Re: [Qemu-devel] [PATCH v2] net/net: Change the default mac address of nic

[mike <qiudayu@linux.vnet.ibm.com>]

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On 10/18/2013 05:00 PM, Stefan Hajnoczi wrote:
> On Fri, Oct 18, 2013 at 10:54:13AM +0800, mike wrote:
>>> NACK
>>>
>>> I'm not going to merge this patch:
>>>
>>> If you terminate QEMU and launch it again the NIC gets a different MAC
>>> address.  Some guest operating systems are sensitive to this - under
>> For these users must use -device <nic-model>,mac=XX:XX:XX:XX:XX:XX.
>> I think no body will boot up the guest, which sensitive to this,
>> without mac address.
>>
>> Actually, people use the command line without mac address, mean they mainly
>> don't care about mac address, so give them random mac address is reasonable
>> I think.
>>
>> In my opinion, if we fix this, for qemu side no any issue, we both support
>> mac address set or unset correctly.
>>
>> What am I confuse is, *qemu supports mac address unset, why we force
>> users must set the address when more than one guests*?
>> This is unreasonable.
>>
>>> many Linux distros the network interfaces names change due to the MAC
>>> address change.  As a result firewall configuration will break and other
>>> services may fail to start because they cannot find the interface.
>> Agree, so this mac address should set in qemu command line as
>> libvirt does :)
>>> If you have multiple guests or want control over the MAC address, set it
>>> explicitly using -device <nic-model>,mac=XX:XX:XX:XX:XX:XX.
>> Currently, especially for developers, people mainly use qemu
>> command line directly, and as qemu supports mac address
>> unset, they may try the simplest command line to boot up
>> lots of guests, they will confuse about why all this guest use
>> the same mac address.
> Your argument is weak: *you* want to avoid specifying the MAC address so
> in exchange you want to *break* existing configurations and force other
> people to start specifying a MAC address.
OK, I do not want to break the existing configurations.

I'm fine if you do not want to merge this patch.

But I think this should be an issue of qemu, and need to
do something on it, so I make this patch.

Can we try other solutions to solve this issue?
(if you agree this should be an issue)

Also this potential issue can happens if the user set the same mac address
with more than one guest on one host.

Can we avoid this ?

Thanks
Mike
> This doesn't improve anything, it will just annoy users and cause bug
> reports.
>
> Sorry that there isn't a solution that satisfies everyone, you'll have
> to add a MAC address to your command-line.
>
> Stefan
>
>
>


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