PAPI: Allow ipaddress object as argument and return values from API calls

The API calls that use any of vl_api_address_t, vl_api_ip4_address,
vl_api_ip6_address_t, vl_api_prefix_t, vl_api_ip4_prefix_t,
vl_api_ip6_prefix_t now accepts either the old style dictionary,
a text string (2001:db8::/32) or an ipaddress ojbect.

Unless it is called with '_no_type_conversion':True, it will
also return an appropriate ipaddress object.

Change-Id: I84e4a1577bd57f6b5ae725f316a523988b6a955b
Signed-off-by: Ole Troan <ot@cisco.com>

4 files changed, 266 insertions, 220 deletions

diff --git a/src/vpp-api/python/vpp_papi/tests/test_vpp_serializer.py b/src/vpp-api/python/vpp_papi/tests/test_vpp_serializer.py
index ba3190cadf9..ca3afc4dcef 100755
--- a/src/vpp-api/python/vpp_papi/tests/test_vpp_serializer.py
+++ b/src/vpp-api/python/vpp_papi/tests/test_vpp_serializer.py
@@ -4,10 +4,10 @@ import unittest
 from vpp_papi.vpp_serializer import VPPType, VPPEnumType
 from vpp_papi.vpp_serializer import VPPUnionType, VPPMessage
 from vpp_papi.vpp_serializer import VPPTypeAlias
-from vpp_papi.vpp_format import VPPFormat
 from socket import inet_pton, AF_INET, AF_INET6
 import logging
 import sys
+from ipaddress import *
 
 
 class TestAddType(unittest.TestCase):
@@ -27,8 +27,10 @@ class TestAddType(unittest.TestCase):
         af = VPPEnumType('vl_api_address_family_t', [["ADDRESS_IP4", 0],
                                                      ["ADDRESS_IP6", 1],
                                                      {"enumtype": "u32"}])
-        ip4 = VPPType('vl_api_ip4_address_t', [['u8', 'address', 4]])
-        ip6 = VPPType('vl_api_ip6_address_t', [['u8', 'address', 16]])
+        ip4 = VPPTypeAlias('vl_api_ip4_address_t', {'type': 'u8',
+                                                    'length': 4})
+        ip6 = VPPTypeAlias('vl_api_ip6_address_t', {'type': 'u8',
+                                                    'length': 16})
         VPPUnionType('vl_api_address_union_t',
                      [["vl_api_ip4_address_t", "ip4"],
                       ["vl_api_ip6_address_t", "ip6"]])
@@ -47,41 +49,34 @@ class TestAddType(unittest.TestCase):
                                                  'vla_address'],
                                                 ['u8', 'is_cool']])
 
-        b = ip4.pack({'address': inet_pton(AF_INET, '1.1.1.1')})
+        b = ip4.pack(inet_pton(AF_INET, '1.1.1.1'))
         self.assertEqual(len(b), 4)
         nt, size = ip4.unpack(b)
-        self.assertEqual(nt.address, inet_pton(AF_INET, '1.1.1.1'))
+        self.assertEqual(str(nt), '1.1.1.1')
 
-        b = ip6.pack({'address': inet_pton(AF_INET6, '1::1')})
+        b = ip6.pack(inet_pton(AF_INET6, '1::1'))
         self.assertEqual(len(b), 16)
 
         b = address.pack({'af': af.ADDRESS_IP4,
                           'un':
-                          {'ip4':
-                           {'address': inet_pton(AF_INET, '2.2.2.2')}}})
+                          {'ip4': inet_pton(AF_INET, '2.2.2.2')}})
         self.assertEqual(len(b), 20)
 
         nt, size = address.unpack(b)
-        self.assertEqual(nt.af, af.ADDRESS_IP4)
-        self.assertEqual(nt.un.ip4.address,
-                         inet_pton(AF_INET, '2.2.2.2'))
-        self.assertEqual(nt.un.ip6.address,
-                         inet_pton(AF_INET6, '0202:0202::'))
+        self.assertEqual(str(nt), '2.2.2.2')
 
