38 lines
1.2 KiB
ReStructuredText
38 lines
1.2 KiB
ReStructuredText
.. _example_reverse_lookup:
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Reverse DNS lookup
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==================
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Reverse DNS lookup involves determining the hostname associated with a given IP
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address.
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This example shows how reverse lookup can be done using unbound module.
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For the reverse DNS records, the special domain in-addr.arpa is reserved.
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For example, a host name for the IP address ``74.125.43.147`` can be obtained
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by issuing a DNS query for the PTR record for address
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``147.43.125.74.in-addr.arpa.``
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Source code
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-----------
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::
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#!/usr/bin/python
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import unbound
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ctx = unbound.ub_ctx()
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ctx.resolvconf("/etc/resolv.conf")
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status, result = ctx.resolve(unbound.reverse("74.125.43.147") + ".in-addr.arpa.", unbound.RR_TYPE_PTR, unbound.RR_CLASS_IN)
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if status == 0 and result.havedata:
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print "Result.data:", result.data.domain_list
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elif status != 0:
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print "Resolve error:", unbound.ub_strerror(status)
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In order to simplify the python code, unbound module contains the
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:meth:`unbound.reverse` function which reverses the hostname components.
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This function is defined as follows::
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def reverse(domain):
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return '.'.join([a for a in domain.split(".")][::-1])
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