qemu-iotests: add infrastructure of fd passing via SCM

This patch make use of the compiled scm helper program to transfer
fd via unix socket at runtime.

Signed-off-by: Wenchao Xia <xiawenc@linux.vnet.ibm.com>
Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>

QMP/qmp.py

@@ -188,3 +188,9 @@ def close(self):
 
     def settimeout(self, timeout):
         self.__sock.settimeout(timeout)
+
+    def get_sock_fd(self):
+        return self.__sock.fileno()
+
+    def is_scm_available(self):
+        return self.__sock.family == socket.AF_UNIX

tests/qemu-iotests/check

@@ -164,6 +164,7 @@ QEMU_IO       -- $QEMU_IO
 IMGFMT        -- $FULL_IMGFMT_DETAILS
 IMGPROTO      -- $FULL_IMGPROTO_DETAILS
 PLATFORM      -- $FULL_HOST_DETAILS
+SOCKET_SCM_HELPER -- $SOCKET_SCM_HELPER
 
 EOF
 #MKFS_OPTIONS  -- $FULL_MKFS_OPTIONS

tests/qemu-iotests/iotests.py

@@ -38,6 +38,8 @@
 imgproto = os.environ.get('IMGPROTO', 'file')
 test_dir = os.environ.get('TEST_DIR', '/var/tmp')
 
+socket_scm_helper = os.environ.get('SOCKET_SCM_HELPER', 'socket_scm_helper')
+
 def qemu_img(*args):
     '''Run qemu-img and return the exit code'''
     devnull = open('/dev/null', 'r+')
@@ -80,6 +82,12 @@ def __init__(self):
                      '-display', 'none', '-vga', 'none']
         self._num_drives = 0
 
+    # This can be used to add an unused monitor instance.
+    def add_monitor_telnet(self, ip, port):
+        args = 'tcp:%s:%d,server,nowait,telnet' % (ip, port)
+        self._args.append('-monitor')
+        self._args.append(args)
+
     def add_drive(self, path, opts=''):
         '''Add a virtio-blk drive to the VM'''
         options = ['if=virtio',
@@ -112,6 +120,21 @@ def add_fd(self, fd, fdset, opaque, opts=''):
         self._args.append(','.join(options))
         return self
 
+    def send_fd_scm(self, fd_file_path):
+        # In iotest.py, the qmp should always use unix socket.
+        assert self._qmp.is_scm_available()
+        bin = socket_scm_helper
+        if os.path.exists(bin) == False:
+            print "Scm help program does not present, path '%s'." % bin
+            return -1
+        fd_param = ["%s" % bin,
+                    "%d" % self._qmp.get_sock_fd(),
+                    "%s" % fd_file_path]
+        devnull = open('/dev/null', 'rb')
+        p = subprocess.Popen(fd_param, stdin=devnull, stdout=sys.stdout,
+                             stderr=sys.stderr)
+        return p.wait()
+
     def launch(self):
         '''Launch the VM and establish a QMP connection'''
         devnull = open('/dev/null', 'rb')