From cb518c563a849f9f868342a7350b8f16cf200fd2 Mon Sep 17 00:00:00 2001
From: Javier Casas <javiercasas@geotab.com>
Date: Thu, 15 May 2025 09:32:51 +0200
Subject: [PATCH] parse socketcand error messages to create a CAN error frame

---
 can/interfaces/socketcand/socketcand.py | 32 ++++++++++++++++++++++---
 1 file changed, 29 insertions(+), 3 deletions(-)

diff --git a/can/interfaces/socketcand/socketcand.py b/can/interfaces/socketcand/socketcand.py
index 7a2cc6fd0..6e726003a 100644
--- a/can/interfaces/socketcand/socketcand.py
+++ b/can/interfaces/socketcand/socketcand.py
@@ -125,10 +125,11 @@ def detect_beacon(timeout_ms: int = 3100) -> List[can.typechecking.AutoDetectedC
 
 
 def convert_ascii_message_to_can_message(ascii_msg: str) -> can.Message:
-    if not ascii_msg.startswith("< frame ") or not ascii_msg.endswith(" >"):
-        log.warning(f"Could not parse ascii message: {ascii_msg}")
+    if not ascii_msg.endswith(" >"):
+        log.warning(f"Missing ending character in ascii message: {ascii_msg}")
         return None
-    else:
+
+    if ascii_msg.startswith("< frame "):
         # frame_string = ascii_msg.removeprefix("< frame ").removesuffix(" >")
         frame_string = ascii_msg[8:-2]
         parts = frame_string.split(" ", 3)
@@ -147,6 +148,31 @@ def convert_ascii_message_to_can_message(ascii_msg: str) -> can.Message:
         )
         return can_message
 
+    if ascii_msg.startswith("< error "):
+        frame_string = ascii_msg[8:-2]
+        parts = frame_string.split(" ", 3)
+        can_id, timestamp = int(parts[0], 16), float(parts[1])
+        is_ext = len(parts[0]) != 3
+
+        # socketcand sends no data in the error message so we don't have information
+        # about the error details, therefore the can frame is created with one
+        # data byte set to zero
+        data = bytearray([0])
+        can_dlc = len(data)
+        can_message = can.Message(
+            timestamp=timestamp,
+            arbitration_id=can_id & 0x1FFFFFFF,
+            is_error_frame=True,
+            data=data,
+            dlc=can_dlc,
+            is_extended_id=True,
+            is_rx=True,
+        )
+        return can_message
+
+    log.warning(f"Could not parse ascii message: {ascii_msg}")
+    return None
+
 
 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