Bind firmware downloads to active network interface

lib/peridiod/binary/downloader.ex

@@ -24,6 +24,7 @@ defmodule Peridiod.Binary.Downloader do
     Downloader.VerifyConfig
   }
 
+  alias Peridiod.Cloud.NetworkMonitor
   alias Peridiod.LogSanitizer
 
   require Logger
@@ -612,7 +613,12 @@ defmodule Peridiod.Binary.Downloader do
     # like this. There may be a better way to do this..
     path = if query, do: "#{path}?#{query}", else: path
 
-    with {:ok, conn} <- Mint.HTTP.connect(String.to_existing_atom(scheme), host, port),
+    transport_opts = bound_interface_transport_opts()
+
+    with {:ok, conn} <-
+           Mint.HTTP.connect(String.to_existing_atom(scheme), host, port,
+             transport_opts: transport_opts
+           ),
          {:ok, conn, request_ref} <- Mint.HTTP.request(conn, "GET", path, request_headers, nil) do
       {:ok,
        %Downloader{
@@ -657,4 +663,16 @@ defmodule Peridiod.Binary.Downloader do
 
   defp add_user_agent_header(headers, _),
     do: [{"User-Agent", "Peridiod/#{Application.spec(:peridiod)[:vsn]}"} | headers]
+
+  @doc false
+  def bound_interface_transport_opts do
+    try do
+      case NetworkMonitor.get_bound_interface() do
+        nil -> []
+        ifname -> [bind_to_device: ifname]
+      end
+    catch
+      :exit, _ -> []
+    end
+  end
 end

test/peridiod/binary/downloader_test.exs

@@ -3,6 +3,7 @@ defmodule Peridiod.Binary.DownloaderTest do
   alias Peridiod.Binary.Downloader
   alias Peridiod.Binary.Downloader.RetryConfig
   alias Peridiod.Binary.Downloader.VerifyConfig
+  alias Peridiod.Cloud.NetworkMonitor
 
   # SHA-256 of test/fixtures/binaries/1M.bin
   @bin_1m_hash Base.decode16!("a073ad730e540107fbb92ee48baab97c9bc16105333a42b15a53bcc183f6f5c2",
@@ -280,4 +281,35 @@ defmodule Peridiod.Binary.DownloaderTest do
       assert_receive {:DOWN, ^ref, :process, ^pid, :normal}, 2000
     end
   end
+
+  describe "interface binding" do
+    test "returns empty transport opts when no interface is bound" do
+      # NetworkMonitor starts with bound_interface: nil in the test environment
+      assert NetworkMonitor.get_bound_interface() == nil
+      assert Downloader.bound_interface_transport_opts() == []
+    end
+
+    test "returns bind_to_device transport opt for the currently bound interface" do
+      original = :sys.get_state(NetworkMonitor)
+
+      on_exit(fn ->
+        :sys.replace_state(NetworkMonitor, fn _ -> original end)
+      end)
+
+      :sys.replace_state(NetworkMonitor, fn state ->
+        %{state | bound_interface: {"eth0", %NetworkMonitor.InterfaceInfo{}}}
+      end)
+
+      assert Downloader.bound_interface_transport_opts() == [bind_to_device: "eth0"]
+    end
+
+    test "returns empty transport opts when NetworkMonitor is not running" do
+      pid = Process.whereis(NetworkMonitor)
+      ref = Process.monitor(pid)
+      Process.exit(pid, :kill)
+      assert_receive {:DOWN, ^ref, :process, ^pid, :killed}
+
+      assert Downloader.bound_interface_transport_opts() == []
+    end
+  end
 end