Bring back use of dnspython for A/AAAA resolution.
This is behind a use_dnspython flag, however, so it can be disabled as desired.
This commit is contained in:
Lance Stout
parent
02f79fc94b
commit
ad91a8cd5e
2 changed files with 90 additions and 27 deletions
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@ -32,10 +32,10 @@ log = logging.getLogger(__name__)
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#: cd dnspython
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#: git checkout python3
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#: python3 setup.py install
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USE_DNSPYTHON = False
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DNSPYTHON_AVAILABLE = False
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try:
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import dns.resolver
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USE_DNSPYTHON = True
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DNSPYTHON_AVAILABLE = True
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except ImportError as e:
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log.debug("Could not find dnspython package. " + \
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"Not all features will be available")
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@ -47,13 +47,13 @@ def default_resolver():
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:returns: A :class:`dns.resolver.Resolver` object if dnspython
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is available. Otherwise, ``None``.
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"""
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if USE_DNSPYTHON:
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if DNSPYTHON_AVAILABLE:
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return dns.resolver.get_default_resolver()
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return None
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def resolve(host, port=None, service=None, proto='tcp',
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resolver=None, use_ipv6=True):
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resolver=None, use_ipv6=True, use_dnspython=True):
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"""Peform DNS resolution for a given hostname.
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Resolution may perform SRV record lookups if a service and protocol
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@ -77,6 +77,9 @@ def resolve(host, port=None, service=None, proto='tcp',
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:param use_ipv6: Optionally control the use of IPv6 in situations
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where it is either not available, or performance
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is degraded. Defaults to ``True``.
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:param use_dnspython: Optionally control if dnspython is used to make
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the DNS queries instead of the built-in DNS
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library.
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:type host: string
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:type port: int
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@ -84,14 +87,22 @@ def resolve(host, port=None, service=None, proto='tcp',
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:type proto: string
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:type resolver: :class:`dns.resolver.Resolver`
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:type use_ipv6: bool
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:type use_dnspython: bool
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:return: An iterable of IP address, port pairs in the order
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dictated by SRV priorities and weights, if applicable.
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"""
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if not use_dnspython:
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if DNSPYTHON_AVAILABLE:
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log.debug("DNS: Not using dnspython, but dnspython is installed.")
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else:
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log.debug("DNS: Not using dnspython.")
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if not use_ipv6:
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log.debug("DNS: Use of IPv6 has been disabled.")
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if resolver is None and USE_DNSPYTHON:
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if resolver is None and DNSPYTHON_AVAILABLE and use_dnspython:
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resolver = dns.resolver.get_default_resolver()
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# An IPv6 literal is allowed to be enclosed in square brackets, but
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@ -122,7 +133,9 @@ def resolve(host, port=None, service=None, proto='tcp',
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if not service:
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hosts = [(host, port)]
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else:
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hosts = get_SRV(host, port, service, proto, resolver=resolver)
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hosts = get_SRV(host, port, service, proto,
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resolver=resolver,
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use_dnspython=use_dnspython)
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for host, port in hosts:
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results = []
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@ -131,16 +144,18 @@ def resolve(host, port=None, service=None, proto='tcp',
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results.append((host, '::1', port))
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results.append((host, '127.0.0.1', port))
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if use_ipv6:
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for address in get_AAAA(host):
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for address in get_AAAA(host, resolver=resolver,
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use_dnspython=use_dnspython):
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results.append((host, address, port))
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for address in get_A(host):
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for address in get_A(host, resolver=resolver,
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use_dnspython=use_dnspython):
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results.append((host, address, port))
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for host, address, port in results:
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yield host, address, port
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def get_A(host):
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def get_A(host, resolver=None, use_dnspython=True):
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"""Lookup DNS A records for a given host.
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If ``resolver`` is not provided, or is ``None``, then resolution will
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@ -148,9 +163,13 @@ def get_A(host):
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:param host: The hostname to resolve for A record IPv4 addresses.
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:param resolver: Optional DNS resolver object to use for the query.
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:param use_dnspython: Optionally control if dnspython is used to make
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the DNS queries instead of the built-in DNS
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library.
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:type host: string
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:type resolver: :class:`dns.resolver.Resolver` or ``None``
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:type use_dnspython: bool
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:return: A list of IPv4 literals.
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"""
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@ -158,15 +177,32 @@ def get_A(host):
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# If not using dnspython, attempt lookup using the OS level
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# getaddrinfo() method.
