Create ipaddr-py IPv6Address from byte string

Question

I frequently need to convert a raw, byte-encoded IPv6 address into an IPv6Address object from the ipaddr-py project. Byte-encoded IPv6 addresses are not accepted by the initializer as shown here:

>>> import ipaddr   
>>> byte_ip = b'\x20\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x01'
>>> ipaddr.IPAddress(byte_ip)
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "ipaddr.py", line 78, in IPAddress
    address)
ValueError: ' \x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x01' does
 not appear to be an IPv4 or IPv6 address

What is the easiest way to convert the byte-encoding to a format ipaddr-py can understand? I'm using v. 2.1.10 of ipaddr.py.

My only workaround so far is way too long for the simple task:

>>> def bytes_to_ipaddr_string(c):
...     c = c.encode('hex')
...     if len(c) is not 32: raise Exception('invalid IPv6 address')
...     s = ''
...     while c is not '':
...         s = s + ':'
...         s = s + c[:4]
...         c = c[4:]
...     return s[1:]
...
>>> ipaddr.IPAddress(bytes_to_ipaddr_string(byte_ip))
IPv6Address('2000::1')

EDIT: I'm looking for a cross-platform solution. Unix-only won't do.

Anyone got a better solution?

Roman Bodnarchuk · Accepted Answer · 2012-05-09 09:52:40Z

2

On Unix IPv6 bin -> string conversion is simple - all you need is socket.inet_ntop:

>>> socket.inet_ntop(socket.AF_INET6, b'\x20\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x01')
'2000::1'

answered May 9, 2012 at 9:52

Roman Bodnarchuk

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Jakob Buron Over a year ago

Very clean solution, thanks. Unfortunately I need a cross-platform solution. At least *nix and Win32.

glglgl · Accepted Answer · 2012-05-09 12:35:32Z

1

Have a look at ipaddr_test.py:

[...]
# Compatibility function to cast str to bytes objects
if issubclass(ipaddr.Bytes, str):
    _cb = ipaddr.Bytes
else:
    _cb = lambda bytestr: bytes(bytestr, 'charmap')
[...]

Then

_cb('\x20\x01\x06\x58\x02\x2a\xca\xfe'
    '\x02\x00\x00\x00\x00\x00\x00\x01')

provides you a Bytes object which is recognized by the module to contain a packed address.

I didn't test it, but it looks as if it is the way it is intended to be...

Meanwhile I tested it. The _cb stuff is presumably for older moule versions which didn't have a Bytes object. So you just can do

import ipaddr
b = ipaddr.Bytes('\x20\x01\x06\x58\x02\x2a\xca\xfe' '\x02\x00\x00\x00\x00\x00\x00\x01')
print ipaddr.IPAddress(b)

which will result in

2001:658:22a:cafe:200::1

which is probably what you need.

edited May 9, 2012 at 12:35

answered May 9, 2012 at 11:24

glglgl

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1 Comment

Jakob Buron Over a year ago

Bingo, ipaddr.IPAddress(ipaddr.Bytes(byte_ip)) works like a charm. I think the _cb stuff is for Python3 compatibility.

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