         # List of addresses
         address_list = []
         for i in range(4):
             address_list.append({'af': af.ADDRESS_IP4,
                                  'un':
-                                 {'ip4':
-                                  {'address': inet_pton(AF_INET, '2.2.2.2')}}})
+                                 {'ip4': inet_pton(AF_INET, '2.2.2.2')}})
         b = va_address_list.pack({'count': len(address_list),
                                   'addresses': address_list})
         self.assertEqual(len(b), 81)
 
         nt, size = va_address_list.unpack(b)
-        self.assertEqual(nt.addresses[0].un.ip4.address,
-                         inet_pton(AF_INET, '2.2.2.2'))
+        self.assertEqual(str(nt.addresses[0]), '2.2.2.2')
 
         b = message_with_va_address_list.pack({'vla_address':
                                                {'count': len(address_list),
@@ -97,6 +92,12 @@ class TestAddType(unittest.TestCase):
                                                      {"enumtype": "u32"}])
         ip4 = VPPTypeAlias('vl_api_ip4_address_t', {'type': 'u8',
                                                     'length': 4})
+        b = ip4.pack('1.1.1.1')
+        self.assertEqual(len(b), 4)
+        nt, size = ip4.unpack(b)
+
+        self.assertEqual(str(nt), '1.1.1.1')
+
         ip6 = VPPTypeAlias('vl_api_ip6_address_t', {'type': 'u8',
                                                     'length': 16})
         VPPUnionType('vl_api_address_union_t',
@@ -108,44 +109,65 @@ class TestAddType(unittest.TestCase):
                            ['vl_api_address_union_t', 'un']])
 
         prefix = VPPType('vl_api_prefix_t',
-                          [['vl_api_address_t', 'address'],
-                           ['u8', 'address_length']])
+                         [['vl_api_address_t', 'address'],
+                          ['u8', 'address_length']])
         message = VPPMessage('svs',
-                          [['vl_api_prefix_t', 'prefix']])
+                             [['vl_api_prefix_t', 'prefix']])
         message_addr = VPPMessage('svs_address',
                                   [['vl_api_address_t', 'address']])
 
         b = message_addr.pack({'address': "1::1"})
         self.assertEqual(len(b), 20)
         nt, size = message_addr.unpack(b)
-        self.assertEqual("1::1", VPPFormat.unformat(nt.address))
+        self.assertEqual("1::1", str(nt.address))
         b = message_addr.pack({'address': "1.1.1.1"})
         self.assertEqual(len(b), 20)
         nt, size = message_addr.unpack(b)
-        self.assertEqual("1.1.1.1", VPPFormat.unformat(nt.address))
+        self.assertEqual("1.1.1.1", str(nt.address))
 
-        b = message.pack({'prefix': "1.1.1.1/24"})
+        b = message.pack({'prefix': "1.1.1.0/24"})
         self.assertEqual(len(b), 21)
         nt, size = message.unpack(b)
-        self.assertEqual("1.1.1.1/24", VPPFormat.unformat(nt.prefix))
+        self.assertEqual("1.1.1.0/24", str(nt.prefix))
 
