Add enable_loopback option to SocketCAN interface

ros2_socketcan/include/ros2_socketcan/socket_can_common.hpp

@@ -34,10 +34,14 @@ namespace socketcan
 /// Bind a non-blocking CAN_RAW socket to the given interface
 /// \param[in] interface The name of the interface to bind, must be smaller than IFNAMSIZ
 /// \param[in] enable_fd Whether this socket uses CAN FD or not
+/// \param[in] enable_loopback Whether this socket will receive sent messages from other processes
+///    connected to the same socket on the same system
 /// \return The file descriptor bound to the given interface
 /// \throw std::runtime_error If one of socket(), fnctl(), ioctl(), bind() failed
 /// \throw std::domain_error If the provided interface name is too long
-int32_t bind_can_socket(const std::string & interface, bool enable_fd);
+int32_t bind_can_socket(
+  const std::string & interface, bool enable_fd,
+  bool enable_loopback = false);
 
 /// Set SocketCAN filters
 /// \param[in] fd File descriptor of the socket

ros2_socketcan/src/socket_can_common.cpp

@@ -37,7 +37,7 @@ namespace socketcan
 {
 
 ////////////////////////////////////////////////////////////////////////////////
-int32_t bind_can_socket(const std::string & interface, bool enable_fd)
+int32_t bind_can_socket(const std::string & interface, bool enable_fd, bool enable_loopback)
 {
   if (interface.length() >= static_cast<std::string::size_type>(IFNAMSIZ)) {
     throw std::domain_error{"CAN interface name too long"};
@@ -73,14 +73,22 @@ int32_t bind_can_socket(const std::string & interface, bool enable_fd)
   }
   //lint -restore NOLINT
 
+  // Enable local message loopback
+  const int32_t loopback = enable_loopback ? 1 : 0;
+  if (0 !=
+    setsockopt(file_descriptor, SOL_CAN_RAW, CAN_RAW_LOOPBACK, &loopback, sizeof(loopback)))
+  {
+    throw std::runtime_error{"Failed to set local loopback option"};
+  }
+
   // Enable CAN FD support
   const int32_t enable_canfd = enable_fd ? 1 : 0;
   if (0 !=
     setsockopt(
       file_descriptor, SOL_CAN_RAW, CAN_RAW_FD_FRAMES, &enable_canfd,
       sizeof(enable_canfd)))
   {
-    throw std::runtime_error{"Failed to enable CAN FD support"};
+    throw std::runtime_error{"Failed to set CAN FD support option"};
   }
 
   return file_descriptor;