'''greendns - non-blocking DNS support for Eventlet ''' # Portions of this code taken from the gogreen project: # http://github.com/slideinc/gogreen # # Copyright (c) 2005-2010 Slide, Inc. # All rights reserved. # # Redistribution and use in source and binary forms, with or without # modification, are permitted provided that the following conditions are # met: # # * Redistributions of source code must retain the above copyright # notice, this list of conditions and the following disclaimer. # * Redistributions in binary form must reproduce the above # copyright notice, this list of conditions and the following # disclaimer in the documentation and/or other materials provided # with the distribution. # * Neither the name of the author nor the names of other # contributors may be used to endorse or promote products derived # from this software without specific prior written permission. # # THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS # "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT # LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR # A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT # OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, # SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT # LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, # DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY # THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT # (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE # OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. import struct from eventlet import patcher from eventlet.green import _socket_nodns from eventlet.green import os from eventlet.green import time from eventlet.green import select from eventlet.support import six dns = patcher.import_patched('dns', select=select, time=time, os=os, socket=_socket_nodns) dns.resolver = patcher.import_patched('dns.resolver', select=select, time=time, os=os, socket=_socket_nodns) for pkg in ('dns.entropy', 'dns.inet', 'dns.query'): setattr(dns, pkg.split('.')[1], patcher.import_patched(pkg, select=select, time=time, os=os, socket=_socket_nodns)) import dns.rdtypes for pkg in ['dns.rdtypes.IN', 'dns.rdtypes.ANY']: setattr(dns.rdtypes, pkg.split('.')[-1], patcher.import_patched(pkg)) for pkg in ['dns.rdtypes.IN.A', 'dns.rdtypes.IN.AAAA']: setattr(dns.rdtypes.IN, pkg.split('.')[-1], patcher.import_patched(pkg)) for pkg in ['dns.rdtypes.ANY.CNAME']: setattr(dns.rdtypes.ANY, pkg.split('.')[-1], patcher.import_patched(pkg)) socket = _socket_nodns DNS_QUERY_TIMEOUT = 10.0 HOSTS_TTL = 10.0 EAI_EAGAIN_ERROR = socket.gaierror(socket.EAI_AGAIN, 'Lookup timed out') EAI_NODATA_ERROR = socket.gaierror(socket.EAI_NODATA, 'No address associated with hostname') EAI_NONAME_ERROR = socket.gaierror(socket.EAI_NONAME, 'Name or service not known') def is_ipv4_addr(host): """Return True if host is a valid IPv4 address""" if not isinstance(host, six.string_types): return False try: dns.ipv4.inet_aton(host) except dns.exception.SyntaxError: return False else: return True def is_ipv6_addr(host): """Return True if host is a valid IPv6 address""" if not isinstance(host, six.string_types): return False try: dns.ipv6.inet_aton(host) except dns.exception.SyntaxError: return False else: return True def is_ip_addr(host): """Return True if host is a valid IPv4 or IPv6 address""" return is_ipv4_addr(host) or is_ipv6_addr(host) class HostsAnswer(dns.resolver.Answer): """Answer class for HostsResolver object""" def __init__(self, qname, rdtype, rdclass, rrset, raise_on_no_answer=True): """Create a new answer :qname: A dns.name.Name instance of the query name :rdtype: The rdatatype of the query :rdclass: The rdataclass of the query :rrset: The dns.rrset.RRset with the response, must have ttl attribute :raise_on_no_answer: Whether to raise dns.resolver.NoAnswer if no answer. """ self.response = None self.qname = qname self.rdtype = rdtype self.rdclass = rdclass self.canonical_name = qname if not rrset and raise_on_no_answer: raise dns.resolver.NoAnswer() self.rrset = rrset self.expiration = (time.time() + rrset.ttl if hasattr(rrset, 'ttl') else 