Re: [PATCH 1/3] qemu: Reflect MAC address change in live domain XML

On Wed, Jun 28, 2023 at 12:53:35PM +0200, Michal Privoznik wrote: > If a guest changes MAC address on its vNIC, then QEMU emits > NIC_RX_FILTER_CHANGED event (the event is emitted in other cases > too, but that's not important right now). Now, domain XML allows > users to chose whether to trust these events or not: > >  <interface trustGuestRxFilters='yes|no'/> > > For the 'no' case no action is performed and the event is > ignored. But for the 'yes' case, some host side features of > corresponding vNIC (well tap/macvtap device) are tweaked to > reflect changed MAC address. But what is missing is reflecting > this new MAC address in domain XML. > > Basically, what happens is: the host sees traffic with new MAC > address, all tools inside the guest see the new MAC address > (including 'virsh domifaddr --source agent') which makes it > harder to match device in the guest with the one in the domain > XML. > > NB, we should relay this event to clients, but that is covered in > next commits. > > Signed-off-by: Michal Privoznik <mprivozn(a)redhat.com&gt; > --- > src/qemu/qemu_domain.c | 18 ++++++++++++++++++ > src/qemu/qemu_driver.c |  2 +- > 2 files changed, 19 insertions(+), 1 deletion(-) > > diff --git a/src/qemu/qemu_domain.c b/src/qemu/qemu_domain.c > index 94587638c3..5e5789a28c 100644 > --- a/src/qemu/qemu_domain.c > +++ b/src/qemu/qemu_domain.c > @@ -12482,6 +12482,19 @@ syncNicRxFilterMulticast(char *ifname, > } > > > +/** > + * qemuDomainSyncRxFilter: > + * @vm: domain object > + * @def: domain interface definition > + * @asyncJob: async job type > + * > + * Fetch new state of RX Filter and set host side of the interface > + * accordingly (e.g. reflect MAC address change on macvtap). > + * > + * Reflect changed MAC address in the domain definition. > + * > + * Returns: 0 on success, -1 on error. > + */ > int > qemuDomainSyncRxFilter(virDomainObj *vm, >                        virDomainNetDef *def, > @@ -12535,6 +12548,11 @@ qemuDomainSyncRxFilter(virDomainObj *vm, >             return -1; >     } > > +    /* Reflect changed MAC address in the domain XML. */ > +    if (virMacAddrCmp(&def->mac, &guestFilter->mac)) { > +        virMacAddrSet(&def->mac, &guestFilter->mac); > +    } > + If we go with the idea I suggested this needs to be done even when we're not updating the filters.