         message_array = VPPMessage('address_array',
-                                   [['vl_api_ip4_address_t',
+                                   [['vl_api_ip6_address_t',
                                      'addresses', 2]])
-        b = message_array.pack({'addresses': ["1::1", "2::2"]})
-        self.assertEqual(len(b), 8)
-
+        b = message_array.pack({'addresses': [IPv6Address(u"1::1"), "2::2"]})
+        self.assertEqual(len(b), 32)
         message_array_vla = VPPMessage('address_array_vla',
                                        [['u32', 'num'],
-                                        ['vl_api_ip4_address_t',
+                                        ['vl_api_ip6_address_t',
                                          'addresses', 0, 'num']])
         b = message_array_vla.pack({'addresses': ["1::1", "2::2"], 'num': 2})
-        self.assertEqual(len(b), 12)
+        self.assertEqual(len(b), 36)
+
+        message_array4 = VPPMessage('address_array4',
+                                    [['vl_api_ip4_address_t',
+                                      'addresses', 2]])
+        b = message_array4.pack({'addresses': ["1.1.1.1", "2.2.2.2"]})
+        self.assertEqual(len(b), 8)
+        b = message_array4.pack({'addresses': [IPv4Address(u"1.1.1.1"),
+                                               "2.2.2.2"]})
+        self.assertEqual(len(b), 8)
+
+        message = VPPMessage('address', [['vl_api_address_t', 'address']])
+        b = message.pack({'address': '1::1'})
+        self.assertEqual(len(b), 20)
+        b = message.pack({'address': '1.1.1.1'})
+        self.assertEqual(len(b), 20)
+        message = VPPMessage('prefix', [['vl_api_prefix_t', 'prefix']])
+        b = message.pack({'prefix': '1::1/130'})
+        self.assertEqual(len(b), 21)
+        b = message.pack({'prefix': IPv6Network(u'1::/119')})
+        self.assertEqual(len(b), 21)
+        b = message.pack({'prefix': IPv4Network(u'1.1.0.0/16')})
+        self.assertEqual(len(b), 21)
 
     def test_zero_vla(self):
         '''Default zero'ed out for VLAs'''
         list = VPPType('vl_api_list_t',
-                         [['u8', 'count', 10]])
+                       [['u8', 'count', 10]])
 
         # Define an embedded VLA type
         valist = VPPType('vl_api_valist_t',
@@ -153,12 +175,12 @@ class TestAddType(unittest.TestCase):
                           ['u8', 'string', 0, 'count']])
         # Define a message
         vamessage = VPPMessage('vamsg',
-                          [['vl_api_valist_t', 'valist'],
-                           ['u8', 'is_something']])
+                               [['vl_api_valist_t', 'valist'],
+                                ['u8', 'is_something']])
 
         message = VPPMessage('msg',
-                          [['vl_api_list_t', 'list'],
-                           ['u8', 'is_something']])
+                             [['vl_api_list_t', 'list'],
+                              ['u8', 'is_something']])
 
         # Pack message without VLA specified
         b = message.pack({'is_something': 1})
diff --git a/src/vpp-api/python/vpp_papi/vpp_format.py b/src/vpp-api/python/vpp_papi/vpp_format.py
index 908606a92cc..1b880ecd248 100644
--- a/src/vpp-api/python/vpp_papi/vpp_format.py
+++ b/src/vpp-api/python/vpp_papi/vpp_format.py
@@ -15,137 +15,107 @@
 
 from socket import inet_pton, inet_ntop, AF_INET6, AF_INET
 import socket
+import ipaddress
 
