ovs-tcpdump: Stdout is shutdown before ovs-tcpdump exit.

If there is a pipe behind ovs-tcpdump (such as ovs-tcpdump -i eth0
| grep "192.168.1.1"), the child process (grep "192.168.1.1") may
exit first and close the pipe when received SIGTERM.  When farther
process (ovs-tcpdump) exit, stdout is flushed into broken pipe, and
then received a exception IOError.  To avoid such problems,
ovs-tcpdump first close stdout before exit.

Signed-off-by: Songtao Zhan <[email protected]>
Signed-off-by: Ilya Maximets <[email protected]>

utilities/ovs-tcpdump.in

@@ -538,6 +538,17 @@ def main():
             print(data.decode('utf-8'))
         raise KeyboardInterrupt
     except KeyboardInterrupt:
+        # If there is a pipe behind ovs-tcpdump (such as ovs-tcpdump
+        # -i eth0 | grep "192.168.1.1"), the pipe is no longer available
+        # after received Ctrl+C.
+        # If we write data to an unavailable pipe, a pipe error will be
+        # reported, so we turn off stdout to avoid subsequent flushing
+        # of data into the pipe.
+        try:
+            sys.stdout.close()
+        except IOError:
+            pass
+
         if pipes.poll() is None:
             pipes.terminate()