Enable PXE for systems using petitboot

Petitboot systems do not use the pxelinux.0 loader. Instead,
petitboot itself handles pxelinux functionality. A side effect of
this is that petitboot requires DHCP option 210 (tftp path-prefix)
as this information is normally derived from the boot file name.
This patch uses the value of tftp_root as a path prefix and makes
the PXE module honor that prefix.

Change-Id: Ib9e954feea2cec38dd8328ada35005c0311c2a1b
Closes-Bug: #1639187
Co-Authored-By: Michael Turek <mjturek@linux.vnet.ibm.com>

ironic/common/pxe_utils.py

@@ -319,6 +319,12 @@ def dhcp_options_for_instance(task):
     else:
         dhcp_opts.append({'opt_name': 'bootfile-name',
                           'opt_value': boot_file})
+        # 210 == tftp server path-prefix or tftp root, will be used to find
+        # pxelinux.cfg directory. The pxelinux.0 loader infers this information
+        # from it's own path, but Petitboot needs it to be specified by this
+        # option since it doesn't use pxelinux.0 loader.
+        dhcp_opts.append({'opt_name': '210',
+                          'opt_value': get_tftp_path_prefix()})
 
     dhcp_opts.append({'opt_name': 'server-ip-address',
                       'opt_value': CONF.pxe.tftp_server})
@@ -330,3 +336,20 @@ def dhcp_options_for_instance(task):
         opt.update({'ip_version': int(CONF.pxe.ip_version)})
 
     return dhcp_opts
+
+
+def get_tftp_path_prefix():
+    """Adds trailing slash (if needed) necessary for path-prefix
+
+    :return: CONF.pxe.tftp_root ensured to have a trailing slash
+    """
+    return os.path.join(CONF.pxe.tftp_root, '')
+
+
+def get_path_relative_to_tftp_root(file_path):
+    """Return file relative path to CONF.pxe.tftp_root
+
+    :param file_path: full file path to be made relative path.
+    :returns: The path relative to CONF.pxe.tftp_root
+    """
+    return os.path.relpath(file_path, get_tftp_path_prefix())

ironic/drivers/modules/pxe.py

@@ -132,16 +132,21 @@ def _get_deploy_image_info(node):
 
 def _get_pxe_kernel_ramdisk(pxe_info):
     pxe_opts = {}
-    pxe_opts['deployment_aki_path'] = pxe_info['deploy_kernel'][1]
-    pxe_opts['deployment_ari_path'] = pxe_info['deploy_ramdisk'][1]
+    pxe_opts['deployment_aki_path'] = pxe_utils.get_path_relative_to_tftp_root(
+        pxe_info['deploy_kernel'][1])
+    pxe_opts['deployment_ari_path'] = pxe_utils.get_path_relative_to_tftp_root(
+        pxe_info['deploy_ramdisk'][1])
     # It is possible that we don't have kernel/ramdisk or even
     # image_source to determine if it's a whole disk image or not.
     # For example, when transitioning to 'available' state for first
     # time from 'manage' state.
     if 'kernel' in pxe_info:
-        pxe_opts['aki_path'] = pxe_info['kernel'][1]
+        pxe_opts['aki_path'] = pxe_utils.get_path_relative_to_tftp_root(
+            pxe_info['kernel'][1])
     if 'ramdisk' in pxe_info:
-        pxe_opts['ari_path'] = pxe_info['ramdisk'][1]
+        pxe_opts['ari_path'] = pxe_utils.get_path_relative_to_tftp_root(
+            pxe_info['ramdisk'][1])
+
     return pxe_opts
 
 

