qemu: qemuDomainChangeNet: validity checks should be done before XML autocompletion

This patch ensures that changes in attributes of interfaces will emit
errors except if they are missing from the XML.
Previously we were falsely reporting successful updates, because some
changed attributes got overwritten before the validity checks.

https://bugzilla.redhat.com/show_bug.cgi?id=1599513Signed-off-by: NKaterina Koukiou <kkoukiou@redhat.com>
Reviewed-by: NJán Tomko <jtomko@redhat.com>

src/qemu/qemu_hotplug.c

@@ -3598,16 +3598,19 @@ qemuDomainChangeNet(virQEMUDriverPtr driver,
         goto cleanup;
     }
 
-    /* info: if newdev->info is empty, fill it in from olddev,
-     * otherwise verify that it matches - nothing is allowed to
-     * change. (There is no helper function to do this, so
-     * individually check the few feidls of virDomainDeviceInfo that
-     * are relevant in this case).
+    /* info: Nothing is allowed to change. First fill the missing newdev->info
+     * from olddev and then check for changes.
      */
-    if (!virDomainDeviceAddressIsValid(&newdev->info,
-                                       VIR_DOMAIN_DEVICE_ADDRESS_TYPE_PCI) &&
-        virDomainDeviceInfoCopy(&newdev->info, &olddev->info) < 0) {
-        goto cleanup;
+    /* if pci addr is missing or is invalid we overwrite it from olddev */
+    if (newdev->info.type == VIR_DOMAIN_DEVICE_ADDRESS_TYPE_NONE ||
+        !virDomainDeviceAddressIsValid(&newdev->info,
+                                       newdev->info.type)) {
+        newdev->info.type = olddev->info.type;
+        newdev->info.addr = olddev->info.addr;
+    }
+    if (olddev->info.type != newdev->info.type) {
+        virReportError(VIR_ERR_OPERATION_UNSUPPORTED, "%s",
+                       _("cannot modify network device address type"));
     }
     if (!virPCIDeviceAddressEqual(&olddev->info.addr.pci,
                                   &newdev->info.addr.pci)) {
@@ -3622,21 +3625,33 @@ qemuDomainChangeNet(virQEMUDriverPtr driver,
 
     /* device alias is checked already in virDomainDefCompatibleDevice */
 
+    if (newdev->info.rombar == VIR_TRISTATE_BOOL_ABSENT)
+        newdev->info.rombar = olddev->info.rombar;
     if (olddev->info.rombar != newdev->info.rombar) {
         virReportError(VIR_ERR_OPERATION_UNSUPPORTED, "%s",
                        _("cannot modify network device rom bar setting"));
         goto cleanup;
     }
+
+    if (!newdev->info.romfile &&
+        VIR_STRDUP(newdev->info.romfile, olddev->info.romfile) < 0)
+        goto cleanup;
     if (STRNEQ_NULLABLE(olddev->info.romfile, newdev->info.romfile)) {
         virReportError(VIR_ERR_OPERATION_UNSUPPORTED, "%s",
                        _("cannot modify network rom file"));
         goto cleanup;
     }
+
+    if (newdev->info.bootIndex == 0)
+        newdev->info.bootIndex = olddev->info.bootIndex;
     if (olddev->info.bootIndex != newdev->info.bootIndex) {
         virReportError(VIR_ERR_OPERATION_UNSUPPORTED, "%s",
                        _("cannot modify network device boot index setting"));
         goto cleanup;
     }
+
+    if (newdev->info.romenabled == VIR_TRISTATE_BOOL_ABSENT)
+        newdev->info.romenabled = olddev->info.romenabled;
     if (olddev->info.romenabled != newdev->info.romenabled) {
         virReportError(VIR_ERR_OPERATION_UNSUPPORTED, "%s",
                        _("cannot modify network device rom enabled setting"));