[PATCH v2 0/3] Migration mechanism with FD

[PATCH v2 0/3] Migration mechanism with FD

[Oksana Vohchana]

To test migration through the file descriptor we should build and provide
a path to socket_scm_helper file. This way is inconvenient for acceptance
testing.
This series provides new functions to receive and send messages over a UNIX
socket. And adds a new migration test.

v2: 
 -  Fix warning of line over 80 characters

Oksana Vohchana (3):
  Adding functions _send_fds and _recv_fds
  Updates send_fd_scm function
  Acceptance test: FD migration

 python/qemu/machine.py        | 88 +++++++++++++++++++++++++----------
 tests/acceptance/migration.py | 21 +++++++++
 2 files changed, 85 insertions(+), 24 deletions(-)

-- 
2.21.1

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

[Oksana Vohchana]

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

[PATCH v2 2/3] Updates send_fd_scm function

[Oksana Vohchana]

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

[PATCH v2 3/3] Acceptance test: FD migration

[Oksana Vohchana]

Adds a new migration test through the file descriptor.

Signed-off-by: Oksana Vohchana <ovoshcha@redhat.com>
---
 tests/acceptance/migration.py | 21 +++++++++++++++++++++
 1 file changed, 21 insertions(+)

diff --git a/tests/acceptance/migration.py b/tests/acceptance/migration.py
index a8367ca023..7f4879ce5d 100644
--- a/tests/acceptance/migration.py
+++ b/tests/acceptance/migration.py
@@ -10,7 +10,10 @@
 # later.  See the COPYING file in the top-level directory.
 
 
+import os
 import tempfile
+from socket import socketpair, AF_UNIX, SOCK_STREAM
+
 from avocado_qemu import Test
 from avocado import skipUnless
 
@@ -75,3 +78,21 @@ class Migration(Test):
         """
         free_port = self._get_free_port()
         dest_uri = 'exec:nc -l localhost %u' % free_port
+
+    def test_migration_with_fd(self):
+        opaque = 'fd-migration'
+        data_to_send = b"{\"execute\": \"getfd\",  \"arguments\": \
+                        {\"fdname\": \"fd-migration\"}}"
+        send_socket, recv_socket = socketpair(AF_UNIX, SOCK_STREAM)
+        fd1 = send_socket.fileno()
+        fd2 = recv_socket.fileno()
+        os.set_inheritable(fd2, True)
+
+        source_vm = self.get_vm()
+        source_vm.launch()
+        source_vm.send_fd_scm(fd=fd1, data=data_to_send)
+
+        dest_vm = self.get_vm('-incoming', 'fd:%s' % fd2)
+        dest_vm.launch()
+        source_vm.qmp('migrate', uri='fd:%s' % opaque)
+        self.assert_migration(source_vm, dest_vm)
-- 
2.21.1