resolver.py 51 KB

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  1. # Copyright (C) 2003-2007, 2009-2011 Nominum, Inc.
  2. #
  3. # Permission to use, copy, modify, and distribute this software and its
  4. # documentation for any purpose with or without fee is hereby granted,
  5. # provided that the above copyright notice and this permission notice
  6. # appear in all copies.
  7. #
  8. # THE SOFTWARE IS PROVIDED "AS IS" AND NOMINUM DISCLAIMS ALL WARRANTIES
  9. # WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
  10. # MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL NOMINUM BE LIABLE FOR
  11. # ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
  12. # WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
  13. # ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT
  14. # OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
  15. """DNS stub resolver.
  16. @var default_resolver: The default resolver object
  17. @type default_resolver: dns.resolver.Resolver object"""
  18. import socket
  19. import sys
  20. import time
  21. import random
  22. try:
  23. import threading as _threading
  24. except ImportError:
  25. import dummy_threading as _threading
  26. import dns.exception
  27. import dns.flags
  28. import dns.ipv4
  29. import dns.ipv6
  30. import dns.message
  31. import dns.name
  32. import dns.query
  33. import dns.rcode
  34. import dns.rdataclass
  35. import dns.rdatatype
  36. import dns.reversename
  37. import dns.tsig
  38. from ._compat import xrange, string_types
  39. if sys.platform == 'win32':
  40. try:
  41. import winreg as _winreg
  42. except ImportError:
  43. import _winreg # pylint: disable=import-error
  44. class NXDOMAIN(dns.exception.DNSException):
  45. """The DNS query name does not exist."""
  46. supp_kwargs = set(['qnames', 'responses'])
  47. fmt = None # we have our own __str__ implementation
  48. def _check_kwargs(self, qnames, responses=None):
  49. if not isinstance(qnames, (list, tuple, set)):
  50. raise AttributeError("qnames must be a list, tuple or set")
  51. if len(qnames) == 0:
  52. raise AttributeError("qnames must contain at least one element")
  53. if responses is None:
  54. responses = {}
  55. elif not isinstance(responses, dict):
  56. raise AttributeError("responses must be a dict(qname=response)")
  57. kwargs = dict(qnames=qnames, responses=responses)
  58. return kwargs
  59. def __str__(self):
  60. if 'qnames' not in self.kwargs:
  61. return super(NXDOMAIN, self).__str__()
  62. qnames = self.kwargs['qnames']
  63. if len(qnames) > 1:
  64. msg = 'None of DNS query names exist'
  65. else:
  66. msg = self.__doc__[:-1]
  67. qnames = ', '.join(map(str, qnames))
  68. return "%s: %s" % (msg, qnames)
  69. def canonical_name(self):
  70. if not 'qnames' in self.kwargs:
  71. raise TypeError("parametrized exception required")
  72. IN = dns.rdataclass.IN
  73. CNAME = dns.rdatatype.CNAME
  74. cname = None
  75. for qname in self.kwargs['qnames']:
  76. response = self.kwargs['responses'][qname]
  77. for answer in response.answer:
  78. if answer.rdtype != CNAME or answer.rdclass != IN:
  79. continue
  80. cname = answer.items[0].target.to_text()
  81. if cname is not None:
  82. return dns.name.from_text(cname)
  83. return self.kwargs['qnames'][0]
  84. canonical_name = property(canonical_name, doc=(
  85. "Return the unresolved canonical name."))
  86. def __add__(self, e_nx):
  87. """Augment by results from another NXDOMAIN exception."""
  88. qnames0 = list(self.kwargs.get('qnames', []))
  89. responses0 = dict(self.kwargs.get('responses', {}))
  90. responses1 = e_nx.kwargs.get('responses', {})
  91. for qname1 in e_nx.kwargs.get('qnames', []):
  92. if qname1 not in qnames0:
  93. qnames0.append(qname1)
  94. if qname1 in responses1:
  95. responses0[qname1] = responses1[qname1]
  96. return NXDOMAIN(qnames=qnames0, responses=responses0)
  97. class YXDOMAIN(dns.exception.DNSException):
  98. """The DNS query name is too long after DNAME substitution."""
  99. # The definition of the Timeout exception has moved from here to the
  100. # dns.exception module. We keep dns.resolver.Timeout defined for
  101. # backwards compatibility.
  102. Timeout = dns.exception.Timeout
  103. class NoAnswer(dns.exception.DNSException):
  104. """The DNS response does not contain an answer to the question."""
  105. fmt = 'The DNS response does not contain an answer ' + \
  106. 'to the question: {query}'
  107. supp_kwargs = set(['response'])
  108. def _fmt_kwargs(self, **kwargs):
  109. return super(NoAnswer, self)._fmt_kwargs(
  110. query=kwargs['response'].question)
  111. class NoNameservers(dns.exception.DNSException):
  112. """All nameservers failed to answer the query.
  113. errors: list of servers and respective errors
  114. The type of errors is
  115. [(server ip address, any object convertible to string)].
  116. Non-empty errors list will add explanatory message ()
  117. """
  118. msg = "All nameservers failed to answer the query."
  119. fmt = "%s {query}: {errors}" % msg[:-1]
  120. supp_kwargs = set(['request', 'errors'])
  121. def _fmt_kwargs(self, **kwargs):
  122. srv_msgs = []
  123. for err in kwargs['errors']:
  124. srv_msgs.append('Server %s %s port %s answered %s' % (err[0],
  125. 'TCP' if err[1] else 'UDP', err[2], err[3]))
  126. return super(NoNameservers, self)._fmt_kwargs(
  127. query=kwargs['request'].question, errors='; '.join(srv_msgs))
  128. class NotAbsolute(dns.exception.DNSException):
  129. """An absolute domain name is required but a relative name was provided."""
  130. class NoRootSOA(dns.exception.DNSException):
  131. """There is no SOA RR at the DNS root name. This should never happen!"""
  132. class NoMetaqueries(dns.exception.DNSException):
  133. """DNS metaqueries are not allowed."""
  134. class Answer(object):
  135. """DNS stub resolver answer
  136. Instances of this class bundle up the result of a successful DNS
  137. resolution.
  138. For convenience, the answer object implements much of the sequence
  139. protocol, forwarding to its rrset. E.g. "for a in answer" is
  140. equivalent to "for a in answer.rrset", "answer[i]" is equivalent
  141. to "answer.rrset[i]", and "answer[i:j]" is equivalent to
  142. "answer.rrset[i:j]".
