TCP_USER_DELAY Testing

14358_repro.py

import socket
import sys
import time

if len(sys.argv) > 1:
    TIMEOUT = int(sys.argv[1])
else:
    TIMEOUT = 5000

HOST="127.0.0.1"
PORT=12345


s = socket.socket(
    socket.AF_INET, socket.SOCK_STREAM)
s.setsockopt(
    socket.IPPROTO_TCP, socket.TCP_USER_TIMEOUT, TIMEOUT
)
s.connect((HOST, PORT))

print(
    ("Sleeping 10s for you to partition the network"
     "on {0}:{1}").format(
         HOST, PORT
    )
)
time.sleep(10)

print("Attempting to send on socket, waiting for an exception")
print("TCP_USER_TIMEOUT={0}".format(TIMEOUT))

start = time.time()
while True:
    try:
        s.send(b'hi\n')
        time.sleep(1)
    except Exception as e:
        print('Detected partition!')
        print(e)
        break

print("Partition healed after {}s".format(time.time() - start))

4.13.0-19-results.txt

$ uname -r
4.13.0-19-generic

$ python 14358_repro.py 5000
Sleeping 10s for you to partition the networkon 127.0.0.1:12345
Attempting to send on socket, waiting for an exception
TCP_USER_TIMEOUT=5000
Detected partition!
[Errno 110] Connection timed out
Partition healed after 7.0073323249816895s

$ python 14358_repro.py 10000
Sleeping 10s for you to partition the networkon 127.0.0.1:12345
Attempting to send on socket, waiting for an exception
TCP_USER_TIMEOUT=10000
Detected partition!
[Errno 110] Connection timed out
Partition healed after 14.011962413787842s

$ python 14358_repro.py 30000
Sleeping 10s for you to partition the networkon 127.0.0.1:12345
Attempting to send on socket, waiting for an exception
TCP_USER_TIMEOUT=30000
Detected partition!
[Errno 110] Connection timed out
Partition healed after 54.052321434020996s

listener.sh

pkill -9 -f "nc -l 12345" && sudo iptables -F OUTPUT;  nc -l 12345 &

partition.sh

# To partition the network
sudo iptables -A OUTPUT -p tcp -d 127.0.0.1 --dport 12345 -j DROP