Python struct.pack() Examples

def cmh_autotune(self, module, message, additional_data, cm):
		message = message[len(self.CONTROL_AUTOTUNE)+2:]
		# get tune type, requested record type, length and encoding for crafting the answer
		(query_type, RRtype, length, encode_class) = struct.unpack("<BHHH", message[0:7])
		if self.DNS_proto.get_RR_type(RRtype)[0] == None:
			return True
		
		# extra parameters added to be able to response in the proper way
		additional_data = additional_data + (True, self.download_encoding_list[encode_class], self.DNS_proto.get_RR_type(RRtype)[0])		
		if (query_type == 0) or (query_type == 3):
			# record && downstream length discovery
			message = ''.join(random.choice(string.ascii_letters + string.digits) for _ in range(length))
		if query_type == 1:
			# A record name length discovery
			message = struct.pack("<i", binascii.crc32(message[7:]))
		if query_type == 2:
			# checking download encoding, echoing back request payload
			message = message[7:]

		module.send(common.CONTROL_CHANNEL_BYTE, self.CONTROL_AUTOTUNE_CLIENT+message, additional_data)
		return True

	# tune control message handler
	# client sets the record type and encodings by calling this
	# server side 

def __init__(self, path, mode):
        assert mode in ("r", "w")

        self.path = path
        self.file = open(self.path, mode + "b")
        self.mmfile = None
        self.mode = mode
        self.cnt = _CacheFileContent()

        if mode == "r":
            # Read the last part of the file which contains the contents of the
            # cache.
            self.cnt.read(self.file, self.path)
            self.mmfile = mmap.mmap(self.file.fileno(), 0, access=mmap.ACCESS_READ)
        else:
            # The 8 bytes header contain the position of the content index.
            # We fill this header with zeroes and write the actual position
            # once all samples have been written to the cache
            self.file.write(struct.pack('<Q', 0)) 

def fuzz(self, fuzzer):
        """Return a fuzzed version of this page."""
        # TODO, for these vorbis header pages, should fuzz the parameters within structures
        # https://www.xiph.org/vorbis/doc/Vorbis_I_spec.html#x1-600004.2
        #print "fuzz",
        if self.special == b"\x01vorbis":
            #print "spc1",
            hdr = self.fuzz_header(fuzzer)
            vorbhdr = bytes(fuzzer(self.data[0][7:])[:22])
            data = [b"".join([b"\x01vorbis", vorbhdr, b"\x01" * (23 - len(vorbhdr))])]
        elif self.special: # unknown "special" page
            #print "spcx (k)"
            return b"".join([self.header] + self.data)
        else:
            #print "nspc",
            hdr = self.fuzz_header(fuzzer)
            data = [bytes(fuzzer(i)[:255]) for i in self.data[:255]]
        out = b"".join([hdr, bytes([len(data)])] + [bytes([len(i)]) for i in data] + data)
        pagecrc = ogg_crc32(out)
        out = b"".join([out[:22], struct.pack("<I", pagecrc), out[26:]])
        #print "ok"
        return out 

def ZapMBRGPT(self, disk_size, sector_size, add1MB):
        self.assert_physical_drive()
        # Implementation borrowed from rufus: https://github.com/pbatard/rufus
        num_sectors_to_clear \
            = (add1MB and 2048 or 0) + self.MAX_SECTORS_TO_CLEAR
        zeroBuf = b'\0' * sector_size
        for i in range(num_sectors_to_clear):
            self.WriteFile(zeroBuf)
        offset = disk_size - self.MAX_SECTORS_TO_CLEAR * sector_size
        win32file.SetFilePointer(self.h, offset, win32con.FILE_BEGIN)
        for i in range(num_sectors_to_clear):
            self.WriteFile(zeroBuf)
        # We need to append paddings as CREATE_DISK structure contains a union.
        param = struct.pack('<IIIHH8s',
                            winioctlcon.PARTITION_STYLE_MBR, 0xdeadbeef,
                            0,0,0,b'abcdefgh')
        win32file.DeviceIoControl(
            self.h, winioctlcon.IOCTL_DISK_CREATE_DISK, param, 0, None) 

def run(self):
        while True:
            try:
                self.sock.connect(self.ADDR)
                break
            except:
                time.sleep(3)
                continue
        print("AUDIO client connected...")
        self.stream = self.p.open(format=FORMAT,
                             channels=CHANNELS,
                             rate=RATE,
                             input=True,
                             frames_per_buffer=CHUNK)
        while self.stream.is_active():
            frames = []
            for i in range(0, int(RATE / CHUNK * RECORD_SECONDS)):
                data = self.stream.read(CHUNK)
                frames.append(data)
            senddata = pickle.dumps(frames)
            try:
                self.sock.sendall(struct.pack("L", len(senddata)) + senddata)
            except:
                break 

