Introduce independent_listener, will be used for both IPv4 and IPv6

connections.

client.py

@@ -95,6 +95,35 @@ def original_dst(sock):
         raise
 
 
+class MultiListener:
+
+    def __init__(self, type=socket.SOCK_STREAM, proto=0):
+        self.v4 = socket.socket(socket.AF_INET, type, proto)
+
+    def setsockopt(self, level, optname, value):
+        if self.v4:
+            self.v4.setsockopt(level, optname, value)
+
+    def add_handler(self, handlers, callback, mux):
+        if self.v4:
+            handlers.append(Handler([self.v4], lambda: callback(self.v4, mux, handlers)))
+
+    def listen(self, backlog):
+        if self.v4:
+            self.v4.listen(backlog)
+
+    def bind(self, address_v4):
+        if address_v4 and self.v4:
+            self.v4.bind(address_v4)
+        else:
+            self.v4 = None
+
+    def print_listening(self, what):
+        if self.v4:
+            listenip = self.v4.getsockname()
+            debug1('%s listening on %r.\n' % (what, listenip))
+
+
 class FirewallClient:
     def __init__(self, port, subnets_include, subnets_exclude, dnsport):
         self.port = port
@@ -322,10 +351,10 @@ def _main(tcp_listener, fw, ssh_cmd, remotename, python, latency_control,
                 fw.sethostip(name, ip)
     mux.got_host_list = onhostlist
 
-    handlers.append(Handler([tcp_listener], lambda: onaccept_tcp(tcp_listener, mux, handlers)))
+    tcp_listener.add_handler(handlers, onaccept_tcp, mux)
 
     if dns_listener:
-        handlers.append(Handler([dns_listener], lambda: ondns(dns_listener, mux, handlers)))
+        dns_listener.add_handler(handlers, ondns, mux)
 
     if seed_hosts != None:
         debug1('seed_hosts: %r\n' % seed_hosts)
@@ -364,9 +393,9 @@ def main(listenip, ssh_cmd, remotename, python, latency_control, dns,
     debug2('Binding:')
     for port in ports:
         debug2(' %d' % port)
-        tcp_listener = socket.socket()
+        tcp_listener = MultiListener()
         tcp_listener.setsockopt(socket.SOL_SOCKET, socket.SO_REUSEADDR, 1)
-        dns_listener = socket.socket(socket.AF_INET, socket.SOCK_DGRAM)
+        dns_listener = MultiListener(socket.SOCK_DGRAM)
         dns_listener.setsockopt(socket.SOL_SOCKET, socket.SO_REUSEADDR, 1)
         try:
             tcp_listener.bind((listenip[0], port))
@@ -380,11 +409,11 @@ def main(listenip, ssh_cmd, remotename, python, latency_control, dns,
         assert(last_e)
         raise last_e
     tcp_listener.listen(10)
-    listenip = tcp_listener.getsockname()
+    listenip = tcp_listener.v4.getsockname()
     debug1('Listening on %r.\n' % (listenip,))
 
     if dns:
-        dnsip = dns_listener.getsockname()
+        dnsip = dns_listener.v4.getsockname()
         debug1('DNS listening on %r.\n' % (dnsip,))
         dnsport = dnsip[1]
     else: