dns: implement querying directly the master server

nsupdate/main/_tests/test_dnstools.py

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+"""
+Tests for dnstools module.
+"""
+
+import pytest
+
+from nsupdate.main.dnstools import (query_ns, NONEXISTING_HOST, WWW_HOST, WWW_IPV4_HOST, WWW_IPV4_IP,
+                                    WWW_IPV6_HOST, WWW_IPV6_IP, )
+
+from dns.resolver import NXDOMAIN
+
+
+class Tests(object):
+    def test_queries_ok(self):
+        """
+        check some simple dns lookups
+        """
+        assert query_ns(WWW_IPV4_HOST, 'A') == WWW_IPV4_IP  # v4 ONLY
+        assert query_ns(WWW_IPV6_HOST, 'AAAA') == WWW_IPV6_IP  # v6 ONLY
+        assert query_ns(WWW_HOST, 'A') == WWW_IPV4_IP  # v4 and v6, query v4
+        assert query_ns(WWW_HOST, 'AAAA') == WWW_IPV6_IP  # v4 and v6, query v6
+
+    def test_queries_failing(self):
+        with pytest.raises(NXDOMAIN):
+            query_ns(NONEXISTING_HOST, 'A')
+        with pytest.raises(NXDOMAIN):
+            query_ns(NONEXISTING_HOST, 'AAAA')

nsupdate/main/dnstools.py

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+"""
+Misc. DNS related code: query, dynamic update, etc.
+"""
+
+SERVER = '85.10.192.104'  # ns1.thinkmo.de (master / dynamic upd server for nsupdate.info)
+BASEDOMAIN = 'nsupdate.info'
+
+NONEXISTING_HOST = 'nonexisting.' + BASEDOMAIN
+WWW_HOST = 'www.' + BASEDOMAIN
+WWW_IPV4_HOST = 'www.ipv4.' + BASEDOMAIN
+WWW_IPV6_HOST = 'www.ipv6.' + BASEDOMAIN
+WWW_IPV4_IP = '178.32.221.14'
+WWW_IPV6_IP = '2001:41d0:8:e00e::1'
+
+import dns.name
+import dns.resolver
+
+def query_ns(qname, rdtype):
+    """
+    query a dns name from our master server
+
+    :param qname: the query name
+    :type qname: dns.name.Name object or str
+    :param rdtype: the query type
+    :type rdtype: int or str
+    :return: IP (as str)
+    """
+    resolver = dns.resolver.Resolver(configure=False)
+    # we do not configure it from resolv.conf, but patch in the values we
+    # want into the documented attributes:
+    resolver.nameservers = [SERVER, ]
+    resolver.search = [dns.name.from_text(BASEDOMAIN), ]
+    answer = resolver.query(qname, rdtype)
+    return str(list(answer)[0])