qemu: homogenize MAC address in live & config when hotplugging a netdev
Prior to commit 55ce6564 (first in libvirt 4.6.0), the XML sent to virDomainAttachDeviceFlags() was parsed only once, and the results of that parse were inserted into both the live object of the running domain and into the persistent config. Thus, if MAC address was omitted from in XML for a network device (<interface>), both the live and config object would have the same MAC address. Commit 55ce6564 changed the code to parse the incoming XML twice - once for live and once for config. This does eliminate the problem of PCI (/scsi/sata) address conflicts caused by allocating an address based on existing devices in live object, but then inserting the result into the config (which may already have a device using that address), BUT it also means that when the MAC address of a network device hasn't been specified in the XML, each copy will get a different auto-generated MAC address. This results in the MAC address of the device changing the next time the domain is shutdown and restarted, which creates havoc with the guest OS's network config. There have been several discussions about this in the last > 1 year, attempting to find the ideal solution to this problem that makes MAC addresses consistent and accounts for all sorts of corner cases with PCI/scsi/sata addresses. All of these discussions fizzled out because every proposal was either too difficult to implement or failed to fix some esoteric case someone thought up. So, in the interest of solving the MAC address problem while not making the "other address" situation any worse than before, this patch simply adds a qemuDomainAttachDeviceLiveAndConfigHomogenize() function that (for now) copies the MAC address from the config object to the live object (if the original xml had <mac address='blah'/> then this will be an effective NOP (as the macs already match)). Any downstream libvirt containing upstream commit 55ce6564 should have this patch as well. https://bugzilla.redhat.com/1783411Signed-off-by: NLaine Stump <laine@redhat.com> Reviewed-by: NMichal Privoznik <mprivozn@redhat.com>
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