WIP test_host_evacuate: check for IP in xenstore first

This can show when after migration an IP address has been published to
Xenstore, but XAPI misses it nevertheless.

TODO: check impact on other code paths, notably VM migration.
Especially those code paths that do not update VM.host, which will
need the same kind of hack we had to do here.

lib/vm.py

@@ -71,6 +71,19 @@ def reboot(self, force=False, verify=False):
             self.wait_for_vm_running_and_ssh_up()
         return ret
 
+    def try_get_ip_xenstore(self):
+        domid = self.param_get("dom-id")
+        result = self.host.ssh(["xenstore", "read", f"/local/domain/{domid}/attr/vif/0/ipv4/0"],
+                               check=False, simple_output=False)
+
+        # An IP that starts with 169.254. is not a real routable IP.
+        # VMs may return such an IP before they get an actual one from DHCP.
+        if result.returncode != 0 or result.stdout.startswith('169.254.'):
+            return False
+        else:
+            logging.info("Xenstore VM IP: %s" % result.stdout)
+            return True
+
     def try_get_and_store_ip(self):
         ip = self.param_get('networks', '0/ip', accept_unknown_key=True)
 
@@ -123,6 +136,7 @@ def wait_for_os_booted(self):
         # waiting for the IP:
         # - allows to make sure the OS actually started (on VMs that have the management agent)
         # - allows to store the IP for future use in the VM object
+        wait_for(self.try_get_ip_xenstore, "Wait for Xenstore VM IP")
         wait_for(self.try_get_and_store_ip, "Wait for VM IP")
         # now wait also for the management agent to have started
         wait_for(self.is_management_agent_up, "Wait for management agent up")

tests/migration/test_host_evacuate.py

@@ -34,6 +34,7 @@ def _host_evacuate_test(source_host, dest_host, network_uuid, vm, expect_error=F
         source_host.xe('host-evacuate', args)
         wait_for(lambda: vm.all_vdis_on_host(dest_host), "Wait for all VDIs on destination host")
         wait_for(lambda: vm.is_running_on_host(dest_host), "Wait for VM to be running on destination host")
+        vm.host = dest_host
         vm.wait_for_os_booted()
         assert not expect_error, "host-evacuate should have raised: %s" % error
     except SSHCommandFailed as e: