Add basic valid pairs keepalives (#12)

Author: LVala

lib/candidate_pair.ex

@@ -7,6 +7,9 @@ defmodule ExICE.CandidatePair do
   alias ExICE.ICEAgent
   alias ExICE.Candidate
 
+  # Tr timeout (keepalives) in ms
+  @tr_timeout 15 * 1000
+
   @type state() :: :waiting | :in_progress | :succeeded | :failed | :frozen
 
   @type t() :: %__MODULE__{
@@ -19,7 +22,8 @@ defmodule ExICE.CandidatePair do
           state: state(),
           valid?: boolean,
           succeeded_pair_id: integer() | nil,
-          discovered_pair_id: integer() | nil
+          discovered_pair_id: integer() | nil,
+          keepalive_timer: reference() | nil
         }
 
   @enforce_keys [:id, :local_cand, :remote_cand, :priority]
@@ -30,7 +34,8 @@ defmodule ExICE.CandidatePair do
                 state: :frozen,
                 valid?: false,
                 succeeded_pair_id: nil,
-                discovered_pair_id: nil
+                discovered_pair_id: nil,
+                keepalive_timer: nil
               ]
 
   @doc false
@@ -50,6 +55,19 @@ defmodule ExICE.CandidatePair do
     }
   end
 
+  @spec schedule_keepalive(t(), Process.dest()) :: :ok
+  def schedule_keepalive(pair, dest \\ self())
+
+  def schedule_keepalive(%{keepalive_timer: timer} = pair, dest) when is_reference(timer) do
+    Process.cancel_timer(timer)
+    schedule_keepalive(%{pair | keepalive_timer: nil}, dest)
+  end
+
+  def schedule_keepalive(pair, dest) do
+    ref = Process.send_after(dest, {:keepalive, pair.id}, @tr_timeout)
+    %{pair | keepalive_timer: ref}
+  end
+
   @spec recompute_priority(t(), ICEAgent.role()) :: t()
   def recompute_priority(pair, role) do
     %__MODULE__{pair | priority: priority(role, pair.local_cand, pair.remote_cand)}

lib/ice_agent.ex

@@ -411,6 +411,42 @@ defmodule ExICE.ICEAgent do
     end
   end
 
+  @impl true
+  def handle_info({:keepalive, id}, %{selected_pair: s_pair} = state)
+      when not is_nil(s_pair) and s_pair.id == id do
+    # if pair was selected, send keepalives only on that pair
+    pair = CandidatePair.schedule_keepalive(s_pair)
+    send_keepalive(state.checklist[id])
+    state = put_in(state.checklist[id], pair)
+    {:noreply, state}
+  end
+
+  @impl true
+  def handle_info({:keepalive, _id}, %{selected_pair: s_pair} = state) when not is_nil(s_pair) do
+    # note: current implementation assumes that, if selected pair exists, none of the already existing
+    # valid pairs will ever become selected (only new appearing valid pairs)
+    # that's why there's no call to `CandidatePair.schedule_keepalive/1`
+    {:noreply, state}
+  end
+
+  @impl true
+  def handle_info({:keepalive, id}, state) do
+    # TODO: keepalives should be send only if no data has been send for @tr_timeout
+    # atm, we send keepalives anyways, also it might be better to pace them with ta_timer
+    # TODO: candidates not in a valid pair also should be kept alive (RFC 8445, sect 5.1.1.4)
+    case Map.fetch(state.checklist, id) do
+      {:ok, pair} ->
+        pair = CandidatePair.schedule_keepalive(pair)
+        state = put_in(state.checklist[id], pair)
+        send_keepalive(pair)
+        {:noreply, state}
+
+      :error ->
+        Logger.warning("Received keepalive request for non-existant candidate pair")
+        {:noreply, state}
+    end
+  end
+
   @impl true
   def handle_info({:udp, socket, src_ip, src_port, packet}, state) do
     if ExSTUN.is_stun(packet) do
@@ -774,6 +810,9 @@ defmodule ExICE.ICEAgent do
 
