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#
# This file is part of pysnmp software.
#
# Copyright (c) 2005-2020, Ilya Etingof <etingof@gmail.com>
# License: https://www.pysnmp.com/pysnmp/license.html
#
# The following routines act like sendto()/recvfrom() calls but additionally
# support local address retrieval (what can be useful when listening on
# 0.0.0.0 or [::]) and source address spoofing (for transparent proxying).
#
# These routines are based on POSIX sendmsg()/recvmsg() calls which were made
# available since Python 3.3. Therefore this module is only Python 3.x
# compatible.
#
# Parts of the code below is taken from:
# http://carnivore.it/2012/10/12/python3.3_sendmsg_and_recvmsg
#
import ctypes
import ipaddress
import socket
from pysnmp import debug
uint32_t = ctypes.c_uint32
in_addr_t = uint32_t
class in_addr(ctypes.Structure): # noqa: N801
"""Represent an IPv4 address."""
_fields_ = [("s_addr", in_addr_t)]
class in6_addr_U(ctypes.Union): # noqa: N801
"""Represent an IPv6 address."""
_fields_ = [
("__u6_addr8", ctypes.c_uint8 * 16),
("__u6_addr16", ctypes.c_uint16 * 8),
("__u6_addr32", ctypes.c_uint32 * 4),
]
class in6_addr(ctypes.Structure): # noqa: N801
"""Represent an IPv6 address."""
_fields_ = [
("__in6_u", in6_addr_U),
]
class in_pktinfo(ctypes.Structure): # noqa: N801
"""Represent an IPv4 packet information."""
_fields_ = [
("ipi_ifindex", ctypes.c_int),
("ipi_spec_dst", in_addr),
("ipi_addr", in_addr),
]
class in6_pktinfo(ctypes.Structure): # noqa: N801
"""Represent an IPv6 packet information."""
_fields_ = [
("ipi6_addr", in6_addr),
("ipi6_ifindex", ctypes.c_uint),
]
def get_recvfrom(addressType):
"""Return a function that receives data from a socket and returns the data and the address of the sender.
The address is an instance of addressType.
"""
def recvfrom(s, sz):
_to = None
data, ancdata, msg_flags, _from = s.recvmsg(sz, socket.CMSG_LEN(sz))
for anc in ancdata:
if anc[0] == socket.SOL_IP and anc[1] == socket.IP_PKTINFO:
addr = in_pktinfo.from_buffer_copy(anc[2])
addr = ipaddress.IPv4Address(memoryview(addr.ipi_addr).tobytes())
_to = (str(addr), s.getsockname()[1])
break
elif anc[0] == socket.SOL_IPV6 and anc[1] == socket.IPV6_PKTINFO:
addr = in6_pktinfo.from_buffer_copy(anc[2])
addr = ipaddress.ip_address(memoryview(addr.ipi6_addr).tobytes())
_to = (str(addr), s.getsockname()[1])
break
debug.logger & debug.FLAG_IO and debug.logger(
"recvfrom: received %d octets from %s to %s; "
"iov blob %r" % (len(data), _from, _to, ancdata)
)
return data, addressType(_from).setLocalAddress(_to)
return recvfrom
def get_sendto(addressType):
"""Return a function that sends data to a socket and returns the number of bytes sent.
The address is an instance of addressType.
"""
def sendto(s, _data, _to):
ancdata = []
if isinstance(_to, addressType):
addr = ipaddress.ip_address(_to.getLocalAddress()[0])
else:
addr = ipaddress.ip_address(s.getsockname()[0])
if isinstance(addr, ipaddress.IPv4Address):
_f = in_pktinfo()
_f.ipi_spec_dst = in_addr.from_buffer_copy(addr.packed)
ancdata = [(socket.SOL_IP, socket.IP_PKTINFO, memoryview(_f).tobytes())]
elif s.family == socket.AF_INET6 and isinstance(addr, ipaddress.IPv6Address):
_f = in6_pktinfo()
_f.ipi6_addr = in6_addr.from_buffer_copy(addr.packed)
ancdata = [(socket.SOL_IPV6, socket.IPV6_PKTINFO, memoryview(_f).tobytes())]
debug.logger & debug.FLAG_IO and debug.logger(
"sendto: sending %d octets to %s; address %r; "
"iov blob %r" % (len(_data), _to, addr, ancdata)
)
return s.sendmsg([_data], ancdata, 0, _to)
return sendto
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