Adding upstream version 2.2.1.upstream/2.2.1

Signed-off-by: Benjamin Drung <bdrung@debian.org>

19 files changed, 4977 insertions, 0 deletions

diff --git a/staslib/.gitignore b/staslib/.gitignore
new file mode 100644
index 0000000..bee8a64
--- /dev/null
+++ b/staslib/.gitignore
@@ -0,0 +1 @@
+__pycache__
diff --git a/staslib/__init__.py b/staslib/__init__.py
new file mode 100644
index 0000000..27673d1
--- /dev/null
+++ b/staslib/__init__.py
@@ -0,0 +1,11 @@
+# Copyright (c) 2022, Dell Inc. or its subsidiaries.  All rights reserved.
+# SPDX-License-Identifier: Apache-2.0
+# See the LICENSE file for details.
+#
+# This file is part of NVMe STorage Appliance Services (nvme-stas).
+#
+# Authors: Martin Belanger <Martin.Belanger@dell.com>
+#
+'''STorage Appliance Services'''
+
+__version__ = '@VERSION@'
diff --git a/staslib/avahi.py b/staslib/avahi.py
new file mode 100644
index 0000000..c8a3a0b
--- /dev/null
+++ b/staslib/avahi.py
@@ -0,0 +1,456 @@
+# Copyright (c) 2021, Dell Inc. or its subsidiaries.  All rights reserved.
+# SPDX-License-Identifier: Apache-2.0
+# See the LICENSE file for details.
+#
+# This file is part of NVMe STorage Appliance Services (nvme-stas).
+#
+# Authors: Martin Belanger <Martin.Belanger@dell.com>
+#
+''' Module that provides a way to retrieve discovered
+    services from the Avahi daemon over D-Bus.
+'''
+import socket
+import typing
+import logging
+import functools
+import dasbus.error
+import dasbus.connection
+import dasbus.client.proxy
+import dasbus.client.observer
+from gi.repository import GLib
+from staslib import defs, conf, gutil
+
+
+def _txt2dict(txt: list):
+    '''@param txt: A list of list of integers. The integers are the ASCII value
+    of printable text characters.
+    '''
+    the_dict = dict()
+    for list_of_chars in txt:
+        try:
+            string = functools.reduce(lambda accumulator, c: accumulator + chr(c), list_of_chars, '')
+            key, val = string.split("=")
+            the_dict[key.lower()] = val
+        except Exception:  # pylint: disable=broad-except
+            pass
+
+    return the_dict
+
+
+def _proto2trans(protocol):
+    '''Return the matching transport for the given protocol.'''
+    if protocol is None:
+        return None
+
+    protocol = protocol.strip().lower()
+    if protocol == 'tcp':
+        return 'tcp'
+
+    if protocol in ('roce', 'iwarp', 'rdma'):
+        return 'rdma'
+
+    return None
+
+
+# ******************************************************************************
+class Avahi:  # pylint: disable=too-many-instance-attributes
+    '''@brief Avahi Server proxy. Set up the D-Bus connection to the Avahi
+    daemon and register to be notified when services of a certain
+    type (stype) are discovered or lost.
+    '''
+
+    DBUS_NAME = 'org.freedesktop.Avahi'
+    DBUS_INTERFACE_SERVICE_BROWSER = DBUS_NAME + '.ServiceBrowser'
+    DBUS_INTERFACE_SERVICE_RESOLVER = DBUS_NAME + '.ServiceResolver'
+    LOOKUP_USE_MULTICAST = 2
+
+    IF_UNSPEC = -1
+    PROTO_INET = 0
+    PROTO_INET6 = 1
+    PROTO_UNSPEC = -1
+
+    LOOKUP_RESULT_LOCAL = 8  # This record/service resides on and was announced by the local host
+    LOOKUP_RESULT_CACHED = 1  # This response originates from the cache
+    LOOKUP_RESULT_STATIC = 32  # The returned data has been defined statically by some configuration option
+    LOOKUP_RESULT_OUR_OWN = 16  # This service belongs to the same local client as the browser object
+    LOOKUP_RESULT_WIDE_AREA = 2  # This response originates from wide area DNS
+    LOOKUP_RESULT_MULTICAST = 4  # This response originates from multicast DNS
+
+    result_flags = {
+        LOOKUP_RESULT_LOCAL: 'local',
+        LOOKUP_RESULT_CACHED: 'cache',
+        LOOKUP_RESULT_STATIC: 'static',
+        LOOKUP_RESULT_OUR_OWN: 'own',
+        LOOKUP_RESULT_WIDE_AREA: 'wan',
+        LOOKUP_RESULT_MULTICAST: 'mcast',
+    }
+
+    protos = {PROTO_INET: 'IPv4', PROTO_INET6: 'IPv6', PROTO_UNSPEC: 'uspecified'}
+
+    @classmethod
+    def result_flags_as_string(cls, flags):
+        '''Convert flags to human-readable string'''
+        return '+'.join((value for flag, value in Avahi.result_flags.items() if (flags & flag) != 0))
+
+    @classmethod
+    def protocol_as_string(cls, proto):
+        '''Convert protocol codes to human-readable strings'''
+        return Avahi.protos.get(proto, 'unknown')
+
+    # ==========================================================================
+    def __init__(self, sysbus, change_cb):
+        self._change_cb = change_cb
+        self._services = dict()
+        self._sysbus = sysbus
+        self._stypes = set()
+        self._service_browsers = dict()
+
+        # Avahi is an on-demand service. If, for some reason, the avahi-daemon
+        # were to stop, we need to try to contact it for it to restart. For
+        # example, when installing the avahi-daemon package on a running system,
+        # the daemon doesn't get started right away. It needs another process to
+        # access it over D-Bus to wake it up. The following timer is used to
+        # periodically query the avahi-daemon until we successfully establish
+        # first contact.
+        self._kick_avahi_tmr = gutil.GTimer(60, self._on_kick_avahi)
+
+        # Subscribe for Avahi signals (i.e. events). This must be done before
+        # any Browser or Resolver is created to avoid race conditions and
+        # missed events.
+        self._subscriptions = [
+            self._sysbus.connection.signal_subscribe(
+                Avahi.DBUS_NAME,
+                Avahi.DBUS_INTERFACE_SERVICE_BROWSER,
+                'ItemNew',
+                None,
+                None,
+                0,
+                self._service_discovered,
+            ),
+            self._sysbus.connection.signal_subscribe(
+                Avahi.DBUS_NAME,
+                Avahi.DBUS_INTERFACE_SERVICE_BROWSER,
+                'ItemRemove',
+                None,
+                None,
+                0,
+                self._service_removed,
+            ),
+            self._sysbus.connection.signal_subscribe(
+                Avahi.DBUS_NAME, Avahi.DBUS_INTERFACE_SERVICE_BROWSER, 'Failure', None, None, 0, self._failure_handler
+            ),
+            self._sysbus.connection.signal_subscribe(
+                Avahi.DBUS_NAME, Avahi.DBUS_INTERFACE_SERVICE_RESOLVER, 'Found', None, None, 0, self._service_identified
+            ),
+            self._sysbus.connection.signal_subscribe(
+                Avahi.DBUS_NAME, Avahi.DBUS_INTERFACE_SERVICE_RESOLVER, 'Failure', None, None, 0, self._failure_handler
+            ),
+        ]
+
+        self._avahi = self._sysbus.get_proxy(Avahi.DBUS_NAME, '/')
+
+        self._avahi_watcher = dasbus.client.observer.DBusObserver(self._sysbus, Avahi.DBUS_NAME)
+        self._avahi_watcher.service_available.connect(self._avahi_available)
+        self._avahi_watcher.service_unavailable.connect(self._avahi_unavailable)
+        self._avahi_watcher.connect_once_available()
+
+    def kill(self):
+        '''@brief Clean up object'''
+        logging.debug('Avahi.kill()')
+
+        self._kick_avahi_tmr.kill()
+        self._kick_avahi_tmr = None
+
+        for subscription in self._subscriptions:
+            self._sysbus.connection.signal_unsubscribe(subscription)
+        self._subscriptions = list()
+
+        self._disconnect()
+
+        self._avahi_watcher.service_available.disconnect()
+        self._avahi_watcher.service_unavailable.disconnect()
+        self._avahi_watcher.disconnect()
+        self._avahi_watcher = None
+
+        dasbus.client.proxy.disconnect_proxy(self._avahi)
+        self._avahi = None
+
+        self._change_cb = None
+        self._sysbus = None
+
+    def info(self) -> dict:
+        '''@brief return debug info about this object'''
+        services = dict()
+        for service, obj in self._services.items():
+            interface, protocol, name, stype, domain = service
+            key = f'({socket.if_indextoname(interface)}, {Avahi.protos.get(protocol, "unknown")}, {name}.{domain}, {stype})'
+            services[key] = obj.get('data', {})
+
+        info = {
+            'avahi wake up timer': str(self._kick_avahi_tmr),
+            'service types': list(self._stypes),
+            'services': services,
+        }
+
+        return info
+
+    def get_controllers(self) -> list:
+        '''@brief Get the discovery controllers as a list of dict()
+        as follows:
+        [
+            {
+                'transport': tcp,
+                'traddr': str(),
+                'trsvcid': str(),
+                'host-iface': str(),
+                'subsysnqn': 'nqn.2014-08.org.nvmexpress.discovery',
+            },
+            {
+                'transport': tcp,
+                'traddr': str(),
+                'trsvcid': str(),
+                'host-iface': str(),
+                'subsysnqn': 'nqn.2014-08.org.nvmexpress.discovery',
+            },
+            [...]
+        ]
+        '''
+        return [service['data'] for service in self._services.values() if len(service['data'])]
+
+    def config_stypes(self, stypes: list):
+        '''@brief Configure the service types that we want to discover.
+        @param stypes: A list of services types, e.g. ['_nvme-disc._tcp']
+        '''
+        self._stypes = set(stypes)
+        success = self._configure_browsers()
+        if not success:
+            self._kick_avahi_tmr.start()
+
+    def kick_start(self):
+        '''@brief We use this to kick start the Avahi
+        daemon (i.e. socket activation).
+        '''
+        self._kick_avahi_tmr.clear()
+
+    def _disconnect(self):
+        logging.debug('Avahi._disconnect()')
+        for service in self._services.values():
+            resolver = service.pop('resolver', None)
+            if resolver is not None:
+                try:
+                    resolver.Free()
+                    dasbus.client.proxy.disconnect_proxy(resolver)
+                except (AttributeError, dasbus.error.DBusError) as ex:
+                    logging.debug('Avahi._disconnect()                - Failed to Free() resolver. %s', ex)
+
+        self._services = dict()
+
+        for browser in self._service_browsers.values():
+            try:
+                browser.Free()
+                dasbus.client.proxy.disconnect_proxy(browser)
+            except (AttributeError, dasbus.error.DBusError) as ex:
+                logging.debug('Avahi._disconnect()                - Failed to Free() browser. %s', ex)
+
+        self._service_browsers = dict()
+
+    def _on_kick_avahi(self):
+        try:
+            # try to contact avahi-daemon. This is just a wake
+            # up call in case the avahi-daemon was sleeping.
+            self._avahi.GetVersionString()
+        except dasbus.error.DBusError:
+            return GLib.SOURCE_CONTINUE
+
+        return GLib.SOURCE_REMOVE
+
+    def _avahi_available(self, _avahi_watcher):
+        '''@brief Hook up DBus signal handlers for signals from stafd.'''
+        logging.info('avahi-daemon service available, zeroconf supported.')
+        success = self._configure_browsers()
+        if not success:
+            self._kick_avahi_tmr.start()
+
+    def _avahi_unavailable(self, _avahi_watcher):
+        self._disconnect()
+        logging.warning('avahi-daemon not available, zeroconf not supported.')
+        self._kick_avahi_tmr.start()
+
+    def _configure_browsers(self):
+        stypes_cur = set(self._service_browsers.keys())
+        stypes_to_add = self._stypes - stypes_cur
+        stypes_to_rm = stypes_cur - self._stypes
+
+        logging.debug('Avahi._configure_browsers()        - stypes_to_rm  = %s', list(stypes_to_rm))
+        logging.debug('Avahi._configure_browsers()        - stypes_to_add = %s', list(stypes_to_add))
+
+        for stype_to_rm in stypes_to_rm:
+            browser = self._service_browsers.pop(stype_to_rm, None)
+            if browser is not None:
+                try:
+                    browser.Free()
+                    dasbus.client.proxy.disconnect_proxy(browser)
+                except (AttributeError, dasbus.error.DBusError) as ex:
+                    logging.debug('Avahi._configure_browsers()        - Failed to Free() browser. %s', ex)
+
+            # Find the cached services corresponding to stype_to_rm and remove them
+            services_to_rm = [service for service in self._services if service[3] == stype_to_rm]
+            for service in services_to_rm:
+                resolver = self._services.pop(service, {}).pop('resolver', None)
+                if resolver is not None:
+                    try:
+                        resolver.Free()
+                        dasbus.client.proxy.disconnect_proxy(resolver)
+                    except (AttributeError, dasbus.error.DBusError) as ex:
+                        logging.debug('Avahi._configure_browsers()        - Failed to Free() resolver. %s', ex)
+
+        for stype in stypes_to_add:
+            try:
+                obj_path = self._avahi.ServiceBrowserNew(
+                    Avahi.IF_UNSPEC, Avahi.PROTO_UNSPEC, stype, 'local', Avahi.LOOKUP_USE_MULTICAST
+                )
+                self._service_browsers[stype] = self._sysbus.get_proxy(Avahi.DBUS_NAME, obj_path)
+            except dasbus.error.DBusError as ex:
+                logging.debug('Avahi._configure_browsers()        - Failed to contact avahi-daemon. %s', ex)
+                logging.warning('avahi-daemon not available, operating w/o mDNS discovery.')
+                return False
+
+        return True
+
+    def _service_discovered(
+        self,
+        _connection,
+        _sender_name: str,
+        _object_path: str,
+        _interface_name: str,
+        _signal_name: str,
+        args: typing.Tuple[int, int, str, str, str, int],
+        *_user_data,
+    ):
+        (interface, protocol, name, stype, domain, flags) = args
+        logging.debug(
+            'Avahi._service_discovered()        - interface=%s (%s), protocol=%s, stype=%s, domain=%s, flags=%s %-14s name=%s',
+            interface,
+            socket.if_indextoname(interface),
+            Avahi.protocol_as_string(protocol),
+            stype,
+            domain,
+            flags,
+            '(' + Avahi.result_flags_as_string(flags) + '),',
+            name,
+        )
+
+        service = (interface, protocol, name, stype, domain)
+        if service not in self._services:
+            try:
+                obj_path = self._avahi.ServiceResolverNew(
+                    interface, protocol, name, stype, domain, Avahi.PROTO_UNSPEC, Avahi.LOOKUP_USE_MULTICAST
+                )
+                self._services[service] = {
+                    'resolver': self._sysbus.get_proxy(Avahi.DBUS_NAME, obj_path),
+                    'data': {},
+                }
+            except dasbus.error.DBusError as ex:
+                logging.warning('Failed to create resolver: "%s", "%s", "%s". %s', interface, name, stype, ex)
+
+    def _service_removed(
+        self,
+        _connection,
+        _sender_name: str,
+        _object_path: str,
+        _interface_name: str,
+        _signal_name: str,
+        args: typing.Tuple[int, int, str, str, str, int],
+        *_user_data,
+    ):
+        (interface, protocol, name, stype, domain, flags) = args
+        logging.debug(
+            'Avahi._service_removed()           - interface=%s (%s), protocol=%s, stype=%s, domain=%s, flags=%s %-14s name=%s',
+            interface,
+            socket.if_indextoname(interface),
+            Avahi.protocol_as_string(protocol),
+            stype,
+            domain,
+            flags,
+            '(' + Avahi.result_flags_as_string(flags) + '),',
+            name,
+        )
+
+        service = (interface, protocol, name, stype, domain)
+        resolver = self._services.pop(service, {}).pop('resolver', None)
+        if resolver is not None:
+            try:
+                resolver.Free()
+                dasbus.client.proxy.disconnect_proxy(resolver)
+            except (AttributeError, dasbus.error.DBusError) as ex:
+                logging.debug('Avahi._service_removed()           - Failed to Free() resolver. %s', ex)
+
+        self._change_cb()
+
+    def _service_identified(  # pylint: disable=too-many-locals
+        self,
+        _connection,
+        _sender_name: str,
+        _object_path: str,
+        _interface_name: str,
+        _signal_name: str,
+        args: typing.Tuple[int, int, str, str, str, str, int, str, int, list, int],
+        *_user_data,
+    ):
+        (interface, protocol, name, stype, domain, host, aprotocol, address, port, txt, flags) = args
+        txt = _txt2dict(txt)
+        logging.debug(
+            'Avahi._service_identified()        - interface=%s (%s), protocol=%s, stype=%s, domain=%s, flags=%s %-14s name=%s, host=%s, aprotocol=%s, address=%s, port=%s, txt=%s',
+            interface,
+            socket.if_indextoname(interface),
+            Avahi.protocol_as_string(protocol),
+            stype,
+            domain,
+            flags,
+            '(' + Avahi.result_flags_as_string(flags) + '),',
+            name,
+            host,
+            Avahi.protocol_as_string(aprotocol),
+            address,
+            port,
+            txt,
+        )
+
+        service = (interface, protocol, name, stype, domain)
+        if service in self._services:
+            transport = _proto2trans(txt.get('p'))
+            if transport is not None:
+                self._services[service]['data'] = {
+                    'transport': transport,
+                    'traddr': address.strip(),
+                    'trsvcid': str(port).strip(),
+                    # host-iface permitted for tcp alone and not rdma
+                    'host-iface': socket.if_indextoname(interface).strip() if transport == 'tcp' else '',
+                    'subsysnqn': txt.get('nqn', defs.WELL_KNOWN_DISC_NQN).strip()
+                    if conf.NvmeOptions().discovery_supp
+                    else defs.WELL_KNOWN_DISC_NQN,
+                }
+
+                self._change_cb()
+            else:
+                logging.error(
+                    'Received invalid/undefined protocol in mDNS TXT field: address=%s, iface=%s, TXT=%s',
+                    address,
+                    socket.if_indextoname(interface).strip(),
+                    txt,
+                )
+
+    def _failure_handler(  # pylint: disable=no-self-use
+        self,
+        _connection,
+        _sender_name: str,
+        _object_path: str,
+        interface_name: str,
+        _signal_name: str,
+        args: typing.Tuple[str],
+        *_user_data,
+    ):
+        (error,) = args
+        if 'ServiceResolver' not in interface_name or 'TimeoutError' not in error:
+            # ServiceResolver may fire a timeout event after being Free'd(). This seems to be normal.
+            logging.error('Avahi._failure_handler()    - name=%s, error=%s', interface_name, error)
diff --git a/staslib/conf.py b/staslib/conf.py
new file mode 100644
index 0000000..a54da98
--- /dev/null
+++ b/staslib/conf.py
@@ -0,0 +1,703 @@
+# Copyright (c) 2022, Dell Inc. or its subsidiaries.  All rights reserved.
+# SPDX-License-Identifier: Apache-2.0
+# See the LICENSE file for details.
+#
+# This file is part of NVMe STorage Appliance Services (nvme-stas).
+#
+# Authors: Martin Belanger <Martin.Belanger@dell.com>
+#
+'''nvme-stas configuration module'''
+
+import re
+import os
+import sys
+import logging
+import functools
+import configparser
+from staslib import defs, singleton, timeparse
+
+__TOKEN_RE = re.compile(r'\s*;\s*')
+__OPTION_RE = re.compile(r'\s*=\s*')
+
+
+class InvalidOption(Exception):
+    '''Exception raised when an invalid option value is detected'''
+
+
+def _parse_controller(controller):
+    '''@brief Parse a "controller" entry. Controller entries are strings
+           composed of several configuration parameters delimited by
+           semi-colons. Each configuration parameter is specified as a
+           "key=value" pair.
+    @return A dictionary of key-value pairs.
+    '''
+    options = dict()
+    tokens = __TOKEN_RE.split(controller)
+    for token in tokens:
+        if token:
+            try:
+                option, val = __OPTION_RE.split(token)
+                options[option.strip()] = val.strip()
+            except ValueError:
+                pass
+
+    return options
+
+
+def _parse_single_val(text):
+    if isinstance(text, str):
+        return text
+    if not isinstance(text, list) or len(text) == 0:
+        return None
+
+    return text[-1]
+
+
+def _parse_list(text):
+    return text if isinstance(text, list) else [text]
+
+
+def _to_int(text):
+    try:
+        return int(_parse_single_val(text))
+    except (ValueError, TypeError):
+        raise InvalidOption  # pylint: disable=raise-missing-from
+
+
+def _to_bool(text, positive='true'):
+    return _parse_single_val(text).lower() == positive
+
+
+def _to_ncc(text):
+    value = _to_int(text)
+    if value == 1:  # 1 is invalid. A minimum of 2 is required (with the exception of 0, which is valid).
+        value = 2
+    return value
+
+
+def _to_ip_family(text):
+    return tuple((4 if text == 'ipv4' else 6 for text in _parse_single_val(text).split('+')))
+
+
+# ******************************************************************************
+class OrderedMultisetDict(dict):
+    '''This class is used to change the behavior of configparser.ConfigParser
+    and allow multiple configuration parameters with the same key. The
+    result is a list of values.
+    '''
+
+    def __setitem__(self, key, value):
+        if key in self and isinstance(value, list):
+            self[key].extend(value)
+        else:
+            super().__setitem__(key, value)
+
+    def __getitem__(self, key):
+        value = super().__getitem__(key)
+
+        if isinstance(value, str):
+            return value.split('\n')
+
+        return value
+
+
+class SvcConf(metaclass=singleton.Singleton):  # pylint: disable=too-many-public-methods
+    '''Read and cache configuration file.'''
