On Tue, Jun 18, 2013 at 10:05:58AM +0800, Fam Zheng wrote: > On Mon, 06/17 17:00, Michael S. Tsirkin wrote: > > On Mon, Jun 17, 2013 at 09:35:10PM +0800, Amos Kong wrote: > > > QEMU allocates macaddr to nic if user doesn't assigne macaddr. > > > But we didn't check if the allocated macaddr is used, it might > > > cause macaddr repeated. > > > > > > # qemu -device e1000,netdev=h1,mac=52:54:00:12:34:56 > > > (qemu) device_add e1000 > > > (qemu) info network > > > e1000.0: index=0,type=nic,model=e1000,macaddr=52:54:00:12:34:56 > > > \ h1: index=0,type=user,net=10.0.2.0,restrict=off > > > e1000.1: index=0,type=nic,model=e1000,macaddr=52:54:00:12:34:56 > > > > > > This patch adds a check in allocating macaddr, reallocate macaddr > > > if it's used by other nic. > > > > > > Signed-off-by: Amos Kong <[email protected]> > > > > I'm not sure this is not exactly what was intended in this case. > > Also this ptotects against an unlikely case of mixing > > implicit and explicit addresses, but not against > > a likely case of multiple qemu on same LAN using same MAC. > > IMHO, either way we can do little to protect against collision of > multiple qemu on the same LAN, but at least this patch protects against > repeated MAC address in one qemu instance. Better in some degree.
This is a policy, we should not dictate it. Maybe you want same MAC for some reason? > Leaving it to user, and asking for address explictly, absolutely helps, > but makes the interface a bit harder to use: there are still cases user > wants it generated automatically. A user that does not want to know what "MAC" even means is the only one I'm aware of. This is not such a case. > Just wondering if a random one could be better? If we are talking about a guest with multiple NICs, if you generate MACs randomly guest won't know which is which. It also breaks assumptions guests make that MAC is a static property of hardware. E.g. it can force windows re-activation, break resume from suspend etc > -- > Fam
