iplib.py

"""
iplib module.

The representation of IPv4 addresses and netmasks.
You can use this module to convert amongst many different notations
and to manage couples of address/netmask in the CIDR notation.

  Copyright 2001-2018 Davide Alberani <da@erlug.linux.it>

All rights reserved.

Redistribution and use in source and binary forms, with or without
modification, are permitted provided that the following conditions are met:
    * Redistributions of source code must retain the above copyright
      notice, this list of conditions and the following disclaimer.
    * Redistributions in binary form must reproduce the above copyright
      notice, this list of conditions and the following disclaimer in the
      documentation and/or other materials provided with the distribution.
    * Neither the name of the copyright holder nor the
      names of its contributors may be used to endorse or promote products
      derived from this software without specific prior written permission.

THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDER ``AS IS'' AND ANY
EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER BE LIABLE FOR ANY
DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
(INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
(INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
"""

__version__ = '1.2.1'


# Notation types (with an example in the comment).
# You can use these constants when you have to specify a notation style.
IP_UNKNOWN = NM_UNKNOWN = 0
IP_DOT = NM_DOT = 1 # 192.168.0.42
IP_HEX = NM_HEX = 2 # 0xC0A8002A
IP_BIN = NM_BIN = 3 # 0o30052000052
IP_OCT = NM_OCT = 4 # 11000000101010000000000000101010
IP_DEC = NM_DEC = 5 # 3232235562
NM_BITS = 6 # 26
NM_WILDCARD = 7 # 0.0.0.63

# Map notations with one or more strings.
# You can use these constant strings when you have to specify a notation
# style, instead of using numeric values.
NOTATION_MAP = {
    IP_DOT:         ('dotted decimal', 'dotted', 'quad', 'dot', 'dotted quad'),
    IP_HEX:         ('hexadecimal', 'hex'),
    IP_BIN:         ('binary', 'bin'),
    IP_OCT:         ('octal', 'oct'),
    IP_DEC:         ('decimal', 'dec'),
    NM_BITS:        ('bits', 'bit', 'cidr'),
    NM_WILDCARD:    ('wildcard bits', 'wildcard'),
    IP_UNKNOWN:     ('unknown', 'unk')
}
_NOTATION_KEYS = dict([(key, key) for key in list(NOTATION_MAP.keys())])
for key, values in list(NOTATION_MAP.items()):
    for value in values:
        _NOTATION_KEYS[value] = key


def _get_notation(notation):
    """Given a numeric value or string value, returns one in IP_DOT, IP_HEX,
    IP_BIN, etc., or None if unable to convert to the internally
    used numeric convention."""
    return _NOTATION_KEYS.get(notation, None)


def p_notation(notation):
    """Return a string representing the given notation."""
    return NOTATION_MAP[_get_notation(notation) or IP_UNKNOWN][0]


# This dictionary maps NM_BITS to NM_DEC values.
# NOTE: /31 is a valid netmask; see RFC3021 (courtesy of Lars Erik Gullerud).
VALID_NETMASKS = {0: 0, 1: 2147483648, 2: 3221225472, 3: 3758096384,
                  4: 4026531840, 5: 4160749568, 6: 4227858432,
                  7: 4261412864, 8: 4278190080, 9: 4286578688,
                  10: 4290772992, 11: 4292870144, 12: 4293918720,
                  13: 4294443008, 14: 4294705152, 15: 4294836224,
                  16: 4294901760, 17: 4294934528, 18: 4294950912,
                  19: 4294959104, 20: 4294963200, 21: 4294965248,
                  22: 4294966272, 23: 4294966784, 24: 4294967040,
                  25: 4294967168, 26: 4294967232, 27: 4294967264,
                  28: 4294967280, 29: 4294967288, 30: 4294967292,
                  31: 4294967294, 32: 4294967295}
_NETMASKS_VALUES = list(VALID_NETMASKS.values())
_NETMASKS_INV = dict([(value, key) for key, value in list(VALID_NETMASKS.items())])


