The code is a bit longer than I typically like to include in a blog post, but here it goes:
"""As always, this code is released under a BSD-style license.
Wrapper for getifaddrs(3).
"""
import socket
import sys
from collections import namedtuple
from ctypes import *
class sockaddr_in(Structure):
_fields_ = [
('sin_len', c_uint8),
('sin_family', c_uint8),
('sin_port', c_uint16),
('sin_addr', c_uint8 * 4),
('sin_zero', c_uint8 * 8)
]
def __str__(self):
assert self.sin_len >= sizeof(sockaddr_in)
data = ''.join(map(chr, self.sin_addr))
return socket.inet_ntop(socket.AF_INET, data)
class sockaddr_in6(Structure):
_fields_ = [
('sin6_len', c_uint8),
('sin6_family', c_uint8),
('sin6_port', c_uint16),
('sin6_flowinfo', c_uint32),
('sin6_addr', c_uint8 * 16),
('sin6_scope_id', c_uint32)
]
def __str__(self):
assert self.sin6_len >= sizeof(sockaddr_in6)
data = ''.join(map(chr, self.sin6_addr))
return socket.inet_ntop(socket.AF_INET6, data)
class sockaddr_dl(Structure):
_fields_ = [
('sdl_len', c_uint8),
('sdl_family', c_uint8),
('sdl_index', c_short),
('sdl_type', c_uint8),
('sdl_nlen', c_uint8),
('sdl_alen', c_uint8),
('sdl_slen', c_uint8),
('sdl_data', c_uint8 * 12)
]
def __str__(self):
assert self.sdl_len >= sizeof(sockaddr_dl)
addrdata = self.sdl_data[self.sdl_nlen:self.sdl_nlen+self.sdl_alen]
return ':'.join('%02x' % x for x in addrdata)
class sockaddr_storage(Structure):
_fields_ = [
('sa_len', c_uint8),
('sa_family', c_uint8),
('sa_data', c_uint8 * 254)
]
class sockaddr(Union):
_anonymous_ = ('sa_storage', )
_fields_ = [
('sa_storage', sockaddr_storage),
('sa_sin', sockaddr_in),
('sa_sin6', sockaddr_in6),
('sa_sdl', sockaddr_dl),
]
def family(self):
return self.sa_storage.sa_family
def __str__(self):
family = self.family()
if family == socket.AF_INET:
return str(self.sa_sin)
elif family == socket.AF_INET6:
return str(self.sa_sin6)
elif family == 18: # AF_LINK
return str(self.sa_sdl)
else:
print family
raise NotImplementedError, "address family %d not supported" % family
class ifaddrs(Structure):
pass
ifaddrs._fields_ = [
('ifa_next', POINTER(ifaddrs)),
('ifa_name', c_char_p),
('ifa_flags', c_uint),
('ifa_addr', POINTER(sockaddr)),
('ifa_netmask', POINTER(sockaddr)),
('ifa_dstaddr', POINTER(sockaddr)),
('ifa_data', c_void_p)
]
# Define constants for the most useful interface flags (from if.h).
IFF_UP = 0x0001
IFF_BROADCAST = 0x0002
IFF_LOOPBACK = 0x0008
IFF_POINTTOPOINT = 0x0010
IFF_RUNNING = 0x0040
if sys.platform == 'darwin' or 'bsd' in sys.platform:
IFF_MULTICAST = 0x8000
elif sys.platform == 'linux':
IFF_MULTICAST = 0x1000
# Load library implementing getifaddrs and freeifaddrs.
if sys.platform == 'darwin':
libc = cdll.LoadLibrary('libc.dylib')
else:
libc = cdll.LoadLibrary('libc.so')
# Tell ctypes the argument and return types for the getifaddrs and
# freeifaddrs functions so it can do marshalling for us.
libc.getifaddrs.argtypes = [POINTER(POINTER(ifaddrs))]
libc.getifaddrs.restype = c_int
libc.freeifaddrs.argtypes = [POINTER(ifaddrs)]
def getifaddrs():
"""
Get local interface addresses.
Returns generator of tuples consisting of interface name, interface flags,
address family (e.g. socket.AF_INET, socket.AF_INET6), address, and netmask.
The tuple members can also be accessed via the names 'name', 'flags',
'family', 'address', and 'netmask', respectively.
"""
# Get address information for each interface.
addrlist = POINTER(ifaddrs)()
if libc.getifaddrs(pointer(addrlist)) < 0:
raise OSError
X = namedtuple('ifaddrs', 'name flags family address netmask')
# Iterate through the address information.
ifaddr = addrlist
while ifaddr and ifaddr.contents:
# The following is a hack to workaround a bug in FreeBSD
# (PR kern/152036) and MacOSX wherein the netmask's sockaddr may be
# truncated. Specifically, AF_INET netmasks may have their sin_addr
# member truncated to the minimum number of bytes necessary to
# represent the netmask. For example, a sockaddr_in with the netmask
# 255.255.254.0 may be truncated to 7 bytes (rather than the normal
# 16) such that the sin_addr field only contains 0xff, 0xff, 0xfe.
# All bytes beyond sa_len bytes are assumed to be zero. Here we work
# around this truncation by copying the netmask's sockaddr into a
# zero-filled buffer.
if ifaddr.contents.ifa_netmask:
netmask = sockaddr()
memmove(byref(netmask), ifaddr.contents.ifa_netmask,
ifaddr.contents.ifa_netmask.contents.sa_len)
if netmask.sa_family == socket.AF_INET and netmask.sa_len < sizeof(sockaddr_in):
netmask.sa_len = sizeof(sockaddr_in)
else:
netmask = None
try:
yield X(ifaddr.contents.ifa_name,
ifaddr.contents.ifa_flags,
ifaddr.contents.ifa_addr.contents.family(),
str(ifaddr.contents.ifa_addr.contents),
str(netmask) if netmask else None)
except NotImplementedError:
# Unsupported address family.
yield X(ifaddr.contents.ifa_name,
ifaddr.contents.ifa_flags,
None,
None,
None)
ifaddr = ifaddr.contents.ifa_next
# When we are done with the address list, ask libc to free whatever memory
# it allocated for the list.
libc.freeifaddrs(addrlist)
__all__ = ['getifaddrs'] + [n for n in dir() if n.startswith('IFF_')]
