Pushed Stateless progress (along with Packet Builder module)

1 files changed, 720 insertions, 0 deletions

diff --git a/scripts/automation/trex_control_plane/client_utils/packet_builder.py b/scripts/automation/trex_control_plane/client_utils/packet_builder.py
new file mode 100644
index 00000000..fc34d931
--- /dev/null
+++ b/scripts/automation/trex_control_plane/client_utils/packet_builder.py
@@ -0,0 +1,720 @@
+#!/router/bin/python
+
+
+import outer_packages
+import dpkt
+import socket
+import binascii
+import copy
+import random
+import string
+import struct
+import re
+
+
+class CTRexPktBuilder(object):
+    """
+    This class defines the TRex API of building a packet using dpkt package.
+    Using this class the user can also define how TRex will handle the packet by specifying the VM setting.
+    """
+    def __init__(self, max_pkt_size=dpkt.ethernet.ETH_LEN_MAX):
+        """
+        Instantiate a CTRexPktBuilder object
+
+        :parameters:
+             None
+
+        """
+        super(CTRexPktBuilder, self).__init__()
+        self._packet = None
+        self._pkt_by_hdr = {}
+        self._pkt_top_layer = None
+        self._max_pkt_size = max_pkt_size
+        self.payload_generator = CTRexPktBuilder.CTRexPayloadGen(self._packet, self._max_pkt_size)
+        self.vm = CTRexPktBuilder.CTRexVM()
+
+    def add_pkt_layer(self, layer_name, pkt_layer):
+        """
+        This method adds additional header to the already existing packet
+
+        :parameters:
+            layer_name: str
+                a string representing the name of the layer.
+                Example: "l2", "l4_tcp", etc.
+
+            pkt_layer : dpkt.Packet obj
+                a dpkt object, generally from higher layer, that will be added on top of existing layer.
+
+        :raises:
+            + :exc:`ValueError`, in case the desired layer_name already exists.
+
+        """
+        assert isinstance(pkt_layer, dpkt.Packet)
+        if layer_name in self._pkt_by_hdr:
+            raise ValueError("Given layer name '{0}' already exists.".format(layer_name))
+        else:
+            dup_pkt = copy.copy(pkt_layer)  # using copy of layer to avoid cyclic packets that may lead to infinite loop
+            if not self._pkt_top_layer:     # this is the first header added
+                self._packet = dup_pkt
+            else:
+                self._pkt_top_layer.data = dup_pkt
+            self._pkt_top_layer = dup_pkt
+            self._pkt_by_hdr[layer_name] = dup_pkt
+            return
+
+    def set_ip_layer_addr(self, layer_name, attr, ip_addr, ip_type="ipv4"):
+        try:
+            layer = self._pkt_by_hdr[layer_name.lower()]
+            if not (isinstance(layer, dpkt.ip.IP) or isinstance(layer, dpkt.ip6.IP6)):
+                raise ValueError("The specified layer '{0}' is not of IPv4/IPv6 type.".format(layer_name))
+            else:
+                decoded_ip = CTRexPktBuilder._decode_ip_addr(ip_addr, ip_type)
+                setattr(layer, attr, decoded_ip)
+        except KeyError:
+            raise KeyError("Specified layer '{0}' doesn't exist on packet.".format(layer_name))
+
+    def set_ipv6_layer_addr(self, layer_name, attr, ip_addr):
+        self.set_ip_layer_addr(layer_name, attr, ip_addr, ip_type="ipv6")
+
+    def set_eth_layer_addr(self, layer_name, attr, mac_addr):
+        try:
+            layer = self._pkt_by_hdr[layer_name.lower()]
+            if not isinstance(layer, dpkt.ethernet.Ethernet):
+                raise ValueError("The specified layer '{0}' is not of Ethernet type.".format(layer_name))
+            else:
+                decoded_mac = CTRexPktBuilder._decode_mac_addr(mac_addr)
+                setattr(layer, attr, decoded_mac)
+        except KeyError:
+            raise KeyError("Specified layer '{0}' doesn't exist on packet.".format(layer_name))
+
+    def set_layer_attr(self, layer_name, attr, val, toggle_bit=False):
+        """
+        This method enables the user to change a value of a previously defined packet layer.
