Select a new pair only if it has the same or greater priority

Author: mickel8

lib/ex_ice/candidate.ex

@@ -94,13 +94,13 @@ defmodule ExICE.Candidate do
   def new(type, config) when type in [:host, :srflx, :prflx, :relay] do
     transport = Keyword.get(config, :transport, :udp)
 
-    priority =
-      if config[:priority] do
-        config[:priority]
-      else
-        base_address = Keyword.fetch!(config, :base_address)
-        ExICE.Priv.Candidate.priority(base_address, type)
-      end
+    priority = Keyword.fetch!(config, :priority)
+    # if config[:priority] do
+    #   config[:priority]
+    # else
+    #   base_address = config[:base_address] || config[:address] || raise "no address"
+    #   ExICE.Priv.Candidate.priority(base_address, type)
+    # end
 
     address = Keyword.fetch!(config, :address)
 

lib/ex_ice/priv/conn_check_handler/controlling.ex

@@ -109,13 +109,39 @@ defmodule ExICE.Priv.ConnCheckHandler.Controlling do
     pair = %CandidatePair{pair | nominate?: false, nominated?: true}
     ice_agent = put_in(ice_agent.checklist[pair.id], pair)
 
+    ice_agent =
+      cond do
+        ice_agent.selected_pair_id == nil ->
+          Logger.debug("Selecting pair: #{pair_id}")
+          %ICEAgent{ice_agent | selected_pair_id: pair.id}
+
+        ice_agent.selected_pair_id != nil and pair.id != ice_agent.selected_pair_id ->
+          selected_pair = Map.fetch!(ice_agent.checklist, ice_agent.selected_pair_id)
+
+          if pair.priority >= selected_pair.priority do
+            Logger.debug("""
+            Selecting new pair with higher priority. \
+            New pair: #{pair_id}, old pair: #{ice_agent.selected_pair_id}.\
+            """)
+
+            %ICEAgent{ice_agent | selected_pair_id: pair.id}
+          else
+            Logger.debug("Not selecting a new pair as it has lower priority.")
+            ice_agent
+          end
+
+        true ->
+          Logger.debug("Not selecting a new pair as it has the same id")
+          ice_agent
+      end
+
     # the controlling agent could nominate only when eoc was set
     # and checklist finished
     if not ice_agent.aggressive_nomination and not Checklist.finished?(ice_agent.checklist) do
       Logger.warning("Nomination succeeded but checklist hasn't finished.")
     end
 
-    %ICEAgent{ice_agent | nominating?: {false, nil}, selected_pair_id: pair.id}
+    %ICEAgent{ice_agent | nominating?: {false, nil}}
   end
 
   defp resolve_pair(ice_agent, pair) do

lib/ex_ice/priv/ice_agent.ex

@@ -2079,11 +2079,17 @@ defmodule ExICE.Priv.ICEAgent do
     end
   end
 
-  defp get_or_create_remote_cand(ice_agent, src_ip, src_port, _prio_attr) do
+  defp get_or_create_remote_cand(ice_agent, src_ip, src_port, prio_attr) do
     case find_remote_cand(Map.values(ice_agent.remote_cands), src_ip, src_port) do
       nil ->
         # TODO calculate correct prio using prio_attr
-        cand = ExICE.Candidate.new(:prflx, address: src_ip, port: src_port)
+        cand =
+          ExICE.Candidate.new(:prflx,
+            address: src_ip,
+            port: src_port,
+            priority: prio_attr.priority
+          )
+
         Logger.debug("Adding new remote prflx candidate: #{inspect(cand)}")
         ice_agent = put_in(ice_agent.remote_cands[cand.id], cand)
         {cand, ice_agent}