ovs python: ovs.stream.open_block() returns success even if the remote is unreachable

The python function ovs.socket_util.check_connection_completion() uses select()
(provided by python) to monitor the socket file descriptor. The select()
returns 1 when the file descriptor becomes ready. For error cases like -
111 (Connection refused) and 113 (No route to host) (POLLERR), ovs.poller._SelectSelect.poll()
expects the exceptfds list to be set by select(). But that is not the case.
As per the select() man page, writefds list will be set for POLLERR.
Please see "Correspondence between select() and poll() notifications" section of select(2)
man page.

Because of this behavior, ovs.socket_util.check_connection_completion() returns success
even if the remote is unreachable or not listening on the port.

This patch fixes this issue by using poll() to check the connection status similar to
the C implementation of check_connection_completion().

A new function 'get_system_poll() is added in ovs/poller.py which returns the
select.poll() object. If select.poll is monkey patched by eventlet/gevent, it
gets the original select.poll() and returns it.

The test cases added in this patch fails without the fix.

Suggested-by: Ben Pfaff <blp@ovn.org>
Signed-off-by: Numan Siddique <nusiddiq@redhat.com>
Signed-off-by: Ben Pfaff <blp@ovn.org>
Acked-by: Mark Michelson <mmichels@redhat.com>

3 files changed, 49 insertions, 0 deletions

diff --git a/tests/automake.mk b/tests/automake.mk
index 01f5077cd..49ceb415d 100644
--- a/tests/automake.mk
+++ b/tests/automake.mk
@@ -422,6 +422,7 @@ CHECK_PYFILES = \
 	tests/test-l7.py \
 	tests/test-ovsdb.py \
 	tests/test-reconnect.py \
+	tests/test-stream.py \
 	tests/MockXenAPI.py \
 	tests/test-unix-socket.py \
 	tests/test-unixctl.py \
diff --git a/tests/ovsdb-idl.at b/tests/ovsdb-idl.at
index 8db6aa462..8c5e9fe50 100644
--- a/tests/ovsdb-idl.at
+++ b/tests/ovsdb-idl.at
@@ -1730,3 +1730,19 @@ OVSDB_CHECK_IDL_COMPOUND_INDEX_WITH_REF([set, simple3 idl-compound-index-with-re
 007: check simple4: empty
 008: End test
 ]])
+
+m4_define([CHECK_STREAM_OPEN_BLOCK_PY],
+  [AT_SETUP([$1])
+   AT_SKIP_IF([test $2 = no])
+   AT_KEYWORDS([Check PY Stream open block - $3])
+   AT_CHECK([ovsdb_start_idltest "ptcp:0:127.0.0.1"])
+   PARSE_LISTENING_PORT([ovsdb-server.log], [TCP_PORT])
+   WRONG_PORT=$(($TCP_PORT+1))
+   AT_CHECK([$3 $srcdir/test-stream.py tcp:127.0.0.1:$TCP_PORT], [0], [ignore])
+   AT_CHECK([$3 $srcdir/test-stream.py tcp:127.0.0.1:$WRONG_PORT], [1], [ignore])
+   OVSDB_SERVER_SHUTDOWN
+   AT_CHECK([$3 $srcdir/test-stream.py tcp:127.0.0.1:$TCP_PORT], [1], [ignore])
+   AT_CLEANUP])
+
+CHECK_STREAM_OPEN_BLOCK_PY([Check PY2 Stream open block], [$HAVE_PYTHON], [$PYTHON])
+CHECK_STREAM_OPEN_BLOCK_PY([Check PY3 Stream open block], [$HAVE_PYTHON], [$PYTHON3])
diff --git a/tests/test-stream.py b/tests/test-stream.py
new file mode 100644
index 000000000..4a5117501
--- /dev/null
+++ b/tests/test-stream.py
@@ -0,0 +1,32 @@
+# Copyright (c) 2018, Red Hat Inc.
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at:
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+import sys
+
+import ovs.stream
+
+
+def main(argv):
+    remote = argv[1]
+    err, stream = ovs.stream.Stream.open_block(
+            ovs.stream.Stream.open(remote))
+
+    if err or stream is None:
+        sys.exit(1)
+
+    sys.exit(0)
+
+
+if __name__ == '__main__':
+    main(sys.argv)