+        This method isn't to be used to set the data attribute of a packet with payload.
+        Use :func:`packet_builder.CTRexPktBuilder.set_payload` instead.
+
+        :parameters:
+            layer_name: str
+                a string representing the name of the layer.
+                Example: "l2", "l4_tcp", etc.
+
+            attr : str
+                a string representing the attribute to be changed on desired layer
+
+            val :
+                value of attribute.
+
+            toggle_bit : bool
+                Indicating if trying to set a specific bit of a field, such as "do not fragment" bit of IP layer.
+
+                Default: **False**
+
+        :raises:
+            + :exc:`KeyError`, in case of missing layer (the desired layer isn't part of packet)
+            + :exc:`ValueError`, in case invalid attribute to the specified layer.
+
+        """
+        try:
+            layer = self._pkt_by_hdr[layer_name.lower()]
+            if attr == 'data' and not isinstance(val, dpkt.Packet):
+                # Don't allow setting 'data' attribute
+                raise ValueError("Set a data attribute with object that is not dpkt.Packet is not allowed using "
+                                 "set_layer_attr method.\nUse set_payload method instead.")
+            if hasattr(layer, attr):
+                if toggle_bit:
+                    setattr(layer, attr, val | getattr(layer, attr, 0))
+                else:
+                    setattr(layer, attr, val)
+                    if attr == 'data':
+                        # re-evaluate packet from the start, possible broken link between layers
+                        self._reevaluate_packet(layer_name.lower())
+            else:
+                raise ValueError("Given attr name '{0}' doesn't exists on specified layer ({1}).".format(layer_name,
+                                                                                                         attr))
+        except KeyError:
+            raise KeyError("Specified layer '{0}' doesn't exist on packet.".format(layer_name))
+
+    def set_layer_bit_attr(self, layer_name, attr, val):
+        return self.set_layer_attr(layer_name, attr, val, True)
+
+    def set_pkt_payload(self, payload):
+        """
+        This method sets a payload to the topmost layer of the generated packet.
+        This method isn't to be used to set another networking layer to the packet.
+        Use :func:`packet_builder.CTRexPktBuilder.set_layer_attr` instead.
+
+
+        :parameters:
+            payload:
+                a payload to be added to the packet at the topmost layer.
+                this object cannot be of type dpkt.Packet.
+
+        :raises:
+            + :exc:`AttributeError`, in case no underlying header to host the payload.
+
+        """
+        assert isinstance(payload, str)
+        try:
+            self._pkt_top_layer.data = payload
+        except AttributeError:
+            raise AttributeError("The so far built packet doesn't contain an option for payload attachment.\n"
+                                 "Make sure to set appropriate underlying header before adding payload")
+
+    def load_packet(self, packet):
+        """
+        This method enables the user to change a value of a previously defined packet layer.
+
+        :parameters:
+            packet: dpkt.Packet obj
+                a dpkt object that represents a packet.
+
+
+        :raises:
+            + :exc:`CTRexPktBuilder.IPAddressError`, in case invalid ip type option specified.
+
+        """
+        assert isinstance(packet, dpkt.Packet)
+        self._packet = copy.copy(packet)
+
+        self._pkt_by_hdr.clear()
+        self._pkt_top_layer = self._packet
+        # analyze packet to layers
+        tmp_layer = self._packet
+        while True:
+            if isinstance(tmp_layer, dpkt.Packet):
+                layer_name = self._gen_layer_name(type(tmp_layer).__name__)
+                self._pkt_by_hdr[layer_name] = tmp_layer
+                self._pkt_top_layer = tmp_layer
+                try:
+                    # check existence of upper layer
+                    tmp_layer = tmp_layer.data
+                except AttributeError:
+                    # this is the most upper header
+                    self._pkt_by_hdr['pkt_final_payload'] = tmp_layer.data
+                    break
+            else:
+                self._pkt_by_hdr['pkt_final_payload'] = tmp_layer
+                break
+        return
+
+    def get_packet(self, get_ptr=False):
+        """
+        This method provides access to the built packet, as an instance or as a pointer to packet itself.
