Add support for udhcpd in wifi technology

README.md

@@ -32,7 +32,7 @@ The following network configurations are supported:
 * [x] WPA2 PSK and EAP
 * [ ] USB gadget mode Ethernet, IPv4 DHCP server to supply host IP address
 * [ ] Cellular networks
-* [ ] WiFi AP mode
+* [x] WiFi AP mode
 * [ ] IPv6
 
 `VintageNet` takes a different approach to networking from `nerves_network`. It
@@ -268,8 +268,7 @@ iex> VintageNet.configure("wlan0", %{
 })
 ```
 
-Example of host mode:
-(note this will not create a DHCP server)
+Example of access point mode:
 
 ```elixir
 iex> VintageNet.configure("wlan0", %{
@@ -284,6 +283,10 @@ iex> VintageNet.configure("wlan0", %{
         address: "192.168.24.1",
         netmask: "255.255.255.0",
         gateway: "192.168.24.1"
+      },
+      dhcpd: %{
+        start: "192.168.24.2",
+        end: "192.168.24.10"
       }
 })
 ```

lib/vintage_net/ip/config_to_udhcpd.ex

@@ -0,0 +1,72 @@
+defmodule VintageNet.IP.ConfigToUdhcpd do
+  @moduledoc """
+  This is a helper module for VintageNet.Technology implementations that use
+  the udhcpd server.
+  """
+
+  @doc """
+  Convert a configuration to the contents of a /etc/udhcpd.conf file
+
+  `start` - Start of the lease block
+  `end` - End of the lease block
+  `max_leases` - The maximum number of leases
+  `decline_time` - The amount of time that an IP will be reserved (leased to nobody)
+  `conflict_time` -The amount of time that an IP will be reserved
+  `offer_time` - How long an offered address is reserved (seconds)
+  `min_lease` - If client asks for lease below this value, it will be rounded up to this value (seconds)
+  `auto_time` - The time period at which udhcpd will write out leases file.
+  `static_leases` - list of `{macaddress, ipaddress}`
+  """
+  @spec config_to_udhcpd_contents(VintageNet.ifname(), map(), Path.t()) :: String.t()
+  def config_to_udhcpd_contents(ifname, %{dhcpd: dhcpd}, tmpdir) do
+    pidfile = Path.join(tmpdir, "udhcpd.#{ifname}.pid")
+    lease_file = Path.join(tmpdir, "udhcpd.#{ifname}.leases")
+
+    initial = """
+    interface #{ifname}
+    pidfile #{pidfile}
+    lease_file #{lease_file}
+    """
+
+    config = Enum.map(dhcpd, &to_udhcpd_string/1)
+    IO.iodata_to_binary([initial, "\n", config, "\n"])
+  end
+
+  defp to_udhcpd_string({:start, val}) do
+    "start #{val}\n"
+  end
+
+  defp to_udhcpd_string({:end, val}) do
+    "end #{val}\n"
+  end
+
+  defp to_udhcpd_string({:max_leases, val}) do
+    "max_leases #{val}\n"
+  end
+
+  defp to_udhcpd_string({:decline_time, val}) do
+    "decline_time #{val}\n"
+  end
+
+  defp to_udhcpd_string({:conflict_time, val}) do
+    "conflict_time #{val}\n"
+  end
+
+  defp to_udhcpd_string({:offer_time, val}) do
+    "offer_time #{val}\n"
+  end
+
+  defp to_udhcpd_string({:min_lease, val}) do
+    "min_lease #{val}\n"
+  end
+
+  defp to_udhcpd_string({:auto_time, val}) do
+    "auto_time #{val}\n"
+  end
+
+  defp to_udhcpd_string({:static_leases, leases}) do
+    Enum.map(leases, fn {mac, ip} ->
+      "static_lease #{mac} #{ip}\n"
+    end)
+  end
+end

lib/vintage_net/technology/wifi.ex

@@ -3,7 +3,7 @@ defmodule VintageNet.Technology.WiFi do
 
   alias VintageNet.WiFi.{Scan, WPA2}
   alias VintageNet.Interface.RawConfig
