README-rebuild
Table of contents
1. General
1.1 Overview
The accedian-skylight_rc NED is delivered without any YANG models in the package.
The models do need to be downloaded, followed by a rebuild and reload of the package before the NED can be fully operational.
This NED contains an optional built-in tool that makes downloading of the device models easy.
Alternatively, manual download is possible as described in chapter 4.
The NED package (i.e with no device models) must first be properly configured in a running NSO environment prior to usage of the downloader tool. The steps described in chapter 1.1 through 1.3 in the README.md must be done prior to this step.
1.2 Using the built-in tool for simple YANG download
The downloader tool is implemented as an NSO RPC which can be invoked for instance from the NSO CLI.
When the tool is executed the NED will automatically connect to the device for which the YANG models shall be downloaded. The device will be requested to return a list of supported models when the NED is probing it for capabilities.
This list of models will be the base used by the tool when downloading the models. During operation the tool will also scan each downloaded YANG file for additional dependencies through import/include found. The tool will try to download all such dependency YANG files as well.
Since currently all Accedian-skylight devices tested with this NED do not support direct YANG model download from the device, the models need to be fetched from elsewhere.
By default the Accedian-skylight repository on github is used as source for all YANG files.
Simple Usage
The Accedian-skylight device does not support model discovery as specified by RFC8040. In order to download the yang models for the device, several configuration needs to be done on the NED side to be able to pull the model from the GIT repo.
Disabling auto-discovery features of the NED: By default, NED will try to discover the RESTCONF URL base, along with capabilities and yang models. Since the device does not support these features, they need to be disabled:
Commit the changes and proceed to the next step.
Inject modules that needs to be downloaded. By default, the NED has no knowledge of the yang module names that are needed, since the module names are not advertised by Accedian Skylight gateway. In order to make the module names known to the NED, they have to be manually injected using ned-settings:
Note: this is the extensive list of modules. It is not mandatory to use all the modules - eg if Accedian-session-y1564 is not actually needed, it can be ommited in the list, thus NED will skip it for download. Once done, commit the ned-settings.
List the download profiles To ease the download process, the NED implements necessary information to download the Accedian Skylight yang model from the following GIT repository: https://github.com/Accedian/skylight-yang.git To list the download profile, run the following RPC:
NOTE: the download profile is based on the 'release/24.09' tag. If another GIT tag is needed, please check chapter 3 for additional options
Downloading the models:
After this step, the NED contains the Accedian Skylight yang models in the proper location, which means the NED needs to be rebuilt with the new model.
For more advanced options using the downloader tool, see chapter 3.
Chapter 5('rpc get-modules') in README.md describes more details about the downloader tool, including all available command line arguments.
1.3 Rebuild the NED with the downloaded YANG models
The NED must be rebuilt when the device models have been downloaded and stored properly.
Very often there are known issues related to building the device YANG models. Such issues typically cause compiler errors or unwanted runtime errors/behaviours in NSO.
The NED is configured to take care of all currently known build/runtime issues. It will automatically patch the problematic files such that they do build properly for NSO. This is done using a set of YANG build recipes bundled with the NED package.
Note that the work with adapting the YANG build recipes is an ongoing process. If new issues are found the Cisco NSO NED team will update the recipes accordingly and then release a new version of the NED.
It is strongly recommended that end users report new YANG build issues found back to the Cisco NSO NED team through a support request
The NED provides two alternatives for rebuilding. It can be done either through NSO using a built-in tool, or by invoking gnu make in an external shell.
Rebuild using the built-in tool
The built-in rpc rebuild-package does rebuild the NED package by automatically invoking gnu make in the source directory of the package installation root.
Note: this rpc can take a long time to finish. This is because compiling YANG models is a very time consuming task.
Additional arguments:
Rebuild using a separate shell
The NED must be rebuilt from inside the NED package installation root (i.e $NED_ROOT_DIR configured in chapter 1.1 in README.md).
To rebuild the NED do as follows:
1.4 Reload the NED package in NSO
When the NED has been successfully rebuilt with the device models it is necessary to reload the package into NSO.
Reloading
Use the following NSO CLI command:
Note, if the NED packages has been rebuilt with a new NED-ID as described in chapter 5 it will be necessary to add 'force' to the reload command:
2. Removing all downloaded YANG models
If a new set of YANG models is going to be downloaded for an already installed and reloaded NED it is highly recommended to first remove all old device YANG models from the previous download.
