Convert dd-wrt's forward_spec to OpenWrt's redirct rules suitable for /etc/network/firewall

convert_forward_spec_to_openwrt.py

"""
Convert dd-wrt's forward_spec from 'nvram get forward_spec' to OpenWrt's 
redirect rules suitable for /etc/network/firewall
"""
from io import StringIO
import re

# example forward line taken from 'nvram get forward_spec' on a dd-wrt router
forward_spec=r"https:on:tcp:443>192.168.1.201:443 ssh:on:tcp:22>192.168.1.202:22 ssh2:off:tcp:23>192.168.1.117:22"


def process_forward_spec(forward_spec):
    b=StringIO()
    for spec in forward_spec.split(' '):
        name, enabled, proto, src_port, dst, dst_port = re.split(':|>', spec)
        b.write(f'\nconfig redirect\n'
                f"\toption target 'DNAT'\n"
                f"\toption name '{name}'\n"
                f"\tlist proto '{proto}'\n"
                f"\toption src 'wan'\n"
                f"\toption src_dport '{src_port}'\n"
                f"\toption dest 'lan'\n"
                f"\toption dest_ip '{dst}'\n"
                f"\toption dest_port '{dst_port}'\n")
        if not enabled=='on':`
            b.write(f"\toption enabled '0'\n")
    return b.getvalue()


if __name__=='__main__':
    print(process_forward_spec(forward_spec))