Check if socket server is MaxScale service

We need to handle the case that a MaxScale service is used as a
server over Unix domain sockets.

server/core/internal/service.hh

@@ -337,6 +337,14 @@ SListener service_find_listener(Service* service,
  */
 bool service_port_is_used(int port);
 
+/**
+ * @brief Check if a MaxScale service listens on a Unix domain socket
+ *
+ * @param path The socket path to check
+ * @return True if a MaxScale service uses the socket
+ */
+bool service_socket_is_used(const std::string& socket_path);
+
 /**
  * @brief Check if the service has a listener with a matching name
  *

server/core/server.cc

@@ -914,7 +914,14 @@ bool SERVER::is_mxs_service()
     bool rval = false;
 
     /** Do a coarse check for local server pointing to a MaxScale service */
-    if (strcmp(address, "127.0.0.1") == 0
+    if (address[0] == '/')
+    {
+        if (service_socket_is_used(address))
+        {
+            rval = true;
+        }
+    }
+    else if (strcmp(address, "127.0.0.1") == 0
              || strcmp(address, "::1") == 0
              || strcmp(address, "localhost") == 0
              || strcmp(address, "localhost.localdomain") == 0)

server/core/service.cc

@@ -1559,6 +1559,31 @@ bool service_port_is_used(int port)
     return rval;
 }
 
+bool service_socket_is_used(const std::string& socket_path)
+{
+    bool rval = false;
+    LockGuard guard(this_unit.lock);
+
+    for (Service* service : this_unit.services)
+    {
+        for (const auto& listener : listener_find_by_service(service))
+        {
+            if (listener->address() == socket_path)
+            {
+                rval = true;
+                break;
+            }
+        }
+
+        if (rval)
+        {
+            break;
+        }
+    }
+
+    return rval;
+}
+
 static const char* service_state_to_string(int state)
 {
     switch (state)