  143. Note that CNAMEs or DNAMEs in the response may mean that answer
  144. node's name might not be the query name.
  145. @ivar qname: The query name
  146. @type qname: dns.name.Name object
  147. @ivar rdtype: The query type
  148. @type rdtype: int
  149. @ivar rdclass: The query class
  150. @type rdclass: int
  151. @ivar response: The response message
  152. @type response: dns.message.Message object
  153. @ivar rrset: The answer
  154. @type rrset: dns.rrset.RRset object
  155. @ivar expiration: The time when the answer expires
  156. @type expiration: float (seconds since the epoch)
  157. @ivar canonical_name: The canonical name of the query name
  158. @type canonical_name: dns.name.Name object
  159. """
  160. def __init__(self, qname, rdtype, rdclass, response,
  161. raise_on_no_answer=True):
  162. self.qname = qname
  163. self.rdtype = rdtype
  164. self.rdclass = rdclass
  165. self.response = response
  166. min_ttl = -1
  167. rrset = None
  168. for count in xrange(0, 15):
  169. try:
  170. rrset = response.find_rrset(response.answer, qname,
  171. rdclass, rdtype)
  172. if min_ttl == -1 or rrset.ttl < min_ttl:
  173. min_ttl = rrset.ttl
  174. break
  175. except KeyError:
  176. if rdtype != dns.rdatatype.CNAME:
  177. try:
  178. crrset = response.find_rrset(response.answer,
  179. qname,
  180. rdclass,
  181. dns.rdatatype.CNAME)
  182. if min_ttl == -1 or crrset.ttl < min_ttl:
  183. min_ttl = crrset.ttl
  184. for rd in crrset:
  185. qname = rd.target
  186. break
  187. continue
  188. except KeyError:
  189. if raise_on_no_answer:
  190. raise NoAnswer(response=response)
  191. if raise_on_no_answer:
  192. raise NoAnswer(response=response)
  193. if rrset is None and raise_on_no_answer:
  194. raise NoAnswer(response=response)
  195. self.canonical_name = qname
  196. self.rrset = rrset
  197. if rrset is None:
  198. while 1:
  199. # Look for a SOA RR whose owner name is a superdomain
  200. # of qname.
  201. try:
  202. srrset = response.find_rrset(response.authority, qname,
  203. rdclass, dns.rdatatype.SOA)
  204. if min_ttl == -1 or srrset.ttl < min_ttl:
  205. min_ttl = srrset.ttl
  206. if srrset[0].minimum < min_ttl:
  207. min_ttl = srrset[0].minimum
  208. break
  209. except KeyError:
  210. try:
  211. qname = qname.parent()
  212. except dns.name.NoParent:
  213. break
  214. self.expiration = time.time() + min_ttl
  215. def __getattr__(self, attr):
  216. if attr == 'name':
  217. return self.rrset.name
  218. elif attr == 'ttl':
  219. return self.rrset.ttl
  220. elif attr == 'covers':
  221. return self.rrset.covers
  222. elif attr == 'rdclass':
  223. return self.rrset.rdclass
  224. elif attr == 'rdtype':
  225. return self.rrset.rdtype
  226. else:
  227. raise AttributeError(attr)
  228. def __len__(self):
  229. return self.rrset and len(self.rrset) or 0
  230. def __iter__(self):
  231. return self.rrset and iter(self.rrset) or iter(tuple())
  232. def __getitem__(self, i):
  233. return self.rrset[i]
  234. def __delitem__(self, i):
  235. del self.rrset[i]
  236. class Cache(object):
  237. """Simple DNS answer cache.
  238. @ivar data: A dictionary of cached data
  239. @type data: dict
  240. @ivar cleaning_interval: The number of seconds between cleanings. The
  241. default is 300 (5 minutes).
  242. @type cleaning_interval: float
  243. @ivar next_cleaning: The time the cache should next be cleaned (in seconds
  244. since the epoch.)
  245. @type next_cleaning: float
  246. """
  247. def __init__(self, cleaning_interval=300.0):
  248. """Initialize a DNS cache.
  249. @param cleaning_interval: the number of seconds between periodic
  250. cleanings. The default is 300.0
  251. @type cleaning_interval: float.
  252. """
  253. self.data = {}
  254. self.cleaning_interval = cleaning_interval
  255. self.next_cleaning = time.time() + self.cleaning_interval
  256. self.lock = _threading.Lock()
  257. def _maybe_clean(self):
  258. """Clean the cache if it's time to do so."""
  259. now = time.time()
  260. if self.next_cleaning <= now:
  261. keys_to_delete = []
  262. for (k, v) in self.data.items():
  263. if v.expiration <= now:
  264. keys_to_delete.append(k)
  265. for k in keys_to_delete:
  266. del self.data[k]
  267. now = time.time()
  268. self.next_cleaning = now + self.cleaning_interval
  269. def get(self, key):
  270. """Get the answer associated with I{key}. Returns None if
  271. no answer is cached for the key.
  272. @param key: the key
  273. @type key: (dns.name.Name, int, int) tuple whose values are the
  274. query name, rdtype, and rdclass.
  275. @rtype: dns.resolver.Answer object or None
  276. """
  277. try:
  278. self.lock.acquire()
  279. self._maybe_clean()
  280. v = self.data.get(key)
  281. if v is None or v.expiration <= time.time():
  282. return None
  283. return v
  284. finally:
  285. self.lock.release()
  286. def put(self, key, value):
  287. """Associate key and value in the cache.
  288. @param key: the key
  289. @type key: (dns.name.Name, int, int) tuple whose values are the
  290. query name, rdtype, and rdclass.
  291. @param value: The answer being cached
  292. @type value: dns.resolver.Answer object
  293. """
  294. try:
  295. self.lock.acquire()
  296. self._maybe_clean()
  297. self.data[key] = value
  298. finally:
  299. self.lock.release()
  300. def flush(self, key=None):
  301. """Flush the cache.
  302. If I{key} is specified, only that item is flushed. Otherwise
  303. the entire cache is flushed.
