From 4b4e5fdbfa4b0af912e228c79a0ec63e867e2441 Mon Sep 17 00:00:00 2001
From: Markus Koch <markus@notsyncing.net>
Date: Fri, 13 May 2022 18:20:13 +0200
Subject: [PATCH] bench: hw_itl: Calculate and append FCS for incoming frames

---
 cocotb/hw_itl.py | 8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/cocotb/hw_itl.py b/cocotb/hw_itl.py
index 62a92eb..7f691e4 100644
--- a/cocotb/hw_itl.py
+++ b/cocotb/hw_itl.py
@@ -13,6 +13,7 @@ import time
 import os
 import asyncio
 import fcntl
+import zlib
 
 '''
 # Set up virtual device using
@@ -37,11 +38,18 @@ class MacDevReceiver():
 		self.macdev.bind((dev, 0))
 		fcntl.fcntl(self.macdev, fcntl.F_SETFL, os.O_NONBLOCK) # Not the best way to poll, but I couldn't get asyncio to play nicely with threading...
 
+	def eth_fcs(self, data):
+		crc = zlib.crc32(data) & 0xFFFF_FFFF
+		return crc.to_bytes(4, byteorder='little')
+
 	async def main(self):
 		ETH_HEAD = b'\x55\x55\x55\x55\xD5'
 		while True:
 			try:
 				r = self.macdev.recv(2000)
+				if len(r) < 60:
+					r += b'\x00' * (60 - len(r))
+				r += self.eth_fcs(r)
 				await self.eth_tx.send(ETH_HEAD + r);
 			except:
 				await Timer(1, "us")