+
+    OPTION_CHECKER = {
+        'Global': {
+            'tron': {
+                'convert': _to_bool,
+                'default': False,
+                'txt-chk': lambda text: _parse_single_val(text).lower() in ('false', 'true'),
+            },
+            'kato': {
+                'convert': _to_int,
+            },
+            'pleo': {
+                'convert': functools.partial(_to_bool, positive='enabled'),
+                'default': True,
+                'txt-chk': lambda text: _parse_single_val(text).lower() in ('disabled', 'enabled'),
+            },
+            'ip-family': {
+                'convert': _to_ip_family,
+                'default': (4, 6),
+                'txt-chk': lambda text: _parse_single_val(text) in ('ipv4', 'ipv6', 'ipv4+ipv6', 'ipv6+ipv4'),
+            },
+            'queue-size': {
+                'convert': _to_int,
+                'rng-chk': lambda value: None if value in range(16, 1025) else range(16, 1025),
+            },
+            'hdr-digest': {
+                'convert': _to_bool,
+                'default': False,
+                'txt-chk': lambda text: _parse_single_val(text).lower() in ('false', 'true'),
+            },
+            'data-digest': {
+                'convert': _to_bool,
+                'default': False,
+                'txt-chk': lambda text: _parse_single_val(text).lower() in ('false', 'true'),
+            },
+            'ignore-iface': {
+                'convert': _to_bool,
+                'default': False,
+                'txt-chk': lambda text: _parse_single_val(text).lower() in ('false', 'true'),
+            },
+            'nr-io-queues': {
+                'convert': _to_int,
+            },
+            'ctrl-loss-tmo': {
+                'convert': _to_int,
+            },
+            'disable-sqflow': {
+                'convert': _to_bool,
+                'txt-chk': lambda text: _parse_single_val(text).lower() in ('false', 'true'),
+            },
+            'nr-poll-queues': {
+                'convert': _to_int,
+            },
+            'nr-write-queues': {
+                'convert': _to_int,
+            },
+            'reconnect-delay': {
+                'convert': _to_int,
+            },
+            ### BEGIN: LEGACY SECTION TO BE REMOVED ###
+            'persistent-connections': {
+                'convert': _to_bool,
+                'default': False,
+                'txt-chk': lambda text: _parse_single_val(text).lower() in ('false', 'true'),
+            },
+            ### END: LEGACY SECTION TO BE REMOVED ###
+        },
+        'Service Discovery': {
+            'zeroconf': {
+                'convert': functools.partial(_to_bool, positive='enabled'),
+                'default': True,
+                'txt-chk': lambda text: _parse_single_val(text).lower() in ('disabled', 'enabled'),
+            },
+        },
+        'Discovery controller connection management': {
+            'persistent-connections': {
+                'convert': _to_bool,
+                'default': True,
+                'txt-chk': lambda text: _parse_single_val(text).lower() in ('false', 'true'),
+            },
+            'zeroconf-connections-persistence': {
+                'convert': lambda text: timeparse.timeparse(_parse_single_val(text)),
+                'default': timeparse.timeparse('72hours'),
+            },
+        },
+        'I/O controller connection management': {
+            'disconnect-scope': {
+                'convert': _parse_single_val,
+                'default': 'only-stas-connections',
+                'txt-chk': lambda text: _parse_single_val(text)
+                in ('only-stas-connections', 'all-connections-matching-disconnect-trtypes', 'no-disconnect'),
+            },
+            'disconnect-trtypes': {
+                # Use set() to eliminate potential duplicates
+                'convert': lambda text: set(_parse_single_val(text).split('+')),
+                'default': [
+                    'tcp',
+                ],
+                'lst-chk': ('tcp', 'rdma', 'fc'),
+            },
+            'connect-attempts-on-ncc': {
+                'convert': _to_ncc,
+                'default': 0,
+            },
+        },
+        'Controllers': {
+            'controller': {
+                'convert': _parse_list,
+                'default': [],
+            },
+            'exclude': {
+                'convert': _parse_list,
+                'default': [],
+            },
+            ### BEGIN: LEGACY SECTION TO BE REMOVED ###
+            'blacklist': {
+                'convert': _parse_list,
+                'default': [],
+            },
+            ### END: LEGACY SECTION TO BE REMOVED ###
+        },
+    }
+
+    def __init__(self, default_conf=None, conf_file='/dev/null'):
+        self._config = None
+        self._defaults = default_conf if default_conf else {}
+
+        if self._defaults is not None and len(self._defaults) != 0:
+            self._valid_conf = {}
+            for section, option in self._defaults:
+                self._valid_conf.setdefault(section, set()).add(option)
+        else:
+            self._valid_conf = None
+
+        self._conf_file = conf_file
+        self.reload()
+
+    def reload(self):
+        '''@brief Reload the configuration file.'''
+        self._config = self._read_conf_file()
+
+    @property
+    def conf_file(self):
+        '''Return the configuration file name'''
+        return self._conf_file
+
+    def set_conf_file(self, fname):
+        '''Set the configuration file name and reload config'''
+        self._conf_file = fname
+        self.reload()
+
+    def get_option(self, section, option, ignore_default=False):  # pylint: disable=too-many-locals
+        '''Retrieve @option from @section, convert raw text to
+        appropriate object type, and validate.'''
+        try:
+            checker = self.OPTION_CHECKER[section][option]
+        except KeyError:
+            logging.error('Requesting invalid section=%s and/or option=%s', section, option)
+            raise
+
+        default = checker.get('default', None)
+
+        try:
+            text = self._config.get(section=section, option=option)
+        except (configparser.NoSectionError, configparser.NoOptionError, KeyError):
+            return None if ignore_default else self._defaults.get((section, option), default)
+
+        return self._check(text, section, option, default)
+
+    tron = property(functools.partial(get_option, section='Global', option='tron'))
+    kato = property(functools.partial(get_option, section='Global', option='kato'))
+    ip_family = property(functools.partial(get_option, section='Global', option='ip-family'))
+    queue_size = property(functools.partial(get_option, section='Global', option='queue-size'))
+    hdr_digest = property(functools.partial(get_option, section='Global', option='hdr-digest'))
+    data_digest = property(functools.partial(get_option, section='Global', option='data-digest'))
+    ignore_iface = property(functools.partial(get_option, section='Global', option='ignore-iface'))
+    pleo_enabled = property(functools.partial(get_option, section='Global', option='pleo'))
+    nr_io_queues = property(functools.partial(get_option, section='Global', option='nr-io-queues'))
+    ctrl_loss_tmo = property(functools.partial(get_option, section='Global', option='ctrl-loss-tmo'))
+    disable_sqflow = property(functools.partial(get_option, section='Global', option='disable-sqflow'))
+    nr_poll_queues = property(functools.partial(get_option, section='Global', option='nr-poll-queues'))
+    nr_write_queues = property(functools.partial(get_option, section='Global', option='nr-write-queues'))
+    reconnect_delay = property(functools.partial(get_option, section='Global', option='reconnect-delay'))
+
+    zeroconf_enabled = property(functools.partial(get_option, section='Service Discovery', option='zeroconf'))
+
+    zeroconf_persistence_sec = property(
+        functools.partial(
+            get_option, section='Discovery controller connection management', option='zeroconf-connections-persistence'
+        )
+    )
+
+    disconnect_scope = property(
+        functools.partial(get_option, section='I/O controller connection management', option='disconnect-scope')
+    )
+    disconnect_trtypes = property(
+        functools.partial(get_option, section='I/O controller connection management', option='disconnect-trtypes')
+    )
+    connect_attempts_on_ncc = property(
+        functools.partial(get_option, section='I/O controller connection management', option='connect-attempts-on-ncc')
+    )
+
+    @property
+    def stypes(self):
+        '''@brief Get the DNS-SD/mDNS service types.'''
+        return ['_nvme-disc._tcp', '_nvme-disc._udp'] if self.zeroconf_enabled else list()
+
+    @property
+    def persistent_connections(self):
+        '''@brief return the "persistent-connections" config parameter'''
+        section = 'Discovery controller connection management'
+        option = 'persistent-connections'
+
+        value = self.get_option(section, option, ignore_default=True)
+        legacy = self.get_option('Global', 'persistent-connections', ignore_default=True)
+
+        if value is None and legacy is None:
+            return self._defaults.get((section, option), True)
+
+        return value or legacy
+
+    def get_controllers(self):
+        '''@brief Return the list of controllers in the config file.
+        Each controller is in the form of a dictionary as follows.
+        Note that some of the keys are optional.
+        {
+            'transport':          [TRANSPORT],
+            'traddr':             [TRADDR],
+            'trsvcid':            [TRSVCID],
+            'host-traddr':        [TRADDR],
+            'host-iface':         [IFACE],
+            'subsysnqn':          [NQN],
+            'dhchap-ctrl-secret': [KEY],
+            'hdr-digest':         [BOOL]
+            'data-digest':        [BOOL]
+            'nr-io-queues':       [NUMBER]
+            'nr-write-queues':    [NUMBER]
+            'nr-poll-queues':     [NUMBER]
+            'queue-size':         [SIZE]
+            'kato':               [KATO]
+            'reconnect-delay':    [SECONDS]
+            'ctrl-loss-tmo':      [SECONDS]
+            'disable-sqflow':     [BOOL]
+        }
+        '''
+        controller_list = self.get_option('Controllers', 'controller')
+        cids = [_parse_controller(controller) for controller in controller_list]
+        for cid in cids:
+            try:
+                # replace 'nqn' key by 'subsysnqn', if present.
+                cid['subsysnqn'] = cid.pop('nqn')
+            except KeyError:
+                pass
+
+            # Verify values of the options used to overload the matching [Global] options
+            for option in cid:
+                if option in self.OPTION_CHECKER['Global']:
+                    value = self._check(cid[option], 'Global', option, None)
+                    if value is not None:
+                        cid[option] = value
+
+        return cids
+
+    def get_excluded(self):
+        '''@brief Return the list of excluded controllers in the config file.
+        Each excluded controller is in the form of a dictionary
+        as follows. All the keys are optional.
+        {
+            'transport':  [TRANSPORT],
+            'traddr':     [TRADDR],
+            'trsvcid':    [TRSVCID],
+            'host-iface': [IFACE],
+            'subsysnqn':  [NQN],
+        }
+        '''
+        controller_list = self.get_option('Controllers', 'exclude')
+
+        # 2022-09-20: Look for "blacklist". This is for backwards compatibility
+        # with releases 1.0 to 1.1.6. This is to be phased out (i.e. remove by 2024)
+        controller_list += self.get_option('Controllers', 'blacklist')
+
+        excluded = [_parse_controller(controller) for controller in controller_list]
+        for controller in excluded:
+            controller.pop('host-traddr', None)  # remove host-traddr
+            try:
+                # replace 'nqn' key by 'subsysnqn', if present.
+                controller['subsysnqn'] = controller.pop('nqn')
+            except KeyError:
+                pass
+        return excluded
+
+    def _check(self, text, section, option, default):
+        checker = self.OPTION_CHECKER[section][option]
+        text_checker = checker.get('txt-chk', None)
+        if text_checker is not None and not text_checker(text):
+            logging.warning(
+                'File:%s [%s]: %s - Text check found invalid value "%s". Default will be used',
+                self.conf_file,
+                section,
+                option,
+                text,
+            )
+            return self._defaults.get((section, option), default)
+
+        converter = checker.get('convert', None)
+        try:
+            value = converter(text)
+        except InvalidOption:
+            logging.warning(
+                'File:%s [%s]: %s - Data converter found invalid value "%s". Default will be used',
+                self.conf_file,
+                section,
+                option,
+                text,
+            )
+            return self._defaults.get((section, option), default)
+
+        value_in_range = checker.get('rng-chk', None)
+        if value_in_range is not None:
+            expected_range = value_in_range(value)
+            if expected_range is not None:
+                logging.warning(
+                    'File:%s [%s]: %s - "%s" is not within range %s..%s. Default will be used',
+                    self.conf_file,
+                    section,
+                    option,
+                    value,
+                    min(expected_range),
+                    max(expected_range),
+                )
+                return self._defaults.get((section, option), default)
+
+        list_checker = checker.get('lst-chk', None)
+        if list_checker:
+            values = set()
+            for item in value:
+                if item not in list_checker:
+                    logging.warning(
+                        'File:%s [%s]: %s - List checker found invalid item "%s" will be ignored.',
+                        self.conf_file,
+                        section,
+                        option,
+                        item,
+                    )
+                else:
+                    values.add(item)
+
+            if len(values) == 0:
+                return self._defaults.get((section, option), default)
+
+            value = list(values)
+
+        return value
+
+    def _read_conf_file(self):
+        '''@brief Read the configuration file if the file exists.'''
+        config = configparser.ConfigParser(
+            default_section=None,
+            allow_no_value=True,
+            delimiters=('='),
+            interpolation=None,
+            strict=False,
+            dict_type=OrderedMultisetDict,
+        )
+        if self._conf_file and os.path.isfile(self._conf_file):
+            config.read(self._conf_file)
+
+        # Parse Configuration and validate.
+        if self._valid_conf is not None:
+            invalid_sections = set()
+            for section in config.sections():
+                if section not in self._valid_conf:
+                    invalid_sections.add(section)
+                else:
+                    invalid_options = set()
+                    for option in config.options(section):
+                        if option not in self._valid_conf.get(section, []):
+                            invalid_options.add(option)
+
+                    if len(invalid_options) != 0:
+                        logging.error(
+                            'File:%s [%s] contains invalid options: %s',
+                            self.conf_file,
+                            section,
+                            invalid_options,
+                        )
+
+            if len(invalid_sections) != 0:
+                logging.error(
+                    'File:%s contains invalid sections: %s',
+                    self.conf_file,
+                    invalid_sections,
+                )
+
+        return config
+
+
+# ******************************************************************************
+class SysConf(metaclass=singleton.Singleton):
+    '''Read and cache the host configuration file.'''
+
+    def __init__(self, conf_file=defs.SYS_CONF_FILE):
+        self._config = None
+        self._conf_file = conf_file
+        self.reload()
+
+    def reload(self):
+        '''@brief Reload the configuration file.'''
+        self._config = self._read_conf_file()
+
+    @property
+    def conf_file(self):
+        '''Return the configuration file name'''
+        return self._conf_file
+
+    def set_conf_file(self, fname):
+        '''Set the configuration file name and reload config'''
+        self._conf_file = fname
+        self.reload()
+
+    def as_dict(self):
+        '''Return configuration as a dictionary'''
+        return {
+            'hostnqn': self.hostnqn,
+            'hostid': self.hostid,
+            'hostkey': self.hostkey,
+            'symname': self.hostsymname,
+        }
+
+    @property
+    def hostnqn(self):
+        '''@brief return the host NQN
+        @return: Host NQN
+        @raise: Host NQN is mandatory. The program will terminate if a
+                Host NQN cannot be determined.
+        '''
+        try:
+            value = self.__get_value('Host', 'nqn', defs.NVME_HOSTNQN)
+        except FileNotFoundError as ex:
+            sys.exit(f'Error reading mandatory Host NQN (see stasadm --help): {ex}')
+
+        if value is not None and not value.startswith('nqn.'):
+            sys.exit(f'Error Host NQN "{value}" should start with "nqn."')
+
+        return value
+
+    @property
+    def hostid(self):
+        '''@brief return the host ID
+        @return: Host ID
+        @raise: Host ID is mandatory. The program will terminate if a
+                Host ID cannot be determined.
+        '''
+        try:
+            value = self.__get_value('Host', 'id', defs.NVME_HOSTID)
+        except FileNotFoundError as ex:
+            sys.exit(f'Error reading mandatory Host ID (see stasadm --help): {ex}')
+
+        return value
+
+    @property
+    def hostkey(self):
+        '''@brief return the host key
+        @return: Host key
+        @raise: Host key is optional, but mandatory if authorization will be performed.
+        '''
+        try:
+            value = self.__get_value('Host', 'key', defs.NVME_HOSTKEY)
+        except FileNotFoundError as ex:
+            logging.info('Host key undefined: %s', ex)
+            value = None
+
+        return value
+
+    @property
+    def hostsymname(self):
+        '''@brief return the host symbolic name (or None)
+        @return: symbolic name or None
+        '''
+        try:
+            value = self.__get_value('Host', 'symname')
+        except FileNotFoundError as ex:
+            logging.warning('Error reading host symbolic name (will remain undefined): %s', ex)
+            value = None
+
+        return value
+
+    def _read_conf_file(self):
+        '''@brief Read the configuration file if the file exists.'''
+        config = configparser.ConfigParser(
+            default_section=None, allow_no_value=True, delimiters=('='), interpolation=None, strict=False
+        )
+        if os.path.isfile(self._conf_file):
+            config.read(self._conf_file)
+        return config
+
+    def __get_value(self, section, option, default_file=None):
+        '''@brief A configuration file consists of sections, each led by a
+               [section] header, followed by key/value entries separated
+               by a equal sign (=). This method retrieves the value
+               associated with the key @option from the section @section.
+               If the value starts with the string "file://", then the value
+               will be retrieved from that file.
+
+        @param section:      Configuration section
+        @param option:       The key to look for
+        @param default_file: A file that contains the default value
+
+        @return: On success, the value associated with the key. On failure,
+                 this method will return None is a default_file is not
+                 specified, or will raise an exception if a file is not
+                 found.
+
+        @raise: This method will raise the FileNotFoundError exception if
+                the value retrieved is a file that does not exist.
+        '''
+        try:
+            value = self._config.get(section=section, option=option)
+            if not value.startswith('file://'):
+                return value
+            file = value[7:]
+        except (configparser.NoSectionError, configparser.NoOptionError, KeyError):
+            if default_file is None:
+                return None
+            file = default_file
+
+        try:
+            with open(file) as f:  # pylint: disable=unspecified-encoding
+                return f.readline().split()[0]
+        except IndexError:
+            return None
+
+
+# ******************************************************************************
+class NvmeOptions(metaclass=singleton.Singleton):
+    '''Object used to read and cache contents of file /dev/nvme-fabrics.
+    Note that this file was not readable prior to Linux 5.16.
+    '''
+
+    def __init__(self):
+        # Supported options can be determined by looking at the kernel version
+        # or by reading '/dev/nvme-fabrics'. The ability to read the options
+        # from '/dev/nvme-fabrics' was only introduced in kernel 5.17, but may
+        # have been backported to older kernels. In any case, if the kernel
+        # version meets the minimum version for that option, then we don't
+        # even need to read '/dev/nvme-fabrics'.
+        self._supported_options = {
+            'discovery': defs.KERNEL_VERSION >= defs.KERNEL_TP8013_MIN_VERSION,
+            'host_iface': defs.KERNEL_VERSION >= defs.KERNEL_IFACE_MIN_VERSION,
+            'dhchap_secret': defs.KERNEL_VERSION >= defs.KERNEL_HOSTKEY_MIN_VERSION,
+            'dhchap_ctrl_secret': defs.KERNEL_VERSION >= defs.KERNEL_CTRLKEY_MIN_VERSION,
+        }
+
+        # If some of the options are False, we need to check wether they can be
+        # read from '/dev/nvme-fabrics'. This method allows us to determine that
+        # an older kernel actually supports a specific option because it was
+        # backported to that kernel.
+        if not all(self._supported_options.values()):  # At least one option is False.
+            try:
+                with open('/dev/nvme-fabrics') as f:  # pylint: disable=unspecified-encoding
+                    options = [option.split('=')[0].strip() for option in f.readline().rstrip('\n').split(',')]
+            except PermissionError:  # Must be root to read this file
+                raise
+            except (OSError, FileNotFoundError):
+                logging.warning('Cannot determine which NVMe options the kernel supports')
+            else:
+                for option, supported in self._supported_options.items():
+                    if not supported:
+                        self._supported_options[option] = option in options
+
+    def __str__(self):
+        return f'supported options: {self._supported_options}'
+
+    def get(self):
+        '''get the supported options as a dict'''
+        return self._supported_options
+
+    @property
+    def discovery_supp(self):
+        '''This option adds support for TP8013'''
+        return self._supported_options['discovery']
+
+    @property
+    def host_iface_supp(self):
+        '''This option allows forcing connections to go over
+        a specific interface regardless of the routing tables.
+        '''
+        return self._supported_options['host_iface']
+
+    @property
+    def dhchap_hostkey_supp(self):
+        '''This option allows specifying the host DHCHAP key used for authentication.'''
+        return self._supported_options['dhchap_secret']
+
+    @property
+    def dhchap_ctrlkey_supp(self):
+        '''This option allows specifying the controller DHCHAP key used for authentication.'''
+        return self._supported_options['dhchap_ctrl_secret']
diff --git a/staslib/ctrl.py b/staslib/ctrl.py
new file mode 100644
index 0000000..97a1c7b
--- /dev/null
+++ b/staslib/ctrl.py
@@ -0,0 +1,850 @@
+# Copyright (c) 2022, Dell Inc. or its subsidiaries.  All rights reserved.
+# SPDX-License-Identifier: Apache-2.0
+# See the LICENSE file for details.
+#
+# This file is part of NVMe STorage Appliance Services (nvme-stas).
+#
+# Authors: Martin Belanger <Martin.Belanger@dell.com>
+#
+'''This module defines the base Controller object from which the
+Dc (Discovery Controller) and Ioc (I/O Controller) objects are derived.'''
+
+import time
+import inspect
+import logging
+from gi.repository import GLib
+from libnvme import nvme
+from staslib import conf, defs, gutil, trid, udev, stas
+
+
+DLP_CHANGED = (
+    (nvme.NVME_LOG_LID_DISCOVER << 16) | (nvme.NVME_AER_NOTICE_DISC_CHANGED << 8) | nvme.NVME_AER_NOTICE
+)  # 0x70f002
+
+
+def get_eflags(dlpe):
+    '''@brief Return eflags field of dlpe'''
+    return int(dlpe.get('eflags', 0)) if dlpe else 0
+
+
+def get_ncc(eflags: int):
+    '''@brief Return True if Not Connected to CDC bit is asserted, False otherwise'''
+    return eflags & nvme.NVMF_DISC_EFLAGS_NCC != 0
+
+
+def dlp_supp_opts_as_string(dlp_supp_opts: int):
+    '''@brief Return the list of options supported by the Get
+    discovery log page command.
+    '''
+    data = {
+        nvme.NVMF_LOG_DISC_LID_EXTDLPES: "EXTDLPES",
+        nvme.NVMF_LOG_DISC_LID_PLEOS: "PLEOS",
+        nvme.NVMF_LOG_DISC_LID_ALLSUBES: "ALLSUBES",
+    }
+    return [txt for msk, txt in data.items() if dlp_supp_opts & msk]
+
+
+# ******************************************************************************
+class Controller(stas.ControllerABC):  # pylint: disable=too-many-instance-attributes
+    '''@brief Base class used to manage the connection to a controller.'''
+
+    def __init__(self, tid: trid.TID, service, discovery_ctrl: bool = False):
+        sysconf = conf.SysConf()
+        self._nvme_options = conf.NvmeOptions()
+        self._root = nvme.root()
+        self._host = nvme.host(
+            self._root, hostnqn=sysconf.hostnqn, hostid=sysconf.hostid, hostsymname=sysconf.hostsymname
+        )
+        self._host.dhchap_key = sysconf.hostkey if self._nvme_options.dhchap_hostkey_supp else None
+        self._udev = udev.UDEV
+        self._device = None  # Refers to the nvme device (e.g. /dev/nvme[n])
+        self._ctrl = None  # libnvme's nvme.ctrl object
+        self._connect_op = None
+
+        super().__init__(tid, service, discovery_ctrl)
+
+    def _release_resources(self):
+        logging.debug('Controller._release_resources()    - %s | %s', self.id, self.device)
+
+        if self._udev:
+            self._udev.unregister_for_device_events(self._on_udev_notification)
+
+        self._kill_ops()
+
+        super()._release_resources()
+
+        self._ctrl = None
+        self._udev = None
+        self._host = None
+        self._root = None
+        self._nvme_options = None
+
+    @property
+    def device(self) -> str:
+        '''@brief return the Linux nvme device id (e.g. nvme3) or empty
+        string if no device is associated with this controller'''
+        if not self._device and self._ctrl and self._ctrl.name:
+            self._device = self._ctrl.name
+
+        return self._device or 'nvme?'
+
+    def all_ops_completed(self) -> bool:
+        '''@brief Returns True if all operations have completed. False otherwise.'''
+        return self._connect_op is None or self._connect_op.completed()
+
+    def connected(self):
+        '''@brief Return whether a connection is established'''
+        return self._ctrl and self._ctrl.connected()
+
+    def controller_id_dict(self) -> dict:
+        '''@brief return the controller ID as a dict.'''
+        cid = super().controller_id_dict()
+        cid['device'] = self.device
+        return cid
+
+    def details(self) -> dict:
+        '''@brief return detailed debug info about this controller'''
+        details = super().details()
+        details.update(
+            self._udev.get_attributes(self.device, ('hostid', 'hostnqn', 'model', 'serial', 'dctype', 'cntrltype'))
+        )
+        details['connected'] = str(self.connected())
+        return details
+
+    def info(self) -> dict:
+        '''@brief Get the controller info for this object'''
+        info = super().info()
+        if self._connect_op:
+            info['connect operation'] = str(self._connect_op.as_dict())
+        return info
+
+    def cancel(self):
+        '''@brief Used to cancel pending operations.'''