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if resolver is None or not use_dnspython:
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try:
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recs = socket.getaddrinfo(host, None, socket.AF_INET,
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socket.SOCK_STREAM)
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return [rec[4][0] for rec in recs]
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except socket.gaierror:
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log.debug("DNS: Error retreiving A address info for %s." % host)
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return []
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# Using dnspython:
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try:
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recs = socket.getaddrinfo(host, None, socket.AF_INET,
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socket.SOCK_STREAM)
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return [rec[4][0] for rec in recs]
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except socket.gaierror:
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log.debug("DNS: Error retreiving A address info for %s." % host)
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recs = resolver.query(host, dns.rdatatype.A)
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return [rec.to_text() for rec in recs]
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except (dns.resolver.NXDOMAIN, dns.resolver.NoAnswer):
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log.debug("DNS: No A records for %s" % host)
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return []
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except dns.exception.Timeout:
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log.debug("DNS: A record resolution timed out for %s" % host)
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return []
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except dns.exception.DNSException as e:
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log.debug("DNS: Error querying A records for %s" % host)
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log.exception(e)
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return []
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def get_AAAA(host):
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def get_AAAA(host, resolver=None, use_dnspython=True):
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"""Lookup DNS AAAA records for a given host.
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If ``resolver`` is not provided, or is ``None``, then resolution will
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@ -174,9 +210,13 @@ def get_AAAA(host):
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:param host: The hostname to resolve for AAAA record IPv6 addresses.
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:param resolver: Optional DNS resolver object to use for the query.
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:param use_dnspython: Optionally control if dnspython is used to make
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the DNS queries instead of the built-in DNS
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library.
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:type host: string
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:type resolver: :class:`dns.resolver.Resolver` or ``None``
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:type use_dnspython: bool
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:return: A list of IPv6 literals.
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"""
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@ -184,19 +224,36 @@ def get_AAAA(host):
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# If not using dnspython, attempt lookup using the OS level
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# getaddrinfo() method.
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if not socket.has_ipv6:
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log.debug("Unable to query %s for AAAA records: IPv6 is not supported", host)
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return []
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if resolver is None or not use_dnspython:
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if not socket.has_ipv6:
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log.debug("Unable to query %s for AAAA records: IPv6 is not supported", host)
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return []
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try:
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recs = socket.getaddrinfo(host, None, socket.AF_INET6,
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socket.SOCK_STREAM)
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return [rec[4][0] for rec in recs]
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except (OSError, socket.gaierror):
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log.debug("DNS: Error retreiving AAAA address " + \
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"info for %s." % host)
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return []
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# Using dnspython:
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try:
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recs = socket.getaddrinfo(host, None, socket.AF_INET6,
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socket.SOCK_STREAM)
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return [rec[4][0] for rec in recs]
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except (OSError, socket.gaierror):
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log.debug("DNS: Error retreiving AAAA address " + \
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"info for %s." % host)
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recs = resolver.query(host, dns.rdatatype.AAAA)
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return [rec.to_text() for rec in recs]
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except (dns.resolver.NXDOMAIN, dns.resolver.NoAnswer):
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log.debug("DNS: No AAAA records for %s" % host)
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return []
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except dns.exception.Timeout:
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log.debug("DNS: AAAA record resolution timed out for %s" % host)
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return []
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except dns.exception.DNSException as e:
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log.debug("DNS: Error querying AAAA records for %s" % host)
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log.exception(e)
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return []
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def get_SRV(host, port, service, proto='tcp', resolver=None):
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def get_SRV(host, port, service, proto='tcp', resolver=None, use_dnspython=True):
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"""Perform SRV record resolution for a given host.
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.. note::
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@ -222,7 +279,7 @@ def get_SRV(host, port, service, proto='tcp', resolver=None):
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:return: A list of hostname, port pairs in the order dictacted
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by SRV priorities and weights.
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"""
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if resolver is None:
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if resolver is None or not use_dnspython:
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log.warning("DNS: dnspython not found. Can not use SRV lookup.")
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return [(host, port)]
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@ -224,6 +224,11 @@ class XMLStream(object):
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#: If set to ``True``, attempt to use IPv6.
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self.use_ipv6 = True
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#: If set to ``True``, allow using the ``dnspython`` DNS library
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#: if available. If set to ``False``, the builtin DNS resolver
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#: will be used, even if ``dnspython`` is installed.
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self.use_dnspython = True
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#: Use CDATA for escaping instead of XML entities. Defaults
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#: to ``False``.
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self.use_cdata = False
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@ -1081,7 +1086,8 @@ class XMLStream(object):
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return resolve(domain, port, service=self.dns_service,
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resolver=resolver,
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use_ipv6=self.use_ipv6)
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use_ipv6=self.use_ipv6,
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use_dnspython=self.use_dnspython)
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def pick_dns_answer(self, domain, port=None):
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"""Pick a server and port from DNS answers.
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