From ad7d2c9f05a654443d63800aadc32c77810b843e Mon Sep 17 00:00:00 2001
From: Michael Kuron <m.kuron@gmx.de>
Date: Sun, 2 Aug 2020 17:31:50 +0200
Subject: [PATCH] rough draft

---
 README.md        |  4 +++
 proxy.py         | 68 ++++++++++++++++++++++++++++++++++++++++++++++++
 requirements.txt |  2 ++
 3 files changed, 74 insertions(+)
 create mode 100644 README.md
 create mode 100644 proxy.py
 create mode 100644 requirements.txt

diff --git a/README.md b/README.md
new file mode 100644
index 0000000..3441412
--- /dev/null
+++ b/README.md
@@ -0,0 +1,4 @@
+https://opensource.apple.com/source/mDNSResponder/mDNSResponder-1096.60.2/ServiceRegistration/dnssd-proxy.c.auto.html
+https://github.com/sbyx/ohybridproxy
+
+requires https://github.com/jstasiak/python-zeroconf
\ No newline at end of file
diff --git a/proxy.py b/proxy.py
new file mode 100644
index 0000000..082f682
--- /dev/null
+++ b/proxy.py
@@ -0,0 +1,68 @@
+#!/usr/bin/env python3
+
+from zeroconf import Zeroconf, ServiceBrowser, ServiceStateChange
+import sys
+import time
+from twisted.internet import reactor, defer
+from twisted.names import client, dns, error, server
+from twisted.python import log
+
+domain = sys.argv[1]
+port = int(sys.argv[2])
+
+class DynamicResolver(object):
+    def _dynamicResponseRequired(self, query):
+        if str(query.name).endswith(domain):
+            return True
+
+        return False
+
+    def _doDynamicResponse(self, query):
+        if query.type == dns.SOA:
+            return [], [], []
+        
+        localname = str(query.name)[:-len(domain)] + "local."
+        
+        services = []
+        def handler(zeroconf, service_type, name, state_change):
+            if state_change is ServiceStateChange.Added:
+                services.append(name)
+        
+        answers = []
+        if query.type == dns.PTR:
+            zeroconf = Zeroconf(ip_version=4)
+            sb = ServiceBrowser(zeroconf, localname, [handler])
+            time.sleep(2) # TODO: non-blocking
+            sb.cancel()
+            for service in services:
+                answers.append(dns.RRHeader(name=query.name.name, type=query.type, payload=dns.Record_PTR(
+                    name=service[:-6] + domain
+                )))
+        else:
+            # TODO: other types
+            print(query)
+        
+        return answers, [], []
+
+    def query(self, query, timeout=None):
+        if self._dynamicResponseRequired(query):
+            return defer.succeed(self._doDynamicResponse(query))
+        else:
+            return defer.fail(error.DomainError())
+
+def main():
+    factory = server.DNSServerFactory(
+        clients=[DynamicResolver()],
+        verbose=0
+    )
+
+    protocol = dns.DNSDatagramProtocol(controller=factory)
+
+    reactor.listenUDP(port, protocol)
+    reactor.listenTCP(port, factory)
+
+    log.startLogging(sys.stdout)
+    reactor.run()
+
+if __name__ == '__main__':
+    raise SystemExit(main())
diff --git a/requirements.txt b/requirements.txt
new file mode 100644
index 0000000..1817370
--- /dev/null
+++ b/requirements.txt
@@ -0,0 +1,2 @@
+zeroconf
+twisted
\ No newline at end of file