+# Copies from vl_api_address_t definition
+ADDRESS_IP4 = 0
+ADDRESS_IP6 = 1
 
-class VPPFormatError(Exception):
-    pass
-
-
-class VPPFormat(object):
-    VPPFormatError = VPPFormatError
-
-    @staticmethod
-    def format_vl_api_ip6_prefix_t(args):
-        prefix, len = args.split('/')
-        return {'prefix': {'address': inet_pton(AF_INET6, prefix)},
-                'len': int(len)}
-
-    @staticmethod
-    def unformat_vl_api_ip6_prefix_t(args):
-        return "{}/{}".format(inet_ntop(AF_INET6, args.prefix),
-                              args.len)
-
-    @staticmethod
-    def format_vl_api_ip4_prefix_t(args):
-        prefix, len = args.split('/')
-        return {'prefix': {'address': inet_pton(AF_INET, prefix)},
-                'len': int(len)}
-
-    @staticmethod
-    def unformat_vl_api_ip4_prefix_t(args):
-        return "{}/{}".format(inet_ntop(AF_INET, args.prefix),
-                              args.len)
-
-    @staticmethod
-    def format_vl_api_ip6_address_t(args):
-        return {'address': inet_pton(AF_INET6, args)}
-
-    @staticmethod
-    def format_vl_api_ip4_address_t(args):
-        return {'address': inet_pton(AF_INET, args)}
-
-    @staticmethod
-    def format_vl_api_address_t(args):
-        try:
-            return {'un': {'ip6': inet_pton(AF_INET6, args)},
-                    'af': int(1)}
-        except socket.error as e:
-            return {'un': {'ip4': inet_pton(AF_INET, args)},
-                    'af': int(0)}
-
-    @staticmethod
-    def unformat_vl_api_address_t(arg):
-        if arg.af == 1:
-            return inet_ntop(AF_INET6, arg.un.ip6)
-        if arg.af == 0:
-            return inet_ntop(AF_INET, arg.un.ip4)
-        raise VPPFormatError
-
-    @staticmethod
-    def format_vl_api_prefix_t(args):
-        prefix, len = args.split('/')
-        return {'address': VPPFormat.format_vl_api_address_t(prefix),
-                'address_length': int(len)}
-
-    @staticmethod
-    def unformat_vl_api_prefix_t(arg):
-        if arg.address.af == 1:
-            return "{}/{}".format(inet_ntop(AF_INET6,
-                                            arg.address.un.ip6),
-                                  arg.address_length)
-        if arg.address.af == 0:
-            return "{}/{}".format(inet_ntop(AF_INET,
-                                            arg.address.un.ip4),
-                                  arg.address_length)
-        raise VPPFormatError
-
-    @staticmethod
-    def format_u8(args):
-        try:
-            return int(args)
-        except Exception as e:
-            return args.encode()
-
-    @staticmethod
-    def format(typename, args):
-        try:
-            return getattr(VPPFormat, 'format_' + typename)(args)
-        except AttributeError:
-            # Default
-            return (int(args))
-
-    @staticmethod
-    def unformat_bytes(args):
-        try:
-            return args.decode('utf-8')
-        except ValueError as e:
-            return args
-
-    @staticmethod
-    def unformat_list(args):
-        s = '['
-        for f in args:
-            t = type(f).__name__
-            if type(f) is int:
-                s2 = str(f)
-            else:
-                s2 = VPPFormat.unformat_t(t, f)
-            s += '{} '.format(s2)
-        return s[:-1] + ']'
-
-    @staticmethod
-    def unformat(args):
-        s = ''
-        return VPPFormat.unformat_t(type(args).__name__, args)
-        '''
-        for i, f in enumerate(args):
-            print('F', f)
-            t = type(f).__name__
-            if type(f) is int:
-                s2 = str(f)
-            else:
-                s2 = VPPFormat.unformat_t(t, f)
-            s += '{} {} '.format(args._fields[i], s2)
-        return s[:-1]
-        '''
-
-    @staticmethod
-    def unformat_t(typename, args):
-        try:
-            return getattr(VPPFormat, 'unformat_' + typename)(args)