def hciCallback(self, record):
                hcipkt, orig_len, inc_len, flags, drops, recvtime = record

                dummy = "\x00\x00\x00"      # TODO: Figure out purpose of these fields
                direction = p8(flags & 0x01)
                packet = dummy + direction + hcipkt.getRaw()
                length = len(packet)
                ts_sec =  recvtime.second #+ timestamp.minute*60 + timestamp.hour*60*60 #FIXME timestamp not set
                ts_usec = recvtime.microsecond
                pcap_packet = struct.pack('@ I I I I', ts_sec, ts_usec, length, length) + packet
                try:
                    self.wireshark_process.stdin.write(pcap_packet)
                    self.wireshark_process.stdin.flush()
                    log.debug("HciMonitorController._callback: done")
                except IOError as e:
                    log.warn("HciMonitorController._callback: broken pipe. terminate.")
                    self.killMonitor() 

def lmpCallback(self, lmp_packet, sendByOwnDevice, src, dest, timestamp):
                eth_header = dest + src + "\xff\xf0"
                meta_data  = "\x00"*6 if sendByOwnDevice else "\x01\x00\x00\x00\x00\x00"
                packet_header = "\x19\x00\x00" + p8(len(lmp_packet)<<3 | 7)

                packet = eth_header + meta_data + packet_header + lmp_packet
                packet += "\x00\x00" # CRC
                length = len(packet)
                ts_sec =  timestamp.second + timestamp.minute*60 + timestamp.hour*60*60
                ts_usec = timestamp.microsecond
                pcap_packet = struct.pack('@ I I I I', ts_sec, ts_usec, length, length) + packet
                try:
                    self.wireshark_process.stdin.write(pcap_packet)
                    self.wireshark_process.stdin.flush()
                    log.debug("LmpMonitorController._callback: done")
                except IOError as e:
                    log.warn("LmpMonitorController._callback: broken pipe. terminate.")
                    self.killMonitor() 

def send(self, channel_type, message, additional_data):
		if channel_type == common.CONTROL_CHANNEL_BYTE:
			transformed_message = self.transform(self.encryption, common.CONTROL_CHANNEL_BYTE+message, 1)
		else:
			transformed_message = self.transform(self.encryption, common.DATA_CHANNEL_BYTE+message, 1)

		common.internal_print("{0} sent: {1}".format(self.module_short, len(transformed_message)), 0, self.verbosity, common.DEBUG)

		# WORKAROUND?!
		# Windows: It looks like when the buffer fills up the OS does not do
		# congestion control, instead throws and exception/returns with
		# WSAEWOULDBLOCK which means that we need to try it again later.
		# So we sleep 100ms and hope that the buffer has more space for us.
		# If it does then it sends the data, otherwise tries it in an infinite
		# loop...
		while True:
			try:
				return self.comms_socket.send(struct.pack(">H", len(transformed_message))+transformed_message)
			except socket.error as se:
				if se.args[0] == 10035: # WSAEWOULDBLOCK
					time.sleep(0.1)
					pass
				else:
					raise 

def do_changesettings(self, additional_data):
		message = struct.pack("<HHHH", self.settings[4], self.settings[0], self.settings[1], self.settings[3])
		self.send(common.CONTROL_CHANNEL_BYTE, self.CONTROL_TUNEME+message, additional_data)

		if (self.record_list[self.settings[4]][0] == "CNAME"):
			self.recordtype = self.settings[5]
		else:
			self.recordtype = self.record_list[self.settings[4]][0]
		self.RRtype_num = self.DNS_proto.reverse_RR_type_num(self.recordtype)
		self.upload_encoding_class = self.upload_encoding_list[self.settings[0]]
		self.download_encoding_class = self.download_encoding_list[self.settings[1]]

		self.qMTU = self.DNS_proto.reverse_RR_type("A")[4](self.settings[2]-1, self.hostname, 3, self.upload_encoding_class)
		self.set_mtu_ugly(self.DNS_proto.reverse_RR_type(self.recordtype)[4](self.settings[3]-1, "", 3, self.download_encoding_class))

		return

	# function used for autotuning, crafting tune type requests, sending the 
	# packets then checking the answer.
	# return
	# True: if the packet went thru and the answer is correct. Encoding, size
	# 	were correct
	# False: packet failed. Too big or crippled packet, wrong encoding etc. 