0) class HostsResolver(object): """Class to parse the hosts file Attributes ---------- :fname: The filename of the hosts file in use. :interval: The time between checking for hosts file modification """ def __init__(self, fname=None, interval=HOSTS_TTL): self._v4 = {} # name -> ipv4 self._v6 = {} # name -> ipv6 self._aliases = {} # name -> cannonical_name self.interval = interval self.fname = fname if fname is None: if os.name == 'posix': self.fname = '/etc/hosts' elif os.name == 'nt': self.fname = os.path.expandvars( r'%SystemRoot%\system32\drivers\etc\hosts') self._last_load = 0 if self.fname: self._load() def _readlines(self): """Read the contents of the hosts file Return list of lines, comment lines and empty lines are excluded. Note that this performs disk I/O so can be blocking. """ lines = [] try: with open(self.fname, 'rU') as fp: for line in fp: line = line.strip() if line and line[0] != '#': lines.append(line) except (IOError, OSError): pass return lines def _load(self): """Load hosts file This will unconditionally (re)load the data from the hosts file. """ lines = self._readlines() self._v4.clear() self._v6.clear() self._aliases.clear() for line in lines: parts = line.split() if len(parts) < 2: continue ip = parts.pop(0) if is_ipv4_addr(ip): ipmap = self._v4 elif is_ipv6_addr(ip): if ip.startswith('fe80'): # Do not use link-local addresses, OSX stores these here continue ipmap = self._v6 else: continue cname = parts.pop(0) ipmap[cname] = ip for alias in parts: ipmap[alias] = ip self._aliases[alias] = cname self._last_load = time.time() def query(self, qname, rdtype=dns.rdatatype.A, rdclass=dns.rdataclass.IN, tcp=False, source=None, raise_on_no_answer=True): """Query the hosts file The known rdtypes are dns.rdatatype.A, dns.rdatatype.AAAA and dns.rdatatype.CNAME. The ``rdclass`` parameter must be dns.rdataclass.IN while the ``tcp`` and ``source`` parameters are ignored. Return a HostAnswer instance or raise a dns.resolver.NoAnswer exception. """ now = time.time() if self._last_load + self.interval < now: self._load() rdclass = dns.rdataclass.IN if isinstance(qname, six.string_types): name = qname qname = dns.name.from_text(qname) else: name = str(qname) rrset = dns.rrset.RRset(qname, rdclass, rdtype) rrset.ttl = self._last_load + self.interval - now if rdclass == dns.rdataclass.IN and rdtype == dns.rdatatype.A: addr = self._v4.get(name) if not addr and qname.is_absolute(): addr = self._v4.get(name[:-1]) if addr: rrset.add(dns.rdtypes.IN.A.A(rdclass, rdtype, addr)) elif rdclass == dns.rdataclass.IN and rdtype == dns.rdatatype.AAAA: addr = self._v6.get(name) if not addr and qname.is_absolute(): addr = self._v6.get(name[:-1]) if addr: rrset.add(dns.rdtypes.IN.AAAA.AAAA(rdclass, rdtype, addr)) elif rdclass == dns.rdataclass.IN and rdtype == dns.rdatatype.CNAME: cname = self._aliases.get(name) if not cname and qname.is_absolute(): cname = self._aliases.get(name[:-1]) if cname: rrset.add(dns.rdtypes.ANY.CNAME.CNAME( rdclass, rdtype, dns.name.from_text(cname))) return HostsAnswer(qname, rdtype, rdclass, rrset, raise_on_no_answer) def getaliases(self, hostname): """Return a list of all the aliases of a given cname""" # Due to the way store aliases this is a bit inefficient, this # clearly was an afterthought. But this is only used by # gethostbyname_ex so it's probably fine. aliases = [] if hostname in self._aliases: cannon = self._aliases[hostname] else: cannon = hostname aliases.append(cannon) for alias, cname in six.iteritems(self._aliases): if cannon == cname: aliases.append(alias) aliases.remove(hostname) return aliases class ResolverProxy(object): """Resolver class which can also use /etc/hosts Initialise with a HostsResolver instance in order for it to also use the hosts file. """ def __init__(self, hosts_resolver=None, filename='/etc/resolv.conf'): """Initialise the resolver proxy :param hosts_resolver: An instance of HostsResolver to use. :param filename: The filename containing the resolver configuration. The default value is correct for both UNIX and Windows, on Windows it will result in the configuration being read from the Windows