add unix socket support (#127)

Config option LISTEN_UNIX_SOCK = "/path/to/socket.file" allows to listen
on specified unix socket in additional to (or instead of) configured ip
addresses. Listening on a socket can be useful for connection from local
reverse proxy w/o wasting tcp ports and network subsystem resources just
for inter-process communication.
Default value is empty - socket not used.

mtprotoproxy.py

@@ -16,6 +16,7 @@ import sys
 import re
 import runpy
 import signal
+import os
 
 
 TG_DATACENTER_PORT = 443
@@ -194,6 +195,9 @@ def init_config():
     # listen address for IPv6
     conf_dict.setdefault("LISTEN_ADDR_IPV6", "::")
 
+    # listen unix socket
+    conf_dict.setdefault("LISTEN_UNIX_SOCK", "")
+
     # allow access to config by attributes
     config = type("config", (dict,), conf_dict)(conf_dict)
 
@@ -1745,6 +1749,15 @@ def try_setup_uvloop():
         pass
 
 
+def remove_unix_socket(path):
+    from stat import S_ISSOCK
+    try:
+        if S_ISSOCK(os.stat(path).st_mode):
+            os.unlink(path)
+    except (FileNotFoundError, NotADirectoryError):
+        pass
+
+
 def loop_exception_handler(loop, context):
     exception = context.get("exception")
     transport = context.get("transport")
@@ -1802,16 +1815,25 @@ def main():
     asyncio.ensure_future(get_cert_len_task)
 
     reuse_port = hasattr(socket, "SO_REUSEPORT")
+    has_unix = hasattr(socket, "AF_UNIX")
+    servers = []
 
     if config.LISTEN_ADDR_IPV4:
-        task_v4 = asyncio.start_server(handle_client_wrapper, config.LISTEN_ADDR_IPV4, config.PORT,
+        task = asyncio.start_server(handle_client_wrapper, config.LISTEN_ADDR_IPV4, config.PORT,
-                                       limit=get_to_tg_bufsize(), reuse_port=reuse_port, loop=loop)
+                                    limit=get_to_tg_bufsize(), reuse_port=reuse_port, loop=loop)
-        server_v4 = loop.run_until_complete(task_v4)
+        servers.append(loop.run_until_complete(task))
 
     if config.LISTEN_ADDR_IPV6 and socket.has_ipv6:
-        task_v6 = asyncio.start_server(handle_client_wrapper, config.LISTEN_ADDR_IPV6, config.PORT,
+        task = asyncio.start_server(handle_client_wrapper, config.LISTEN_ADDR_IPV6, config.PORT,
-                                       limit=get_to_tg_bufsize(), reuse_port=reuse_port, loop=loop)
+                                    limit=get_to_tg_bufsize(), reuse_port=reuse_port, loop=loop)
-        server_v6 = loop.run_until_complete(task_v6)
+        servers.append(loop.run_until_complete(task))
+
+    if config.LISTEN_UNIX_SOCK and has_unix:
+        remove_unix_socket(config.LISTEN_UNIX_SOCK)
+        task = asyncio.start_unix_server(handle_client_wrapper, config.LISTEN_UNIX_SOCK,
+                                         limit=get_to_tg_bufsize(), loop=loop)
+        servers.append(loop.run_until_complete(task))
+        os.chmod(config.LISTEN_UNIX_SOCK, 0o666)
 
     try:
         loop.run_forever()
@@ -1821,13 +1843,12 @@ def main():
     for task in asyncio.Task.all_tasks():
         task.cancel()
 
-    if config.LISTEN_ADDR_IPV4:
+    for server in servers:
-        server_v4.close()
+        server.close()
-        loop.run_until_complete(server_v4.wait_closed())
+        loop.run_until_complete(server.wait_closed())
 
-    if config.LISTEN_ADDR_IPV6 and socket.has_ipv6:
+    if config.LISTEN_UNIX_SOCK and has_unix:
-        server_v6.close()
+        remove_unix_socket(config.LISTEN_UNIX_SOCK)
-        loop.run_until_complete(server_v6.wait_closed())
 
     loop.close()