feat: add content-sensitive proxy behaviour for UDP

include/esockd_proxy.hrl

@@ -0,0 +1,63 @@
+%%--------------------------------------------------------------------
+%% Copyright (c) 2024 EMQ Technologies Co., Ltd. All Rights Reserved.
+%%
+%% Licensed under the Apache License, Version 2.0 (the "License");
+%% you may not use this file except in compliance with the License.
+%% You may obtain a copy of the License at
+%%
+%%     http://www.apache.org/licenses/LICENSE-2.0
+%%
+%% Unless required by applicable law or agreed to in writing, software
+%% distributed under the License is distributed on an "AS IS" BASIS,
+%% WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+%% See the License for the specific language governing permissions and
+%% limitations under the License.
+%%--------------------------------------------------------------------
+
+-ifndef(ESOCKD_PROXY_HRL).
+-define(ESOCKD_PROXY_HRL, true).
+
+-define(SSL_TRANSPORT, esockd_transport).
+-define(PROXY_TRANSPORT, esockd_udp_proxy).
+
+-type proxy_id() :: pid().
+-type socket_packet() :: binary().
+-type socket() :: inet:socket() | ssl:sslsocket().
+
+-type transport() :: {udp, pid(), socket()} | ?SSL_TRANSPORT.
+-type proxy_transport() :: {?PROXY_TRANSPORT, pid(), socket()}.
+-type address() :: {inet:ip_address(), inet:port_number()}.
+-type peer() :: socket() | address().
+
+-type connection_module() :: atom().
+-type connection_state() :: term().
+-type connection_packet() :: term().
+
+-type connection_id() ::
+    peer()
+    | integer()
+    | string()
+    | binary().
+
+-type proxy_packet() ::
+    {?PROXY_TRANSPORT, proxy_id(), binary(), connection_packet()}.
+
+%% Routing information search results
+
+%% send raw socket packet
+-type get_connection_id_result() ::
+    %% send decoded packet
+    {ok, connection_id(), connection_packet(), connection_state()}
+    | invalid.
+
+-type connection_options() :: #{
+    esockd_proxy_opts := proxy_options(),
+    atom() => term()
+}.
+
+-type proxy_options() :: #{
+    connection_mod := connection_module(),
+    heartbeat => non_neg_integer()
+}.
+
+-endif.

rebar.config

@@ -18,6 +18,10 @@
 {src_dirs, ["src"]}.
 
 
+{deps,
+    [ {gproc, {git, "https://github.com/uwiger/gproc", {tag, "0.8.0"}}}
+    ]}.
+
 {cover_enabled, true}.
 {cover_opts, [verbose]}.
 {cover_export_enabled, true}.

src/esockd_sup.erl

@@ -53,7 +53,7 @@ start_link() ->
 child_spec(Proto, ListenOn, Opts) when is_atom(Proto) ->
     ListenerRef = {Proto, ListenOn},
     _ = esockd_server:set_listener_prop(ListenerRef, type, tcp),
-    _ = esockd_server:set_listener_prop(ListenerRef, options, Opts),    
+    _ = esockd_server:set_listener_prop(ListenerRef, options, Opts),
     #{id => child_id(Proto, ListenOn),
       start => {esockd_listener_sup, start_link, [Proto, ListenOn]},
       restart => transient,
@@ -76,7 +76,7 @@ udp_child_spec(Proto, Port, Opts) when is_atom(Proto) ->
 dtls_child_spec(Proto, Port, Opts) when is_atom(Proto) ->
     ListenerRef = {Proto, Port},
     _ = esockd_server:set_listener_prop(ListenerRef, type, dtls),
-    _ = esockd_server:set_listener_prop(ListenerRef, options, Opts),    
+    _ = esockd_server:set_listener_prop(ListenerRef, options, Opts),
     #{id => child_id(Proto, Port),
       start => {esockd_listener_sup, start_link, [Proto, Port]},
       restart => transient,
@@ -191,5 +191,11 @@ init([]) ->
                type => worker,
                modules => [esockd_server]
               },
-    {ok, {SupFlags, [Limiter, Server]}}.
-
+    ProxyDB = #{id => esockd_udp_proxy_db,
+                start => {esockd_udp_proxy_db, start_link, []},
+                restart => permanent,
+                shutdown => 5000,
+                type => worker,
+                modules => [esockd_udp_proxy_db]
+               },
+    {ok, {SupFlags, [Limiter, Server, ProxyDB]}}.

src/udp_proxy/doc/proxy.plantuml

@@ -0,0 +1,43 @@
+@startuml
+skinparam dpi 300
+left to right direction
+
+frame client {
+      card clinet1
+      card client2
+      card client3
+}
+
+frame proxy {
+      label "proxy converts the udp connection\nto long connection in the application"
+      agent proxy1
+      agent proxy2
+      agent proxy3
+}
+
+frame connection {
+      card connection1
+      card connection2
+      card connection3
+}
+
+clinet1 .[#red].> proxy1
+client2 .[#blue].> proxy1
+client3 ..> proxy2
+client3 ..> proxy3
+
+proxy1 -[#red]-> connection1 : client1
+proxy1 -[#blue]-> connection2 : client2
+proxy2 --> connection3 : client3
+proxy3 --> connection3 : client3
+
+note bottom of proxy1
+different clients use the same UDP channel,e.g NAT, the proxy will first disconnect the existing connection and then connect to the new one
+endnote
+
+
+note right of proxy
+proxy2 and proxy3 are multiple channels used by a client,e.g LB
+endnote
+
+@enduml