diff --git a/etc/emqx.conf b/etc/emqx.conf
index 7454f32f4..b559f28a3 100644
--- a/etc/emqx.conf
+++ b/etc/emqx.conf
@@ -202,9 +202,11 @@ mqtt.max_packet_size = 1MB
 mqtt.max_clientid_len = 65535
 
 ## Maximum topic levels allowed. 0 means no limit.
+## Depth so big may lead to subscribing performance issues.
 ##
-## Value: Number
-mqtt.max_topic_levels = 0
+## Value: Number [0-65535]
+## Default: 128
+mqtt.max_topic_levels = 128
 
 ## Maximum QoS allowed.
 ##
@@ -242,7 +244,7 @@ mqtt.ignore_loop_deliver = false
 mqtt.strict_mode = false
 
 ## Specify the response information returned to the client
-## 
+##
 ## Value: String
 ## mqtt.response_information = example
 
diff --git a/etc/zones.conf b/etc/zones.conf
index a290eaa4d..31845e1e0 100644
--- a/etc/zones.conf
+++ b/etc/zones.conf
@@ -57,8 +57,9 @@ zone.external.force_shutdown_policy = 10000|32MB
 ## zone.external.max_clientid_len = 1024
 
 ## Maximum topic levels allowed. 0 means no limit.
+## Depth so big may lead to subscribing performance issues.
 ##
-## Value: Number
+## Value: Number [0-65535]
 ## zone.external.max_topic_levels = 7
 
 ## Maximum QoS allowed.
@@ -250,7 +251,7 @@ zone.external.ignore_loop_deliver = false
 zone.external.strict_mode = false
 
 ## Specify the response information returned to the client
-## 
+##
 ## Value: String
 ## zone.external.response_information = example
 
@@ -341,7 +342,7 @@ zone.internal.ignore_loop_deliver = false
 zone.internal.strict_mode = false
 
 ## Specify the response information returned to the client
-## 
+##
 ## Value: String
 ## zone.internal.response_information = example
 
diff --git a/priv/emqx.schema b/priv/emqx.schema
index 4bfa44c6a..0ff956869 100644
--- a/priv/emqx.schema
+++ b/priv/emqx.schema
@@ -757,7 +757,7 @@ end}.
 
 %% @doc Set the Maximum topic levels.
 {mapping, "mqtt.max_topic_levels", "emqx.max_topic_levels", [
-  {default, 0},
+  {default, 128},
   {datatype, integer}
 ]}.
 
