vintage_net: An Elixir repository from jthacker

NOTE: If you've been using vintage_net v0.6.x or earlier, we split out network technology support out to separate libraries in v0.7.0. You'll need to add those libraries to your mix dependency list and rename some atoms. Configurations stored on deployed devices will be automatically updated. See the v0.7.0 release notes for details.

VintageNet is network configuration library built specifically for Nerves Project devices. It has the following features:

Ethernet and WiFi support included. Extendible to other technologies
Default configurations specified in your Application config
Runtime updates to configurations are persisted and applied on next boot (configurations are obfuscated by default to hide WiFi passphrases)
Simple subscription to network status change events
Connect to multiple networks at a time and prioritize which interfaces are used (Ethernet over WiFi over cellular)
Internet connection monitoring and failure detection
Predictable network interface names

TL;DR: Don't care about any of this and just want the string to copy/paste to set up networking? See the VintageNet Cookbook.

The following network configurations are supported:

Wired Ethernet, IPv4 DHCP
Wired Ethernet, IPv4 static IP
WiFi password-less and WEP
WPA2 PSK and EAP
USB gadget mode Ethernet, IPv4 DHCP server to supply host IP address
Cellular networks (see vintage_net_mobile for details)
WiFi AP mode
IPv6 - Partially supported. SLAAC configuration works.

vintage_net takes a different approach to networking from nerves_network. Its focus is on building and applying network configurations. Where nerves_network provided configurable state machines, vintage_net turns human-readable configurations into everything from configuration files and calls to ip to starting up networking GenServers and routing table updates. This makes it easier to add support for new network technologies and features. While Elixir and Erlang were great to implement network protocols in, it was frequently more practical to reuse embedded Linux implementations. Importantly, though, vintage_net monitors Linux daemons under its OTP supervision tree so failures on both the "C" and Elixir sides propagate in the expected ways.

Another important difference is that VintageNet doesn't attempt to make incremental modifications to configurations. It completely tears down an interface's connection and then brings up new configurations in a fresh state. Network reconfiguration is assumed to be an infrequent event so while this can cause a hiccup in the network connectivity, it removes state machine code that made nerves_network hard to maintain.

Installation

First, if you're modifying an existing project, you will need to remove nerves_network and nerves_init_gadget. vintage_net doesn't work with either of them. You'll get an error if any project references those packages.

There are two routes to integrating vintage_net:

Use nerves_pack. nerves_pack is like nerves_init_gadget, but for vintage_net.
Copy and paste from vintage_net_example

The next step is to make sure that your Nerves system is compatible. The official Nerves systems released after 12/11/2019 work without modification. If rolling your own Nerves port, you will need the following Linux kernel options enabled:

CONFIG_IP_ADVANCED_ROUTER=y
CONFIG_IP_MULTIPLE_TABLES=y

Then make sure that you have the following Busybox options enabled:

CONFIG_IFCONFIG=y - ifconfig ifconfig
CONFIG_UDHCPC=y - udhcpc DHCP Client
CONFIG_UDHCPD=y - udhcpd DHCP Server (optional)

Finally, you'll need to choose what network connection technologies that you want available in your firmware. If using nerves_pack, you'll get support for wired Ethernet, WiFi, and USB gadget networking automatically. Otherwise, add one or more of the following to your dependency list:

vintage_net_ethernet - Standard wired Ethernet
vintage_net_wifi - Client configurations for 802.11 WiFi
vintage_net_direct - Direct connections like those used for USB gadget
vintage_net_mobile - Support for a few cellular modems

Configuration

VintageNet has many application configuration keys. Most defaults are fine. At a minimum, you'll want to specify a default configuration and default regulatory domain if using WiFi. In your main config.exs, add the following:

config :vintage_net,
  regulatory_domain: "US",
  config: [
    {"eth0", %{type: VintageNetEthernet, ipv4: %{method: :dhcp}}},
    {"wlan0", %{type: VintageNetWiFi}}
  ]

This sets the regulatory domain to the US (set to your ISO 3166-1 alpha-2 country code. This code is passed on to the drivers for WiFi and other wireless networking technologies so that they comply with local regulations. If you need a global default, set to "00" or don't set at all. Unfortunately, this may mean that an access point isn't visible if it is running on a frequency that's allowed in your country, but not globally.

