[PATCH v2 2/3] Updates send_fd_scm function

[Oksana Vohchana <ovoshcha@redhat.com>]

A qemu-iotest uses for FD-migration test a helper program "socket_scm_helper".
And it makes some problems if you didn't build it with a QEMU. And now we can
use new methods for the socket that allow us to send a file/socket descriptor
(with access and permissions) from one process to another.

Signed-off-by: Oksana Vohchana <ovoshcha@redhat.com>
---
 python/qemu/machine.py | 64 ++++++++++++++++++++++++++----------------
 1 file changed, 40 insertions(+), 24 deletions(-)

diff --git a/python/qemu/machine.py b/python/qemu/machine.py
index 976316e5f5..906ca118db 100644
--- a/python/qemu/machine.py
+++ b/python/qemu/machine.py
@@ -179,20 +179,27 @@ class QEMUMachine(object):
         return sock.sendmsg([msg], [(socket.SOL_SOCKET, socket.SCM_RIGHTS,
                                       array.array("i", fds))])
 
-    def send_fd_scm(self, fd=None, file_path=None):
+    def send_fd_scm(self, fd=None, file_path=None, data=None):
         """
-        Send an fd or file_path to socket_scm_helper.
+        Can be used in two different cases.
+        Send an fd or file_path to socket_scm_helper or
+        provide data and fd to send it to the socket.
 
-        Exactly one of fd and file_path must be given.
-        If it is file_path, the helper will open that file and pass its own fd.
+        Exactly one of fd and file_path must be given to the case of
+        socket_scm_helper. If it is file_path, the helper will open that file
+        and pass its own fd.
+
+        To second case need adds data that include a QMP request and fd
         """
         # In iotest.py, the qmp should always use unix socket.
         assert self._qmp.is_scm_available()
-        if self._socket_scm_helper is None:
-            raise QEMUMachineError("No path to socket_scm_helper set")
-        if not os.path.exists(self._socket_scm_helper):
-            raise QEMUMachineError("%s does not exist" %
-                                   self._socket_scm_helper)
+        if data is None:
+            if self._socket_scm_helper is None:
+                raise QEMUMachineError(
+                    "No path to socket_scm_helper set or data provided")
+            if not os.path.exists(self._socket_scm_helper):
+                raise QEMUMachineError("%s does not exist" %
+                                       self._socket_scm_helper)
 
         # This did not exist before 3.4, but since then it is
         # mandatory for our purpose
@@ -201,24 +208,33 @@ class QEMUMachine(object):
             if fd is not None:
                 os.set_inheritable(fd, True)
 
-        fd_param = ["%s" % self._socket_scm_helper,
-                    "%d" % self._qmp.get_sock_fd()]
+        if data is None:
+            fd_param = ["%s" % self._socket_scm_helper,
+                        "%d" % self._qmp.get_sock_fd()]
+            if file_path is not None:
+                assert fd is None
+                fd_param.append(file_path)
+            else:
+                assert fd is not None
+                fd_param.append(str(fd))
 
-        if file_path is not None:
-            assert fd is None
-            fd_param.append(file_path)
-        else:
-            assert fd is not None
-            fd_param.append(str(fd))
+            devnull = open(os.path.devnull, 'rb')
+            proc = subprocess.Popen(fd_param, stdin=devnull,
+                                    stdout=subprocess.PIPE,
+                                    stderr=subprocess.STDOUT, close_fds=False)
+            output = proc.communicate()[0]
+            if output:
+                LOG.debug(output)
 
-        devnull = open(os.path.devnull, 'rb')
-        proc = subprocess.Popen(fd_param, stdin=devnull, stdout=subprocess.PIPE,
-                                stderr=subprocess.STDOUT, close_fds=False)
-        output = proc.communicate()[0]
-        if output:
-            LOG.debug(output)
+            return proc.returncode
 
-        return proc.returncode
+        else:
+            sock_fd = socket.fromfd(self._qmp.get_sock_fd(), socket.AF_UNIX,
+                                    socket.SOCK_STREAM)
+            fds_param = [fd, self._qmp.get_sock_fd()]
+            self._send_fds(sock_fd, data, fds_param)
+            self._recv_fds(sock_fd)
+            return self
 
     @staticmethod
     def _remove_if_exists(path):
-- 
2.21.1