# - Functions used to check if an address or a netmask is in a given notation.

def is_dot(ip):
    """Return true if the IP address is in dotted decimal notation."""
    octets = str(ip).split('.')
    if len(octets) != 4:
        return False
    for i in octets:
        try:
            val = int(i)
        except ValueError:
            return False
        if val > 255 or val < 0:
            return False
    return True


def is_hex(ip):
    """Return true if the IP address is in hexadecimal notation."""
    try:
        dec = int(str(ip), 16)
    except (TypeError, ValueError):
        return False
    if dec > 0xFFFFFFFF or dec < 0:
        return False
    return True


def is_bin(ip):
    """Return true if the IP address is in binary notation."""
    try:
        ip = str(ip)
        if len(ip) != 32:
            return False
        dec = int(ip, 2)
    except (TypeError, ValueError):
        return False
    if dec > 4294967295 or dec < 0:
        return False
    return True


def is_oct(ip):
    """Return true if the IP address is in octal notation."""
    try:
        dec = int(str(ip), 8)
    except (TypeError, ValueError):
        return False
    if dec > 0o37777777777 or dec < 0:
        return False
    return True


def is_dec(ip):
    """Return true if the IP address is in decimal notation."""
    try:
        dec = int(str(ip))
    except ValueError:
        return False
    if dec > 4294967295 or dec < 0:
        return False
    return True


def _check_nm(nm, notation):
    """Function internally used to check if the given netmask
    is of the specified notation."""
    # Convert to decimal, and check if it's in the list of valid netmasks.
    _NM_CHECK_FUNCT = {
        NM_DOT: _dot_to_dec,
        NM_HEX: _hex_to_dec,
        NM_BIN: _bin_to_dec,
        NM_OCT: _oct_to_dec,
        NM_DEC: _dec_to_dec_long}
    try:
        dec = _NM_CHECK_FUNCT[notation](nm, check=True)
    except ValueError:
        return False
    if dec in _NETMASKS_VALUES:
        return True
    return False


def is_dot_nm(nm):
    """Return true if the netmask is in dotted decimal notatation."""
    return _check_nm(nm, NM_DOT)


def is_hex_nm(nm):
    """Return true if the netmask is in hexadecimal notatation."""
    return _check_nm(nm, NM_HEX)


def is_bin_nm(nm):
    """Return true if the netmask is in binary notatation."""
    return _check_nm(nm, NM_BIN)


def is_oct_nm(nm):
    """Return true if the netmask is in octal notatation."""
    return _check_nm(nm, NM_OCT)


def is_dec_nm(nm):
    """Return true if the netmask is in decimal notatation."""
    return _check_nm(nm, NM_DEC)


def is_bits_nm(nm):
    """Return true if the netmask is in bits notatation."""
    try:
        bits = int(str(nm))
    except ValueError:
        return False
    if bits > 32 or bits < 0:
        return False
    return True


def is_wildcard_nm(nm):
    """Return true if the netmask is in wildcard bits notatation."""
    try:
        dec = 0xFFFFFFFF - _dot_to_dec(nm, check=True)
    except ValueError:
        return False
    if dec in _NETMASKS_VALUES:
        return True
    return False


# - Functions used to convert various notation to/from decimal notation.

def _dot_to_dec(ip, check=True):
    """Dotted decimal notation to decimal conversion."""
    if check and not is_dot(ip):
        raise ValueError('_dot_to_dec: invalid IP: "%s"' % ip)
    octets = str(ip).split('.')
    dec = 0
    dec |= int(octets[0]) << 24
    dec |= int(octets[1]) << 16
    dec |= int(octets[2]) << 8
    dec |= int(octets[3])
    return dec


def _dec_to_dot(ip):
    """Decimal to dotted decimal notation conversion."""
    first = int((ip >> 24) & 255)
    second = int((ip >> 16) & 255)
    third = int((ip >> 8) & 255)
    fourth = int(ip & 255)
    return '%d.%d.%d.%d' % (first, second, third, fourth)


def _hex_to_dec(ip, check=True):
    """Hexadecimal to decimal conversion."""
    if check and not is_hex(ip):
        raise ValueError('_hex_to_dec: invalid IP: "%s"' % ip)
    if isinstance(ip, int):
        ip = hex(ip)
    return int(str(ip), 16)


def _dec_to_hex(ip):
    """Decimal to hexadecimal conversion."""
    return hex(ip)


