1 | #!/usr/bin/python |
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2 | from twisted.internet import reactor |
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3 | from twisted.names import server |
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4 | from twisted.names import dns |
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5 | from twisted.names import common |
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6 | from twisted.internet import defer |
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7 | from twisted.python import failure |
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8 | |
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9 | import sipb_xen_database |
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10 | import psycopg2 |
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11 | import sqlalchemy |
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12 | import time |
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13 | |
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14 | class DatabaseAuthority(common.ResolverBase): |
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15 | """An Authority that is loaded from a file.""" |
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16 | |
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17 | soa = None |
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18 | |
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19 | def __init__(self, domains, database=None): |
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20 | common.ResolverBase.__init__(self) |
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21 | if database is not None: |
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22 | sipb_xen_database.connect(database) |
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23 | self.domains = domains |
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24 | self.soa = dns.Record_SOA(mname='sipb-xen-dev.mit.edu', |
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25 | rname='sipb-xen.mit.edu', |
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26 | serial=1, refresh=3600, retry=900, |
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27 | expire=3600000, minimum=21600, ttl=3600) |
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28 | self.ns = dns.Record_NS(name='ns1.xvm.mit.edu', ttl=3600) |
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29 | record = dns.Record_A(address='18.181.0.62', ttl=3600) |
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30 | self.ns1 = dns.RRHeader('ns1.xvm.mit.edu', dns.A, dns.IN, |
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31 | 3600, record, auth=True) |
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32 | |
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33 | |
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34 | def _lookup(self, name, cls, type, timeout = None): |
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35 | for i in range(3): |
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36 | try: |
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37 | value = self._lookup_unsafe(name, cls, type, timeout = None) |
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38 | except (psycopg2.OperationalError, sqlalchemy.exceptions.SQLError): |
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39 | if i == 2: |
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40 | raise |
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41 | print "Reloading database" |
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42 | time.sleep(0.5) |
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43 | continue |
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44 | else: |
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45 | return value |
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46 | |
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47 | def _lookup_unsafe(self, name, cls, type, timeout): |
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48 | sipb_xen_database.clear_cache() |
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49 | |
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50 | ttl = 900 |
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51 | if name.lower() in self.domains: |
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52 | domain = name.lower() |
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53 | else: |
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54 | # This works because domain will remain bound after breaking out of the loop |
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55 | for domain in self.domains: |
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56 | if name.lower().endswith('.'+domain): |
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57 | break |
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58 | else: #Not us |
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59 | return defer.fail(failure.Failure(dns.DomainError(name))) |
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60 | results = [] |
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61 | authority = [] |
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62 | additional = [self.ns1] |
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63 | authority.append(dns.RRHeader(domain, dns.NS, dns.IN, |
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64 | 3600, self.ns, auth=True)) |
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65 | if cls == dns.IN: |
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66 | if type in (dns.A, dns.ALL_RECORDS): |
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67 | host = name[:-len(domain)-1] |
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68 | if not host: |
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69 | record = dns.Record_A('18.181.0.62', ttl) |
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70 | results.append(dns.RRHeader(name, dns.A, dns.IN, |
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71 | ttl, record, auth=True)) |
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72 | else: |
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73 | value = sipb_xen_database.Machine.get_by(name=host) |
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74 | if value is None or not value.nics: |
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75 | return defer.fail(failure.Failure(dns.AuthoritativeDomainError(name))) |
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76 | ip = value.nics[0].ip |
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77 | if ip is None: #Deactivated? |
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78 | return defer.fail(failure.Failure(dns.AuthoritativeDomainError(name))) |
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79 | record = dns.Record_A(ip, ttl) |
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80 | results.append(dns.RRHeader(name, dns.A, dns.IN, |
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81 | ttl, record, auth=True)) |
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82 | elif type == dns.NS: |
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83 | results.append(dns.RRHeader(domain, dns.NS, dns.IN, |
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84 | ttl, self.ns, auth=True)) |
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85 | authority = [] |
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86 | elif type == dns.SOA: |
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87 | results.append(dns.RRHeader(domain, dns.SOA, dns.IN, |
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88 | ttl, self.soa, auth=True)) |
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89 | return defer.succeed((results, authority, additional)) |
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90 | else: |
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91 | #Doesn't exist |
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92 | return defer.fail(failure.Failure(dns.AuthoritativeDomainError(name))) |
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93 | |
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94 | if '__main__' == __name__: |
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95 | resolver = DatabaseAuthority(['servers.csail.mit.edu', |
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96 | 'xvm.mit.edu'], |
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97 | 'postgres://sipb-xen@sipb-xen-dev/sipb_xen') |
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98 | |
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99 | verbosity = 0 |
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100 | f = server.DNSServerFactory(authorities=[resolver], verbose=verbosity) |
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101 | p = dns.DNSDatagramProtocol(f) |
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102 | f.noisy = p.noisy = verbosity |
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103 | |
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104 | reactor.listenUDP(53, p) |
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105 | reactor.listenTCP(53, f) |
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106 | reactor.run() |
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