-        except AttributeError:
-            # Type without explicit override
-            return VPPFormat.unformat(args)
-
-        # Default handling
-        return args
+#
+# Type conversion for input arguments and return values
+#
+
+
+def format_vl_api_address_t(args):
+    try:
+        return {'un': {'ip6': inet_pton(AF_INET6, args)},
+                'af': ADDRESS_IP6}
+    except socket.error as e:
+        return {'un': {'ip4': inet_pton(AF_INET, args)},
+                'af': ADDRESS_IP4}
+
+
+def format_vl_api_prefix_t(args):
+    p, length = args.split('/')
+    return {'address': format_vl_api_address_t(p),
+            'address_length': int(length)}
+
+
+def format_vl_api_ip6_prefix_t(args):
+    p, length = args.split('/')
+    return {'prefix': inet_pton(AF_INET6, p),
+            'len': int(length)}
+
+
+def format_vl_api_ip4_prefix_t(args):
+    p, length = args.split('/')
+    return {'prefix': inet_pton(AF_INET, p),
+            'len': int(length)}
+
+
+conversion_table = {
+    'vl_api_ip6_address_t':
+    {
+        'IPv6Address': lambda o: o.packed,
+        'str': lambda s: inet_pton(AF_INET6, s)
+    },
+    'vl_api_ip4_address_t':
+    {
+        'IPv4Address': lambda o: o.packed,
+        'str': lambda s: inet_pton(AF_INET, s)
+    },
+    'vl_api_ip6_prefix_t':
+    {
+        'IPv6Network': lambda o: {'prefix': o.network_address.packed,
+                                  'len': o.prefixlen},
+        'str': lambda s: format_vl_api_ip6_prefix_t(s)
+    },
+    'vl_api_ip4_prefix_t':
+    {
+        'IPv4Network': lambda o: {'prefix': o.network_address.packed,
+                                  'len': o.prefixlen},
+        'str': lambda s: format_vl_api_ip4_prefix_t(s)
+    },
+    'vl_api_address_t':
+    {
+        'IPv4Address': lambda o: {'af': ADDRESS_IP4, 'un': {'ip4': o.packed}},
+        'IPv6Address': lambda o: {'af': ADDRESS_IP6, 'un': {'ip6': o.packed}},
+        'str': lambda s: format_vl_api_address_t(s)
+    },
+    'vl_api_prefix_t':
+    {
+        'IPv4Network': lambda o: {'prefix':
+                                  {'af': ADDRESS_IP4, 'un':
+                                   {'ip4': o.network_address.packed}},
+                                  'len': o.prefixlen},
+        'IPv6Network': lambda o: {'prefix':
+                                  {'af': ADDRESS_IP6, 'un':
+                                   {'ip6': o.network_address.packed}},
+                                  'len': o.prefixlen},
+        'str': lambda s: format_vl_api_prefix_t(s)
+    },
+}
+
+
+def unformat_api_address_t(o):
+    if o.af == 1:
+        return ipaddress.IPv6Address(o.un.ip6)
+    if o.af == 0:
+        return ipaddress.IPv4Address(o.un.ip4)
+
+
+def unformat_api_prefix_t(o):
+    if isinstance(o.address, ipaddress.IPv4Address):
+        return ipaddress.IPv4Network((o.address, o.address_length), False)
+    if isinstance(o.address, ipaddress.IPv6Address):
+        return ipaddress.IPv6Network((o.address, o.address_length), False)
+
+
+conversion_unpacker_table = {
+    'vl_api_ip6_address_t': lambda o: ipaddress.IPv6Address(o),
+    'vl_api_ip6_prefix_t': lambda o: ipaddress.IPv6Network((o.prefix, o.len)),
+    'vl_api_ip4_address_t': lambda o: ipaddress.IPv4Address(o),
+    'vl_api_ip4_prefix_t': lambda o: ipaddress.IPv4Network((o.prefix, o.len)),
+    'vl_api_address_t': lambda o: unformat_api_address_t(o),
+    'vl_api_prefix_t': lambda o: unformat_api_prefix_t(o),
+}
diff --git a/src/vpp-api/python/vpp_papi/vpp_papi.py b/src/vpp-api/python/vpp_papi/vpp_papi.py
index c37334cd4e5..32abe14da94 100644
--- a/src/vpp-api/python/vpp_papi/vpp_papi.py
+++ b/src/vpp-api/python/vpp_papi/vpp_papi.py
@@ -28,7 +28,6 @@ import weakref
 import atexit
 from . vpp_serializer import VPPType, VPPEnumType, VPPUnionType, BaseTypes
 from . vpp_serializer import VPPMessage, vpp_get_type, VPPTypeAlias
-from . vpp_format import VPPFormat
 