def _oct_to_dec(ip, check=True):
    """Octal to decimal conversion."""
    if check and not is_oct(ip):
        raise ValueError('_oct_to_dec: invalid IP: "%s"' % ip)
    if isinstance(ip, int):
        ip = oct(ip)
    return int(str(ip), 8)


def _dec_to_oct(ip):
    """Decimal to octal conversion."""
    return oct(ip)


def _bin_to_dec(ip, check=True):
    """Binary to decimal conversion."""
    if check and not is_bin(ip):
        raise ValueError('_bin_to_dec: invalid IP: "%s"' % ip)
    if isinstance(ip, int):
        ip = str(ip)
    return int(str(ip), 2)


def _BYTES_TO_BITS():
    """Generate a table to convert a whole byte to binary.
    This code was taken from the Python Cookbook, 2nd edition - O'Reilly."""
    the_table = 256*[None]
    bits_per_byte = list(range(7, -1, -1))
    for n in range(256):
        l = n
        bits = 8*[None]
        for i in bits_per_byte:
            bits[i] = '01'[n & 1]
            n >>= 1
        the_table[l] = ''.join(bits)
    return the_table


_BYTES_TO_BITS = _BYTES_TO_BITS()


def _dec_to_bin(ip):
    """Decimal to binary conversion."""
    bits = []
    while ip:
        bits.append(_BYTES_TO_BITS[ip & 255])
        ip >>= 8
    bits.reverse()
    return ''.join(bits) or 32*'0'


def _dec_to_dec_long(ip, check=True):
    """Decimal to decimal (long) conversion."""
    if check and not is_dec(ip):
        raise ValueError('_dec_to_dec: invalid IP: "%s"' % ip)
    return int(str(ip))


def _dec_to_dec_str(ip):
    """Decimal to decimal (string) conversion."""
    return str(ip)


def _bits_to_dec(nm, check=True):
    """Bits to decimal conversion."""
    if check and not is_bits_nm(nm):
        raise ValueError('_bits_to_dec: invalid netmask: "%s"' % nm)
    bits = int(str(nm))
    return VALID_NETMASKS[bits]


def _dec_to_bits(nm):
    """Decimal to bits conversion."""
    return str(_NETMASKS_INV[nm])


def _wildcard_to_dec(nm, check=False):
    """Wildcard bits to decimal conversion."""
    if check and not is_wildcard_nm(nm):
        raise ValueError('_wildcard_to_dec: invalid netmask: "%s"' % nm)
    return 0xFFFFFFFF - _dot_to_dec(nm, check=False)


def _dec_to_wildcard(nm):
    """Decimal to wildcard bits conversion."""
    return _dec_to_dot(0xFFFFFFFF - nm)


# - Functions used to detect the notation of an IP address or netmask.

_CHECK_FUNCT = {
    IP_DOT: (is_dot, is_dot_nm),
    IP_HEX: (is_hex, is_hex_nm),
    IP_BIN: (is_bin, is_bin_nm),
    IP_OCT: (is_oct, is_oct_nm),
    IP_DEC: (is_dec, is_dec_nm),
    NM_BITS: (lambda: False, is_bits_nm),
    NM_WILDCARD: (lambda: False, is_wildcard_nm)
}
_CHECK_FUNCT_KEYS = list(_CHECK_FUNCT.keys())


def _is_notation(ip, notation, _isnm):
    """Internally used to check if an IP/netmask is in the given notation."""
    notation_orig = notation
    notation = _get_notation(notation)
    if notation not in _CHECK_FUNCT_KEYS:
        raise ValueError('_is_notation: unkown notation: "%s"' % notation_orig)
    return _CHECK_FUNCT[notation][_isnm](ip)


def is_notation(ip, notation):
    """Return true if the given address is in the given notation."""
    return _is_notation(ip, notation, _isnm=False)


def is_notation_nm(nm, notation):
    """Return true if the given netmask is in the given notation."""
    return _is_notation(nm, notation, _isnm=True)