registry. """ self._hosts = hosts_resolver self._filename = filename self._resolver = dns.resolver.Resolver(filename=self._filename) self._resolver.cache = dns.resolver.LRUCache() def clear(self): self._resolver = dns.resolver.Resolver(filename=self._filename) self._resolver.cache = dns.resolver.Cache() def query(self, qname, rdtype=dns.rdatatype.A, rdclass=dns.rdataclass.IN, tcp=False, source=None, raise_on_no_answer=True): """Query the resolver, using /etc/hosts if enabled""" if qname is None: qname = '0.0.0.0' if rdclass == dns.rdataclass.IN and self._hosts: try: return self._hosts.query(qname, rdtype) except dns.resolver.NoAnswer: pass return self._resolver.query(qname, rdtype, rdclass, tcp, source, raise_on_no_answer) def getaliases(self, hostname): """Return a list of all the aliases of a given hostname""" if self._hosts: aliases = self._hosts.getaliases(hostname) else: aliases = [] while True: try: ans = self._resolver.query(hostname, dns.rdatatype.CNAME) except (dns.resolver.NoAnswer, dns.resolver.NXDOMAIN): break else: aliases.extend(str(rr.target) for rr in ans.rrset) hostname = ans[0].target return aliases resolver = ResolverProxy(hosts_resolver=HostsResolver()) def resolve(name, family=socket.AF_INET, raises=True): """Resolve a name for a given family using the global resolver proxy This method is called by the global getaddrinfo() function. Return a dns.resolver.Answer instance. If there is no answer it's rrset will be emtpy. """ if family == socket.AF_INET: rdtype = dns.rdatatype.A elif family == socket.AF_INET6: rdtype = dns.rdatatype.AAAA else: raise socket.gaierror(socket.EAI_FAMILY, 'Address family not supported') try: try: return resolver.query(name, rdtype, raise_on_no_answer=raises) except dns.resolver.NXDOMAIN: if not raises: return HostsAnswer(dns.name.Name(name), rdtype, dns.rdataclass.IN, None, False) raise except dns.exception.Timeout: raise EAI_EAGAIN_ERROR except dns.exception.DNSException: raise EAI_NODATA_ERROR def resolve_cname(host): """Return the canonical name of a hostname""" try: ans = resolver.query(host, dns.rdatatype.CNAME) except dns.resolver.NoAnswer: return host except dns.exception.Timeout: raise EAI_EAGAIN_ERROR except dns.exception.DNSException: raise EAI_NODATA_ERROR else: return str(ans[0].target) def getaliases(host): """Return a list of for aliases for the given hostname This method does translate the dnspython exceptions into socket.gaierror exceptions. If no aliases are available an empty list will be returned. """ try: return resolver.getaliases(host) except dns.exception.Timeout: raise EAI_EAGAIN_ERROR except dns.exception.DNSException: raise EAI_NODATA_ERROR def _getaddrinfo_lookup(host, family, flags): """Resolve a hostname to a list of addresses Helper function for getaddrinfo. """ if flags & socket.AI_NUMERICHOST: raise EAI_NONAME_ERROR addrs = [] if family == socket.AF_UNSPEC: for qfamily in [socket.AF_INET6, socket.AF_INET]: answer = resolve(host, qfamily, False) if answer.rrset: addrs.extend([rr.address for rr in answer.rrset]) elif family == socket.AF_INET6 and flags & socket.AI_V4MAPPED: answer = resolve(host, socket.AF_INET6, False) if answer.rrset: addrs = [rr.address for rr in answer.rrset] if not addrs or flags & socket.AI_ALL: answer = resolve(host, socket.AF_INET, False) if answer.rrset: addrs = ['::ffff:' + rr.address for rr in answer.rrset] else: answer = resolve(host, family, False) if answer.rrset: addrs = [rr.address for rr in answer.rrset] return str(answer.qname), addrs def getaddrinfo(host, port, family=0, socktype=0, proto=0, flags=0): """Replacement for Python's socket.getaddrinfo This does the A and AAAA lookups asynchronously after which it calls the OS' getaddrinfo(3) using the AI_NUMERICHOST flag. This flag ensures getaddrinfo(3) does not use the network itself and allows us to respect all the other arguments like the native OS. """ if isinstance(host, six.string_types): host = host.encode('idna').decode('ascii') if host is not None and not is_ip_addr(host): qname, addrs = _getaddrinfo_lookup(host, family, flags) else: qname = host addrs = [host] aiflags = (flags | socket.AI_NUMERICHOST) & (0xffff ^ socket.AI_CANONNAME) res = [] err = None for addr in addrs: try: ai = socket.getaddrinfo(addr, port, family, socktype, proto, aiflags) except socket.error as e: if flags & socket.AI_ADDRCONFIG: err = e continue raise res.extend(ai) if not res: if err: raise err raise socket.gaierror(socket.EAI_NONAME, 'No address found') if flags & socket.AI_CANONNAME: if not is_ip_addr(qname): qname = resolve_cname(qname).encode('ascii').decode('idna') ai = res[0] res[0] = (ai[0], ai[1], ai[2], qname, ai[4]) return res def gethostbyname(hostname): """Replacement for Python's socket.gethostbyname""" if is_ipv4_addr(hostname): return hostname rrset = resolve(hostname) return rrset[0].address def gethostbyname_ex(hostname): """Replacement for Python's socket.gethostbyname_ex""" if is_ipv4_addr(hostname): return (hostname, [], [hostname]) ans = resolve(hostname) aliases = getaliases(hostname) addrs = [rr.address for rr in ans.rrset] qname = str(ans.qname) if qname[-1] == '.': qname = qname[:-1] return (qname, aliases, addrs) def getnameinfo(sockaddr, flags): """Replacement for Python's socket.getnameinfo. Currently only supports IPv4. """ try: host, port = sockaddr except (ValueError, TypeError): if not isinstance(sockaddr, tuple): del sockaddr # to pass a stdlib test that is # hyper-careful about reference counts raise TypeError('getnameinfo() argument 1 must be a tuple') else: # must be ipv6 sockaddr, pretending we don't know how to resolve it raise EAI_NONAME_ERROR if (flags & socket.NI_NAMEREQD) and (flags & socket.NI_NUMERICHOST): # Conflicting flags. Punt. raise EAI_NONAME_ERROR if is_ipv4_addr(host): try: rrset = resolver.query( dns.reversename.from_address(host), dns.rdatatype.PTR) if len(rrset) > 1: raise socket.error('sockaddr resolved to multiple addresses') host = rrset[0].target.to_text(omit_final_dot=True) except dns.exception.Timeout: if flags & socket.NI_NAMEREQD: raise EAI_EAGAIN_ERROR except dns.exception.DNSException: if flags & socket.NI_NAMEREQD: raise EAI_NONAME_ERROR else: try: rrset = resolver.query(host) if len(rrset) > 1: raise socket.error('sockaddr resolved to multiple addresses') if flags & socket.NI_NUMERICHOST: host = rrset[0].address except dns.exception.Timeout: raise EAI_EAGAIN_ERROR except dns.exception.DNSException: raise socket.gaierror( (socket.EAI_NODATA, 'No address associated with hostname')) if not (flags & socket.NI_NUMERICSERV): proto = (flags & socket.NI_DGRAM) and 'udp' or 'tcp' port = socket.getservbyport(port, proto) return (host, port) def _net_read(sock, count, expiration): """coro friendly replacement for dns.query._net_write Read the specified number of bytes from sock. Keep trying until we either get the desired amount, or we hit EOF. A Timeout exception will be raised if the operation is not completed by the expiration time. """ s = '' while count > 0: try: n = sock.recv(count) except socket.timeout: # Q: Do we also need to catch coro.CoroutineSocketWake and pass? if expiration - time.time() <= 0.0: raise dns.exception.Timeout if n == '': raise EOFError count = count - len(n) s = s + n return s def _net_write(sock, data, expiration): """coro friendly replacement for dns.query._net_write Write the specified data to the socket. A Timeout exception will be raised if the operation is not completed by the expiration time. """ current = 0 l = len(data) while current < l: try: current += sock.send(data[current:]) except socket.timeout: # Q: Do we also need to catch coro.CoroutineSocketWake and pass? if expiration - time.time() <= 0.0: raise dns.exception.Timeout def udp(q, where, timeout=DNS_QUERY_TIMEOUT, port=53, af=None, source=None, source_port=0, ignore_unexpected=False): """coro friendly replacement for dns.query.udp Return the response obtained after sending a query via UDP. @param q: the query @type q: dns.message.Message @param where: where to send the message @type where: string containing an IPv4 or IPv6 address @param timeout: The number of seconds to wait before the query times out. If None, the default, wait forever. @type timeout: float @param port: The port to which to send the