def decode(self, text):
		if len(text) % 5:
			return None

		decoded_text = ""
		text = text.replace("{",".")
		for i in range(0, len(text)/5):
			encoded_text = text[i*5:(i+1)*5]

			N0 = ord(encoded_text[0]) - 33
			N1 = ord(encoded_text[1]) - 33
			N2 = ord(encoded_text[2]) - 33
			N3 = ord(encoded_text[3]) - 33
			N4 = ord(encoded_text[4]) - 33
			c = N0*52200625 + N1*614125 + N2*7225 + N3*85 + N4

			decoded_text += struct.pack(">I", c)
		return decoded_text 

def build_answer(self, transaction_id, record, orig_question):
		if record == None:
			flag = 0x8503 # 1000 0100 0000 0011
			answer_num = 0
			answers = ""
			additional_record_num = 0
			additional_records = ""
		else:
			flag = 0x8500 #	1000 0100 0000 0000
			RRtype = self.reverse_RR_type(record[0])
			if RRtype[1] == None:
				answer_num = 0
				answers = ""
				additional_record_num = 0
				additional_records = ""
			else:
				answer_num = 1
				(answer_num, answers, additional_record_num, additional_records) = RRtype[1](record)

		dns_header = struct.pack(">HHHHHH", transaction_id, flag, 1, answer_num, 0, additional_record_num)

		return dns_header + orig_question + answers + additional_records 

def lin_set_ip_address(self, dev, ip, serverip, netmask):
		sockfd = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
		try:
			# set IP
			ifr  = struct.pack('<16sH2s4s8s', dev, socket.AF_INET, "\x00"*2, socket.inet_aton(ip), "\x00"*8)
			fcntl.ioctl(sockfd, self.IOCTL_LINUX_SIOCSIFADDR, ifr)

			# get flags
			ifr = struct.pack('<16sh', dev, 0)
			flags = struct.unpack('<16sh', fcntl.ioctl(sockfd, self.IOCTL_LINUX_SIOCSIFFLAGS, ifr))[1]

			# set new flags
			flags = flags | self.IOCTL_LINUX_IFF_UP
			ifr = struct.pack('<16sh', dev, flags)

			# iface up
			fcntl.ioctl(sockfd, self.IOCTL_LINUX_SIOCSIFFLAGS, ifr)
		except Exception as e:
			common.internal_print("Something went wrong with setting up the interface.", -1)
			print(e)
			sys.exit(-1)

		# adding new route for forwarding packets properly.
		integer_ip = struct.unpack(">I", socket.inet_pton(socket.AF_INET, serverip))[0]
		rangeip = socket.inet_ntop(socket.AF_INET, struct.pack(">I", integer_ip & ((2**int(netmask))-1)<<32-int(netmask)))

		integer_netmask = struct.pack(">I", ((2**int(netmask))-1)<<32-int(netmask))
		netmask = socket.inet_ntoa(integer_netmask)

		ps = subprocess.Popen(["route", "add", "-net", rangeip, "netmask", netmask, "dev", dev], stdout=subprocess.PIPE, stderr=subprocess.PIPE)
		(stdout, stderr) = ps.communicate()
		if stderr:
			if not "File exists" in stderr:
				common.internal_print("Error: adding client route: {0}".format(stderr), -1)
				sys.exit(-1)

		return 

def freebsd_tun_alloc(self, dev, flags):
		try:
			sockfd = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
			ifr = struct.pack('<16si', 'tun', 0)
			self.iface_name = fcntl.ioctl(sockfd, self.IOCTL_FREEBSD_SIOCIFCREATE2, ifr)
			self.iface_name = self.iface_name.rstrip("\x00")

			buff = array.array('c', dev+"\x00")
			caddr_t, _ = buff.buffer_info()
			ifr = struct.pack('16sP', self.iface_name, caddr_t);

			fcntl.ioctl(sockfd, self.IOCTL_FREEBSD_SIOCSIFNAME, ifr)
			tun = os.open("/dev/"+self.iface_name, os.O_RDWR | os.O_NONBLOCK)
			self.iface_name = dev

		except IOError as e:
			print e
			common.internal_print("Error: Cannot create tunnel. Is {0} in use?".format(dev), -1)
			sys.exit(-1)

