NVMe-oF: Fix generation of hostnqn file

In some old nvme-cli versions the NVMe-oF create_hostnqn method fails.

This happens specifically on versions between not having the
show-hostnqn command and having it always return a value. On those
version the command only returns the value present in the file and never
tries to return an idempotent or random value.

This patch adds for that specific case, which is identified by the
stderr message:

   hostnqn is not available -- use nvme gen-hostnqn

Closes-Bug: #2035606
Change-Id: Ic57d0fd85daf358e2b23326022fc471f034b0a2f

os_brick/privileged/nvmeof.py

@@ -50,11 +50,14 @@ def create_hostnqn() -> str:
         # This is different from OSError's ENOENT, which is missing nvme
         # command.  This ENOENT is when nvme says there isn't an nqn.
         except putils.ProcessExecutionError as e:
-            err_msg = e.stdout[:e.stdout.find('\n')]
-            show_hostnqn_subcmd_missing = (
-                "ERROR: Invalid sub-command".casefold() in err_msg.casefold())
-            if show_hostnqn_subcmd_missing:
+            # nvme-cli's error are all over the place, so merge the output
+            err_msg = e.stdout + '\n' + e.stderr
+            msg = err_msg.casefold()
+            if 'error: invalid sub-command' in msg:
                 LOG.debug('Version too old cannot check current hostnqn.')
+            elif 'hostnqn is not available' in msg:
+                LOG.debug('Version too old to return hostnqn from non file '
+                          'sources')
             elif e.exit_code == errno.ENOENT:
                 LOG.debug('No nqn could be formed from dmi or systemd.')
             else:

os_brick/tests/privileged/test_nvmeof.py

@@ -64,7 +64,8 @@ class PrivNVMeTestCase(base.TestCase):
         hostnqn = mock.Mock()
         mock_exec.side_effect = [
             putils.ProcessExecutionError(exit_code=errno.ENOENT,
-                                         stdout="totally exist sub-command"),
+                                         stdout="totally exist sub-command",
+                                         stderr=''),
             (hostnqn, mock.sentinel.err)
         ]
 
@@ -83,17 +84,23 @@ class PrivNVMeTestCase(base.TestCase):
         mock_chmod.assert_called_once_with('/etc/nvme/hostnqn', 0o644)
         self.assertEqual(stripped_hostnqn, res)
 
+    @ddt.data((231, 'error: Invalid sub-command\n', ''),
+              (254, '', 'hostnqn is not available -- use nvme gen-hostnqn\n'))
+    @ddt.unpack
     @mock.patch('os.chmod')
     @mock.patch.object(builtins, 'open', new_callable=mock.mock_open)
     @mock.patch('os.makedirs')
     @mock.patch.object(rootwrap, 'custom_execute')
-    def test_create_hostnqn_generate_old_nvme_cli(self, mock_exec, mock_mkdirs,
-                                                  mock_open, mock_chmod):
+    def test_create_hostnqn_generate_old_nvme_cli(
+            self, exit_code, stdout, stderr, mock_exec, mock_mkdirs, mock_open,
+            mock_chmod):
+
         hostnqn = mock.Mock()
         mock_exec.side_effect = [
             putils.ProcessExecutionError(
-                exit_code=231,
-                stdout="error: Invalid sub-command\n"),
+                exit_code=exit_code,
+                stdout=stdout,
+                stderr=stderr),
             (hostnqn, mock.sentinel.err)
         ]
 

releasenotes/notes/nvmeof-old-shownqn-c8cc2820b9c1418e.yaml

@@ -0,0 +1,6 @@
+---
+fixes:
+  - |
+    NVMe-oF connector `bug #2035606
+    <https://bugs.launchpad.net/os-brick/+bug/2035606>`_: Fixed generation of
+    hostnqn file on old nvme-cli versions.