2.1 Clean the NED source directory
Use the following make target to remove all previously downloaded YANG.
Clean using the built-in tool
Clean using a separate shell
3. Using the built-in downloader tool for a custom download
Using a pre-configured download profile is the easiest way for downloading the device YANG models.
In case this is not a suitable approach, the downloader tool has a number of additional arguments that allows for doing a custom download. For instance by limiting the scope for downloading the YANG models.
3.1 Creating a custom download
Use the 'module-include-regex' and 'module-exclude-regex' to customize the download scope. Both arguments shall be specified as regular expressions.
The easiest way to get the arguments right is by using the RPC named 'list-modules'
Note: the Accedian Skylight does not support model discovery for listing modules. For this reason, the modules needs to be specified using ned-settings. Please check chapter 1.2 to see how to inject modules. Once the models are known to the NED, custom download procedure can be follwed. By default, the NED implements a download profile that is based on the Accedian Skylight yang model git repo, for the tag release/24.09. If another git tag is needed, a custom download RPC can be used from the NED side:
Explanations:
remote: this is the method of download. in the above example, we are using git method
repository: this is the git repository
checkout: this is the git tag or branch to be used for the model
dir: the path in the git repo where the models are stored
module-exclude-regex: regular expression for modules to be excluded from the download. in the above example, all modules matching ietf-.* are excluded because they are already included in NSO distribution
See chapter 5 in README.md for more details about the RPC commands get-modules and list-modules.
4. Alternative download methods
The device models can of course also be downloaded manually. To use this option the NED package must first be unpacked. The steps described in README.md chapter 1.1 must be done first. It is preferred to do the chapter 1.2 and 1.3 steps in README.md as well.
4.1 Copy the files into the NED source directory
When the YANG models have been downloaded manually, all the files need to be copied into the source directory of the NED installation:
Note, YANG files with names like <module name>@<date revision>.yang need to be renamed to .yang.
This is because of a limitation in the current NED make system.
This manual procedure is equivalent to using the downloader tool with a path to local directory as remote source. See chapter 5('rpc get-modules') in README.md for more info.
Please do not remove any of the the yang files used internally by the NED in the $NED_ROOT_DIR/src/yang
This applies to the following files:
The best way to clean the source directory is to follow the steps in chapter 5.
5. Rebuilding the NED using a custom NED-ID
A common use case is to have many different versions of the same device in the network controlled by NSO. Each device will then have its unique set of YANG files which this NED has to be rebuilt for.
To setup NSO for this kind of scenario, each built flavour of the built NED must have its own unique NED-ID.
This will make NSO allow multiple versions of the same NED package to co-exist.
Rebuilding with a custom NED-ID can be done in the alternative ways:
Through the built-in rpc, using the following additional arguments:
suffix
major
minor
Through gmake in a separate shell, using the following additional make variables:
NED_ID_SUFFIX
NED_ID_MAJOR
NED_ID_MINOR
The default NED-ID is: accedian-skylight_rc-gen-3.0
5.1 Rebuild with a custom NED-ID
Do as follows to build each flavour of the accedian-skylight_rc NED. Do it in iterations, one at the time:
Follow the instructions in chapter 1.1 to 1.3 in README.md to unpack the NED and install a device instance using it. Make sure a unique location is selected and update the environment variable $NED_ROOT_DIR accordingly and configure a device instance.
Follow the instructions in chapter 1.2 to download the YANG models matching the configured device.
Follow the instructions in chapter 1.3 to rebuild the NED.
Alternative 1: Use the built-in rpc to rebuild with custom NED-ID
Use any combination of the additional ned-id arguments major, minor and suffix
Two examples showing NED-ID adapted for "device version" 21.6:
This will generate a NED-ID like: 'accedian-skylight_rc-r21.6-gen-1.0'
This will generate a NED-ID like: 'accedian-skylight_rc-gen-21.6'
Alternative 2: Rebuild the NED using gnu make from a shell
Add any combination of the additional make variables 'NED_ID_SUFFIX','NED_ID_MAJOR' and 'NED_ID_MINOR' to the command line.