message. The default is 53. @type port: int @param af: the address family to use. The default is None, which causes the address family to use to be inferred from the form of of where. If the inference attempt fails, AF_INET is used. @type af: int @rtype: dns.message.Message object @param source: source address. The default is the IPv4 wildcard address. @type source: string @param source_port: The port from which to send the message. The default is 0. @type source_port: int @param ignore_unexpected: If True, ignore responses from unexpected sources. The default is False. @type ignore_unexpected: bool""" wire = q.to_wire() if af is None: try: af = dns.inet.af_for_address(where) except: af = dns.inet.AF_INET if af == dns.inet.AF_INET: destination = (where, port) if source is not None: source = (source, source_port) elif af == dns.inet.AF_INET6: destination = (where, port, 0, 0) if source is not None: source = (source, source_port, 0, 0) s = socket.socket(af, socket.SOCK_DGRAM) s.settimeout(timeout) try: expiration = dns.query._compute_expiration(timeout) if source is not None: s.bind(source) try: s.sendto(wire, destination) except socket.timeout: # Q: Do we also need to catch coro.CoroutineSocketWake and pass? if expiration - time.time() <= 0.0: raise dns.exception.Timeout while 1: try: (wire, from_address) = s.recvfrom(65535) except socket.timeout: # Q: Do we also need to catch coro.CoroutineSocketWake and pass? if expiration - time.time() <= 0.0: raise dns.exception.Timeout if from_address == destination: break if not ignore_unexpected: raise dns.query.UnexpectedSource( 'got a response from %s instead of %s' % (from_address, destination)) finally: s.close() r = dns.message.from_wire(wire, keyring=q.keyring, request_mac=q.mac) if not q.is_response(r): raise dns.query.BadResponse() return r def tcp(q, where, timeout=DNS_QUERY_TIMEOUT, port=53, af=None, source=None, source_port=0): """coro friendly replacement for dns.query.tcp Return the response obtained after sending a query via TCP. @param q: the query @type q: dns.message.Message object @param where: where to send the message @type where: string containing an IPv4 or IPv6 address @param timeout: The number of seconds to wait before the query times out. If None, the default, wait forever. @type timeout: float @param port: The port to which to send the message. The default is 53. @type port: int @param af: the address family to use. The default is None, which causes the address family to use to be inferred from the form of of where. If the inference attempt fails, AF_INET is used. @type af: int @rtype: dns.message.Message object @param source: source address. The default is the IPv4 wildcard address. @type source: string @param source_port: The port from which to send the message. The default is 0. @type source_port: int""" wire = q.to_wire() if af is None: try: af = dns.inet.af_for_address(where) except: af = dns.inet.AF_INET if af == dns.inet.AF_INET: destination = (where, port) if source is not None: source = (source, source_port) elif af == dns.inet.AF_INET6: destination = (where, port, 0, 0) if source is not None: source = (source, source_port, 0, 0) s = socket.socket(af, socket.SOCK_STREAM) s.settimeout(timeout) try: expiration = dns.query._compute_expiration(timeout) if source is not None: s.bind(source) try: s.connect(destination) except socket.timeout: # Q: Do we also need to catch coro.CoroutineSocketWake and pass? if expiration - time.time() <= 0.0: raise dns.exception.Timeout l = len(wire) # copying the wire into tcpmsg is inefficient, but lets us # avoid writev() or doing a short write that would get pushed # onto the net tcpmsg = struct.pack("!H", l) + wire _net_write(s, tcpmsg, expiration) ldata = _net_read(s, 2, expiration) (l,) = struct.unpack("!H", ldata) wire = _net_read(s, l, expiration) finally: s.close() r = dns.message.from_wire(wire, keyring=q.keyring, request_mac=q.mac) if not q.is_response(r): raise dns.query.BadResponse() return r def reset(): resolver.clear() # Install our coro-friendly replacements for the tcp and udp query methods. dns.query.tcp = tcp dns.query.udp = udp