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

[Vincent Palatin <vpalatin@chromium.org>]

>> First of all, as you have 2 totally separated subnets in your setup, I
>> think your command-line should use "vlan=" parameter to isolate them,
>> else you will end up with some random routing/broadcasting (and random
>> tends to change over time).
>
> Does the kernel need some sort of vlan support compiled into it for this
> to work, or can the kernel not care?

You don't need anything in your kernel, this is for Qemu network layer
configuration.

>> I'm not using setup with multiple NICs but I would have written something like :
>> qemu -net nic,vlan=1,blah -net user,vlan=1 -net nic,vlan=2,blah -net
>> tun,vlan=2,blah
>>
>> In addition to this, which type of NIC are you using ?
>
> The actual command line is various permutations of:
>
> ~/qemu/qemu/x86_64-softmmu/qemu-system-x86_64 -m 512 -kernel
> ~/linux/linux/arch/x86/boot/bzImage -no-reboot -hda squeeze.ext3 -append
> "root=/dev/hda rw" -net nic,model=e1000,macaddr=52:54:00:11:11:11 -net
> user -redir tcp:9876::22 -net nic,model=e1000,macaddr=52:54:00:22:22:22
> -net tap,ifname=kvm0,script=no,downscript=no
>
> With the parameters reordered to try to beat some controllable behavior
> out of it.  (It had a deterministic behavior before the above commit,
> going back at least 2 years.  The behavior was changed by the commit.)
>
>> In my understanding, the Linux kernel might assign interface number
>> depending on the order the interfaces are appearing.
>
> It's going in PCI bus order.  And the _interfaces_ are still happily in
> PCI bus order both before and after this commit.  What's changing is the
> association between interface and -net user or -net tap.
>
> The first one, with macaddr 11:11:11, is always eth0.  But before the
> patch, eth0 is -net user, and after the patch eth0 is -net tap.

So, did you try the vlan parameter which is supposed to associate each
interface with the proper thing (IMO the command line order should not
have anything to do with it) ?

-- 
Vincent