fix: add lw gateway endpoint placeholder support (#6267)

apps/emqx/include/emqx_placeholder.hrl

@@ -76,6 +76,8 @@
 -define(PH_NODE,                    <<"${node}">>               ).
 -define(PH_REASON,                  <<"${reason}">>             ).
 
+-define(PH_ENDPOINT_NAME,           <<"${endpoint_name}">>      ).
+
 %% sync change these place holder with binary def.
 -define(PH_S_ACTION,                  "${action}"               ).
 -define(PH_S_CERT_SUBJECT,            "${cert_subject}"         ).
@@ -108,5 +110,6 @@
 -define(PH_S_DISCONNECTED_AT,         "${disconnected_at}"      ).
 -define(PH_S_NODE,                    "${node}"                 ).
 -define(PH_S_REASON,                  "${reason}"               ).
+-define(PH_S_ENDPOINT_NAME,           "${endpoint_name}"        ).
 
 -endif.

apps/emqx/src/emqx_mountpoint.erl

@@ -67,14 +67,17 @@ unmount(MountPoint, Msg = #message{topic = Topic}) ->
 -spec(replvar(maybe(mountpoint()), map()) -> maybe(mountpoint())).
 replvar(undefined, _Vars) ->
     undefined;
-replvar(MountPoint, #{clientid := ClientId, username := Username}) ->
+replvar(MountPoint, Vars) ->
-    lists:foldl(fun feed_var/2, MountPoint,
+    ClientID     = maps:get(clientid, Vars, undefined),
-                [{?PH_CLIENTID, ClientId}, {?PH_USERNAME, Username}]).
+    UserName     = maps:get(username, Vars, undefined),
+    EndpointName = maps:get(endpoint_name, Vars, undefined),
+    List = [ {?PH_CLIENTID, ClientID}
+           , {?PH_USERNAME, UserName}
+           , {?PH_ENDPOINT_NAME, EndpointName}
+           ],
+    lists:foldl(fun feed_var/2, MountPoint, List).
 
-feed_var({?PH_CLIENTID, ClientId}, MountPoint) ->
+feed_var({_PlaceHolder, undefined}, MountPoint) ->
-    emqx_topic:feed_var(?PH_CLIENTID, ClientId, MountPoint);
-feed_var({?PH_USERNAME, undefined}, MountPoint) ->
     MountPoint;
-feed_var({?PH_USERNAME, Username}, MountPoint) ->
+feed_var({PlaceHolder, Value}, MountPoint) ->
-    emqx_topic:feed_var(?PH_USERNAME, Username, MountPoint).
+    emqx_topic:feed_var(PlaceHolder, Value, MountPoint).
-

apps/emqx_gateway/etc/emqx_gateway.conf.example

@@ -256,7 +256,7 @@ gateway.lwm2m {
   enable_stats = true
 
   ## When publishing or subscribing, prefix all topics with a mountpoint string.
-  mountpoint = "lwm2m/%u"
+  mountpoint = "lwm2m/${username}"
 
   xml_dir = "{{ platform_etc_dir }}/lwm2m_xml"
 

apps/emqx_gateway/src/emqx_gateway_api.erl

@@ -16,6 +16,8 @@
 %%
 -module(emqx_gateway_api).
 
+-include_lib("emqx/include/emqx_placeholder.hrl").
+
 -behaviour(minirest_api).
 
 -import(emqx_gateway_http,
@@ -293,7 +295,7 @@ schema_gateway_overview_list() ->
         <<"type">> => <<"udp">>,
         <<"running">> => true,
         <<"bind">> => 5783}],
-  <<"mountpoint">> => <<"lwm2m/%e/">>,
+  <<"mountpoint">> => <<"lwm2m/", ?PH_S_ENDPOINT_NAME, "/">>,
   <<"qmode_time_windonw">> => 22,
   <<"translators">> =>
       #{<<"command">> => <<"dn/#">>,<<"notify">> => <<"up/notify">>,