Netlink Lua

The lua library netlink.so uses the netlink socket to acquire network state information about interface links, IP addresses, routes and address resolutions.

It additionally allows to listen for netlink events and receive changes. Usage examples can be found in the examples directory.

Examples

> require"netlink".ethtool("eno1").speed
100
> require"netlink".ethtool("eno1").duplex
full
> require"inspect".inspect(require"netlink".socket():query({route=true}))
{ {
    event = "newroute",
    gateway = "192.168.178.1",
    scope = 0,
    stamp = 252071566
  }, {
    dst = "192.168.178.0/24",
    event = "newroute",
    scope = 253,
    stamp = 252071566
  } }

> s = require"netlink".socket()
> s:poll()
true
> s:event()
{ {
    event = "newlink",
    hwaddr = "ce:d4:ad:5a:e6:24",
    index = 5,
    mtu = 1500,
    name = "dummy0",
    running = false,
    stamp = 252811866,
    up = false
  } }

Functions of the netlink library

netlink.ethtool() function

Returns ethernet information about the given interface name. If an array is provided as argument, it is expected to contain an entry called name with the interface name.

If the interface is an ethernet interface, the table is filled with the following values:

• speed (10 / 100 / 1000)
• duplex (full / half)
• autoneg (true / false)
• name (interface name)

netlink.groups() function

Returns an array of strings of all known groups.

> require"inspect".inspect(require"netlink".groups())
{ "link", "ifaddr", "route", "neigh" }

netlink.socket() function

The netlink.socket() function returns a table to handle netlink events. The optional parameter is a set of netlink groups returned by netlink.groups():

local s = require"netlink".socket( { link = true, ifaddr = true } )

If unset, all supported groups will be used.

Methods of the netlink socket class

The returned table contains the entry "_mnl_userdata" which contains the netlink data. It additionally comes with the following methods:

• fd() Returns the file descriptor to be used in luaposix.poll()
• event() Returns an array of dictionaries with changed items
• query() Triggers all events, registered with netlink.socket().
• groups() Returns an array of strings of all registered groups to receive events for.
• poll() Since events() does not block and in case of no events immediately returns an empty array, poll() can be used to wait for new events.

Returned netlink data

All returned tables have the following entries:

• event: new/del + group name, e.g. newlink, delifaddr
• stamp: milliseconds since boot (CLOCK_MONOTONIC)
• index: Interface index

Event "newlink" and "dellink"

• hwaddr: The MAC address
• mtu: Maximum Transfer Unit
• name: Interface name
• up: Reflects the administrative state of the interface (IFF_UP)
• running: Reflects the operational state (IFF_RUNNING).

Event "newifaddr" and "delifaddr"

• family: AF_INET or AF_INET6
• ip: IP address

Event "newroute" and "delroute"

• scope: Sort of distance to the destination.
• gateway: Gateway IP (For scope 0)
• dst: Network (For scope 253)
• prefsrc: Preferred source address to use when sending over this route
• metric: Route metric

Event "newneigh", and "delneigh"

• hwaddr: The resolved MAC address associated with the requested IP address
• ip: Requested IP address
• state: One out of: "reachable", "stale", "failed"
• probes: Number of probes