Hi,
When plug a bridge interface to an active VM with both LIVE AND CONFIG flags,
libvirt generate different mac address to LIVE and CONFIG instance, so After
I reboot the VM, DHCP server doesn't assign the same IP address to the new
bridge interface.
Steps:
1. Having running VM
## virsh list
Id Name State
-------------------------------
1 centos_7.6_64 running
2. Prepare a bridge interface xml
## cat interface.xml
<interface type='bridge'>
<source bridge='br0-int'/>
<virtualport type='openvswitch'>
</virtualport>
<model type='virtio'/>
<target dev='ovsvnet4'/>
</interface>
3. Plug interface with --live and --config
##virsh attach-device centos_7.6_64 interface.xml --config --live
Device attached successfully
4. Check LIVE XML
## cat /var/run/libvirt/qemu/centos_7.6_64.xml | grep ovsvnet4 -A 4 -B 6
<interface type='bridge'>
<mac address='52:54:00:23:7d:fb'/>
<source bridge='br0-int'/>
<virtualport type='openvswitch'>
<parameters interfaceid='c9f07f2b-3888-4f25-bd80-f5ba04d07bf8'/>
</virtualport>
<target dev='ovsvnet4'/>
<model type='virtio'/>
<alias name='net0'/>
<address type='pci' domain='0x0000' bus='0x02' slot='0x00' function='0x0'/>
</interface>
5. Check Config XML
## cat /etc/libvirt/qemu/centos_7.6_64.xml | grep ovsvnet4 -A 3 -B 6
<interface type='bridge'>
<mac address='52:54:00:bb:d4:53'/>
<source bridge='br0-int'/>
<virtualport type='openvswitch'>
<parameters interfaceid='189234ea-878e-4e8a-9f63-f43fac50aebd'/>
</virtualport>
<target dev='ovsvnet4'/>
<model type='virtio'/>
<address type='pci' domain='0x0000' bus='0x02' slot='0x00' function='0x0'/>
</interface>
The mac address and virtualport interfaceid does not match in LIVE and CONFIG XML.
This phenomenon was introduced by the commit:
commit 55ce65646348884656fd7bf3f109ebf8f7603494
Author: John Ferlan <jferlan@xxxxxxxxxx>
Date: Tue Jun 12 08:44:21 2018 -0400
qemu: Use the correct vm def on cold attach
https://bugzilla.redhat.com/show_bug.cgi?id=1559867
When attaching a device to the domain we need to be sure
to use the correct domain definition (vm->def or vm->newDef)
when calling virDomainDeviceDefParse because the post parse
processing algorithms that may assign an address for the
device will use whatever domain definition was passed in.
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