The config section is a list of network configurations. The one shown above configures DHCP on wired Ethernet and minimally starts up a WiFi LAN so that it's possible to scan for networks. The typical setup is to provide generic defaults here. Static IP addresses, WiFi SSIDs and credentials are more appropriately configured at run-time. VintageNet persists configurations too. Details on network configuration are described later.

The following table describes the other application config keys.

Key	Description
config	A list of default network configurations
tmpdir	Path to a temporary directory for VintageNet
to_elixir_socket	Name to use for the Unix domain socket for C to Elixir communication
udhcpc_handler	Module for handling notifications from `udhcpc`
resolvconf	Path to `/etc/resolv.conf`
persistence	Module for persisting network configurations
persistence_dir	Path to a directory for storing persisted configurations
persistence_secret	A 16-byte secret or an MFA for getting a secret
internet_host	IP address for host to `ping` to check for Internet connectivity. Must be a tuple of integers (`{1, 1, 1, 1}`) or binary representation (`"1.1.1.1"`)
regulatory_domain	ISO 3166-1 alpha-2 country (`00` for global, `US`, etc.)

Network interface configuration

VintageNet supports several network technologies out of the box and third-party libraries can provide more via the VintageNet.Technology behaviour.

Configurations are Elixir maps. These are specified in three places:

The vintage_net application config (e.g., your config.exs)
Locally saved configuration (see the VintageNet.Persistence behaviour for replacing the default)
Calling VintageNet.configure/2 to change the configuration at run-time

When vintage_net starts, it applies saved configurations first and if any thing is wrong with those configs, it reverts to the application config. A good practice is to have safe defaults for all network interfaces in the application config.

The only required key in the configuration maps is :type. All other keys follow from the type. :type should be set to a module that implements the VintageNet.Technology behaviour. The following are common technologies:

VintageNetEthernet - Standard wired Ethernet
VintageNetWiFi - Client configurations for 802.11 WiFi
VintageNetDirect - Direct connections like those used for USB gadget connections
VintageNet.Technology.Null - An empty configuration useful for turning off a configuration

See the links above for specific documentation.

Persistence

By default, VintageNet stores network configuration to disk. If you are migrating from nerves_network you may already have a persistence implementation. To disable the default persistence, configure vintage_net as follows:

config :vintage_net,
  persistence: VintageNet.Persistence.Null

Debugging

Debugging networking issues is not fun. When you're starting out with vintage_net, it is highly recommended to connect to your target using a method that doesn't require networking to work. This could be a UART connection to an IEx console on a Nerves device or maybe just hooking up a keyboard and monitor.

If having trouble, first check VintageNet.info() to verify the configuration and connection status:

iex> VintageNet.info
VintageNet 0.3.0

All interfaces:       ["eth0", "lo", "tap0", "wlan0"]
Available interfaces: ["eth0", "wlan0"]

Interface eth0
  Type: VintageNetEthernet
  Present: true
  State: :configured
  Connection: :internet
  Configuration:
    %{ipv4: %{method: :dhcp}, type: VintageNetEthernet}

Interface wlan0
  Type: VintageNetWiFi
  Present: true
  State: :configured
  Connection: :internet
  Configuration:
    %{
      ipv4: %{method: :dhcp},
      type: VintageNetWiFi,
      wifi: %{
        key_mgmt: :wpa_psk,
        mode: :infrastructure,
        psk: "******",
        ssid: "MyLAN"
      }
    }

