#!/usr/bin/python from twisted.internet import reactor from twisted.names import server from twisted.names import dns from twisted.names import common from twisted.internet import defer from twisted.python import failure import sipb_xen_database import psycopg2 import sqlalchemy import time class DatabaseAuthority(common.ResolverBase): """An Authority that is loaded from a file.""" soa = None def __init__(self, domains, database=None): common.ResolverBase.__init__(self) if database is not None: sipb_xen_database.connect(database) self.domains = domains self.soa = dns.Record_SOA(mname='sipb-xen-dev.mit.edu', rname='sipb-xen.mit.edu', serial=1, refresh=3600, retry=900, expire=3600000, minimum=21600, ttl=3600) self.ns = dns.Record_NS(name='ns1.xvm.mit.edu', ttl=3600) def _lookup(self, name, cls, type, timeout = None): for i in range(3): try: value = self._lookup_unsafe(name, cls, type, timeout = None) except (psycopg2.OperationalError, sqlalchemy.exceptions.SQLError): if i == 2: raise print "Reloading database" time.sleep(0.5) continue else: return value def _lookup_unsafe(self, name, cls, type, timeout): sipb_xen_database.clear_cache() ttl = 900 if name.lower() in self.domains: domain = name.lower() else: # This works because domain will remain bound after breaking out of the loop for domain in self.domains: if name.lower().endswith('.'+domain): break else: #Not us return defer.fail(failure.Failure(dns.DomainError(name))) results = [] authority = [] additional = [] authority.append(dns.RRHeader(domain, dns.NS, dns.IN, 3600, self.ns, auth=True)) if cls == dns.IN: if type in (dns.A, dns.ALL_RECORDS): host = name[:-len(domain)-1] if not host: record = dns.Record_CNAME('sipb-xen-dev.mit.edu', ttl) results.append(dns.RRHeader(name, dns.CNAME, dns.IN, ttl, record, auth=True)) else: value = sipb_xen_database.Machine.get_by(name=host) if value is None or not value.nics: return defer.fail(failure.Failure(dns.AuthoritativeDomainError(name))) ip = value.nics[0].ip if ip is None: #Deactivated? return defer.fail(failure.Failure(dns.AuthoritativeDomainError(name))) record = dns.Record_A(ip, ttl) results.append(dns.RRHeader(name, dns.A, dns.IN, ttl, record, auth=True)) elif type == dns.NS: results.append(dns.RRHeader(domain, dns.NS, dns.IN, ttl, self.ns, auth=True)) authority = [] record = dns.Record_A(address='18.181.0.62', ttl=ttl) additional.append(dns.RRHeader('ns1.xvm.mit.edu', dns.A, dns.IN, ttl, record, auth=True)) elif type == dns.SOA: results.append(dns.RRHeader(domain, dns.SOA, dns.IN, ttl, self.soa, auth=True)) return defer.succeed((results, authority, additional)) else: #Doesn't exist return defer.fail(failure.Failure(dns.AuthoritativeDomainError(name))) if '__main__' == __name__: resolver = DatabaseAuthority(['servers.csail.mit.edu', 'xvm.mit.edu'], 'postgres://sipb-xen@sipb-xen-dev/sipb_xen') verbosity = 0 f = server.DNSServerFactory(authorities=[resolver], verbose=verbosity) p = dns.DNSDatagramProtocol(f) f.noisy = p.noisy = verbosity reactor.listenUDP(53, p) reactor.listenTCP(53, f) reactor.run()