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proxy.py
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proxy.py
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#!/usr/bin/env python3
from zeroconf import Zeroconf, ServiceBrowser, ServiceStateChange, ServiceInfo, DNSQuestion, DNSOutgoing, RecordUpdateListener
from zeroconf.const import _TYPE_A, _CLASS_IN, _FLAGS_QR_QUERY
import sys
import time
from twisted.internet import reactor, defer, threads
from twisted.names import client, dns, error, server
from twisted.python import log
import socket
domain = sys.argv[1]
port = int(sys.argv[2])
ttl = 120
timeout = 2
class DynamicResolver(object):
def __init__(self):
self.zeroconf = Zeroconf(ip_version=4)
def _dynamicResponseRequired(self, query):
if str(query.name).endswith(domain):
return True
return False
def _doDynamicResponse(self, query):
if query.type == dns.SOA:
return defer.succeed(([], [], []))
localname = str(query.name)[:-len(domain)] + "local."
def browse(localname):
services = []
def handler(zeroconf, service_type, name, state_change):
if state_change is ServiceStateChange.Added:
services.append(name)
sb = ServiceBrowser(self.zeroconf, localname, [handler])
time.sleep(timeout)
sb.cancel()
answers, additional = [], []
for service in services:
answers.append(dns.RRHeader(name=localname[:-6] + domain, ttl=ttl, type=dns.PTR, payload=dns.Record_PTR(
name=service[:-6] + domain
)))
#txt_ans, _, _ = txt(service)
#srv_ans, _, a_ans = srv(service)
#additional += a_ans + txt_ans + srv_ans
return answers, [], additional
def txt(localname):
if localname.endswith('._device-info._tcp.local.'):
info = ServiceInfo(localname, localname)
info.request(self.zeroconf, timeout*1000)
if not info.text:
return [], [], []
else:
info = self.zeroconf.get_service_info(localname, localname, timeout*1000)
if info is None:
return [], [], []
order = []
i = 0
while i < len(info.text):
length = info.text[i]
i += 1
kv = info.text[i : i + length].split(b'=')
order.append(kv[0])
i += length
data = [b"%s=%s" % (p, info.properties[p]) for p in sorted(info.properties, key=lambda k: order.index(k) if k in order else 1000)]
answers = [dns.RRHeader(name=localname[:-6] + domain, ttl=ttl, type=dns.TXT, payload=dns.Record_TXT(
*data
))]
return answers, [], []
def srv(localname):
info = self.zeroconf.get_service_info(localname, localname, timeout*1000)
if info is None:
return [], [], []
answers = [dns.RRHeader(name=localname[:-6] + domain, ttl=ttl, type=dns.SRV, payload=dns.Record_SRV(
info.priority, info.weight, info.port, info.server[:-6] + domain
))]
additional = [dns.RRHeader(name=info.server[:-6] + domain, ttl=ttl, type=dns.A, payload=dns.Record_A(
socket.inet_ntop(socket.AF_INET, addr)
)) for addr in info.addresses]
return answers, [], additional
def host(localname):
class listener(RecordUpdateListener):
def __init__(self):
self.addrs = []
self.time = time.time()
def update_record(self, zc, now, record):
if record.type == _TYPE_A and len(record.address) == 4:
self.addrs.append(socket.inet_ntop(socket.AF_INET, record.address))
l = listener()
q = DNSQuestion(localname, _TYPE_A, _CLASS_IN)
self.zeroconf.add_listener(l, q)
out = DNSOutgoing(_FLAGS_QR_QUERY)
out.add_question(q)
self.zeroconf.send(out)
while len(l.addrs) == 0 and time.time() - l.time < timeout:
time.sleep(0.1)
self.zeroconf.remove_listener(l)
answers = [dns.RRHeader(name=query.name.name, ttl=ttl, type=dns.A, payload=dns.Record_A(
addr
)) for addr in l.addrs]
return answers, [], []
d = defer.Deferred()
if query.type == dns.PTR:
d = threads.deferToThread(browse, localname)
return d
elif query.type == dns.TXT:
d = threads.deferToThread(txt, localname)
return d
elif query.type == dns.SRV:
d = threads.deferToThread(srv, localname)
return d
elif query.type == dns.A:
d = threads.deferToThread(host, localname)
return d
elif query.type != dns.AAAA:
print("Unsupported request", query)
d.callback(([], [], []))
return d
def query(self, query, timeout=None):
if self._dynamicResponseRequired(query):
return self._doDynamicResponse(query)
else:
return defer.fail(error.DomainError())
class TruncatingDNSDatagramProtocol(dns.DNSDatagramProtocol):
def writeMessage(self, message, address):
if type(message) is dns.Message and len(message.toStr()) > 512:
message.additional = []
if len(message.toStr()) > 512:
message.trunc = 1
message.answers = []
dns.DNSDatagramProtocol.writeMessage(self, message, address)
def main():
factory = server.DNSServerFactory(
clients=[DynamicResolver()],
verbose=0
)
protocol = TruncatingDNSDatagramProtocol(controller=factory)
reactor.listenUDP(port, protocol)
reactor.listenTCP(port, factory)
log.startLogging(sys.stdout)
reactor.run()
if __name__ == '__main__':
raise SystemExit(main())