#!/usr/bin/env python # -*- coding: utf-8 -*- # Copyright (c) 2014 clowwindy # # Permission is hereby granted, free of charge, to any person obtaining a copy # of this software and associated documentation files (the "Software"), to deal # in the Software without restriction, including without limitation the rights # to use, copy, modify, merge, publish, distribute, sublicense, and/or sell # copies of the Software, and to permit persons to whom the Software is # furnished to do so, subject to the following conditions: # # The above copyright notice and this permission notice shall be included in # all copies or substantial portions of the Software. # # THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR # IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, # FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE # AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER # LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, # OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE # SOFTWARE. import time import os import socket import struct import logging import common import lru_cache import eventloop CACHE_SWEEP_INTERVAL = 30 common.patch_socket() # rfc1035 # format # +---------------------+ # | Header | # +---------------------+ # | Question | the question for the name server # +---------------------+ # | Answer | RRs answering the question # +---------------------+ # | Authority | RRs pointing toward an authority # +---------------------+ # | Additional | RRs holding additional information # +---------------------+ # # header # 1 1 1 1 1 1 # 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 # +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+ # | ID | # +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+ # |QR| Opcode |AA|TC|RD|RA| Z | RCODE | # +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+ # | QDCOUNT | # +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+ # | ANCOUNT | # +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+ # | NSCOUNT | # +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+ # | ARCOUNT | # +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+ QTYPE_ANY = 255 QTYPE_A = 1 QTYPE_AAAA = 28 QTYPE_CNAME = 5 QCLASS_IN = 1 def build_address(address): address = address.strip('.') labels = address.split('.') results = [] for label in labels: l = len(label) if l > 63: return None results.append(chr(l)) results.append(label) results.append('\0') return ''.join(results) def build_request(address, qtype, request_id): header = struct.pack('!HBBHHHH', request_id, 1, 0, 1, 0, 0, 0) addr = build_address(address) qtype_qclass = struct.pack('!HH', qtype, QCLASS_IN) return header + addr + qtype_qclass def parse_ip(addrtype, data, length, offset): if addrtype == QTYPE_A: return socket.inet_ntop(socket.AF_INET, data[offset:offset + length]) elif addrtype == QTYPE_AAAA: return socket.inet_ntop(socket.AF_INET6, data[offset:offset + length]) elif addrtype == QTYPE_CNAME: return parse_name(data, offset)[1] else: return data def parse_name(data, offset): p = offset labels = [] l = ord(data[p]) while l > 0: if (l & (128 + 64)) == (128 + 64): # pointer pointer = struct.unpack('!H', data[p:p + 2])[0] pointer &= 0x3FFF r = parse_name(data, pointer) labels.append(r[1]) p += 2 # pointer is the end return p - offset, '.'.join(labels) else: labels.append(data[p + 1:p + 1 + l]) p += 1 + l l = ord(data[p]) return p - offset + 1, '.'.join(labels) # rfc1035 # record # 1 1 1 1 1 1 # 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 # +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+ # | | # / / # / NAME / # | | # +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+ # | TYPE | # +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+ # | CLASS | # +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+ # | TTL | # | | # +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+ # | RDLENGTH | # +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--| # / RDATA / # / / # +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+ def parse_record(data, offset, question=False): nlen, name = parse_name(data, offset) if not question: record_type, record_class, record_ttl, record_rdlength = struct.unpack( '!HHiH', data[offset + nlen:offset + nlen + 10] ) ip = parse_ip(record_type, data, record_rdlength, offset + nlen + 10) return nlen + 10 + record_rdlength, \ (name, ip, record_type, record_class, record_ttl) else: record_type, record_class = struct.unpack( '!HH', data[offset + nlen:offset + nlen + 4] ) return nlen + 4, (name, None, record_type, record_class, None, None) def parse_response(data): try: if len(data) >= 12: header = struct.unpack('!HBBHHHH', data[:12]) # res_id = header[0] # res_qr = header[1] & 128 res_tc = header[1] & 2 # res_ra = header[2] & 128 res_rcode = header[2] & 15 # assert res_tc == 0 # assert res_rcode in [0, 3] res_qdcount = header[3] res_ancount = header[4] res_nscount = header[5] res_arcount = header[6] qds = [] ans = [] offset = 12 for i in xrange(0, res_qdcount): l, r = parse_record(data, offset, True) offset += l if r: qds.append(r) for i in xrange(0, res_ancount): l, r = parse_record(data, offset) offset += l if r: ans.append(r) for i in xrange(0, res_nscount): l, r = parse_record(data, offset) offset += l for i in xrange(0, res_arcount): l, r = parse_record(data, offset) offset += l response = DNSResponse() if qds: response.hostname = qds[0][0] for an in ans: response.answers.append((an[1], an[2], an[3])) return response except Exception as e: import traceback traceback.print_exc() logging.error(e) return None def is_ip(address): for family in (socket.AF_INET, socket.AF_INET6): try: socket.inet_pton(family, address) return True except (OSError, IOError): pass return False class DNSResponse(object): def __init__(self): self.hostname = None self.answers = [] # each: (addr, type, class) def __str__(self): return '%s: %s' % (self.hostname, str(self.answers)) STATUS_IPV4 = 0 STATUS_IPV6 = 1 class DNSResolver(object): def __init__(self): self._loop = None self._request_id = 1 self._hosts = {} self._hostname_status = {} self._hostname_to_cb = {} self._cb_to_hostname = {} self._cache = lru_cache.LRUCache(timeout=300) self._last_time = time.time() self._sock = None self._parse_resolv() self._parse_hosts() # TODO monitor hosts change and reload hosts # TODO parse /etc/gai.conf and follow its rules def _parse_resolv(self): try: with open('/etc/resolv.conf', 'rb') as f: servers = [] content = f.readlines() for line in content: line = line.strip() if line: if line.startswith('nameserver'): parts = line.split() if len(parts) >= 2: server = parts[1] if is_ip(server): servers.append(server) # TODO support more servers if servers: self._dns_server = (servers[0], 53) return except IOError: pass self._dns_server = ('8.8.8.8', 53) def _parse_hosts(self): etc_path = '/etc/hosts' if os.environ.__contains__('WINDIR'): etc_path = os.environ['WINDIR'] + '/system32/drivers/etc/hosts' try: with open(etc_path, 'rb') as f: for line in f.readlines(): line = line.strip() parts = line.split() if len(parts) >= 2: ip = parts[0] if is_ip(ip): for i in xrange(1, len(parts)): hostname = parts[i] if hostname: self._hosts[hostname] = ip except IOError: self._hosts['localhost'] = '127.0.0.1' def add_to_loop(self, loop): if self._loop: raise Exception('already add to loop') self._loop = loop # TODO when dns server is IPv6 self._sock = socket.socket(socket.AF_INET, socket.SOCK_DGRAM, socket.SOL_UDP) self._sock.setblocking(False) loop.add(self._sock, eventloop.POLL_IN) loop.add_handler(self.handle_events) def _call_callback(self, hostname, ip): callbacks = self._hostname_to_cb.get(hostname, []) for callback in callbacks: if self._cb_to_hostname.__contains__(callback): del self._cb_to_hostname[callback] if ip: callback((hostname, ip), None) else: callback((hostname, None), Exception('unknown hostname %s' % hostname)) if self._hostname_to_cb.__contains__(hostname): del self._hostname_to_cb[hostname] if self._hostname_status.__contains__(hostname): del self._hostname_status[hostname] def _handle_data(self, data): response = parse_response(data) if response and response.hostname: hostname = response.hostname ip = None for answer in response.answers: if answer[1] in (QTYPE_A, QTYPE_AAAA) and \ answer[2] == QCLASS_IN: ip = answer[0] break if not ip and self._hostname_status.get(hostname, STATUS_IPV6) \ == STATUS_IPV4: self._hostname_status[hostname] = STATUS_IPV6 self._send_req(hostname, QTYPE_AAAA) else: if ip: self._cache[hostname] = ip self._call_callback(hostname, ip) def handle_events(self, events): for sock, fd, event in events: if sock != self._sock: continue if event & eventloop.POLL_ERR: logging.error('dns socket err') self._loop.remove(self._sock) self._sock.close() # TODO when dns server is IPv6 self._sock = socket.socket(socket.AF_INET, socket.SOCK_DGRAM, socket.SOL_UDP) self._sock.setblocking(False) self._loop.add(self._sock, eventloop.POLL_IN) else: data, addr = sock.recvfrom(1024) if addr != self._dns_server: logging.warn('received a packet other than our dns') break self._handle_data(data) break now = time.time() if now - self._last_time > CACHE_SWEEP_INTERVAL: self._cache.sweep() self._last_time = now def remove_callback(self, callback): hostname = self._cb_to_hostname.get(callback) if hostname: del self._cb_to_hostname[callback] arr = self._hostname_to_cb.get(hostname, None) if arr: arr.remove(callback) if not arr: del self._hostname_to_cb[hostname] if self._hostname_status.__contains__(hostname): del self._hostname_status[hostname] def _send_req(self, hostname, qtype): logging.debug('resolving %s with type %d using server %s', hostname, qtype, self._dns_server) self._request_id += 1 if self._request_id > 32768: self._request_id = 1 req = build_request(hostname, qtype, self._request_id) self._sock.sendto(req, self._dns_server) def resolve(self, hostname, callback): if not hostname: callback(None, Exception('empty hostname')) elif is_ip(hostname): callback((hostname, hostname), None) elif self._hosts.__contains__(hostname): logging.debug('hit hosts: %s', hostname) ip = self._hosts[hostname] callback((hostname, ip), None) elif self._cache.__contains__(hostname): logging.debug('hit cache: %s', hostname) ip = self._cache[hostname] callback((hostname, ip), None) else: arr = self._hostname_to_cb.get(hostname, None) if not arr: self._hostname_status[hostname] = STATUS_IPV4 self._send_req(hostname, QTYPE_A) self._hostname_to_cb[hostname] = [callback] self._cb_to_hostname[callback] = hostname else: arr.append(callback) def close(self): self._sock.close() def test(): logging.getLogger('').handlers = [] logging.basicConfig(level=logging.DEBUG, format='%(asctime)s %(levelname)-8s %(message)s', datefmt='%Y-%m-%d %H:%M:%S', filemode='a+') def _callback(address, error): print error, address loop = eventloop.EventLoop() resolver = DNSResolver() resolver.add_to_loop(loop) for hostname in ['www.google.com', '8.8.8.8', 'localhost', 'activate.adobe.com', 'www.twitter.com', 'ipv6.google.com', 'ipv6.l.google.com', 'www.gmail.com', 'r4---sn-3qqp-ioql.googlevideo.com', 'www.baidu.com', 'www.a.shifen.com', 'm.baidu.jp', 'www.youku.com', 'www.twitter.com', 'ipv6.google.com']: resolver.resolve(hostname, _callback) loop.run() if __name__ == '__main__': test()