'''
Netlink message generation/parsing
Copyright 2007 Johannes Berg <johannes@sipsolutions.net>
GPLv2+; See copying for details.
'''
import os
import socket
import struct
try:
# try to use python 2.5's netlink support
_dummysock = socket.socket(socket.AF_NETLINK, socket.SOCK_RAW, 0)
_dummysock.bind((0, 0))
del _dummysock
def _nl_bind(descriptor, addr):
descriptor.bind(addr)
def _nl_getsockname(descriptor):
return descriptor.getsockname()
def _nl_send(descriptor, msg):
descriptor.send(msg)
def _nl_recv(descriptor, bufs=16384):
return descriptor.recvfrom(bufs)
except socket.error:
# or fall back to the _netlink C module
try:
import _netlink
def _nl_bind(descriptor, addr):
_netlink.bind(descriptor.fileno(), addr[1])
def _nl_getsockname(descriptor):
return _netlink.getsockname(descriptor.fileno())
def _nl_send(descriptor, msg):
_netlink.send(descriptor.fileno(), msg)
def _nl_recv(descriptor, bufs=16384):
return _netlink.recvfrom(descriptor.fileno(), bufs)
except ImportError:
# or fall back to the ctypes module
import ctypes
libc = ctypes.CDLL(None)
class SOCKADDR_NL(ctypes.Structure):
_fields_ = [("nl_family", ctypes.c_ushort),
("nl_pad", ctypes.c_ushort),
("nl_pid", ctypes.c_int),
("nl_groups", ctypes.c_int)]
def _nl_bind(descriptor, addr):
addr = SOCKADDR_NL(socket.AF_NETLINK, 0, os.getpid(), 0)
return libc.bind(descriptor.fileno(),
ctypes.pointer(addr),
ctypes.sizeof(addr))
def _nl_getsockname(descriptor):
addr = SOCKADDR_NL(0, 0, 0, 0)
len = ctypes.c_int(ctypes.sizeof(addr));
libc.getsockname(descriptor.fileno(),
ctypes.pointer(addr),
ctypes.pointer(len))
return addr.nl_pid, addr.nl_groups;
def _nl_send(descriptor, msg):
return libc.send(descriptor.fileno(), msg, len(msg), 0);
def _nl_recv(descriptor, bufs=16384):
addr = SOCKADDR_NL(0, 0, 0, 0)
len = ctypes.c_int(ctypes.sizeof(addr))
buf = ctypes.create_string_buffer(bufs)
r = libc.recvfrom(descriptor.fileno(),
buf, bufs, 0,
ctypes.pointer(addr), ctypes.pointer(len))
ret = ctypes.string_at(ctypes.pointer(buf), r)
return ret, (addr.nl_pid, addr.nl_groups)
# flags
NLM_F_REQUEST = 1
NLM_F_MULTI = 2
NLM_F_ACK = 4
NLM_F_ECHO = 8
# types
NLMSG_NOOP = 1
NLMSG_ERROR = 2
NLMSG_DONE = 3
NLMSG_OVERRUN = 4
NLMSG_MIN_TYPE = 0x10
class Attr:
def __init__(self, attr_type, data, *values):
self.type = attr_type
if len(values):
self.data = struct.pack(data, *values)
else:
self.data = data
def _dump(self):
hdr = struct.pack("HH", len(self.data)+4, self.type)
length = len(self.data)
pad = ((length + 4 - 1) & ~3 ) - length
return hdr + self.data + b'\0' * pad
def __repr__(self):
return '<Attr type %d, data "%s">' % (self.type, repr(self.data))
def u16(self):
return struct.unpack('H', self.data)[0]
def s16(self):
return struct.unpack('h', self.data)[0]
def u32(self):
return struct.unpack('I', self.data)[0]
def s32(self):
return struct.unpack('i', self.data)[0]
def str(self):
return self.data
def nulstr(self):
return self.data.split('\0')[0]
def nested(self):
return parse_attributes(self.data)
class StrAttr(Attr):
def __init__(self, attr_type, data):
