socket.gethostbyaddr() wrongly returning a DNS CNAME as the 'primary' hostname

Ned Deily nad at acm.org
Thu Apr 28 21:34:45 CEST 2011


In article 
<850c85c0-be6e-4eec-b6b1-5c79e1716f6d at glegroupsg2000goo.googlegroups.com
>, cjblaine <cjblaine at gmail.com> wrote:
> Python 2.7.1 (perhaps others)
> 
> I believe this is a bug.  Comments?
> 
> Docs state: Return a triple (hostname, aliaslist, ipaddrlist)
> where hostname is the primary host name responding to the
> given ip_address, aliaslist is a (possibly empty) list of
> alternative host names  for the same address, and ipaddrlist
> is a list of IPv4/v6 addresses for the same interface on the
> same host (most likely containing only a single address).
> 
> my-dns-cname.our.org is a CNAME record for primary.our.org
> primary.our.org has IP address xx.xx.xx.xx
> 
> import socket
> socket.gethostbyaddr('xx.xx.xx.xx')
> 
> returns:
> 
>     ('my-dns-cname.our.org', ['primary.our.org'], ['xx.xx.xx.xx'])

socket.gethostbyaddr() is pretty much just a transparent wrapper around 
the platform's C library function of the same name.  See if a simple C 
program with a similar call to gethostbyaddr produces the same results.  
The code in question for Python 2.7 is here:

http://hg.python.org/cpython/file/a6b772599594/Modules/socketmodule.c

-- 
 Ned Deily,
 nad at acm.org




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