mirror of
https://github.com/AuxXxilium/arv-v-dsm.git
synced 2024-11-23 23:10:58 +07:00
81 lines
2.2 KiB
Python
Executable File
81 lines
2.2 KiB
Python
Executable File
#!/usr/bin/env python3
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import argparse
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import ipaddress
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import json
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import re
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import socket
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import subprocess
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from typing import List, Iterable
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DEFAULT_ROUTE = 'default'
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DEFAULT_DNS_IPS = ('8.8.8.8', '8.8.4.4')
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DHCP_CONF_TEMPLATE = """
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start {host_addr}
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end {host_addr}
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# avoid dhcpd complaining that we have
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# too many addresses
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max_leases 1
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interface {dhcp_intf}
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option dns {dns}
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option router {gateway}
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option subnet {subnet}
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option hostname {hostname}
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"""
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def default_route(routes):
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"""Returns the host's default route"""
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for route in routes:
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if route['dst'] == DEFAULT_ROUTE:
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return route
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raise ValueError('no default route')
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def addr_of(addrs, dev : str) -> ipaddress.IPv4Interface:
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"""Finds and returns the IP address of `dev`"""
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for addr in addrs:
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if addr['ifname'] != dev:
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continue
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if len(addr['addr_info']) != 1:
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raise ValueError('only exactly one address on dev is supported')
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info = addr['addr_info'][0]
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return ipaddress.IPv4Interface((info['local'], info['prefixlen']))
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raise ValueError('dev {0} not found'.format(dev))
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def generate_conf(intf_name : str, dns : Iterable[str]) -> str:
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"""Generates a dhcpd config. `intf_name` is the interface to listen on."""
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with subprocess.Popen(['ip', '-json', 'route'],
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stdout=subprocess.PIPE) as proc:
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routes = json.load(proc.stdout)
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with subprocess.Popen(['ip', '-json', 'addr'],
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stdout=subprocess.PIPE) as proc:
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addrs = json.load(proc.stdout)
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droute = default_route(routes)
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host_addr = addr_of(addrs, droute['dev'])
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return DHCP_CONF_TEMPLATE.format(
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dhcp_intf = intf_name,
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dns = ' '.join(dns),
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gateway = droute['gateway'],
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host_addr = host_addr.ip,
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hostname = socket.gethostname(),
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subnet = host_addr.network.netmask,
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)
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if __name__ == '__main__':
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parser = argparse.ArgumentParser()
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parser.add_argument('intf_name')
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parser.add_argument('dns_ips', nargs='*')
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args = parser.parse_args()
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dns_ips = args.dns_ips
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if not dns_ips:
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dns_ips = DEFAULT_DNS_IPS
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print(generate_conf(args.intf_name, dns_ips))
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