-  alias VintageNet.IP.ConfigToInterfaces
+  alias VintageNet.IP.{ConfigToInterfaces, ConfigToUdhcpd}
 
   @impl true
   def to_raw_config(ifname, %{type: __MODULE__, wifi: wifi_config} = config, opts) do
@@ -35,17 +35,33 @@ defmodule VintageNet.Technology.WiFi do
       {:run, killall, ["-q", "wpa_supplicant"]}
     ]
 
-    {:ok,
-     %RawConfig{
-       ifname: ifname,
-       type: __MODULE__,
-       source_config: config,
-       files: files,
-       cleanup_files: [Path.join(control_interface_path, ifname)],
-       child_specs: [{VintageNet.Interface.ConnectivityChecker, ifname}],
-       up_cmds: up_cmds,
-       down_cmds: down_cmds
-     }}
+    case maybe_add_udhcpd(ifname, config, opts) do
+      {udhcpd_files, udhcpd_up_cmds, udhcpd_down_cmds} ->
+        {:ok,
+         %RawConfig{
+           ifname: ifname,
+           type: __MODULE__,
+           source_config: config,
+           files: files ++ udhcpd_files,
+           cleanup_files: [Path.join(control_interface_path, ifname)],
+           child_specs: [{VintageNet.Interface.ConnectivityChecker, ifname}],
+           up_cmds: up_cmds ++ udhcpd_up_cmds,
+           down_cmds: down_cmds ++ udhcpd_down_cmds
+         }}
+
+      nil ->
+        {:ok,
+         %RawConfig{
+           ifname: ifname,
+           type: __MODULE__,
+           source_config: config,
+           files: files,
+           cleanup_files: [Path.join(control_interface_path, ifname)],
+           child_specs: [{VintageNet.Interface.ConnectivityChecker, ifname}],
+           up_cmds: up_cmds,
+           down_cmds: down_cmds
+         }}
+    end
   end
 
   def to_raw_config(ifname, %{type: __MODULE__}, opts) do
@@ -84,6 +100,29 @@ defmodule VintageNet.Technology.WiFi do
     {:error, :bad_configuration}
   end
 
+  defp maybe_add_udhcpd(ifname, %{dhcpd: _dhcpd} = config, opts) do
+    tmpdir = Keyword.fetch!(opts, :tmpdir)
+    killall = Keyword.fetch!(opts, :bin_killall)
+    udhcpd = Keyword.fetch!(opts, :bin_udhcpd)
+    udhcpd_conf_path = Path.join(tmpdir, "udhcpd.conf.#{ifname}")
+
+    files = [
+      {udhcpd_conf_path, ConfigToUdhcpd.config_to_udhcpd_contents(ifname, config, tmpdir)}
+    ]
+
+    up_cmds = [
+      {:run, udhcpd, [udhcpd_conf_path]}
+    ]
+
+    down_cmds = [
+      {:run, killall, ["-q", "udhcpd"]}
+    ]
+
+    {files, up_cmds, down_cmds}
+  end
+
+  defp maybe_add_udhcpd(_, _, _), do: nil
+
   @impl true
   def ioctl(ifname, :scan, _args) do
     Scan.scan(ifname)

mix.exs

@@ -36,6 +36,7 @@ defmodule VintageNet.MixProject do
         bin_wpa_supplicant: "/usr/sbin/wpa_supplicant",
         bin_wpa_cli: "/usr/sbin/wpa_cli",
         bin_ip: "/sbin/ip",
+        bin_udhcpd: "/usr/sbin/udhcpd",
         udhcpc_handler: VintageNet.Interface.Udhcpc,
         resolvconf: "/etc/resolv.conf",
         persistence: VintageNet.Persistence.FlatFile,

test/vintage_net/ip/config_to_udhcpd_test.exs

@@ -0,0 +1,40 @@
+defmodule VintageNet.IP.ConfigToUdhcpdTest do
+  use ExUnit.Case
+  alias VintageNet.IP.ConfigToUdhcpd
+
+  test "dhcp server config" do
+    tmp_dir = "test_tmp"
+
+    input = %{
+      dhcpd: %{
+        start: "192.168.1.2",
+        end: "192.168.1.100",
+        max_leases: 98,
+        decline_time: 100,
