Gracefully ERROR in _init_instance if vnic_type changed

If the vnic_type of a bound port changes from "direct" to "macvtap" and
then the compute service is restarted then during _init_instance nova
tries to plug the vif of the changed port. However as it now has macvtap
vnic_type nova tries to look up the netdev of the parent VF. Still that
VF is consumed by the instance so there is no such netdev on the host
OS. This error killed the compute service at startup due to unhandled
exception. This patch adds the exception handler, logs an ERROR and
continue initializing other instances on the host.

Also this patch adds a detailed ERROR log when nova detects that the
vnic_type changed during _heal_instance_info_cache periodic.

Closes-Bug: #1981813
Change-Id: I1719f8eda04e8d15a3b01f0612977164c4e55e85

1 files changed, 34 insertions, 0 deletions

diff --git a/nova/network/neutron.py b/nova/network/neutron.py
index 5ca7649303..27e7d06455 100644
--- a/nova/network/neutron.py
+++ b/nova/network/neutron.py
@@ -3356,6 +3356,25 @@ class API:
             delegate_create=True,
         )
 
+    def _log_error_if_vnic_type_changed(
+        self, port_id, old_vnic_type, new_vnic_type, instance
+    ):
+        if old_vnic_type and old_vnic_type != new_vnic_type:
+            LOG.error(
+                'The vnic_type of the bound port %s has '
+                'been changed in neutron from "%s" to '
+                '"%s". Changing vnic_type of a bound port '
+                'is not supported by Nova. To avoid '
+                'breaking the connectivity of the instance '
+                'please change the port vnic_type back to '
+                '"%s".',
+                port_id,
+                old_vnic_type,
+                new_vnic_type,
+                old_vnic_type,
+                instance=instance
+            )
+
     def _build_network_info_model(self, context, instance, networks=None,
                                   port_ids=None, admin_client=None,
                                   preexisting_port_ids=None,
@@ -3429,6 +3448,12 @@ class API:
                         preexisting_port_ids)
                     for index, vif in enumerate(nw_info):
                         if vif['id'] == refresh_vif_id:
+                            self._log_error_if_vnic_type_changed(
+                                vif['id'],
+                                vif['vnic_type'],
+                                refreshed_vif['vnic_type'],
+                                instance,
+                            )
                             # Update the existing entry.
                             nw_info[index] = refreshed_vif
                             LOG.debug('Updated VIF entry in instance network '
@@ -3478,6 +3503,7 @@ class API:
             networks, port_ids = self._gather_port_ids_and_networks(
                     context, instance, networks, port_ids, client)
 
+        old_nw_info = instance.get_network_info()
         nw_info = network_model.NetworkInfo()
         for port_id in port_ids:
             current_neutron_port = current_neutron_port_map.get(port_id)
@@ -3485,6 +3511,14 @@ class API:
                 vif = self._build_vif_model(
                     context, client, current_neutron_port, networks,
                     preexisting_port_ids)
+                for old_vif in old_nw_info:
+                    if old_vif['id'] == port_id:
+                        self._log_error_if_vnic_type_changed(
+                            port_id,
+                            old_vif['vnic_type'],
+                            vif['vnic_type'],
+                            instance,
+                        )
                 nw_info.append(vif)
             elif nw_info_refresh:
                 LOG.info('Port %s from network info_cache is no '