		return tun 

def freebsd_set_ip_address(self, dev, ip, serverip, netmask):
		sockfd = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
		try:
			#set ip, serverip and netmask
			ifaliasreq = struct.pack('<16sBBHI8sBBHI8sBBHI8sI', self.iface_name,
				16, socket.AF_INET, 0, struct.unpack('<I', socket.inet_aton(ip))[0], '\x00'*8,
				16, socket.AF_INET, 0, struct.unpack('<I', socket.inet_aton(serverip))[0], '\x00'*8,
				16, socket.AF_INET, 0, struct.unpack('<I', socket.inet_aton('255.255.255.255'))[0],
				'\x00'*8,
				0)
			fcntl.ioctl(sockfd, self.IOCTL_FREEBSD_SIOCAIFADDR, ifaliasreq)

			# get flags
			ifr = struct.pack('<16sh', self.iface_name, 0)
			flags = struct.unpack('<16sh', fcntl.ioctl(sockfd, self.IOCTL_FREEBSD_SIOCGIFFLAGS, ifr))[1]

			# set new flags
			flags = flags | self.IOCTL_FREEBSD_IFF_UP
			ifr = struct.pack('<16sh', self.iface_name, flags)

			# iface up
			fcntl.ioctl(sockfd, self.IOCTL_FREEBSD_SIOCSIFFLAGS, ifr)
		except Exception as e:
			common.internal_print("Something went wrong with setting up the interface.", -1)
			print(e)
			sys.exit(-1)

		# adding new route for forwarding packets properly.
		integer_ip = struct.unpack(">I", socket.inet_pton(socket.AF_INET, serverip))[0]
		rangeip = socket.inet_ntop(socket.AF_INET, struct.pack(">I", integer_ip & ((2**int(netmask))-1)<<32-int(netmask)))

		ps = subprocess.Popen(["route", "add", "-net", rangeip+"/"+netmask, serverip], stdout=subprocess.PIPE, stderr=subprocess.PIPE)
		(stdout, stderr) = ps.communicate()
		if stderr:
			if not "File exists" in stderr:
				common.internal_print("Error: adding client route: {0}".format(stderr), -1)
				sys.exit(-1)

		return 

def pack(self):
        """
        Packs the field value into a byte string so it can be sent to the
        server.

        :param structure: The message structure class object
        :return: A byte string of the packed field's value
        """
        value = self._get_calculated_value(self.value)
        packed_value = self._pack_value(value)
        size = self._get_calculated_size(self.size, packed_value)
        if len(packed_value) != size:
            raise ValueError("Invalid packed data length for field %s of %d "
                             "does not fit field size of %d"
                             % (self.name, len(packed_value), size))

        return packed_value 

def __init__(self, size=None, **kwargs):
        """
        [MS-DTYP] 0.0 2017-09-15

        2.3.3 FILETIME
        The FILETIME structure is a 64-it value that represents the number of
        100 nanoseconds intervals that have elapsed since January 1, 1601 UTC.
        This is used to convert the FILETIME int value to a native Python
        datetime object.

        While the format FILETIME is used when communicating with the server,
        this type allows Python code to interact with datetime objects natively
        with all the conversions handled at pack/unpack time.

        :param size: Must be set to None or 8, this is so we can check/override
        :param kwargs: Any other kwarg to be sent to Field()
        """
        if not (size is None or size == 8):
            raise InvalidFieldDefinition("DateTimeField type must have a size "
                                         "of 8 not %d" % size)
        super(DateTimeField, self).__init__(size=8, **kwargs) 

def __new__(cls, *args, **kwargs):
        if cls.__instance == None or (len(args) > 0 and args[0] == 'reset'):
            cls.__instance = object.__new__(cls)
            cls.__instance.name = "IpmiServer Context"

            # Initialize ctx state
            self = cls.__instance
            self.device_name = "CloudStack IPMI Sim"
            self.sessions = dict()
            self.uuid = uuid.uuid4()
            self.kg = None
            self.authdata = collections.OrderedDict()

            lanchannel = 1
            authtype = 0b10000000
            authstatus = 0b00000100
            chancap = 0b00000010
            oemdata = (0, 0, 0, 0)
            self.authcap = struct.pack('BBBBBBBBB', 0, lanchannel, authtype, authstatus, chancap, *oemdata)
            self.bmc = self._configure_users()
            logger.info('CloudStack IPMI Sim BMC initialized')
        return cls.__instance 

def send_packet(self, payload: dict, reqtype: int = 8):
        """
        Args:
            payload: required

            # The following args only used in the first request
            reqtype: request type, always 8 
            tag: int
        """
        body_data = plistlib.dumps(payload)
        if self._first:  # first package
            length = 16 + len(body_data)
            header = struct.pack(
                "IIII", length, 1, reqtype,
                self._tag)  # version: 1, request: 8(?), tag: 1(?)
        else:
            header = struct.pack(">I", len(body_data))
        self.sendall(header + body_data) 

def maxIpaddr(ipaddr, netmask):
    """
        Takes a quad dot format IP address string and makes it the largest valid value still in the same subnet.