+
+        :parameters:
+            get_ptr : bool
+                indicate whether to get a reference to packet or a copy.
+                Use only in advanced modes
+                if set to true, metadata for packet is cleared, and any further modification is not guaranteed.
+
+                default value : False
+
+        :return:
+            + the current packet built by CTRexPktBuilder object.
+            + None if packet is empty
+
+        """
+        if get_ptr:
+            self._pkt_by_hdr = {}
+            self._pkt_top_layer = None
+            return self._packet
+        else:
+            return copy.copy(self._packet)
+
+    def get_layer(self, layer_name):
+        """
+        This method provides access to a specific layer of the packet, as a **copy of the layer instance**.
+
+        :parameters:
+            layer_name : str
+                the name given to desired layer
+
+        :return:
+            + a copy of the desired layer of the current packet if exists.
+            + None if no such layer
+
+        """
+        layer = self._pkt_by_hdr.get(layer_name)
+        return copy.copy(layer) if layer else None
+
+    # VM access methods
+    def set_vm_ip_range(self, ip_start, ip_end, ip_type="ipv4"):
+        pass
+
+    def set_vm_range_type(self, ip_type):
+        pass
+
+    def set_vm_core_mask(self, ip_type):
+        pass
+
+    def get_vm_data(self):
+        pass
+
+    def dump_pkt(self):
+        """
+        Dumps the packet as a decimal array of bytes (each item x gets value between 0-255)
+
+        :parameters:
+            None
+
+        :return:
+            + packet representation as array of bytes
+
+        :raises:
+            + :exc:`CTRexPktBuilder.EmptyPacketError`, in case packet is empty.
+
+        """
+        if self._packet is None:
+            raise CTRexPktBuilder.EmptyPacketError()
+        pkt_in_hex = binascii.hexlify(str(self._packet))
+        return [int(pkt_in_hex[i:i+2], 16)
+                for i in range(0, len(pkt_in_hex), 2)]
+        # return [pkt_in_hex[i:i+2] for i in range(0, len(pkt_in_hex), 2)]
+
+    def dump_pkt_to_pcap(self, file_path, ts=None):
+        """
+        Dumps the packet as a decimal array of bytes (each item x gets value between 0-255)
+
+        :parameters:
+            file_path : str
+                a path (including filename) to which to write to pcap file to.
+
+            ts : int
+                a timestamp to attach to the packet when dumped to pcap file.
+                if ts in None, then time.time() is used to set the timestamp.
+
+                Default: **None**
+
+        :return:
+            None
+
+        :raises:
+            + :exc:`CTRexPktBuilder.EmptyPacketError`, in case packet is empty.
