Add frequency to WiFi parameters

This is needed for the `:ibss` mode so that the first one on the network
can choose a channel.

README.md

@@ -287,6 +287,8 @@ The `:wifi` key has the following common fields:
   * `:scan_ssid` - Scan with SSID-specific Probe Request frames (this can be
     used to find APs that do not accept broadcast SSID or use multiple SSIDs;
     this will add latency to scanning, so enable this only when needed)
+  * `:frequency` - When in `:ibss` mode, use this channel frequency (in MHz).
+    For example, specify 2412 for channel 1.
 
 See the [official
 docs](https://w1.fi/cgit/hostap/plain/wpa_supplicant/wpa_supplicant.conf) for

lib/vintage_net/technology/wifi.ex

@@ -17,7 +17,8 @@ defmodule VintageNet.Technology.WiFi do
     :bssid_whitelist,
     :bssid_blacklist,
     :priority,
-    :scan_ssid
+    :scan_ssid,
+    :frequency
   ]
 
   @moduledoc """
@@ -340,6 +341,7 @@ defmodule VintageNet.Technology.WiFi do
       into_config_string(wifi, :bssid_blacklist),
       into_config_string(wifi, :wps_disabled),
       into_config_string(wifi, :mode),
+      into_config_string(wifi, :frequency),
 
       # WPA-PSK settings
       into_config_string(wifi, :psk),
@@ -444,6 +446,10 @@ defmodule VintageNet.Technology.WiFi do
     "priority=#{value}"
   end
 
+  defp wifi_opt_to_config_string(_wifi, :frequency, value) do
+    "frequency=#{value}"
+  end
+
   defp wifi_opt_to_config_string(_wifi, :identity, value) do
     "identity=#{inspect(value)}"
   end

test/vintage_net/technology/wifi_test.exs

@@ -1687,7 +1687,8 @@ defmodule VintageNet.Technology.WiFiTest do
           %{
             mode: :ibss,
             ssid: "my_mesh",
-            key_mgmt: :none
+            key_mgmt: :none,
+            frequency: 2412
           }
         ]
       },
@@ -1725,6 +1726,7 @@ defmodule VintageNet.Technology.WiFiTest do
          ssid="my_mesh"
          key_mgmt=NONE
          mode=1
+         frequency=2412
          }
          """}
       ],