Flush file buffer when using stdout

[rafa-br34]

Currently, Masscan does not flush the file buffer when using the -oL - flags. This does not allow other programs (in my case, Python) to easily parse the output stream.

Here's the code I'm using in case anyone wants to reproduce the issue.

import subprocess

def masscan_iterate(path, port, rate=1000):
        process = subprocess.Popen(
                [
                        path,
                        "-oL", "-",
                        "-p", str(port),
                        "--rate", str(rate),
                        "--exclude", "255.255.255.255",
                        "0.0.0.0/0"
                ],
                stdout = subprocess.PIPE,
                stderr = subprocess.DEVNULL
        )

        while process.poll() == None:
                line = process.stdout.readline() # Hangs with the current Masscan version, works with the patch

                if line != b'':
                        print(line)

masscan_iterate("./masscan", 22)