  304. @param key: the key to flush
  305. @type key: (dns.name.Name, int, int) tuple or None
  306. """
  307. try:
  308. self.lock.acquire()
  309. if key is not None:
  310. if key in self.data:
  311. del self.data[key]
  312. else:
  313. self.data = {}
  314. self.next_cleaning = time.time() + self.cleaning_interval
  315. finally:
  316. self.lock.release()
  317. class LRUCacheNode(object):
  318. """LRUCache node.
  319. """
  320. def __init__(self, key, value):
  321. self.key = key
  322. self.value = value
  323. self.prev = self
  324. self.next = self
  325. def link_before(self, node):
  326. self.prev = node.prev
  327. self.next = node
  328. node.prev.next = self
  329. node.prev = self
  330. def link_after(self, node):
  331. self.prev = node
  332. self.next = node.next
  333. node.next.prev = self
  334. node.next = self
  335. def unlink(self):
  336. self.next.prev = self.prev
  337. self.prev.next = self.next
  338. class LRUCache(object):
  339. """Bounded least-recently-used DNS answer cache.
  340. This cache is better than the simple cache (above) if you're
  341. running a web crawler or other process that does a lot of
  342. resolutions. The LRUCache has a maximum number of nodes, and when
  343. it is full, the least-recently used node is removed to make space
  344. for a new one.
  345. @ivar data: A dictionary of cached data
  346. @type data: dict
  347. @ivar sentinel: sentinel node for circular doubly linked list of nodes
  348. @type sentinel: LRUCacheNode object
  349. @ivar max_size: The maximum number of nodes
  350. @type max_size: int
  351. """
  352. def __init__(self, max_size=100000):
  353. """Initialize a DNS cache.
  354. @param max_size: The maximum number of nodes to cache; the default is
  355. 100,000. Must be greater than 1.
  356. @type max_size: int
  357. """
  358. self.data = {}
  359. self.set_max_size(max_size)
  360. self.sentinel = LRUCacheNode(None, None)
  361. self.lock = _threading.Lock()
  362. def set_max_size(self, max_size):
  363. if max_size < 1:
  364. max_size = 1
  365. self.max_size = max_size
  366. def get(self, key):
  367. """Get the answer associated with I{key}. Returns None if
  368. no answer is cached for the key.
  369. @param key: the key
  370. @type key: (dns.name.Name, int, int) tuple whose values are the
  371. query name, rdtype, and rdclass.
  372. @rtype: dns.resolver.Answer object or None
  373. """
  374. try:
  375. self.lock.acquire()
  376. node = self.data.get(key)
  377. if node is None:
  378. return None
  379. # Unlink because we're either going to move the node to the front
  380. # of the LRU list or we're going to free it.
  381. node.unlink()
  382. if node.value.expiration <= time.time():
  383. del self.data[node.key]
  384. return None
  385. node.link_after(self.sentinel)
  386. return node.value
  387. finally:
  388. self.lock.release()
  389. def put(self, key, value):
  390. """Associate key and value in the cache.
  391. @param key: the key
  392. @type key: (dns.name.Name, int, int) tuple whose values are the
  393. query name, rdtype, and rdclass.
  394. @param value: The answer being cached
  395. @type value: dns.resolver.Answer object
  396. """
  397. try:
  398. self.lock.acquire()
  399. node = self.data.get(key)
  400. if node is not None:
  401. node.unlink()
  402. del self.data[node.key]
  403. while len(self.data) >= self.max_size:
  404. node = self.sentinel.prev
  405. node.unlink()
  406. del self.data[node.key]
  407. node = LRUCacheNode(key, value)
  408. node.link_after(self.sentinel)
  409. self.data[key] = node
  410. finally:
  411. self.lock.release()
  412. def flush(self, key=None):
  413. """Flush the cache.
  414. If I{key} is specified, only that item is flushed. Otherwise
  415. the entire cache is flushed.
  416. @param key: the key to flush
  417. @type key: (dns.name.Name, int, int) tuple or None
  418. """
  419. try:
  420. self.lock.acquire()
  421. if key is not None:
  422. node = self.data.get(key)
  423. if node is not None:
  424. node.unlink()
  425. del self.data[node.key]
  426. else:
  427. node = self.sentinel.next
  428. while node != self.sentinel:
  429. next = node.next
  430. node.prev = None
  431. node.next = None
  432. node = next
  433. self.data = {}
  434. finally:
  435. self.lock.release()
  436. class Resolver(object):
  437. """DNS stub resolver
  438. @ivar domain: The domain of this host
  439. @type domain: dns.name.Name object
  440. @ivar nameservers: A list of nameservers to query. Each nameserver is
  441. a string which contains the IP address of a nameserver.
  442. @type nameservers: list of strings
  443. @ivar search: The search list. If the query name is a relative name,
  444. the resolver will construct an absolute query name by appending the search
  445. names one by one to the query name.
  446. @type search: list of dns.name.Name objects
  447. @ivar port: The port to which to send queries. The default is 53.
  448. @type port: int
  449. @ivar timeout: The number of seconds to wait for a response from a
  450. server, before timing out.
  451. @type timeout: float
  452. @ivar lifetime: The total number of seconds to spend trying to get an
  453. answer to the question. If the lifetime expires, a Timeout exception
  454. will occur.
  455. @type lifetime: float
  456. @ivar keyring: The TSIG keyring to use. The default is None.
  457. @type keyring: dict
  458. @ivar keyname: The TSIG keyname to use. The default is None.
  459. @type keyname: dns.name.Name object
  460. @ivar keyalgorithm: The TSIG key algorithm to use. The default is
  461. dns.tsig.default_algorithm.
  462. @type keyalgorithm: string
  463. @ivar edns: The EDNS level to use. The default is -1, no Edns.
  464. @type edns: int
  465. @ivar ednsflags: The EDNS flags
  466. @type ednsflags: int
  467. @ivar payload: The EDNS payload size. The default is 0.
  468. @type payload: int
  469. @ivar flags: The message flags to use. The default is None (i.e. not
  470. overwritten)
  471. @type flags: int
  472. @ivar cache: The cache to use. The default is None.
  473. @type cache: dns.resolver.Cache object
  474. @ivar retry_servfail: should we retry a nameserver if it says SERVFAIL?
  475. The default is 'false'.
  476. @type retry_servfail: bool
  477. """
  478. def __init__(self, filename='/etc/resolv.conf', configure=True):
  479. """Initialize a resolver instance.
