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86 lines
2.4 KiB
ReStructuredText
86 lines
2.4 KiB
ReStructuredText
.. _scripting-user:
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*********
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Scripting
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*********
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The behavior of FRR may be extended or customized using its built-in scripting
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capabilities. The scripting language is Lua 5.3. This guide assumes Lua
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knowledge. For more information on Lua, consult the Lua 5.3 reference manual, or
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*Programming in Lua* (note that the free version covers only Lua 5.0).
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https://www.lua.org/manual/5.3/
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http://www.lua.org/pil/contents.html
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Scripting
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=========
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.. seealso:: Developer docs for scripting
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How to use
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----------
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1. Identify the Lua function name. See :ref:`lua-hook-calls`.
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2. Write the Lua script
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3. Configure FRR to use the Lua script
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In order to use scripting, FRR must be built with ``--enable-scripting``.
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.. note::
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Scripts are typically loaded just-in-time. This means you can change the
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contents of a script that is in use without restarting FRR. Not all
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scripting locations may behave this way; refer to the documentation for the
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particular location.
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Example: on_rib_process_dplane_results
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--------------------------------------
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This example shows how to write a Lua script that logs changes when a route is
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added.
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First, identify the Lua hook call to attach a Lua function to: this will be the
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name of the Lua function. In this case, since the hook call is
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`on_rib_process_dplane_results`:
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.. code-block:: lua
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function on_rib_process_dplane_results(ctx)
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log.info(ctx.rinfo.zd_dest.network)
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return {}
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The documentation for :ref:`on-rib-process-dplane-results` tells us its
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arguments. Here, the destination prefix for a route is being logged out.
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Scripts live in :file:`/etc/frr/scripts/` by default. This is configurable at
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compile time via ``--with-scriptdir``. It may be overridden at runtime with the
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``--scriptdir`` daemon option.
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The documentation for :ref:`on-rib-process-dplane-results` indicates that the
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``script`` command should be used to set the script. Assuming that the above
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function was created in :file:`/etc/frr/scripts/my_dplane_script.lua`, the
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following vtysh command sets the script for the hook call:
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.. code-block:: console
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script on_rib_process_dplane_results my_dplane_script
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After the script is set, when the hook call is hit, FRR will look for a
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*on_rib_process_dplane_results* function in
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:file:`/etc/frr/scripts/my_dplane_script.lua` and run it with the ``ctx`` object
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as its argument.
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.. _lua-hook-calls:
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Available Lua hook calls
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========================
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:ref:`on-rib-process-dplane-results`
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