lib/flua: Add bindings for libifconfig

[freqlabs]

Summary

Add Lua bindings for libifconfig to flua.

Throwing this on phab to see if anyone has a use case for it. Otherwise, I don't have plans to commit it yet. libifconfig really should have more features.

Test Plan

#!/usr/libexec/flua

ifcfg = require('ifconfig').open()
ucl = require('ucl')

ifaces = ifcfg:foreach_iface(function(_, iface, ifs)
    local name = iface:name()
    ifs[name] = {
        media = ifcfg:get_media(name),
        status = ifcfg:get_status(name),
        capabilities = ifcfg:get_capability(name),
        groups = ifcfg:get_groups(name),
        metric = ifcfg:get_metric(name),
        mtu = ifcfg:get_mtu(name),
        nd6 = ifcfg:get_nd6(name),
        lagg_status = ifcfg:get_lagg_status(name),
        laggdev = ifcfg:get_laggport_laggdev(name),
        addresses = ifcfg:foreach_ifaddr(iface, function(_, addr, addrs)
            table.insert(addrs, ifcfg:addr_info(addr))
            return addrs
        end, {})
    }
    return ifs
end, {})

function yaml(obj)
    print(ucl.to_format(obj, "yaml"))
end

yaml(ifaces)

ifcfg:get_status("usb")
print(ifcfg:error())

[kevans]

Tossing kp in the mix for the giggles of it

[freqlabs]

Perhaps useful for network testing purposes?

[pstef]

I can see some potential for automation and orchestration.

[kp]

Without immediate users for this it's probably a bit early to commit this, but I like the notion.
If nothing else it gives a bit more sample code of how we can wrap things in Lua, and I could also see use cases for base-system scripting where we may want something other than shell to do things in.

[freqlabs]

Thanks for the feedback. Definitely early days for all this. I'm continuing the work over on gitlab to avoid too much phabricator spam for the time being :)
https://gitlab.com/freqlabs/lua-libifconfig

[freqlabs]

Updated diff to include man page, example code, build as a lua module instead of embedded in flua.
Diff is based on flua-libjail going in first.

There is still quite a bit of functionality missing from libifconfig that makes this feel poorly fleshed out.

[gbe]

From the first look the man page should be fine. Did you run igor and mandoc -Tlint against it?

[freqlabs]

Incorporated changes to libifconfig.

[freqlabs]

Avoid tracking stack index manually when we know the position relative to the top. We're usually using the index to set a field on a table immediately under a value on the top of the stack, so the index can be specified as -2 rather than the absolute index.

Fixed empty media options table. I forgot to pop the option names off the stack and into the table after pushing the string.

Further refinement of the media table format: rather than setting "<unknown type>", "<unknown subtype>", or "<unknown mode>", just leave the field out of the table and let the caller decide if/how they want to display the nil field. This idea stems from mode only really being a thing for wifi, and seeing "mode": "<unknown mode>" on every Ethernet interface for example is not ideal.

Note to self: update the documentation for the mode table format in the man page, too.

[freqlabs]

In D25447#609400, @gbe wrote:

From the first look the man page should be fine. Did you run igor and mandoc -Tlint against it?

Yes, apart from the date they both come back clean.

[freqlabs]

Changed the format of lagg ports to a table keyed by the interface name, so rather than

"ports": [
    {
        "lacp_state": [
            "ACTIVITY",
            "AGGREGATION",
            "SYNC",
            "COLLECTING",
            "DISTRIBUTING"
        ],
        "flags": [
            "ACTIVE",
            "COLLECTING",
            "DISTRIBUTING"
        ],
        "laggport": "igb0"
    },
    {
        "lacp_state": [
            "ACTIVITY",
            "AGGREGATION",
            "SYNC",
            "COLLECTING",
            "DISTRIBUTING"
        ],
        "flags": [
            "ACTIVE",
            "COLLECTING",
            "DISTRIBUTING"
        ],
        "laggport": "igb1"
    }
],

we now have

"ports": {
    "igb0": {
        "lacp_state": [
            "ACTIVITY",
            "AGGREGATION",
            "SYNC",
            "COLLECTING",
            "DISTRIBUTING"
        ],
        "flags": [
            "ACTIVE",
            "COLLECTING",
            "DISTRIBUTING"
        ]
    },
    "igb1": {
        "lacp_state": [
            "ACTIVITY",
            "AGGREGATION",
            "SYNC",
            "COLLECTING",
            "DISTRIBUTING"
        ],
        "flags": [
            "ACTIVE",
            "COLLECTING",
            "DISTRIBUTING"
        ]
    }
},

Updated the man page to reflect recent changes to table formats.