  480. @param filename: The filename of a configuration file in
  481. standard /etc/resolv.conf format. This parameter is meaningful
  482. only when I{configure} is true and the platform is POSIX.
  483. @type filename: string or file object
  484. @param configure: If True (the default), the resolver instance
  485. is configured in the normal fashion for the operating system
  486. the resolver is running on. (I.e. a /etc/resolv.conf file on
  487. POSIX systems and from the registry on Windows systems.)
  488. @type configure: bool"""
  489. self.domain = None
  490. self.nameservers = None
  491. self.nameserver_ports = None
  492. self.port = None
  493. self.search = None
  494. self.timeout = None
  495. self.lifetime = None
  496. self.keyring = None
  497. self.keyname = None
  498. self.keyalgorithm = None
  499. self.edns = None
  500. self.ednsflags = None
  501. self.payload = None
  502. self.cache = None
  503. self.flags = None
  504. self.retry_servfail = False
  505. self.rotate = False
  506. self.reset()
  507. if configure:
  508. if sys.platform == 'win32':
  509. self.read_registry()
  510. elif filename:
  511. self.read_resolv_conf(filename)
  512. def reset(self):
  513. """Reset all resolver configuration to the defaults."""
  514. self.domain = \
  515. dns.name.Name(dns.name.from_text(socket.gethostname())[1:])
  516. if len(self.domain) == 0:
  517. self.domain = dns.name.root
  518. self.nameservers = []
  519. self.nameserver_ports = {}
  520. self.port = 53
  521. self.search = []
  522. self.timeout = 2.0
  523. self.lifetime = 30.0
  524. self.keyring = None
  525. self.keyname = None
  526. self.keyalgorithm = dns.tsig.default_algorithm
  527. self.edns = -1
  528. self.ednsflags = 0
  529. self.payload = 0
  530. self.cache = None
  531. self.flags = None
  532. self.retry_servfail = False
  533. self.rotate = False
  534. def read_resolv_conf(self, f):
  535. """Process f as a file in the /etc/resolv.conf format. If f is
  536. a string, it is used as the name of the file to open; otherwise it
  537. is treated as the file itself."""
  538. if isinstance(f, string_types):
  539. try:
  540. f = open(f, 'r')
  541. except IOError:
  542. # /etc/resolv.conf doesn't exist, can't be read, etc.
  543. # We'll just use the default resolver configuration.
  544. self.nameservers = ['127.0.0.1']
  545. return
  546. want_close = True
  547. else:
  548. want_close = False
  549. try:
  550. for l in f:
  551. if len(l) == 0 or l[0] == '#' or l[0] == ';':
  552. continue
  553. tokens = l.split()
  554. # Any line containing less than 2 tokens is malformed
  555. if len(tokens) < 2:
  556. continue
  557. if tokens[0] == 'nameserver':
  558. self.nameservers.append(tokens[1])
  559. elif tokens[0] == 'domain':
  560. self.domain = dns.name.from_text(tokens[1])
  561. elif tokens[0] == 'search':
  562. for suffix in tokens[1:]:
  563. self.search.append(dns.name.from_text(suffix))
  564. elif tokens[0] == 'options':
  565. if 'rotate' in tokens[1:]:
  566. self.rotate = True
  567. finally:
  568. if want_close:
  569. f.close()
  570. if len(self.nameservers) == 0:
  571. self.nameservers.append('127.0.0.1')
  572. def _determine_split_char(self, entry):
  573. #
  574. # The windows registry irritatingly changes the list element
  575. # delimiter in between ' ' and ',' (and vice-versa) in various
  576. # versions of windows.
  577. #
  578. if entry.find(' ') >= 0:
  579. split_char = ' '
  580. elif entry.find(',') >= 0:
  581. split_char = ','
  582. else:
  583. # probably a singleton; treat as a space-separated list.
  584. split_char = ' '
  585. return split_char
  586. def _config_win32_nameservers(self, nameservers):
  587. """Configure a NameServer registry entry."""
  588. # we call str() on nameservers to convert it from unicode to ascii
  589. nameservers = str(nameservers)
  590. split_char = self._determine_split_char(nameservers)
  591. ns_list = nameservers.split(split_char)
  592. for ns in ns_list:
  593. if ns not in self.nameservers:
  594. self.nameservers.append(ns)
  595. def _config_win32_domain(self, domain):
  596. """Configure a Domain registry entry."""
  597. # we call str() on domain to convert it from unicode to ascii
  598. self.domain = dns.name.from_text(str(domain))
  599. def _config_win32_search(self, search):
  600. """Configure a Search registry entry."""
  601. # we call str() on search to convert it from unicode to ascii
  602. search = str(search)
  603. split_char = self._determine_split_char(search)
  604. search_list = search.split(split_char)
  605. for s in search_list:
  606. if s not in self.search:
  607. self.search.append(dns.name.from_text(s))
  608. def _config_win32_fromkey(self, key):
  609. """Extract DNS info from a registry key."""
  610. try:
  611. servers, rtype = _winreg.QueryValueEx(key, 'NameServer')
  612. except WindowsError: # pylint: disable=undefined-variable
  613. servers = None
  614. if servers:
  615. self._config_win32_nameservers(servers)
  616. try:
  617. dom, rtype = _winreg.QueryValueEx(key, 'Domain')
  618. if dom:
  619. self._config_win32_domain(dom)
  620. except WindowsError: # pylint: disable=undefined-variable
  621. pass
  622. else:
  623. try:
  624. servers, rtype = _winreg.QueryValueEx(key, 'DhcpNameServer')
  625. except WindowsError: # pylint: disable=undefined-variable
  626. servers = None
  627. if servers:
  628. self._config_win32_nameservers(servers)
  629. try:
  630. dom, rtype = _winreg.QueryValueEx(key, 'DhcpDomain')
  631. if dom:
  632. self._config_win32_domain(dom)
  633. except WindowsError: # pylint: disable=undefined-variable
  634. pass
  635. try:
  636. search, rtype = _winreg.QueryValueEx(key, 'SearchList')
  637. except WindowsError: # pylint: disable=undefined-variable
  638. search = None
  639. if search:
  640. self._config_win32_search(search)
  641. def read_registry(self):
  642. """Extract resolver configuration from the Windows registry."""