Attr.__init__(self, attr_type, "%ds" % len(data), data.encode('utf-8'))
class NulStrAttr(Attr):
def __init__(self, attr_type, data):
Attr.__init__(self, attr_type, "%dsB" % len(data), data.encode('utf-8'), 0)
class U32Attr(Attr):
def __init__(self, attr_type, val):
Attr.__init__(self, attr_type, "I", val)
class U8Attr(Attr):
def __init__(self, attr_type, val):
Attr.__init__(self, attr_type, "B", val)
class Nested(Attr):
def __init__(self, attr_type, attrs):
self.attrs = attrs
self.type = attr_type
def _dump(self):
contents = []
for attr in self.attrs:
contents.append(attr._dump())
contents = ''.join(contents)
length = len(contents)
hdr = struct.pack("HH", length+4, self.type)
return hdr + contents
NETLINK_ROUTE = 0
NETLINK_UNUSED = 1
NETLINK_USERSOCK = 2
NETLINK_FIREWALL = 3
NETLINK_INET_DIAG = 4
NETLINK_NFLOG = 5
NETLINK_XFRM = 6
NETLINK_SELINUX = 7
NETLINK_ISCSI = 8
NETLINK_AUDIT = 9
NETLINK_FIB_LOOKUP = 10
NETLINK_CONNECTOR = 11
NETLINK_NETFILTER = 12
NETLINK_IP6_FW = 13
NETLINK_DNRTMSG = 14
NETLINK_KOBJECT_UEVENT = 15
NETLINK_GENERIC = 16
class Message:
def __init__(self, msg_type, flags=0, seq=-1, payload=None):
self.type = msg_type
self.flags = flags
self.seq = seq
self.pid = -1
payload = payload or []
if isinstance(payload, list):
contents = []
for attr in payload:
contents.append(attr._dump())
self.payload = b''.join(contents)
else:
self.payload = payload
def send(self, conn):
if self.seq == -1:
self.seq = conn.seq()
self.pid = conn.pid
length = len(self.payload)
hdr = struct.pack("IHHII", length + 4*4, self.type,
self.flags, self.seq, self.pid)
conn.send(hdr + self.payload)
def __repr__(self):
return '<netlink.Message type=%d, pid=%d, seq=%d, flags=0x%x "%s">' % (
self.type, self.pid, self.seq, self.flags, repr(self.payload))
class Connection:
def __init__(self, nltype, groups=0, unexpected_msg_handler=None):
self.descriptor = socket.socket(socket.AF_NETLINK,
socket.SOCK_RAW, nltype)
self.descriptor.setsockopt(socket.SOL_SOCKET, socket.SO_SNDBUF, 65536)
self.descriptor.setsockopt(socket.SOL_SOCKET, socket.SO_RCVBUF, 65536)
_nl_bind(self.descriptor, (0, groups))
self.pid, self.groups = _nl_getsockname(self.descriptor)
self._seq = 0
self.unexpected = unexpected_msg_handler
def send(self, msg):
_nl_send(self.descriptor, msg)
def recv(self):
contents, (nlpid, nlgrps) = _nl_recv(self.descriptor)
# XXX: python doesn't give us message flags, check
# len(contents) vs. msglen for TRUNC
msglen, msg_type, flags, seq, pid = struct.unpack("IHHII",
contents[:16])
msg = Message(msg_type, flags, seq, contents[16:])
msg.pid = pid
if msg.type == NLMSG_ERROR:
errno = -struct.unpack("i", msg.payload[:4])[0]
if errno != 0:
err = OSError("Netlink error: %s (%d)" % (
os.strerror(errno), errno))
err.errno = errno
raise err
return msg
def seq(self):
self._seq += 1
return self._seq
def parse_attributes(data):
attrs = {}
while len(data):
attr_len, attr_type = struct.unpack("HH", data[:4])
attrs[attr_type] = Attr(attr_type, data[4:attr_len])
attr_len = ((attr_len + 4 - 1) & ~3 )
data = data[attr_len:]
return attrs