Re: [Qemu-devel] -net interface association behavior change in current -git.

[Rob Landley <rob@landley.net>]

On 05/12/2011 09:10 AM, Markus Armbruster wrote:
> Rob Landley <rob@landley.net> writes:
> 
>> In 1.14.0, if I did this:
>>
>>   qemu -net nic,blah -net user -net nic,blah -net tun,blah
>>
>> Then the first nic would be -net user, and the second nic would be -net
>> tun.    In current -git, -net user attaches to the second interface and
>> -net tun attaches to the first, I.E. the order is reversed.
>>
>> Either way the first -nic becomes eth0 in Linux and the second becomes
>> eth1 (I can manually assign mac addresses in order to confirm which is
>> which), but eth0 used to be the -net user interface and now eth1 is the
>> -net user interface.
>>
>> I bisected this to commit 60c07d933c66c4b30a83b but I don't know why it
>> changed the behavior, and I can't find _documentation_ on having
>> multiple interfaces transports hooked up to the same qemu instance
>> anyway.  (It used to work, but possibly that was an accident?)
>>
>> Any ideas?
> 
> Does it happen with -device and -netdev as well?
> 
> See docs/qdev-device-use.txt for how to go from -net to -device.

Read read read...

That seems to be micromanaging PCI bus slot assignment, which isn't
changed by this patch.  The cards don't move around, nor does the
association between cards and Linux eth0/eth1.  What changes is which
virtual LAN each virtual ethernet card is plugged into.  (The virtual
cat5 cable coming out of the card moves to a different switch.)

(The fix was to tag everything with vlan arguments and manually manage
the association.)

Rob