       {pair_id, state} = add_valid_pair(valid_pair, conn_check_pair, checklist_pair, state)
 
+      pair = CandidatePair.schedule_keepalive(state.checklist[pair_id])
+      state = put_in(state.checklist[pair_id], pair)
+
       # get new conn check pair as it will have updated
       # discovered and succeeded pair fields
       conn_check_pair = Map.fetch!(state.checklist, conn_check_pair.id)
@@ -1445,6 +1484,18 @@ defmodule ExICE.ICEAgent do
     %{state | ta_timer: nil}
   end
 
+  defp send_keepalive(pair) do
+    type = %Type{class: :indication, method: :binding}
+
+    req =
+      type
+      |> Message.new()
+      |> Message.with_fingerprint()
+
+    dst = {pair.remote_cand.address, pair.remote_cand.port}
+    do_send(pair.local_cand.socket, dst, Message.encode(req))
+  end
+
   @doc false
   @spec send_conn_check(CandidatePair.t(), map()) :: {CandidatePair.t(), map()}
   def send_conn_check(pair, state) do

mix.exs

@@ -30,7 +30,7 @@ defmodule ExICE.MixProject do
   defp deps do
     [
       {:ex_stun, "~> 0.1.0"},
-      {:excoveralls, "~> 0.14.6", only: :test, runtime: false},
+      {:excoveralls, "~> 0.15", only: :test, runtime: false},
       {:ex_doc, "~> 0.27", only: :dev, runtime: false},
       {:credo, "~> 1.6", only: [:dev, :test], runtime: false}
     ]

