Add function to enable localhost communication only from env var

rmw/CMakeLists.txt

@@ -28,6 +28,7 @@ set(rmw_sources
  "src/allocators.c"
  "src/convert_rcutils_ret_to_rmw_ret.c"
  "src/event.c"
+ "src/host.c"
  "src/init.c"
  "src/init_options.c"
  "src/names_and_types.c"

rmw/include/rmw/host.h

@@ -0,0 +1,43 @@
+// Copyright 2019 Open Source Robotics Foundation, Inc.
+//
+// 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 RMW__IMPL__CPP__HOST_H
+#define RMW__IMPL__CPP__HOST_H
+
+#ifdef __cplusplus
+extern "C"
+{
+#endif
+
+#include "rmw/macros.h"
+#include "rmw/types.h"
+
+const char * RMW_LOCAL_HOST_ENV_VAR = "ROS_LOCALHOST_ONLY";
+
+/// Determine if the user wants to communicate using loopback only.
+/**
+ * Checks if localhost should be used for network communication checking ROS_LOCALHOST_ONLY env
+ * variable
+ * \returns true if ROS_LOCALHOST_ONLY is 1 or true, false otherwise.
+ */
+RMW_PUBLIC
+RMW_WARN_UNUSED
+bool
+rmw_local_host_only();
+
+#ifdef __cplusplus
+}
+#endif
+
+#endif // RMW__IMPL__CPP__HOST_H

rmw/src/host.c

@@ -0,0 +1,29 @@
+// Copyright 2019 Open Source Robotics Foundation, Inc.
+//
+// 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.
+
+#include <rmw/host.h>
+
+#include "rcutils/get_env.h"
+
+#include <stdlib.h>
+#include <string.h>
+
+bool
+rmw_local_host_only()
+{
+ const char * ros_local_host_env_val = NULL;
+ return rcutils_get_env(RMW_LOCAL_HOST_ENV_VAR, &ros_local_host_env_val) == NULL &&
+ ros_local_host_env_val != NULL &&
+ (strcmp(ros_local_host_env_val, "true") == 0 || strcmp(ros_local_host_env_val, "1") == 0);
+}