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

[Stefan Hajnoczi]

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.

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