Recommended way to import external yang

[tsiemers1]

I am looking over the guides and trying to find information on the correct way to use external yang files. For example, lets say I do not want to recreate ethernet-groupings for XE and just want to import Cisco's submodule 

Cisco-IOS-XE-interfaces 

and from there use the grouping

grouping ethernet-grouping

 Would I just copying over the "Cisco-IOS-XE-interfaces" over to the "/opt/ncs/ncs-4.7.3.1/src/ncs/yang" folder that contains all the other default talif/ietf yang files and then import it into my yang?

module TESTPKG {

  namespace "http://example.com/TESTPKG";
  prefix TESTPKG;

  import Cisco-IOS-XE-native {
    prefix xe;
  }
}

Is this recommended our is a better method preferred over copying the source yang files? Or is it better to use the ios-ned and create choices/groupings similar to the accepted solution in this thread?

Thanks

[rogaglia · Accepted solution]

Hi,

You do not need to "copy and paste", you could simply write:

uses xe:ethernet-grouping

Now, this only works because ethernet-grouping is was originally grouped. What if it wasn't? Well, there is a YANG Schema Mount standard just out of the IETF (RFC 8528) but NSO only supports it for the NEDs but not for other packages.

[tsiemers1]

Just read over the Yang Schema mount rfc, looks very handy. Any plans to release it to more than NEDS?

Also, I must be missing something trivial on getting external yang files to work in my package. I created the following structure to test a custom yang file in the /opt/ncs/current/src/ncs/yang directory.

/opt/ncs/ncs-4.7.2/src/ncs/yang/
└── test-external-pkg.yang

module test-external-pkg {

  namespace "http://example.com/test-external-pkg";
  prefix tpext;

}

When I run make on my test package src folder it comes back fine. When I went to reload NSO I got a namespace error. I tried adding it as a required-package in the package-meta-data.xml, thinking this is not the right approach but I find a similar error on this post so I tried it.

<ncs-package xmlns="http://tail-f.com/ns/ncs-packages">
  <name>testpkg</name>
  <package-version>1.0</package-version>
  <description>Generated Python package</description>
  <ncs-min-version>4.7</ncs-min-version>
  <required-package>
     <name>test-external-pkg</name>
  </required-package>
  <component>
    <name>main</name>
    <application>
      <python-class-name>testpkg.main.Main</python-class-name>
    </application>
  </component>
</ncs-package>

The reload gives the error that the package is undefined so I must be missing a piece since this isn't a package, only a single yang file.

Error: Failed to load NCS package: testpkg; required package test-external-pkg of version undefined is not present (found none)

[vleijon]

Have you added to the yang path in the makefile? So that it can reach all the files.

[tsiemers1]

I put my custom test-external-pkg.yang into the /opt/ncs/current/src/ncs/yang directory where all the other default yang files ( for example ietf-inet-types.yang)

Then ran the make command, it created my test-external-pkg.fxs inside of the /opt/ncs/current/src/ncs/yang.

After watching the debug logs of NSO trying to start I noticed that all the other default .fxs files were located in:

/opt/ncs/ncs-4.7.2/etc/ncs/

I manually moved my test-external-pkg.fxs to that above directory and it worked. 

sudo mv /opt/ncs/current/src/ncs/yang/test-external-pkg.fxs /opt/ncs/ncs-4.7.2/etc/ncs/

Still looking for docs on the correct process of adding a custom yang then getting the .fxs to create in the proper load directory. Thinking something with the way I am running the make command.

Thanks

[tsiemers1]

Looks like you can add dirs as load paths in nso.conf. I think my process now is to create yangs, run make command to get the .fxs and move it to the load directory specified in ncs.conf

<load-path>
<dir>./packages</dir>
<dir>${NCS_DIR}/etc/ncs</dir>

<!-- To disable northbound snmp altogether -->
<!-- comment out the path below -->
<dir>${NCS_DIR}/etc/ncs/snmp</dir>
</load-path>

[vleijon]

In your Makefile for your package, you can update the YANGPATH to include the path to the yang files you need.

In each package there is a load-dir where fxs files are loaded. The default makefile for a package places the fxs files there.