1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
|
# Copyright (C) Dnspython Contributors, see LICENSE for text of ISC license
# Copyright (C) 2003-2017 Nominum, Inc.
#
# Permission to use, copy, modify, and distribute this software and its
# documentation for any purpose with or without fee is hereby granted,
# provided that the above copyright notice and this permission notice
# appear in all copies.
#
# THE SOFTWARE IS PROVIDED "AS IS" AND NOMINUM DISCLAIMS ALL WARRANTIES
# WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
# MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL NOMINUM BE LIABLE FOR
# ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
# WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
# ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT
# OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
"""Asynchronous DNS stub resolver."""
import time
import dns.asyncbackend
import dns.asyncquery
import dns.exception
import dns.query
import dns.resolver
# import some resolver symbols for brevity
from dns.resolver import NXDOMAIN, NoAnswer, NotAbsolute, NoRootSOA
# for indentation purposes below
_udp = dns.asyncquery.udp
_tcp = dns.asyncquery.tcp
class Resolver(dns.resolver.BaseResolver):
"""Asynchronous DNS stub resolver."""
async def resolve(self, qname, rdtype=dns.rdatatype.A,
rdclass=dns.rdataclass.IN,
tcp=False, source=None, raise_on_no_answer=True,
source_port=0, lifetime=None, search=None,
backend=None):
"""Query nameservers asynchronously to find the answer to the question.
*backend*, a ``dns.asyncbackend.Backend``, or ``None``. If ``None``,
the default, then dnspython will use the default backend.
See :py:func:`dns.resolver.Resolver.resolve()` for the
documentation of the other parameters, exceptions, and return
type of this method.
"""
resolution = dns.resolver._Resolution(self, qname, rdtype, rdclass, tcp,
raise_on_no_answer, search)
if not backend:
backend = dns.asyncbackend.get_default_backend()
start = time.time()
while True:
(request, answer) = resolution.next_request()
# Note we need to say "if answer is not None" and not just
# "if answer" because answer implements __len__, and python
# will call that. We want to return if we have an answer
# object, including in cases where its length is 0.
if answer is not None:
# cache hit!
return answer
done = False
while not done:
(nameserver, port, tcp, backoff) = resolution.next_nameserver()
if backoff:
await backend.sleep(backoff)
timeout = self._compute_timeout(start, lifetime,
resolution.errors)
try:
if dns.inet.is_address(nameserver):
if tcp:
response = await _tcp(request, nameserver,
timeout, port,
source, source_port,
backend=backend)
else:
response = await _udp(request, nameserver,
timeout, port,
source, source_port,
raise_on_truncation=True,
backend=backend)
else:
# We don't do DoH yet.
raise NotImplementedError
except Exception as ex:
(_, done) = resolution.query_result(None, ex)
continue
(answer, done) = resolution.query_result(response, None)
# Note we need to say "if answer is not None" and not just
# "if answer" because answer implements __len__, and python
# will call that. We want to return if we have an answer
# object, including in cases where its length is 0.
if answer is not None:
return answer
async def resolve_address(self, ipaddr, *args, **kwargs):
"""Use an asynchronous resolver to run a reverse query for PTR
records.
This utilizes the resolve() method to perform a PTR lookup on the
specified IP address.
*ipaddr*, a ``str``, the IPv4 or IPv6 address you want to get
the PTR record for.
All other arguments that can be passed to the resolve() function
except for rdtype and rdclass are also supported by this
function.
"""
return await self.resolve(dns.reversename.from_address(ipaddr),
rdtype=dns.rdatatype.PTR,
rdclass=dns.rdataclass.IN,
*args, **kwargs)
# pylint: disable=redefined-outer-name
async def canonical_name(self, name):
"""Determine the canonical name of *name*.
The canonical name is the name the resolver uses for queries
after all CNAME and DNAME renamings have been applied.
*name*, a ``dns.name.Name`` or ``str``, the query name.
This method can raise any exception that ``resolve()`` can
raise, other than ``dns.resolver.NoAnswer`` and
``dns.resolver.NXDOMAIN``.
Returns a ``dns.name.Name``.
"""
try:
answer = await self.resolve(name, raise_on_no_answer=False)
canonical_name = answer.canonical_name
except dns.resolver.NXDOMAIN as e:
canonical_name = e.canonical_name
return canonical_name
default_resolver = None
def get_default_resolver():
"""Get the default asynchronous resolver, initializing it if necessary."""
if default_resolver is None:
reset_default_resolver()
return default_resolver
def reset_default_resolver():
"""Re-initialize default asynchronous resolver.
Note that the resolver configuration (i.e. /etc/resolv.conf on UNIX
systems) will be re-read immediately.
"""
global default_resolver
default_resolver = Resolver()
async def resolve(qname, rdtype=dns.rdatatype.A, rdclass=dns.rdataclass.IN,
tcp=False, source=None, raise_on_no_answer=True,
source_port=0, lifetime=None, search=None, backend=None):
"""Query nameservers asynchronously to find the answer to the question.
This is a convenience function that uses the default resolver
object to make the query.
See :py:func:`dns.asyncresolver.Resolver.resolve` for more
information on the parameters.
"""
return await get_default_resolver().resolve(qname, rdtype, rdclass, tcp,
source, raise_on_no_answer,
source_port, lifetime, search,
backend)
async def resolve_address(ipaddr, *args, **kwargs):
"""Use a resolver to run a reverse query for PTR records.
See :py:func:`dns.asyncresolver.Resolver.resolve_address` for more
information on the parameters.
"""
return await get_default_resolver().resolve_address(ipaddr, *args, **kwargs)
async def canonical_name(name):
"""Determine the canonical name of *name*.
See :py:func:`dns.resolver.Resolver.canonical_name` for more
information on the parameters and possible exceptions.
"""
return await get_default_resolver().canonical_name(name)
async def zone_for_name(name, rdclass=dns.rdataclass.IN, tcp=False,
resolver=None, backend=None):
"""Find the name of the zone which contains the specified name.
See :py:func:`dns.resolver.Resolver.zone_for_name` for more
information on the parameters and possible exceptions.
"""
if isinstance(name, str):
name = dns.name.from_text(name, dns.name.root)
if resolver is None:
resolver = get_default_resolver()
if not name.is_absolute():
raise NotAbsolute(name)
while True:
try:
answer = await resolver.resolve(name, dns.rdatatype.SOA, rdclass,
tcp, backend=backend)
if answer.rrset.name == name:
return name
# otherwise we were CNAMEd or DNAMEd and need to look higher
except (NXDOMAIN, NoAnswer):
pass
try:
name = name.parent()
except dns.name.NoParent: # pragma: no cover
raise NoRootSOA
|
