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| Dir : //proc/self/root/opt/saltstack/salt/extras-3.10/pyroute2/ext/rawsocket.py |
import struct
from ctypes import (
Structure,
addressof,
c_ubyte,
c_uint,
c_ushort,
c_void_p,
sizeof,
string_at,
)
from socket import AF_PACKET, SOCK_RAW, SOL_SOCKET, errno, error, htons, socket
from pyroute2.iproute.linux import IPRoute
ETH_P_ALL = 3
SO_ATTACH_FILTER = 26
SO_DETACH_FILTER = 27
total_filter = [[0x06, 0, 0, 0]]
class sock_filter(Structure):
_fields_ = [
('code', c_ushort), # u16
('jt', c_ubyte), # u8
('jf', c_ubyte), # u8
('k', c_uint),
] # u32
class sock_fprog(Structure):
_fields_ = [('len', c_ushort), ('filter', c_void_p)]
def compile_bpf(code):
ProgramType = sock_filter * len(code)
program = ProgramType(*[sock_filter(*line) for line in code])
sfp = sock_fprog(len(code), addressof(program[0]))
return string_at(addressof(sfp), sizeof(sfp)), program
class RawSocket(socket):
'''
This raw socket binds to an interface and optionally installs a BPF
filter.
When created, the socket's buffer is cleared to remove packets that
arrived before bind() or the BPF filter is installed. Doing so
requires calling recvfrom() which may raise an exception if the
interface is down.
In order to allow creating the socket when the interface is
down, the ENETDOWN exception is caught and discarded.
'''
fprog = None
def __init__(self, ifname, bpf=None):
self.ifname = ifname
# lookup the interface details
with IPRoute() as ip:
for link in ip.get_links():
if link.get_attr('IFLA_IFNAME') == ifname:
break
else:
raise IOError(2, 'Link not found')
self.l2addr = link.get_attr('IFLA_ADDRESS')
self.ifindex = link['index']
# bring up the socket
socket.__init__(self, AF_PACKET, SOCK_RAW, htons(ETH_P_ALL))
socket.bind(self, (self.ifname, ETH_P_ALL))
if bpf:
self.clear_buffer()
fstring, self.fprog = compile_bpf(bpf)
socket.setsockopt(self, SOL_SOCKET, SO_ATTACH_FILTER, fstring)
else:
self.clear_buffer(remove_total_filter=True)
def clear_buffer(self, remove_total_filter=False):
# there is a window of time after the socket has been created and
# before bind/attaching a filter where packets can be queued onto the
# socket buffer
# see comments in function set_kernel_filter() in libpcap's
# pcap-linux.c. libpcap sets a total filter which does not match any
# packet. It then clears what is already in the socket
# before setting the desired filter
total_fstring, prog = compile_bpf(total_filter)
socket.setsockopt(self, SOL_SOCKET, SO_ATTACH_FILTER, total_fstring)
self.setblocking(0)
while True:
try:
self.recvfrom(0)
except error as e:
if e.args[0] == errno.ENETDOWN:
# we only get this exception once per down event
# there may be more packets left to clean
pass
elif e.args[0] in [errno.EAGAIN, errno.EWOULDBLOCK]:
break
else:
raise
self.setblocking(1)
if remove_total_filter:
# total_fstring ignored
socket.setsockopt(
self, SOL_SOCKET, SO_DETACH_FILTER, total_fstring
)
def csum(self, data):
if len(data) % 2:
data += b'\x00'
csum = sum(
[
struct.unpack('>H', data[x * 2 : x * 2 + 2])[0]
for x in range(len(data) // 2)
]
)
csum = (csum >> 16) + (csum & 0xFFFF)
csum += csum >> 16
return ~csum & 0xFFFF