diff --git a/rebar.config b/rebar.config
index fe785724a..ee58d3dac 100644
--- a/rebar.config
+++ b/rebar.config
@@ -6,7 +6,7 @@
  [{gproc, {git, "https://github.com/uwiger/gproc", {tag, "0.8.0"}}},
   {jiffy, {git, "https://github.com/emqx/jiffy", {tag, "1.0.5"}}},
   {cowboy, {git, "https://github.com/emqx/cowboy", {tag, "2.7.1"}}},
-  {esockd, {git, "https://github.com/emqx/esockd", {tag, "5.7.5"}}},
+  {esockd, {git, "https://github.com/emqx/esockd", {tag, "5.7.6"}}},
   {ekka, {git, "https://github.com/emqx/ekka", {tag, "0.7.10"}}},
   {gen_rpc, {git, "https://github.com/emqx/gen_rpc", {tag, "2.5.0"}}},
   {cuttlefish, {git, "https://github.com/emqx/cuttlefish", {tag, "v3.0.0"}}}
diff --git a/src/emqx.appup.src b/src/emqx.appup.src
index 2c0d887f8..d37dc20c1 100644
--- a/src/emqx.appup.src
+++ b/src/emqx.appup.src
@@ -70,7 +70,8 @@
      {load_module,emqx_pqueue,brutal_purge,soft_purge,[]},
      {load_module,emqx_mqueue,brutal_purge,soft_purge,[]},
      {load_module,emqx_alarm_handler,brutal_purge,soft_purge,[]},
-     {load_module,emqx_misc,brutal_purge,soft_purge,[]}
+     {load_module,emqx_misc,brutal_purge,soft_purge,[]},
+     {load_module, emqx_limiter, brutal_purge, soft_purge, []}
    ]},
    {<<"4.2.4">>, [
      {load_module, emqx_frame, brutal_purge, soft_purge, []},
@@ -89,7 +90,8 @@
      {load_module,emqx_pqueue,brutal_purge,soft_purge,[]},
      {load_module,emqx_mqueue,brutal_purge,soft_purge,[]},
      {load_module,emqx_alarm_handler,brutal_purge,soft_purge,[]},
-     {load_module,emqx_misc,brutal_purge,soft_purge,[]}
+     {load_module,emqx_misc,brutal_purge,soft_purge,[]},
+     {load_module, emqx_limiter, brutal_purge, soft_purge, []}
    ]},
    {<<"4.2.5">>, [
      {load_module, emqx_frame, brutal_purge, soft_purge, []},
@@ -108,7 +110,8 @@
      {load_module,emqx_pqueue,brutal_purge,soft_purge,[]},
      {load_module,emqx_mqueue,brutal_purge,soft_purge,[]},
      {load_module,emqx_alarm_handler,brutal_purge,soft_purge,[]},
-     {load_module,emqx_misc,brutal_purge,soft_purge,[]}
+     {load_module,emqx_misc,brutal_purge,soft_purge,[]},
+     {load_module, emqx_limiter, brutal_purge, soft_purge, []}
    ]},
    {<<"4.2.[6-7]">>, [
      {load_module, emqx_frame, brutal_purge, soft_purge, []},
@@ -120,13 +123,22 @@
      {load_module,emqx_pqueue,brutal_purge,soft_purge,[]},
      {load_module,emqx_mqueue,brutal_purge,soft_purge,[]},
      {load_module,emqx_alarm_handler,brutal_purge,soft_purge,[]},
-     {load_module,emqx_misc,brutal_purge,soft_purge,[]}
+     {load_module,emqx_misc,brutal_purge,soft_purge,[]},
+     {load_module, emqx_limiter, brutal_purge, soft_purge, []}
    ]},
    {<<"4.2.8">>, [
      {load_module, emqx_frame, brutal_purge, soft_purge, []},
      {load_module, emqx_channel, brutal_purge, soft_purge, []},
      {load_module, emqx_connection, brutal_purge, soft_purge, []},
-     {load_module, emqx_cm, brutal_purge, soft_purge, []}
+     {load_module, emqx_ws_connection, brutal_purge, soft_purge, []},
+     {load_module, emqx_cm, brutal_purge, soft_purge, []},
+     {load_module, emqx_limiter, brutal_purge, soft_purge, []}
+   ]},
+   {<<"4.2.9">>, [
+     {load_module, emqx_frame, brutal_purge, soft_purge, []},
+     {load_module, emqx_connection, brutal_purge, soft_purge, []},
+     {load_module, emqx_ws_connection, brutal_purge, soft_purge, []},
+     {load_module, emqx_limiter, brutal_purge, soft_purge, []}
    ]},
    {<<".*">>, []}
  ],
@@ -199,7 +211,8 @@
      {load_module,emqx_pqueue,brutal_purge,soft_purge,[]},
      {load_module,emqx_mqueue,brutal_purge,soft_purge,[]},
