On Wed, Jun 28, 2023 at 12:53:34PM +0200, Michal Privoznik wrote:
These are RFC patches. I'd like to start a discussion on the following problem:
We need to decide if we want to inform users in the live XML that the MAC changed (no matter the setting of trustGuestRxFilters), idea below. We could then add a flag to virDomainInterfaceAddresses() that switches to the other MAC address.
A mgmt application has info tied to an <interface/> (stored elsewhere, not important right now). And they use basically the only piece of information that's visible in both host and guest: MAC address. No, user aliases are not visible in the guest. Therefore, when they query the guest-agent (e.g. via 'virsh domifaddr --source agent') they can reconstruct their knowledge on NICs. But there's a catch - if user decides to change MAC address form inside of the VM. Then the only link between host and guest is broken. Now, we could make the guest-agent report both current and permanent MAC address. But unfortunately, libvirt's virDomainInterfaceAddresses() is not prepared for that. Now, I don't recall why we decided to not update MAC address in the live XML on change, but maybe somebody else does. Or we can pass the event from QEMU to the mgmt application so that it can update its state.
Could that be that referring to the interface would be troublesome? Can we add something like "current MAC address" in case it was changed?
Michal Prívozník (3): qemu: Reflect MAC address change in live domain XML Introduce NIC_MAC_CHANGE event qemu: Emit NIC_MAC_CHANGE event examples/c/misc/event-test.c | 14 +++++ include/libvirt/libvirt-domain.h | 28 +++++++++ src/conf/domain_event.c | 93 +++++++++++++++++++++++++++++ src/conf/domain_event.h | 12 ++++ src/libvirt_private.syms | 2 + src/qemu/qemu_domain.c | 34 ++++++++++- src/qemu/qemu_domain.h | 3 +- src/qemu/qemu_driver.c | 11 ++-- src/qemu/qemu_process.c | 2 +- src/remote/remote_daemon_dispatch.c | 32 ++++++++++ src/remote/remote_driver.c | 34 +++++++++++ src/remote/remote_protocol.x | 17 +++++- tools/virsh-domain-event.c | 20 +++++++ 13 files changed, 294 insertions(+), 8 deletions(-) -- 2.39.3
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