+        super().cancel()
+        if self._connect_op:
+            self._connect_op.cancel()
+
+    def _kill_ops(self):
+        if self._connect_op:
+            self._connect_op.kill()
+            self._connect_op = None
+
+    def set_level_from_tron(self, tron):
+        '''Set log level based on TRON'''
+        if self._root:
+            self._root.log_level("debug" if tron else "err")
+
+    def _on_udev_notification(self, udev_obj):
+        if self._alive():
+            if udev_obj.action == 'change':
+                nvme_aen = udev_obj.get('NVME_AEN')
+                nvme_event = udev_obj.get('NVME_EVENT')
+                if isinstance(nvme_aen, str):
+                    logging.info('%s | %s - Received AEN: %s', self.id, udev_obj.sys_name, nvme_aen)
+                    self._on_aen(int(nvme_aen, 16))
+                if isinstance(nvme_event, str):
+                    self._on_nvme_event(nvme_event)
+            elif udev_obj.action == 'remove':
+                logging.info('%s | %s - Received "remove" event', self.id, udev_obj.sys_name)
+                self._on_ctrl_removed(udev_obj)
+            else:
+                logging.debug(
+                    'Controller._on_udev_notification() - %s | %s: Received "%s" event',
+                    self.id,
+                    udev_obj.sys_name,
+                    udev_obj.action,
+                )
+        else:
+            logging.debug(
+                'Controller._on_udev_notification() - %s | %s: Received event on dead object. udev_obj %s: %s',
+                self.id,
+                self.device,
+                udev_obj.action,
+                udev_obj.sys_name,
+            )
+
+    def _on_ctrl_removed(self, udev_obj):  # pylint: disable=unused-argument
+        if self._udev:
+            self._udev.unregister_for_device_events(self._on_udev_notification)
+        self._kill_ops()  # Kill all pending operations
+        self._ctrl = None
+
+        # Defer removal of this object to the next main loop's idle period.
+        GLib.idle_add(self._serv.remove_controller, self, True)
+
+    def _get_cfg(self):
+        '''Get configuration parameters. These may either come from the [Global]
+        section or from a "controller" entry in the configuration file. A
+        definition found in a "controller" entry overrides the same definition
+        found in the [Global] section.
+        '''
+        cfg = {}
+        service_conf = conf.SvcConf()
+        for option, keyword in (
+            ('kato', 'keep_alive_tmo'),
+            ('queue-size', 'queue_size'),
+            ('hdr-digest', 'hdr_digest'),
+            ('data-digest', 'data_digest'),
+            ('nr-io-queues', 'nr_io_queues'),
+            ('ctrl-loss-tmo', 'ctrl_loss_tmo'),
+            ('disable-sqflow', 'disable_sqflow'),
+            ('nr-poll-queues', 'nr_poll_queues'),
+            ('nr-write-queues', 'nr_write_queues'),
+            ('reconnect-delay', 'reconnect_delay'),
+        ):
+            # Check if the value is defined as a "controller" entry (i.e. override)
+            ovrd_val = self.tid.cfg.get(option, None)
+            if ovrd_val is not None:
+                cfg[keyword] = ovrd_val
+            else:
+                # Check if the value is found in the [Global] section.
+                glob_val = service_conf.get_option('Global', option)
+                if glob_val is not None:
+                    cfg[keyword] = glob_val
+
+        return cfg
+
+    def _do_connect(self):
+        service_conf = conf.SvcConf()
+        host_iface = (
+            self.tid.host_iface
+            if (self.tid.host_iface and not service_conf.ignore_iface and self._nvme_options.host_iface_supp)
+            else None
+        )
+        self._ctrl = nvme.ctrl(
+            self._root,
+            subsysnqn=self.tid.subsysnqn,
+            transport=self.tid.transport,
+            traddr=self.tid.traddr,
+            trsvcid=self.tid.trsvcid if self.tid.trsvcid else None,
+            host_traddr=self.tid.host_traddr if self.tid.host_traddr else None,
+            host_iface=host_iface,
+        )
+        self._ctrl.discovery_ctrl_set(self._discovery_ctrl)
+
+        # Set the DHCHAP key on the controller
+        # NOTE that this will eventually have to
+        # change once we have support for AVE (TP8019)
+        ctrl_dhchap_key = self.tid.cfg.get('dhchap-ctrl-secret')
+        if ctrl_dhchap_key and self._nvme_options.dhchap_ctrlkey_supp:
+            has_dhchap_key = hasattr(self._ctrl, 'dhchap_key')
+            if not has_dhchap_key:
+                logging.warning(
+                    '%s | %s - libnvme-%s does not allow setting the controller DHCHAP key. Please upgrade libnvme.',
+                    self.id,
+                    self.device,
+                    defs.LIBNVME_VERSION,
+                )
+            else:
+                self._ctrl.dhchap_key = ctrl_dhchap_key
+
+        # Audit existing nvme devices. If we find a match, then
+        # we'll just borrow that device instead of creating a new one.
+        udev_obj = self._find_existing_connection()
+        if udev_obj is not None:
+            # A device already exists.
+            self._device = udev_obj.sys_name
+            logging.debug(
+                'Controller._do_connect()           - %s Found existing control device: %s', self.id, udev_obj.sys_name
+            )
+            self._connect_op = gutil.AsyncTask(
+                self._on_connect_success, self._on_connect_fail, self._ctrl.init, self._host, int(udev_obj.sys_number)
+            )
+        else:
+            cfg = self._get_cfg()
+            logging.debug(
+                'Controller._do_connect()           - %s Connecting to nvme control with cfg=%s', self.id, cfg
+            )
+            self._connect_op = gutil.AsyncTask(
+                self._on_connect_success, self._on_connect_fail, self._ctrl.connect, self._host, cfg
+            )
+
+        self._connect_op.run_async()
+
+    # --------------------------------------------------------------------------
+    def _on_connect_success(self, op_obj: gutil.AsyncTask, data):
+        '''@brief Function called when we successfully connect to the
+        Controller.
+        '''
+        op_obj.kill()
+        self._connect_op = None
+
+        if self._alive():
+            self._device = self._ctrl.name
+            logging.info('%s | %s - Connection established!', self.id, self.device)
+            self._connect_attempts = 0
+            self._udev.register_for_device_events(self._device, self._on_udev_notification)
+        else:
+            logging.debug(
+                'Controller._on_connect_success()   - %s | %s: Received event on dead object. data=%s',
+                self.id,
+                self.device,
+                data,
+            )
+
+    def _on_connect_fail(self, op_obj: gutil.AsyncTask, err, fail_cnt):  # pylint: disable=unused-argument
+        '''@brief Function called when we fail to connect to the Controller.'''
+        op_obj.kill()
+        self._connect_op = None
+        if self._alive():
+            if self._connect_attempts == 1:
+                # Do a fast re-try on the first failure.
+                self._retry_connect_tmr.set_timeout(self.FAST_CONNECT_RETRY_PERIOD_SEC)
+            elif self._connect_attempts == 2:
+                # If the fast connect re-try fails, then we can print a message to
+                # indicate the failure, and start a slow re-try period.
+                self._retry_connect_tmr.set_timeout(self.CONNECT_RETRY_PERIOD_SEC)
+                logging.error('%s Failed to connect to controller. %s %s', self.id, err.domain, err.message)
+
+            if self._should_try_to_reconnect():
+                logging.debug(
+                    'Controller._on_connect_fail()      - %s %s. Retry in %s sec.',
+                    self.id,
+                    err,
+                    self._retry_connect_tmr.get_timeout(),
+                )
+                self._retry_connect_tmr.start()
+        else:
+            logging.debug(
+                'Controller._on_connect_fail()      - %s Received event on dead object. %s %s',
+                self.id,
+                err.domain,
+                err.message,
+            )
+
+    def disconnect(self, disconnected_cb, keep_connection):
+        '''@brief Issue an asynchronous disconnect command to a Controller.
+        Once the async command has completed, the callback 'disconnected_cb'
+        will be invoked. If a controller is already disconnected, then the
+        callback will be added to the main loop's next idle slot to be executed
+        ASAP.
+
+        @param disconnected_cb: Callback to be called when disconnect has
+        completed. the callback must have this signature:
+            def cback(controller: Controller, success: bool)
+        @param keep_connection: Whether the underlying connection should remain
+        in the kernel.
+        '''
+        logging.debug(
+            'Controller.disconnect()            - %s | %s: keep_connection=%s', self.id, self.device, keep_connection
+        )
+        if self._ctrl and self._ctrl.connected() and not keep_connection:
+            logging.info('%s | %s - Disconnect initiated', self.id, self.device)
+            op = gutil.AsyncTask(self._on_disconn_success, self._on_disconn_fail, self._ctrl.disconnect)
+            op.run_async(disconnected_cb)
+        else:
+            # Defer callback to the next main loop's idle period. The callback
+            # cannot be called directly as the current Controller object is in the
+            # process of being disconnected and the callback will in fact delete
+            # the object. This would invariably lead to unpredictable outcome.
+            GLib.idle_add(disconnected_cb, self, True)
+
+    def _on_disconn_success(self, op_obj: gutil.AsyncTask, data, disconnected_cb):  # pylint: disable=unused-argument
+        logging.debug('Controller._on_disconn_success()   - %s | %s', self.id, self.device)
+        op_obj.kill()
+        # Defer callback to the next main loop's idle period. The callback
+        # cannot be called directly as the current Controller object is in the
+        # process of being disconnected and the callback will in fact delete
+        # the object. This would invariably lead to unpredictable outcome.
+        GLib.idle_add(disconnected_cb, self, True)
+
+    def _on_disconn_fail(
+        self, op_obj: gutil.AsyncTask, err, fail_cnt, disconnected_cb
+    ):  # pylint: disable=unused-argument
+        logging.debug('Controller._on_disconn_fail()      - %s | %s: %s', self.id, self.device, err)
+        op_obj.kill()
+        # Defer callback to the next main loop's idle period. The callback
+        # cannot be called directly as the current Controller object is in the
+        # process of being disconnected and the callback will in fact delete
+        # the object. This would invariably lead to unpredictable outcome.
+        GLib.idle_add(disconnected_cb, self, False)
+
+
+# ******************************************************************************
+class Dc(Controller):
+    '''@brief This object establishes a connection to one Discover Controller (DC).
+    It retrieves the discovery log pages and caches them.
+    It also monitors udev events associated with that DC and updates
+    the cached discovery log pages accordingly.
+    '''
+
+    GET_LOG_PAGE_RETRY_RERIOD_SEC = 20
+    REGISTRATION_RETRY_RERIOD_SEC = 5
+    GET_SUPPORTED_RETRY_RERIOD_SEC = 5
+
+    def __init__(self, staf, tid: trid.TID, log_pages=None, origin=None):
+        super().__init__(tid, staf, discovery_ctrl=True)
+        self._register_op = None
+        self._get_supported_op = None
+        self._get_log_op = None
+        self._origin = origin
+        self._log_pages = log_pages if log_pages else list()  # Log pages cache
+
+        # For Avahi-discovered DCs that later become unresponsive, monitor how
+        # long the controller remains unresponsive and if it does not return for
+        # a configurable soak period (_ctrl_unresponsive_tmr), remove that
+        # controller. Only Avahi-discovered controllers need this timeout-based
+        # cleanup.
+        self._ctrl_unresponsive_time = None  # The time at which connectivity was lost
+        self._ctrl_unresponsive_tmr = gutil.GTimer(0, self._serv.controller_unresponsive, self.tid)
+
+    def _release_resources(self):
+        logging.debug('Dc._release_resources()            - %s | %s', self.id, self.device)
+        super()._release_resources()
+
+        if self._ctrl_unresponsive_tmr is not None:
+            self._ctrl_unresponsive_tmr.kill()
+
+        self._log_pages = list()
+        self._ctrl_unresponsive_tmr = None
+
+    def _kill_ops(self):
+        super()._kill_ops()
+        if self._get_log_op:
+            self._get_log_op.kill()
+            self._get_log_op = None
+        if self._register_op:
+            self._register_op.kill()
+            self._register_op = None
+        if self._get_supported_op:
+            self._get_supported_op.kill()
+            self._get_supported_op = None
+
+    def all_ops_completed(self) -> bool:
+        '''@brief Returns True if all operations have completed. False otherwise.'''
+        return (
+            super().all_ops_completed()
+            and (self._get_log_op is None or self._get_log_op.completed())
+            and (self._register_op is None or self._register_op.completed())
+            and (self._get_supported_op is None or self._get_supported_op.completed())
+        )
+
+    @property
+    def origin(self):
+        '''@brief Return how this controller came into existance. Was it
+        "discovered" through mDNS service discovery (TP8009), was it manually
+        "configured" in stafd.conf, or was it a "referral".
+        '''
+        return self._origin
+
+    @origin.setter
+    def origin(self, value):
+        '''@brief Set the origin of this controller.'''
+        if value in ('discovered', 'configured', 'referral'):
+            self._origin = value
+            self._handle_lost_controller()
+        else:
+            logging.error('%s | %s - Trying to set invalid origin to %s', self.id, self.device, value)
+
+    def reload_hdlr(self):
+        '''@brief This is called when a "reload" signal is received.'''
+        logging.debug('Dc.reload_hdlr()                   - %s | %s', self.id, self.device)
+
+        self._handle_lost_controller()
+        self._resync_with_controller()
+
+    def info(self) -> dict:
+        '''@brief Get the controller info for this object'''
+        timeout = conf.SvcConf().zeroconf_persistence_sec
+        unresponsive_time = (
+            time.asctime(self._ctrl_unresponsive_time) if self._ctrl_unresponsive_time is not None else '---'
+        )
+        info = super().info()
+        info['origin'] = self.origin
+        if self.origin == 'discovered':
+            # The code that handles "unresponsive" DCs only applies to
+            # discovered DCs. So, let's only print that info when it's relevant.
+            info['unresponsive timer'] = str(self._ctrl_unresponsive_tmr)
+            info['unresponsive timeout'] = f'{timeout} sec' if timeout >= 0 else 'forever'
+            info['unresponsive time'] = unresponsive_time
+        if self._get_log_op:
+            info['get log page operation'] = str(self._get_log_op.as_dict())
+        if self._register_op:
+            info['register operation'] = str(self._register_op.as_dict())
+        if self._get_supported_op:
+            info['get supported log page operation'] = str(self._get_supported_op.as_dict())
+        return info
+
+    def cancel(self):
+        '''@brief Used to cancel pending operations.'''
+        super().cancel()
+        if self._get_log_op:
+            self._get_log_op.cancel()
+        if self._register_op:
+            self._register_op.cancel()
+        if self._get_supported_op:
+            self._get_supported_op.cancel()
+
+    def log_pages(self) -> list:
+        '''@brief Get the cached log pages for this object'''
+        return self._log_pages
+
+    def referrals(self) -> list:
+        '''@brief Return the list of referrals'''
+        return [page for page in self._log_pages if page['subtype'] == 'referral']
+
+    def _is_ddc(self):
+        return self._ctrl and self._ctrl.dctype != 'cdc'
+
+    def _on_aen(self, aen: int):
+        if aen == DLP_CHANGED and self._get_log_op:
+            self._get_log_op.run_async()
+
+    def _handle_lost_controller(self):
+        if self.origin == 'discovered':  # Only apply to mDNS-discovered DCs
+            if not self._serv.is_avahi_reported(self.tid) and not self.connected():
+                timeout = conf.SvcConf().zeroconf_persistence_sec
+                if timeout >= 0:
+                    if self._ctrl_unresponsive_time is None:
+                        self._ctrl_unresponsive_time = time.localtime()
+                        self._ctrl_unresponsive_tmr.start(timeout)
+                        logging.info(
+                            '%s | %s - Controller is not responding. Will be removed by %s unless restored',
+                            self.id,
+                            self.device,
+                            time.ctime(time.mktime(self._ctrl_unresponsive_time) + timeout),
+                        )
+
+                    return
+
+                logging.info(
+                    '%s | %s - Controller not responding. Retrying...',
+                    self.id,
+                    self.device,
+                )
+
+        self._ctrl_unresponsive_time = None
+        self._ctrl_unresponsive_tmr.stop()
+        self._ctrl_unresponsive_tmr.set_timeout(0)
+
+    def is_unresponsive(self):
+        '''@brief For "discovered" DC, return True if DC is unresponsive,
+        False otherwise.
+        '''
+        return (
+            self.origin == 'discovered'
+            and not self._serv.is_avahi_reported(self.tid)
+            and not self.connected()
+            and self._ctrl_unresponsive_time is not None
+            and self._ctrl_unresponsive_tmr.time_remaining() <= 0
+        )
+
+    def _resync_with_controller(self):
+        '''Communicate with DC to resync the states'''
+        if self._register_op:
+            self._register_op.run_async()
+        elif self._get_supported_op:
+            self._get_supported_op.run_async()
+        elif self._get_log_op:
+            self._get_log_op.run_async()
+
+    def _on_nvme_event(self, nvme_event: str):
+        if nvme_event in ('connected', 'rediscover'):
+            # This event indicates that the kernel
+            # driver re-connected to the DC.
+            logging.debug(
+                'Dc._on_nvme_event()                - %s | %s: Received "%s" event',
+                self.id,
+                self.device,
+                nvme_event,
+            )
+            self._resync_with_controller()
+
+    def _find_existing_connection(self):
+        return self._udev.find_nvme_dc_device(self.tid)
+
+    def _post_registration_actions(self):
+        # Need to check that supported_log_pages() is available (introduced in libnvme 1.2)
+        has_supported_log_pages = hasattr(self._ctrl, 'supported_log_pages')
+        if not has_supported_log_pages:
+            logging.warning(
+                '%s | %s - libnvme-%s does not support "Get supported log pages". Please upgrade libnvme.',
+                self.id,
+                self.device,
+                defs.LIBNVME_VERSION,
+            )
+
+        if conf.SvcConf().pleo_enabled and self._is_ddc() and has_supported_log_pages:
+            self._get_supported_op = gutil.AsyncTask(
+                self._on_get_supported_success, self._on_get_supported_fail, self._ctrl.supported_log_pages
+            )
+            self._get_supported_op.run_async()
+        else:
+            self._get_log_op = gutil.AsyncTask(self._on_get_log_success, self._on_get_log_fail, self._ctrl.discover)
+            self._get_log_op.run_async()
+
+    # --------------------------------------------------------------------------
+    def _on_connect_success(self, op_obj: gutil.AsyncTask, data):
+        '''@brief Function called when we successfully connect to the
+        Discovery Controller.
+        '''
+        super()._on_connect_success(op_obj, data)
+
+        if self._alive():
+            self._ctrl_unresponsive_time = None
+            self._ctrl_unresponsive_tmr.stop()
+            self._ctrl_unresponsive_tmr.set_timeout(0)
+
+            if self._ctrl.is_registration_supported():
+                self._register_op = gutil.AsyncTask(
+                    self._on_registration_success,
+                    self._on_registration_fail,
+                    self._ctrl.registration_ctlr,
+                    nvme.NVMF_DIM_TAS_REGISTER,
+                )
+                self._register_op.run_async()
+            else:
+                self._post_registration_actions()
+
+    def _on_connect_fail(self, op_obj: gutil.AsyncTask, err, fail_cnt):
+        '''@brief Function called when we fail to connect to the Controller.'''
+        super()._on_connect_fail(op_obj, err, fail_cnt)
+
+        if self._alive():
+            self._handle_lost_controller()
+
+    # --------------------------------------------------------------------------
+    def _on_registration_success(self, op_obj: gutil.AsyncTask, data):  # pylint: disable=unused-argument
+        '''@brief Function called when we successfully register with the
+        Discovery Controller. See self._register_op object
+        for details.
+
+        NOTE: The name _on_registration_success() may be misleading. "success"
+        refers to the fact that a successful exchange was made with the DC.
+        It doesn't mean that the registration itself succeeded.
+        '''
+        if self._alive():
+            if data is not None:
+                logging.warning('%s | %s - Registration error. %s.', self.id, self.device, data)
+            else:
+                logging.debug('Dc._on_registration_success()      - %s | %s', self.id, self.device)
+
+            self._post_registration_actions()
+        else:
+            logging.debug(
+                'Dc._on_registration_success()      - %s | %s: Received event on dead object.', self.id, self.device
+            )
+
+    def _on_registration_fail(self, op_obj: gutil.AsyncTask, err, fail_cnt):
+        '''@brief Function called when we fail to register with the
+        Discovery Controller. See self._register_op object
+        for details.
+        '''
+        if self._alive():
+            logging.debug(
+                'Dc._on_registration_fail()         - %s | %s: %s. Retry in %s sec',
+                self.id,
+                self.device,
+                err,
+                Dc.REGISTRATION_RETRY_RERIOD_SEC,
+            )
+            if fail_cnt == 1:  # Throttle the logs. Only print the first time the command fails
+                logging.error('%s | %s - Failed to register with Discovery Controller. %s', self.id, self.device, err)
+            op_obj.retry(Dc.REGISTRATION_RETRY_RERIOD_SEC)
+        else:
+            logging.debug(
+                'Dc._on_registration_fail()         - %s | %s: Received event on dead object. %s',
+                self.id,
+                self.device,
+                err,
+            )
+            op_obj.kill()
+
+    # --------------------------------------------------------------------------
+    def _on_get_supported_success(self, op_obj: gutil.AsyncTask, data):  # pylint: disable=unused-argument
+        '''@brief Function called when we successfully retrieved the supported
+        log pages from the Discovery Controller. See self._get_supported_op object
+        for details.
+
+        NOTE: The name _on_get_supported_success() may be misleading. "success"
+        refers to the fact that a successful exchange was made with the DC.
+        It doesn't mean that the Get Supported Log Page itself succeeded.
+        '''
+        if self._alive():
+            try:
+                dlp_supp_opts = data[nvme.NVME_LOG_LID_DISCOVER] >> 16
+            except (TypeError, IndexError):
+                dlp_supp_opts = 0
+
+            logging.debug(
+                'Dc._on_get_supported_success()     - %s | %s: supported options = 0x%04X = %s',
+                self.id,
+                self.device,
+                dlp_supp_opts,
+                dlp_supp_opts_as_string(dlp_supp_opts),
+            )
+
+            if 'lsp' in inspect.signature(self._ctrl.discover).parameters:
+                lsp = nvme.NVMF_LOG_DISC_LSP_PLEO if dlp_supp_opts & nvme.NVMF_LOG_DISC_LID_PLEOS else 0
+                self._get_log_op = gutil.AsyncTask(
+                    self._on_get_log_success, self._on_get_log_fail, self._ctrl.discover, lsp
+                )
+            else:
+                logging.warning(
+                    '%s | %s - libnvme-%s does not support setting PLEO bit. Please upgrade.',
+                    self.id,
+                    self.device,
+                    defs.LIBNVME_VERSION,
+                )
+                self._get_log_op = gutil.AsyncTask(self._on_get_log_success, self._on_get_log_fail, self._ctrl.discover)
+            self._get_log_op.run_async()
+        else:
+            logging.debug(
+                'Dc._on_get_supported_success()     - %s | %s: Received event on dead object.', self.id, self.device
+            )
+
+    def _on_get_supported_fail(self, op_obj: gutil.AsyncTask, err, fail_cnt):
+        '''@brief Function called when we fail to retrieve the supported log
+        page from the Discovery Controller. See self._get_supported_op object
+        for details.
