Merge branch 'staging' into remove-dnsmasq

This implementes a small DNS server that can be controlled/setup by
VintageNet natively, instead of shelling out to dnsmasq. It also
by extension removes the usage of dnsmasq's dhcp server, replacing it
with dhcpcd which is built into VintageNet as well.

farmbot_os/config/target/dev.exs

@@ -10,22 +10,7 @@ config :vintage_net,
   persistence: VintageNet.Persistence.Null,
   config: [
     {"wlan0", %{type: VintageNet.Technology.Null}},
-    {"usb0",
-     %{
-       type: FarmbotOS.Platform.Target.Configurator.CaptivePortal,
-       ipv4: %{
-         method: :static,
-         address: "192.168.25.1",
-         netmask: "255.255.255.0"
-       },
-       dnsmasq: %{
-         domain: "farmbot",
-         server: "192.168.25.1",
-         address: "192.168.25.1",
-         start: "192.168.25.2",
-         end: "192.168.25.10"
-       }
-     }}
+    {"usb0", %{type: VintageNetDirect}}
   ]
 
 config :mdns_lite,

farmbot_os/config/target/prod.exs

@@ -10,22 +10,7 @@ config :vintage_net,
   persistence: VintageNet.Persistence.Null,
   config: [
     {"wlan0", %{type: VintageNet.Technology.Null}},
-    {"usb0",
-     %{
-       type: FarmbotOS.Platform.Target.Configurator.CaptivePortal,
-       ipv4: %{
-         method: :static,
-         address: "192.168.25.1",
-         netmask: "255.255.255.0"
-       },
-       dnsmasq: %{
-         domain: "farmbot",
-         server: "192.168.25.1",
-         address: "192.168.25.1",
-         start: "192.168.25.2",
-         end: "192.168.25.10"
-       }
-     }}
+    {"usb0", %{type: VintageNetDirect}}
   ]
 
 config :mdns_lite,

farmbot_os/lib/farmbot_os/configurator/captive_dns.ex

@@ -0,0 +1,79 @@
+defmodule FarmbotOS.Configurator.CaptiveDNS do
+  use GenServer
+  alias __MODULE__, as: State
+
+  defstruct [:dns_socket, :dns_port, :ifname]
+
+  def start_link(ifname, port) do
+    GenServer.start_link(__MODULE__, [ifname, port])
+  end
+
+  @impl GenServer
+  def init([ifname, port]) do
+    send(self(), :open_dns)
+    # use charlist here because :inet module works with charlists
+    {:ok, %State{dns_port: port, ifname: to_charlist(ifname)}}
+  end
+
+  @impl GenServer
+  # open a UDP socket on port 53
+  def handle_info(:open_dns, state) do
+    case :gen_udp.open(state.dns_port, [:binary, active: true, reuseaddr: true]) do
+      {:ok, socket} ->
+        {:noreply, %State{state | dns_socket: socket}}
+
+      error ->
+        {:stop, error, state}
+    end
+  end
+
+  # binary dns message from the socket
+  def handle_info(
+        {:udp, socket, ip, port, packet},
+        %{dns_socket: socket} = state
+      ) do
+    record = DNS.Record.decode(packet)
+    {answers, state} = handle_dns(record.qdlist, [], state)
+    response = DNS.Record.encode(%{record | anlist: answers})
+    _ = :gen_udp.send(socket, ip, port, response)
+    {:noreply, state}
+  end
+
+  # recursively check for dns queries, respond to each of them with the local ip address.
+
+  # respond to `a` with our current ip address
+  defp handle_dns(
+         [%{type: :a} = q | rest],
+         answers,
+         state
+       ) do
+    ifname = state.ifname
+    {:ok, interfaces} = :inet.getifaddrs()
+    {^ifname, ifinfo} = List.keyfind(interfaces, ifname, 0)
+
+    addr =
+      Enum.find_value(ifinfo, fn
+        {:addr, {_, _, _, _} = ipv4_addr} -> ipv4_addr
+        _ -> false
+      end)
+
+    answer = make_record(q.domain, q.type, 120, addr)
+    handle_dns(rest, [answer | answers], state)
+  end
+
+  # stop recursing when qdlist is fully enumerated
+  defp handle_dns([], answers, state) do
+    {Enum.reverse(answers), state}
+  end
+
+  defp make_record(domain, type, ttl, data) do
+    %DNS.Resource{
+      domain: domain,
+      class: :in,
+      type: type,
+      ttl: ttl,
+      data: data
+    }
+  end
+end
+FarmbotOS.Configurator.CaptiveDNS.start_link("lo0", 4040)

farmbot_os/mix.exs

@@ -92,6 +92,7 @@ defmodule FarmbotOS.MixProject do
       {:cors_plug, "~> 2.0"},
       {:plug_cowboy, "~> 2.1"},
       {:phoenix_html, "~> 2.13"},
+      {:dns, "~> 2.1"},
 