+
+        """
+        if self._packet is None:
+            raise CTRexPktBuilder.EmptyPacketError()
+        try:
+            with open(file_path, 'wb') as f:
+                pcap_wr = dpkt.pcap.Writer(f)
+                pcap_wr.writepkt(self._packet, ts)
+                return
+        except IOError:
+            raise IOError(2, "The provided path could not be accessed")
+
+
+    # ----- useful shortcut methods ----- #
+    def gen_dns_packet(self):
+        pass
+
+    # ----- internal methods ----- #
+    def _reevaluate_packet(self, layer_name):
+        cur_layer = self._packet
+        known_layers = set(self._pkt_by_hdr.keys())
+        found_layers = set()
+        while True:
+            pointing_layer_name = self._find_pointing_layer(known_layers, cur_layer)
+            found_layers.add(pointing_layer_name)
+            if self._pkt_by_hdr[layer_name] is cur_layer:
+                self._pkt_top_layer = cur_layer
+                disconnected_layers = known_layers.difference(found_layers)
+                # remove disconnected layers
+                for layer in disconnected_layers:
+                    self._pkt_by_hdr.pop(layer)
+                break
+            else:
+                cur_layer = cur_layer.data
+
+    def _gen_layer_name(self, layer_class_name):
+        assert isinstance(layer_class_name, str)
+        layer_name = layer_class_name.lower()
+        idx = 1
+        while True:
+            tmp_name = "{name}_{id}".format(name=layer_name, id=idx)
+            if tmp_name not in self._pkt_by_hdr:
+                return tmp_name
+            else:
+                idx += 1
+
+    def _find_pointing_layer(self, known_layers, layer_obj):
+        assert isinstance(known_layers, set)
+        for layer in known_layers:
+            if self._pkt_by_hdr[layer] is layer_obj:
+                return layer
+
+    @staticmethod
+    def _decode_mac_addr(mac_addr):
+        """
+        Static method to test for MAC address validity.
+
+        :parameters:
+            mac_addr : str
+                a string representing an MAC address, separated by ':' or '-'.
+
+                examples: '00:de:34:ef:2e:f4', '00-de-34-ef-2e-f4
+
+        :return:
+            + an hex-string representation of the MAC address.
+              for example, ip 00:de:34:ef:2e:f4 will return '\x00\xdeU\xef.\xf4'
+
+        :raises:
+            + :exc:`CTRexPktBuilder.MACAddressError`, in case invalid ip type option specified.
+
+        """
+        tmp_mac = mac_addr.lower().replace('-', ':')
+        if re.match("[0-9a-f]{2}([-:])[0-9a-f]{2}(\\1[0-9a-f]{2}){4}$", tmp_mac):
+            return binascii.unhexlify(tmp_mac.replace(':', ''))
+            # another option for both Python 2 and 3: 
+            # codecs.decode(tmp_mac.replace(':', ''), 'hex')
+        else:
+            raise CTRexPktBuilder.MACAddressError()
+
+    @staticmethod
+    def _decode_ip_addr(ip_addr, ip_type):
+        """
+        Static method to test for IPv4/IPv6 address validity.
+
+        :parameters:
+            ip_addr : str
+                a string representing an IP address (IPv4/IPv6)
+
+            ip_type : str
+                The type of IP to be checked.
+                Valid types: "ipv4", "ipv6".
+
+        :return:
+            + an hex-string representation of the ip address.
+              for example, ip 1.2.3.4 will return '\x01\x02\x03\x04'
+
+        :raises:
+            + :exc:`CTRexPktBuilder.IPAddressError`, in case invalid ip type option specified.
