[Python-Dev] IPv6 hostname resolution using socket.getaddrinfo()

Blinston_Fernandes at Dell.com Blinston_Fernandes at Dell.com
Tue Sep 18 04:14:46 CEST 2007


On python2.4.1

>>> socket.getaddrinfo('www.python.org', None, socket.AF_INET,
socket.SOCK_DGRAM, socket.IPPROTO_IP, socket.AI_CANONNAME)
[(2, 2, 17, 'dinsdale.python.org', ('82.94.237.218', 0))]
>>>

Blinston.

-----Original Message-----
From: python-dev-bounces+blinston_fernandes=dell.com at python.org
[mailto:python-dev-bounces+blinston_fernandes=dell.com at python.org] On
Behalf Of O.R.Senthil Kumaran
Sent: Monday, September 17, 2007 10:08 PM
To: python-dev at python.org
Subject: [Python-Dev] IPv6 hostname resolution using
socket.getaddrinfo()

To get the hostname, I can use socket.gethostbyname() but that has an
inherent limitation wherein does it not support IPv6 name resolution,
and
getaddrinfo() should be used instead.

Looking up the socket.getaddrinfo() documentation, I come to know that

The getaddrinfo() function returns a list of 5-tuples with the following
structure:

(family, socktype, proto, canonname, sockaddr)

family, socktype, proto are all integer and are meant to be passed to
the socket() function. canonname is a string representing the canonical
name of the host. It can be a numeric IPv4/v6 address when AI_CANONNAME
is specified for a numeric host.

With this information, if I try something like this:

>>> for res in socket.getaddrinfo('goofy.goofy.com', None,
	socket.AI_CANONNAME):

        print res

(2, 1, 6, '', ('10.98.1.6', 0))
(2, 2, 17, '', ('10.98.1.6', 0))
(2, 3, 0, '', ('10.98.1.6', 0))

In the output, I see the cannoname to be always blank ''. I am not
getting the IPv4 or IPv6 address as a result of using getaddrinfo().

Am I making any mistake?

What i am trying is a replacement function for
socket.gethostbyname(hostname) which will work for both IPv4 and IPv6
(and make changes in urllib2 to support that)

# return hostbyname for either IPv4 or IPv6 address. Common function.

def ipv6_gethostbyname(hostname):
        for res in socket.getaddrinfo(hostname,None,
		socket.AI_CANONNAME):
                fa, socktype, proto, canonname, sa = res
        return cannoname

The above function does not seem to work. It returns blank value only.

Any help/ pointers? 

--
O.R.Senthil Kumaran
http://uthcode.sarovar.org
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