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Re: socket.gethostbyaddr( os.environ['REMOTE_ADDR'] error

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Chris Angelico <rosuav@gmail.com> wrote:

> On Tue, Jan 10, 2012 at 9:35 AM, Dominic Binks <dbinks@codeaurora.org> wrote:
> > The address database can have multiple names for the same IP address so
> > gethostbyaddr returns a list - [0] being the first item in the list (and
> > usually considered the canonical name)
> 
> Point to note: The inverse operation, getting IP addresses from names,
> quite frequently returns multiple results - and in that case, there's
> no "canonical name". You'll still usually want to take the zeroth
> (first) item in the list, but often the list will change in order.
> Try, for instance:
> 
> $ dig +short www.google.com
> 
> which uses DNS rotation as a form of load-balancing.
> 
> In any case, you normally just take the first entry.
> 

On both 2.6.6 and 2.7.1, the doc says: 

,----
| >>> help(socket.gethostbyaddr)
| Help on built-in function gethostbyaddr in module _socket:
| 
| gethostbyaddr(...)
|     gethostbyaddr(host) -> (name, aliaslist, addresslist)
|     
|     Return the true host name, a list of aliases, and a list of IP addresses,
|     for a host.  The host argument is a string giving a host name or IP number.
`----

so socket.gethostbyaddr(os.environ['REMOTE_ADDR'])[0] is the 0th element
of the tuple, i.e. the *name* that is returned. So (unless I'm confused
which is always a distinct possibility) this has nothing to do with
load-balancing or multiple addresses: it's the equivalent of 

  dig +short -x <addr>

Nick

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Re: socket.gethostbyaddr( os.environ['REMOTE_ADDR'] error Thomas Rachel <nutznetz-0c1b6768-bfa9-48d5-a470-7603bd3aa915@spamschutz.glglgl.de> - 2012-01-02 16:49 +0100
  Re: socket.gethostbyaddr( os.environ['REMOTE_ADDR'] error Νικόλαος Κούρας <nikos.kouras@gmail.com> - 2012-01-02 10:18 -0800
    Re: socket.gethostbyaddr( os.environ['REMOTE_ADDR'] error Roy Smith <roy@panix.com> - 2012-01-02 13:42 -0500
      Re: socket.gethostbyaddr( os.environ['REMOTE_ADDR'] error Νικόλαος Κούρας <nikos.kouras@gmail.com> - 2012-01-02 11:51 -0800
        Re: socket.gethostbyaddr( os.environ['REMOTE_ADDR'] error Roy Smith <roy@panix.com> - 2012-01-02 15:31 -0500
          Re: socket.gethostbyaddr( os.environ['REMOTE_ADDR'] error Νικόλαος Κούρας <nikos.kouras@gmail.com> - 2012-01-09 14:19 -0800
            Re: socket.gethostbyaddr( os.environ['REMOTE_ADDR'] error Dominic Binks <dbinks@codeaurora.org> - 2012-01-09 14:35 -0800
              Re: socket.gethostbyaddr( os.environ['REMOTE_ADDR'] error Νικόλαος Κούρας <nikos.kouras@gmail.com> - 2012-01-09 15:04 -0800
              Re: socket.gethostbyaddr( os.environ['REMOTE_ADDR'] error Thomas Rachel <nutznetz-0c1b6768-bfa9-48d5-a470-7603bd3aa915@spamschutz.glglgl.de> - 2012-01-10 07:42 +0100
                Re: socket.gethostbyaddr( os.environ['REMOTE_ADDR'] error Chris Angelico <rosuav@gmail.com> - 2012-01-10 18:29 +1100
            Re: socket.gethostbyaddr( os.environ['REMOTE_ADDR'] error Chris Angelico <rosuav@gmail.com> - 2012-01-10 10:14 +1100
            Re: socket.gethostbyaddr( os.environ['REMOTE_ADDR'] error Nick Dokos <nicholas.dokos@hp.com> - 2012-01-09 18:32 -0500
            Re: socket.gethostbyaddr( os.environ['REMOTE_ADDR'] error Chris Angelico <rosuav@gmail.com> - 2012-01-10 13:08 +1100
      Re: socket.gethostbyaddr( os.environ['REMOTE_ADDR'] error Νικόλαος Κούρας <nikos.kouras@gmail.com> - 2012-01-02 11:54 -0800

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