+
+        """
+        if ip_type == "ipv4":
+            try:
+                return socket.inet_pton(socket.AF_INET, ip_addr)
+            except AttributeError:  # no inet_pton here, sorry
+                # try:
+                return socket.inet_aton(ip_addr)
+                # except socket.error:
+                #     return False
+                # return ip_addr.count('.') == 3
+            except socket.error:  # not a valid address
+                raise CTRexPktBuilder.IPAddressError()
+        elif ip_type == "ipv6":
+            try:
+                return socket.inet_pton(socket.AF_INET6, ip_addr)
+            except socket.error:  # not a valid address
+                raise CTRexPktBuilder.IPAddressError()
+        else:
+            raise CTRexPktBuilder.IPAddressError()
+
+    # ------ private classes ------ #
+    class CTRexPayloadGen(object):
+
+        def __init__(self, packet_ref, max_pkt_size):
+            self._pkt_ref = packet_ref
+            self._max_pkt_size = max_pkt_size
+
+        def gen_random_str(self):
+            gen_length = self._calc_gen_length()
+            # return a string of size gen_length bytes, to pad the packet to its max_size
+            return ''.join(random.SystemRandom().choice(string.ascii_letters + string.digits)
+                           for _ in range(gen_length))
+
+        def gen_repeat_ptrn(self, ptrn_to_repeat):
+            gen_length = self._calc_gen_length()
+            if isinstance(ptrn_to_repeat, str):
+                # generate repeated string
+                return (ptrn_to_repeat * (gen_length/len(ptrn_to_repeat) + 1))[:gen_length]
+            elif isinstance(ptrn_to_repeat, int):
+                ptrn = binascii.unhexlify(hex(ptrn_to_repeat)[2:])
+                return (ptrn * (gen_length/len(ptrn) + 1))[:gen_length]
+            elif isinstance(ptrn_to_repeat, tuple):
+                if not all((isinstance(x, int) and (x < 255) and (x >= 0))
+                           for x in ptrn_to_repeat):
+                    raise ValueError("All numbers in tuple must be in range 0 <= number <= 255 ")
+                # generate repeated sequence
+                to_pack = (ptrn_to_repeat * (gen_length/len(ptrn_to_repeat) + 1))[:gen_length]
+                return struct.pack('B'*gen_length, *to_pack)
+            else:
+                raise ValueError("Given ptrn_to_repeat argument type ({0}) is illegal.".
+                                 format(type(ptrn_to_repeat)))
+
+        def _calc_gen_length(self):
+            return self._max_pkt_size - len(self._pkt_ref)
+
+    class CTRexVM(object):
+        """
+        This class defines the TRex VM which represents how TRex will regenerate packets.
+        The packets will be regenerated based on the built packet containing this class.
+        """
+        def __init__(self):
+            """
+            Instantiate a CTRexVM object
+
+            :parameters:
+                None
+            """
+            super(CTRexPktBuilder.CTRexVM, self).__init__()
+            self.vm_variables = {}
+
+        def set_vm_var_field(self, var_name, field_name, val):
+            """
+            Set VM variable field. Only existing variables are allowed to be changed.
+
+            :parameters:
+                var_name : str
+                    a string representing the name of the VM variable to be changed.
+                field_name : str
+                    a string representing the field name of the VM variable to be changed.
+                val :
+                    a value to be applied to field_name field of the var_name VM variable.
+
+            :raises:
+                + :exc:`KeyError`, in case invalid var_name has been specified.
+                + :exc:`CTRexPktBuilder.VMVarFieldTypeError`, in case mismatch between `val` and allowed type.
+                + :exc:`CTRexPktBuilder.VMVarValueError`, in case val isn't one of allowed options of field_name.
+
+            """
+            return self.vm_variables[var_name].set_field(field_name, val)
+
+        def add_flow_man_simple(self, name, **kwargs):
+            """
+            Adds a new flow manipulation object to the VM instance.
+
+            :parameters:
+                name : str
+                    name of the manipulation, must be distinct.
+                    Example: 'source_ip_change'
+
+                **kwargs : dict
+                    optional, set flow_man fields on initialization (key = field_name, val = field_val).
+                    Must be used with legit fields, see :func:`CTRexPktBuilder.CTRexVM.CTRexVMVariable.set_field`.
+
+            :return:
+                None
+
+            :raises:
+                + :exc:`CTRexPktBuilder.VMVarNameExistsError`, in case of desired flow_man name already taken.
+                + Exceptions from :func:`CTRexPktBuilder.CTRexVM.CTRexVMVariable.set_field` method.
+                  Will rise when VM variables were misconfiguration.
+            """
+            if name not in self.vm_variables.keys():
+                self.vm_variables[name] = self.CTRexVMVariable(name)
+                # try configuring VM var attributes
+                for (field, value) in kwargs.items():
+                    self.vm_variables[name].set_field(field, value)
+            else:
+                raise CTRexPktBuilder.VMVarNameExistsError(name)
+
+        def load_flow_man(self, flow_obj):
+            """
+            Loads an outer VM variable (instruction) into current VM.
