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Elevate DHCP options to their own module
This is a large change that removes the use of unmodified string maps for representing DHCP options. Now that DHCP options are intentionally part of the public interface, the keys used are now atoms with values that have documented types. Additionally, this makes some functions and modules involved with DHCP options more obviously private. They need to be public to be easily tested, but they may change in the future.
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,181 @@ | ||
| defmodule VintageNet.DHCP.Options do | ||
| @moduledoc """ | ||
| DHCP Options | ||
| """ | ||
|
|
||
| alias VintageNet.IP | ||
| require Logger | ||
|
|
||
| @typedoc """ | ||
| A map of options and other information reported by udhcpc | ||
| Here's an example: | ||
| ```elixir | ||
| %{ | ||
| broadcast: {192, 168, 7, 255}, | ||
| dns: {192, 168, 7, 1}, | ||
| domain: "hunleth.lan", | ||
| hostname: "nerves-9780", | ||
| ip: {192, 168, 7, 190}, | ||
| lease: 86400, | ||
| mask: 24, | ||
| router: {192, 168, 7, 1}, | ||
| serverid: {192, 168, 7, 1}, | ||
| siaddr: {192, 168, 7, 1}, | ||
| subnet: {255, 255, 255, 0} | ||
| } | ||
| ``` | ||
| """ | ||
| @type t() :: %{ | ||
| optional(:ip) => :inet.ip_address(), | ||
| optional(:mask) => non_neg_integer(), | ||
| optional(:siaddr) => :inet.ip_address(), | ||
| optional(:subnet) => :inet.ip_address(), | ||
| optional(:timezone) => String.t(), | ||
| optional(:router) => [:inet.ip_address()], | ||
| optional(:dns) => [:inet.ip_address()], | ||
| optional(:lprsrv) => [:inet.ip_address()], | ||
| optional(:hostname) => String.t(), | ||
| optional(:bootsize) => String.t(), | ||
| optional(:domain) => String.t(), | ||
| optional(:swapsrv) => :inet.ip_address(), | ||
| optional(:rootpath) => String.t(), | ||
| optional(:ipttl) => non_neg_integer(), | ||
| optional(:mtu) => non_neg_integer(), | ||
| optional(:broadcast) => :inet.ip_address(), | ||
| optional(:routes) => [:inet.ip_address()], | ||
| optional(:nisdomain) => String.t(), | ||
| optional(:nissrv) => [:inet.ip_address()], | ||
| optional(:ntpsrv) => [:inet.ip_address()], | ||
| optional(:wins) => String.t(), | ||
| optional(:lease) => non_neg_integer(), | ||
| optional(:serverid) => :inet.ip_address(), | ||
| optional(:message) => String.t(), | ||
| optional(:renewal_time) => non_neg_integer(), | ||
| optional(:rebind_time) => non_neg_integer(), | ||
| optional(:vendor) => String.t(), | ||
| optional(:tftp) => String.t(), | ||
| optional(:bootfile) => String.t(), | ||
| optional(:userclass) => String.t(), | ||
| optional(:tzstr) => String.t(), | ||
| optional(:tzdbstr) => String.t(), | ||
| optional(:search) => String.t(), | ||
| optional(:sipsrv) => String.t(), | ||
| optional(:staticroutes) => [:inet.ip_address()], | ||
| optional(:vlanid) => String.t(), | ||
| optional(:vlanpriority) => non_neg_integer(), | ||
| optional(:pxeconffile) => String.t(), | ||
| optional(:pxepathprefix) => String.t(), | ||
| optional(:reboottime) => String.t(), | ||
| optional(:ip6rd) => String.t(), | ||
| optional(:msstaticroutes) => String.t(), | ||
| optional(:wpad) => String.t() | ||
| } | ||
|
|
||
| # Extract and translate udhcpc environment variables to DHCP options | ||
| @doc false | ||
| @spec udhcpc_to_options(%{String.t() => String.t()}) :: t() | ||
| def udhcpc_to_options(info) do | ||
| info | ||
| |> Map.new(&transform_udhcpc_option/1) | ||
| |> Map.delete(:discard) | ||
| end | ||
|
|
||
| # udhcpc passes DHCP options via environment variables and there's a lot of noise. | ||
| # Transform known keys to atoms and mark unknown or unsupported ones as `:discard` | ||
| defp transform_udhcpc_option({k, v}) do | ||