def _detect(ip, _isnm):
    """Function internally used to detect the notation of the
    given IP or netmask."""
    ip = str(ip)
    if len(ip) > 1:
        if ip[0:2] == '0x':
            if _CHECK_FUNCT[IP_HEX][_isnm](ip):
                return IP_HEX
        elif ip[0] == '0':
            if _CHECK_FUNCT[IP_OCT][_isnm](ip):
                return IP_OCT
    if _CHECK_FUNCT[IP_DOT][_isnm](ip):
        return IP_DOT
    elif _isnm and _CHECK_FUNCT[NM_BITS][_isnm](ip):
        return NM_BITS
    elif _CHECK_FUNCT[IP_DEC][_isnm](ip):
        return IP_DEC
    elif _isnm and _CHECK_FUNCT[NM_WILDCARD][_isnm](ip):
        return NM_WILDCARD
    elif _CHECK_FUNCT[IP_BIN][_isnm](ip):
        return IP_BIN
    return IP_UNKNOWN


def detect(ip):
    """Detect the notation of an IP address.

    @param ip: the IP address.
    @type ip: integers, strings or object with an appropriate __str()__ method.
    @return: one of the IP_* constants; IP_UNKNOWN if undetected."""
    return _detect(ip, _isnm=False)


def detect_nm(nm):
    """Detect the notation of a netmask.
    @param nm: the netmask.
    @type nm: integers, strings or object with an appropriate __str()__ method.
    @return: one of the NM_* constants; NM_UNKNOWN if undetected."""
    return _detect(nm, _isnm=True)


def p_detect(ip):
    """Return the notation of an IP address (string)."""
    return NOTATION_MAP[detect(ip)][0]


def p_detect_nm(nm):
    """Return the notation of a netmask (string)."""
    return NOTATION_MAP[detect_nm(nm)][0]


def _convert(ip, notation, inotation, _check, _isnm):
    """Internally used to convert IPs and netmasks to other notations."""
    inotation_orig = inotation
    notation_orig = notation
    inotation = _get_notation(inotation)
    notation = _get_notation(notation)
    if inotation is None:
        raise ValueError('_convert: unknown input notation: "%s"' % inotation_orig)
    if notation is None:
        raise ValueError('_convert: unknown output notation: "%s"' % notation_orig)
    docheck = _check or False
    if inotation == IP_UNKNOWN:
        inotation = _detect(ip, _isnm)
        if inotation == IP_UNKNOWN:
            raise ValueError('_convert: unable to guess input notation or invalid value')
        if _check is None:
            docheck = True
    # We _always_ check this case later.
    if _isnm:
        docheck = False
    dec = 0
    if inotation == IP_DOT:
        dec = _dot_to_dec(ip, docheck)
    elif inotation == IP_HEX:
        dec = _hex_to_dec(ip, docheck)
    elif inotation == IP_BIN:
        dec = _bin_to_dec(ip, docheck)
    elif inotation == IP_OCT:
        dec = _oct_to_dec(ip, docheck)
    elif inotation == IP_DEC:
        dec = _dec_to_dec_long(ip, docheck)
    elif _isnm and inotation == NM_BITS:
        dec = _bits_to_dec(ip, docheck)
    elif _isnm and inotation == NM_WILDCARD:
        dec = _wildcard_to_dec(ip, docheck)
    else:
        raise ValueError('_convert: unknown IP/netmask notation: "%s"' % inotation_orig)
    # Ensure this is a valid netmask.
    if _isnm and dec not in _NETMASKS_VALUES:
        raise ValueError('_convert: invalid netmask: "%s"' % ip)
    if notation == IP_DOT:
        return _dec_to_dot(dec)
    elif notation == IP_HEX:
        return _dec_to_hex(dec)
    elif notation == IP_BIN:
        return _dec_to_bin(dec)
    elif notation == IP_OCT:
        return _dec_to_oct(dec)
    elif notation == IP_DEC:
        return _dec_to_dec_str(dec)
    elif _isnm and notation == NM_BITS:
        return _dec_to_bits(dec)
    elif _isnm and notation == NM_WILDCARD:
        return _dec_to_wildcard(dec)
    else:
        raise ValueError('convert: unknown notation: "%s"' % notation_orig)


def convert(ip, notation=IP_DOT, inotation=IP_UNKNOWN, check=True):
    """Convert among IP address notations.

    Given an IP address, this function returns the address
    in another notation.

    @param ip: the IP address.
    @type ip: integers, strings or object with an appropriate __str()__ method.