       # Nerves stuff.
       {:nerves, "~> 1.5", runtime: false},

farmbot_os/platform/target/configurator/captive_portal.ex

@@ -6,6 +6,7 @@ defmodule FarmbotOS.Platform.Target.Configurator.CaptivePortal do
 
   @behaviour VintageNet.Technology
   require FarmbotCore.Logger
+  alias FarmbotOS.Configurator.CaptiveDNS
 
   @impl VintageNet.Technology
   def normalize(%{vintage_net_wifi: _} = config) do
@@ -24,7 +25,7 @@ defmodule FarmbotOS.Platform.Target.Configurator.CaptivePortal do
 
     ifname
     |> vintage_wifi(normalized, opts)
-    |> dnsmasq(opts)
+    |> add_captive_dns()
   end
 
   def to_raw_config(ifname, config, opts) do
@@ -32,7 +33,7 @@ defmodule FarmbotOS.Platform.Target.Configurator.CaptivePortal do
 
     ifname
     |> vintage_ethernet(normalized, opts)
-    |> dnsmasq(opts)
+    |> add_captive_dns()
   end
 
   @impl VintageNet.Technology
@@ -45,67 +46,12 @@ defmodule FarmbotOS.Platform.Target.Configurator.CaptivePortal do
     VintageNetWiFi.ioctl(ifname, ioctl, args)
   end
 
-  defp dnsmasq(
-         %{ifname: ifname, source_config: %{dnsmasq: config}} = raw_config,
-         opts
-       ) do
-    tmpdir = Keyword.fetch!(opts, :tmpdir)
-    killall = Keyword.fetch!(opts, :bin_killall)
-    dnsmasq = System.find_executable("dnsmasq")
-    dnsmasq_conf_path = Path.join(tmpdir, "dnsmasq.conf.#{ifname}")
-    dnsmasq_lease_file = Path.join(tmpdir, "dnsmasq.leases.#{ifname}")
-    dnsmasq_pid_file = Path.join(tmpdir, "dnsmasq.pid.#{ifname}")
-
-    dnsmasq_conf_contents = """
-    interface=#{ifname}
-    except-interface=lo
-    localise-queries
-    bogus-priv
-    bind-interfaces
-    listen-address=#{config[:address]}
-    server=#{config[:address]}
-    address=/#/#{config[:address]}
-    dhcp-option=6,#{config[:address]}
-    dhcp-range=#{config[:start]},#{config[:end]},12h
-    """
-
-    files = [
-      {dnsmasq_conf_path, dnsmasq_conf_contents}
+  defp add_captive_dns(%{ifname: ifname} = raw_config) do
+    child_specs = [
+      {CaptiveDNS, [ifname, 53]}
     ]
 
-    up_cmds = [
-      {:run, dnsmasq,
-       [
-         "-K",
-         "-l",
-         dnsmasq_lease_file,
-         "-x",
-         dnsmasq_pid_file,
-         "-C",
-         dnsmasq_conf_path
-       ]}
-    ]
-
-    down_cmds = [
-      {:run, killall, ["-q", "-9", "dnsmasq"]}
-    ]
-
-    updated_raw_config = %{
-      raw_config
-      | files: raw_config.files ++ files,
-        up_cmds: raw_config.up_cmds ++ up_cmds,
-        down_cmds: raw_config.down_cmds ++ down_cmds,
-        cleanup_files:
-          raw_config.cleanup_files ++
-            [dnsmasq_conf_path, dnsmasq_lease_file, dnsmasq_pid_file]
-    }
-
-    updated_raw_config
-  end
-
-  defp dnsmasq(%{} = raw_config, _opts) do
-    FarmbotCore.Logger.error(1, "DNSMASQ Disabled")
-    raw_config
+    %{raw_config | child_specs: raw_config.child_specs ++ child_specs}
   end
 
   defp vintage_wifi(ifname, config, opts) do

farmbot_os/platform/target/network.ex

@@ -36,10 +36,7 @@ defmodule FarmbotOS.Platform.Target.Network do
         address: "192.168.24.1",
         netmask: "255.255.255.0"
       },
-      dnsmasq: %{
-        domain: "farmbot",
-        server: "192.168.24.1",
-        address: "192.168.24.1",
+      dhcpd: %{
         start: "192.168.24.2",
         end: "192.168.24.10"
       }

farmbot_os/test/farmbot_os/captive_dns_test.exs

@@ -0,0 +1,13 @@
+defmodule FarmbotOS.Configurator.CaptiveDNSTest do
+  use ExUnit.Case, async: false
+
+  @dig System.find_executable("dig")
+  if @dig do
+    test "all dns queries resolve to local ip address" do
+      {:ok, dns_server} = FarmbotOS.Configurator.CaptiveDNS.start_link("lo0", 4040)
+      res = :os.cmd('dig -p 4040')
+      refute String.contains?(to_string(res), "no servers could be reached")
+    end
+  end
+
+end