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233 lines
8.9 KiB
233 lines
8.9 KiB
3 years ago
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# Copyright (C) Dnspython Contributors, see LICENSE for text of ISC license
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# Copyright (C) 2003-2017 Nominum, Inc.
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#
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# Permission to use, copy, modify, and distribute this software and its
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# documentation for any purpose with or without fee is hereby granted,
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# provided that the above copyright notice and this permission notice
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# appear in all copies.
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#
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# THE SOFTWARE IS PROVIDED "AS IS" AND NOMINUM DISCLAIMS ALL WARRANTIES
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# WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
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# MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL NOMINUM BE LIABLE FOR
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# ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
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# WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
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# ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT
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# OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
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"""Asynchronous DNS stub resolver."""
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import time
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import dns.asyncbackend
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import dns.asyncquery
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import dns.exception
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import dns.query
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import dns.resolver
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# import some resolver symbols for brevity
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from dns.resolver import NXDOMAIN, NoAnswer, NotAbsolute, NoRootSOA
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# for indentation purposes below
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_udp = dns.asyncquery.udp
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_tcp = dns.asyncquery.tcp
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class Resolver(dns.resolver.BaseResolver):
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"""Asynchronous DNS stub resolver."""
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async def resolve(self, qname, rdtype=dns.rdatatype.A,
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rdclass=dns.rdataclass.IN,
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tcp=False, source=None, raise_on_no_answer=True,
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source_port=0, lifetime=None, search=None,
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backend=None):
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"""Query nameservers asynchronously to find the answer to the question.
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*backend*, a ``dns.asyncbackend.Backend``, or ``None``. If ``None``,
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the default, then dnspython will use the default backend.
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See :py:func:`dns.resolver.Resolver.resolve()` for the
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documentation of the other parameters, exceptions, and return
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type of this method.
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"""
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resolution = dns.resolver._Resolution(self, qname, rdtype, rdclass, tcp,
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raise_on_no_answer, search)
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if not backend:
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backend = dns.asyncbackend.get_default_backend()
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start = time.time()
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while True:
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(request, answer) = resolution.next_request()
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# Note we need to say "if answer is not None" and not just
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# "if answer" because answer implements __len__, and python
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# will call that. We want to return if we have an answer
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# object, including in cases where its length is 0.
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if answer is not None:
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# cache hit!
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return answer
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done = False
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while not done:
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(nameserver, port, tcp, backoff) = resolution.next_nameserver()
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if backoff:
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await backend.sleep(backoff)
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timeout = self._compute_timeout(start, lifetime,
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resolution.errors)
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try:
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if dns.inet.is_address(nameserver):
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if tcp:
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response = await _tcp(request, nameserver,
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timeout, port,
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source, source_port,
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backend=backend)
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else:
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response = await _udp(request, nameserver,
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timeout, port,
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source, source_port,
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raise_on_truncation=True,
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backend=backend)
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else:
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response = await dns.asyncquery.https(request,
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nameserver,
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timeout=timeout)
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except Exception as ex:
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(_, done) = resolution.query_result(None, ex)
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continue
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(answer, done) = resolution.query_result(response, None)
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# Note we need to say "if answer is not None" and not just
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# "if answer" because answer implements __len__, and python
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# will call that. We want to return if we have an answer
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# object, including in cases where its length is 0.
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if answer is not None:
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return answer
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async def resolve_address(self, ipaddr, *args, **kwargs):
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"""Use an asynchronous resolver to run a reverse query for PTR
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records.
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This utilizes the resolve() method to perform a PTR lookup on the
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specified IP address.
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*ipaddr*, a ``str``, the IPv4 or IPv6 address you want to get
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the PTR record for.
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All other arguments that can be passed to the resolve() function
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except for rdtype and rdclass are also supported by this
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function.
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"""
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return await self.resolve(dns.reversename.from_address(ipaddr),
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rdtype=dns.rdatatype.PTR,
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rdclass=dns.rdataclass.IN,
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*args, **kwargs)
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# pylint: disable=redefined-outer-name
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async def canonical_name(self, name):
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"""Determine the canonical name of *name*.
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The canonical name is the name the resolver uses for queries
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after all CNAME and DNAME renamings have been applied.
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*name*, a ``dns.name.Name`` or ``str``, the query name.
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This method can raise any exception that ``resolve()`` can
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raise, other than ``dns.resolver.NoAnswer`` and
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``dns.resolver.NXDOMAIN``.
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Returns a ``dns.name.Name``.
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"""
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try:
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answer = await self.resolve(name, raise_on_no_answer=False)
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canonical_name = answer.canonical_name
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except dns.resolver.NXDOMAIN as e:
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canonical_name = e.canonical_name
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return canonical_name
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default_resolver = None
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def get_default_resolver():
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"""Get the default asynchronous resolver, initializing it if necessary."""
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if default_resolver is None:
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reset_default_resolver()
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return default_resolver
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def reset_default_resolver():
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"""Re-initialize default asynchronous resolver.
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Note that the resolver configuration (i.e. /etc/resolv.conf on UNIX
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systems) will be re-read immediately.
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"""
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global default_resolver
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default_resolver = Resolver()
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async def resolve(qname, rdtype=dns.rdatatype.A, rdclass=dns.rdataclass.IN,
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tcp=False, source=None, raise_on_no_answer=True,
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source_port=0, lifetime=None, search=None, backend=None):
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"""Query nameservers asynchronously to find the answer to the question.
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This is a convenience function that uses the default resolver
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object to make the query.
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See :py:func:`dns.asyncresolver.Resolver.resolve` for more
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information on the parameters.
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"""
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return await get_default_resolver().resolve(qname, rdtype, rdclass, tcp,
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source, raise_on_no_answer,
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source_port, lifetime, search,
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backend)
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async def resolve_address(ipaddr, *args, **kwargs):
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"""Use a resolver to run a reverse query for PTR records.
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See :py:func:`dns.asyncresolver.Resolver.resolve_address` for more
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information on the parameters.
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"""
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return await get_default_resolver().resolve_address(ipaddr, *args, **kwargs)
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async def canonical_name(name):
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"""Determine the canonical name of *name*.
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See :py:func:`dns.resolver.Resolver.canonical_name` for more
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information on the parameters and possible exceptions.
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"""
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return await get_default_resolver().canonical_name(name)
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async def zone_for_name(name, rdclass=dns.rdataclass.IN, tcp=False,
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resolver=None, backend=None):
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"""Find the name of the zone which contains the specified name.
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See :py:func:`dns.resolver.Resolver.zone_for_name` for more
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information on the parameters and possible exceptions.
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"""
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if isinstance(name, str):
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name = dns.name.from_text(name, dns.name.root)
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if resolver is None:
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resolver = get_default_resolver()
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if not name.is_absolute():
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raise NotAbsolute(name)
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while True:
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try:
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answer = await resolver.resolve(name, dns.rdatatype.SOA, rdclass,
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tcp, backend=backend)
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if answer.rrset.name == name:
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return name
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# otherwise we were CNAMEd or DNAMEd and need to look higher
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except (NXDOMAIN, NoAnswer):
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pass
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try:
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name = name.parent()
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except dns.name.NoParent: # pragma: no cover
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raise NoRootSOA
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