# Copyright (c) Twisted Matrix Laboratories.
# See LICENSE for details.

"""
POSIX implementation of local network interface enumeration.
"""

from __future__ import division, absolute_import

import sys, socket

from socket import AF_INET, AF_INET6, inet_ntop
from ctypes import (
CDLL, POINTER, Structure, c_char_p, c_ushort, c_int,
c_uint32, c_uint8, c_void_p, c_ubyte, pointer, cast)
from ctypes.util import find_library

from twisted.python.compat import _PY3, nativeString

if _PY3:
# Once #6070 is implemented, this can be replaced with the implementation
# from that ticket:
def chr(i):
"""
Python 3 implementation of Python 2 chr(), i.e. convert an integer to
corresponding byte.
"""
return bytes([i])


libc = CDLL(find_library("c"))

if sys.platform == 'darwin':
_sockaddrCommon = [
("sin_len", c_uint8),
("sin_family", c_uint8),
]
else:
_sockaddrCommon = [
("sin_family", c_ushort),
]



class in_addr(Structure):
_fields_ = [
("in_addr", c_ubyte * 4),
]



class in6_addr(Structure):
_fields_ = [
("in_addr", c_ubyte * 16),
]



class sockaddr(Structure):
_fields_ = _sockaddrCommon + [
("sin_port", c_ushort),
]



class sockaddr_in(Structure):
_fields_ = _sockaddrCommon + [
("sin_port", c_ushort),
("sin_addr", in_addr),
]



class sockaddr_in6(Structure):
_fields_ = _sockaddrCommon + [
("sin_port", c_ushort),
("sin_flowinfo", c_uint32),
("sin_addr", in6_addr),
]



class ifaddrs(Structure):
pass

ifaddrs_p = POINTER(ifaddrs)
ifaddrs._fields_ = [
('ifa_next', ifaddrs_p),
('ifa_name', c_char_p),
('ifa_flags', c_uint32),
('ifa_addr', POINTER(sockaddr)),
('ifa_netmask', POINTER(sockaddr)),
('ifa_dstaddr', POINTER(sockaddr)),
('ifa_data', c_void_p)]

getifaddrs = libc.getifaddrs
getifaddrs.argtypes = [POINTER(ifaddrs_p)]
getifaddrs.restype = c_int

freeifaddrs = libc.freeifaddrs
freeifaddrs.argtypes = [ifaddrs_p]

def _interfaces():
"""
Call C{getifaddrs(3)} and return a list of tuples of interface name, address
family, and human-readable address representing its results.
"""
ifaddrs = ifaddrs_p()
if getifaddrs(pointer(ifaddrs)) < 0:
raise OSError()
results = []
try:
while ifaddrs:
if ifaddrs[0].ifa_addr:
family = ifaddrs[0].ifa_addr[0].sin_family
if family == AF_INET:
addr = cast(ifaddrs[0].ifa_addr, POINTER(sockaddr_in))
elif family == AF_INET6:
addr = cast(ifaddrs[0].ifa_addr, POINTER(sockaddr_in6))
else:
addr = None

if addr:
packed = b''.join(map(chr, addr[0].sin_addr.in_addr[:]))
results.append((
ifaddrs[0].ifa_name,
family,
inet_ntop(family, packed)))

ifaddrs = ifaddrs[0].ifa_next
finally:
freeifaddrs(ifaddrs)
return results



def posixGetLinkLocalIPv6Addresses():
"""
Return a list of strings in colon-hex format representing all the link local
IPv6 addresses available on the system, as reported by I{getifaddrs(3)}.
"""
retList = []
for (interface, family, address) in _interfaces():
interface = nativeString(interface)
address = nativeString(address)
if family == socket.AF_INET6 and address.startswith('fe80:'):
retList.append('%s%%%s' % (address, interface))
return retList