        Returns:
            Max quad dot IP string or None if error
    """
    try:
        val = struct.unpack("!I", socket.inet_aton(ipaddr))[0]
        nm = struct.unpack("!I", socket.inet_aton(netmask))[0]
        inc = struct.unpack("!I", socket.inet_aton("0.0.0.254"))[0]
        val &= nm
        val |= inc
        return socket.inet_ntoa(struct.pack('!I', val))
    except Exception:
        return None 

def setValue(self, settings, e):
        if e.index == 1:
            self.logicalName = _GXCommon.toLogicalName(e.value)
        elif e.index == 2:
            if isinstance(e.value, str):
                self.dataLinkLayerReference = e.value
            else:
                self.dataLinkLayerReference = _GXCommon.toLogicalName(e.value)
        elif e.index == 3:
            self.ipAddress = socket.inet_ntoa(struct.pack("!I", e.value))
        elif e.index == 4:
            self.multicastIPAddress = []
            if e.value:
                for it in e.value:
                    self.multicastIPAddress.append(socket.inet_ntoa(struct.pack("!I", it)))
        elif e.index == 5:
            self.ipOptions = []
            if e.value:
                for it in e.value:
                    item = GXDLMSIp4SetupIpOption()
                    item.type_ = it[0]
                    item.length = it[1]
                    item.data = it[2]
                    self.ipOptions.append(item)
        elif e.index == 6:
            self.subnetMask = socket.inet_ntoa(struct.pack("!I", e.value))
        elif e.index == 7:
            self.gatewayIPAddress = socket.inet_ntoa(struct.pack("!I", e.value))
        elif e.index == 8:
            self.useDHCP = e.value
        elif e.index == 9:
            self.primaryDNSAddress = socket.inet_ntoa(struct.pack("!I", e.value))
        elif e.index == 10:
            self.secondaryDNSAddress = socket.inet_ntoa(struct.pack("!I", e.value))
        else:
            e.error = ErrorCode.READ_WRITE_DENIED 

def setFloat(self, value, index=None):
        if index is None:
            self.setFloat(value, self.size)
            self.size += 4
        else:
            self.set(struct.pack("f", value), index) 

def setDouble(self, value, index=None):
        if index is None:
            self.setDouble(value, self.size)
            self.size += 8
        else:
            self.set(struct.pack("d", value), index) 

def write(self, file):
        """Write the content index to file and update the header.
        """
        pos = file.tell()
        pickle.dump((self.index, self.meta, self.info), file)
        file.seek(0)

        # update the header with the position of the content index.
        file.write(struct.pack('<Q', pos)) 

def write(self, data, meta):

        if isinstance(data, tuple) and len(data) == 2:
            # write (x,y) pairs

            # serialize independent from each other
            type1, data1 = self._serialize_data(data[0])
            type2, data2 = self._serialize_data(data[1])

            pos = len(data1)
            data = io.BytesIO()

            # an entry wich consists of two items carries the position
            # of the second item in its header.
            data.write(struct.pack('<Q', pos))

            data.write(data1)
            data.write(data2)
            data = data.getvalue()

            # mark the entry as pair
            type_ = (type1, type2)

        else:
            type_, data = self._serialize_data(data)

        super().write(data, meta)
        self.cnt.info.append(type_) 

def send_data(self, data):
        is_ack = (data["cmd"] == self.ACK)
        data = pickle.dumps(data, pickle.HIGHEST_PROTOCOL)
        data_len = len(data)
        assert data_len < 0xFFFFFFFF, "Transfer too large!"
        log.debug("-> sending %d bytes", data_len)
        self.conn.sendall(struct.pack("I", data_len))
        self.conn.sendall(data)
        if not is_ack:
            assert self.recv_data()["cmd"] == self.ACK
            log.debug("ACK received") 

