ncclient subscribe to netconf stream problem with NSO version 5.2

[cabottch@cisco.com]

Dear Community,

Can not subscribe to a netconf stream using ncclient (same code working well with NSO version 4.7). 

Code:

from ncclient import manager

def start():
  conn=manager.connect(host="192.168.137.235", port=2022, username="admin", password="admin", device_params={'name': "default"}, timeout=30, hostkey_verify=False, unknown_host_cb=True, look_for_keys=False)
  print conn.create_subscription(stream_name="ncs-events")
  while True:
    print conn.take_notification().notification_xml

if __name__ == '__main__':
  start()

Error:

Traceback (most recent call last):
  File "stream-ncs-events.py", line 12, in <module>
    start()
  File "stream-ncs-events.py", line 7, in start
    print conn.create_subscription(stream_name="ncs-events")
  File "/usr/local/lib/python2.7/dist-packages/ncclient/manager.py", line 236, in execute
    huge_tree=self._huge_tree).request(*args, **kwds)
  File "/usr/local/lib/python2.7/dist-packages/ncclient/operations/subscribe.py", line 64, in request
    return self._request(node)
  File "/usr/local/lib/python2.7/dist-packages/ncclient/operations/rpc.py", line 349, in _request
    raise self._reply.error
ncclient.operations.rpc.RPCError: {'info': '<?xml version="1.0" encoding="UTF-8"?><error-info xmlns="urn:ietf:params:xml:ns:netconf:base:1.0" xmlns:nc="urn:ietf:params:xml:ns:netconf:base:1.0"><bad-element>stream</bad-element>\n</error-info>\n', 'severity': 'error', 'tag': 'unknown-element', 'path': '\n    /rpc/p0:create-subscription\n  ', 'message': None, 'type': 'protocol'}

stream is there:

admin@ncs# show notification stream ?
Possible completions:
  SPWIFI          SP-WIFI-stream
  kicker-events   NCS event according to tailf-kicker.yang
  ncs-events      NCS event according to tailf-ncs-devices.yang

Thanks in advance for your help.

[gmuloche · Accepted solution]

Hello

managed to reproduce same error python 3.7 ncclient 6.6.0 and NSO 5.2.1

looking at netconf trace:

#309
<nc:rpc message-id="urn:uuid:86a933bc-510b-4be9-ace9-809af87bba52" xmlns:nc="urn:ietf:params:xml:ns:netconf:base:1.0">
  <ns0:create-subscription xmlns:ns0="urn:ietf:params:xml:ns:netconf:notification:1.0">
    <nc:stream>ncs-events</nc:stream>
  </ns0:create-subscription>
</nc:rpc>

using netconf console (coming with NSO)

netconf-console -d  --host 127.0.0.1 --port 2022 --create-subscription ncs-events

looking at netconf trace:

#266
<rpc message-id="1" xmlns="urn:ietf:params:xml:ns:netconf:base:1.0">
  <create-subscription xmlns="urn:ietf:params:xml:ns:netconf:notification:1.0">
    <stream>ncs-events</stream>
  </create-subscription>
</rpc>

Looks like a NS problem you can track in ncclient library to xml_.py file (sub_ele / qualify lambda that insert BASE_NS_1

I patched my library like this (ncclient/operations/subscribe.py):

   53         if stream_name is not None:
   54             # Original commented
   55             # sub_ele(node, "stream").text = stream_name
CC 56             sub_ele_ns(node, "stream", NETCONF_NOTIFICATION_NS).text = stream_name

and your script started working.

looking at netconf trace:

#311
<nc:rpc message-id="urn:uuid:6fe34aa2-7b08-4b68-8a7f-ceef96a3d986" xmlns:nc="urn:ietf:params:xml:ns:netconf:base:1.0">
  <ns0:create-subscription xmlns:ns0="urn:ietf:params:xml:ns:netconf:notification:1.0">
    <ns0:stream>ncs-events</ns0:stream>
  </ns0:create-subscription>
</nc:rpc>

Bottom line: you can patch the library (hmmm maybe open a github issue for this ?) - or use netconf-console! 

Corollary: probably you will need to do the sub_ele_ns trick for filter and start/stop times if you want to continue using ncclient

Why was it working before? maybe a less strict checking of namespaces in NSO 4.x ? (I have in mind restconf enforcing namespaces starting NSO 5.x)

Hope that helps!

[cabottch@cisco.com]

Thanks so much for your help!!!