ejabberd_listener: Try to create provisional socket in final directory (#4422)

and if that path is too long, then try HOME directory,
if that's too long too, throw error explaining the problem.

By the way, cutting the base64 string to 107 is a bad idea,
as it encodes the final path, which would get lost and crash.

src/ejabberd_listener.erl

@@ -224,13 +224,26 @@ setup_provisional_udsocket_dir(DefinitivePath) ->
     ProvisionalPath = get_provisional_udsocket_path(DefinitivePath),
     ?INFO_MSG("Creating a Unix Domain Socket provisional file at ~ts for the definitive path ~s",
               [ProvisionalPath, DefinitivePath]),
-    ProvisionalPath.
+    ProvisionalPathAbsolute = relative_socket_to_mnesia(ProvisionalPath),
+    create_base_dir(ProvisionalPathAbsolute),
+    ProvisionalPathAbsolute.
 
 get_provisional_udsocket_path(Path) ->
     PathBase64 = misc:term_to_base64(Path),
     PathBuild = filename:join(misc:get_home(), PathBase64),
-    %% Shorthen the path, a long path produces a crash when opening the socket.
+    DestPath = filename:join(filename:dirname(Path), PathBase64),
-    binary:part(PathBuild, {0, erlang:min(107, byte_size(PathBuild))}).
+    case {byte_size(DestPath) > 107, byte_size(PathBuild) > 107} of
+        {false, _} ->
+            DestPath;
+        {true, false} ->
+            ?INFO_MSG("The provisional Unix Domain Socket path ~ts is longer than 107, let's use home directory instead which is ~p", [DestPath, byte_size(PathBuild)]),
+            PathBuild;
+        {true, true} ->
+            ?ERROR_MSG("The Unix Domain Socket path ~ts is too long, "
+                       "and I cannot create the provisional file safely. "
+                       "Please configure a shorter path and try again.", [Path]),
+            throw({error_socket_path_too_long, Path})
+    end.
 
 get_definitive_udsocket_path(<<"unix", _>> = Unix) ->
     Unix;
@@ -271,17 +284,20 @@ set_definitive_udsocket(<<"unix:", Path/binary>>, Opts) ->
             end
     end,
     FinalPath = relative_socket_to_mnesia(Path),
-    FinalPathDir = filename:dirname(FinalPath),
+    create_base_dir(FinalPath),
-    case file:make_dir(FinalPathDir) of
-        ok ->
-            file:change_mode(FinalPathDir, 8#00700);
-        _ ->
-            ok
-    end,
     file:rename(Prov, FinalPath);
 set_definitive_udsocket(Port, _Opts) when is_integer(Port) ->
     ok.
 
+create_base_dir(Path) ->
+    Dirname = filename:dirname(Path),
+    case file:make_dir(Dirname) of
+        ok ->
+            file:change_mode(Dirname, 8#00700);
+        _ ->
+            ok
+    end.
+
 relative_socket_to_mnesia(Path1) ->
     case filename:pathtype(Path1) of
         absolute ->