nameservers are obtained from nmcli

Before this patch, tobiko tried to obtain the list of nameservers
from a machine from its resolv.conf file.
With this patch, tobiko checks whether that machine has nmcli command
available and, if so, tries to obtain the DNS server with it too.

Change-Id: If83a8637dffa14dc712e605842e5d55713389dea

tobiko/shell/sh/__init__.py

@@ -24,6 +24,7 @@ from tobiko.shell.sh import _hostname
 from tobiko.shell.sh import _io
 from tobiko.shell.sh import _local
 from tobiko.shell.sh import _nameservers
+from tobiko.shell.sh import _nmcli
 from tobiko.shell.sh import _path
 from tobiko.shell.sh import _process
 from tobiko.shell.sh import _ps
@@ -135,3 +136,6 @@ get_file_size = _wc.get_file_size
 CommandNotFound = _which.CommandNotFound
 SkipOnCommandNotFound = _which.SkipOnCommandNotFound
 find_command = _which.find_command
+
+get_nm_connection_ids = _nmcli.get_nm_connection_ids
+get_nm_connection_values = _nmcli.get_nm_connection_values

tobiko/shell/sh/_nameservers.py

@@ -59,10 +59,23 @@ def list_nameservers(ssh_client: typing.Optional[ssh.SSHClientFixture] = None,
         filenames = ['/etc/resolv.conf']
 
     nameservers: tobiko.Selection[netaddr.IPAddress] = tobiko.Selection()
+    # obtain nameservers from the resolv.conf file
     for filename in filenames:
         nameservers.extend(parse_resolv_conf_file(ssh_client=ssh_client,
                                                   filename=filename,
                                                   **execute_params))
+
+    # obtain nameservers from nmcli, if available
+    try:
+        sh.find_command('nmcli', ssh_client=ssh_client)
+    except sh.CommandNotFound:
+        msg = 'nmcli command not available'
+        if ssh_client:
+            msg += f' on {ssh_client.host}'
+        LOG.debug(msg)
+    else:
+        nameservers.extend(parse_dns_nmcli(ssh_client=ssh_client))
+
     if ip_version:
         nameservers = nameservers.with_attributes(version=ip_version)
     return nameservers
@@ -71,8 +84,7 @@ def list_nameservers(ssh_client: typing.Optional[ssh.SSHClientFixture] = None,
 def parse_resolv_conf_file(
         filename: str,
         ssh_client: typing.Optional[ssh.SSHClientFixture] = None,
-        **execute_params) -> \
-        typing.Generator[netaddr.IPAddress, None, None]:
+        **execute_params) -> typing.Generator[netaddr.IPAddress, None, None]:
     lines: typing.List[str] = \
         sh.execute(f"cat '{filename}'",
                    ssh_client=ssh_client,
@@ -94,3 +106,18 @@ def parse_resolv_conf_file(
                     yield netaddr.IPAddress(nameserver)
                 except netaddr.AddrFormatError:
                     LOG.exception(f"Invalid nameserver address: {nameserver}")
+
+
+def parse_dns_nmcli(
+        ssh_client: typing.Optional[ssh.SSHClientFixture] = None) -> \
+        typing.Generator[netaddr.IPAddress, None, None]:
+    connections = sh.get_nm_connection_ids(ssh_client=ssh_client)
+    for connection in connections:
+        nameservers = sh.get_nm_connection_values(connection,
+                                                  'IP4.DNS,IP6.DNS',
+                                                  ssh_client=ssh_client)
+        for nameserver in nameservers:
+            try:
+                yield netaddr.IPAddress(nameserver)
+            except netaddr.AddrFormatError:
+                LOG.exception(f"Invalid nameserver address: {nameserver}")

tobiko/shell/sh/_nmcli.py

@@ -0,0 +1,45 @@
+# Copyright (c) 2025 Red Hat, Inc.
+#
+# All Rights Reserved.
+#
+#    Licensed under the Apache License, Version 2.0 (the "License"); you may
+#    not use this file except in compliance with the License. You may obtain
+#    a copy of the License at
+#
+#         http://www.apache.org/licenses/LICENSE-2.0
+#
+#    Unless required by applicable law or agreed to in writing, software
+#    distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
+#    WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
+#    License for the specific language governing permissions and limitations
+#    under the License.
+from __future__ import absolute_import
+
+from oslo_log import log
+
+from tobiko.shell.sh import _execute
+from tobiko.shell import ssh
+
+
+LOG = log.getLogger(__name__)
+
+
+def get_nm_connection_ids(ssh_client: ssh.SSHClientType = None) -> list:
+    result = _execute.execute('nmcli -g UUID con',
+                              ssh_client=ssh_client)
+    return result.stdout.splitlines()
+
+
+def get_nm_connection_values(connection: str,
+                             values: str,
+                             ssh_client: ssh.SSHClientType = None) -> list:
+    result = _execute.execute(f'nmcli -g {values} con show "{connection}"',
+                              ssh_client=ssh_client)
+    return_values = []
+    for line in result.stdout.splitlines():
+        if line:
+            for value in line.split('|'):
+                # nmcli adds escape char before ":" and we need to remove it
+                return_values.append(value.strip().replace('\\', ''))
+
+    return return_values

tobiko/tests/functional/openstack/stacks/test_advanced_vm.py

@@ -15,6 +15,8 @@
 #    under the License.
 from __future__ import absolute_import
 
+import typing
+
 import tobiko
 from tobiko.shell import sh
 from tobiko.openstack import stacks
@@ -27,7 +29,7 @@ class AdvancedServerStackTest(test_cirros.CirrosServerStackTest):
     #: Stack of resources with a server attached to a floating IP
     stack = tobiko.required_fixture(stacks.AdvancedServerStackFixture)
 
-    nameservers_filenames = ('/etc/resolv.conf',)
+    nameservers_filenames: typing.Optional[typing.Sequence[str]] = []
 
     def test_python(self):
         python_version = sh.execute(['python3', '--version'],