Cocotb with scapy cosimulation

Hi. I’ve been using Cocotb with scapy for simulating a tcp stack. Till now I’ve successfully run the ping/arp procedure. It’s TCP stack <=>MAC <=> cocotb <=> TAP device on wsl2 windows10 2004

This is the code I’m using for ping

@cocotb.coroutine
async def rgmii_sfuncion(a, b, c):
    while True:
        data = a.recv_raw()
        crc = crc32(data[1])
        rawdata = b'\x55\x55\x55\x55\x55\x55\x55\xD5' + data[1]
        for i in range(4):
            temp = (crc >> (8*i)) & 0xFF
            rawdata += bytes([temp])
        await b.send(rawdata)
        await b.wait()
        rx_frame = await c.recv()
        #a.send(rx_frame.data[8:])
        a.outs.write(rx_frame.data[8:])

It needs a packet send followed by a packet recv. So ping and arp works fine. I think.

So when it comes to tcp, the problem is how can I recv a packet while send a packet concurrently.

I’m thinking about

@cocotb.coroutine
async def rgmii_sfuncion(a, b, c):
    while True:
        data = a.recv_raw()
        crc = crc32(data[1])
        rawdata = b'\x55\x55\x55\x55\x55\x55\x55\xD5' + data[1]
        for i in range(4):
            temp = (crc >> (8*i)) & 0xFF
            rawdata += bytes([temp])
        await b.send(rawdata)
        await b.wait()
        #rx_frame = await c.recv()
        #a.send(rx_frame.data[8:])
        #a.outs.write(rx_frame.data[8:])

@cocotb.coroutine
async def rgmii_rfuncion(a, b, c):
    while True:
        rx_frame = await c.recv()
        #a.send(rx_frame.data[8:])
        a.outs.write(rx_frame.data[8:])

Is that work? I’ve tried the code before but no fortune.

But there may be a problem in the tcp stack.

[silenuszhi]

The problem is my send and recv function is both while true loop.

This is the point of cocotb.fork. It creates two concurrent tasks that run “at the same time”. So two infinite loops will work fine.

In async def recv. I use the scapy.recv_raw() which is a blocking function

Ahh, I see. scapy.recv_raw and the other scapy calls are threaded blocking calls. Wrap the functions that block in cocotb.external to turn them into an coroutine that you can await on. For example:

data = await cocotb.external(a.recv_raw)()

I’m a such noob of python. My mistake. After surround both scapy read / write function with cocotb.external. Now it works like a charm.

Thankyou all for help. @ktbarrett @alexforencich @themperek

[silenuszhi]

Ahh. I get the problem. Need sometime to figure it out. Update later. Close for now.