test: use dynamic port allocation to avoid test conflicts

Use port=0 for dynamic port allocation in test framework components
to avoid "address already in use" errors from concurrent tests or
ports stuck in TIME_WAIT state from previous test runs.

Changes:
- socks5.py: Update conf.addr after bind() to reflect actual port
- p2p.py: Retrieve actual port after create_server() when port=0
- feature_proxy.py: Use port=0 for all SOCKS5 proxy servers
- feature_anchors.py: Use port=0 for onion proxy server

test/functional/test_framework/p2p.py

@@ -787,13 +787,14 @@ class NetworkThread(threading.Thread):
                 cls.protos[(addr, port)] = None
             return response
 
-        if (addr, port) not in cls.listeners:
+        if port == 0 or (addr, port) not in cls.listeners:
             # When creating a listener on a given (addr, port) we only need to
             # do it once. If we want different behaviors for different
             # connections, we can accomplish this by providing different
             # `proto` functions
 
             listener = await cls.network_event_loop.create_server(peer_protocol, addr, port)
+            port = listener.sockets[0].getsockname()[1]
             logger.debug("Listening server on %s:%d should be started" % (addr, port))
             cls.listeners[(addr, port)] = listener
 

test/functional/test_framework/socks5.py

@@ -203,6 +203,9 @@ class Socks5Server():
         self.s = socket.socket(conf.af)
         self.s.setsockopt(socket.SOL_SOCKET, socket.SO_REUSEADDR, 1)
         self.s.bind(conf.addr)
+        # When port=0, the OS assigns an available port. Update conf.addr
+        # to reflect the actual bound address so callers can use it.
+        self.conf.addr = self.s.getsockname()
         self.s.listen(5)
         self.running = False
         self.thread = None