    @param notation: the notation of the output (default: IP_DOT).
    @type notation: one of the IP_* constants, or the equivalent strings.

    @param inotation: force the input to be considered in the given notation
                    (default the notation of the input is autodetected).
    @type inotation: one of the IP_* constants, or the equivalent strings.

    @param check: force the notation check on the input.
    @type check: True force the check, False force not to check and None
                do the check only if the inotation is unknown.

    @return: a string representing the IP in the selected notation.

    @raise ValueError: raised when the input is in unknown notation."""
    return _convert(ip, notation, inotation, _check=check, _isnm=False)


def convert_nm(nm, notation=IP_DOT, inotation=IP_UNKNOWN, check=True):
    """Convert a netmask to another notation."""
    return _convert(nm, notation, inotation, _check=check, _isnm=True)


# - Classes used to manage IP addresses, netmasks and the CIDR notation.

class _IPv4Base(object):
    """Base class for IP addresses and netmasks."""
    _isnm = False # Set to True when representing a netmask.

    def __init__(self, ip, notation=IP_UNKNOWN):
        """Initialize the object."""
        self.set(ip, notation)

    def set(self, ip, notation=IP_UNKNOWN):
        """Set the IP address/netmask."""
        self._ip_dec = int(_convert(ip, notation=IP_DEC, inotation=notation,
                                    _check=True, _isnm=self._isnm))
        self._ip = _convert(self._ip_dec, notation=IP_DOT, inotation=IP_DEC,
                            _check=False, _isnm=self._isnm)

    def get(self):
        """Return the address/netmask."""
        return self.get_dot()

    def get_dot(self):
        """Return the dotted decimal notation of the address/netmask."""
        return self._ip

    def get_hex(self):
        """Return the hexadecimal notation of the address/netmask."""
        return _convert(self._ip_dec, notation=IP_HEX,
                        inotation=IP_DEC, _check=False, _isnm=self._isnm)

    def get_bin(self):
        """Return the binary notation of the address/netmask."""
        return _convert(self._ip_dec, notation=IP_BIN,
                        inotation=IP_DEC, _check=False, _isnm=self._isnm)

    def get_dec(self):
        """Return the decimal notation of the address/netmask."""
        return str(self._ip_dec)

    def get_oct(self):
        """Return the octal notation of the address/netmask."""
        return _convert(self._ip_dec, notation=IP_OCT,
                        inotation=IP_DEC, _check=False, _isnm=self._isnm)

    def __str__(self):
        """Print this address/netmask."""
        return self.get()

    def _cmp_prepare(self, other):
        """Prepare the item to be compared with this address/netmask."""
        if isinstance(other, self.__class__):
            return other._ip_dec
        elif isinstance(other, int):
            # NOTE: this hides the fact that "other" can be a non valid IP/nm.
            return other
        return self.__class__(other)._ip_dec

    def __lt__(self, other):
        ret = self._ip_dec < self._cmp_prepare(other)
        if self._isnm:
            return not ret
        return ret

    def __le__(self, other):
        ret = self._ip_dec <= self._cmp_prepare(other)
        if self._isnm:
            return not ret
        return ret

    def __gt__(self, other):
        ret = self._ip_dec > self._cmp_prepare(other)
        if self._isnm:
            return not ret
        return ret

    def __ge__(self, other):
        ret = self._ip_dec >= self._cmp_prepare(other)
        if self._isnm:
            return not ret
        return ret

    def __eq__(self, other):
        return self._ip_dec == self._cmp_prepare(other)

    def __ne__(self, other):
        return self._ip_dec != self._cmp_prepare(other)

    def __int__(self):
        """Return the decimal representation of the address/netmask."""
        return self._ip_dec

    def __index__(self):
        return self._ip_dec

    def __long__(self):
        return self._ip_dec

    def __oct__(self):
        return oct(self._ip_dec)

    def __hex__(self):
        return hex(self._ip_dec)

    if not _isnm:
        ip = address = property(get, set, doc='The represented IP.')
    else:
        nm = netmask = property(get, set, doc='The represented netmask.')


class IPv4Address(_IPv4Base):
    """An IPv4 Internet address.