 if sys.version[0] == '2':
     import Queue as queue
@@ -56,11 +55,11 @@ def vpp_atexit(vpp_weakref):
         vpp_instance.logger.debug('Cleaning up VPP on exit')
         vpp_instance.disconnect()
 
-
-def vpp_iterator(d):
-    if sys.version[0] == '2':
+if sys.version[0] == '2':
+    def vpp_iterator(d):
         return d.iteritems()
-    else:
+else:
+    def vpp_iterator(d):
         return d.items()
 
 
@@ -409,7 +408,8 @@ class VPP(object):
 
                 # Create function for client side messages.
                 if name in self.services:
-                    if 'stream' in self.services[name] and self.services[name]['stream']:
+                    if 'stream' in self.services[name] and \
+                       self.services[name]['stream']:
                         multipart = True
                     else:
                         multipart = False
@@ -493,7 +493,7 @@ class VPP(object):
         else:
             raise VPPIOError(2, 'RPC reply message received in event handler')
 
-    def decode_incoming_msg(self, msg):
+    def decode_incoming_msg(self, msg, no_type_conversion=False):
         if not msg:
             self.logger.warning('vpp_api.read failed')
             return
@@ -508,7 +508,7 @@ class VPP(object):
         if not msgobj:
             raise VPPIOError(2, 'Reply message undefined')
 
-        r, size = msgobj.unpack(msg)
+        r, size = msgobj.unpack(msg, ntc=no_type_conversion)
         return r
 
     def msg_handler_async(self, msg):
@@ -535,7 +535,7 @@ class VPP(object):
         d = set(kwargs.keys()) - set(msg.field_by_name.keys())
         if d:
             raise VPPValueError('Invalid argument {} to {}'
-                             .format(list(d), msg.name))
+                                .format(list(d), msg.name))
 
     def _call_vpp(self, i, msg, multipart, **kwargs):
         """Given a message, send the message and await a reply.
@@ -560,6 +560,8 @@ class VPP(object):
             context = kwargs['context']
         kwargs['_vl_msg_id'] = i
 
+        no_type_conversion = kwargs.pop('_no_type_conversion', False)
+
         try:
             if self.transport.socket_index:
                 kwargs['client_index'] = self.transport.socket_index
@@ -582,7 +584,7 @@ class VPP(object):
             msg = self.transport.read()
             if not msg:
                 raise VPPIOError(2, 'VPP API client: read failed')
-            r = self.decode_incoming_msg(msg)
+            r = self.decode_incoming_msg(msg, no_type_conversion)
             msgname = type(r).__name__
             if context not in r or r.context == 0 or context != r.context:
                 # Message being queued
diff --git a/src/vpp-api/python/vpp_papi/vpp_serializer.py b/src/vpp-api/python/vpp_papi/vpp_serializer.py
index 13721ff88d4..5dce03b6188 100644
--- a/src/vpp-api/python/vpp_papi/vpp_serializer.py
+++ b/src/vpp-api/python/vpp_papi/vpp_serializer.py
@@ -17,7 +17,10 @@ import struct
 import collections
 from enum import IntEnum
 import logging
-from .vpp_format import VPPFormat
+from . import vpp_format
+import ipaddress
+import sys
+import socket
 
 #
 # Set log-level in application by doing e.g.:
@@ -26,6 +29,32 @@ from .vpp_format import VPPFormat
 #
 logger = logging.getLogger(__name__)
 
+if sys.version[0] == '2':
+    check = lambda d: type(d) is dict
+else:
+    check = lambda d: type(d) is dict or type(d) is bytes
+
+def conversion_required(data, field_type):
+    if check(data):
+        return False
+    try:
+        if type(data).__name__ in vpp_format.conversion_table[field_type]:
+            return True
+    except KeyError:
+        return False
+
+
+def conversion_packer(data, field_type):
+    t = type(data).__name__
+    return types[field_type].pack(vpp_format.
+                                  conversion_table[field_type][t](data))
+
+
+def conversion_unpacker(data, field_type):
+    if field_type not in vpp_format.conversion_unpacker_table:
+        return data
+    return vpp_format.conversion_unpacker_table[field_type](data)
+
 
 class BaseTypes(object):
     def __init__(self, type, elements=0):
@@ -51,7 +80,7 @@ class BaseTypes(object):
             data = 0
         return self.packer.pack(data)
 