If you're using Toolshed, try running the following:

iex> ifconfig
lo: flags=[:up, :loopback, :running]
    inet 127.0.0.1  netmask 255.0.0.0
    inet ::1  netmask ffff:ffff:ffff:ffff:ffff:ffff:ffff:ffff
    hwaddr 00:00:00:00:00:00

eth0: flags=[:up, :broadcast, :running, :multicast]
    inet 192.168.9.131  netmask 255.255.255.0  broadcast 192.168.9.255
    inet fe80::6264:5ff:fee1:4045  netmask ffff:ffff:ffff:ffff::
    hwaddr 60:64:05:e1:40:45

wlan0: flags=[:up, :broadcast, :running, :multicast]
    inet 192.168.9.175  netmask 255.255.255.0  broadcast 192.168.9.255
    inet fe80::20c:e7ff:fe11:3d46  netmask ffff:ffff:ffff:ffff::
    hwaddr 00:0c:e7:11:3d:46

Or ping:

iex> ping "nerves-project.com"
Press enter to stop
Response from nerves-project.com (96.126.123.244): time=48.87ms
Response from nerves-project.com (96.126.123.244): time=42.856ms
Response from nerves-project.com (96.126.123.244): time=43.097ms

You can also specify an interface to use with ping:

iex> ping "nerves-project.com", ifname: "wlan0"
Press enter to stop
Response from nerves-project.com (96.126.123.244): time=57.817ms
Response from nerves-project.com (96.126.123.244): time=46.796ms

iex> ping "nerves-project.com", ifname: "eth0"
Press enter to stop
Response from nerves-project.com (96.126.123.244): time=47.923ms
Response from nerves-project.com (96.126.123.244): time=48.688ms

If it looks like nothing is working, check the logs. On Nerves devices, this is frequently done by calling RingLogger.next or RingLogger.attach.

At a last resort, please open a GitHub issue. We would be glad to help. We only have one ask and that is that you get us started with an improvement to our documentation or code so that the next person to run into the issue will have an easier time. Thanks!

Properties

VintageNet maintains a key/value store for retrieving information on networking information:

iex> VintageNet.get(["interface", "eth0", "connection"])
:internet

iex> VintageNet.get_by_prefix([])
[
  {["interface", "eth0", "connection"], :internet},
  {["interface", "eth0", "state"], :configured},
  {["interface", "eth0", "type"], VintageNetEthernet},
  {["interface", "wlan0", "connection"], :internet},
  {["interface", "wlan0", "state"], :configured},
  {["interface", "wlan0", "type"], VintageNetWiFi}
]

You can also subscribe to keys and receive a message every time it or one its child keys changes:

iex> VintageNet.subscribe(["interface", "eth0"])
:ok

iex> flush
{VintageNet, ["interface", "eth0", "state"], :configuring, :configured, %{}}

The message format is {VintageNet, name, old_value, new_value, metadata}

Global properties

Property	Values	Description
`available_interfaces`	`[eth0, ...]`	Currently available network interfaces in priority order. E.g., the first one is used by default
`connection`	`:disconnected`, `:lan`, `:internet`	The overall network connection status. This is the best status of all interfaces.

Common network interface properties

All network interface properties can be found under ["interface", ifname] in the PropertyTable. The following table lists out properties common to all interfaces:

Property	Values	Description
`type`	`VintageNetEthernet`, etc.	The type of the interface
`config`	`%{...}`	The configuration for this interface
`state`	`:configured`, `:configuring`, etc.	The state of the interface from `VintageNet`'s point of view.
`hw_path`	`"/devices/platform/ocp/4a100000.ethernet"`	This is how Linux internally views the connections going to the interface.
`connection`	`:disconnected`, `:lan`, `:internet`	This provides a determination of the Internet connection status
`lower_up`	`true` or `false`	This indicates whether the physical layer is "up". E.g., a cable is connected or WiFi associated
`mac_address`	"11:22:33:44:55:66"	The interface's MAC address as a string
`addresses`	[address_info]	This is a list of all of the addresses assigned to this interface

Specific types of interfaces provide more parameters.

Predictable network interface names

When using more than one of the same type of interface, it's possible for Linux to reorder their naming. For example, if you have two USB WiFi adapters, one will be named wlan0 and the other wlan1. Which one is first depends on things like when the adapter is found and when kernel modules are loaded. This can vary between boots and cause a lot of confusion.

