[PATCH v2 1/3] Adding functions _send_fds and _recv_fds

[Oksana Vohchana <ovoshcha@redhat.com>]

It provides new possibilities to send or receive data through the Unix domain
socket file descriptor.
This is useful for obtaining a socket that belongs to a different network
namespace.

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

diff --git a/python/qemu/machine.py b/python/qemu/machine.py
index 183d8f3d38..976316e5f5 100644
--- a/python/qemu/machine.py
+++ b/python/qemu/machine.py
@@ -24,6 +24,7 @@ import subprocess
 import shutil
 import socket
 import tempfile
+import array
 
 from . import qmp
 
@@ -155,6 +156,29 @@ class QEMUMachine(object):
         self._args.append(','.join(options))
         return self
 
+    def _recv_fds(self, sock, msglen=8192, maxfds=4096):
+        """
+        Function from:
+        https://docs.python.org/3/library/socket.html#socket.socket.recvmsg
+        """
+        fds = array.array("i")
+        msg, ancdata, flags, addr = sock.recvmsg(msglen, socket.CMSG_LEN(
+            maxfds * fds.itemsize))
+        for cmsg_level, cmsg_type, cmsg_data in ancdata:
+            if (cmsg_level == socket.SOL_SOCKET and
+                    cmsg_type == socket.SCM_RIGHTS):
+                fds.frombytes(cmsg_data[:len(cmsg_data) - (len(cmsg_data)
+                    % fds.itemsize)])
+        return msg, list(fds)
+
+    def _send_fds(self, sock, msg, fds):
+        """
+        Function from:
+        https://docs.python.org/3/library/socket.html#socket.socket.sendmsg
+        """
+        return sock.sendmsg([msg], [(socket.SOL_SOCKET, socket.SCM_RIGHTS,
+                                      array.array("i", fds))])
+
     def send_fd_scm(self, fd=None, file_path=None):
         """
         Send an fd or file_path to socket_scm_helper.
-- 
2.21.1