Two examples showing NED-ID adapted for "device version" 21.6:
This will generate a NED-ID like: 'accedian-skylight_rc-r21.6-gen-1.0'
This will generate a NED-ID like: 'accedian-skylight_rc-gen-21.6'
Follow the instructions in chapter 1.4 to reload the NED package. The rebuilt NED package will now have the NED-ID:
accedian-skylight_rc<NED_ID_SUFFIX>-gen-<NED_ID_MAJOR>.<NED_ID_MINOR>This is detected by NSO and will have the following side effects:
The default NED-ID will no longer exist after the packages has been reloaded in NSO. Hence, any devices configured with the default NED-ID can no longer exist either.
It is recommended to delete all device instances using the default NED-ID before reloading the packages in NSO.
It is necessary to use 'packages reload force' when reloading the packages in NSO.
Reconfigure the device instance from step #1 in this list. Now use the new NED-ID
Verify functionality by executing a 'sync-from' on the configured device instance.
5.2 Exporting the rebuilt NED package
When the NED has been rebuilt with a new NED-ID, it typically needs to be exported as a separate NED package. This new package will then be a ready to use NED containing the raw as well as the customized and compiled versions of the third party YANG models. This package can then be loaded into a new NSO instance etc just like any other NED.
The NED has a built-in tool to make the export procedure easy. It is implemented as an additional rpc which can be invoked through the NSO CLI or any other northbound NSO interface.
It copies all relevant elements from the "source" directory of rebuilt NED into a tar.gz archive file. The top dir of the archive will be named in accordance with the generated NED-ID, i.e. accedian-skylight_rc<NED_ID_SUFFIX>-gen-<NED_ID_MAJOR>.<NED_ID_MINOR>.
Usage:
Additional arguments:
6. YANG fixes applied when rebuilding the NED
Third party YANG files often have errors that can cause problems during compilation and/or at runtime.
Common examples of such are besides pure YANG bugs, also specific NSO incompatible YANG constructs or that the device does not obey the models properly.
The NED build system is instrumented with a set of tools that is able to automatically apply various kinds of fixes to the third party YANG files. These fixes, referred to as YANG recipes, ensure that the YANG files will compile properly when the NED package is being rebuilt. This of course only refers to the YANG file versions that have so far been verified by the Cisco NED team. New build time issues can still occur if the NED is rebuilt with unverified YANG file versions.
It is encouraged to contact the Cisco NED team on any such issue by opening a support ticket. See chapter 8 in the README.md for further information.
Below is a description of the YANG recipes currently in use by the accedian-skylight_rc NED.
7. Advanced: repairing YANG modules
Many third party YANG models are plagued with issues preventing them from being compiled and/or used with NSO. They simply need to be repaired.
This NED package has been verified to work with device models and YANG model revisions listed in the README.md. Any issues that were discovered in the listed revisions have been fixed, and the fixes are already included in the package.
However, there is always a risk that new problems related to the YANG models will emerge. For example, if the NED is used together with YANG models that have not been verified by the Cisco NED team. Another example could be if the NED is used in a new use case that has not previously been verified.
If this happens, new YANG repair might be necessary.
It is encouraged to contact the Cisco NED team for help in any such matter.
Create a support case with a description of the issue and the use case. Follow the instructions in the README.md.
There is of course also a do it yourself option. This is mainly for the advanced user though. Good knowledge about the YANG modelling language is required. The NED is bundled with a set of tools to help automating YANG repair. This chapter is intended to give an overview of how to use them.
7.1 Different kinds of YANG related issues
When preparing the YANG modules for use with NSO, we can classify the kind issues found in the YANG modules as either to be of compile-time, or run-time character.
With compile-time we mean an issue which needs to be fixed to be able to at all compile and load the YANG into NSO, whereas a run-time issue is anything that needs to be addressed after the YANG is successfully compiled (e.g. invalid constraints which are not met by actual device).
7.2 Compile-time issues
The first step before using the YANG modules in NSO is to make sure they can be compiled properly. For convenience, most standard issues found in YANG are by default automatically patched when compiling the package, in which case the resulting files will be found in src/tmp-yang (NOTE: the original YANG-files in src/yang are not modified).
This is controlled by the make variable AUTOPATCH_YANG_NED. Usually it is enabled already in the NED make file $NED_ROOT_DIR/src/Makefile, like below:
The auto patcher feature does only fix the most standard issues.
If the YANG compilation still fails, like in the example below, further actions are necessary:
Always try to avoid modifying the original files in src/yang. Instead use the available tools to do the patching at compile-time, with the results ending up in src/tmp-yang where the make process always places the actual files currently in use.