| # See https://elixir.bootlin.com/busybox/1.35.0/source/networking/udhcp/common.c#L97 | ||
| # See https://www.rfc-editor.org/rfc/rfc2132 for descriptions | ||
| udhcpc_option_map = %{ | ||
| # DHCP fields | ||
| "ip" => {:ip, &IP.ip_to_tuple/1}, | ||
| "mask" => {:mask, &parse_int/1}, | ||
| "siaddr" => {:siaddr, &IP.ip_to_tuple/1}, | ||
| # DHCP options | ||
| "subnet" => {:subnet, &IP.ip_to_tuple/1}, | ||
| "timezone" => {:timezone, &identity/1}, | ||
| "router" => {:router, &parse_ip_list/1}, | ||
| # "opt4" => :timesrv, | ||
| # "opt5" => :namesrv, | ||
| "dns" => {:dns, &parse_ip_list/1}, | ||
| # "opt7" => :logsrv, | ||
| # "opt8" => :cookiesrv, | ||
| "lprsrv" => {:lprsrv, &parse_ip_list/1}, | ||
| "hostname" => {:hostname, &identity/1}, | ||
| "bootsize" => {:bootsize, &identity/1}, | ||
| "domain" => {:domain, &identity/1}, | ||
| "swapsrv" => {:swapsrv, &IP.ip_to_tuple/1}, | ||
| "rootpath" => {:rootpath, &identity/1}, | ||
| "ipttl" => {:ipttl, &parse_int/1}, | ||
| "mtu" => {:mtu, &parse_int/1}, | ||
| "broadcast" => {:broadcast, &IP.ip_to_tuple/1}, | ||
| "routes" => {:routes, &parse_ip_list/1}, | ||
| "nisdomain" => {:nisdomain, &identity/1}, | ||
| "nissrv" => {:nissrv, &parse_ip_list/1}, | ||
| "ntpsrv" => {:ntpsrv, &parse_ip_list/1}, | ||
| "wins" => {:wins, &identity/1}, | ||
| "lease" => {:lease, &parse_int/1}, | ||
| "serverid" => {:serverid, &IP.ip_to_tuple/1}, | ||
| "message" => {:message, &identity/1}, | ||
| "opt58" => {:renewal_time, &parse_hex/1}, | ||
| "opt59" => {:rebind_time, &parse_hex/1}, | ||
| "vendor" => {:vendor, &identity/1}, | ||
| "tftp" => {:tftp, &identity/1}, | ||
| "bootfile" => {:bootfile, &identity/1}, | ||
| "opt77" => {:userclass, &identity/1}, | ||
| "tzstr" => {:tzstr, &identity/1}, | ||
| "tzdbstr" => {:tzdbstr, &identity/1}, | ||
| "search" => {:search, &identity/1}, | ||
| "sipsrv" => {:sipsrv, &identity/1}, | ||
| "staticroutes" => {:staticroutes, &parse_ip_list/1}, | ||
| "vlanid" => {:vlanid, &identity/1}, | ||
| "vlanpriority" => {:vlanpriority, &parse_int/1}, | ||
| "pxeconffile" => {:pxeconffile, &identity/1}, | ||
| "pxepathprefix" => {:pxepathprefix, &identity/1}, | ||
| "reboottime" => {:reboottime, &identity/1}, | ||
| "ip6rd" => {:ip6rd, &identity/1}, | ||
| "msstaticroutes" => {:msstaticroutes, &identity/1}, | ||
| "wpad" => {:wpad, &identity/1} | ||
| # opt50 is used to request a client IP and used internally by udhcpc, so skip. | ||
| # opt53 is the message type, so it's not an option | ||
| # opt57 is the max message length, so it's not an option | ||
| # See https://elixir.bootlin.com/busybox/1.35.0/source/networking/udhcp/common.c#L83 | ||
| } | ||
|
|
||
| with {:ok, {key, parser}} <- Map.fetch(udhcpc_option_map, k), | ||
| {:ok, result} <- parser.(v) do | ||
| {key, result} | ||
| else | ||
| _error -> {:discard, nil} | ||
| end | ||
| end | ||
|
|
||
| defp summarize_ok_tuples(ok_tuples, results \\ []) | ||
| defp summarize_ok_tuples([], results), do: {:ok, Enum.reverse(results)} | ||
| defp summarize_ok_tuples([{:ok, v} | rest], acc), do: summarize_ok_tuples(rest, [v | acc]) | ||
| defp summarize_ok_tuples([{:error, _} = error | _rest], _), do: error | ||
|
|
||
| defp parse_ip_list(str) do | ||
| str | ||
| |> String.split(" ", trim: true) | ||
| |> Enum.map(&IP.ip_to_tuple/1) | ||
| |> summarize_ok_tuples() | ||
| end | ||
|
|
||
| defp parse_int(str) do | ||
| case Integer.parse(str) do | ||
| {v, ""} -> {:ok, v} | ||
| _ -> {:error, "Expecting integer, got #{str}."} | ||
| end | ||
| end | ||
|
|
||
| defp parse_hex(str) do | ||
| case Integer.parse(str, 16) do | ||
| {v, ""} -> {:ok, v} | ||
| _ -> {:error, "Expecting hex, got #{str}."} | ||
| end | ||
| end | ||
|
|
||
| defp identity(str), do: {:ok, str} | ||
| end |
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