+        conflict_time: 200,
+        offer_time: 300,
+        min_lease: 60,
+        auto_time: 60,
+        static_leases: [
+          {"00:60:08:11:CE:4E", "192.168.1.55"},
+          {"00:60:08:11:CE:3E", "192.168.1.56"}
+        ]
+      }
+    }
+
+    output = ConfigToUdhcpd.config_to_udhcpd_contents("eth0", input, tmp_dir)
+
+    assert output =~ """
+           auto_time 60
+           conflict_time 200
+           decline_time 100
+           end 192.168.1.100
+           max_leases 98
+           min_lease 60
+           offer_time 300
+           start 192.168.1.2
+           static_lease 00:60:08:11:CE:4E 192.168.1.55
+           static_lease 00:60:08:11:CE:3E 192.168.1.56
+           """
+  end
+end

test/vintage_net/technology/wifi_test.exs

@@ -1042,4 +1042,78 @@ defmodule VintageNet.Technology.WiFiTest do
 
     assert {:ok, output} == WiFi.to_raw_config("wlan0", input, default_opts())
   end
+
+  test "create a dhcpd config" do
+    input = %{
+      type: VintageNet.Technology.WiFi,
+      wifi: %{
+        ssid: "example ap",
+        key_mgmt: :none,
+        mode: :host
+      },
+      ipv4: %{
+        method: :static,
+        address: "192.168.24.1",
+        netmask: "255.255.255.0",
+        gateway: "192.168.24.1"
+      },
+      dhcpd: %{
+        start: "192.168.24.2",
+        end: "192.168.24.100"
+      },
+      hostname: "unit_test"
+    }
+
+    output = %RawConfig{
+      ifname: "wlan0",
+      type: VintageNet.Technology.WiFi,
+      source_config: input,
+      child_specs: [{VintageNet.Interface.ConnectivityChecker, "wlan0"}],
+      files: [
+        {"/tmp/vintage_net/network_interfaces.wlan0",
+         """
+         iface wlan0 inet static
+           address 192.168.24.1
+           gateway 192.168.24.1
+           netmask 255.255.255.0
+           hostname unit_test
+         """},
+        {"/tmp/vintage_net/wpa_supplicant.conf.wlan0",
+         """
+         ctrl_interface=/tmp/vintage_net/wpa_supplicant
+         country=00
+         network={
+         ssid="example ap"
+         key_mgmt=NONE
+         mode=2
+         }
+         """},
+        {"/tmp/vintage_net/udhcpd.conf.wlan0",
+         """
+         interface wlan0
+         pidfile /tmp/vintage_net/udhcpd.wlan0.pid
+         lease_file /tmp/vintage_net/udhcpd.wlan0.leases
+
+         end 192.168.24.100
+         start 192.168.24.2
+
+         """}
+      ],
+      up_cmds: [
+        {:run_ignore_errors, "/usr/bin/killall", ["-q", "wpa_supplicant"]},
+        {:run, "/usr/sbin/wpa_supplicant",
+         ["-B", "-i", "wlan0", "-c", "/tmp/vintage_net/wpa_supplicant.conf.wlan0", "-dd"]},
+        {:run, "/sbin/ifup", ["-i", "/tmp/vintage_net/network_interfaces.wlan0", "wlan0"]},
+        {:run, "/usr/sbin/udhcpd", ["/tmp/vintage_net/udhcpd.conf.wlan0"]}
+      ],
+      down_cmds: [
+        {:run, "/sbin/ifdown", ["-i", "/tmp/vintage_net/network_interfaces.wlan0", "wlan0"]},
+        {:run, "/usr/bin/killall", ["-q", "wpa_supplicant"]},
+        {:run, "/usr/bin/killall", ["-q", "udhcpd"]}
+      ],
+      cleanup_files: ["/tmp/vintage_net/wpa_supplicant/wlan0"]
+    }
+
+    assert {:ok, output} == WiFi.to_raw_config("wlan0", input, default_opts())
+  end
 end