bench: hw_itl: Calculate and append FCS for incoming frames

cocotb/hw_itl.py

@@ -1,4 +1,4 @@
-#!/usr/bin/env python
+#!/usr/bin/env python3
 
 import cocotb
 from cocotb.triggers import *
@@ -13,6 +13,14 @@ import time
 import os
 import asyncio
 import fcntl
+import zlib
+
+'''
+# Set up virtual device using
+sudo ip link add virt0 type dummy
+sudo ip link set up virt0
+sudo ip addr add 192.168.2.10/24 dev virt0
+'''
 
 class MacDevReceiver():
 	def __init__(self, dut, eth_tx, eth_rx, dev):
@@ -28,13 +36,20 @@ class MacDevReceiver():
 		ETH_P_ALL=3
 		self.macdev=socket.socket(socket.AF_PACKET, socket.SOCK_RAW, socket.htons(ETH_P_ALL))
 		self.macdev.bind((dev, 0))
-		fcntl.fcntl(self.macdev, fcntl.F_SETFL, os.O_NONBLOCK)
+		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")