Lua is loaded into an empty namespace, preventing key Lua functions

[Cerebus]

Description

The Lua scripting environment loads the user script into an empty namespace, preventing necessary Lua functions like pairs() and ipairs form working. This makes it impossible to iterate over Lua tables, which is pretty important capability.

Version

Hello, this is FRRouting (version 10.2-dev_git20240920)

How to reproduce

Try the following:

function on_rib_process_dplane_results(ctx)
    if ctx.rinfo.zd_ng then
        for k, v in pairs(ctx.rinfo.zd_ng) do
            log.info("entry=" .. k .. " ifindex=" .. v.ifindex)
        end
    end
    return {}
end

Expected behavior

I should get a log entry for each entry in the nexthop group.

Actual behavior

The script will throw an exception:

Lua hook call 'on_rib_process_dplane_results' : runtime error: /etc/frr/scripts/logger.lua:3: attempt to call a nil value (global 'pairs')

Additional context

This kind of error is typical in Lua modules that use the deprecated module() function to create modules. This function creates a new namespace (or table, b/c it's Lua everything is a table) for the module definitions, and the global namespace is no longer accessible. Welcome to Lua. :)

See here for more detail:

http://lua-users.org/wiki/ModulesTutorial

See also #16847.

Checklist

• I have searched the open issues for this bug.
• I have not included sensitive information in this report.

[ton31337]

Should be fixed by #16907.

[Cerebus]

Finally back to this task. Confirmed on current HEAD. Thanks much.