+        '''
+        if self._alive():
+            logging.debug(
+                'Dc._on_get_supported_fail()        - %s | %s: %s. Retry in %s sec',
+                self.id,
+                self.device,
+                err,
+                Dc.GET_SUPPORTED_RETRY_RERIOD_SEC,
+            )
+            if fail_cnt == 1:  # Throttle the logs. Only print the first time the command fails
+                logging.error(
+                    '%s | %s - Failed to Get supported log pages from Discovery Controller. %s',
+                    self.id,
+                    self.device,
+                    err,
+                )
+            op_obj.retry(Dc.GET_SUPPORTED_RETRY_RERIOD_SEC)
+        else:
+            logging.debug(
+                'Dc._on_get_supported_fail()        - %s | %s: Received event on dead object. %s',
+                self.id,
+                self.device,
+                err,
+            )
+            op_obj.kill()
+
+    # --------------------------------------------------------------------------
+    def _on_get_log_success(self, op_obj: gutil.AsyncTask, data):  # pylint: disable=unused-argument
+        '''@brief Function called when we successfully retrieve the log pages
+        from the Discovery Controller. See self._get_log_op object
+        for details.
+        '''
+        if self._alive():
+            # Note that for historical reasons too long to explain, the CDC may
+            # return invalid addresses ('0.0.0.0', '::', or ''). Those need to
+            # be filtered out.
+            referrals_before = self.referrals()
+            self._log_pages = (
+                [
+                    {k.strip(): str(v).strip() for k, v in dictionary.items()}
+                    for dictionary in data
+                    if dictionary.get('traddr', '').strip() not in ('0.0.0.0', '::', '')
+                ]
+                if data
+                else list()
+            )
+            logging.info(
+                '%s | %s - Received discovery log pages (num records=%s).', self.id, self.device, len(self._log_pages)
+            )
+            referrals_after = self.referrals()
+            self._serv.log_pages_changed(self, self.device)
+            if referrals_after != referrals_before:
+                logging.debug(
+                    'Dc._on_get_log_success()           - %s | %s: Referrals before = %s',
+                    self.id,
+                    self.device,
+                    referrals_before,
+                )
+                logging.debug(
+                    'Dc._on_get_log_success()           - %s | %s: Referrals after  = %s',
+                    self.id,
+                    self.device,
+                    referrals_after,
+                )
+                self._serv.referrals_changed()
+        else:
+            logging.debug(
+                'Dc._on_get_log_success()           - %s | %s: Received event on dead object.', self.id, self.device
+            )
+
+    def _on_get_log_fail(self, op_obj: gutil.AsyncTask, err, fail_cnt):
+        '''@brief Function called when we fail to retrieve the log pages
+        from the Discovery Controller. See self._get_log_op object
+        for details.
+        '''
+        if self._alive():
+            logging.debug(
+                'Dc._on_get_log_fail()              - %s | %s: %s. Retry in %s sec',
+                self.id,
+                self.device,
+                err,
+                Dc.GET_LOG_PAGE_RETRY_RERIOD_SEC,
+            )
+            if fail_cnt == 1:  # Throttle the logs. Only print the first time the command fails
+                logging.error('%s | %s - Failed to retrieve log pages. %s', self.id, self.device, err)
+            op_obj.retry(Dc.GET_LOG_PAGE_RETRY_RERIOD_SEC)
+        else:
+            logging.debug(
+                'Dc._on_get_log_fail()              - %s | %s: Received event on dead object. %s',
+                self.id,
+                self.device,
+                err,
+            )
+            op_obj.kill()
+
+
+# ******************************************************************************
+class Ioc(Controller):
+    '''@brief This object establishes a connection to one I/O Controller.'''
+
+    def __init__(self, stac, tid: trid.TID):
+        self._dlpe = None
+        super().__init__(tid, stac)
+
+    def _find_existing_connection(self):
+        return self._udev.find_nvme_ioc_device(self.tid)
+
+    def _on_aen(self, aen: int):
+        pass
+
+    def _on_nvme_event(self, nvme_event):
+        pass
+
+    def reload_hdlr(self):
+        '''@brief This is called when a "reload" signal is received.'''
+        if not self.connected() and self._retry_connect_tmr.time_remaining() == 0:
+            self._try_to_connect_deferred.schedule()
+
+    @property
+    def eflags(self):
+        '''@brief Return the eflag field of the DLPE'''
+        return get_eflags(self._dlpe)
+
+    @property
+    def ncc(self):
+        '''@brief Return Not Connected to CDC status'''
+        return get_ncc(self.eflags)
+
+    def details(self) -> dict:
+        '''@brief return detailed debug info about this controller'''
+        details = super().details()
+        details['dlpe'] = str(self._dlpe)
+        details['dlpe.eflags.ncc'] = str(self.ncc)
+        return details
+
+    def update_dlpe(self, dlpe):
+        '''@brief This method is called when a new DLPE associated
+        with this controller is received.'''
+        new_ncc = get_ncc(get_eflags(dlpe))
+        old_ncc = self.ncc
+        self._dlpe = dlpe
+
+        if old_ncc and not new_ncc:  # NCC bit cleared?
+            if not self.connected():
+                self._connect_attempts = 0
+                self._try_to_connect_deferred.schedule()
+
+    def _should_try_to_reconnect(self):
+        '''@brief This is used to determine when it's time to stop trying toi connect'''
+        max_connect_attempts = conf.SvcConf().connect_attempts_on_ncc if self.ncc else 0
+        return max_connect_attempts == 0 or self._connect_attempts < max_connect_attempts
diff --git a/staslib/defs.py b/staslib/defs.py
new file mode 100644
index 0000000..5a50371
--- /dev/null
+++ b/staslib/defs.py
@@ -0,0 +1,51 @@
+# Copyright (c) 2021, Dell Inc. or its subsidiaries.  All rights reserved.
+# SPDX-License-Identifier: Apache-2.0
+# See the LICENSE file for details.
+#
+# This file is part of NVMe STorage Appliance Services (nvme-stas).
+#
+# Authors: Martin Belanger <Martin.Belanger@dell.com>
+
+''' @brief This file gets automagically configured by meson at build time.
+'''
+import os
+import sys
+import shutil
+import platform
+from staslib.version import KernelVersion
+
+try:
+    import libnvme
+
+    LIBNVME_VERSION = libnvme.__version__
+except (AttributeError, ModuleNotFoundError):
+    LIBNVME_VERSION = '?.?'
+
+VERSION = '@VERSION@'
+LICENSE = '@LICENSE@'
+
+STACD_DBUS_NAME = '@STACD_DBUS_NAME@'
+STACD_DBUS_PATH = '@STACD_DBUS_PATH@'
+
+STAFD_DBUS_NAME = '@STAFD_DBUS_NAME@'
+STAFD_DBUS_PATH = '@STAFD_DBUS_PATH@'
+
+KERNEL_VERSION = KernelVersion(platform.release())
+KERNEL_IFACE_MIN_VERSION = KernelVersion('5.14')
+KERNEL_TP8013_MIN_VERSION = KernelVersion('5.16')
+KERNEL_HOSTKEY_MIN_VERSION = KernelVersion('5.20')
+KERNEL_CTRLKEY_MIN_VERSION = KernelVersion('5.20')
+
+WELL_KNOWN_DISC_NQN = 'nqn.2014-08.org.nvmexpress.discovery'
+
+PROG_NAME = os.path.basename(sys.argv[0])
+
+NVME_HOSTID = '/etc/nvme/hostid'
+NVME_HOSTNQN = '/etc/nvme/hostnqn'
+NVME_HOSTKEY = '/etc/nvme/hostkey'
+
+SYS_CONF_FILE = '/etc/stas/sys.conf'
+STAFD_CONF_FILE = '/etc/stas/stafd.conf'
+STACD_CONF_FILE = '/etc/stas/stacd.conf'
+
+SYSTEMCTL = shutil.which('systemctl')
diff --git a/staslib/gutil.py b/staslib/gutil.py
new file mode 100644
index 0000000..c40b80e
--- /dev/null
+++ b/staslib/gutil.py
@@ -0,0 +1,418 @@
+# Copyright (c) 2022, Dell Inc. or its subsidiaries.  All rights reserved.
+# SPDX-License-Identifier: Apache-2.0
+# See the LICENSE file for details.
+#
+# This file is part of NVMe STorage Appliance Services (nvme-stas).
+#
+# Authors: Martin Belanger <Martin.Belanger@dell.com>
+#
+'''This module provides utility functions/classes to provide easier to use
+access to GLib/Gio/Gobject resources.
+'''
+
+import logging
+from gi.repository import Gio, GLib, GObject
+from staslib import conf, iputil, trid
+
+
+# ******************************************************************************
+class GTimer:
+    '''@brief Convenience class to wrap GLib timers'''
+
+    def __init__(
+        self, interval_sec: float = 0, user_cback=lambda: GLib.SOURCE_REMOVE, *user_data, priority=GLib.PRIORITY_DEFAULT
+    ):  # pylint: disable=keyword-arg-before-vararg
+        self._source = None
+        self._interval_sec = float(interval_sec)
+        self._user_cback = user_cback
+        self._user_data = user_data
+        self._priority = priority if priority is not None else GLib.PRIORITY_DEFAULT
+
+    def _release_resources(self):
+        self.stop()
+        self._user_cback = None
+        self._user_data = None
+
+    def kill(self):
+        '''@brief Used to release all resources associated with a timer.'''
+        self._release_resources()
+
+    def __str__(self):
+        if self._source is not None:
+            return f'{self._interval_sec}s [{self.time_remaining()}s]'
+
+        return f'{self._interval_sec}s [off]'
+
+    def _callback(self, *_):
+        retval = self._user_cback(*self._user_data)
+        if retval == GLib.SOURCE_REMOVE:
+            self._source = None
+        return retval
+
+    def stop(self):
+        '''@brief Stop timer'''
+        if self._source is not None:
+            self._source.destroy()
+            self._source = None
+
+    def start(self, new_interval_sec: float = -1.0):
+        '''@brief Start (or restart) timer'''
+        if new_interval_sec >= 0:
+            self._interval_sec = float(new_interval_sec)
+
+        if self._source is not None:
+            self._source.set_ready_time(
+                self._source.get_time() + (self._interval_sec * 1000000)
+            )  # ready time is in micro-seconds (monotonic time)
+        else:
+            if self._interval_sec.is_integer():
+                self._source = GLib.timeout_source_new_seconds(int(self._interval_sec))  # seconds resolution
+            else:
+                self._source = GLib.timeout_source_new(self._interval_sec * 1000.0)  # mili-seconds resolution
+
+            self._source.set_priority(self._priority)
+            self._source.set_callback(self._callback)
+            self._source.attach()
+
+    def clear(self):
+        '''@brief Make timer expire now. The callback function
+        will be invoked immediately by the main loop.
+        '''
+        if self._source is not None:
+            self._source.set_ready_time(0)  # Expire now!
+
+    def set_callback(self, user_cback, *user_data):
+        '''@brief set the callback function to invoke when timer expires'''
+        self._user_cback = user_cback
+        self._user_data = user_data
+
+    def set_timeout(self, new_interval_sec: float):
+        '''@brief set the timer's duration'''
+        if new_interval_sec >= 0:
+            self._interval_sec = float(new_interval_sec)
+
+    def get_timeout(self):
+        '''@brief get the timer's duration'''
+        return self._interval_sec
+
+    def time_remaining(self) -> float:
+        '''@brief Get how much time remains on a timer before it fires.'''
+        if self._source is not None:
+            delta_us = self._source.get_ready_time() - self._source.get_time()  # monotonic time in micro-seconds
+            if delta_us > 0:
+                return delta_us / 1000000.0
+
+        return 0
+
+
+# ******************************************************************************
+class NameResolver:  # pylint: disable=too-few-public-methods
+    '''@brief DNS resolver to convert host names to IP addresses.'''
+
+    def __init__(self):
+        self._resolver = Gio.Resolver.get_default()
+
+    def resolve_ctrl_async(self, cancellable, controllers_in: list, callback):
+        '''@brief The traddr fields may specify a hostname instead of an IP
+        address. We need to resolve all the host names to addresses.
+        Resolving hostnames may take a while as a DNS server may need
+        to be contacted. For that reason, we're using async APIs with
+        callbacks to resolve all the hostnames.
+
+        The callback @callback will be called once all hostnames have
+        been resolved.
+
+        @param controllers: List of trid.TID
+        '''
+        pending_resolution_count = 0
+        controllers_out = []
+        service_conf = conf.SvcConf()
+
+        def addr_resolved(resolver, result, controller):
+            try:
+                addresses = resolver.lookup_by_name_finish(result)  # List of Gio.InetAddress objects
+
+            except GLib.GError as err:
+                # We don't need to report "cancellation" errors.
+                if err.matches(Gio.io_error_quark(), Gio.IOErrorEnum.CANCELLED):
+                    # pylint: disable=no-member
+                    logging.debug('NameResolver.resolve_ctrl_async()  - %s %s', err.message, controller)
+                else:
+                    logging.error('%s', err.message)  # pylint: disable=no-member
+
+                # if err.matches(Gio.resolver_error_quark(), Gio.ResolverError.TEMPORARY_FAILURE):
+                # elif err.matches(Gio.resolver_error_quark(), Gio.ResolverError.NOT_FOUND):
+                # elif err.matches(Gio.resolver_error_quark(), Gio.ResolverError.INTERNAL):
+
+            else:
+                traddr = None
+
+                # If multiple addresses are returned (which is often the case),
+                # prefer IPv4 addresses over IPv6.
+                if 4 in service_conf.ip_family:
+                    for address in addresses:
+                        # There may be multiple IPv4 addresses. Pick 1st one.
+                        if address.get_family() == Gio.SocketFamily.IPV4:
+                            traddr = address.to_string()
+                            break
+
+                if traddr is None and 6 in service_conf.ip_family:
+                    for address in addresses:
+                        # There may be multiple IPv6 addresses. Pick 1st one.
+                        if address.get_family() == Gio.SocketFamily.IPV6:
+                            traddr = address.to_string()
+                            break
+
+                if traddr is not None:
+                    logging.debug(
+                        'NameResolver.resolve_ctrl_async()  - resolved \'%s\' -> %s', controller.traddr, traddr
+                    )
+                    cid = controller.as_dict()
+                    cid['traddr'] = traddr
+                    nonlocal controllers_out
+                    controllers_out.append(trid.TID(cid))
+
+            # Invoke callback after all hostnames have been resolved
+            nonlocal pending_resolution_count
+            pending_resolution_count -= 1
+            if pending_resolution_count == 0:
+                callback(controllers_out)
+
+        for controller in controllers_in:
+            if controller.transport in ('tcp', 'rdma'):
+                hostname_or_addr = controller.traddr
+                if not hostname_or_addr:
+                    logging.error('Invalid traddr: %s', controller)
+                else:
+                    # Try to convert to an ipaddress object. If this
+                    # succeeds, then we don't need to call the resolver.
+                    ip = iputil.get_ipaddress_obj(hostname_or_addr)
+                    if ip is None:
+                        logging.debug('NameResolver.resolve_ctrl_async()  - resolving \'%s\'', hostname_or_addr)
+                        pending_resolution_count += 1
+                        self._resolver.lookup_by_name_async(hostname_or_addr, cancellable, addr_resolved, controller)
+                    elif ip.version in service_conf.ip_family:
+                        controllers_out.append(controller)
+                    else:
+                        logging.warning(
+                            'Excluding configured IP address %s based on "ip-family" setting', hostname_or_addr
+                        )
+            else:
+                controllers_out.append(controller)
+
+        if pending_resolution_count == 0:  # No names are pending asynchronous resolution
+            callback(controllers_out)
+
+
+# ******************************************************************************
+class _TaskRunner(GObject.Object):
+    '''@brief This class allows running methods asynchronously in a thread.'''
+
+    def __init__(self, user_function, *user_args):
+        '''@param user_function: function to run inside a thread
+        @param user_args: arguments passed to @user_function
+        '''
+        super().__init__()
+        self._user_function = user_function
+        self._user_args = user_args
+
+    def communicate(self, cancellable, cb_function, *cb_args):
+        '''@param cancellable: A Gio.Cancellable object that can be used to
+                            cancel an in-flight async command.
+        @param cb_function: User callback function to call when the async
+                            command has completed.  The callback function
+                            will be passed these arguments:
+
+                                (runner, result, *cb_args)
+
+                            Where:
+                                runner: This _TaskRunner object instance
+                                result: A GObject.Object instance that contains the result
+                                cb_args: The cb_args arguments passed to communicate()
+
+        @param cb_args: User arguments to pass to @cb_function
+        '''
+
+        def in_thread_exec(task, self, task_data, cancellable):  # pylint: disable=unused-argument
+            if task.return_error_if_cancelled():
+                return  # Bail out if task has been cancelled
+
+            try:
+                value = GObject.Object()
+                value.result = self._user_function(*self._user_args)
+                task.return_value(value)
+            except Exception as ex:  # pylint: disable=broad-except
+                task.return_error(GLib.Error(message=str(ex), domain=type(ex).__name__))
+
+        task = Gio.Task.new(self, cancellable, cb_function, *cb_args)
+        task.set_return_on_cancel(False)
+        task.run_in_thread(in_thread_exec)
+        return task
+
+    def communicate_finish(self, result):  # pylint: disable=no-self-use
+        '''@brief Use this function in your callback (see @cb_function) to
+         extract data from the result object.
+
+        @return On success (True, data, None),
+        On failure (False, None, err: GLib.Error)
+        '''
+        try:
+            success, value = result.propagate_value()
+            return success, value.result, None
+        except GLib.Error as err:
+            return False, None, err
+
+
+# ******************************************************************************
+class AsyncTask:  # pylint: disable=too-many-instance-attributes
+    '''Object used to manage an asynchronous GLib operation. The operation
+    can be cancelled or retried.
+    '''
+
+    def __init__(self, on_success_callback, on_failure_callback, operation, *op_args):
+        '''@param on_success_callback: Callback method invoked when @operation completes successfully
+        @param on_failure_callback: Callback method invoked when @operation fails
+        @param operation: Operation (i.e. a function) to execute asynchronously
+        @param op_args: Arguments passed to operation
+        '''
+        self._cancellable = Gio.Cancellable()
+        self._operation = operation
+        self._op_args = op_args
+        self._success_cb = on_success_callback
+        self._fail_cb = on_failure_callback
+        self._retry_tmr = None
+        self._errmsg = None
+        self._task = None
+        self._fail_cnt = 0
+
+    def _release_resources(self):
+        if self._alive():
+            self._cancellable.cancel()
+
+        if self._retry_tmr is not None:
+            self._retry_tmr.kill()
+
+        self._operation = None
+        self._op_args = None
+        self._success_cb = None
+        self._fail_cb = None
+        self._retry_tmr = None
+        self._errmsg = None
+        self._task = None
+        self._fail_cnt = None
+        self._cancellable = None
+
+    def __str__(self):
+        return str(self.as_dict())
+
+    def as_dict(self):
+        '''Return object members as a dictionary'''
+        info = {
+            'fail count': self._fail_cnt,
+            'completed': self._task.get_completed(),
+            'alive': self._alive(),
+        }
+
+        if self._retry_tmr:
+            info['retry timer'] = str(self._retry_tmr)
+
+        if self._errmsg:
+            info['error'] = self._errmsg
+
+        return info
+
+    def _alive(self):
+        return self._cancellable and not self._cancellable.is_cancelled()
+
+    def completed(self):
+        '''@brief Returns True if the task has completed, False otherwise.'''
+        return self._task is not None and self._task.get_completed()
+
+    def cancel(self):
+        '''@brief cancel async operation'''
+        if self._alive():
+            self._cancellable.cancel()
+
+    def kill(self):
+        '''@brief kill and clean up this object'''
+        self._release_resources()
+
+    def run_async(self, *args):
+        '''@brief
+        Method used to initiate an asynchronous operation with the
+        Controller. When the operation completes (or fails) the
+        callback method @_on_operation_complete() will be invoked.
+        '''
+        runner = _TaskRunner(self._operation, *self._op_args)
+        self._task = runner.communicate(self._cancellable, self._on_operation_complete, *args)
+
+    def retry(self, interval_sec, *args):
+        '''@brief Tell this object that the async operation is to be retried
+        in @interval_sec seconds.
+
+        '''
+        if self._retry_tmr is None:
+            self._retry_tmr = GTimer()
+        self._retry_tmr.set_callback(self._on_retry_timeout, *args)
+        self._retry_tmr.start(interval_sec)
+
+    def _on_retry_timeout(self, *args):
+        '''@brief
+        When an operation fails, the application has the option to
+        retry at a later time by calling the retry() method. The
+        retry() method starts a timer at the end of which the operation
+        will be executed again. This is the method that is called when
+        the timer expires.
+        '''
+        if self._alive():
+            self.run_async(*args)
+        return GLib.SOURCE_REMOVE
+
+    def _on_operation_complete(self, runner, result, *args):
+        '''@brief
+        This callback method is invoked when the operation with the
+        Controller has completed (be it successful or not).
+        '''
+        # The operation might have been cancelled.
+        # Only proceed if it hasn't been cancelled.
+        if self._operation is None or not self._alive():
+            return
+
+        success, data, err = runner.communicate_finish(result)
+
+        if success:
+            self._errmsg = None
+            self._fail_cnt = 0
+            self._success_cb(self, data, *args)
+        else:
+            self._errmsg = str(err)
+            self._fail_cnt += 1
+            self._fail_cb(self, err, self._fail_cnt, *args)
+
+
+# ******************************************************************************
+class Deferred:
+    '''Implement a deferred function call. A deferred is a function that gets
+    added to the main loop to be executed during the next idle slot.'''
+
+    def __init__(self, func, *user_data):
+        self._source = None
+        self._func = func
+        self._user_data = user_data
+
+    def schedule(self):
+        '''Schedule the function to be called by the main loop. If the
+        function  is already scheduled, then do nothing'''
+        if not self.is_scheduled():
+            srce_id = GLib.idle_add(self._func, *self._user_data)
+            self._source = GLib.main_context_default().find_source_by_id(srce_id)
+
+    def is_scheduled(self):
+        '''Check if deferred is currently schedules to run'''
+        return self._source and not self._source.is_destroyed()
+
+    def cancel(self):
+        '''Remove deferred from main loop'''
+        if self.is_scheduled():
+            self._source.destroy()
+        self._source = None
diff --git a/staslib/iputil.py b/staslib/iputil.py
new file mode 100644
index 0000000..9199a49
--- /dev/null
+++ b/staslib/iputil.py
@@ -0,0 +1,169 @@
+# Copyright (c) 2022, Dell Inc. or its subsidiaries.  All rights reserved.
+# SPDX-License-Identifier: Apache-2.0
+# See the LICENSE file for details.
+#
+# This file is part of NVMe STorage Appliance Services (nvme-stas).
+#
+# Authors: Martin Belanger <Martin.Belanger@dell.com>
+
+'''A collection of IP address and network interface utilities'''
+
+import socket
+import logging
+import ipaddress
+from staslib import conf
+
+RTM_NEWADDR = 20
+RTM_GETADDR = 22
+NLM_F_REQUEST = 0x01
+NLM_F_ROOT = 0x100
+NLMSG_DONE = 3
+IFLA_ADDRESS = 1
+NLMSGHDR_SZ = 16
+IFADDRMSG_SZ = 8
+RTATTR_SZ = 4
+
+# Netlink request (Get address command)
+GETADDRCMD = (
+    # BEGIN: struct nlmsghdr
+    b'\0' * 4  # nlmsg_len (placeholder - actual length calculated below)
+    + (RTM_GETADDR).to_bytes(2, byteorder='little', signed=False)  # nlmsg_type
+    + (NLM_F_REQUEST | NLM_F_ROOT).to_bytes(2, byteorder='little', signed=False)  # nlmsg_flags
+    + b'\0' * 2  # nlmsg_seq
+    + b'\0' * 2  # nlmsg_pid
+    # END: struct nlmsghdr
+    + b'\0' * 8  # struct ifaddrmsg
+)
+GETADDRCMD = len(GETADDRCMD).to_bytes(4, byteorder='little') + GETADDRCMD[4:]  # nlmsg_len
+
+
+# ******************************************************************************
+def get_ipaddress_obj(ipaddr):
+    '''@brief Return a IPv4Address or IPv6Address depending on whether @ipaddr
+    is a valid IPv4 or IPv6 address. Return None otherwise.'''