The NED is bundled with three different YANG pre-processor tools that can be used to patch the YANG files at compile-time:
schypp
jypp
ypp
7.2.1 The schypp tool
This is the schema aware YANG pre-processor tool. It is automatically invoked at compile-time and reads directives from the file $NED_ROOT_DIR/src/customize-schema.schypp.
Each line in this file contains one directive, starting with one of the keywords add, remove, replace, or inline-type. This keyword is followed by the globally unique schema-path for the node to 'operate' on. No line breaks allowed.
If prefix is needed for a non-unique name in the path, the prefix must be the same as declared by the module. Depending on the type of operation the schema-path shall be followed by '::' (i.e. two colons) followed by further arguments as needed. The details for each type is described below.
The following directives are supported:
inline-type
add
delete
replace
The inline-type
This is applicable for leafs of type leafref. The tool looks up the type of the referred leaf and inlines the same type on the referee.
Very useful for all kinds of YANG issues related to leafrefs etc.
Syntax:
Example:
The add
For adding YANG statements to the schema.
Syntax:
Example:
The remove
For removing YANG statement from the schema.
Syntax:
Example:
The replace
For replacing YANG statements in the schema. In this case the matching statement (must be unique match) is replaced by the given statement(s), same rules for stmt-match and YANG-stmt(s) as for add/remove.
7.2.2 The jypp tool
This tool is implemented in Java. Hence its name. Everything you can do with the schypp tool can also be done with this tool. The big difference is that it is YANG model aware instead of schema aware. It needs a "path" in the YANG model file to the node/area to operate on.
To find out the path, do as follows:
Find out the name of the file that contains the declaration of the node to operate on.
Open the file and search for the node to operate on.
Run the jypp tool from a shell like below:
Example:
The range for MPLS label values, specified in the file openconfig-mpls-types.yang line 278, needs to be modified.
Run the tool to find out the YANG path to it:
The path is: /#mpls-label/type/#uint32/range
With a correct path following operations are supported by the jypp tool:
--add-stmt
--remove-stmt
-- remove-all
--replace-stmt
The --add-stmt
Add extra statement to the node identified by the YANG path
Syntax:
Example:
The --remove-stmt
Remove a statement identified by the YANG path.
Syntax:
Example:
The --replace-stmt
Replace a statement on the node identified by the YANG path.
Syntax:
Example:
Test executing the new jypp rules from a shell and verify that the corresponding files in tmp-yang have been modified accordingly. When you have a set of jypp rules that works, it is time to install them into the make machinery. This ensures that they are automatically applied every time the NED package is re-built.
Open the file $NED_ROOT_DIR/src/ned-custom.mk. Scroll to the make target do-profile-default and add the new jypp rules to it.
Example:
7.2.3 The ypp tool
This is the oldest of the three YANG pre-processor tools. It is a pattern match oriented text processing utility. The patterns are made of regular expressions. The ypp tool is basically like an advanced sed. Everything you can do with schypp and jypp can also be done with ypp. In most cases schypp and jypp are superior and more easy to use. However, sometimes the ypp tool is the only possible option.
Syntax:
Example:
Test executing the new ypp rules from a shell and verify that the corresponding files in tmp-yang have been modified accordingly. When you have a set of ypp rules that works, it is time to install them into the make machinery. This ensures that they are automatically applied every time the NED package is re-built.
Open the file $NED_ROOT_DIR/src/ned-custom.mk. Scroll to the make target do-profile-default and add the new jypp rules to it.
Example:
7.2.4 Verify the YANG repair
There is a separate make target to only do the 'pre-processing' of the YANG modules, i.e. automatic patching and application of 'local' schema customizations, it is run like this:
When run, one can immediately see the resulting YANG modules in the directory src/tmp-yang (i.e. this is what will be used by the NED at run-time).
7.3 Run-time issues
After all YANG modules can be compiled and loaded into NSO, there might still be issues which are only discovered at run-time. These might be constraints that are present in the YANG module but which are not strictly met by the device, such as integer value ranges or leafref targets. These kind of issues need to be investigated with real config from the device, hence a NED instance needs to be able to connect to device and do a full sync-from.
For example, if the device returns config containing a leaf of type leafref whose target is missing, when doing a full sync-from, NSO might say something like:
This indicates that the device is not fully compliant with the YANG models it is using. Hence, the YANG needs further repair.
Use the same toolkit as described in 6.2 to fix run-time issues.
The issue described above can for example be repaired with an additional schypp statement:
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