network_config: added retries for lazy nics

In some setups, some NICs are seen by the OS later on during the first
early boot time, which requires retries so that the proper network
configuration is set.

The retry count and the timeout between retries is configurable using
the default configuration for retries:

```ini
[DEFAULT]
retry_count = 5
retry_count_interval = 4

```

Change-Id: I9bb46f4ece45a1988c9a7b9d08de5336e15eb85d

cloudbaseinit/plugins/common/networkconfig.py

@@ -13,10 +13,12 @@
 #    under the License.
 
 import re
+import time
 
 import netaddr
 from oslo_log import log as oslo_logging
 
+from cloudbaseinit import conf as cloudbaseinit_conf
 from cloudbaseinit import exception
 from cloudbaseinit.models import network as network_model
 from cloudbaseinit.osutils import factory as osutils_factory
@@ -24,6 +26,7 @@ from cloudbaseinit.plugins.common import base as plugin_base
 from cloudbaseinit.utils import network
 
 
+CONF = cloudbaseinit_conf.CONF
 LOG = oslo_logging.getLogger(__name__)
 
 # Mandatory network details are marked with True. And
@@ -124,49 +127,77 @@ def _preprocess_nics(network_details, network_adapters):
 class NetworkConfigPlugin(plugin_base.BasePlugin):
     def _process_network_details(self, network_details):
         osutils = osutils_factory.get_os_utils()
+
+        reboot_required = False
+        configured = False
+        macnics = {}
+
         # Check and save NICs by MAC.
         network_adapters = osutils.get_network_adapters()
         network_details = _preprocess_nics(network_details,
                                            network_adapters)
-        macnics = {}
+
         for nic in network_details:
             # Assuming that the MAC address is unique.
             macnics[nic.mac] = nic
 
         # Try configuring all the available adapters.
         adapter_macs = [pair[1] for pair in network_adapters]
-        reboot_required = False
-        configured = False
-        for mac in adapter_macs:
-            nic = macnics.pop(mac, None)
-            if not nic:
-                LOG.warn("Missing details for adapter %s", mac)
-                continue
 
-            name = osutils.get_network_adapter_name_by_mac_address(mac)
-            LOG.info("Configuring network adapter: %s", name)
+        network_details_nr = len(network_details)
+        LOG.debug("Found '%d' nics to configure", network_details_nr)
+        retry_count = 0
+        nics_configured = 0
+
+        while True:
+            LOG.debug("Trying to configure nics(%d-nth try)", retry_count + 1)
+            for mac in adapter_macs:
+                nic = macnics.pop(mac, None)
+                if not nic:
+                    LOG.warn("Missing details for adapter %s", mac)
+                    continue
+
+                name = osutils.get_network_adapter_name_by_mac_address(mac)
+                LOG.info("Configuring network adapter: %s", name)
+
+                # In v6 only case, nic.address and nic.netmask could be unset
+                if nic.address and nic.netmask:
+                    reboot = osutils.set_static_network_config(
+                        name,
+                        nic.address,
+                        nic.netmask,
+                        nic.gateway,
+                        nic.dnsnameservers or []
+                    )
+                reboot_required = reboot or reboot_required
+                # Set v6 info too if available.
+                if nic.address6 and nic.netmask6:
+                    reboot = osutils.set_static_network_config(
+                        name,
+                        nic.address6,
+                        nic.netmask6,
+                        nic.gateway6,
+                        []
+                    )
+                reboot_required = reboot or reboot_required
+                configured = True
+                nics_configured += 1
+
+            retry_count += 1
+
+            if (nics_configured >= network_details_nr
+                    or retry_count >= CONF.retry_count):
+                break
+
+            # try again to retrieve the network adapters
+            time.sleep(CONF.retry_count_interval)
+            network_adapters = osutils.get_network_adapters()
+            network_details = _preprocess_nics(network_details,
+                                               network_adapters)
+            for nic in network_details:
+                macnics[nic.mac] = nic
+            adapter_macs = [pair[1] for pair in network_adapters]
 
-            # In v6 only case, nic.address and nic.netmask could be unset
-            if nic.address and nic.netmask:
-                reboot = osutils.set_static_network_config(
-                    name,
-                    nic.address,
-                    nic.netmask,
-                    nic.gateway,
-                    nic.dnsnameservers or []
-                )
-            reboot_required = reboot or reboot_required
-            # Set v6 info too if available.
-            if nic.address6 and nic.netmask6:
-                reboot = osutils.set_static_network_config(
-                    name,
-                    nic.address6,
-                    nic.netmask6,
-                    nic.gateway6,
-                    []
-                )
-            reboot_required = reboot or reboot_required
-            configured = True
         for mac in macnics:
             LOG.warn("Details not used for adapter %s", mac)
         if not configured: