virDomainNetFindIdx: Ignore auto generated MAC addresses

When detaching an <interface/> from a domain, the MAC address is
parsed and if not present one is generated. If no corresponding
interface is found in the domain, the following error is
reported:

error: operation failed: no device matching mac address 52:54:00:75:32:5b found

where the MAC address is the auto generated one. This might be
very confusing. Solution to this is to ignore auto generated MAC
address when looking up the device.
Signed-off-by: NMichal Privoznik <mprivozn@redhat.com>
Reviewed-by: NErik Skultety <eskultet@redhat.com>

src/conf/domain_conf.c

@@ -15649,11 +15649,17 @@ int virDomainNetInsert(virDomainDefPtr def, virDomainNetDefPtr net)
     return 0;
 }
 
-/* virDomainNetFindIdx: search according to mac address and guest side
- *                      PCI address (if specified)
+/**
+ * virDomainNetFindIdx:
+ * @def: domain definition
+ * @net: interface definition
  *
- * Return: index of match if unique match found
- *         -1 otherwise and an error is logged
+ * Lookup domain's network interface based on passed @net
+ * definition. If @net's MAC address was auto generated,
+ * the MAC comparison is ignored.
+ *
+ * Return: index of match if unique match found,
+ *         -1 otherwise and an error is logged.
  */
 int
 virDomainNetFindIdx(virDomainDefPtr def, virDomainNetDefPtr net)
@@ -15661,53 +15667,66 @@ virDomainNetFindIdx(virDomainDefPtr def, virDomainNetDefPtr net)
     size_t i;
     int matchidx = -1;
     char mac[VIR_MAC_STRING_BUFLEN];
+    bool MACAddrSpecified = !net->mac.generated;
     bool PCIAddrSpecified = virDomainDeviceAddressIsValid(&net->info,
                                                           VIR_DOMAIN_DEVICE_ADDRESS_TYPE_PCI);
 
     for (i = 0; i < def->nnets; i++) {
-        if (virMacAddrCmp(&def->nets[i]->mac, &net->mac))
+        if (MACAddrSpecified &&
+            virMacAddrCmp(&def->nets[i]->mac, &net->mac) != 0)
             continue;
 
-        if ((matchidx >= 0) && !PCIAddrSpecified) {
+        if (PCIAddrSpecified &&
+            !virPCIDeviceAddressEqual(&def->nets[i]->info.addr.pci,
+                                      &net->info.addr.pci))
+            continue;
+
+        if (matchidx >= 0) {
             /* there were multiple matches on mac address, and no
              * qualifying guest-side PCI address was given, so we must
              * fail (NB: a USB address isn't adequate, since it may
              * specify only vendor and product ID, and there may be
              * multiples of those.
              */
-            virReportError(VIR_ERR_OPERATION_FAILED,
-                           _("multiple devices matching mac address %s found"),
-                           virMacAddrFormat(&net->mac, mac));
-            return -1;
-        }
-        if (PCIAddrSpecified) {
-            if (virPCIDeviceAddressEqual(&def->nets[i]->info.addr.pci,
-                                         &net->info.addr.pci)) {
-                /* exit early if the pci address was specified and
-                 * it matches, as this guarantees no duplicates.
-                 */
-                matchidx = i;
-                break;
+            if (MACAddrSpecified) {
+                virReportError(VIR_ERR_OPERATION_FAILED,
+                               _("multiple devices matching MAC address %s found"),
+                               virMacAddrFormat(&net->mac, mac));
+            } else {
+                virReportError(VIR_ERR_OPERATION_FAILED, "%s",
+                               _("multiple matching devices found"));
             }
-        } else {
-            /* no PCI address given, so there may be multiple matches */
-            matchidx = i;
+
+            return -1;
         }
+
+        matchidx = i;
     }
+
     if (matchidx < 0) {
-        if (PCIAddrSpecified) {
+        if (MACAddrSpecified && PCIAddrSpecified) {
             virReportError(VIR_ERR_OPERATION_FAILED,
-                           _("no device matching mac address %s found on "
+                           _("no device matching MAC address %s found on "
                              "%.4x:%.2x:%.2x.%.1x"),
                            virMacAddrFormat(&net->mac, mac),
                            net->info.addr.pci.domain,
                            net->info.addr.pci.bus,
                            net->info.addr.pci.slot,
                            net->info.addr.pci.function);
-        } else {
+        } else if (PCIAddrSpecified) {
             virReportError(VIR_ERR_OPERATION_FAILED,
-                           _("no device matching mac address %s found"),
+                           _("no device found on %.4x:%.2x:%.2x.%.1x"),
+                           net->info.addr.pci.domain,
+                           net->info.addr.pci.bus,
+                           net->info.addr.pci.slot,
+                           net->info.addr.pci.function);
+        } else if (MACAddrSpecified) {
+            virReportError(VIR_ERR_OPERATION_FAILED,
+                           _("no device matching MAC address %s found"),
                            virMacAddrFormat(&net->mac, mac));
+        } else {
+            virReportError(VIR_ERR_OPERATION_FAILED, "%s",
+                           _("no matching device found"));
         }
     }
     return matchidx;