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DNS querying through libc using ctypes

Project description

Provides access to res_query (resolver(3)) and friends for very basic DNS querying (beyond gethostbyname).

Right now, it only supports MX record lookups.

This is not a replacement for fully featured DNS libraries like dnspython or pycares, but rather a small wrapper to provide a bare minimal lookup capability. Additionally, it serves as an example of how to use -lresolv routines.

Most common usage

from pylresolv import ns_parse, ns_type, res_query

answer = res_query('', rr_type=ns_type.ns_t_mx)
ret = ns_parse(answer, handler=ns_type.handle_t_mx)

Will produce a list of RR objects:

[RR<ns_type.ns_t_mx: 15>((40, u'')),
 RR<ns_type.ns_t_mx: 15>((30, u'')),
 RR<ns_type.ns_t_mx: 15>((10, u'')),
 RR<ns_type.ns_t_mx: 15>((20, u'')),
 RR<ns_type.ns_t_mx: 15>((5, u''))]

Example from main:

from pprint import pprint
queries = (
    ('', ns_type.ns_t_ns),
    ('', ns_type.ns_t_a),
    ('', ns_type.ns_t_mx),
    ('', ns_type.ns_t_txt),
    ('', ns_type.ns_t_cname),
for qhost, qtype in queries:
    print('Querying host {!r} type {!r}:'.format(qhost, qtype))
    answer = res_query(qhost, rr_type=qtype)
    ret = ns_parse(answer)
    # ret = ns_parse(answer, handler=ns_type.handle_t_mx)
    # ret = ns_parse(answer, handler=ns_type.handle_bin)
    pprint([rr.contents for rr in ret])


Querying host '' type <ns_type.ns_t_ns: 2>:
['', '', '', '']

Querying host '' type <ns_type.ns_t_a: 1>:

Querying host '' type <ns_type.ns_t_mx: 15>:
[(40, ''),
 (30, ''),
 (10, ''),
 (20, ''),
 (5, '')]

Querying host '' type <ns_type.ns_t_txt: 16>:

Querying host '' type <ns_type.ns_t_cname: 5>:

2019-07-03: 0.2

  • Renamed ns_type.handle_mx to ns_type.handle_t_mx.

  • Added: - handle_bin - handle_compressed - handle_text - handle_t_cname - handle_t_ns` - handle_t_txt`

  • ns_parse now wraps the returned values into RR objects, so the type can be retrieved afterwards. The value can be fetched from its contents property.

  • You can use handle_bin to fetch A or AAAA records.

  • res_query now raises LookupError on failure.

2019-03-17: 0.1

  • Initial release.

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