+            The outer VM variable must contain different name than existing VM variables currently registered on VM.
+
+            :parameters:
+                flow_obj : CTRexVMVariable
+                    a CTRexVMVariable to be loaded into VM variable sets.
+
+            :return:
+                list holds variables data of VM
+
+            """
+            assert isinstance(flow_obj, CTRexPktBuilder.CTRexVM.CTRexVMVariable)
+            if flow_obj.name not in self.vm_variables.keys():
+                self.vm_variables[flow_obj.name] = flow_obj
+            else:
+                raise CTRexPktBuilder.VMVarNameExistsError(flow_obj.name)
+
+        def dump(self):
+            """
+            dumps a VM variables (instructions) into an list data structure.
+
+            :parameters:
+                None
+
+            :return:
+                list holds variables data of VM
+
+            """
+            return [var.dump()
+                    for key, var in self.vm_variables.items()]
+
+        class CTRexVMVariable(object):
+            """
+            This class defines a single VM variable to be used as part of CTRexVar object.
+            """
+            VALID_SIZE = [1, 2, 4, 8]
+            VALID_OPERATION = ["inc", "dec", "random"]
+
+            def __init__(self, name):
+                """
+                Instantiate a CTRexVMVariable object
+
+                :parameters:
+                    name : str
+                        a string representing the name of the VM variable.
+                """
+                super(CTRexPktBuilder.CTRexVM.CTRexVMVariable, self).__init__()
+                self.name = name
+                self.size = 4
+                self.big_endian = True
+                self.operation = "inc"
+                self.split_by_core = False
+                self.init_value = 1
+                self.min_value = self.init_value
+                self.max_value = self.init_value
+
+            def set_field(self, field_name, val):
+                """
+                Set VM variable field. Only existing variables are allowed to be changed.
+
+                :parameters:
+                    field_name : str
+                        a string representing the field name of the VM variable to be changed.
+                    val :
+                        a value to be applied to field_name field of the var_name VM variable.
+
+                :return:
+                    None
+
+                :raises:
+                    + :exc:`CTRexPktBuilder.VMVarNameError`, in case of illegal field name.
+                    + :exc:`CTRexPktBuilder.VMVarFieldTypeError`, in case mismatch between `val` and allowed type.
+                    + :exc:`CTRexPktBuilder.VMVarValueError`, in case val isn't one of allowed options of field_name.
+
+                """
+                if not hasattr(self, field_name):
+                    raise CTRexPktBuilder.VMVarNameError(field_name)
+                elif field_name == "size":
+                    if type(val) != int:
+                        raise CTRexPktBuilder.VMVarFieldTypeError("size", int)
+                    elif val not in self.VALID_SIZE:
+                        raise CTRexPktBuilder.VMVarValueError("size", self.VALID_SIZE)
+                elif field_name == "init_value":
+                    if type(val) != int:
+                        raise CTRexPktBuilder.VMVarFieldTypeError("init_value", int)
+                elif field_name == "operation":
+                    if type(val) != str:
+                        raise CTRexPktBuilder.VMVarFieldTypeError("operation", str)
+                    elif val not in self.VALID_OPERATION:
+                        raise CTRexPktBuilder.VMVarValueError("operation", self.VALID_OPERATION)
+                elif field_name == "split_by_core":
+                    val = bool(val)
+                # update field value on success
+                setattr(self, field_name, val)
+
+            def is_valid(self):
+                if self.size not in self.VALID_SIZE:
+                    return False
+                if self.type not in self.VALID_OPERATION:
+                    return False
+                return True
+
+            def dump(self):
+                """
+                dumps a variable fields in a dictionary data structure.
+
+                :parameters:
+                    None
+
+                :return:
+                    dictionary holds variable data of VM variable
+
+                """
+                return {"ins_name": "flow_man_simple",  # VM variable dump always refers to manipulate instruction.
