From afd6b2f5aed86da2cc4b2e4b41a69d1197600089 Mon Sep 17 00:00:00 2001
From: Rodolfo Alonso Hernandez <ralonsoh@redhat.com>
Date: Mon, 2 Dec 2019 11:48:28 +0000
Subject: [PATCH] Avoid raising NetworkInterfaceNotFound exception in DHCP
 agent logs

In "ip_lib.ensure_device_is_ready", before retrieving the interface
attributes, a check is done to know if the interface exists. In case
it does not exist, the exception "NetworkInterfaceNotFound" will not
be raised and written in the logs.

Conflicts:
    neutron/privileged/agent/linux/ip_lib.py

Change-Id: I4b9fd0885d850601717274a5058e042871211bbb
Closes-Bug: #1854723
(cherry picked from commit 8cc2765b5fdd229c9f6f19b83ad9e1ba030040ae)
---
 neutron/agent/linux/ip_lib.py                 |  8 +++++--
 neutron/privileged/agent/linux/ip_lib.py      | 24 ++++++++++++-------
 neutron/tests/unit/agent/linux/test_ip_lib.py | 14 +++++++----
 3 files changed, 31 insertions(+), 15 deletions(-)

diff --git a/neutron/agent/linux/ip_lib.py b/neutron/agent/linux/ip_lib.py
index 4f929c365f1..362ece1838e 100644
--- a/neutron/agent/linux/ip_lib.py
+++ b/neutron/agent/linux/ip_lib.py
@@ -509,6 +509,10 @@ class IpLinkCommand(IpDeviceCommandBase):
         return privileged.get_link_attributes(self.name,
                                               self._parent.namespace)
 
+    @property
+    def exists(self):
+        return privileged.interface_exists(self.name, self._parent.namespace)
+
 
 class IpAddrCommand(IpDeviceCommandBase):
     COMMAND = 'addr'
@@ -946,8 +950,8 @@ def ensure_device_is_ready(device_name, namespace=None):
     dev = IPDevice(device_name, namespace=namespace)
     try:
         # Ensure the device has a MAC address and is up, even if it is already
-        # up. If the device doesn't exist, a RuntimeError will be raised.
-        if not dev.link.address:
+        # up.
+        if not dev.link.exists or not dev.link.address:
             LOG.error("Device %s cannot be used as it has no MAC "
                       "address", device_name)
             return False
diff --git a/neutron/privileged/agent/linux/ip_lib.py b/neutron/privileged/agent/linux/ip_lib.py
index 3403bc08dc4..3bb04297e45 100644
--- a/neutron/privileged/agent/linux/ip_lib.py
+++ b/neutron/privileged/agent/linux/ip_lib.py
@@ -17,6 +17,7 @@ import socket
 
 from neutron_lib import constants
 from oslo_concurrency import lockutils
+from oslo_log import log as logging
 import pyroute2
 from pyroute2 import netlink
 from pyroute2.netlink import exceptions as netlink_exceptions
@@ -31,6 +32,8 @@ from neutron._i18n import _
 from neutron import privileged
 
 
+LOG = logging.getLogger(__name__)
+
 _IP_VERSION_FAMILY_MAP = {4: socket.AF_INET, 6: socket.AF_INET6}
 
 NETNS_RUN_DIR = '/var/run/netns'
@@ -240,12 +243,17 @@ def _translate_ip_device_exception(e, device=None, namespace=None):
                                              namespace=namespace)
 
 
-def get_link_id(device, namespace):
-    try:
-        with get_iproute(namespace) as ip:
-            return ip.link_lookup(ifname=device)[0]
-    except IndexError:
-        raise NetworkInterfaceNotFound(device=device, namespace=namespace)
+def get_link_id(device, namespace, raise_exception=True):
+    with get_iproute(namespace) as ip:
+        link_id = ip.link_lookup(ifname=device)
+    if not link_id or len(link_id) < 1:
+        if raise_exception:
+            raise NetworkInterfaceNotFound(device=device, namespace=namespace)
+        else:
+            LOG.debug('Interface %(dev)s not found in namespace %(namespace)s',
+                      {'dev': device, 'namespace': namespace})
+            return None
+    return link_id[0]
 
 
 def _run_iproute_link(command, device, namespace=None, **kwargs):
@@ -376,10 +384,8 @@ def delete_interface(ifname, namespace, **kwargs):
 @privileged.default.entrypoint
 def interface_exists(ifname, namespace):
     try:
-        idx = get_link_id(ifname, namespace)
+        idx = get_link_id(ifname, namespace, raise_exception=False)
         return bool(idx)
-    except NetworkInterfaceNotFound:
-        return False
     except OSError as e:
         if e.errno == errno.ENOENT:
             return False
diff --git a/neutron/tests/unit/agent/linux/test_ip_lib.py b/neutron/tests/unit/agent/linux/test_ip_lib.py
index 63b97962812..905f83f5a0f 100644
--- a/neutron/tests/unit/agent/linux/test_ip_lib.py
+++ b/neutron/tests/unit/agent/linux/test_ip_lib.py
@@ -936,15 +936,21 @@ class TestDeviceExists(base.BaseTestCase):
 
     def test_ensure_device_is_ready_no_link_address(self):
         with mock.patch.object(
-            priv_lib, 'get_link_attributes'
-        ) as get_link_attributes, mock.patch.object(
-            priv_lib, 'set_link_attribute'
-        ) as set_link_attribute:
+                priv_lib, 'get_link_attributes') as get_link_attributes, \
+                mock.patch.object(priv_lib, 'set_link_attribute') as \
+                set_link_attribute, \
+                mock.patch.object(priv_lib, 'interface_exists',
+                                  return_value=True):
             get_link_attributes.return_value = {}
             self.assertFalse(ip_lib.ensure_device_is_ready("lo"))
             get_link_attributes.assert_called_once_with("lo", None)
             set_link_attribute.assert_not_called()
 
+    def test_ensure_device_is_ready_no_device(self):
+        with mock.patch.object(priv_lib, 'interface_exists',
+                               return_value=False):
+            self.assertFalse(ip_lib.ensure_device_is_ready("lo"))
+
 
 class TestGetRoutingTable(base.BaseTestCase):
     ip_db_interfaces = {