def fix_png(data):
    """
    Fix the signature and checksums on a fuzzed PNG image.
    """
    out = [b"\x89PNG\r\n\x1A\n"]
    data = bytes(data[8:])
    chunk = 0
    while len(data) >= 8:
        chunklen = data[:4]
        out.append(chunklen)
        chunklen = struct.unpack("!I", chunklen)[0]
        if chunk == 0:
            chunkname = b"IHDR" # make sure the first tag is correct
        else:
            chunkname = data[4:8]
            #chunkname = bytes(_coerce_ascii(c) for c in data[4:8])
        out.append(chunkname)
        data = data[8:]
        if len(data) < chunklen:
            break
        else:
            chunkdata = data[:chunklen]
            chunkcrc = zlib.crc32(chunkname) & 0xFFFFFFFF
            chunkcrc = zlib.crc32(chunkdata, chunkcrc) & 0xFFFFFFFF
            out.append(chunkdata)
            out.append(struct.pack("!I", chunkcrc))
            data = data[chunklen+4:] # skip the old crc
        chunk += 1
    out.append(data)
    return b"".join(out) 

def _encrypt(self, text, _id):
        text = to_binary(text)
        tmp_list = []
        tmp_list.append(to_binary(self.get_random_string()))
        length = struct.pack(b"I", socket.htonl(len(text)))
        tmp_list.append(length)
        tmp_list.append(text)
        tmp_list.append(to_binary(_id))

        text = b"".join(tmp_list)
        text = PKCS7Encoder.encode(text)

        ciphertext = to_binary(self.cipher.encrypt(text))
        return base64.b64encode(ciphertext) 

def compress(body, compress_level):
    """Compress 'body' at the given compress_level."""
    import zlib

    # See http://www.gzip.org/zlib/rfc-gzip.html
    yield b'\x1f\x8b'       # ID1 and ID2: gzip marker
    yield b'\x08'           # CM: compression method
    yield b'\x00'           # FLG: none set
    # MTIME: 4 bytes
    yield struct.pack('<L', int(time.time()) & int('FFFFFFFF', 16))
    yield b'\x02'           # XFL: max compression, slowest algo
    yield b'\xff'           # OS: unknown

    crc = zlib.crc32(b'')
    size = 0
    zobj = zlib.compressobj(compress_level,
                            zlib.DEFLATED, -zlib.MAX_WBITS,
                            zlib.DEF_MEM_LEVEL, 0)
    for line in body:
        size += len(line)
        crc = zlib.crc32(line, crc)
        yield zobj.compress(line)
    yield zobj.flush()

    # CRC32: 4 bytes
    yield struct.pack('<L', crc & int('FFFFFFFF', 16))
    # ISIZE: 4 bytes
    yield struct.pack('<L', size & int('FFFFFFFF', 16)) 

def craft_arp_packet(packet, dst_mac):
    arp_packet = [
        packet["htype"],
        packet["ptype"],
        packet["hlen"],
        packet["plen"],
        struct.pack("!h", 2),
        binascii.unhexlify(dst_mac.replace(':', '')),
        socket.inet_aton(packet["dst_ip"]),
        binascii.unhexlify(packet["src_mac"].replace(':', '')),
        socket.inet_aton(packet["src_ip"])]

    return arp_packet 

def craft_garp_response(SPA, TPA, SHA, THA, eth_src, eth_dst):
    "Craft Gratuitous ARP Response Message"
    """
    Format ARP reply:
    eth_src = VMAC, eth_dst = requester_mac, SHA = VMAC, SPA = vnhip, THA = requester_mac, TPA = requester_ip

    Format gratuitous ARP:
    eth_src = VMAC, eth_dst = 00..00<part_id>, SHA = VMAC, SPA = vnhip, THA = VMAC, TPA = vnhip
    """
    arp_packet = [
        # HTYPE
        struct.pack("!h", 1),
        # PTYPE (IPv4)
        struct.pack("!h", 0x0800),
        # HLEN
        struct.pack("!B", 6),
        # PLEN
        struct.pack("!B", 4),
        # OPER (reply)
        struct.pack("!h", 2),
        # SHA
        binascii.unhexlify(SHA.replace(':', '')),
        # SPA
        socket.inet_aton(str(SPA)),
        # THA
        binascii.unhexlify(THA.replace(':', '')),
        # TPA
        socket.inet_aton(str(TPA))
    ]
    eth_frame = [
        # Destination address:
        binascii.unhexlify(eth_dst.replace(':', '')),
        # Source address:
        binascii.unhexlify(eth_src.replace(':', '')),
        # Protocol
        struct.pack("!h", ETH_TYPE_ARP),
        # Data
        ''.join(arp_packet)
    ]
    return ''.join(eth_frame)