little script to test getaddrinfo resolver

resolve.py

#! /usr/bin/env python

from __future__ import print_function

import argparse
import socket
import six


def parse_args():
	parser = argparse.ArgumentParser()
	parser.add_argument(
		'-6', '--ipv6', dest='ipv6', default=None, action='store_true', help='enable IPv6-only lookups (default=both)',
	)
	parser.add_argument(
		'--no-ipv6', dest='ipv6', action='store_false', help='disable IPv6 lookups',
	)
	parser.add_argument(
		'-4', '--ipv4', dest='ipv4', default=None, action='store_true', help='enable IPv4-only lookups (default=both)',
	)
	parser.add_argument(
		'--no-ipv4', dest='ipv4', action='store_false', help='disable IPv4 lookups',
	)
	parser.add_argument(
		'-s', '--socktype', dest='socktype', nargs=1, type=six.text_type, help='socket type (stream, dgram, ...)',
	)
	parser.add_argument(
		'-p', '--proto', '--protocol', nargs=1, dest='proto', type=six.text_type, help='protocol (udp, tcp, ...)',
	)
	parser.add_argument('host', type=str, help='hostname to resolve')
	parser.add_argument('port', nargs='?', type=str, help='port to resolve')
	args = parser.parse_args()
	return args


def resolve_socktype(socktype_arg):
	sock = getattr(socket, 'SOCK_' + proto.upper(), None)
	if not sock:
		raise AttributeError('Unknown socket type: {}'.format(socktype_arg))
	return sock


def print_sockaddr(sockaddr, numeric=False):
	print("ip_addr=   {}".format(sockaddr[0]))
	if numeric:
		print("port=      {}".format(sockaddr[1]))
	else:
		try:
			serv = socket.getservbyport(sockaddr[1])
			print("serv=      {} ({})".format(serv, sockaddr[1]))
		except socket.error:
			print("port=      {}".format(sockaddr[1]))

	if len(sockaddr) > 2:
		print("scope=     {}".format(sockaddr[2]))


def get_family_by_id(family):
	for key in socket.__all__:
		if key.startswith('AF_') and getattr(socket, key) == family:
			return key
	return family


def get_socktype_by_id(socktype):
	for key in socket.__all__:
		if key.startswith('SOCK_') and getattr(socket, key) == socktype:
			return key
	return socktype


def print_addr(addr, numeric=False):
	family, socktype, proto, canonname, sockaddr = addr
	if numeric:
		print("family=    {}".format(family))
		print("socktype=  {}".format(socktype))
	else:
		print("family=    {} ({})".format(get_family_by_id(family), family))
		print("socktype=  {} ({})".format(get_socktype_by_id(socktype), socktype))
	if canonname:
		print("canonname= {}".format(canonname))
	print_sockaddr(sockaddr)


def print_addrs(addrs):
	for i, addr in enumerate(addrs):
		if i:
			print('')
		print_addr(addr)


def main():
	args = parse_args()
	ipv4 = getattr(args, 'ipv4', None)
	ipv6 = getattr(args, 'ipv6', None)

	host = args.host
	port = args.port

	# defaults are a little weird:
	# - when nothing is specified, you get v4 and v6
	# - when one of either ipv4 or ipv6 is specified, you only get addresses of that type
	# - when both are specified, you get addresses of both types
	# POLA violation:
	# - when you disable both v4 and v6, you (again) get all addresses
	#
	# Command line switches are evaluated in order, so --ipv6 --no-ipv6 gives you ipv4 addreses only.
	if (ipv4 or ipv4 is None) and not ipv6:
		family = socket.AF_INET
	elif (ipv6 or ipv6 is None) and not ipv4:
		family = socket.AF_INET6
	else:
		family = socket.AF_UNSPEC


	if getattr(args, 'socktype', None):
		socktype = resolve_socktype(args.socktype[0])
	else:
		socktype = 0

	if getattr(args, 'proto', None):
		proto = socket.getprotobyname(args.proto[0])
	else:
		proto = 0

	addrs = socket.getaddrinfo(host, port, family, socktype, proto)
	print_addrs(addrs)


if __name__ == '__main__':
	main()