FIN is sent before earlier data #3100
Description
If an application does a large write and then a shutdown(SHUT_WR), the FIN packet seems to be sent before the data (and even before acknowledging the peer's SYN). For example with the client:
s = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
s.connect(('server', 8080))
s.send(b'1'*1000)
s.shutdown(socket.SHUT_WR)
assert b'' == s.recv(1)
s.close()Shadow gives the pcap:
We can see that the 1000 bytes are sent after the FIN packet, which leads to bugs.
@robgjansen This might be related to the tgen stream issue, where we can close the socket while there is still data in the send buffer, and it seems like the FIN might be sent out-of-order.
Server code
import asyncio
import socket
import sys
async def handle_client(client, addr):
loop = asyncio.get_event_loop()
while True:
buf = await loop.sock_recv(client, 1024)
if len(buf) == 0:
break
print("Connection closed:", addr)
client.close()
async def run_server(port):
server = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
server.bind(('0.0.0.0', port))
server.listen(100)
server.setblocking(False)
loop = asyncio.get_event_loop()
while True:
client, addr = await loop.sock_accept(server)
print("New connection:", addr)
loop.create_task(handle_client(client, addr))
asyncio.run(run_server(int(sys.argv[1])))