  643. lm = _winreg.ConnectRegistry(None, _winreg.HKEY_LOCAL_MACHINE)
  644. want_scan = False
  645. try:
  646. try:
  647. # XP, 2000
  648. tcp_params = _winreg.OpenKey(lm,
  649. r'SYSTEM\CurrentControlSet'
  650. r'\Services\Tcpip\Parameters')
  651. want_scan = True
  652. except EnvironmentError:
  653. # ME
  654. tcp_params = _winreg.OpenKey(lm,
  655. r'SYSTEM\CurrentControlSet'
  656. r'\Services\VxD\MSTCP')
  657. try:
  658. self._config_win32_fromkey(tcp_params)
  659. finally:
  660. tcp_params.Close()
  661. if want_scan:
  662. interfaces = _winreg.OpenKey(lm,
  663. r'SYSTEM\CurrentControlSet'
  664. r'\Services\Tcpip\Parameters'
  665. r'\Interfaces')
  666. try:
  667. i = 0
  668. while True:
  669. try:
  670. guid = _winreg.EnumKey(interfaces, i)
  671. i += 1
  672. key = _winreg.OpenKey(interfaces, guid)
  673. if not self._win32_is_nic_enabled(lm, guid, key):
  674. continue
  675. try:
  676. self._config_win32_fromkey(key)
  677. finally:
  678. key.Close()
  679. except EnvironmentError:
  680. break
  681. finally:
  682. interfaces.Close()
  683. finally:
  684. lm.Close()
  685. def _win32_is_nic_enabled(self, lm, guid, interface_key):
  686. # Look in the Windows Registry to determine whether the network
  687. # interface corresponding to the given guid is enabled.
  688. #
  689. # (Code contributed by Paul Marks, thanks!)
  690. #
  691. try:
  692. # This hard-coded location seems to be consistent, at least
  693. # from Windows 2000 through Vista.
  694. connection_key = _winreg.OpenKey(
  695. lm,
  696. r'SYSTEM\CurrentControlSet\Control\Network'
  697. r'\{4D36E972-E325-11CE-BFC1-08002BE10318}'
  698. r'\%s\Connection' % guid)
  699. try:
  700. # The PnpInstanceID points to a key inside Enum
  701. (pnp_id, ttype) = _winreg.QueryValueEx(
  702. connection_key, 'PnpInstanceID')
  703. if ttype != _winreg.REG_SZ:
  704. raise ValueError
  705. device_key = _winreg.OpenKey(
  706. lm, r'SYSTEM\CurrentControlSet\Enum\%s' % pnp_id)
  707. try:
  708. # Get ConfigFlags for this device
  709. (flags, ttype) = _winreg.QueryValueEx(
  710. device_key, 'ConfigFlags')
  711. if ttype != _winreg.REG_DWORD:
  712. raise ValueError
  713. # Based on experimentation, bit 0x1 indicates that the
  714. # device is disabled.
  715. return not flags & 0x1
  716. finally:
  717. device_key.Close()
  718. finally:
  719. connection_key.Close()
  720. except (EnvironmentError, ValueError):
  721. # Pre-vista, enabled interfaces seem to have a non-empty
  722. # NTEContextList; this was how dnspython detected enabled
  723. # nics before the code above was contributed. We've retained
  724. # the old method since we don't know if the code above works
  725. # on Windows 95/98/ME.
  726. try:
  727. (nte, ttype) = _winreg.QueryValueEx(interface_key,
  728. 'NTEContextList')
  729. return nte is not None
  730. except WindowsError: # pylint: disable=undefined-variable
  731. return False
  732. def _compute_timeout(self, start):
  733. now = time.time()
  734. duration = now - start
  735. if duration < 0:
  736. if duration < -1:
  737. # Time going backwards is bad. Just give up.
  738. raise Timeout(timeout=duration)
  739. else:
  740. # Time went backwards, but only a little. This can
  741. # happen, e.g. under vmware with older linux kernels.
  742. # Pretend it didn't happen.
  743. now = start
  744. if duration >= self.lifetime:
  745. raise Timeout(timeout=duration)
  746. return min(self.lifetime - duration, self.timeout)
  747. def query(self, qname, rdtype=dns.rdatatype.A, rdclass=dns.rdataclass.IN,
  748. tcp=False, source=None, raise_on_no_answer=True, source_port=0):
  749. """Query nameservers to find the answer to the question.
  750. The I{qname}, I{rdtype}, and I{rdclass} parameters may be objects
  751. of the appropriate type, or strings that can be converted into objects
  752. of the appropriate type. E.g. For I{rdtype} the integer 2 and the
  753. the string 'NS' both mean to query for records with DNS rdata type NS.
  754. @param qname: the query name
  755. @type qname: dns.name.Name object or string
  756. @param rdtype: the query type
  757. @type rdtype: int or string
  758. @param rdclass: the query class
  759. @type rdclass: int or string
  760. @param tcp: use TCP to make the query (default is False).
  761. @type tcp: bool
  762. @param source: bind to this IP address (defaults to machine default
  763. IP).
  764. @type source: IP address in dotted quad notation
  765. @param raise_on_no_answer: raise NoAnswer if there's no answer
  766. (defaults is True).
  767. @type raise_on_no_answer: bool
  768. @param source_port: The port from which to send the message.
  769. The default is 0.
  770. @type source_port: int
  771. @rtype: dns.resolver.Answer instance
  772. @raises Timeout: no answers could be found in the specified lifetime
  773. @raises NXDOMAIN: the query name does not exist
  774. @raises YXDOMAIN: the query name is too long after DNAME substitution
  775. @raises NoAnswer: the response did not contain an answer and
  776. raise_on_no_answer is True.
  777. @raises NoNameservers: no non-broken nameservers are available to
  778. answer the question."""
