RPC edit-config payloads are not fully validated

[olofhagsand]

It has been observed that if a load file operation (eg cli_load_syntax_file()) loads an invalid XML file (invalid from a YANG perspective), the RPC edit-config operation forwards the invalid XML to the backend, the backend does not check the sanity of the invalid XML, resulting in errors in the datastore.
Example: openconfig-network-instance. If a file contains:

<config>
   <network-instances xmlns="http://openconfig.net/yang/network-instance">
      <network-instance>
         <name>A</name>
         ...
      </network-instance>
   </network-instances>
   <network-instances xmlns="http://openconfig.net/yang/network-instance">
      <network-instance>
         <name>B</name>
         ...
      </network-instance>
   </network-instances>
</config>

where the top-level container "network-instances" are invalid. Only a single container is allowed.
This results in an edit-config with two containers which are not discarded by the backend.
The backend needs to validate the incoming payload
For RFC reference, see RFC 7950 Section 8.3:

8.3.  NETCONF Constraint Enforcement Model
   For configuration data, there are three windows when constraints MUST
   be enforced:
   o  during parsing of RPC payloads
   o  during processing of the <edit-config> operation

[olofhagsand]

Added checks of top-level objects at edit-config time.
Note that this is not a full validation, but only a check that the top-level config objects obey basic enumeration rules.
If they are not checked, operations on the datastore may result in invalid XML in the datastore.
Full validation is made at regular validation time, ie "load; validate"
@pheller please verify patch?

[pheller]

vagrant@ubuntu2004:~$ cat two-netinst-containers.xml | clixon_netconf -f /usr/local/etc/example.xml -q0
<rpc-reply xmlns="urn:ietf:params:xml:ns:netconf:base:1.0" message-id=""><rpc-error><error-type>protocol</error-type><error-tag>operation-failed</error-tag><error-app-tag>too-many-elements</error-app-tag><error-severity>error</error-severity><error-path>/rpc/edit-config/config/network-instances</error-path></rpc-error></rpc-reply>]]>]]>

vagrant@ubuntu2004:~$ cat one-netinst-container.xml | clixon_netconf -f /usr/local/etc/example.xml -q0
<rpc-reply xmlns="urn:ietf:params:xml:ns:netconf:base:1.0" message-id=""><ok/></rpc-reply>]]>]]>

Looks right to me.

[olofhagsand]

Verified, thanks ^