From 40bcda1d74386ee361d7039d75e3ab1e57e78536 Mon Sep 17 00:00:00 2001
From: Kevin Schweikert <54439512+kevinschweikert@users.noreply.github.com>
Date: Wed, 11 Sep 2024 03:44:21 +0200
Subject: [PATCH] Unset remaining ifaces when using `MdnsLite.InetMonitor`
 (#158)

---
 lib/mdns_lite/core_monitor.ex        | 15 +++++++++++++++
 lib/mdns_lite/inet_monitor.ex        | 10 +++++++++-
 test/mdns_lite/core_monitor_test.exs | 19 +++++++++++++++++++
 3 files changed, 43 insertions(+), 1 deletion(-)

diff --git a/lib/mdns_lite/core_monitor.ex b/lib/mdns_lite/core_monitor.ex
index d0250ea..35c9602 100644
--- a/lib/mdns_lite/core_monitor.ex
+++ b/lib/mdns_lite/core_monitor.ex
@@ -65,6 +65,21 @@ defmodule MdnsLite.CoreMonitor do
     %{state | todo: []}
   end
 
+  @spec unset_remaining_ifnames(state(), [String.t()]) :: state()
+  def unset_remaining_ifnames(state, new_ifnames) do
+    Enum.reduce(known_ifnames(state), state, fn ifname, state ->
+      if ifname in new_ifnames do
+        state
+      else
+        set_ip_list(state, ifname, [])
+      end
+    end)
+  end
+
+  defp known_ifnames(state) do
+    Map.keys(state.ip_list)
+  end
+
   defp compute_delta(old_list, new_list) do
     {old_list -- new_list, new_list -- old_list}
   end
diff --git a/lib/mdns_lite/inet_monitor.ex b/lib/mdns_lite/inet_monitor.ex
index ccbdd76..746cfcf 100644
--- a/lib/mdns_lite/inet_monitor.ex
+++ b/lib/mdns_lite/inet_monitor.ex
@@ -36,10 +36,14 @@ defmodule MdnsLite.InetMonitor do
   end
 
   defp update(state) do
-    get_all_ip_addrs()
+    ifname_addresses = get_all_ip_addrs()
+    ifnames = only_ifnames(ifname_addresses)
+
+    ifname_addresses
     |> Enum.reduce(state, fn {ifname, ip_list}, state ->
       CoreMonitor.set_ip_list(state, ifname, ip_list)
     end)
+    |> CoreMonitor.unset_remaining_ifnames(ifnames)
     |> CoreMonitor.flush_todo_list()
   end
 
@@ -57,4 +61,8 @@ defmodule MdnsLite.InetMonitor do
     addrs = for addr <- Keyword.get_values(info, :addr), do: addr
     {to_string(ifname), addrs}
   end
+
+  defp only_ifnames(ifname_addresses) do
+    Enum.map(ifname_addresses, &elem(&1, 0)) |> Enum.uniq()
+  end
 end
diff --git a/test/mdns_lite/core_monitor_test.exs b/test/mdns_lite/core_monitor_test.exs
index 1b184e7..5c4cf33 100644
--- a/test/mdns_lite/core_monitor_test.exs
+++ b/test/mdns_lite/core_monitor_test.exs
@@ -68,4 +68,23 @@ defmodule MdnsLite.CoreMonitorTest do
              {MdnsLite.ResponderSupervisor, :start_child, ["eth0", {1, 2, 3, 4, 5, 6, 7, 8}]}
            ]
   end
+
+  test "remove unset ifnames" do
+    state =
+      CoreMonitor.init([])
+      |> CoreMonitor.set_ip_list("eth0", [{1, 2, 3, 4}, {1, 2, 3, 4, 5, 6, 7, 8}])
+      |> CoreMonitor.set_ip_list("wlan0", [{10, 11, 12, 13}, {14, 15, 16, 17}])
+      |> CoreMonitor.flush_todo_list()
+
+    state =
+      state
+      |> CoreMonitor.set_ip_list("wlan0", [{10, 11, 12, 13}])
+      |> CoreMonitor.unset_remaining_ifnames(["wlan0"])
+
+    # IPv4 filtering is on by default
+    assert state.todo == [
+             {MdnsLite.ResponderSupervisor, :stop_child, ["wlan0", {14, 15, 16, 17}]},
+             {MdnsLite.ResponderSupervisor, :stop_child, ["eth0", {1, 2, 3, 4}]}
+           ]
+  end
 end