  779. if isinstance(qname, string_types):
  780. qname = dns.name.from_text(qname, None)
  781. if isinstance(rdtype, string_types):
  782. rdtype = dns.rdatatype.from_text(rdtype)
  783. if dns.rdatatype.is_metatype(rdtype):
  784. raise NoMetaqueries
  785. if isinstance(rdclass, string_types):
  786. rdclass = dns.rdataclass.from_text(rdclass)
  787. if dns.rdataclass.is_metaclass(rdclass):
  788. raise NoMetaqueries
  789. qnames_to_try = []
  790. if qname.is_absolute():
  791. qnames_to_try.append(qname)
  792. else:
  793. if len(qname) > 1:
  794. qnames_to_try.append(qname.concatenate(dns.name.root))
  795. if self.search:
  796. for suffix in self.search:
  797. qnames_to_try.append(qname.concatenate(suffix))
  798. else:
  799. qnames_to_try.append(qname.concatenate(self.domain))
  800. all_nxdomain = True
  801. nxdomain_responses = {}
  802. start = time.time()
  803. _qname = None # make pylint happy
  804. for _qname in qnames_to_try:
  805. if self.cache:
  806. answer = self.cache.get((_qname, rdtype, rdclass))
  807. if answer is not None:
  808. if answer.rrset is None and raise_on_no_answer:
  809. raise NoAnswer(response=answer.response)
  810. else:
  811. return answer
  812. request = dns.message.make_query(_qname, rdtype, rdclass)
  813. if self.keyname is not None:
  814. request.use_tsig(self.keyring, self.keyname,
  815. algorithm=self.keyalgorithm)
  816. request.use_edns(self.edns, self.ednsflags, self.payload)
  817. if self.flags is not None:
  818. request.flags = self.flags
  819. response = None
  820. #
  821. # make a copy of the servers list so we can alter it later.
  822. #
  823. nameservers = self.nameservers[:]
  824. errors = []
  825. if self.rotate:
  826. random.shuffle(nameservers)
  827. backoff = 0.10
  828. while response is None:
  829. if len(nameservers) == 0:
  830. raise NoNameservers(request=request, errors=errors)
  831. for nameserver in nameservers[:]:
  832. timeout = self._compute_timeout(start)
  833. port = self.nameserver_ports.get(nameserver, self.port)
  834. try:
  835. tcp_attempt = tcp
  836. if tcp:
  837. response = dns.query.tcp(request, nameserver,
  838. timeout, port,
  839. source=source,
  840. source_port=source_port)
  841. else:
  842. response = dns.query.udp(request, nameserver,
  843. timeout, port,
  844. source=source,
  845. source_port=source_port)
  846. if response.flags & dns.flags.TC:
  847. # Response truncated; retry with TCP.
  848. tcp_attempt = True
  849. timeout = self._compute_timeout(start)
  850. response = \
  851. dns.query.tcp(request, nameserver,
  852. timeout, port,
  853. source=source,
  854. source_port=source_port)
  855. except (socket.error, dns.exception.Timeout) as ex:
  856. #
  857. # Communication failure or timeout. Go to the
  858. # next server
  859. #
  860. errors.append((nameserver, tcp_attempt, port, ex,
  861. response))
  862. response = None
  863. continue
  864. except dns.query.UnexpectedSource as ex:
  865. #
  866. # Who knows? Keep going.
  867. #
  868. errors.append((nameserver, tcp_attempt, port, ex,
  869. response))
  870. response = None
  871. continue
  872. except dns.exception.FormError as ex:
  873. #
  874. # We don't understand what this server is
  875. # saying. Take it out of the mix and
  876. # continue.
  877. #
  878. nameservers.remove(nameserver)
  879. errors.append((nameserver, tcp_attempt, port, ex,
  880. response))
  881. response = None
  882. continue
  883. except EOFError as ex:
  884. #
  885. # We're using TCP and they hung up on us.
  886. # Probably they don't support TCP (though
  887. # they're supposed to!). Take it out of the
  888. # mix and continue.
  889. #
  890. nameservers.remove(nameserver)
  891. errors.append((nameserver, tcp_attempt, port, ex,
  892. response))
  893. response = None
  894. continue
  895. rcode = response.rcode()
  896. if rcode == dns.rcode.YXDOMAIN:
  897. ex = YXDOMAIN()
  898. errors.append((nameserver, tcp_attempt, port, ex,
  899. response))
  900. raise ex
  901. if rcode == dns.rcode.NOERROR or \
  902. rcode == dns.rcode.NXDOMAIN:
  903. break
  904. #
  905. # We got a response, but we're not happy with the
  906. # rcode in it. Remove the server from the mix if
  907. # the rcode isn't SERVFAIL.
  908. #
  909. if rcode != dns.rcode.SERVFAIL or not self.retry_servfail:
  910. nameservers.remove(nameserver)
  911. errors.append((nameserver, tcp_attempt, port,
  912. dns.rcode.to_text(rcode), response))
  913. response = None
  914. if response is not None:
  915. break
  916. #
  917. # All nameservers failed!
  918. #
  919. if len(nameservers) > 0:
  920. #
  921. # But we still have servers to try. Sleep a bit
  922. # so we don't pound them!
  923. #
  924. timeout = self._compute_timeout(start)
  925. sleep_time = min(timeout, backoff)
  926. backoff *= 2
  927. time.sleep(sleep_time)
  928. if response.rcode() == dns.rcode.NXDOMAIN:
  929. nxdomain_responses[_qname] = response
  930. continue
  931. all_nxdomain = False
  932. break
  933. if all_nxdomain:
  934. raise NXDOMAIN(qnames=qnames_to_try, responses=nxdomain_responses)
  935. answer = Answer(_qname, rdtype, rdclass, response,
  936. raise_on_no_answer)
  937. if self.cache:
  938. self.cache.put((_qname, rdtype, rdclass), answer)
  939. return answer
  940. def use_tsig(self, keyring, keyname=None,
  941. algorithm=dns.tsig.default_algorithm):
  942. """Add a TSIG signature to the query.
  943. @param keyring: The TSIG keyring to use; defaults to None.
  944. @type keyring: dict
  945. @param keyname: The name of the TSIG key to use; defaults to None.
  946. The key must be defined in the keyring. If a keyring is specified
  947. but a keyname is not, then the key used will be the first key in the
  948. keyring. Note that the order of keys in a dictionary is not defined,
  949. so applications should supply a keyname when a keyring is used, unless
  950. they know the keyring contains only one key.
  951. @param algorithm: The TSIG key algorithm to use. The default
  952. is dns.tsig.default_algorithm.
  953. @type algorithm: string"""
  954. self.keyring = keyring
  955. if keyname is None:
  956. self.keyname = list(self.keyring.keys())[0]
  957. else:
  958. self.keyname = keyname
  959. self.keyalgorithm = algorithm
  960. def use_edns(self, edns, ednsflags, payload):
  961. """Configure Edns.
  962. @param edns: The EDNS level to use. The default is -1, no Edns.