+                        "flow_variable_name": self.name,
+                        "object_size": self.size,
+                        # "big_endian": self.big_endian,
+                        "Operation": self.operation,
+                        "split_by_core": self.split_by_core,
+                        "init_value": self.init_value,
+                        "min_value": self.min_value,
+                        "max_value": self.max_value}
+
+    class CPacketBuildException(Exception):
+        """
+        This is the general Packet Building error exception class.
+        """
+        def __init__(self, code, message):
+            self.code = code
+            self.message = message
+
+        def __str__(self):
+            return self.__repr__()
+
+        def __repr__(self):
+            return u"[errcode:%r] %r" % (self.code, self.message)
+
+    class EmptyPacketError(CPacketBuildException):
+        """
+        This exception is used to indicate an error caused by operation performed on an empty packet.
+        """
+        def __init__(self, message=''):
+            self._default_message = 'Illegal operation on empty packet.'
+            self.message = message or self._default_message
+            super(CTRexPktBuilder.EmptyPacketError, self).__init__(-10, self.message)
+
+    class IPAddressError(CPacketBuildException):
+        """
+        This exception is used to indicate an error on the IP addressing part of the packet.
+        """
+        def __init__(self, message=''):
+            self._default_message = 'Illegal type or value of IP address has been provided.'
+            self.message = message or self._default_message
+            super(CTRexPktBuilder.IPAddressError, self).__init__(-11, self.message)
+
+    class MACAddressError(CPacketBuildException):
+        """
+        This exception is used to indicate an error on the MAC addressing part of the packet.
+        """
+        def __init__(self, message=''):
+            self._default_message = 'Illegal MAC address has been provided.'
+            self.message = message or self._default_message
+            super(CTRexPktBuilder.MACAddressError, self).__init__(-11, self.message)
+
+    class VMVarNameExistsError(CPacketBuildException):
+        """
+        This exception is used to indicate a duplicate usage of VM variable.
+        """
+        def __init__(self, name, message=''):
+            self._default_message = 'The given VM name ({0}) already exists as part of the stream.'.format(name)
+            self.message = message or self._default_message
+            super(CTRexPktBuilder.VMVarNameExistsError, self).__init__(-21, self.message)
+
+    class VMVarNameError(CPacketBuildException):
+        """
+        This exception is used to indicate that an undefined VM var field name has been accessed.
+        """
+        def __init__(self, name, message=''):
+            self._default_message = "The given VM field name ({0}) is not defined and isn't legal.".format(name)
+            self.message = message or self._default_message
+            super(CTRexPktBuilder.VMVarNameError, self).__init__(-22, self.message)
+
+    class VMVarFieldTypeError(CPacketBuildException):
+        """
+        This exception is used to indicate an illegal value has type has been given to VM variable field.
+        """
+        def __init__(self, name, ok_type, message=''):
+            self._default_message = 'The desired value of field {field_name} is of type {field_type}, \
+            and not of the allowed {allowed_type}.'.format(field_name=name,
+                                                           field_type=type(name).__name__,
+                                                           allowed_type=ok_type.__name__)
+            self.message = message or self._default_message
+            super(CTRexPktBuilder.VMVarFieldTypeError, self).__init__(-31, self.message)
+
+    class VMVarValueError(CPacketBuildException):
+        """
+        This exception is used to indicate an error an illegal value has been assigned to VM variable field.
+        """
+        def __init__(self, name, ok_opts, message=''):
+            self._default_message = 'The desired value of field {field_name} is illegal.\n \
+            The only allowed options are: {allowed_opts}.'.format(field_name=name,
+                                                                  allowed_opts=ok_opts)
+            self.message = message or self._default_message
+            super(CTRexPktBuilder.VMVarValueError, self).__init__(-32, self.message)
+
+
+if __name__ == "__main__":
+    pass