ironic/tests/unit/common/test_pxe_utils.py

@@ -424,9 +424,13 @@ class TestPXEUtils(db_base.DbTestCase):
         self.config(ip_version=ip_version, group='pxe')
         self.config(tftp_server='192.0.2.1', group='pxe')
         self.config(pxe_bootfile_name='fake-bootfile', group='pxe')
+        self.config(tftp_root='/tftp-path/', group='pxe')
         expected_info = [{'opt_name': 'bootfile-name',
                           'opt_value': 'fake-bootfile',
                           'ip_version': ip_version},
+                         {'opt_name': '210',
+                          'opt_value': '/tftp-path/',
+                          'ip_version': ip_version},
                          {'opt_name': 'server-ip-address',
                           'opt_value': '192.0.2.1',
                           'ip_version': ip_version},
@@ -603,3 +607,25 @@ class TestPXEUtils(db_base.DbTestCase):
                 '/httpboot/pxelinux.cfg/aa-aa-aa-aa-aa-aa')
             rmtree_mock.assert_called_once_with(
                 os.path.join(CONF.deploy.http_root, self.node.uuid))
+
+    def test_get_tftp_path_prefix_with_trailing_slash(self):
+        self.config(tftp_root='/tftpboot-path/', group='pxe')
+        path_prefix = pxe_utils.get_tftp_path_prefix()
+        self.assertEqual(path_prefix, '/tftpboot-path/')
+
+    def test_get_tftp_path_prefix_without_trailing_slash(self):
+        self.config(tftp_root='/tftpboot-path', group='pxe')
+        path_prefix = pxe_utils.get_tftp_path_prefix()
+        self.assertEqual(path_prefix, '/tftpboot-path/')
+
+    def test_get_path_relative_to_tftp_root_with_trailing_slash(self):
+        self.config(tftp_root='/tftpboot-path/', group='pxe')
+        test_file_path = '/tftpboot-path/pxelinux.cfg/test'
+        relpath = pxe_utils.get_path_relative_to_tftp_root(test_file_path)
+        self.assertEqual(relpath, 'pxelinux.cfg/test')
+
+    def test_get_path_relative_to_tftp_root_without_trailing_slash(self):
+        self.config(tftp_root='/tftpboot-path', group='pxe')
+        test_file_path = '/tftpboot-path/pxelinux.cfg/test'
+        relpath = pxe_utils.get_path_relative_to_tftp_root(test_file_path)
+        self.assertEqual(relpath, 'pxelinux.cfg/test')

ironic/tests/unit/drivers/modules/test_pxe.py

@@ -178,14 +178,10 @@ class PXEPrivateMethodsTestCase(db_base.DbTestCase):
 
         tftp_server = CONF.pxe.tftp_server
 
-        deploy_kernel = os.path.join(CONF.pxe.tftp_root, self.node.uuid,
-                                     'deploy_kernel')
-        deploy_ramdisk = os.path.join(CONF.pxe.tftp_root, self.node.uuid,
-                                      'deploy_ramdisk')
-        kernel = os.path.join(CONF.pxe.tftp_root, self.node.uuid,
-                              'kernel')
-        ramdisk = os.path.join(CONF.pxe.tftp_root, self.node.uuid,
-                               'ramdisk')
+        deploy_kernel = os.path.join(self.node.uuid, 'deploy_kernel')
+        deploy_ramdisk = os.path.join(self.node.uuid, 'deploy_ramdisk')
+        kernel = os.path.join(self.node.uuid, 'kernel')
+        ramdisk = os.path.join(self.node.uuid, 'ramdisk')
         root_dir = CONF.pxe.tftp_root
 
         image_info = {
@@ -251,11 +247,14 @@ class PXEPrivateMethodsTestCase(db_base.DbTestCase):
         self.node.save()
         self.config(group='pxe', tftp_server='my-tftp-server')
         self.config(group='pxe', pxe_append_params='my-pxe-append-params')
+        self.config(group='pxe', tftp_root='/tftp-path/')
         image_info = {
             'deploy_kernel': ('deploy_kernel',
-                              'path-to-deploy_kernel'),
+                              os.path.join(CONF.pxe.tftp_root,
+                                           'path-to-deploy_kernel')),
             'deploy_ramdisk': ('deploy_ramdisk',
-                               'path-to-deploy_ramdisk')}
+                               os.path.join(CONF.pxe.tftp_root,
+                                            'path-to-deploy_ramdisk'))}
 
         with task_manager.acquire(self.context, self.node.uuid,
                                   shared=True) as task:

releasenotes/notes/add-pxe-support-for-petitboot-50d1fe4e7da4bfba.yaml

@@ -0,0 +1,6 @@
+---
+features:
+  - Adds the use of DHCP option 210 (tftp-path-prefix). This
+    enables PXE for systems using petitboot, which cannot
+    infer their tftp-path-prefix from the boot file location
+    as petitboot does not use a boot file.