The solution is to rename network interfaces based on characteristics of the interface - such as how it's connected. Then application software refers to the new name rather than names like wlan0. This is a common problem, and VintageNet provides support for automatically renaming network interfaces.

If you're used to systemd's approach to naming interfaces, be aware that VintageNet's approach is different: systemd has an algorithm for generating names (e.g., enp4s0) automatically. VintageNet requires you to provide the names to use (e.q., internet0, lan0, etc.) and how they map to hardware. If VintageNet is confronted with a network interface that is connected in a way that it doesn't know about, it will do nothing.

IMPORTANT: Do not mix and match predictable interface names and non-predictable interface names (wlan*, eth*, usb*, wwan*). It is confusing and VintageNet will fight you.

Before switching to predictable names, find out how your network interfaces are connected. For example, this device has an Ethernet interface and two USB WiFi dongles:

iex> VintageNet.match(["interface", :_, "hw_path"])
[
  {["interface", "eth0", "hw_path"], "/devices/platform/ocp/4a100000.ethernet"},
  {["interface", "lo", "hw_path"], "/devices/virtual"},
  {["interface", "wlan0", "hw_path"], "/devices/platform/ocp/47400000.usb/47401c00.usb/musb-hdrc.1/usb2/2-1/2-1:1.0"},
  {["interface", "wlan1", "hw_path"], "/devices/platform/ocp/47400000.usb/47401400.usb/musb-hdrc.0/usb1/1-1/1-1:1.4"}
]

Now update your config.exs with the mappings with the :ifnames key. Be sure to also update the default configuration with the new interface names. Continuing the example, imagine that one WiFi adapter supports 802.11 meshing and it's guaranteed to be in one USB port on the device. The other USB port can have any of a few types of USB WiFi modules. We need to use predictable naming in this case so that meshing is only setup on the adapter that supports it.

config :vintage_net,
  ifnames: [
    %{
      hw_path: "/devices/platform/ocp/4a100000.ethernet",
      ifname: "ethernet0"
    },
    %{
      hw_path: "/devices/platform/ocp/47400000.usb/47401c00.usb/musb-hdrc.1/usb2/2-1/2-1:1.0",
      ifname: "primary_wifi"
    },
    %{
      hw_path: "/devices/platform/ocp/47400000.usb/47401400.usb/musb-hdrc.0/usb1/1-1/1-1:1.4",
      ifname: "mesh_wifi"
    }
  ],
  config: [
    {"ethernet0", %{type: VintageNetEthernet}},
    {"primary_wifi", %{type: VintageNetWiFi}},
    {"mesh_wifi", %{type: VintageNetWiFi}}
  ]

IMPORTANT: VintageNet has rules about renaming interfaces to prevent confusing errors. Below is a list of reasons it will not rename an interface

hw_path matches /devices/virtual (such as lo0, ppp0 etc.)
A second interface's hw_path matches an interface that has already been renamed. This should never happen.

Power Management

Some devices require additional work to be done for them to become available. Examples of this are:

Setting a GPIO to enable power to the module
Loading a Linux kernel module that is not automatically loaded via the default mechanisms
Running usb_modeswitch to change the USB interface to the appropriate state
Performing an initialization step such as loading firmware

Similarly, when the network interface is no longer being used, it can be nice to undo any steps above.

This process is referred to as power management in VintageNet even though the implementation may not actually affect power use. To use it, implement the VintageNet.PowerManager behaviour and register the implementation in your config.exs.

Additionally, VintageNet runs a watchdog-like service for network devices that supply VintageNet.PowerManager implementations. If the watchdog is not pet within the timeout period (user-specified and defaults to 60 seconds), VintageNet powers the device off and and on. The VintageNet power management code supports mandatory minimum on and off times to prevent damage to hardware and also minimize pointless power cycling of hardware.

While many network devices are fairly reliable and powering off and on seems unnecessary, it can save a trip to the field or a full device reboot.

VintageNet.info/1 shows the power management state for network interfaces that are using this feature.

jthacker/vintage_net