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# 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.
"""trio async I/O library DNS stub resolver."""
import trio
import dns.exception
import dns.query
import dns.resolver
import dns.trio.query
# import some resolver symbols for brevity
from dns.resolver import NXDOMAIN, NoAnswer, NotAbsolute, NoRootSOA
# we do this for indentation reasons below
_udp = dns.trio.query.udp
_stream = dns.trio.query.stream
class TooManyAttempts(dns.exception.DNSException):
"""A resolution had too many unsuccessful attempts."""
class Resolver(dns.resolver.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, search=None):
"""Query nameservers asynchronously to find the answer to the question.
The *qname*, *rdtype*, and *rdclass* parameters may be objects
of the appropriate type, or strings that can be converted into objects
of the appropriate type.
*qname*, a ``dns.name.Name`` or ``str``, the query name.
*rdtype*, an ``int`` or ``str``, the query type.
*rdclass*, an ``int`` or ``str``, the query class.
*tcp*, a ``bool``. If ``True``, use TCP to make the query.
*source*, a ``str`` or ``None``. If not ``None``, bind to this IP
address when making queries.
*raise_on_no_answer*, a ``bool``. If ``True``, raise
``dns.resolver.NoAnswer`` if there's no answer to the question.
*source_port*, an ``int``, the port from which to send the message.
*search*, a ``bool`` or ``None``, determines whether the search
list configured in the system's resolver configuration are
used. The default is ``None``, which causes the value of
the resolver's ``use_search_by_default`` attribute to be used.
Raises ``dns.resolver.NXDOMAIN`` if the query name does not exist.
Raises ``dns.resolver.YXDOMAIN`` if the query name is too long after
DNAME substitution.
Raises ``dns.resolver.NoAnswer`` if *raise_on_no_answer* is
``True`` and the query name exists but has no RRset of the
desired type and class.
Raises ``dns.resolver.NoNameservers`` if no non-broken
nameservers are available to answer the question.
Returns a ``dns.resolver.Answer`` instance.
"""
resolution = dns.resolver._Resolution(self, qname, rdtype, rdclass, tcp,
raise_on_no_answer, search)
while True:
(request, answer) = resolution.next_request()
if answer:
# cache hit!
return answer
loops = 1
done = False
while not done:
(nameserver, port, tcp, backoff) = resolution.next_nameserver()
if backoff:
loops += 1
if loops >= 5:
raise TooManyAttempts
await trio.sleep(backoff)
try:
with trio.fail_after(self.timeout):
if dns.inet.is_address(nameserver):
if tcp:
response = await \
_stream(request, nameserver,
port=port,
source=source,
source_port=source_port)
else:
response = await \
_udp(request,
nameserver,
port=port,
source=source,
source_port=source_port)
else:
# We don't do DoH yet.
raise NotImplementedError
(answer, done) = resolution.query_result(response, None)
if answer:
return answer
except Exception as ex:
(_, done) = resolution.query_result(None, ex)
async def query(self, *args, **kwargs):
# We have to define something here as we don't want to inherit the
# parent's query().
raise NotImplementedError
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)
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, search=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 ``dns.trio.resolver.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, search)
async def zone_for_name(name, rdclass=dns.rdataclass.IN, tcp=False,
resolver=None):
"""Find the name of the zone which contains the specified name.
*name*, an absolute ``dns.name.Name`` or ``str``, the query name.
*rdclass*, an ``int``, the query class.
*tcp*, a ``bool``. If ``True``, use TCP to make the query.
*resolver*, a ``dns.trio.resolver.Resolver`` or ``None``, the
resolver to use. If ``None``, the default resolver is used.
Raises ``dns.resolver.NoRootSOA`` if there is no SOA RR at the DNS
root. (This is only likely to happen if you're using non-default
root servers in your network and they are misconfigured.)
Returns a ``dns.name.Name``.
"""
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)
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:
raise NoRootSOA
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