+    try:
+        ip = ipaddress.ip_address(ipaddr)
+    except ValueError:
+        return None
+
+    return ip
+
+
+# ******************************************************************************
+def _data_matches_ip(data_family, data, ip):
+    if data_family == socket.AF_INET:
+        try:
+            other_ip = ipaddress.IPv4Address(data)
+        except ValueError:
+            return False
+        if ip.version == 6:
+            ip = ip.ipv4_mapped
+    elif data_family == socket.AF_INET6:
+        try:
+            other_ip = ipaddress.IPv6Address(data)
+        except ValueError:
+            return False
+        if ip.version == 4:
+            other_ip = other_ip.ipv4_mapped
+    else:
+        return False
+
+    return other_ip == ip
+
+
+# ******************************************************************************
+def iface_of(src_addr):
+    '''@brief Find the interface that has src_addr as one of its assigned IP addresses.
+    @param src_addr: The IP address to match
+    @type src_addr: Instance of ipaddress.IPv4Address or ipaddress.IPv6Address
+    '''
+    with socket.socket(socket.AF_NETLINK, socket.SOCK_RAW) as sock:
+        sock.sendall(GETADDRCMD)
+        nlmsg = sock.recv(8192)
+        nlmsg_idx = 0
+        while True:
+            if nlmsg_idx >= len(nlmsg):
+                nlmsg += sock.recv(8192)
+
+            nlmsg_type = int.from_bytes(nlmsg[nlmsg_idx + 4 : nlmsg_idx + 6], byteorder='little', signed=False)
+            if nlmsg_type == NLMSG_DONE:
+                break
+
+            if nlmsg_type != RTM_NEWADDR:
+                break
+
+            nlmsg_len = int.from_bytes(nlmsg[nlmsg_idx : nlmsg_idx + 4], byteorder='little', signed=False)
+            if nlmsg_len % 4:  # Is msg length not a multiple of 4?
+                break
+
+            ifaddrmsg_indx = nlmsg_idx + NLMSGHDR_SZ
+            ifa_family = nlmsg[ifaddrmsg_indx]
+            ifa_index = int.from_bytes(nlmsg[ifaddrmsg_indx + 4 : ifaddrmsg_indx + 8], byteorder='little', signed=False)
+
+            rtattr_indx = ifaddrmsg_indx + IFADDRMSG_SZ
+            while rtattr_indx < (nlmsg_idx + nlmsg_len):
+                rta_len = int.from_bytes(nlmsg[rtattr_indx : rtattr_indx + 2], byteorder='little', signed=False)
+                rta_type = int.from_bytes(nlmsg[rtattr_indx + 2 : rtattr_indx + 4], byteorder='little', signed=False)
+                if rta_type == IFLA_ADDRESS:
+                    data = nlmsg[rtattr_indx + RTATTR_SZ : rtattr_indx + rta_len]
+                    if _data_matches_ip(ifa_family, data, src_addr):
+                        return socket.if_indextoname(ifa_index)
+
+                rta_len = (rta_len + 3) & ~3  # Round up to multiple of 4
+                rtattr_indx += rta_len  # Move to next rtattr
+
+            nlmsg_idx += nlmsg_len  # Move to next Netlink message
+
+    return ''
+
+
+# ******************************************************************************
+def get_interface(src_addr):
+    '''Get interface for given source address
+    @param src_addr: The source address
+    @type src_addr: str
+    '''
+    if not src_addr:
+        return ''
+
+    src_addr = src_addr.split('%')[0]  # remove scope-id (if any)
+    src_addr = get_ipaddress_obj(src_addr)
+    return '' if src_addr is None else iface_of(src_addr)
+
+
+# ******************************************************************************
+def remove_invalid_addresses(controllers: list):
+    '''@brief Remove controllers with invalid addresses from the list of controllers.
+    @param controllers: List of TIDs
+    '''
+    service_conf = conf.SvcConf()
+    valid_controllers = list()
+    for controller in controllers:
+        if controller.transport in ('tcp', 'rdma'):
+            # Let's make sure that traddr is
+            # syntactically a valid IPv4 or IPv6 address.
+            ip = get_ipaddress_obj(controller.traddr)
+            if ip is None:
+                logging.warning('%s IP address is not valid', controller)
+                continue
+
+            # Let's make sure the address family is enabled.
+            if ip.version not in service_conf.ip_family:
+                logging.debug(
+                    '%s ignored because IPv%s is disabled in %s',
+                    controller,
+                    ip.version,
+                    service_conf.conf_file,
+                )
+                continue
+
+            valid_controllers.append(controller)
+
+        elif controller.transport in ('fc', 'loop'):
+            # At some point, need to validate FC addresses as well...
+            valid_controllers.append(controller)
+
+        else:
+            logging.warning('Invalid transport %s', controller.transport)
+
+    return valid_controllers
diff --git a/staslib/log.py b/staslib/log.py
new file mode 100644
index 0000000..9622e98
--- /dev/null
+++ b/staslib/log.py
@@ -0,0 +1,53 @@
+# Copyright (c) 2022, Dell Inc. or its subsidiaries.  All rights reserved.
+# SPDX-License-Identifier: Apache-2.0
+# See the LICENSE file for details.
+#
+# This file is part of NVMe STorage Appliance Services (nvme-stas).
+#
+# Authors: Martin Belanger <Martin.Belanger@dell.com>
+#
+'''nvme-stas logging module'''
+
+import sys
+import logging
+from staslib import defs
+
+
+def init(syslog: bool):
+    '''Init log module
+    @param syslog: True to send messages to the syslog,
+                   False to send messages to stdout.
+    '''
+    log = logging.getLogger()
+    log.propagate = False
+
+    if syslog:
+        try:
+            # Try journal logger first
+            import systemd.journal  # pylint: disable=import-outside-toplevel
+
+            handler = systemd.journal.JournalHandler(SYSLOG_IDENTIFIER=defs.PROG_NAME)
+        except ModuleNotFoundError:
+            # Go back to standard syslog handler
+            from logging.handlers import SysLogHandler  # pylint: disable=import-outside-toplevel
+
+            handler = SysLogHandler(address="/dev/log")
+            handler.setFormatter(logging.Formatter(f'{defs.PROG_NAME}: %(message)s'))
+    else:
+        # Log to stdout
+        handler = logging.StreamHandler(stream=sys.stdout)
+
+    log.addHandler(handler)
+    log.setLevel(logging.INFO if syslog else logging.DEBUG)
+
+
+def level() -> str:
+    '''@brief return current log level'''
+    logger = logging.getLogger()
+    return str(logging.getLevelName(logger.getEffectiveLevel()))
+
+
+def set_level_from_tron(tron):
+    '''Set log level based on TRON'''
+    logger = logging.getLogger()
+    logger.setLevel(logging.DEBUG if tron else logging.INFO)
diff --git a/staslib/meson.build b/staslib/meson.build
new file mode 100644
index 0000000..eb006f0
--- /dev/null
+++ b/staslib/meson.build
@@ -0,0 +1,60 @@
+# Copyright (c) 2021, Dell Inc. or its subsidiaries.  All rights reserved.
+# SPDX-License-Identifier: Apache-2.0
+# See the LICENSE file for details.
+#
+# This file is part of NVMe STorage Appliance Services (nvme-stas).
+#
+# Authors: Martin Belanger <Martin.Belanger@dell.com>
+#
+
+files_to_configure = [ 'defs.py', '__init__.py', 'stafd.idl', 'stacd.idl' ]
+configured_files = []
+foreach file : files_to_configure
+    configured_files += configure_file(
+        input: file,
+        output: file,
+        configuration: conf
+    )
+endforeach
+
+files_to_copy = [
+    'avahi.py',
+    'conf.py',
+    'ctrl.py',
+    'gutil.py',
+    'iputil.py',
+    'log.py',
+    'service.py',
+    'singleton.py',
+    'stas.py',
+    'timeparse.py',
+    'trid.py',
+    'udev.py',
+    'version.py'
+]
+copied_files = []
+foreach file : files_to_copy
+    copied_files += configure_file(
+        input: file,
+        output: file,
+        copy: true,
+    )
+endforeach
+
+files_to_install = copied_files + configured_files
+python3.install_sources(
+    files_to_install,
+    pure: true,
+    subdir: 'staslib',
+)
+
+#===============================================================================
+# Make a list of modules to lint
+skip = ['stafd.idl', 'stacd.idl']
+foreach file: files_to_install
+    fname = fs.name('@0@'.format(file))
+    if fname not in skip
+        modules_to_lint += file
+    endif
+endforeach
+
diff --git a/staslib/service.py b/staslib/service.py
new file mode 100644
index 0000000..ce4769d
--- /dev/null
+++ b/staslib/service.py
@@ -0,0 +1,878 @@
+# Copyright (c) 2022, Dell Inc. or its subsidiaries.  All rights reserved.
+# SPDX-License-Identifier: Apache-2.0
+# See the LICENSE file for details.
+#
+# This file is part of NVMe STorage Appliance Services (nvme-stas).
+#
+# Authors: Martin Belanger <Martin.Belanger@dell.com>
+#
+'''This module defines the base Service object from
+which the Staf and the Stac objects are derived.'''
+
+import json
+import logging
+import pathlib
+import subprocess
+from itertools import filterfalse
+import dasbus.error
+import dasbus.client.observer
+import dasbus.client.proxy
+
+from gi.repository import GLib
+from systemd.daemon import notify as sd_notify
+from staslib import avahi, conf, ctrl, defs, gutil, iputil, stas, timeparse, trid, udev
+
+
+# ******************************************************************************
+class CtrlTerminator:
+    '''The Controller Terminator is used to gracefully disconnect from
+    controllers. All communications with controllers is handled by the kernel.
+    Once we make a request to the kernel to perform an operation (e.g. connect),
+    we have to wait for it to complete before requesting another operation. This
+    is particularly important when we want to disconnect from a controller while
+    there are pending operations, especially a pending connect.
+
+    The "connect" operation is especially unpredictable because all connect
+    requests are made through the blocking interface "/dev/nvme-fabrics". This
+    means that once a "connect" operation has been submitted, and depending on
+    how many connect requests are made concurrently, it can take several seconds
+    for a connect to be processed by the kernel.
+
+    While connect or other operations are being performed, it is possible
+    that a disconnect may be requested (e.g. someone or something changes the
+    configuration to remove a controller). Because it is not possible to
+    terminate a pending operation request, we have to wait for it to complete
+    before we can issue a disconnect. Failure to do that will result in
+    operations being performed by the kernel in reverse order. For example,
+    a disconnect may be executed before a pending connect has had a chance to
+    complete. And this will result in controllers that are supposed to be
+    disconnected to be connected without nvme-stas knowing about it.
+
+    The Controller Terminator is used when we need to disconnect from a
+    controller. It will make sure that there are no pending operations before
+    issuing a disconnect.
+    '''
+
+    DISPOSAL_AUDIT_PERIOD_SEC = 30
+
+    def __init__(self):
+        self._udev = udev.UDEV
+        self._controllers = list()  # The list of controllers to dispose of.
+        self._audit_tmr = gutil.GTimer(self.DISPOSAL_AUDIT_PERIOD_SEC, self._on_disposal_check)
+
+    def dispose(self, controller: ctrl.Controller, on_controller_removed_cb, keep_connection: bool):
+        '''Invoked by a service (stafd or stacd) to dispose of a controller'''
+        if controller.all_ops_completed():
+            logging.debug(
+                'CtrlTerminator.dispose()           - %s | %s: Invoke disconnect()', controller.tid, controller.device
+            )
+            controller.disconnect(on_controller_removed_cb, keep_connection)
+        else:
+            logging.debug(
+                'CtrlTerminator.dispose()           - %s | %s: Add controller to garbage disposal',
+                controller.tid,
+                controller.device,
+            )
+            self._controllers.append((controller, keep_connection, on_controller_removed_cb, controller.tid))
+
+            self._udev.register_for_action_events('add', self._on_kernel_events)
+            self._udev.register_for_action_events('remove', self._on_kernel_events)
+
+            if self._audit_tmr.time_remaining() == 0:
+                self._audit_tmr.start()
+
+    def pending_disposal(self, tid):
+        '''Check whether @tid is pending disposal'''
+        for controller in self._controllers:
+            if controller.tid == tid:
+                return True
+        return False
+
+    def info(self):
+        '''@brief Get info about this object (used for debug)'''
+        info = {
+            'terminator.audit timer': str(self._audit_tmr),
+        }
+        for controller, _, _, tid in self._controllers:
+            info[f'terminator.controller.{tid}'] = str(controller.info())
+        return info
+
+    def kill(self):
+        '''Stop Controller Terminator and release resources.'''
+        self._audit_tmr.stop()
+        self._audit_tmr = None
+
+        if self._udev:
+            self._udev.unregister_for_action_events('add', self._on_kernel_events)
+            self._udev.unregister_for_action_events('remove', self._on_kernel_events)
+            self._udev = None
+
+        for controller, keep_connection, on_controller_removed_cb, _ in self._controllers:
+            controller.disconnect(on_controller_removed_cb, keep_connection)
+
+        self._controllers.clear()
+
+    def _on_kernel_events(self, udev_obj):
+        logging.debug('CtrlTerminator._on_kernel_events() - %s event received', udev_obj.action)
+        self._disposal_check()
+
+    def _on_disposal_check(self, *_user_data):
+        logging.debug('CtrlTerminator._on_disposal_check()- Periodic audit')
+        return GLib.SOURCE_REMOVE if self._disposal_check() else GLib.SOURCE_CONTINUE
+
+    @staticmethod
+    def _keep_or_terminate(args):
+        '''Return False if controller is to be kept. True if controller
+        was terminated and can be removed from the list.'''
+        controller, keep_connection, on_controller_removed_cb, tid = args
+        if controller.all_ops_completed():
+            logging.debug(
+                'CtrlTerminator._keep_or_terminate()- %s | %s: Disconnecting controller',
+                tid,
+                controller.device,
+            )
+            controller.disconnect(on_controller_removed_cb, keep_connection)
+            return True
+
+        return False
+
+    def _disposal_check(self):
+        # Iterate over the list, terminating (disconnecting) those controllers
+        # that have no pending operations, and remove those controllers from the
+        # list (only keep controllers that still have operations pending).
+        self._controllers[:] = filterfalse(self._keep_or_terminate, self._controllers)
+        disposal_complete = len(self._controllers) == 0
+
+        if disposal_complete:
+            logging.debug('CtrlTerminator._disposal_check()   - Disposal complete')
+            self._audit_tmr.stop()
+            self._udev.unregister_for_action_events('add', self._on_kernel_events)
+            self._udev.unregister_for_action_events('remove', self._on_kernel_events)
+        else:
+            self._audit_tmr.start()  # Restart timer
+
+        return disposal_complete
+
+
+# ******************************************************************************
+class Service(stas.ServiceABC):
+    '''@brief Base class used to manage a STorage Appliance Service'''
+
+    def __init__(self, args, default_conf, reload_hdlr):
+        self._udev = udev.UDEV
+        self._terminator = CtrlTerminator()
+
+        super().__init__(args, default_conf, reload_hdlr)
+
+    def _release_resources(self):
+        logging.debug('Service._release_resources()')
+        super()._release_resources()
+
+        if self._terminator:
+            self._terminator.kill()
+
+        self._udev = None
+        self._terminator = None
+
+    def _disconnect_all(self):
+        '''Tell all controller objects to disconnect'''
+        keep_connections = self._keep_connections_on_exit()
+        controllers = self._controllers.values()
+        logging.debug(
+            'Service._stop_hdlr()               - Controller count = %s, keep_connections = %s',
+            len(controllers),
+            keep_connections,
+        )
+        for controller in controllers:
+            self._terminator.dispose(controller, self._on_final_disconnect, keep_connections)
+
+    def info(self) -> dict:
+        '''@brief Get the status info for this object (used for debug)'''
+        info = super().info()
+        if self._terminator:
+            info.update(self._terminator.info())
+        return info
+
+    @stas.ServiceABC.tron.setter
+    def tron(self, value):
+        '''@brief Set Trace ON property'''
+        super(__class__, self.__class__).tron.__set__(self, value)
+
+
+# ******************************************************************************
+class Stac(Service):
+    '''STorage Appliance Connector (STAC)'''
+
+    CONF_STABILITY_LONG_SOAK_TIME_SEC = 10  # pylint: disable=invalid-name
+    ADD_EVENT_SOAK_TIME_SEC = 1
+
+    def __init__(self, args, dbus):
+        default_conf = {
+            ('Global', 'tron'): False,
+            ('Global', 'hdr-digest'): False,
+            ('Global', 'data-digest'): False,
+            ('Global', 'kato'): None,  # None to let the driver decide the default
+            ('Global', 'nr-io-queues'): None,  # None to let the driver decide the default
+            ('Global', 'nr-write-queues'): None,  # None to let the driver decide the default
+            ('Global', 'nr-poll-queues'): None,  # None to let the driver decide the default
+            ('Global', 'queue-size'): None,  # None to let the driver decide the default
+            ('Global', 'reconnect-delay'): None,  # None to let the driver decide the default
+            ('Global', 'ctrl-loss-tmo'): None,  # None to let the driver decide the default
+            ('Global', 'disable-sqflow'): None,  # None to let the driver decide the default
+            ('Global', 'ignore-iface'): False,
+            ('Global', 'ip-family'): (4, 6),
+            ('Controllers', 'controller'): list(),
+            ('Controllers', 'exclude'): list(),
+            ('I/O controller connection management', 'disconnect-scope'): 'only-stas-connections',
+            ('I/O controller connection management', 'disconnect-trtypes'): ['tcp'],
+            ('I/O controller connection management', 'connect-attempts-on-ncc'): 0,
+        }
+
+        super().__init__(args, default_conf, self._reload_hdlr)
+
+        self._add_event_soak_tmr = gutil.GTimer(self.ADD_EVENT_SOAK_TIME_SEC, self._on_add_event_soaked)
+
+        self._config_connections_audit()
+
+        # Create the D-Bus instance.
+        self._config_dbus(dbus, defs.STACD_DBUS_NAME, defs.STACD_DBUS_PATH)
+
+        # Connect to STAF D-Bus interface
+        self._staf = None
+        self._staf_watcher = dasbus.client.observer.DBusObserver(self._sysbus, defs.STAFD_DBUS_NAME)
+        self._staf_watcher.service_available.connect(self._connect_to_staf)
+        self._staf_watcher.service_unavailable.connect(self._disconnect_from_staf)
+        self._staf_watcher.connect_once_available()
+
+    def _release_resources(self):
+        logging.debug('Stac._release_resources()')
+
+        if self._add_event_soak_tmr:
+            self._add_event_soak_tmr.kill()
+
+        if self._udev:
+            self._udev.unregister_for_action_events('add', self._on_add_event)
+
+        self._destroy_staf_comlink(self._staf_watcher)
+        if self._staf_watcher is not None:
+            self._staf_watcher.disconnect()
+
+        super()._release_resources()
+
+        self._staf = None
+        self._staf_watcher = None
+        self._add_event_soak_tmr = None
+
+    def _dump_last_known_config(self, controllers):
+        config = list(controllers.keys())
+        logging.debug('Stac._dump_last_known_config()     - IOC count = %s', len(config))
+        self._write_lkc(config)
+
+    def _load_last_known_config(self):
+        config = self._read_lkc() or list()
+        logging.debug('Stac._load_last_known_config()     - IOC count = %s', len(config))
+
+        controllers = {}
+        for tid in config:
+            # Only create Ioc objects if there is already a connection in the kernel
+            # First, regenerate the TID (in case of soft. upgrade and TID object
+            # has changed internally)
+            tid = trid.TID(tid.as_dict())
+            if udev.UDEV.find_nvme_ioc_device(tid) is not None:
+                controllers[tid] = ctrl.Ioc(self, tid)
+
+        return controllers
+
+    def _audit_all_connections(self, tids):
+        '''A host should only connect to I/O controllers that have been zoned
+        for that host or a manual "controller" entry exists in stacd.conf.
+        A host should disconnect from an I/O controller when that I/O controller
+        is removed from the zone or a "controller" entry is manually removed
+        from stacd.conf. stacd will audit connections if "disconnect-scope=
+        all-connections-matching-disconnect-trtypes". stacd will delete any
+        connection that is not supposed to exist.
+        '''
+        logging.debug('Stac._audit_all_connections()      - tids = %s', tids)
+        num_controllers = len(self._controllers)
+        for tid in tids:
+            if tid not in self._controllers and not self._terminator.pending_disposal(tid):
+                self._controllers[tid] = ctrl.Ioc(self, tid)
+
+        if num_controllers != len(self._controllers):
+            self._cfg_soak_tmr.start(self.CONF_STABILITY_SOAK_TIME_SEC)
+
+    def _on_add_event(self, udev_obj):
+        '''@brief This function is called when a "add" event is received from
+        the kernel for an NVMe device. This is used to trigger an audit and make
+        sure that the connection to an I/O controller is allowed.
+
+        WARNING: There is a race condition with the "add" event from the kernel.
+        The kernel sends the "add" event a bit early and the sysfs attributes
+        associated with the nvme object are not always fully initialized.
+        To workaround this problem we use a soaking timer to give time for the
+        sysfs attributes to stabilize.
+        '''
+        logging.debug('Stac._on_add_event(()              - Received "add" event: %s', udev_obj.sys_name)
+        self._add_event_soak_tmr.start()
+
+    def _on_add_event_soaked(self):
+        '''@brief After the add event has been soaking for ADD_EVENT_SOAK_TIME_SEC
+        seconds, we can audit the connections.
+        '''
+        if self._alive():
+            svc_conf = conf.SvcConf()
+            if svc_conf.disconnect_scope == 'all-connections-matching-disconnect-trtypes':
+                self._audit_all_connections(self._udev.get_nvme_ioc_tids(svc_conf.disconnect_trtypes))
+        return GLib.SOURCE_REMOVE
+
+    def _config_connections_audit(self):
+        '''This function checks the "disconnect_scope" parameter to determine
+        whether audits should be performed. Audits are enabled when
+        "disconnect_scope == all-connections-matching-disconnect-trtypes".
+        '''
+        svc_conf = conf.SvcConf()
+        if svc_conf.disconnect_scope == 'all-connections-matching-disconnect-trtypes':
+            if not self._udev.is_action_cback_registered('add', self._on_add_event):
+                self._udev.register_for_action_events('add', self._on_add_event)
+                self._audit_all_connections(self._udev.get_nvme_ioc_tids(svc_conf.disconnect_trtypes))
+        else:
+            self._udev.unregister_for_action_events('add', self._on_add_event)
+
+    def _keep_connections_on_exit(self):
+        '''@brief Determine whether connections should remain when the
+        process exits.
+        '''
+        return True
+
+    def _reload_hdlr(self):
+        '''@brief Reload configuration file. This is triggered by the SIGHUP
+        signal, which can be sent with "systemctl reload stacd".
+        '''
+        if not self._alive():
+            return GLib.SOURCE_REMOVE
+
+        sd_notify('RELOADING=1')
+        service_cnf = conf.SvcConf()
+        service_cnf.reload()
+        self.tron = service_cnf.tron
+        self._config_connections_audit()
+        self._cfg_soak_tmr.start(self.CONF_STABILITY_SOAK_TIME_SEC)
+
+        for controller in self._controllers.values():
+            controller.reload_hdlr()
+
+        sd_notify('READY=1')
+        return GLib.SOURCE_CONTINUE
+
+    def _get_log_pages_from_stafd(self):
+        if self._staf:
+            try:
+                return json.loads(self._staf.get_all_log_pages(True))
+            except dasbus.error.DBusError:
+                pass
+
+        return list()
+
+    def _config_ctrls_finish(self, configured_ctrl_list: list):  # pylint: disable=too-many-locals
+        '''@param configured_ctrl_list: list of TIDs'''
+        # This is a callback function, which may be called after the service
+        # has been signalled to stop. So let's make sure the service is still
+        # alive and well before continuing.
