[3.13] gh-119461: Fix ThreadedVSOCKSocketStreamTest (#119465) (#119479)

gh-119461: Fix ThreadedVSOCKSocketStreamTest (#119465)

Fix ThreadedVSOCKSocketStreamTest: if get_cid() returns the host
address or the "any" address, use the local communication address
(loopback): VMADDR_CID_LOCAL.

On Linux 6.9, apparently, the /dev/vsock device is now available but
get_cid() returns VMADDR_CID_ANY (-1).

(cherry picked from commit e94dbe4)

Lib/test/test_socket.py

@@ -47,6 +47,7 @@
 # test unicode string and carriage return
 MSG = 'Michael Gilfix was here\u1234\r\n'.encode('utf-8')
 
+VMADDR_CID_LOCAL = 1
 VSOCKPORT = 1234
 AIX = platform.system() == "AIX"
 WSL = "microsoft-standard-WSL" in platform.release()
@@ -160,8 +161,8 @@ def _have_socket_qipcrtr():
 
 def _have_socket_vsock():
     """Check whether AF_VSOCK sockets are supported on this host."""
-    ret = get_cid() is not None
-    return ret
+    cid = get_cid()
+    return (cid is not None)
 
 
 def _have_socket_bluetooth():
@@ -520,8 +521,6 @@ def clientTearDown(self):
 @unittest.skipIf(WSL, 'VSOCK does not work on Microsoft WSL')
 @unittest.skipUnless(HAVE_SOCKET_VSOCK,
           'VSOCK sockets required for this test.')
-@unittest.skipUnless(get_cid() != 2,
-          "This test can only be run on a virtual guest.")
 class ThreadedVSOCKSocketStreamTest(unittest.TestCase, ThreadableTest):
 
     def __init__(self, methodName='runTest'):
@@ -543,6 +542,9 @@ def clientSetUp(self):
         self.cli = socket.socket(socket.AF_VSOCK, socket.SOCK_STREAM)
         self.addCleanup(self.cli.close)
         cid = get_cid()
+        if cid in (socket.VMADDR_CID_HOST, socket.VMADDR_CID_ANY):
+            # gh-119461: Use the local communication address (loopback)
+            cid = VMADDR_CID_LOCAL
         self.cli.connect((cid, VSOCKPORT))
 
     def testStream(self):