      {load_module,emqx_alarm_handler,brutal_purge,soft_purge,[]},
-     {load_module,emqx_misc,brutal_purge,soft_purge,[]}
+     {load_module,emqx_misc,brutal_purge,soft_purge,[]},
+     {load_module, emqx_limiter, brutal_purge, soft_purge, []}
    ]},
    {<<"4.2.4">>, [
      {load_module, emqx_frame, brutal_purge, soft_purge, []},
@@ -218,7 +231,8 @@
      {load_module,emqx_pqueue,brutal_purge,soft_purge,[]},
      {load_module,emqx_mqueue,brutal_purge,soft_purge,[]},
      {load_module,emqx_alarm_handler,brutal_purge,soft_purge,[]},
-     {load_module,emqx_misc,brutal_purge,soft_purge,[]}
+     {load_module,emqx_misc,brutal_purge,soft_purge,[]},
+     {load_module, emqx_limiter, brutal_purge, soft_purge, []}
    ]},
    {<<"4.2.5">>, [
      {load_module, emqx_frame, brutal_purge, soft_purge, []},
@@ -237,7 +251,8 @@
      {load_module,emqx_pqueue,brutal_purge,soft_purge,[]},
      {load_module,emqx_mqueue,brutal_purge,soft_purge,[]},
      {load_module,emqx_alarm_handler,brutal_purge,soft_purge,[]},
-     {load_module,emqx_misc,brutal_purge,soft_purge,[]}
+     {load_module,emqx_misc,brutal_purge,soft_purge,[]},
+     {load_module, emqx_limiter, brutal_purge, soft_purge, []}
    ]},
    {<<"4.2.[6-7]">>, [
      {load_module, emqx_frame, brutal_purge, soft_purge, []},
@@ -249,13 +264,22 @@
      {load_module,emqx_pqueue,brutal_purge,soft_purge,[]},
      {load_module,emqx_mqueue,brutal_purge,soft_purge,[]},
      {load_module,emqx_alarm_handler,brutal_purge,soft_purge,[]},
-     {load_module,emqx_misc,brutal_purge,soft_purge,[]}
+     {load_module,emqx_misc,brutal_purge,soft_purge,[]},
+     {load_module, emqx_limiter, brutal_purge, soft_purge, []}
    ]},
    {<<"4.2.8">>, [
      {load_module, emqx_frame, brutal_purge, soft_purge, []},
      {load_module, emqx_channel, brutal_purge, soft_purge, []},
      {load_module, emqx_connection, brutal_purge, soft_purge, []},
-     {load_module, emqx_cm, brutal_purge, soft_purge, []}
+     {load_module, emqx_ws_connection, brutal_purge, soft_purge, []},
+     {load_module, emqx_cm, brutal_purge, soft_purge, []},
+     {load_module, emqx_limiter, brutal_purge, soft_purge, []}
+   ]},
+   {<<"4.2.9">>, [
+     {load_module, emqx_frame, brutal_purge, soft_purge, []},
+     {load_module, emqx_connection, brutal_purge, soft_purge, []},
+     {load_module, emqx_ws_connection, brutal_purge, soft_purge, []},
+     {load_module, emqx_limiter, brutal_purge, soft_purge, []}
    ]},
    {<<".*">>, []}
  ]
diff --git a/src/emqx_connection.erl b/src/emqx_connection.erl
index ffec9055e..4054c27c4 100644
--- a/src/emqx_connection.erl
+++ b/src/emqx_connection.erl
@@ -589,6 +589,11 @@ parse_incoming(Data, Packets, State = #state{parse_state = ParseState}) ->
             NState = State#state{parse_state = NParseState},
             parse_incoming(Rest, [Packet|Packets], NState)
     catch
+        error:proxy_protocol_config_disabled ->
+            ?LOG(error,
+                 "~nMalformed packet, "
+                 "please check proxy_protocol config for specific listeners and zones~n"),
+            {[{frame_error, proxy_protocol_config_disabled} | Packets], State};
         error:Reason:Stk ->
             ?LOG(error, "~nParse failed for ~0p~n~0p~nFrame data:~0p",
                  [Reason, Stk, Data]),
@@ -812,4 +817,3 @@ stop(Reason, Reply, State) ->
 set_field(Name, Value, State) ->
     Pos = emqx_misc:index_of(Name, record_info(fields, state)),
     setelement(Pos+1, State, Value).
-
diff --git a/src/emqx_frame.erl b/src/emqx_frame.erl
index 7caa92ea8..f0e2f6e4e 100644
--- a/src/emqx_frame.erl
+++ b/src/emqx_frame.erl
@@ -69,6 +69,13 @@
 
