conf: Generate MAC address instead of keeping all zeroes

When we parse <mac address="00:00:00:00:00:00"/> we keep that in memory
and pass it down to the hypervisor. However, that MAC address is not
strictly valid as it is not marked as locally administered (bit 0x02)
but it is not even globally unique. It is also used for loopback device
on Linux, for example. And QEMU sees such MAC address just as "not
specified" and generates a new one that libvirt does not even know
about. So to make the overall experience better we now generate it if
the supplied one is all clear.

Resolves: https://issues.redhat.com/browse/RHEL-974

Signed-off-by: Martin Kletzander <mkletzan@redhat.com>
Reviewed-by: Michal Privoznik <mprivozn@redhat.com>

src/conf/domain_conf.c

@@ -9665,7 +9665,7 @@ virDomainNetDefParseXML(virDomainXMLOption *xmlopt,
             return NULL;
     }
 
-    if (!macaddr) {
+    if (!macaddr || virMacAddrIsAllClear(&def->mac)) {
         virDomainNetGenerateMAC(xmlopt, &def->mac);
         def->mac_generated = true;
     }

src/libvirt_private.syms

@@ -2743,6 +2743,7 @@ virMacAddrCompare;
 virMacAddrFormat;
 virMacAddrGenerate;
 virMacAddrGetRaw;
+virMacAddrIsAllClear;
 virMacAddrIsBroadcastRaw;
 virMacAddrIsMulticast;
 virMacAddrIsUnicast;

src/util/virmacaddr.c

@@ -246,6 +246,11 @@ virMacAddrIsBroadcastRaw(const unsigned char s[VIR_MAC_BUFLEN])
     return memcmp(virMacAddrBroadcastAddrRaw, s, sizeof(*s)) == 0;
 }
 
+bool virMacAddrIsAllClear(const virMacAddr *addr)
+{
+    return !virMacAddrCmpRaw(addr, (const unsigned char[VIR_MAC_BUFLEN]){0});
+}
+
 void
 virMacAddrFree(virMacAddr *addr)
 {

src/util/virmacaddr.h

@@ -58,6 +58,7 @@ int virMacAddrParseHex(const char* str,
 bool virMacAddrIsUnicast(const virMacAddr *addr);
 bool virMacAddrIsMulticast(const virMacAddr *addr);
 bool virMacAddrIsBroadcastRaw(const unsigned char s[VIR_MAC_BUFLEN]);
+bool virMacAddrIsAllClear(const virMacAddr *addr);
 void virMacAddrFree(virMacAddr *addr);
 
 G_DEFINE_AUTOPTR_CLEANUP_FUNC(virMacAddr, virMacAddrFree);

tests/genericxml2xmlindata/network-interface-mac-clear.xml

@@ -0,0 +1,21 @@
+<domain type='qemu'>
+  <name>QEMUGuest1</name>
+  <uuid>c7a5fdbd-edaf-9455-926a-d65c16db1809</uuid>
+  <memory unit='KiB'>219136</memory>
+  <currentMemory unit='KiB'>219136</currentMemory>
+  <vcpu placement='static'>1</vcpu>
+  <os>
+    <type arch='x86_64' machine='pc'>hvm</type>
+    <boot dev='hd'/>
+  </os>
+  <clock offset='utc'/>
+  <on_poweroff>destroy</on_poweroff>
+  <on_reboot>restart</on_reboot>
+  <on_crash>destroy</on_crash>
+  <devices>
+    <interface type='bridge'>
+      <mac address='00:00:00:00:00:00'/>
+      <source bridge='br0'/>
+    </interface>
+  </devices>
+</domain>

tests/genericxml2xmloutdata/network-interface-mac-clear.xml

@@ -0,0 +1,21 @@
+<domain type='qemu'>
+  <name>QEMUGuest1</name>
+  <uuid>c7a5fdbd-edaf-9455-926a-d65c16db1809</uuid>
+  <memory unit='KiB'>219136</memory>
+  <currentMemory unit='KiB'>219136</currentMemory>
+  <vcpu placement='static'>1</vcpu>
+  <os>
+    <type arch='x86_64' machine='pc'>hvm</type>
+    <boot dev='hd'/>
+  </os>
+  <clock offset='utc'/>
+  <on_poweroff>destroy</on_poweroff>
+  <on_reboot>restart</on_reboot>
+  <on_crash>destroy</on_crash>
+  <devices>
+    <interface type='bridge'>
+      <mac address='52:54:00:00:00:00'/>
+      <source bridge='br0'/>
+    </interface>
+  </devices>
+</domain>

tests/genericxml2xmltest.c

@@ -187,6 +187,7 @@ mymain(void)
     DO_TEST("cpu-cache-disable");
 
     DO_TEST("network-interface-mac-check");
+    DO_TEST_DIFFERENT("network-interface-mac-clear");
 
     DO_TEST_DIFFERENT("chardev-tcp");
     DO_TEST_FAIL_ACTIVE("chardev-tcp-missing-host");
@@ -257,4 +258,5 @@ mymain(void)
     return ret == 0 ? EXIT_SUCCESS : EXIT_FAILURE;
 }
 
-VIR_TEST_MAIN(mymain)
+VIR_TEST_MAIN_PRELOAD(mymain,
+                      VIR_TEST_MOCK("virrandom"))