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1# Copyright (c) 2014 The Chromium OS Authors. All rights reserved.
2# Use of this source code is governed by a BSD-style license that can be
3# found in the LICENSE file.
4
5import logging
6
7from autotest_lib.client.common_lib import error
8
9def from_addr(addr, prefix_len=None):
10    """Build a Netblock object.
11
12    @param addr: string IP address with optional prefix length
13            (e.g. '192.168.1.1' or '192.168.1.1/24'). If |addr| has no
14            prefix length, then use the |prefix_len| parameter.
15    @param prefix_len: int number of bits forming the IP subnet prefix for
16            |addr|. This value will be preferred to the parsed value if
17            |addr| has a prefix length as well. If |addr|
18            has no prefix length and |prefix_len| is None, then an error
19            will be thrown.
20
21    """
22    if addr is None:
23        raise error.TestError('netblock.from_addr() expects non-None addr '
24                              'parameter.')
25
26    prefix_sep_count = addr.count('/')
27    if prefix_sep_count > 1:
28        raise error.TestError('Invalid IP address found: "%s".' % addr)
29
30    if prefix_sep_count == 1:
31        addr_str, prefix_len_str = addr.split('/')
32    else:
33        # No prefix separator.  Assume addr looks like '192.168.1.1'
34        addr_str = addr
35        # Rely on passed in |prefix_len|
36        prefix_len_str = None
37
38    if prefix_len is not None and prefix_len_str is not None:
39        logging.warning('Ignoring parsed prefix length of %s in favor of '
40                        'passed in value %d', prefix_len_str, prefix_len)
41    elif prefix_len is not None and prefix_len_str is None:
42        pass
43    elif prefix_len is None and prefix_len_str is not None:
44        prefix_len = int(prefix_len_str)
45    else:
46        raise error.TestError('Cannot construct netblock without knowing '
47                              'prefix length for addr: "%s".' % addr)
48
49    return Netblock(addr_str, prefix_len)
50
51
52class Netblock(object):
53    """Utility class for transforming netblock address to related strings."""
54
55    @staticmethod
56    def _octets_to_addr(octets):
57        """Transform a list of bytes into a string IP address.
58
59        @param octets list of ints (e.g. [192.168.0.1]).
60        @return string IP address (e.g. '192.168.0.1.').
61
62        """
63        return '.'.join(map(str, octets))
64
65
66    @staticmethod
67    def _int_to_octets(num):
68        """Tranform a 32 bit number into a list of 4 octets.
69
70        @param num: number to convert to octets.
71        @return list of int values <= 8 bits long.
72
73        """
74        return [(num >> s) & 0xff for s in (24, 16, 8, 0)]
75
76
77    @property
78    def netblock(self):
79        """@return the IPv4 address/prefix, e.g., '192.168.0.1/24'."""
80        return '/'.join([self._octets_to_addr(self._octets),
81                         str(self.prefix_len)])
82
83
84    @property
85    def netmask(self):
86        """@return the IPv4 netmask, e.g., '255.255.255.0'."""
87        return self._octets_to_addr(self._mask_octets)
88
89
90    @property
91    def prefix_len(self):
92        """@return the IPv4 prefix len, e.g., 24."""
93        return self._prefix_len
94
95
96    @property
97    def subnet(self):
98        """@return the IPv4 subnet, e.g., '192.168.0.0'."""
99        octets = [a & m for a, m in zip(self._octets, self._mask_octets)]
100        return self._octets_to_addr(octets)
101
102
103    @property
104    def broadcast(self):
105        """@return the IPv4 broadcast address, e.g., '192.168.0.255'."""
106        octets = [a | (m ^ 0xff)
107                  for a, m in zip(self._octets, self._mask_octets)]
108        return self._octets_to_addr(octets)
109
110
111    @property
112    def addr(self):
113        """@return the IPv4 address, e.g., '192.168.0.1'."""
114        return self._octets_to_addr(self._octets)
115
116
117    def __init__(self, addr_str, prefix_len):
118        """Construct a Netblock.
119
120        @param addr_str: string IP address (e.g. '192.168.1.1').
121        @param prefix_len: int length of subnet prefix (e.g. 24).
122
123        """
124        self._octets = map(int, addr_str.split('.'))
125        mask_bits = (-1 << (32 - prefix_len)) & 0xffffffff
126        self._mask_octets = self._int_to_octets(mask_bits)
127        self._prefix_len = prefix_len
128
129
130    def get_addr_in_block(self, offset):
131        """Get an address in a subnet.
132
133        For instance if this netblock represents 192.168.0.1/24,
134        then get_addr_in_block(5) would return 192.168.0.5.
135
136        @param offset int offset in block, (e.g. 5).
137        @return string address (e.g. '192.168.0.5').
138
139        """
140        offset = self._int_to_octets(offset)
141        octets = [(a & m) + o
142                  for a, m, o in zip(self._octets, self._mask_octets, offset)]
143        return self._octets_to_addr(octets)
144