python/qmp: allow sockets to be passed to connect()

Allow existing sockets to be passed to connect(). The changes are pretty
minimal, and this allows for far greater flexibility in setting up
communications with an endpoint.

Signed-off-by: John Snow <jsnow@redhat.com>
Message-id: 20230517163406.2593480-2-jsnow@redhat.com
Signed-off-by: John Snow <jsnow@redhat.com>

python/qemu/qmp/protocol.py

@@ -370,7 +370,7 @@ async def accept(self) -> None:
 
     @upper_half
     @require(Runstate.IDLE)
-    async def connect(self, address: SocketAddrT,
+    async def connect(self, address: Union[SocketAddrT, socket.socket],
                       ssl: Optional[SSLContext] = None) -> None:
         """
         Connect to the server and begin processing message queues.
@@ -615,7 +615,7 @@ async def _do_accept(self) -> None:
         self.logger.debug("Connection accepted.")
 
     @upper_half
-    async def _do_connect(self, address: SocketAddrT,
+    async def _do_connect(self, address: Union[SocketAddrT, socket.socket],
                           ssl: Optional[SSLContext] = None) -> None:
         """
         Acting as the transport client, initiate a connection to a server.
@@ -634,9 +634,17 @@ async def _do_connect(self, address: SocketAddrT,
         # otherwise yield.
         await asyncio.sleep(0)
 
-        self.logger.debug("Connecting to %s ...", address)
-
-        if isinstance(address, tuple):
+        if isinstance(address, socket.socket):
+            self.logger.debug("Connecting with existing socket: "
+                              "fd=%d, family=%r, type=%r",
+                              address.fileno(), address.family, address.type)
+            connect = asyncio.open_connection(
+                limit=self._limit,
+                ssl=ssl,
+                sock=address,
+            )
+        elif isinstance(address, tuple):
+            self.logger.debug("Connecting to %s ...", address)
             connect = asyncio.open_connection(
                 address[0],
                 address[1],
@@ -644,13 +652,14 @@ async def _do_connect(self, address: SocketAddrT,
                 limit=self._limit,
             )
         else:
+            self.logger.debug("Connecting to file://%s ...", address)
             connect = asyncio.open_unix_connection(
                 path=address,
                 ssl=ssl,
                 limit=self._limit,
             )
-        self._reader, self._writer = await connect
 
+        self._reader, self._writer = await connect
         self.logger.debug("Connected.")
 
     @upper_half