2 files changed, 41 insertions, 3 deletions
diff --git a/python/qemu/aqmp/legacy.py b/python/qemu/aqmp/legacy.py
index 0890f95b16..6baa5f3409 100644
--- a/python/qemu/aqmp/legacy.py
+++ b/python/qemu/aqmp/legacy.py
@@ -56,6 +56,9 @@ class QEMUMonitorProtocol(qemu.qmp.QEMUMonitorProtocol):
         self._address = address
         self._timeout: Optional[float] = None
 
+        if server:
+            self._aqmp._bind_hack(address)  # pylint: disable=protected-access
+
     _T = TypeVar('_T')
 
     def _sync(
diff --git a/python/qemu/aqmp/protocol.py b/python/qemu/aqmp/protocol.py
index 50e973c2f2..33358f5cd7 100644
--- a/python/qemu/aqmp/protocol.py
+++ b/python/qemu/aqmp/protocol.py
@@ -15,6 +15,7 @@ from asyncio import StreamReader, StreamWriter
 from enum import Enum
 from functools import wraps
 import logging
+import socket
 from ssl import SSLContext
 from typing import (
     Any,
@@ -238,6 +239,9 @@ class AsyncProtocol(Generic[T]):
         self._runstate = Runstate.IDLE
         self._runstate_changed: Optional[asyncio.Event] = None
 
+        # Workaround for bind()
+        self._sock: Optional[socket.socket] = None
+
     def __repr__(self) -> str:
         cls_name = type(self).__name__
         tokens = []
@@ -427,6 +431,34 @@ class AsyncProtocol(Generic[T]):
         else:
             await self._do_connect(address, ssl)
 
+    def _bind_hack(self, address: Union[str, Tuple[str, int]]) -> None:
+        """
+        Used to create a socket in advance of accept().
+
+        This is a workaround to ensure that we can guarantee timing of
+        precisely when a socket exists to avoid a connection attempt
+        bouncing off of nothing.
+
+        Python 3.7+ adds a feature to separate the server creation and
+        listening phases instead, and should be used instead of this
+        hack.
+        """
+        if isinstance(address, tuple):
+            family = socket.AF_INET
+        else:
+            family = socket.AF_UNIX
+
+        sock = socket.socket(family, socket.SOCK_STREAM)
+        sock.setsockopt(socket.SOL_SOCKET, socket.SO_REUSEADDR, 1)
+
+        try:
+            sock.bind(address)
+        except:
+            sock.close()
+            raise
+
+        self._sock = sock
+
     @upper_half
     async def _do_accept(self, address: SocketAddrT,
                          ssl: Optional[SSLContext] = None) -> None:
@@ -464,24 +496,27 @@ class AsyncProtocol(Generic[T]):
         if isinstance(address, tuple):
             coro = asyncio.start_server(
                 _client_connected_cb,
-                host=address[0],
-                port=address[1],
+                host=None if self._sock else address[0],
+                port=None if self._sock else address[1],
                 ssl=ssl,
                 backlog=1,
                 limit=self._limit,
+                sock=self._sock,
             )
         else:
             coro = asyncio.start_unix_server(
                 _client_connected_cb,
-                path=address,
+                path=None if self._sock else address,
                 ssl=ssl,
                 backlog=1,
                 limit=self._limit,
+                sock=self._sock,
             )
 
         server = await coro     # Starts listening
         await connected.wait()  # Waits for the callback to fire (and finish)
         assert server is None
+        self._sock = None
 
         self.logger.debug("Connection accepted.")