+        if not self._alive():
+            logging.debug('Stac._config_ctrls_finish()        - Exiting because service is no longer alive')
+            return
+
+        # Eliminate invalid entries from stacd.conf "controller list".
+        configured_ctrl_list = [
+            tid for tid in configured_ctrl_list if '' not in (tid.transport, tid.traddr, tid.trsvcid, tid.subsysnqn)
+        ]
+
+        logging.debug('Stac._config_ctrls_finish()        - configured_ctrl_list = %s', configured_ctrl_list)
+
+        discovered_ctrls = dict()
+        for staf_data in self._get_log_pages_from_stafd():
+            host_traddr = staf_data['discovery-controller']['host-traddr']
+            host_iface = staf_data['discovery-controller']['host-iface']
+            for dlpe in staf_data['log-pages']:
+                if dlpe.get('subtype') == 'nvme':  # eliminate discovery controllers
+                    tid = stas.tid_from_dlpe(dlpe, host_traddr, host_iface)
+                    discovered_ctrls[tid] = dlpe
+
+        discovered_ctrl_list = list(discovered_ctrls.keys())
+        logging.debug('Stac._config_ctrls_finish()        - discovered_ctrl_list = %s', discovered_ctrl_list)
+
+        controllers = stas.remove_excluded(configured_ctrl_list + discovered_ctrl_list)
+        controllers = iputil.remove_invalid_addresses(controllers)
+
+        new_controller_tids = set(controllers)
+        cur_controller_tids = set(self._controllers.keys())
+        controllers_to_add = new_controller_tids - cur_controller_tids
+        controllers_to_del = cur_controller_tids - new_controller_tids
+
+        logging.debug('Stac._config_ctrls_finish()        - controllers_to_add   = %s', list(controllers_to_add))
+        logging.debug('Stac._config_ctrls_finish()        - controllers_to_del   = %s', list(controllers_to_del))
+
+        svc_conf = conf.SvcConf()
+        no_disconnect = svc_conf.disconnect_scope == 'no-disconnect'
+        match_trtypes = svc_conf.disconnect_scope == 'all-connections-matching-disconnect-trtypes'
+        logging.debug(
+            'Stac._config_ctrls_finish()        - no_disconnect=%s, match_trtypes=%s, svc_conf.disconnect_trtypes=%s',
+            no_disconnect,
+            match_trtypes,
+            svc_conf.disconnect_trtypes,
+        )
+        for tid in controllers_to_del:
+            controller = self._controllers.pop(tid, None)
+            if controller is not None:
+                keep_connection = no_disconnect or (match_trtypes and tid.transport not in svc_conf.disconnect_trtypes)
+                self._terminator.dispose(controller, self.remove_controller, keep_connection)
+
+        for tid in controllers_to_add:
+            self._controllers[tid] = ctrl.Ioc(self, tid)
+
+        for tid, controller in self._controllers.items():
+            if tid in discovered_ctrls:
+                dlpe = discovered_ctrls[tid]
+                controller.update_dlpe(dlpe)
+
+        self._dump_last_known_config(self._controllers)
+
+    def _connect_to_staf(self, _):
+        '''@brief Hook up DBus signal handlers for signals from stafd.'''
+        if not self._alive():
+            return
+
+        try:
+            self._staf = self._sysbus.get_proxy(defs.STAFD_DBUS_NAME, defs.STAFD_DBUS_PATH)
+            self._staf.log_pages_changed.connect(self._log_pages_changed)
+            self._staf.dc_removed.connect(self._dc_removed)
+            self._cfg_soak_tmr.start()
+
+            # Make sure timer is set back to its normal value.
+            self._cfg_soak_tmr.set_timeout(self.CONF_STABILITY_SOAK_TIME_SEC)
+            logging.debug('Stac._connect_to_staf()            - Connected to staf')
+        except dasbus.error.DBusError:
+            logging.error('Failed to connect to staf')
+
+    def _destroy_staf_comlink(self, watcher):  # pylint: disable=unused-argument
+        if self._staf:
+            self._staf.log_pages_changed.disconnect(self._log_pages_changed)
+            self._staf.dc_removed.disconnect(self._dc_removed)
+            dasbus.client.proxy.disconnect_proxy(self._staf)
+            self._staf = None
+
+    def _disconnect_from_staf(self, watcher):
+        self._destroy_staf_comlink(watcher)
+
+        # When we lose connectivity with stafd, the most logical explanation
+        # is that stafd restarted. In that case, it may take some time for stafd
+        # to re-populate its log pages cache. So let's give stafd plenty of time
+        # to update its log pages cache and send log pages change notifications
+        # before triggering a stacd re-config. We do this by momentarily
+        # increasing the config soak timer to a longer period.
+        if self._cfg_soak_tmr:
+            self._cfg_soak_tmr.set_timeout(self.CONF_STABILITY_LONG_SOAK_TIME_SEC)
+
+        logging.debug('Stac._disconnect_from_staf()       - Disconnected from staf')
+
+    def _log_pages_changed(  # pylint: disable=too-many-arguments
+        self, transport, traddr, trsvcid, host_traddr, host_iface, subsysnqn, device
+    ):
+        if not self._alive():
+            return
+
+        logging.debug(
+            'Stac._log_pages_changed()          - transport=%s, traddr=%s, trsvcid=%s, host_traddr=%s, host_iface=%s, subsysnqn=%s, device=%s',
+            transport,
+            traddr,
+            trsvcid,
+            host_traddr,
+            host_iface,
+            subsysnqn,
+            device,
+        )
+        if self._cfg_soak_tmr:
+            self._cfg_soak_tmr.start(self.CONF_STABILITY_SOAK_TIME_SEC)
+
+    def _dc_removed(self):
+        if not self._alive():
+            return
+
+        logging.debug('Stac._dc_removed()')
+        if self._cfg_soak_tmr:
+            self._cfg_soak_tmr.start(self.CONF_STABILITY_SOAK_TIME_SEC)
+
+
+# ******************************************************************************
+# Only keep legacy FC rule (not even sure this is still in use today, but just to be safe).
+UDEV_RULE_OVERRIDE = r'''
+ACTION=="change", SUBSYSTEM=="fc", ENV{FC_EVENT}=="nvmediscovery", \
+  ENV{NVMEFC_HOST_TRADDR}=="*",  ENV{NVMEFC_TRADDR}=="*", \
+  RUN+="%s --no-block start nvmf-connect@--transport=fc\t--traddr=$env{NVMEFC_TRADDR}\t--trsvcid=none\t--host-traddr=$env{NVMEFC_HOST_TRADDR}.service"
+'''
+
+
+def _udev_rule_ctrl(suppress):
+    '''@brief We override the standard udev rule installed by nvme-cli, i.e.
+    '/usr/lib/udev/rules.d/70-nvmf-autoconnect.rules', with a copy into
+    /run/udev/rules.d. The goal is to suppress the udev rule that controls TCP
+    connections to I/O controllers. This is to avoid race conditions between
+    stacd and udevd. This is configurable. See "udev-rule" in stacd.conf
+    for details.
+
+    @param enable: When True, override nvme-cli's udev rule and prevent TCP I/O
+    Controller connections by nvme-cli. When False, allow nvme-cli's udev rule
+    to make TCP I/O connections.
+    @type enable: bool
+    '''
+    udev_rule_file = pathlib.Path('/run/udev/rules.d', '70-nvmf-autoconnect.rules')
+    if suppress:
+        if not udev_rule_file.exists():
+            pathlib.Path('/run/udev/rules.d').mkdir(parents=True, exist_ok=True)
+            text = UDEV_RULE_OVERRIDE % (defs.SYSTEMCTL)
+            udev_rule_file.write_text(text)  # pylint: disable=unspecified-encoding
+    else:
+        try:
+            udev_rule_file.unlink()
+        except FileNotFoundError:
+            pass
+
+
+def _is_dlp_changed_aen(udev_obj):
+    '''Check whether we received a Change of Discovery Log Page AEN'''
+    nvme_aen = udev_obj.get('NVME_AEN')
+    if not isinstance(nvme_aen, str):
+        return False
+
+    aen = int(nvme_aen, 16)
+    if aen != ctrl.DLP_CHANGED:
+        return False
+
+    logging.info(
+        '%s - Received AEN: Change of Discovery Log Page (%s)',
+        udev_obj.sys_name,
+        nvme_aen,
+    )
+    return True
+
+
+def _event_matches(udev_obj, nvme_events):
+    '''Check whether we received an NVMe Event matching
+    one of the events listed in @nvme_events'''
+    nvme_event = udev_obj.get('NVME_EVENT')
+    if nvme_event not in nvme_events:
+        return False
+
+    logging.info('%s - Received "%s" event', udev_obj.sys_name, nvme_event)
+    return True
+
+
+# ******************************************************************************
+class Staf(Service):
+    '''STorage Appliance Finder (STAF)'''
+
+    def __init__(self, args, dbus):
+        default_conf = {
+            ('Global', 'tron'): False,
+            ('Global', 'hdr-digest'): False,
+            ('Global', 'data-digest'): False,
+            ('Global', 'kato'): 30,
+            ('Global', 'queue-size'): None,  # None to let the driver decide the default
+            ('Global', 'reconnect-delay'): None,  # None to let the driver decide the default
+            ('Global', 'ctrl-loss-tmo'): None,  # None to let the driver decide the default
+            ('Global', 'disable-sqflow'): None,  # None to let the driver decide the default
+            ('Global', 'persistent-connections'): False,  # Deprecated
+            ('Discovery controller connection management', 'persistent-connections'): True,
+            ('Discovery controller connection management', 'zeroconf-connections-persistence'): timeparse.timeparse(
+                '72hours'
+            ),
+            ('Global', 'ignore-iface'): False,
+            ('Global', 'ip-family'): (4, 6),
+            ('Global', 'pleo'): True,
+            ('Service Discovery', 'zeroconf'): True,
+            ('Controllers', 'controller'): list(),
+            ('Controllers', 'exclude'): list(),
+        }
+
+        super().__init__(args, default_conf, self._reload_hdlr)
+
+        self._avahi = avahi.Avahi(self._sysbus, self._avahi_change)
+        self._avahi.config_stypes(conf.SvcConf().stypes)
+
+        # Create the D-Bus instance.
+        self._config_dbus(dbus, defs.STAFD_DBUS_NAME, defs.STAFD_DBUS_PATH)
+
+        self._udev.register_for_action_events('change', self._nvme_cli_interop)
+        _udev_rule_ctrl(True)
+
+    def info(self) -> dict:
+        '''@brief Get the status info for this object (used for debug)'''
+        info = super().info()
+        info['avahi'] = self._avahi.info()
+        return info
+
+    def _release_resources(self):
+        logging.debug('Staf._release_resources()')
+        if self._udev:
+            self._udev.unregister_for_action_events('change', self._nvme_cli_interop)
+
+        super()._release_resources()
+
+        _udev_rule_ctrl(False)
+        if self._avahi:
+            self._avahi.kill()
+            self._avahi = None
+
+    def _dump_last_known_config(self, controllers):
+        config = {tid: {'log_pages': dc.log_pages(), 'origin': dc.origin} for tid, dc in controllers.items()}
+        logging.debug('Staf._dump_last_known_config()     - DC count = %s', len(config))
+        self._write_lkc(config)
+
+    def _load_last_known_config(self):
+        config = self._read_lkc() or dict()
+        logging.debug('Staf._load_last_known_config()     - DC count = %s', len(config))
+
+        controllers = {}
+        for tid, data in config.items():
+            if isinstance(data, dict):
+                log_pages = data.get('log_pages')
+                origin = data.get('origin')
+            else:
+                log_pages = data
+                origin = None
+
+            # Regenerate the TID (in case of soft. upgrade and TID object
+            # has changed internally)
+            tid = trid.TID(tid.as_dict())
+            controllers[tid] = ctrl.Dc(self, tid, log_pages, origin)
+
+        return controllers
+
+    def _keep_connections_on_exit(self):
+        '''@brief Determine whether connections should remain when the
+        process exits.
+        '''
+        return conf.SvcConf().persistent_connections
+
+    def _reload_hdlr(self):
+        '''@brief Reload configuration file. This is triggered by the SIGHUP
+        signal, which can be sent with "systemctl reload stafd".
+        '''
+        if not self._alive():
+            return GLib.SOURCE_REMOVE
+
+        sd_notify('RELOADING=1')
+        service_cnf = conf.SvcConf()
+        service_cnf.reload()
+        self.tron = service_cnf.tron
+        self._avahi.kick_start()  # Make sure Avahi is running
+        self._avahi.config_stypes(service_cnf.stypes)
+        self._cfg_soak_tmr.start()
+
+        for controller in self._controllers.values():
+            controller.reload_hdlr()
+
+        sd_notify('READY=1')
+        return GLib.SOURCE_CONTINUE
+
+    def is_avahi_reported(self, tid):
+        '''@brief Return whether @tid is being reported by the Avahi daemon.
+        @return: True if the Avahi daemon is reporting it, False otherwise.
+        '''
+        for cid in self._avahi.get_controllers():
+            if trid.TID(cid) == tid:
+                return True
+        return False
+
+    def log_pages_changed(self, controller, device):
+        '''@brief Function invoked when a controller's cached log pages
+        have changed. This will emit a D-Bus signal to inform
+        other applications that the cached log pages have changed.
+        '''
+        self._dbus_iface.log_pages_changed.emit(
+            controller.tid.transport,
+            controller.tid.traddr,
+            controller.tid.trsvcid,
+            controller.tid.host_traddr,
+            controller.tid.host_iface,
+            controller.tid.subsysnqn,
+            device,
+        )
+
+    def dc_removed(self):
+        '''@brief Function invoked when a controller's cached log pages
+        have changed. This will emit a D-Bus signal to inform
+        other applications that the cached log pages have changed.
+        '''
+        self._dbus_iface.dc_removed.emit()
+
+    def _referrals(self) -> list:
+        return [
+            stas.tid_from_dlpe(dlpe, controller.tid.host_traddr, controller.tid.host_iface)
+            for controller in self.get_controllers()
+            for dlpe in controller.referrals()
+        ]
+
+    def _config_ctrls_finish(self, configured_ctrl_list: list):
+        '''@brief Finish discovery controllers configuration after
+        hostnames (if any) have been resolved. All the logic associated
+        with discovery controller creation/deletion is found here.  To
+        avoid calling this algorith repetitively for each and every events,
+        it is called after a soaking period controlled by self._cfg_soak_tmr.
+
+        @param configured_ctrl_list: List of TIDs configured in stafd.conf with
+        all hostnames resolved to their corresponding IP addresses.
+        '''
+        # This is a callback function, which may be called after the service
+        # has been signalled to stop. So let's make sure the service is still
+        # alive and well before continuing.
+        if not self._alive():
+            logging.debug('Staf._config_ctrls_finish()        - Exiting because service is no longer alive')
+            return
+
+        # Eliminate invalid entries from stafd.conf "controller list".
+        controllers = list()
+        for tid in configured_ctrl_list:
+            if '' in (tid.transport, tid.traddr, tid.trsvcid):
+                continue
+            if not tid.subsysnqn:
+                cid = tid.as_dict()
+                cid['subsysnqn'] = defs.WELL_KNOWN_DISC_NQN
+                controllers.append(trid.TID(cid))
+            else:
+                controllers.append(tid)
+        configured_ctrl_list = controllers
+
+        # Get the Avahi-discovered list and the referrals.
+        discovered_ctrl_list = [trid.TID(cid) for cid in self._avahi.get_controllers()]
+        referral_ctrl_list = self._referrals()
+        logging.debug('Staf._config_ctrls_finish()        - configured_ctrl_list = %s', configured_ctrl_list)
+        logging.debug('Staf._config_ctrls_finish()        - discovered_ctrl_list = %s', discovered_ctrl_list)
+        logging.debug('Staf._config_ctrls_finish()        - referral_ctrl_list   = %s', referral_ctrl_list)
+
+        all_ctrls = configured_ctrl_list + discovered_ctrl_list + referral_ctrl_list
+        controllers = stas.remove_excluded(all_ctrls)
+        controllers = iputil.remove_invalid_addresses(controllers)
+
+        new_controller_tids = set(controllers)
+        cur_controller_tids = set(self._controllers.keys())
+        controllers_to_add = new_controller_tids - cur_controller_tids
+        controllers_to_del = cur_controller_tids - new_controller_tids
+
+        # Make a list list of excluded and invalid controllers
+        must_remove_list = set(all_ctrls) - new_controller_tids
+
+        # Find "discovered" controllers that have not responded
+        # in a while and add them to controllers that must be removed.
+        must_remove_list.update({tid for tid, controller in self._controllers.items() if controller.is_unresponsive()})
+
+        # Do not remove Avahi-discovered DCs from controllers_to_del unless
+        # marked as "must-be-removed" (must_remove_list). This is to account for
+        # the case where mDNS discovery is momentarily disabled (e.g. Avahi
+        # daemon restarts). We don't want to delete connections because of
+        # temporary mDNS impairments. Removal of Avahi-discovered DCs will be
+        # handled differently and only if the connection cannot be established
+        # for a long period of time.
+        logging.debug('Staf._config_ctrls_finish()        - must_remove_list     = %s', list(must_remove_list))
+        controllers_to_del = {
+            tid
+            for tid in controllers_to_del
+            if tid in must_remove_list or self._controllers[tid].origin != 'discovered'
+        }
+
+        logging.debug('Staf._config_ctrls_finish()        - controllers_to_add   = %s', list(controllers_to_add))
+        logging.debug('Staf._config_ctrls_finish()        - controllers_to_del   = %s', list(controllers_to_del))
+
+        # Delete controllers
+        for tid in controllers_to_del:
+            controller = self._controllers.pop(tid, None)
+            if controller is not None:
+                self._terminator.dispose(controller, self.remove_controller, keep_connection=False)
+
+        if len(controllers_to_del) > 0:
+            self.dc_removed()  # Let other apps (e.g. stacd) know that discovery controllers were removed.
+
+        # Add controllers
+        for tid in controllers_to_add:
+            self._controllers[tid] = ctrl.Dc(self, tid)
+
+        # Update "origin" on all DC objects
+        for tid, controller in self._controllers.items():
+            origin = (
+                'configured'
+                if tid in configured_ctrl_list
+                else 'referral'
+                if tid in referral_ctrl_list
+                else 'discovered'
+                if tid in discovered_ctrl_list
+                else None
+            )
+            if origin is not None:
+                controller.origin = origin
+
+        self._dump_last_known_config(self._controllers)
+
+    def _avahi_change(self):
+        if self._alive() and self._cfg_soak_tmr is not None:
+            self._cfg_soak_tmr.start()
+
+    def controller_unresponsive(self, tid):
+        '''@brief Function invoked when a controller becomes unresponsive and
+        needs to be removed.
+        '''
+        if self._alive() and self._cfg_soak_tmr is not None:
+            logging.debug('Staf.controller_unresponsive()     - tid = %s', tid)
+            self._cfg_soak_tmr.start()
+
+    def referrals_changed(self):
+        '''@brief Function invoked when a controller's cached referrals
+        have changed.
+        '''
+        if self._alive() and self._cfg_soak_tmr is not None:
+            logging.debug('Staf.referrals_changed()')
+            self._cfg_soak_tmr.start()
+
+    def _nvme_cli_interop(self, udev_obj):
+        '''Interoperability with nvme-cli:
+        stafd will invoke nvme-cli's connect-all the same way nvme-cli's udev
+        rules would do normally. This is for the case where a user has an hybrid
+        configuration where some controllers are configured through nvme-stas
+        and others through nvme-cli. This is not an optimal configuration. It
+        would be better if everything was configured through nvme-stas, however
+        support for hybrid configuration was requested by users (actually only
+        one user requested this).'''
+
+        # Looking for 'change' events only
+        if udev_obj.action != 'change':
+            return
+
+        # Looking for events from Discovery Controllers only
+        if not udev.Udev.is_dc_device(udev_obj):
+            return
+
+        # Is the controller already being monitored by stafd?
+        for controller in self.get_controllers():
+            if controller.device == udev_obj.sys_name:
+                return
+
+        # Did we receive a Change of DLP AEN or an NVME Event indicating 'connect' or 'rediscover'?
+        if not _is_dlp_changed_aen(udev_obj) and not _event_matches(udev_obj, ('connected', 'rediscover')):
+            return
+
+        # We need to invoke "nvme connect-all" using nvme-cli's nvmf-connect@.service
+        # NOTE: Eventually, we'll be able to drop --host-traddr and --host-iface from
+        # the parameters passed to nvmf-connect@.service. A fix was added to connect-all
+        # to infer these two values from the device used to connect to the DC.
+        # Ref: https://github.com/linux-nvme/nvme-cli/pull/1812
+        cnf = [
+            ('--device', udev_obj.sys_name),
+            ('--host-traddr', udev_obj.properties.get('NVME_HOST_TRADDR', None)),
+            ('--host-iface', udev_obj.properties.get('NVME_HOST_IFACE', None)),
+        ]
+        # Use systemd's escaped syntax (i.e. '=' is replaced by '\x3d', '\t' by '\x09', etc.
+        options = r'\x09'.join(
+            [fr'{option}\x3d{value}' for option, value in cnf if value not in (None, 'none', 'None', '')]
+        )
+        logging.info('Invoking: systemctl start nvmf-connect@%s.service', options)
+        cmd = [defs.SYSTEMCTL, '--quiet', '--no-block', 'start', fr'nvmf-connect@{options}.service']
+        subprocess.run(cmd, check=False)
diff --git a/staslib/singleton.py b/staslib/singleton.py
new file mode 100644
index 0000000..2171186
--- /dev/null
+++ b/staslib/singleton.py
@@ -0,0 +1,23 @@
+# Copyright (c) 2022, Dell Inc. or its subsidiaries.  All rights reserved.
+# SPDX-License-Identifier: Apache-2.0
+# See the LICENSE file for details.
+#
+# This file is part of NVMe STorage Appliance Services (nvme-stas).
+#
+# Authors: Martin Belanger <Martin.Belanger@dell.com>
+#
+'''Implementation of a singleton pattern'''
+
+
+class Singleton(type):
+    '''metaclass implementation of a singleton pattern'''
+
+    _instances = {}
+
+    def __call__(cls, *args, **kwargs):
+        if cls not in cls._instances:
+            # This variable declaration is required to force a
+            # strong reference on the instance.
+            instance = super(Singleton, cls).__call__(*args, **kwargs)
+            cls._instances[cls] = instance
+        return cls._instances[cls]
diff --git a/staslib/stacd.idl b/staslib/stacd.idl
new file mode 100644
index 0000000..efefbbe
--- /dev/null
+++ b/staslib/stacd.idl
@@ -0,0 +1,27 @@
+<node>
+    <interface name="@STACD_DBUS_NAME@.debug">
+        <property name="tron" type="b" access="readwrite"/>
+        <property name="log_level" type="s" access="read"/>
+        <method name="process_info">
+            <arg direction="out" type="s" name="info_json"/>
+        </method>
+        <method name="controller_info">
+            <arg direction="in" type="s" name="transport"/>
+            <arg direction="in" type="s" name="traddr"/>
+            <arg direction="in" type="s" name="trsvcid"/>
+            <arg direction="in" type="s" name="host_traddr"/>
+            <arg direction="in" type="s" name="host_iface"/>
+            <arg direction="in" type="s" name="subsysnqn"/>
+            <arg direction="out" type="s" name="info_json"/>
+        </method>
+    </interface>
+
+    <interface name="@STACD_DBUS_NAME@">
+        <method name="list_controllers">
+            <arg direction="in" type="b" name="detailed"/>
+            <arg direction="out" type="aa{ss}" name="controller_list"/>
+        </method>
+    </interface>
+</node>
+
+
diff --git a/staslib/stafd.idl b/staslib/stafd.idl
new file mode 100644
index 0000000..8c98ffe
--- /dev/null
+++ b/staslib/stafd.idl
@@ -0,0 +1,49 @@
+<node>
+    <interface name="@STAFD_DBUS_NAME@.debug">
+        <property name="tron" type="b" access="readwrite"/>
+        <property name="log_level" type="s" access="read"/>
+        <method name="process_info">
+            <arg direction="out" type="s" name="info_json"/>
+        </method>
+        <method name="controller_info">
+            <arg direction="in" type="s" name="transport"/>
+            <arg direction="in" type="s" name="traddr"/>
+            <arg direction="in" type="s" name="trsvcid"/>
+            <arg direction="in" type="s" name="host_traddr"/>
+            <arg direction="in" type="s" name="host_iface"/>
+            <arg direction="in" type="s" name="subsysnqn"/>
+            <arg direction="out" type="s" name="info_json"/>
+        </method>
+    </interface>
+
+    <interface name="@STAFD_DBUS_NAME@">
+        <method name="list_controllers">
+            <arg direction="in" type="b" name="detailed"/>
+            <arg direction="out" type="aa{ss}" name="controller_list"/>
+        </method>
+        <method name="get_log_pages">
+            <arg direction="in" type="s" name="transport"/>
+            <arg direction="in" type="s" name="traddr"/>
+            <arg direction="in" type="s" name="trsvcid"/>
+            <arg direction="in" type="s" name="host_traddr"/>
+            <arg direction="in" type="s" name="host_iface"/>
+            <arg direction="in" type="s" name="subsysnqn"/>
+            <arg direction="out" type="aa{ss}" name="log_pages"/>
+        </method>
+        <method name="get_all_log_pages">
+            <arg direction="in" type="b" name="detailed"/>
+            <arg direction="out" type="s" name="log_pages_json"/>
+        </method>
+        <signal name="log_pages_changed">
+          <arg direction="out" type="s" name="transport"/>
+          <arg direction="out" type="s" name="traddr"/>
+          <arg direction="out" type="s" name="trsvcid"/>
+          <arg direction="out" type="s" name="host_traddr"/>
+          <arg direction="out" type="s" name="host_iface"/>
+          <arg direction="out" type="s" name="subsysnqn"/>
+          <arg direction="out" type="s" name="device"/>
+        </signal>
+        <signal name="dc_removed"></signal>
+    </interface>
+</node>
+
diff --git a/staslib/stas.py b/staslib/stas.py
new file mode 100644
index 0000000..95afb94
--- /dev/null
+++ b/staslib/stas.py
@@ -0,0 +1,554 @@
+# Copyright (c) 2021, Dell Inc. or its subsidiaries.  All rights reserved.
+# SPDX-License-Identifier: Apache-2.0
+# See the LICENSE file for details.
+#
+# This file is part of NVMe STorage Appliance Services (nvme-stas).
+#
+# Authors: Martin Belanger <Martin.Belanger@dell.com>
+#
+'''Library for staf/stac. You will find here common code for stafd and stacd
+including the Abstract Base Classes (ABC) for Controllers and Services'''
+
+import os
+import sys
+import abc
+import signal
+import pickle
+import logging
+import dasbus.connection
+from gi.repository import Gio, GLib
+from systemd.daemon import notify as sd_notify
+from staslib import conf, defs, gutil, log, trid
+
+try:
+    # Python 3.9 or later
+    # This is the preferred way, but may not be available before Python 3.9
+    from importlib.resources import files
+except ImportError:
+    try:
+        # Pre Python 3.9 backport of importlib.resources (if installed)
+        from importlib_resources import files
+    except ImportError:
+        # Less efficient, but avalable on older versions of Python
+        import pkg_resources
+
+        def load_idl(idl_fname):
+            '''@brief Load D-Bus Interface Description Language File'''
+            try:
+                return pkg_resources.resource_string('staslib', idl_fname).decode()
+            except (FileNotFoundError, AttributeError):
+                pass
+
+            return ''
+
+    else:
+
+        def load_idl(idl_fname):
+            '''@brief Load D-Bus Interface Description Language File'''
+            try:
+                return files('staslib').joinpath(idl_fname).read_text()  # pylint: disable=unspecified-encoding
+            except FileNotFoundError:
+                pass
+
+            return ''
+
+else:
+
+    def load_idl(idl_fname):
+        '''@brief Load D-Bus Interface Description Language File'''
+        try:
+            return files('staslib').joinpath(idl_fname).read_text()  # pylint: disable=unspecified-encoding
+        except FileNotFoundError:
+            pass
+
+        return ''
+
+
+# ******************************************************************************
+def check_if_allowed_to_continue():
+    '''@brief Let's perform some basic checks before going too far. There are
+           a few pre-requisites that need to be met before this program
+           is allowed to proceed:
+
+             1) The program needs to have root privileges
+             2) The nvme-tcp kernel module must be loaded
+
+    @return This function will only return if all conditions listed above
+            are met. Otherwise the program exits.
+    '''
+    # 1) Check root privileges
+    if os.geteuid() != 0:
+        sys.exit(f'Permission denied. You need root privileges to run {defs.PROG_NAME}.')
+
+    # 2) Check that nvme-tcp kernel module is running
+    if not os.path.exists('/dev/nvme-fabrics'):
+        # There's no point going any further if the kernel module hasn't been loaded
+        sys.exit('Fatal error: missing nvme-tcp kernel module')
+
+
+# ******************************************************************************
+def tid_from_dlpe(dlpe, host_traddr, host_iface):
+    '''@brief Take a Discovery Log Page Entry and return a Controller ID as a dict.'''
+    cid = {
+        'transport': dlpe['trtype'],
+        'traddr': dlpe['traddr'],
+        'trsvcid': dlpe['trsvcid'],
+        'host-traddr': host_traddr,
+        'host-iface': host_iface,
+        'subsysnqn': dlpe['subnqn'],
+    }
+    return trid.TID(cid)
+
+
+# ******************************************************************************
+def _excluded(excluded_ctrl_list, controller: dict):
+    '''@brief Check if @controller is excluded.'''
+    for excluded_ctrl in excluded_ctrl_list:
+        test_results = [val == controller.get(key, None) for key, val in excluded_ctrl.items()]
+        if all(test_results):
+            return True
+    return False
+
+
+# ******************************************************************************
+def remove_excluded(controllers: list):
+    '''@brief Remove excluded controllers from the list of controllers.
+    @param controllers: List of TIDs
+    '''
+    excluded_ctrl_list = conf.SvcConf().get_excluded()
+    if excluded_ctrl_list:
+        logging.debug('remove_excluded()                  - excluded_ctrl_list   = %s', excluded_ctrl_list)
+        controllers = [
+            controller for controller in controllers if not _excluded(excluded_ctrl_list, controller.as_dict())
+        ]
+    return controllers
+
+
+# ******************************************************************************
+class ControllerABC(abc.ABC):
+    '''@brief Base class used to manage the connection to a controller.'''
+
+    CONNECT_RETRY_PERIOD_SEC = 60
+    FAST_CONNECT_RETRY_PERIOD_SEC = 3
+
+    def __init__(self, tid: trid.TID, service, discovery_ctrl: bool = False):
+        self._tid = tid
+        self._serv = service  # Refers to the parent service (either Staf or Stac)
+        self.set_level_from_tron(self._serv.tron)
+        self._cancellable = Gio.Cancellable()
+        self._connect_attempts = 0
+        self._retry_connect_tmr = gutil.GTimer(self.CONNECT_RETRY_PERIOD_SEC, self._on_try_to_connect)
+        self._discovery_ctrl = discovery_ctrl
+        self._try_to_connect_deferred = gutil.Deferred(self._try_to_connect)
+        self._try_to_connect_deferred.schedule()
+
+    def _release_resources(self):
+        # Remove pending deferred from main loop
+        if self._try_to_connect_deferred:
+            self._try_to_connect_deferred.cancel()
+
+        if self._retry_connect_tmr is not None:
+            self._retry_connect_tmr.kill()
+
+        if self._alive():
+            self._cancellable.cancel()
+
+        self._tid = None
+        self._serv = None
+        self._cancellable = None
+        self._retry_connect_tmr = None
+        self._try_to_connect_deferred = None
+
+    @property
+    def id(self) -> str:
+        '''@brief Return the Transport ID as a printable string'''
+        return str(self.tid)
+
+    @property
+    def tid(self):
+        '''@brief Return the Transport ID object'''
+        return self._tid
+
+    def controller_id_dict(self) -> dict:
+        '''@brief return the controller ID as a dict.'''
+        return {k: str(v) for k, v in self.tid.as_dict().items()}
+
+    def details(self) -> dict:
+        '''@brief return detailed debug info about this controller'''
+        return self.info()
+
+    def info(self) -> dict:
+        '''@brief Get the controller info for this object'''
+        info = self.controller_id_dict()
+        info['connect attempts'] = str(self._connect_attempts)
+        info['retry connect timer'] = str(self._retry_connect_tmr)
+        return info
+
+    def cancel(self):
+        '''@brief Used to cancel pending operations.'''
+        if self._alive():
+            logging.debug('ControllerABC.cancel()             - %s', self.id)
+            self._cancellable.cancel()
+
+    def kill(self):
+        '''@brief Used to release all resources associated with this object.'''
+        logging.debug('ControllerABC.kill()               - %s', self.id)
+        self._release_resources()
+
+    def _alive(self):
+        '''There may be race condition where a queued event gets processed
+        after the object is no longer configured (i.e. alive). This method
+        can be used by callback functions to make sure the object is still
+        alive before processing further.
+        '''
+        return self._cancellable and not self._cancellable.is_cancelled()
+
+    def _on_try_to_connect(self):
+        if self._alive():
+            self._try_to_connect_deferred.schedule()
+        return GLib.SOURCE_REMOVE
+
+    def _should_try_to_reconnect(self):  # pylint: disable=no-self-use
+        return True
+
+    def _try_to_connect(self):
+        if not self._alive():
+            return GLib.SOURCE_REMOVE
+
+        # This is a deferred function call. Make sure
+        # the source of the deferred is still good.
+        source = GLib.main_current_source()
+        if source and source.is_destroyed():
+            return GLib.SOURCE_REMOVE
+
+        self._connect_attempts += 1
+
+        self._do_connect()
+
+        return GLib.SOURCE_REMOVE
+
+    @abc.abstractmethod
+    def set_level_from_tron(self, tron):
+        '''Set log level based on TRON'''
+
+    @abc.abstractmethod
+    def _do_connect(self):
+        '''Perform connection'''
+
+    @abc.abstractmethod
+    def _on_aen(self, aen: int):
+        '''Event handler when an AEN is received'''
+
+    @abc.abstractmethod
+    def _on_nvme_event(self, nvme_event):
+        '''Event handler when an nvme_event is received'''
+
+    @abc.abstractmethod
+    def _on_ctrl_removed(self, udev_obj):
+        '''Called when the associated nvme device (/dev/nvmeX) is removed
+        from the system by the kernel.
+        '''
+
+    @abc.abstractmethod
+    def _find_existing_connection(self):
+        '''Check if there is an existing connection that matches this Controller's TID'''
+
+    @abc.abstractmethod
+    def all_ops_completed(self) -> bool:
+        '''@brief Returns True if all operations have completed. False otherwise.'''
+
+    @abc.abstractmethod
+    def connected(self):
+        '''@brief Return whether a connection is established'''
+
+    @abc.abstractmethod
+    def disconnect(self, disconnected_cb, keep_connection):
+        '''@brief Issue an asynchronous disconnect command to a Controller.
+        Once the async command has completed, the callback 'disconnected_cb'
+        will be invoked. If a controller is already disconnected, then the
+        callback will be added to the main loop's next idle slot to be executed
+        ASAP.
+        '''
+
+    @abc.abstractmethod
+    def reload_hdlr(self):
+        '''@brief This is called when a "reload" signal is received.'''
+
+
+# ******************************************************************************
+class ServiceABC(abc.ABC):  # pylint: disable=too-many-instance-attributes
+    '''@brief Base class used to manage a STorage Appliance Service'''
+
+    CONF_STABILITY_SOAK_TIME_SEC = 1.5
+
+    def __init__(self, args, default_conf, reload_hdlr):
+        service_conf = conf.SvcConf(default_conf=default_conf)
+        service_conf.set_conf_file(args.conf_file)  # reload configuration
+        self._tron = args.tron or service_conf.tron
+        log.set_level_from_tron(self._tron)
+
+        self._lkc_file = os.path.join(
+            os.environ.get('RUNTIME_DIRECTORY', os.path.join('/run', defs.PROG_NAME)), 'last-known-config.pickle'
+        )
+        self._loop = GLib.MainLoop()
+        self._cancellable = Gio.Cancellable()
+        self._resolver = gutil.NameResolver()
+        self._controllers = self._load_last_known_config()
+        self._dbus_iface = None
+        self._cfg_soak_tmr = gutil.GTimer(self.CONF_STABILITY_SOAK_TIME_SEC, self._on_config_ctrls)
+        self._sysbus = dasbus.connection.SystemMessageBus()
+
+        GLib.unix_signal_add(GLib.PRIORITY_HIGH, signal.SIGINT, self._stop_hdlr)  # CTRL-C
+        GLib.unix_signal_add(GLib.PRIORITY_HIGH, signal.SIGTERM, self._stop_hdlr)  # systemctl stop stafd
+        GLib.unix_signal_add(GLib.PRIORITY_HIGH, signal.SIGHUP, reload_hdlr)  # systemctl reload stafd
+
+        nvme_options = conf.NvmeOptions()
+        if not nvme_options.host_iface_supp or not nvme_options.discovery_supp:
+            logging.warning(
+                'Kernel does not appear to support all the options needed to run this program. Consider updating to a later kernel version.'
+            )
+
+        # We don't want to apply configuration changes right away.
+        # Often, multiple changes will occur in a short amount of time (sub-second).
+        # We want to wait until there are no more changes before applying them
+        # to the system. The following timer acts as a "soak period". Changes
+        # will be applied by calling self._on_config_ctrls() at the end of
+        # the soak period.
+        self._cfg_soak_tmr.start()
+
+    def _release_resources(self):
+        logging.debug('ServiceABC._release_resources()')
+
+        if self._alive():
+            self._cancellable.cancel()
+
+        if self._cfg_soak_tmr is not None:
+            self._cfg_soak_tmr.kill()
+
+        self._controllers.clear()
+
+        if self._sysbus:
+            self._sysbus.disconnect()
+
+        self._cfg_soak_tmr = None
+        self._cancellable = None
+        self._resolver = None
+        self._lkc_file = None
+        self._sysbus = None
+
+    def _config_dbus(self, iface_obj, bus_name: str, obj_name: str):
+        self._dbus_iface = iface_obj
+        self._sysbus.publish_object(obj_name, iface_obj)
+        self._sysbus.register_service(bus_name)
+
+    @property
+    def tron(self):
+        '''@brief Get Trace ON property'''
+        return self._tron
+
+    @tron.setter
+    def tron(self, value):
+        '''@brief Set Trace ON property'''
+        self._tron = value
+        log.set_level_from_tron(self._tron)
+        for controller in self._controllers.values():
+            controller.set_level_from_tron(self._tron)
+
+    def run(self):
+        '''@brief Start the main loop execution'''
+        try:
+            self._loop.run()
+        except Exception as ex:  # pylint: disable=broad-except
+            logging.critical('exception: %s', ex)
+
+        self._loop = None
+
+    def info(self) -> dict:
+        '''@brief Get the status info for this object (used for debug)'''
+        nvme_options = conf.NvmeOptions()
+        info = conf.SysConf().as_dict()
+        info['last known config file'] = self._lkc_file
+        info['config soak timer'] = str(self._cfg_soak_tmr)
+        info['kernel support.TP8013'] = str(nvme_options.discovery_supp)
+        info['kernel support.host_iface'] = str(nvme_options.host_iface_supp)
+        return info
+
+    def get_controllers(self) -> dict:
+        '''@brief return the list of controller objects'''
+        return self._controllers.values()
+
+    def get_controller(
+        self, transport: str, traddr: str, trsvcid: str, host_traddr: str, host_iface: str, subsysnqn: str
+    ):  # pylint: disable=too-many-arguments
+        '''@brief get the specified controller object from the list of controllers'''
+        cid = {
+            'transport': transport,
+            'traddr': traddr,
+            'trsvcid': trsvcid,
+            'host-traddr': host_traddr,
+            'host-iface': host_iface,
+            'subsysnqn': subsysnqn,
+        }
+        return self._controllers.get(trid.TID(cid))
+
+    def _remove_ctrl_from_dict(self, controller, shutdown=False):
+        tid_to_pop = controller.tid
+        if not tid_to_pop:
+            # Being paranoid. This should not happen, but let's say the
+            # controller object has been purged, but it is somehow still
+            # listed in self._controllers.
+            for tid, _controller in self._controllers.items():
+                if _controller is controller:
+                    tid_to_pop = tid
+                    break
+
+        if tid_to_pop:
+            logging.debug('ServiceABC._remove_ctrl_from_dict()- %s | %s', tid_to_pop, controller.device)
+            popped = self._controllers.pop(tid_to_pop, None)
+            if not shutdown and popped is not None and self._cfg_soak_tmr:
+                self._cfg_soak_tmr.start()
+        else:
+            logging.debug('ServiceABC._remove_ctrl_from_dict()- already removed')
+
+    def remove_controller(self, controller, success):  # pylint: disable=unused-argument
+        '''@brief remove the specified controller object from the list of controllers
+        @param controller: the controller object
+        @param success: whether the disconnect was successful'''
+        logging.debug('ServiceABC.remove_controller()')
+        if isinstance(controller, ControllerABC):
+            self._remove_ctrl_from_dict(controller)
+            controller.kill()
+
+    def _alive(self):
+        '''It's a good idea to check that this object hasn't been
+        cancelled (i.e. is still alive) when entering a callback function.
+        Callback functrions can be invoked after, for example, a process has
+        been signalled to stop or restart, in which case it makes no sense to
+        proceed with the callback.
+        '''
+        return self._cancellable and not self._cancellable.is_cancelled()
+
+    def _cancel(self):
+        logging.debug('ServiceABC._cancel()')
+        if self._alive():
+            self._cancellable.cancel()
+
+        for controller in self._controllers.values():
+            controller.cancel()
+
+    def _stop_hdlr(self):
+        logging.debug('ServiceABC._stop_hdlr()')
+        sd_notify('STOPPING=1')
+
+        self._cancel()  # Cancel pending operations
+
+        self._dump_last_known_config(self._controllers)
+
+        if len(self._controllers) == 0:
+            GLib.idle_add(self._exit)
+        else:
+            self._disconnect_all()
+
+        return GLib.SOURCE_REMOVE
+
+    def _on_final_disconnect(self, controller, success):
+        '''Callback invoked after a controller is disconnected.
+        THIS IS USED DURING PROCESS SHUTDOWN TO WAIT FOR ALL CONTROLLERS TO BE
+        DISCONNECTED BEFORE EXITING THE PROGRAM. ONLY CALL ON SHUTDOWN!
+        @param controller: the controller object
+        @param success: whether the disconnect operation was successful
+        '''
+        logging.debug(
+            'ServiceABC._on_final_disconnect()  - %s | %s: disconnect %s',
+            controller.id,
+            controller.device,
+            'succeeded' if success else 'failed',
+        )
+
+        self._remove_ctrl_from_dict(controller, True)
+        controller.kill()
+
+        # When all controllers have disconnected, we can finish the clean up
+        if len(self._controllers) == 0:
+            # Defer exit to the next main loop's idle period.
+            GLib.idle_add(self._exit)
+
+    def _exit(self):
+        logging.debug('ServiceABC._exit()')
+        self._release_resources()
+        self._loop.quit()
+
+    def _on_config_ctrls(self, *_user_data):
+        if self._alive():
+            self._config_ctrls()
+        return GLib.SOURCE_REMOVE
+
+    def _config_ctrls(self):
+        '''@brief Start controllers configuration.'''
+        # The configuration file may contain controllers and/or excluded
+        # controllers with traddr specified as hostname instead of IP address.
+        # Because of this, we need to remove those excluded elements before
+        # running name resolution. And we will need to remove excluded
+        # elements after name resolution is complete (i.e. in the calback
+        # function _config_ctrls_finish)
+        logging.debug('ServiceABC._config_ctrls()')
+        configured_controllers = [trid.TID(cid) for cid in conf.SvcConf().get_controllers()]
+        configured_controllers = remove_excluded(configured_controllers)
+        self._resolver.resolve_ctrl_async(self._cancellable, configured_controllers, self._config_ctrls_finish)
+
+    def _read_lkc(self):
+        '''@brief Read Last Known Config from file'''
+        try:
+            with open(self._lkc_file, 'rb') as file:
+                return pickle.load(file)
+        except (FileNotFoundError, AttributeError, EOFError):
+            return None
+
+    def _write_lkc(self, config):
+        '''@brief Write Last Known Config to file, and if config is empty
+        make sure the file is emptied.'''
+        try:
+            # Note that if config is empty we still
+            # want to open/close the file to empty it.
+            with open(self._lkc_file, 'wb') as file:
+                if config:
+                    pickle.dump(config, file)
+        except FileNotFoundError as ex:
+            logging.error('Unable to save last known config: %s', ex)
+
+    @abc.abstractmethod
+    def _disconnect_all(self):
+        '''Tell all controller objects to disconnect'''
+
+    @abc.abstractmethod
+    def _keep_connections_on_exit(self):
+        '''@brief Determine whether connections should remain when the
+        process exits.
+
+        NOTE) This is the base class method used to define the interface.
+        It must be overloaded by a child class.
+        '''
+
+    @abc.abstractmethod
+    def _config_ctrls_finish(self, configured_ctrl_list):
+        '''@brief Finish controllers configuration after hostnames (if any)
+        have been resolved.
+
+        Configuring controllers must be done asynchronously in 2 steps.
+        In the first step, host names get resolved to find their IP addresses.
+        Name resolution can take a while, especially when an external name
+        resolution server is used. Once that step completed, the callback
+        method _config_ctrls_finish() (i.e. this method), gets invoked to
+        complete the controller configuration.
+
+        NOTE) This is the base class method used to define the interface.
+        It must be overloaded by a child class.
+        '''
+
+    @abc.abstractmethod
+    def _load_last_known_config(self):
+        '''Load last known config from file (if any)'''
+
+    @abc.abstractmethod
+    def _dump_last_known_config(self, controllers):
+        '''Save last known config to file'''
diff --git a/staslib/timeparse.py b/staslib/timeparse.py
new file mode 100644
index 0000000..5295fc4
--- /dev/null
+++ b/staslib/timeparse.py
@@ -0,0 +1,139 @@
+#!/usr/bin/env python
+# -*- coding: utf-8 -*-
+
+'''
+This module was borrowed and modified from: https://github.com/wroberts/pytimeparse
+
+timeparse.py
+(c) Will Roberts <wildwilhelm@gmail.com>  1 February, 2014
+
+Implements a single function, `timeparse`, which can parse various
+kinds of time expressions.
