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

[Markus Armbruster]

Rob Landley <address@hidden> writes:

> On 05/12/2011 09:10 AM, Markus Armbruster wrote:
>> Rob Landley <address@hidden> 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.)

I didn't mean to tell you "try using -device to juggle PCI addresses".
I meant to steer you away from QEMU VLANs, to find out whether they're a
factor in your problem.  Possible, because non-VLAN uses a few different
code paths in QEMU.  Sorry if I was too terse.

In general, my advice is stay away from QEMU VLANs.

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

Glad you got your problem solved.