mix.lock

@@ -5,11 +5,11 @@
   "earmark_parser": {:hex, :earmark_parser, "1.4.26", "f4291134583f373c7d8755566122908eb9662df4c4b63caa66a0eabe06569b0a", [:mix], [], "hexpm", "48d460899f8a0c52c5470676611c01f64f3337bad0b26ddab43648428d94aabc"},
   "ex_doc": {:hex, :ex_doc, "0.28.4", "001a0ea6beac2f810f1abc3dbf4b123e9593eaa5f00dd13ded024eae7c523298", [:mix], [{:earmark_parser, "~> 1.4.19", [hex: :earmark_parser, repo: "hexpm", optional: false]}, {:makeup_elixir, "~> 0.14", [hex: :makeup_elixir, repo: "hexpm", optional: false]}, {:makeup_erlang, "~> 0.1", [hex: :makeup_erlang, repo: "hexpm", optional: false]}], "hexpm", "bf85d003dd34911d89c8ddb8bda1a958af3471a274a4c2150a9c01c78ac3f8ed"},
   "ex_stun": {:hex, :ex_stun, "0.1.0", "252474bf4c8519fbf4bc0fbfc6a1b846a634b1478c65dbbfb4b6ab4e33c2a95a", [:mix], [], "hexpm", "629fc8be45b624a92522f81d85ba001877b1f0745889a2419bdb678790d7480c"},
-  "excoveralls": {:hex, :excoveralls, "0.14.6", "610e921e25b180a8538229ef547957f7e04bd3d3e9a55c7c5b7d24354abbba70", [:mix], [{:hackney, "~> 1.16", [hex: :hackney, repo: "hexpm", optional: false]}, {:jason, "~> 1.0", [hex: :jason, repo: "hexpm", optional: false]}], "hexpm", "0eceddaa9785cfcefbf3cd37812705f9d8ad34a758e513bb975b081dce4eb11e"},
+  "excoveralls": {:hex, :excoveralls, "0.17.0", "279f124dba347903bb654bc40745c493ae265d45040001b4899ea1edf88078c7", [:mix], [{:castore, "~> 1.0", [hex: :castore, repo: "hexpm", optional: true]}, {:jason, "~> 1.0", [hex: :jason, repo: "hexpm", optional: false]}], "hexpm", "08b638d114387a888f9cb8d65f2a0021ec04c3e447b793efa7c1e734aba93004"},
   "file_system": {:hex, :file_system, "0.2.10", "fb082005a9cd1711c05b5248710f8826b02d7d1784e7c3451f9c1231d4fc162d", [:mix], [], "hexpm", "41195edbfb562a593726eda3b3e8b103a309b733ad25f3d642ba49696bf715dc"},
   "hackney": {:hex, :hackney, "1.18.1", "f48bf88f521f2a229fc7bae88cf4f85adc9cd9bcf23b5dc8eb6a1788c662c4f6", [:rebar3], [{:certifi, "~>2.9.0", [hex: :certifi, repo: "hexpm", optional: false]}, {:idna, "~>6.1.0", [hex: :idna, repo: "hexpm", optional: false]}, {:metrics, "~>1.0.0", [hex: :metrics, repo: "hexpm", optional: false]}, {:mimerl, "~>1.1", [hex: :mimerl, repo: "hexpm", optional: false]}, {:parse_trans, "3.3.1", [hex: :parse_trans, repo: "hexpm", optional: false]}, {:ssl_verify_fun, "~>1.1.0", [hex: :ssl_verify_fun, repo: "hexpm", optional: false]}, {:unicode_util_compat, "~>0.7.0", [hex: :unicode_util_compat, repo: "hexpm", optional: false]}], "hexpm", "a4ecdaff44297e9b5894ae499e9a070ea1888c84afdd1fd9b7b2bc384950128e"},
   "idna": {:hex, :idna, "6.1.1", "8a63070e9f7d0c62eb9d9fcb360a7de382448200fbbd1b106cc96d3d8099df8d", [:rebar3], [{:unicode_util_compat, "~>0.7.0", [hex: :unicode_util_compat, repo: "hexpm", optional: false]}], "hexpm", "92376eb7894412ed19ac475e4a86f7b413c1b9fbb5bd16dccd57934157944cea"},
-  "jason": {:hex, :jason, "1.3.0", "fa6b82a934feb176263ad2df0dbd91bf633d4a46ebfdffea0c8ae82953714946", [:mix], [{:decimal, "~> 1.0 or ~> 2.0", [hex: :decimal, repo: "hexpm", optional: true]}], "hexpm", "53fc1f51255390e0ec7e50f9cb41e751c260d065dcba2bf0d08dc51a4002c2ac"},
+  "jason": {:hex, :jason, "1.4.1", "af1504e35f629ddcdd6addb3513c3853991f694921b1b9368b0bd32beb9f1b63", [:mix], [{:decimal, "~> 1.0 or ~> 2.0", [hex: :decimal, repo: "hexpm", optional: true]}], "hexpm", "fbb01ecdfd565b56261302f7e1fcc27c4fb8f32d56eab74db621fc154604a7a1"},
   "makeup": {:hex, :makeup, "1.1.0", "6b67c8bc2882a6b6a445859952a602afc1a41c2e08379ca057c0f525366fc3ca", [:mix], [{:nimble_parsec, "~> 1.2.2 or ~> 1.3", [hex: :nimble_parsec, repo: "hexpm", optional: false]}], "hexpm", "0a45ed501f4a8897f580eabf99a2e5234ea3e75a4373c8a52824f6e873be57a6"},
   "makeup_elixir": {:hex, :makeup_elixir, "0.16.0", "f8c570a0d33f8039513fbccaf7108c5d750f47d8defd44088371191b76492b0b", [:mix], [{:makeup, "~> 1.0", [hex: :makeup, repo: "hexpm", optional: false]}, {:nimble_parsec, "~> 1.2.3", [hex: :nimble_parsec, repo: "hexpm", optional: false]}], "hexpm", "28b2cbdc13960a46ae9a8858c4bebdec3c9a6d7b4b9e7f4ed1502f8159f338e7"},
   "makeup_erlang": {:hex, :makeup_erlang, "0.1.1", "3fcb7f09eb9d98dc4d208f49cc955a34218fc41ff6b84df7c75b3e6e533cc65f", [:mix], [{:makeup, "~> 1.0", [hex: :makeup, repo: "hexpm", optional: false]}], "hexpm", "174d0809e98a4ef0b3309256cbf97101c6ec01c4ab0b23e926a9e17df2077cbb"},