+'''
+
+# MIT LICENSE
+#
+# Permission is hereby granted, free of charge, to any person
+# obtaining a copy of this software and associated documentation files
+# (the "Software"), to deal in the Software without restriction,
+# including without limitation the rights to use, copy, modify, merge,
+# publish, distribute, sublicense, and/or sell copies of the Software,
+# and to permit persons to whom the Software is furnished to do so,
+# subject to the following conditions:
+#
+# The above copyright notice and this permission notice shall be
+# included in all copies or substantial portions of the Software.
+#
+# THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
+# EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
+# MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
+# NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS
+# BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN
+# ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
+# CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+# SOFTWARE.
+
+import re
+
+SIGN = r'(?P<sign>[+|-])?'
+DAYS = r'(?P<days>[\d.]+)\s*(?:d|dys?|days?)'
+HOURS = r'(?P<hours>[\d.]+)\s*(?:h|hrs?|hours?)'
+MINS = r'(?P<mins>[\d.]+)\s*(?:m|(mins?)|(minutes?))'
+SECS = r'(?P<secs>[\d.]+)\s*(?:s|secs?|seconds?)'
+SEPARATORS = r'[,/]'
+SECCLOCK = r':(?P<secs>\d{2}(?:\.\d+)?)'
+MINCLOCK = r'(?P<mins>\d{1,2}):(?P<secs>\d{2}(?:\.\d+)?)'
+HOURCLOCK = r'(?P<hours>\d+):(?P<mins>\d{2}):(?P<secs>\d{2}(?:\.\d+)?)'
+DAYCLOCK = r'(?P<days>\d+):(?P<hours>\d{2}):(?P<mins>\d{2}):(?P<secs>\d{2}(?:\.\d+)?)'
+
+
+def _opt(string):
+    return f'(?:{string})?'
+
+
+def _optsep(string):
+    return fr'(?:{string}\s*(?:{SEPARATORS}\s*)?)?'
+
+
+TIMEFORMATS = [
+    fr'{_optsep(DAYS)}\s*{_optsep(HOURS)}\s*{_optsep(MINS)}\s*{_opt(SECS)}',
+    f'{MINCLOCK}',
+    fr'{_optsep(DAYS)}\s*{HOURCLOCK}',
+    f'{DAYCLOCK}',
+    f'{SECCLOCK}',
+]
+
+COMPILED_SIGN = re.compile(r'\s*' + SIGN + r'\s*(?P<unsigned>.*)$')
+COMPILED_TIMEFORMATS = [re.compile(r'\s*' + timefmt + r'\s*$', re.I) for timefmt in TIMEFORMATS]
+
+MULTIPLIERS = {
+    'days': 60 * 60 * 24,
+    'hours': 60 * 60,
+    'mins': 60,
+    'secs': 1,
+}
+
+
+def timeparse(sval):
+    '''
+    Parse a time expression, returning it as a number of seconds.  If
+    possible, the return value will be an `int`; if this is not
+    possible, the return will be a `float`.  Returns `None` if a time
+    expression cannot be parsed from the given string.
+
+    Arguments:
+    - `sval`: the string value to parse
+
+    >>> timeparse('1:24')
+    84
+    >>> timeparse(':22')
+    22
+    >>> timeparse('1 minute, 24 secs')
+    84
+    >>> timeparse('1m24s')
+    84
+    >>> timeparse('1.2 minutes')
+    72
+    >>> timeparse('1.2 seconds')
+    1.2
+
+    Time expressions can be signed.
+
+    >>> timeparse('- 1 minute')
+    -60
+    >>> timeparse('+ 1 minute')
+    60
+    '''
+    try:
+        return float(sval)
+    except TypeError:
+        pass
+    except ValueError:
+        match = COMPILED_SIGN.match(sval)
+        sign = -1 if match.groupdict()['sign'] == '-' else 1
+        sval = match.groupdict()['unsigned']
+        for timefmt in COMPILED_TIMEFORMATS:
+            match = timefmt.match(sval)
+            if match and match.group(0).strip():
+                mdict = match.groupdict()
+                # if all of the fields are integer numbers
+                if all(v.isdigit() for v in list(mdict.values()) if v):
+                    return sign * sum((MULTIPLIERS[k] * int(v, 10) for (k, v) in list(mdict.items()) if v is not None))
+
+                # if SECS is an integer number
+                if 'secs' not in mdict or mdict['secs'] is None or mdict['secs'].isdigit():
+                    # we will return an integer
+                    return sign * int(
+                        sum(
+                            (
+                                MULTIPLIERS[k] * float(v)
+                                for (k, v) in list(mdict.items())
+                                if k != 'secs' and v is not None
+                            )
+                        )
+                    ) + (int(mdict['secs'], 10) if mdict['secs'] else 0)
+
+                # SECS is a float, we will return a float
+                return sign * sum((MULTIPLIERS[k] * float(v) for (k, v) in list(mdict.items()) if v is not None))
+
+    return None
diff --git a/staslib/trid.py b/staslib/trid.py
new file mode 100644
index 0000000..ea40b7d
--- /dev/null
+++ b/staslib/trid.py
@@ -0,0 +1,137 @@
+# Copyright (c) 2022, Dell Inc. or its subsidiaries.  All rights reserved.
+# SPDX-License-Identifier: Apache-2.0
+# See the LICENSE file for details.
+#
+# This file is part of NVMe STorage Appliance Services (nvme-stas).
+#
+# Authors: Martin Belanger <Martin.Belanger@dell.com>
+#
+'''This module defines the Transport Identifier Object, which is used
+throughout nvme-stas to uniquely identify a Controller'''
+
+import hashlib
+from staslib import conf
+
+
+class TID:  # pylint: disable=too-many-instance-attributes
+    '''Transport Identifier'''
+
+    RDMA_IP_PORT = '4420'
+    DISC_IP_PORT = '8009'
+
+    def __init__(self, cid: dict):
+        '''@param cid: Controller Identifier. A dictionary with the following
+        contents.
+        {
+            # Transport parameters
+            'transport':   str, # [mandatory]
+            'traddr':      str, # [mandatory]
+            'subsysnqn':   str, # [mandatory]
+            'trsvcid':     str, # [optional]
+            'host-traddr': str, # [optional]
+            'host-iface':  str, # [optional]
+
+            # Connection parameters
+            'dhchap-ctrl-secret': str, # [optional]
+            'hdr-digest':         str, # [optional]
+            'data-digest':        str, # [optional]
+            'nr-io-queues':       str, # [optional]
+            'nr-write-queues':    str, # [optional]
+            'nr-poll-queues':     str, # [optional]
+            'queue-size':         str, # [optional]
+            'kato':               str, # [optional]
+            'reconnect-delay':    str, # [optional]
+            'ctrl-loss-tmo':      str, # [optional]
+            'disable-sqflow':     str, # [optional]
+        }
+        '''
+        self._cfg = {
+            k: v
+            for k, v in cid.items()
+            if k not in ('transport', 'traddr', 'subsysnqn', 'trsvcid', 'host-traddr', 'host-iface')
+        }
+        self._transport = cid.get('transport', '')
+        self._traddr = cid.get('traddr', '')
+        self._trsvcid = ''
+        if self._transport in ('tcp', 'rdma'):
+            trsvcid = cid.get('trsvcid', None)
+            self._trsvcid = (
+                trsvcid if trsvcid else (TID.RDMA_IP_PORT if self._transport == 'rdma' else TID.DISC_IP_PORT)
+            )
+        self._host_traddr = cid.get('host-traddr', '')
+        self._host_iface = '' if conf.SvcConf().ignore_iface else cid.get('host-iface', '')
+        self._subsysnqn = cid.get('subsysnqn', '')
+        self._shortkey = (self._transport, self._traddr, self._trsvcid, self._subsysnqn, self._host_traddr)
+        self._key = (self._transport, self._traddr, self._trsvcid, self._subsysnqn, self._host_traddr, self._host_iface)
+        self._hash = int.from_bytes(
+            hashlib.md5(''.join(self._key).encode('utf-8')).digest(), 'big'
+        )  # We need a consistent hash between restarts
+        self._id = f'({self._transport}, {self._traddr}, {self._trsvcid}{", " + self._subsysnqn if self._subsysnqn else ""}{", " + self._host_iface if self._host_iface else ""}{", " + self._host_traddr if self._host_traddr else ""})'  # pylint: disable=line-too-long
+
+    @property
+    def transport(self):  # pylint: disable=missing-function-docstring
+        return self._transport
+
+    @property
+    def traddr(self):  # pylint: disable=missing-function-docstring
+        return self._traddr
+
+    @property
+    def trsvcid(self):  # pylint: disable=missing-function-docstring
+        return self._trsvcid
+
+    @property
+    def host_traddr(self):  # pylint: disable=missing-function-docstring
+        return self._host_traddr
+
+    @property
+    def host_iface(self):  # pylint: disable=missing-function-docstring
+        return self._host_iface
+
+    @property
+    def subsysnqn(self):  # pylint: disable=missing-function-docstring
+        return self._subsysnqn
+
+    @property
+    def cfg(self):  # pylint: disable=missing-function-docstring
+        return self._cfg
+
+    def as_dict(self):
+        '''Return object members as a dictionary'''
+        data = {
+            'transport': self.transport,
+            'traddr': self.traddr,
+            'subsysnqn': self.subsysnqn,
+            'trsvcid': self.trsvcid,
+            'host-traddr': self.host_traddr,
+            'host-iface': self.host_iface,
+        }
+        data.update(self._cfg)
+        return data
+
+    def __str__(self):
+        return self._id
+
+    def __repr__(self):
+        return self._id
+
+    def __eq__(self, other):
+        if not isinstance(other, self.__class__):
+            return False
+
+        if self._host_iface and other._host_iface:
+            return self._key == other._key
+
+        return self._shortkey == other._shortkey
+
+    def __ne__(self, other):
+        if not isinstance(other, self.__class__):
+            return True
+
+        if self._host_iface and other._host_iface:
+            return self._key != other._key
+
+        return self._shortkey != other._shortkey
+
+    def __hash__(self):
+        return self._hash
diff --git a/staslib/udev.py b/staslib/udev.py
new file mode 100644
index 0000000..12ef61b
--- /dev/null
+++ b/staslib/udev.py
@@ -0,0 +1,334 @@
+# Copyright (c) 2022, Dell Inc. or its subsidiaries.  All rights reserved.
+# SPDX-License-Identifier: Apache-2.0
+# See the LICENSE file for details.
+#
+# This file is part of NVMe STorage Appliance Services (nvme-stas).
+#
+# Authors: Martin Belanger <Martin.Belanger@dell.com>
+#
+'''This module provides functions to access nvme devices using the pyudev module'''
+
+import os
+import time
+import logging
+import pyudev
+from gi.repository import GLib
+from staslib import defs, iputil, trid
+
+
+# ******************************************************************************
+class Udev:
+    '''@brief Udev event monitor. Provide a way to register for udev events.
+    WARNING: THE singleton.Singleton PATTERN CANNOT BE USED WITH THIS CLASS.
+    IT INTERFERES WITH THE pyudev INTERNALS, WHICH CAUSES OBJECT CLEAN UP TO FAIL.
+    '''
+
+    def __init__(self):
+        self._log_event_soak_time = 0
+        self._log_event_count = 0
+        self._device_event_registry = dict()
+        self._action_event_registry = dict()
+        self._context = pyudev.Context()
+        self._monitor = pyudev.Monitor.from_netlink(self._context)
+        self._monitor.filter_by(subsystem='nvme')
+        self._event_source = GLib.io_add_watch(
+            self._monitor.fileno(),
+            GLib.PRIORITY_HIGH,
+            GLib.IO_IN,
+            self._process_udev_event,
+        )
+        self._monitor.start()
+
+    def release_resources(self):
+        '''Release all resources used by this object'''
+        if self._event_source is not None:
+            GLib.source_remove(self._event_source)
+
+        if self._monitor is not None:
+            self._monitor.remove_filter()
+
+        self._event_source = None
+        self._monitor = None
+        self._context = None
+        self._device_event_registry = None
+        self._action_event_registry = None
+
+    def get_nvme_device(self, sys_name):
+        '''@brief Get the udev device object associated with an nvme device.
+        @param sys_name: The device system name (e.g. 'nvme1')
+        @return A pyudev.device._device.Device object
+        '''
+        device_node = os.path.join('/dev', sys_name)
+        try:
+            return pyudev.Devices.from_device_file(self._context, device_node)
+        except pyudev.DeviceNotFoundByFileError as ex:
+            logging.error("Udev.get_nvme_device() - Error: %s", ex)
+            return None
+
+    def is_action_cback_registered(self, action: str, user_cback):
+        '''Returns True if @user_cback is registered for @action. False otherwise.
+        @param action: one of 'add', 'remove', 'change'.
+        @param user_cback: A callback function with this signature: cback(udev_obj)
+        '''
+        return user_cback in self._action_event_registry.get(action, set())
+
+    def register_for_action_events(self, action: str, user_cback):
+        '''@brief Register a callback function to be called when udev events
+        for a specific action are received.
+        @param action: one of 'add', 'remove', 'change'.
+        '''
+        self._action_event_registry.setdefault(action, set()).add(user_cback)
+
+    def unregister_for_action_events(self, action: str, user_cback):
+        '''@brief The opposite of register_for_action_events()'''
+        try:
+            self._action_event_registry.get(action, set()).remove(user_cback)
+        except KeyError:  # Raise if user_cback already removed
+            pass
+
+    def register_for_device_events(self, sys_name: str, user_cback):
+        '''@brief Register a callback function to be called when udev events
+        are received for a specific nvme device.
+        @param sys_name: The device system name (e.g. 'nvme1')
+        '''
+        if sys_name:
+            self._device_event_registry[sys_name] = user_cback
+
+    def unregister_for_device_events(self, user_cback):
+        '''@brief The opposite of register_for_device_events()'''
+        entries = list(self._device_event_registry.items())
+        for sys_name, _user_cback in entries:
+            if user_cback == _user_cback:
+                self._device_event_registry.pop(sys_name, None)
+                break
+
+    def get_attributes(self, sys_name: str, attr_ids) -> dict:
+        '''@brief Get all the attributes associated with device @sys_name'''
+        attrs = {attr_id: '' for attr_id in attr_ids}
+        if sys_name and sys_name != 'nvme?':
+            udev = self.get_nvme_device(sys_name)
+            if udev is not None:
+                for attr_id in attr_ids:
+                    try:
+                        value = udev.attributes.asstring(attr_id).strip()
+                        attrs[attr_id] = '' if value == '(efault)' else value
+                    except Exception:  # pylint: disable=broad-except
+                        pass
+
+        return attrs
+
+    @staticmethod
+    def is_dc_device(device):
+        '''@brief check whether device refers to a Discovery Controller'''
+        subsysnqn = device.attributes.get('subsysnqn')
+        if subsysnqn is not None and subsysnqn.decode() == defs.WELL_KNOWN_DISC_NQN:
+            return True
+
+        # Note: Prior to 5.18 linux didn't expose the cntrltype through
+        # the sysfs. So, this may return None on older kernels.
+        cntrltype = device.attributes.get('cntrltype')
+        if cntrltype is not None and cntrltype.decode() == 'discovery':
+            return True
+
+        # Imply Discovery controller based on the absence of children.
+        # Discovery Controllers have no children devices
+        if len(list(device.children)) == 0:
+            return True
+
+        return False
+
+    @staticmethod
+    def is_ioc_device(device):
+        '''@brief check whether device refers to an I/O Controller'''
+        # Note: Prior to 5.18 linux didn't expose the cntrltype through
+        # the sysfs. So, this may return None on older kernels.
+        cntrltype = device.attributes.get('cntrltype')
+        if cntrltype is not None and cntrltype.decode() == 'io':
+            return True
+
+        # Imply I/O controller based on the presence of children.
+        # I/O Controllers have children devices
+        if len(list(device.children)) != 0:
+            return True
+
+        return False
+
+    def find_nvme_dc_device(self, tid):
+        '''@brief  Find the nvme device associated with the specified
+                Discovery Controller.
+        @return The device if a match is found, None otherwise.
+        '''
+        for device in self._context.list_devices(
+            subsystem='nvme', NVME_TRADDR=tid.traddr, NVME_TRSVCID=tid.trsvcid, NVME_TRTYPE=tid.transport
+        ):
+            if not self.is_dc_device(device):
+                continue
+
+            if self.get_tid(device) != tid:
+                continue
+
+            return device
+
+        return None
+
+    def find_nvme_ioc_device(self, tid):
+        '''@brief  Find the nvme device associated with the specified
+                I/O Controller.
+        @return The device if a match is found, None otherwise.
+        '''
+        for device in self._context.list_devices(
+            subsystem='nvme', NVME_TRADDR=tid.traddr, NVME_TRSVCID=tid.trsvcid, NVME_TRTYPE=tid.transport
+        ):
+            if not self.is_ioc_device(device):
+                continue
+
+            if self.get_tid(device) != tid:
+                continue
+
+            return device
+
+        return None
+
+    def get_nvme_ioc_tids(self, transports):
+        '''@brief  Find all the I/O controller nvme devices in the system.
+        @return A list of pyudev.device._device.Device objects
+        '''
+        tids = []
+        for device in self._context.list_devices(subsystem='nvme'):
+            if device.properties.get('NVME_TRTYPE', '') not in transports:
+                continue
+
+            if not self.is_ioc_device(device):
+                continue
+
+            tids.append(self.get_tid(device))
+
+        return tids
+
+    def _process_udev_event(self, event_source, condition):  # pylint: disable=unused-argument
+        if condition == GLib.IO_IN:
+            event_count = 0
+            while True:
+                try:
+                    device = self._monitor.poll(timeout=0)
+                except EnvironmentError as ex:
+                    device = None
+                    # This event seems to happen in bursts.  So, let's suppress
+                    # logging for 2 seconds to avoid filling the syslog.
+                    self._log_event_count += 1
+                    now = time.time()
+                    if now > self._log_event_soak_time:
+                        logging.debug('Udev._process_udev_event()         - %s [%s]', ex, self._log_event_count)
+                        self._log_event_soak_time = now + 2
+                        self._log_event_count = 0
+
+                if device is None:
+                    break
+
+                event_count += 1
+                self._device_event(device, event_count)
+
+        return GLib.SOURCE_CONTINUE
+
+    @staticmethod
+    def __cback_names(action_cbacks, device_cback):
+        names = []
+        for cback in action_cbacks:
+            names.append(cback.__name__ + '()')
+        if device_cback:
+            names.append(device_cback.__name__ + '()')
+        return names
+
+    def _device_event(self, device, event_count):
+        action_cbacks = self._action_event_registry.get(device.action, set())
+        device_cback = self._device_event_registry.get(device.sys_name, None)
+
+        logging.debug(
+            'Udev._device_event()               - %-8s %-6s  %-8s  %s',
+            f'{device.sys_name}:',
+            device.action,
+            f'{event_count:2}:{device.sequence_number}',
+            self.__cback_names(action_cbacks, device_cback),
+        )
+
+        for action_cback in action_cbacks:
+            GLib.idle_add(action_cback, device)
+
+        if device_cback is not None:
+            GLib.idle_add(device_cback, device)
+
+    @staticmethod
+    def _get_property(device, prop, default=''):
+        prop = device.properties.get(prop, default)
+        return '' if prop.lower() == 'none' else prop
+
+    @staticmethod
+    def _get_attribute(device, attr_id, default=''):
+        try:
+            attr = device.attributes.asstring(attr_id).strip()
+        except Exception:  # pylint: disable=broad-except
+            attr = default
+
+        return '' if attr.lower() == 'none' else attr
+
+    @staticmethod
+    def get_key_from_attr(device, attr, key, delim=','):
+        '''Get attribute specified by attr, which is composed of key=value pairs.
+        Then return the value associated with key.
+        @param device: The Device object
+        @param attr: The device's attribute to get
+        @param key: The key to look for in the attribute
+        @param delim: Delimiter used between key=value pairs.
+        @example:
+            "address" attribute contains "trtype=tcp,traddr=10.10.1.100,trsvcid=4420,host_traddr=10.10.1.50"
+        '''
+        attr_str = Udev._get_attribute(device, attr)
+        if not attr_str:
+            return ''
+
+        if key[-1] != '=':
+            key += '='
+        start = attr_str.find(key)
+        if start < 0:
+            return ''
+        start += len(key)
+
+        end = attr_str.find(delim, start)
+        if end < 0:
+            return attr_str[start:]
+
+        return attr_str[start:end]
+
+    @staticmethod
+    def _get_host_iface(device):
+        host_iface = Udev._get_property(device, 'NVME_HOST_IFACE')
+        if not host_iface:
+            # We'll try to find the interface from the source address on
+            # the connection. Only available if kernel exposes the source
+            # address (src_addr) in the "address" attribute.
+            src_addr = Udev.get_key_from_attr(device, 'address', 'src_addr=')
+            host_iface = iputil.get_interface(src_addr)
+        return host_iface
+
+    @staticmethod
+    def get_tid(device):
+        '''@brief return the Transport ID associated with a udev device'''
+        cid = {
+            'transport': Udev._get_property(device, 'NVME_TRTYPE'),
+            'traddr': Udev._get_property(device, 'NVME_TRADDR'),
+            'trsvcid': Udev._get_property(device, 'NVME_TRSVCID'),
+            'host-traddr': Udev._get_property(device, 'NVME_HOST_TRADDR'),
+            'host-iface': Udev._get_host_iface(device),
+            'subsysnqn': Udev._get_attribute(device, 'subsysnqn'),
+        }
+        return trid.TID(cid)
+
+
+UDEV = Udev()  # Singleton
+
+
+def shutdown():
+    '''Destroy the UDEV singleton'''
+    global UDEV  # pylint: disable=global-statement,global-variable-not-assigned
+    UDEV.release_resources()
+    del UDEV
diff --git a/staslib/version.py b/staslib/version.py
new file mode 100644
index 0000000..999d916
--- /dev/null
+++ b/staslib/version.py
@@ -0,0 +1,64 @@
+# Copyright (c) 2021, Dell Inc. or its subsidiaries.  All rights reserved.
+# SPDX-License-Identifier: Apache-2.0
+# See the LICENSE file for details.
+#
+# This file is part of NVMe STorage Appliance Services (nvme-stas).
+#
+# Authors: Martin Belanger <Martin.Belanger@dell.com>
+#
+''' distutils (and hence LooseVersion) is being deprecated. None of the
+    suggested replacements (e.g. from pkg_resources import parse_version) quite
+    work with Linux kernel versions the way LooseVersion does.
+
+    It was suggested to simply lift the LooseVersion code and vendor it in,
+    which is what this module is about.
+'''
+
+import re
+
+
+class KernelVersion:
+    '''Code loosely lifted from distutils's LooseVersion'''
+
+    component_re = re.compile(r'(\d+ | [a-z]+ | \.)', re.VERBOSE)
+
+    def __init__(self, string: str):
+        self.string = string
+        self.version = self.__parse(string)
+
+    def __str__(self):
+        return self.string
+
+    def __repr__(self):
+        return f'KernelVersion ("{self}")'
+
+    def __eq__(self, other):
+        return self.version == self.__version(other)
+
+    def __lt__(self, other):
+        return self.version < self.__version(other)
+
+    def __le__(self, other):
+        return self.version <= self.__version(other)
+
+    def __gt__(self, other):
+        return self.version > self.__version(other)
+
+    def __ge__(self, other):
+        return self.version >= self.__version(other)
+
+    @staticmethod
+    def __version(obj):
+        return obj.version if isinstance(obj, KernelVersion) else KernelVersion.__parse(obj)
+
+    @staticmethod
+    def __parse(string):
+        components = []
+        for item in KernelVersion.component_re.split(string):
+            if item and item != '.':
+                try:
+                    components.append(int(item))
+                except ValueError:
+                    pass
+
+        return components