Allow to set allocation port range via env variable

Author: LVala

README.md

@@ -88,6 +88,13 @@ RELAY_IP=0.0.0.0
 EXTERNAL_RELAY_IP=167.235.241.140
 ```
 
+Rel will try to open relay addresses in `49_152 - 65_535` port range, but this can be changed. `RELAY_PORT_END` must be greater than `RELAY_PORT_START`.
+
+```console
+RELAY_PORT_START=35000
+RELAY_PORT_END=45000
+```
+
 Remember to use the `REALM` variable specific to your deployment. It's used in `REALM` STUN attributes. See
 [this section of RFC 2617](https://datatracker.ietf.org/doc/html/rfc2617#section-3.2.1) to learn about appropriate values for `REALM` attribute.
 
@@ -96,6 +103,7 @@ REALM=my-amazing-turn.com
 ```
 
 You can configure the number of running `listener` processes. By default, it is equal to number of running Erlang VM schedulers:
+
 ```console
 LISTENER_COUNT=8
 ```

config/config.exs

@@ -1,9 +1,5 @@
 import Config
 
-config :rel,
-  alloc_port_range: 49_152..65_535
-
-# various lifetimes
 config :rel,
   # 1 day in seconds, see https://datatracker.ietf.org/doc/html/draft-uberti-rtcweb-turn-rest-00#section-2.2
   credentials_lifetime: 24 * 60 * 60,

config/runtime.exs

@@ -133,7 +133,9 @@ config :rel,
   relay_ip: relay_ip,
   external_relay_ip: external_relay_ip,
   listen_port: System.get_env("LISTEN_PORT", "3478") |> ConfigUtils.parse_port(),
-  realm: System.get_env("REALM", "example.com")
+  realm: System.get_env("REALM", "example.com"),
+  relay_port_start: System.get_env("RELAY_PORT_START", "49152") |> ConfigUtils.parse_port(),
+  relay_port_end: System.get_env("RELAY_PORT_END", "65535") |> ConfigUtils.parse_port()
 
 # Metrics endpoint configuration
 config :rel,

lib/rel/listener.ex

@@ -22,7 +22,6 @@ defmodule Rel.Listener do
   alias ExSTUN.Message.Attribute.{Username, XORMappedAddress}
 
   @buf_size 2 * 1024 * 1024
-  @default_alloc_ports MapSet.new(Application.compile_env!(:rel, :alloc_port_range))
 
   @spec start_link(term()) :: {:ok, pid()}
   def start_link(args) do
@@ -322,7 +321,10 @@ defmodule Rel.Listener do
       |> Enum.map(fn alloc_origin_state -> Map.fetch!(alloc_origin_state, :alloc_port) end)
       |> MapSet.new()
 
-    available_alloc_ports = MapSet.difference(@default_alloc_ports, used_alloc_ports)
+    relay_port_start = Application.fetch_env!(:rel, :relay_port_start)
+    relay_port_end = Application.fetch_env!(:rel, :relay_port_end)
+    default_alloc_ports = MapSet.new(relay_port_start..relay_port_end)
+    available_alloc_ports = MapSet.difference(default_alloc_ports, used_alloc_ports)
 
     if MapSet.size(available_alloc_ports) == 0 do
       {:error, :out_of_ports}