    This class represents an IPv4 Internet address."""

    def __repr__(self):
        """The representation string for this address."""
        return '<IPv4 address %s>' % self.get()

    def _add(self, other):
        """Sum two IP addresses."""
        if isinstance(other, self.__class__):
            sum_ = self._ip_dec + other._ip_dec
        elif isinstance(other, int):
            sum_ = self._ip_dec + other
        else:
            other = self.__class__(other)
            sum_ = self._ip_dec + other._ip_dec
        return sum_

    def __add__(self, other):
        """Sum two IP addresses."""
        return IPv4Address(self._add(other), notation=IP_DEC)

    __radd__ = __add__

    def __iadd__(self, other):
        """Augmented arithmetic sum."""
        self.set(self._add(other), notation=IP_DEC)
        return self

    def _sub(self, other):
        """Subtract two IP addresses."""
        if isinstance(other, self.__class__):
            sub = self._ip_dec - other._ip_dec
        if isinstance(other, int):
            sub = self._ip_dec - other
        else:
            other = self.__class__(other)
            sub = self._ip_dec - other._ip_dec
        return sub

    def __sub__(self, other):
        """Subtract two IP addresses."""
        return IPv4Address(self._sub(other), notation=IP_DEC)

    __rsub__ = __sub__

    def __isub__(self, other):
        """Augmented arithmetic subtraction."""
        self.set(self._sub(other), notation=IP_DEC)
        return self


class IPv4NetMask(_IPv4Base):
    """An IPv4 Internet netmask.

    This class represents an IPv4 Internet netmask."""
    _isnm = True

    def get_bits(self):
        """Return the bits notation of the netmask."""
        return _convert(self._ip, notation=NM_BITS,
                        inotation=IP_DOT, _check=False, _isnm=self._isnm)

    def get_wildcard(self):
        """Return the wildcard bits notation of the netmask."""
        return _convert(self._ip, notation=NM_WILDCARD,
                        inotation=IP_DOT, _check=False, _isnm=self._isnm)

    def __repr__(self):
        """The representation string for this netmask."""
        return '<IPv4 netmask %s>' % self.get()


class CIDR(object):
    """A CIDR address.

    The representation of a Classless Inter-Domain Routing (CIDR) address."""
    def __init__(self, ip, netmask=None):
        self.set(ip, netmask)

    def set(self, ip, netmask=None):
        """Set the IP address and the netmask."""
        if isinstance(ip, str) and netmask is None:
            ipnm = ip.split('/')
            if len(ipnm) != 2:
                raise ValueError('set: invalid CIDR: "%s"' % ip)
            ip = ipnm[0]
            netmask = ipnm[1]
        if isinstance(ip, IPv4Address):
            self._ip = ip
        else:
            self._ip = IPv4Address(ip)
        if isinstance(netmask, IPv4NetMask):
            self._nm = netmask
        else:
            self._nm = IPv4NetMask(netmask)
        ipl = int(self._ip)
        nml = int(self._nm)
        base_add = ipl & nml
        self._ip_num = 0xFFFFFFFF - 1 - nml
        # NOTE: quite a mess.
        #      This's here to handle /32 (-1) and /31 (0) netmasks.
        if self._ip_num in (-1, 0):
            if self._ip_num == -1:
                self._ip_num = 1
            else:
                self._ip_num = 2
            self._net_ip = None
            self._bc_ip = None
            self._first_ip_dec = base_add
            self._first_ip = IPv4Address(self._first_ip_dec, notation=IP_DEC)
            if self._ip_num == 1:
                last_ip_dec = self._first_ip_dec
            else:
                last_ip_dec = self._first_ip_dec + 1
            self._last_ip = IPv4Address(last_ip_dec, notation=IP_DEC)
            return
        self._net_ip = IPv4Address(base_add, notation=IP_DEC)
        self._bc_ip = IPv4Address(base_add + self._ip_num + 1, notation=IP_DEC)
        self._first_ip_dec = base_add + 1
        self._first_ip = IPv4Address(self._first_ip_dec, notation=IP_DEC)
        self._last_ip = IPv4Address(base_add + self._ip_num, notation=IP_DEC)

    def get(self):
        """Print this CIDR address."""
        return '%s/%s' % (str(self._ip), str(self._nm))

