From d92e5bff254d725472341156f59b9753cd2f685c Mon Sep 17 00:00:00 2001
From: Justin Schneck <j.schneck@peridio.com>
Date: Wed, 3 Jul 2024 15:22:49 -0400
Subject: [PATCH] reserve in use tunnel interface ips

---
 lib/peridio/rat/network.ex      | 13 ++++++++++++-
 lib/peridio/rat/network/cidr.ex |  2 +-
 lib/peridio/rat/tunnel.ex       |  8 ++++++++
 3 files changed, 21 insertions(+), 2 deletions(-)

diff --git a/lib/peridio/rat/network.ex b/lib/peridio/rat/network.ex
index 94f95b4..ae9886b 100644
--- a/lib/peridio/rat/network.ex
+++ b/lib/peridio/rat/network.ex
@@ -1,4 +1,5 @@
 defmodule Peridio.RAT.Network do
+  alias Peridio.RAT.Tunnel
   alias Peridio.RAT.Network.CIDR
 
   # RFC 1918 - Private Address Space
@@ -46,7 +47,7 @@ defmodule Peridio.RAT.Network do
     case :inet.getifaddrs() do
       {:ok, addrs} ->
         resp =
-          Enum.reduce(addrs, [], fn inets_interface, acc ->
+          Enum.reduce(addrs, tunnel_interface_cidrs(), fn inets_interface, acc ->
             case CIDR.from_inets_interface(inets_interface) do
               {:ok, cidr} -> [cidr | acc]
               _e -> acc
@@ -60,6 +61,16 @@ defmodule Peridio.RAT.Network do
     end
   end
 
+  def tunnel_interface_cidrs() do
+    Peridio.RAT.DynamicSupervisor
+    |> DynamicSupervisor.which_children()
+    |> Enum.map(&elem(&1, 1))
+    |> Enum.map(&Tunnel.get_state/1)
+    |> Enum.map(& &1.interface.ip_address.address)
+    |> Enum.map(&CIDR.from_ip_range(&1..&1))
+    |> List.flatten()
+  end
+
   def reserved_ports(port_start..port_end//_) do
     case System.cmd("ss", [
            "-tauH",
diff --git a/lib/peridio/rat/network/cidr.ex b/lib/peridio/rat/network/cidr.ex
index dc6e8d9..6d4c2bd 100644
--- a/lib/peridio/rat/network/cidr.ex
+++ b/lib/peridio/rat/network/cidr.ex
@@ -76,7 +76,7 @@ defmodule Peridio.RAT.Network.CIDR do
   end
 
   def from_ip_range(_, acc \\ [])
-  def from_ip_range(s_ip..s_ip//_ = range, _), do: [do_from_ip_range(range)]
+  def from_ip_range(s_ip..e_ip//_ = range, []) when s_ip == e_ip, do: [do_from_ip_range(range)]
   def from_ip_range(s_ip..e_ip//_, acc) when s_ip >= e_ip, do: acc
 
   def from_ip_range(_ip_start..ip_end//_ = range, acc) do
diff --git a/lib/peridio/rat/tunnel.ex b/lib/peridio/rat/tunnel.ex
index fff2c29..21a217d 100644
--- a/lib/peridio/rat/tunnel.ex
+++ b/lib/peridio/rat/tunnel.ex
@@ -84,6 +84,10 @@ defmodule Peridio.RAT.Tunnel do
     }
   end
 
+  def get_state(pid) do
+    GenServer.call(pid, :get_state)
+  end
+
   def start_link(%State{} = state) do
     GenServer.start_link(__MODULE__, state, name: generate_via_tuple(state.id, state.interface))
   end
@@ -119,6 +123,10 @@ defmodule Peridio.RAT.Tunnel do
     end
   end
 
+  def handle_call(:get_state, _from, state) do
+    {:reply, state, state}
+  end
+
   def handle_info(:ttl_timeout, state) do
     # Just stop the process here and rely on the terminate callback to do the work.
     {:stop, :normal, state}