-    def unpack(self, data, offset, result=None):
+    def unpack(self, data, offset, result=None, ntc=False):
         return self.packer.unpack_from(data, offset)[0], self.packer.size
 
 
@@ -79,19 +108,21 @@ class FixedList_u8(object):
         self.packer = BaseTypes(field_type, num)
         self.size = self.packer.size
 
-    def pack(self, list, kwargs=None):
+    def pack(self, data, kwargs=None):
         """Packs a fixed length bytestring. Left-pads with zeros
         if input data is too short."""
-        if not list:
+        if not data:
             return b'\x00' * self.size
-        if len(list) > self.num:
+
+        if len(data) > self.num:
             raise VPPSerializerValueError(
                 'Fixed list length error for "{}", got: {}'
                 ' expected: {}'
-                .format(self.name, len(list), self.num))
-        return self.packer.pack(list)
+                .format(self.name, len(data), self.num))
+
+        return self.packer.pack(data)
 
-    def unpack(self, data, offset=0, result=None):
+    def unpack(self, data, offset=0, result=None, ntc=False):
         if len(data[offset:]) < self.num:
             raise VPPSerializerValueError(
                 'Invalid array length for "{}" got {}'
@@ -105,6 +136,8 @@ class FixedList(object):
         self.num = num
         self.packer = types[field_type]
         self.size = self.packer.size * num
+        self.name = name
+        self.field_type = field_type
 
     def pack(self, list, kwargs):
         if len(list) != self.num:
@@ -116,12 +149,12 @@ class FixedList(object):
             b += self.packer.pack(e)
         return b
 
-    def unpack(self, data, offset=0, result=None):
+    def unpack(self, data, offset=0, result=None, ntc=False):
         # Return a list of arguments
         result = []
         total = 0
         for e in range(self.num):
-            x, size = self.packer.unpack(data, offset)
+            x, size = self.packer.unpack(data, offset, ntc=ntc)
             result.append(x)
             offset += size
             total += size
@@ -153,7 +186,7 @@ class VLAList(object):
             b += self.packer.pack(e)
         return b
 
-    def unpack(self, data, offset=0, result=None):
+    def unpack(self, data, offset=0, result=None, ntc=False):
         # Return a list of arguments
         total = 0
 
@@ -162,11 +195,11 @@ class VLAList(object):
             if result[self.index] == 0:
                 return b'', 0
             p = BaseTypes('u8', result[self.index])
-            return p.unpack(data, offset)
+            return p.unpack(data, offset, ntc=ntc)
 
         r = []
         for e in range(result[self.index]):
-            x, size = self.packer.unpack(data, offset)
+            x, size = self.packer.unpack(data, offset, ntc=ntc)
             r.append(x)
             offset += size
             total += size
@@ -187,7 +220,7 @@ class VLAList_legacy():
             b += self.packer.pack(e)
         return b
 
-    def unpack(self, data, offset=0, result=None):
+    def unpack(self, data, offset=0, result=None, ntc=False):
         total = 0
         # Return a list of arguments
         if (len(data) - offset) % self.packer.size:
@@ -196,7 +229,7 @@ class VLAList_legacy():
         elements = int((len(data) - offset) / self.packer.size)
         r = []
         for e in range(elements):
-            x, size = self.packer.unpack(data, offset)
+            x, size = self.packer.unpack(data, offset, ntc=ntc)
             r.append(x)
             offset += self.packer.size
             total += size
@@ -227,7 +260,7 @@ class VPPEnumType(object):
     def pack(self, data, kwargs=None):
         return types['u32'].pack(data)
 
-    def unpack(self, data, offset=0, result=None):
+    def unpack(self, data, offset=0, result=None, ntc=False):
         x, size = types['u32'].unpack(data, offset)
         return self.enum(x), size
 
@@ -272,31 +305,53 @@ class VPPUnionType(object):
         r[:len(b)] = b
         return r
 