    def set_ip(self, ip):
        """Change the current IP."""
        self.set(ip=ip, netmask=self._nm)

    def get_ip(self):
        """Return the given address."""
        return self._ip

    def set_netmask(self, netmask):
        """Change the current netmask."""
        self.set(ip=self._ip, netmask=netmask)

    def get_netmask(self):
        """Return the netmask."""
        return self._nm

    def get_first_ip(self):
        """Return the first usable IP address."""
        return self._first_ip

    def get_last_ip(self):
        """Return the last usable IP address."""
        return self._last_ip

    def get_network_ip(self):
        """Return the network address."""
        return self._net_ip

    def get_broadcast_ip(self):
        """Return the broadcast address."""
        return self._bc_ip

    def get_ip_number(self):
        """Return the number of usable IP addresses."""
        return self._ip_num

    def get_all_valid_ip(self):
        """Return a list of IPv4Address objects, one for every usable IP.

        WARNING: it's slow and can take a huge amount of memory for
        subnets with a large number of addresses.
        Use __iter__ instead ('for ip in ...')."""
        return list(self.__iter__())

    def is_valid_ip(self, ip):
        """Return true if the given address in amongst the usable addresses,
        or if the given CIDR is contained in this one."""
        if not isinstance(ip, (IPv4Address, CIDR)):
            if str(ip).find('/') == -1:
                ip = IPv4Address(ip)
            else:
                # Support for CIDR strings/objects, an idea of Nicola Novello.
                ip = CIDR(ip)
        if isinstance(ip, IPv4Address):
            if ip < self._first_ip or ip > self._last_ip:
                return False
        elif isinstance(ip, CIDR):
            # NOTE: manage /31 networks; 127.0.0.1/31 is considered to
            #       be included in 127.0.0.1/8.
            if ip._nm._ip_dec == 0xFFFFFFFE \
                    and self._nm._ip_dec != 0xFFFFFFFE:
                compare_to_first = self._net_ip._ip_dec
                compare_to_last = self._bc_ip._ip_dec
            else:
                compare_to_first = self._first_ip._ip_dec
                compare_to_last = self._last_ip._ip_dec
            if ip._first_ip._ip_dec < compare_to_first or \
                    ip._last_ip._ip_dec > compare_to_last:
                return False
        return True

    def __str__(self):
        """Print this CIDR address."""
        return self.get()

    def __repr__(self):
        """The representation string for this netmask."""
        return '<%s/%s CIDR>' % (str(self.get_ip()), str(self.get_netmask()))

    def __len__(self):
        """Return the number of usable IP address."""
        return self.get_ip_number()

    def __lt__(self, other):
        if not isinstance(other, self.__class__):
            other = self.__class__(other)
        return self._nm < other._nm

    def __le__(self, other):
        if not isinstance(other, self.__class__):
            other = self.__class__(other)
        return self._nm <= other._nm

    def __gt__(self, other):
        if not isinstance(other, self.__class__):
            other = self.__class__(other)
        return self._nm > other._nm

    def __ge__(self, other):
        if not isinstance(other, self.__class__):
            other = self.__class__(other)
        return self._nm >= other._nm

    def __eq__(self, other):
        if not isinstance(other, self.__class__):
            other = self.__class__(other)
        return self._nm == other._nm

    def __ne__(self, other):
        if not isinstance(other, self.__class__):
            other = self.__class__(other)
        return self._nm != other._nm

    def __contains__(self, item):
        """Return true if the given address in amongst the usable addresses,
        or if the given CIDR is contained in this one."""
        return self.is_valid_ip(item)

    def __iter__(self):
        """Iterate over IPv4Address objects, one for every usable IP."""
        for i in range(0, self._ip_num):
            yield IPv4Address(self._first_ip_dec + i, notation=IP_DEC)

    cidr = property(get, set, doc='The represented CIDR.')
    ip = address = property(get_ip, set_ip, doc='The IP of this CIDR.')
    nm = netmask = property(get_netmask, set_netmask,
                            doc='The netmask of this CIDR.')
    first_ip = property(get_first_ip)
    last_ip = property(get_last_ip)
    network_ip = property(get_network_ip)
    broadcast_ip = property(get_broadcast_ip)
    ip_number = property(get_ip_number)