 -define(MULTIPLIER_MAX, 16#200000).
 
+%% proxy_protocol v1 header human readable
+-define(PPV1_PROXY, "PROXY ").
+-define(PPV1_PROXY_UNKNOWN, "PROXY UNKNOWN").
+%% proxy_protocol v2 header signature:
+%% 16#0D,16#0A, 16#0D,16#0A,16#00,16#0D,16#0A,16#51,16#55,16#49,16#54,16#0A
+-define(PPV2_HEADER_SIG, "\r\n\r\n\0\r\nQUIT\n").
+
 -dialyzer({no_match, [serialize_utf8_string/2]}).
 
 %%--------------------------------------------------------------------
@@ -98,6 +105,13 @@ parse(Bin) ->
 -spec(parse(binary(), parse_state()) -> parse_result()).
 parse(<<>>, {none, Options}) ->
     {more, {none, Options}};
+parse(<<?PPV1_PROXY, IPVer:5/binary, _Rest/binary>>, {none, _Options})
+  when IPVer =:= <<"TCP4 ">> orelse IPVer =:= <<"TCP6 ">> ->
+    error(proxy_protocol_config_disabled);
+parse(<<?PPV1_PROXY_UNKNOWN, _Rest/binary>>, {none, _Options}) ->
+    error(proxy_protocol_config_disabled);
+parse(<<?PPV2_HEADER_SIG, _Rest/binary>>, {none, _Options}) ->
+    error(proxy_protocol_config_disabled);
 parse(<<Type:4, Dup:1, QoS:2, Retain:1, Rest/binary>>,
       {none, Options = #{strict_mode := StrictMode}}) ->
     %% Validate header if strict mode.
diff --git a/src/emqx_limiter.erl b/src/emqx_limiter.erl
index 447e04fea..8acd50d32 100644
--- a/src/emqx_limiter.erl
+++ b/src/emqx_limiter.erl
@@ -23,6 +23,7 @@
         , init/4 %% XXX: Compatible with before 4.2 version
         , info/1
         , check/2
+        , update_overall_limiter/4
         ]).
 
 -record(limiter, {
@@ -152,3 +153,15 @@ is_message_limiter(conn_messages_in) -> true;
 is_message_limiter(conn_messages_routing) -> true;
 is_message_limiter(overall_messages_routing) -> true;
 is_message_limiter(_) -> false.
+
+update_overall_limiter(Zone, Name, Capacity, Interval) ->
+    case is_overall_limiter(Name) of
+        false -> false;
+        _ ->
+            try
+                esockd_limiter:update({Zone, Name}, Capacity, Interval),
+                true
+            catch _:_:_ ->
+                    false
+            end
+    end.
diff --git a/src/emqx_ws_connection.erl b/src/emqx_ws_connection.erl
index ac975850e..ff7dccd32 100644
--- a/src/emqx_ws_connection.erl
+++ b/src/emqx_ws_connection.erl
@@ -63,7 +63,7 @@
           %% Simulate the active_n opt
           active_n :: pos_integer(),
           %% MQTT Piggyback
-          mqtt_piggyback :: single | multiple, 
+          mqtt_piggyback :: single | multiple,
           %% Limiter
           limiter :: maybe(emqx_limiter:limiter()),
           %% Limit Timer
@@ -486,6 +486,12 @@ parse_incoming(Data, State = #state{parse_state = ParseState}) ->
             NState = State#state{parse_state = NParseState},
             parse_incoming(Rest, postpone({incoming, Packet}, NState))
     catch
+        error:proxy_protocol_config_disabled ->
+            ?LOG(error,
+                 "~nMalformed packet, "
+                 "please check proxy_protocol config for specific listeners and zones~n"),
+            FrameError = {frame_error, proxy_protocol_config_disabled},
+            postpone({incoming, FrameError} ,State);
         error:Reason:Stk ->
             ?LOG(error, "~nParse failed for ~0p~n~0p~nFrame data: ~0p",
                  [Reason, Stk, Data]),
@@ -544,7 +550,7 @@ handle_outgoing(Packets, State = #state{active_n = ActiveN, mqtt_piggyback = MQT
                      postpone({check_gc, Stats}, State);
                  false -> State
              end,
-    
+
     {case MQTTPiggyback of
          single -> [{binary, IoData}];
          multiple -> lists:map(fun(Bin) -> {binary, Bin} end, IoData)
@@ -689,4 +695,3 @@ trigger(Event) -> erlang:send(self(), Event).
 set_field(Name, Value, State) ->
     Pos = emqx_misc:index_of(Name, record_info(fields, state)),
     setelement(Pos+1, State, Value).
-
diff --git a/test/emqx_channel_SUITE.erl b/test/emqx_channel_SUITE.erl
index 613da40ac..12c024775 100644
--- a/test/emqx_channel_SUITE.erl
+++ b/test/emqx_channel_SUITE.erl
@@ -82,7 +82,7 @@ t_chan_caps(_) ->
      #{max_clientid_len := 65535,
        max_qos_allowed := 2,
        max_topic_alias := 65535,
-       max_topic_levels := 0,
+       max_topic_levels := 128,
        retain_available := true,
        shared_subscription := true,
        subscription_identifiers := true,
@@ -768,4 +768,3 @@ session(InitFields) when is_map(InitFields) ->
 quota() ->
     emqx_limiter:init(zone, [{conn_messages_routing, {5, 1}},
                              {overall_messages_routing, {10, 1}}]).
-