Support changing the subnet from 192.168.0.0

The default 192.168.0.0 network works well for the wizard's IP addresses
and is easy to remember. There's confusion, though, when devices have
WiFi adapters that can run in both AP and station mode at the same time.
During the test step of connecting to an AP, if the network being tested
is also on the 192.168.0.0 subnet, then there will be two 192.168.0.0
networks. To minimize the chance of this, it's now possible to set the
subnet to something very unlikely to see.

This isn't the default since changing the default would invalidate
configuration instructions for people using the wizard in their
projects.

Author: fhunleth

README.md

@@ -111,12 +111,13 @@ Each configuration option is optional and will fall back to
 ### DNS in AP-mode
 
 When the wizard is running, users go to either `http://192.168.0.1/` or
-`http://wifi.config/` to access the web user interface. The latter can be
+`http://wifi.config/` to access the web user interface. Both can be
 changed via the `config.exs`:
 
 ```elixir
 config :vintage_net_wizard,
-  dns_name: "my-wifi-config.com"
+  dns_name: "my-wifi-config.com",
+  subnet: "192.168.0.0"
 ```
 
 ### Port

lib/vintage_net_wizard/ap_mode.ex

@@ -4,16 +4,22 @@ defmodule VintageNetWizard.APMode do
   """
 
   @default_hostname "vintage_net_wizard"
+  @default_dns_name "wifi.config"
+  @default_subnet {192, 168, 0, 0}
 
   @doc """
   Change the WiFi module into access point mode
   """
   @spec into_ap_mode(VintageNet.ifname()) :: :ok | {:error, any()}
   def into_ap_mode(ifname) do
     hostname = get_hostname()
-    our_name = Application.get_env(:vintage_net_wizard, :dns_name, "wifi.config")
+    our_name = Application.get_env(:vintage_net_wizard, :dns_name, @default_dns_name)
 
-    config = ap_mode_configuration(hostname, our_name)
+    subnet =
+      Application.get_env(:vintage_net_wizard, :subnet, @default_subnet)
+      |> VintageNet.IP.ip_to_tuple!()
+
+    config = ap_mode_configuration(hostname, our_name, subnet)
     VintageNet.configure(ifname, config, persist: false)
   end
 
@@ -34,13 +40,26 @@ defmodule VintageNetWizard.APMode do
     VintageNet.configure(ifname, no_ap_mode)
   end
 
+  defp create_ip_24(subnet, host) when host > 0 and host < 255 do
+    {a, b, c, _} = subnet
+    {a, b, c, host}
+  end
+
   @doc """
   Return a configuration to put VintageNet into AP mode
+
+  * `hostname` - the device's hostname which will be modified to be the AP's SSID
+  * `our_name` - the name for clients to use when connecting to the wizard if
+                 not using the IP address.
+  * `class_c_subnet` - A class C subnet to use for all of the IP addresses on
+                 this network.
   """
-  @spec ap_mode_configuration(String.t(), String.t()) :: map()
-  def ap_mode_configuration(hostname, our_name) do
+  @spec ap_mode_configuration(String.t(), String.t(), :inet.ip4_address()) :: map()
+  def ap_mode_configuration(hostname, our_name, class_c_subnet) do
     ssid = sanitize_hostname_for_ssid(hostname)
-    our_ip_address = {192, 168, 0, 1}
+
+    subnet_mask = VintageNet.IP.prefix_length_to_subnet_mask(:inet, 24)
+    our_ip_address = create_ip_24(class_c_subnet, 1)
 
     %{
       type: VintageNetWiFi,
@@ -59,13 +78,12 @@ defmodule VintageNetWizard.APMode do
         prefix_length: 24
       },
       dhcpd: %{
-        # These are defaults and are reproduced here as documentation
-        start: {192, 168, 0, 20},
-        end: {192, 168, 0, 254},
+        start: create_ip_24(class_c_subnet, 20),
+        end: create_ip_24(class_c_subnet, 254),
         max_leases: 235,
         options: %{
           dns: [our_ip_address],
-          subnet: {255, 255, 255, 0},
+          subnet: subnet_mask,
           router: [our_ip_address],
           domain: our_name,
           search: [our_name]

test/vintage_net_wizard/ap_mode_test.exs

@@ -4,7 +4,7 @@ defmodule VintageNetWizard.APModeTest do
   alias VintageNetWizard.APMode
 
   test "AP mode configuration has expected content" do
-    config = APMode.ap_mode_configuration("hostname", "our_name")
+    config = APMode.ap_mode_configuration("hostname", "our_name", {192, 168, 0, 0})
 
     expected = %{
       type: VintageNetWiFi,
@@ -29,18 +29,48 @@ defmodule VintageNetWizard.APModeTest do
   end
 
   test "empty hostname gets changed to a valid ssid" do
-    config = APMode.ap_mode_configuration("", "our_name")
+    config = APMode.ap_mode_configuration("", "our_name", {192, 168, 0, 0})
 
     %{vintage_net_wifi: %{networks: [%{ssid: ssid}]}} = config
 
     assert ssid == "vintage_net_wizard"
   end
 
   test "long hostname gets trimmed" do
-    config = APMode.ap_mode_configuration("1234567890123456789012345678901234567890", "our_name")
+    config =
+      APMode.ap_mode_configuration(
+        "1234567890123456789012345678901234567890",
+        "our_name",
+        {192, 168, 0, 0}
+      )
 
     %{vintage_net_wifi: %{networks: [%{ssid: ssid}]}} = config
 
     assert byte_size(ssid) <= 32
   end
+
+  test "AP mode configuration on custom subnet" do
+    config = APMode.ap_mode_configuration("hostname", "our_name", {10, 20, 30, 0})
+
+    expected = %{
+      type: VintageNetWiFi,
+      ipv4: %{address: {10, 20, 30, 1}, method: :static, prefix_length: 24},
+      vintage_net_wifi: %{networks: [%{key_mgmt: :none, mode: :ap, ssid: "hostname"}]},
+      dhcpd: %{
+        end: {10, 20, 30, 254},
+        max_leases: 235,
+        options: %{
+          dns: [{10, 20, 30, 1}],
+          domain: "our_name",
+          router: [{10, 20, 30, 1}],
+          search: ["our_name"],
+          subnet: {255, 255, 255, 0}
+        },
+        start: {10, 20, 30, 20}
+      },
+      dnsd: %{records: [{"our_name", {10, 20, 30, 1}}]}
+    }
+
+    assert expected == config
+  end
 end