fix(socketcand): refuse remote frames instead of sending them as normal ones

can/interfaces/socketcand/socketcand.py

@@ -176,6 +176,13 @@ def convert_ascii_message_to_can_message(ascii_msg: str) -> can.Message:
 def convert_can_message_to_ascii_message(can_message: can.Message) -> str:
     # Note: socketcan bus adds extended flag, remote_frame_flag & error_flag to id
     # not sure if that is necessary here
+    if can_message.is_remote_frame:
+        # The send command is "< send id dlc [data]* >", there is no field for
+        # the remote request flag, so the frame would go out as a normal one
+        raise can.CanOperationError(
+            "socketcand cannot send remote frames, its send command has no "
+            "remote request flag"
+        )
     can_id = can_message.arbitration_id
     if can_message.is_extended_id:
         can_id_string = f"{(can_id&0x1FFFFFFF):08X}"

doc/changelog.d/2091.fixed.rst

@@ -0,0 +1 @@
+Refuse to send remote frames on the ``socketcand`` interface instead of sending them as normal frames. The socketcand protocol has no remote request flag. (:issue:`2091`)

test/test_socketcand.py

@@ -42,5 +42,32 @@ def test_missing_ending_character(self):
         self.assertIsNone(msg)
 
 
+class TestConvertCanMessageToAsciiMessage(unittest.TestCase):
+    def test_standard_frame(self):
+        msg = can.Message(
+            arbitration_id=0x123, data=[0x01, 0x02, 0x03, 0x04], is_extended_id=False
+        )
+        self.assertEqual(
+            socketcand.convert_can_message_to_ascii_message(msg),
+            "< send 123 4 1 2 3 4 >",
+        )
+
+    def test_extended_frame(self):
+        msg = can.Message(
+            arbitration_id=0x1AAAAAAA, data=[0x01, 0xF1], is_extended_id=True
+        )
+        self.assertEqual(
+            socketcand.convert_can_message_to_ascii_message(msg),
+            "< send 1AAAAAAA 2 1 f1 >",
+        )
+
+    def test_remote_frame_is_refused(self):
+        msg = can.Message(
+            arbitration_id=0x403, is_remote_frame=True, is_extended_id=False
+        )
+        with self.assertRaises(can.CanOperationError):
+            socketcand.convert_can_message_to_ascii_message(msg)
+
+
 if __name__ == "__main__":
     unittest.main()