Restrict enrichment enqueue to T-Mobile CGNAT subnet (172.56.0.0/13)

Store remote_ip in session, check subnet in LiveView mount before
enqueuing weather/HRRR/terrain/solar enrichment jobs.

lib/microwaveprop_web/live/contact_live/show.ex

@@ -18,10 +18,14 @@ defmodule MicrowavepropWeb.ContactLive.Show do
   require Logger
 
   @earth_radius_m 6_371_000.0
+  # T-Mobile CGNAT range — only enqueue enrichment jobs from this subnet
+  @enqueue_subnet {172, 56, 0, 0}
+  @enqueue_mask 13
 
   @impl true
-  def mount(%{"id" => id}, _session, socket) do
+  def mount(%{"id" => id}, session, socket) do
     contact = id |> Radio.get_contact!() |> Radio.ensure_positions!()
+    can_enqueue = internal_network?(session)
 
     if connected?(socket) do
       Phoenix.PubSub.subscribe(Microwaveprop.PubSub, "contact_enrichment:#{contact.id}")
@@ -31,13 +35,16 @@ defmodule MicrowavepropWeb.ContactLive.Show do
     end
 
     weather = load_weather(contact)
-    solar = maybe_enqueue_solar(contact)
+    solar = if can_enqueue, do: maybe_enqueue_solar(contact), else: load_solar(contact)
     hrrr_path = Weather.hrrr_profiles_for_path(contact)
     hrrr = List.first(hrrr_path)
-    {hrrr, contact} = maybe_enqueue_hrrr(hrrr, contact)
+
+    {hrrr, contact} =
+      if can_enqueue, do: maybe_enqueue_hrrr(hrrr, contact), else: {hrrr, contact}
+
     terrain = Terrain.get_terrain_profile(contact.id)
-    contact = maybe_enqueue_terrain(terrain, contact)
-    contact = maybe_enqueue_weather(weather, contact)
+    contact = if can_enqueue, do: maybe_enqueue_terrain(terrain, contact), else: contact
+    contact = if can_enqueue, do: maybe_enqueue_weather(weather, contact), else: contact
     iemre = load_iemre(contact)
     elevation_profile = compute_elevation_profile(contact, hrrr_path, weather.soundings)
     propagation_analysis = build_propagation_analysis(contact, hrrr, terrain, elevation_profile, weather.soundings)
@@ -389,6 +396,26 @@ defmodule MicrowavepropWeb.ContactLive.Show do
     |> Map.new()
   end
 
+  defp internal_network?(session) do
+    case session["remote_ip"] do
+      nil ->
+        false
+
+      ip_str ->
+        case :inet.parse_address(String.to_charlist(ip_str)) do
+          {:ok, {a, b, c, d}} ->
+            ip_int = Bitwise.bsl(a, 24) + Bitwise.bsl(b, 16) + Bitwise.bsl(c, 8) + d
+            {sa, sb, sc, sd} = @enqueue_subnet
+            subnet_int = Bitwise.bsl(sa, 24) + Bitwise.bsl(sb, 16) + Bitwise.bsl(sc, 8) + sd
+            mask = Bitwise.bsl(0xFFFFFFFF, 32 - @enqueue_mask)
+            Bitwise.band(ip_int, mask) == Bitwise.band(subnet_int, mask)
+
+          _ ->
+            false
+        end
+    end
+  end
+
   defp load_solar(contact) do
     contact.qso_timestamp
     |> DateTime.to_date()

lib/microwaveprop_web/router.ex

@@ -4,12 +4,18 @@ defmodule MicrowavepropWeb.Router do
   pipeline :browser do
     plug :accepts, ["html"]
     plug :fetch_session
+    plug :store_remote_ip
     plug :fetch_live_flash
     plug :put_root_layout, html: {MicrowavepropWeb.Layouts, :root}
     plug :protect_from_forgery
     plug :put_secure_browser_headers
   end
 
+  defp store_remote_ip(conn, _opts) do
+    ip_str = conn.remote_ip |> :inet.ntoa() |> to_string()
+    Plug.Conn.put_session(conn, :remote_ip, ip_str)
+  end
+
   pipeline :api do
     plug :accepts, ["json"]
   end