Paramiko rekeying failure

paramiko_rekey.py

#!/usr/bin/python

import argparse
import paramiko
import sys
import time

DATAFILE = '/tmp/file.txt'

class AcceptPolicy(paramiko.client.MissingHostKeyPolicy):

    def missing_host_key(*args):
        return

parser = argparse.ArgumentParser()
parser.add_argument("--sftp", action='store_true', help="Use SFTP channel (default is session)")
parser.add_argument("host", type=str, help="Hostname to connect to")
parser.add_argument("--username", "-u", type=str, help="Username to use")
parser.add_argument("--rekey", type=int, default=100, help="Rekey interval in kilobytes (default 100)")
args = parser.parse_args()

client = paramiko.SSHClient()
client.set_missing_host_key_policy(AcceptPolicy())
client.connect(hostname=args.host, username=args.username)

transport = client.get_transport()

packetizer = transport.packetizer
packetizer.REKEY_BYTES = 1024 * args.rekey

print "REKEY_BYTES: {}".format(packetizer.REKEY_BYTES)
print "REKEY_PACKETS: {}".format(packetizer.REKEY_PACKETS)

if not args.sftp:
    print "Using SSHClient, which should fail in rekeying"

    count = 0
    while True:
        stdin, stdout, stderr = client.exec_command('cat {}'.format(DATAFILE))
        rekey = False
        for line in stdout:
            if not rekey:
                if transport.packetizer.need_rekey():
                    print "Need rekey"
                    rekey = True

        count += 1
        print "Read file {} times".format(count)
        time.sleep(2)

else:
    print "Using SFTPClient, which should succeed in rekeying"
    sftp = paramiko.sftp_client.SFTPClient.from_transport(transport)
    
    count = 0
    while True:
        with sftp.file(DATAFILE) as stdout:
            rekey = False
            for line in stdout:
                if not rekey:
                    if transport.packetizer.need_rekey():
                        print "Need rekey"
                        rekey = True
        count += 1
        print "Read file {} times".format(count)
        time.sleep(2)