| 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 | def _lookup(self, name, cls, type, timeout = None): |
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| 29 | for i in range(3): |
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| 30 | try: |
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| 31 | value = self._lookup_unsafe(name, cls, type, timeout = None) |
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| 32 | except (psycopg2.OperationalError, sqlalchemy.exceptions.SQLError): |
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| 33 | if i == 2: |
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| 34 | raise |
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| 35 | print "Reloading database" |
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| 36 | time.sleep(0.5) |
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| 37 | continue |
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| 38 | else: |
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| 39 | return value |
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| 40 | |
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| 41 | def _lookup_unsafe(self, name, cls, type, timeout): |
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| 42 | sipb_xen_database.clear_cache() |
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| 43 | if name.lower() in self.domains: |
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| 44 | domain = name.lower() |
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| 45 | else: |
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| 46 | for domain in self.domains: |
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| 47 | if name.lower().endswith('.'+domain): |
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| 48 | break |
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| 49 | else: #Not us |
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| 50 | return defer.fail(failure.Failure(dns.DomainError(name))) |
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| 51 | results = [] |
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| 52 | if cls == dns.IN and type in (dns.A, dns.ALL_RECORDS): |
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| 53 | host = name[:-len(domain)-1] |
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| 54 | if not host: |
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| 55 | ttl = 900 |
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| 56 | record = dns.Record_CNAME('sipb-xen-dev.mit.edu', ttl) |
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| 57 | results.append(dns.RRHeader(name, dns.CNAME, dns.IN, |
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| 58 | ttl, record, auth=True)) |
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| 59 | else: |
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| 60 | value = sipb_xen_database.Machine.get_by(name=host) |
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| 61 | if value is None or not value.nics: |
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| 62 | return defer.fail(failure.Failure(dns.AuthoritativeDomainError(name))) |
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| 63 | ip = value.nics[0].ip |
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| 64 | if ip is None: #Deactivated? |
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| 65 | return defer.fail(failure.Failure(dns.AuthoritativeDomainError(name))) |
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| 66 | ttl = 900 |
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| 67 | record = dns.Record_A(ip, ttl) |
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| 68 | results.append(dns.RRHeader(name, dns.A, dns.IN, |
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| 69 | ttl, record, auth=True)) |
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| 70 | authority = [] |
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| 71 | auth_record = dns.Record_NS(name='ns1.xvm.mit.edu', ttl=3600) |
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| 72 | authority.append(dns.RRHeader(domain, dns.NS, dns.IN, |
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| 73 | 3600, auth_record, auth=True)) |
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| 74 | return defer.succeed((results, authority, [])) |
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| 75 | #Doesn't exist |
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| 76 | return defer.fail(failure.Failure(dns.AuthoritativeDomainError(name))) |
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| 77 | |
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| 78 | if '__main__' == __name__: |
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| 79 | resolver = DatabaseAuthority(['servers.csail.mit.edu', |
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| 80 | 'xvm.mit.edu'], |
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| 81 | 'postgres://sipb-xen@sipb-xen-dev/sipb_xen') |
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| 82 | |
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| 83 | verbosity = 0 |
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| 84 | f = server.DNSServerFactory(authorities=[resolver], verbose=verbosity) |
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| 85 | p = dns.DNSDatagramProtocol(f) |
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| 86 | f.noisy = p.noisy = verbosity |
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| 87 | |
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| 88 | reactor.listenUDP(53, p) |
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| 89 | reactor.listenTCP(53, f) |
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| 90 | reactor.run() |
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