  963. @type edns: int
  964. @param ednsflags: The EDNS flags
  965. @type ednsflags: int
  966. @param payload: The EDNS payload size. The default is 0.
  967. @type payload: int"""
  968. if edns is None:
  969. edns = -1
  970. self.edns = edns
  971. self.ednsflags = ednsflags
  972. self.payload = payload
  973. def set_flags(self, flags):
  974. """Overrides the default flags with your own
  975. @param flags: The flags to overwrite the default with
  976. @type flags: int"""
  977. self.flags = flags
  978. default_resolver = None
  979. def get_default_resolver():
  980. """Get the default resolver, initializing it if necessary."""
  981. if default_resolver is None:
  982. reset_default_resolver()
  983. return default_resolver
  984. def reset_default_resolver():
  985. """Re-initialize default resolver.
  986. resolv.conf will be re-read immediatelly.
  987. """
  988. global default_resolver
  989. default_resolver = Resolver()
  990. def query(qname, rdtype=dns.rdatatype.A, rdclass=dns.rdataclass.IN,
  991. tcp=False, source=None, raise_on_no_answer=True,
  992. source_port=0):
  993. """Query nameservers to find the answer to the question.
  994. This is a convenience function that uses the default resolver
  995. object to make the query.
  996. @see: L{dns.resolver.Resolver.query} for more information on the
  997. parameters."""
  998. return get_default_resolver().query(qname, rdtype, rdclass, tcp, source,
  999. raise_on_no_answer, source_port)
  1000. def zone_for_name(name, rdclass=dns.rdataclass.IN, tcp=False, resolver=None):
  1001. """Find the name of the zone which contains the specified name.
  1002. @param name: the query name
  1003. @type name: absolute dns.name.Name object or string
  1004. @param rdclass: The query class
  1005. @type rdclass: int
  1006. @param tcp: use TCP to make the query (default is False).
  1007. @type tcp: bool
  1008. @param resolver: the resolver to use
  1009. @type resolver: dns.resolver.Resolver object or None
  1010. @rtype: dns.name.Name"""
  1011. if isinstance(name, string_types):
  1012. name = dns.name.from_text(name, dns.name.root)
  1013. if resolver is None:
  1014. resolver = get_default_resolver()
  1015. if not name.is_absolute():
  1016. raise NotAbsolute(name)
  1017. while 1:
  1018. try:
  1019. answer = resolver.query(name, dns.rdatatype.SOA, rdclass, tcp)
  1020. if answer.rrset.name == name:
  1021. return name
  1022. # otherwise we were CNAMEd or DNAMEd and need to look higher
  1023. except (dns.resolver.NXDOMAIN, dns.resolver.NoAnswer):
  1024. pass
  1025. try:
  1026. name = name.parent()
  1027. except dns.name.NoParent:
  1028. raise NoRootSOA
  1029. #
  1030. # Support for overriding the system resolver for all python code in the
  1031. # running process.
  1032. #
  1033. _protocols_for_socktype = {
  1034. socket.SOCK_DGRAM: [socket.SOL_UDP],
  1035. socket.SOCK_STREAM: [socket.SOL_TCP],
  1036. }
  1037. _resolver = None
  1038. _original_getaddrinfo = socket.getaddrinfo
  1039. _original_getnameinfo = socket.getnameinfo
  1040. _original_getfqdn = socket.getfqdn
  1041. _original_gethostbyname = socket.gethostbyname
  1042. _original_gethostbyname_ex = socket.gethostbyname_ex
  1043. _original_gethostbyaddr = socket.gethostbyaddr
  1044. def _getaddrinfo(host=None, service=None, family=socket.AF_UNSPEC, socktype=0,
  1045. proto=0, flags=0):
  1046. if flags & (socket.AI_ADDRCONFIG | socket.AI_V4MAPPED) != 0:
  1047. raise NotImplementedError
  1048. if host is None and service is None:
  1049. raise socket.gaierror(socket.EAI_NONAME)
  1050. v6addrs = []
  1051. v4addrs = []
  1052. canonical_name = None
  1053. try:
  1054. # Is host None or a V6 address literal?
  1055. if host is None:
  1056. canonical_name = 'localhost'
  1057. if flags & socket.AI_PASSIVE != 0:
  1058. v6addrs.append('::')
  1059. v4addrs.append('0.0.0.0')
  1060. else:
  1061. v6addrs.append('::1')
  1062. v4addrs.append('127.0.0.1')
  1063. else:
  1064. parts = host.split('%')
  1065. if len(parts) == 2:
  1066. ahost = parts[0]
  1067. else:
  1068. ahost = host
  1069. addr = dns.ipv6.inet_aton(ahost)
  1070. v6addrs.append(host)
  1071. canonical_name = host
  1072. except Exception:
  1073. try:
  1074. # Is it a V4 address literal?
  1075. addr = dns.ipv4.inet_aton(host)
  1076. v4addrs.append(host)
  1077. canonical_name = host
  1078. except Exception:
  1079. if flags & socket.AI_NUMERICHOST == 0:
  1080. try:
  1081. if family == socket.AF_INET6 or family == socket.AF_UNSPEC:
  1082. v6 = _resolver.query(host, dns.rdatatype.AAAA,
  1083. raise_on_no_answer=False)
  1084. # Note that setting host ensures we query the same name
  1085. # for A as we did for AAAA.
  1086. host = v6.qname
  1087. canonical_name = v6.canonical_name.to_text(True)
  1088. if v6.rrset is not None:
  1089. for rdata in v6.rrset:
  1090. v6addrs.append(rdata.address)
  1091. if family == socket.AF_INET or family == socket.AF_UNSPEC:
  1092. v4 = _resolver.query(host, dns.rdatatype.A,
  1093. raise_on_no_answer=False)
  1094. host = v4.qname
  1095. canonical_name = v4.canonical_name.to_text(True)
  1096. if v4.rrset is not None:
  1097. for rdata in v4.rrset:
  1098. v4addrs.append(rdata.address)
  1099. except dns.resolver.NXDOMAIN:
  1100. raise socket.gaierror(socket.EAI_NONAME)
  1101. except:
  1102. raise socket.gaierror(socket.EAI_SYSTEM)
  1103. port = None
  1104. try:
  1105. # Is it a port literal?