-    def unpack(self, data, offset=0, result=None):
+    def unpack(self, data, offset=0, result=None, ntc=False):
         r = []
         maxsize = 0
         for k, p in self.packers.items():
-            x, size = p.unpack(data, offset)
+            x, size = p.unpack(data, offset, ntc=ntc)
             if size > maxsize:
                 maxsize = size
             r.append(x)
         return self.tuple._make(r), maxsize
 
 
-def VPPTypeAlias(name, msgdef):
-    t = vpp_get_type(msgdef['type'])
-    if not t:
-        raise ValueError()
-    if 'length' in msgdef:
-        if msgdef['length'] == 0:
+class VPPTypeAlias(object):
+    def __init__(self, name, msgdef):
+        self.name = name
+        t = vpp_get_type(msgdef['type'])
+        if not t:
             raise ValueError()
-        if msgdef['type'] == 'u8':
-            types[name] = FixedList_u8(name, msgdef['type'],
-                                       msgdef['length'])
+        if 'length' in msgdef:
+            if msgdef['length'] == 0:
+                raise ValueError()
+            if msgdef['type'] == 'u8':
+                self.packer = FixedList_u8(name, msgdef['type'],
+                                           msgdef['length'])
+                self.size = self.packer.size
+            else:
+                self.packer = FixedList(name, msgdef['type'], msgdef['length'])
         else:
-            types[name] = FixedList(name, msgdef['type'], msgdef['length'])
-    else:
-        types[name] = t
+            self.packer = t
+            self.size = t.size
+
+        types[name] = self
+
+    def pack(self, data, kwargs=None):
+        if data and conversion_required(data, self.name):
+            try:
+                return conversion_packer(data, self.name)
+            # Python 2 and 3 raises different exceptions from inet_pton
+            except(OSError, socket.error, TypeError):
+                pass
+
+        return self.packer.pack(data, kwargs)
+
+    def unpack(self, data, offset=0, result=None, ntc=False):
+        t, size = self.packer.unpack(data, offset, result, ntc=ntc)
+        if not ntc:
+            return conversion_unpacker(t, self.name), size
+        return t, size
 
 
 class VPPType(object):
@@ -352,9 +407,12 @@ class VPPType(object):
         if not kwargs:
             kwargs = data
         b = bytes()
-        for i, a in enumerate(self.fields):
 
-            # Try one of the format functions
+        # Try one of the format functions
+        if data and conversion_required(data, self.name):
+            return conversion_packer(data, self.name)
+
+        for i, a in enumerate(self.fields):
             if data and type(data) is not dict and a not in data:
                 raise VPPSerializerValueError(
                     "Invalid argument: {} expected {}.{}".
@@ -367,33 +425,27 @@ class VPPType(object):
             else:
                 arg = data[a]
                 kwarg = kwargs[a] if a in kwargs else None
-
             if isinstance(self.packers[i], VPPType):
-                try:
-                    b += self.packers[i].pack(arg, kwarg)
-                except ValueError:
-                    # Invalid argument, can we convert it?
-                    arg = VPPFormat.format(self.packers[i].name, data[a])
-                    data[a] = arg
-                    kwarg = arg
-                    b += self.packers[i].pack(arg, kwarg)
+                b += self.packers[i].pack(arg, kwarg)
             else:
                 b += self.packers[i].pack(arg, kwargs)
 
         return b
 
-    def unpack(self, data, offset=0, result=None):
+    def unpack(self, data, offset=0, result=None, ntc=False):
         # Return a list of arguments
         result = []
         total = 0
         for p in self.packers:
-            x, size = p.unpack(data, offset, result)
+            x, size = p.unpack(data, offset, result, ntc)
             if type(x) is tuple and len(x) == 1:
                 x = x[0]
             result.append(x)
             offset += size
             total += size
         t = self.tuple._make(result)
+        if not ntc:
+            t = conversion_unpacker(t, self.name)
         return t, total