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@xxxxxxxxxx>
---
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.
return 0;
}
diff --git a/src/qemu/qemu_driver.c b/src/qemu/qemu_driver.c
index f20544590d..ccf653d201 100644
--- a/src/qemu/qemu_driver.c
+++ b/src/qemu/qemu_driver.c
@@ -3712,7 +3712,7 @@ processNicRxFilterChangedEvent(virDomainObj *vm,
"from domain %p %s",
devAlias, vm, vm->def->name);
- if (virDomainObjBeginJob(vm, VIR_JOB_QUERY) < 0)
+ if (virDomainObjBeginJob(vm, VIR_JOB_MODIFY) < 0)
return;
if (!virDomainObjIsActive(vm)) {
--
2.39.3
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