  1106. if service is None:
  1107. port = 0
  1108. else:
  1109. port = int(service)
  1110. except Exception:
  1111. if flags & socket.AI_NUMERICSERV == 0:
  1112. try:
  1113. port = socket.getservbyname(service)
  1114. except Exception:
  1115. pass
  1116. if port is None:
  1117. raise socket.gaierror(socket.EAI_NONAME)
  1118. tuples = []
  1119. if socktype == 0:
  1120. socktypes = [socket.SOCK_DGRAM, socket.SOCK_STREAM]
  1121. else:
  1122. socktypes = [socktype]
  1123. if flags & socket.AI_CANONNAME != 0:
  1124. cname = canonical_name
  1125. else:
  1126. cname = ''
  1127. if family == socket.AF_INET6 or family == socket.AF_UNSPEC:
  1128. for addr in v6addrs:
  1129. for socktype in socktypes:
  1130. for proto in _protocols_for_socktype[socktype]:
  1131. tuples.append((socket.AF_INET6, socktype, proto,
  1132. cname, (addr, port, 0, 0)))
  1133. if family == socket.AF_INET or family == socket.AF_UNSPEC:
  1134. for addr in v4addrs:
  1135. for socktype in socktypes:
  1136. for proto in _protocols_for_socktype[socktype]:
  1137. tuples.append((socket.AF_INET, socktype, proto,
  1138. cname, (addr, port)))
  1139. if len(tuples) == 0:
  1140. raise socket.gaierror(socket.EAI_NONAME)
  1141. return tuples
  1142. def _getnameinfo(sockaddr, flags=0):
  1143. host = sockaddr[0]
  1144. port = sockaddr[1]
  1145. if len(sockaddr) == 4:
  1146. scope = sockaddr[3]
  1147. family = socket.AF_INET6
  1148. else:
  1149. scope = None
  1150. family = socket.AF_INET
  1151. tuples = _getaddrinfo(host, port, family, socket.SOCK_STREAM,
  1152. socket.SOL_TCP, 0)
  1153. if len(tuples) > 1:
  1154. raise socket.error('sockaddr resolved to multiple addresses')
  1155. addr = tuples[0][4][0]
  1156. if flags & socket.NI_DGRAM:
  1157. pname = 'udp'
  1158. else:
  1159. pname = 'tcp'
  1160. qname = dns.reversename.from_address(addr)
  1161. if flags & socket.NI_NUMERICHOST == 0:
  1162. try:
  1163. answer = _resolver.query(qname, 'PTR')
  1164. hostname = answer.rrset[0].target.to_text(True)
  1165. except (dns.resolver.NXDOMAIN, dns.resolver.NoAnswer):
  1166. if flags & socket.NI_NAMEREQD:
  1167. raise socket.gaierror(socket.EAI_NONAME)
  1168. hostname = addr
  1169. if scope is not None:
  1170. hostname += '%' + str(scope)
  1171. else:
  1172. hostname = addr
  1173. if scope is not None:
  1174. hostname += '%' + str(scope)
  1175. if flags & socket.NI_NUMERICSERV:
  1176. service = str(port)
  1177. else:
  1178. service = socket.getservbyport(port, pname)
  1179. return (hostname, service)
  1180. def _getfqdn(name=None):
  1181. if name is None:
  1182. name = socket.gethostname()
  1183. try:
  1184. return _getnameinfo(_getaddrinfo(name, 80)[0][4])[0]
  1185. except Exception:
  1186. return name
  1187. def _gethostbyname(name):
  1188. return _gethostbyname_ex(name)[2][0]
  1189. def _gethostbyname_ex(name):
  1190. aliases = []
  1191. addresses = []
  1192. tuples = _getaddrinfo(name, 0, socket.AF_INET, socket.SOCK_STREAM,
  1193. socket.SOL_TCP, socket.AI_CANONNAME)
  1194. canonical = tuples[0][3]
  1195. for item in tuples:
  1196. addresses.append(item[4][0])
  1197. # XXX we just ignore aliases
  1198. return (canonical, aliases, addresses)
  1199. def _gethostbyaddr(ip):
  1200. try:
  1201. dns.ipv6.inet_aton(ip)
  1202. sockaddr = (ip, 80, 0, 0)
  1203. family = socket.AF_INET6
  1204. except Exception:
  1205. sockaddr = (ip, 80)
  1206. family = socket.AF_INET
  1207. (name, port) = _getnameinfo(sockaddr, socket.NI_NAMEREQD)
  1208. aliases = []
  1209. addresses = []
  1210. tuples = _getaddrinfo(name, 0, family, socket.SOCK_STREAM, socket.SOL_TCP,
  1211. socket.AI_CANONNAME)
  1212. canonical = tuples[0][3]
  1213. for item in tuples:
  1214. addresses.append(item[4][0])
  1215. # XXX we just ignore aliases
  1216. return (canonical, aliases, addresses)
  1217. def override_system_resolver(resolver=None):
  1218. """Override the system resolver routines in the socket module with
  1219. versions which use dnspython's resolver.
  1220. This can be useful in testing situations where you want to control
  1221. the resolution behavior of python code without having to change
  1222. the system's resolver settings (e.g. /etc/resolv.conf).
  1223. The resolver to use may be specified; if it's not, the default
  1224. resolver will be used.
  1225. @param resolver: the resolver to use
  1226. @type resolver: dns.resolver.Resolver object or None
  1227. """
  1228. if resolver is None:
  1229. resolver = get_default_resolver()
  1230. global _resolver
  1231. _resolver = resolver
  1232. socket.getaddrinfo = _getaddrinfo
  1233. socket.getnameinfo = _getnameinfo
  1234. socket.getfqdn = _getfqdn
  1235. socket.gethostbyname = _gethostbyname
  1236. socket.gethostbyname_ex = _gethostbyname_ex
  1237. socket.gethostbyaddr = _gethostbyaddr
  1238. def restore_system_resolver():
  1239. """Undo the effects of override_system_resolver().
  1240. """
  1241. global _resolver
  1242. _resolver = None
  1243. socket.getaddrinfo = _original_getaddrinfo
  1244. socket.getnameinfo = _original_getnameinfo
  1245. socket.getfqdn = _original_getfqdn
  1246. socket.gethostbyname = _original_gethostbyname
  1247. socket.gethostbyname_ex = _original_gethostbyname_ex
  1248. socket.gethostbyaddr = _original_gethostbyaddr