to "glue"
>> a tap device and an eth together, the same way the bridge code does,
>> just without the extra device.
>
> I don't think that helps either.  At the end of the day, this is
> really a policy decision.  You want to expose the subset of
> functionality that the majority of your users require.  Inevitably,
> you'll leave some users who need more complex setups on their own.
>
> For instance, users with one NIC are certainly common.  Two or more
> NICs are also pretty common.  But what about people that require
> guests to be on separate VLANs?
>
> This is where management tools come in.  When running qemu by hand,
> the management tool is the distro more or less as they will be
> choosing the default policies.  What we need to think about is how to
> make sure we can seamlessly integrate with whatever policies they want
> to implement.
>
> I think the one thing we could add is a configurable message to print
> when a user tries to use a bridge that isn't configured yet.  For
> instance, if a user runs qemu without a bridge setup, what would be
> nice is the following:
>
> $ qemu -net bridge -net nic -hda ~/images/linux.img
> qemu: error running bridge helper
>
> You currently do not have 'qemubr0' configured.  To setup qemubr0, run
> (as root):
>  zypper install qemu-network-setup
>  qemu-network-setup qemubr0
>
> $ sudo qemu-network-setup
> Which interface do you want to configure [qemubr0]: qemubr0
> Do you want to configure qemubr0 as NAT or Bridge [NAT]: Bridge
> Which physical interface do you want to bridge qemubr0 to [eth0]: eth0
> qemubr0 is now configured.
>
> I expect that this is going to be different for every distro.  netcf
> my make this easier but for now, I think this is the most realistic
> approach.

Well I'm not that familiar with the bridging stuff as I'm rather scared
by it myself, but last time I tried if I

# brctl addif br0 eth0
# ifconfig br0 up

eth0 stopped working, so I had to stop network manager, assign an IP to
br0 manually and hope network manager doesn't kick in again. I don't see
how we can solve that easily, as most people will want to use NM.

Alex