[Qemu-block] [PATCH 2/3] qemu-iotests: improve nbd-fault-injector.py startup protocol

[Stefan Hajnoczi]

Currently 083 waits for the nbd-fault-injector.py server to start up by
looping until netstat shows the TCP listen socket.

The startup protocol can be simplified by passing a 0 port number to
nbd-fault-injector.py.  The kernel will allocate a port in bind(2) and
the final port number can be printed by nbd-fault-injector.py.

This should make it slightly nicer and less TCP-specific to wait for
server startup.  This patch changes nbd-fault-injector.py, the next one
will rewrite server startup in 083.

Signed-off-by: Stefan Hajnoczi <address@hidden>
---
 tests/qemu-iotests/nbd-fault-injector.py | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/tests/qemu-iotests/nbd-fault-injector.py 
b/tests/qemu-iotests/nbd-fault-injector.py
index 6c07191a5a..1c10dcb51c 100755
--- a/tests/qemu-iotests/nbd-fault-injector.py
+++ b/tests/qemu-iotests/nbd-fault-injector.py
@@ -235,11 +235,15 @@ def open_socket(path):
         sock = socket.socket()
         sock.setsockopt(socket.SOL_SOCKET, socket.SO_REUSEADDR, 1)
         sock.bind((host, int(port)))
+
+        # If given port was 0 the final port number is now available
+        path = '%s:%d' % sock.getsockname()
     else:
         sock = socket.socket(socket.AF_UNIX)
         sock.bind(path)
     sock.listen(0)
     print 'Listening on %s' % path
+    sys.stdout.flush() # another process may be waiting, show message now
     return sock
 
 def usage(args):
-- 
2.13.5