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374 lines
11 KiB
374 lines
11 KiB
# Copyright 2014 The Android Open Source Project
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#
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# Licensed under the Apache License, Version 2.0 (the "License");
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# you may not use this file except in compliance with the License.
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# You may obtain a copy of the License at
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#
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# http://www.apache.org/licenses/LICENSE-2.0
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#
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# Unless required by applicable law or agreed to in writing, software
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# distributed under the License is distributed on an "AS IS" BASIS,
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# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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# See the License for the specific language governing permissions and
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# limitations under the License.
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"""Python wrapper for C socket calls and data structures."""
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import ctypes
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import ctypes.util
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import os
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import re
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import socket
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import struct
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import cstruct
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import util
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# Data structures.
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# These aren't constants, they're classes. So, pylint: disable=invalid-name
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CMsgHdr = cstruct.Struct("cmsghdr", "@Lii", "len level type")
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Iovec = cstruct.Struct("iovec", "@PL", "base len")
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MsgHdr = cstruct.Struct("msghdr", "@LLPLPLi",
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"name namelen iov iovlen control msg_controllen flags")
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SockaddrIn = cstruct.Struct("sockaddr_in", "=HH4sxxxxxxxx", "family port addr")
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SockaddrIn6 = cstruct.Struct("sockaddr_in6", "=HHI16sI",
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"family port flowinfo addr scope_id")
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SockaddrStorage = cstruct.Struct("sockaddr_storage", "=H126s", "family data")
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SockExtendedErr = cstruct.Struct("sock_extended_err", "@IBBBxII",
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"errno origin type code info data")
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InPktinfo = cstruct.Struct("in_pktinfo", "@i4s4s", "ifindex spec_dst addr")
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In6Pktinfo = cstruct.Struct("in6_pktinfo", "@16si", "addr ifindex")
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# Constants.
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# IPv4 socket options and cmsg types.
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IP_TTL = 2
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IP_MTU_DISCOVER = 10
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IP_PKTINFO = 8
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IP_RECVERR = 11
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IP_RECVTTL = 12
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IP_MTU = 14
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# IPv6 socket options and cmsg types.
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IPV6_MTU_DISCOVER = 23
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IPV6_RECVERR = 25
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IPV6_RECVPKTINFO = 49
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IPV6_PKTINFO = 50
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IPV6_RECVHOPLIMIT = 51
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IPV6_HOPLIMIT = 52
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IPV6_PATHMTU = 61
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IPV6_DONTFRAG = 62
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# PMTUD values.
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IP_PMTUDISC_DO = 1
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CMSG_ALIGNTO = struct.calcsize("@L") # The kernel defines this as sizeof(long).
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# Sendmsg flags
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MSG_CONFIRM = 0X800
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MSG_ERRQUEUE = 0x2000
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# Linux errqueue API.
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SO_ORIGIN_ICMP = 2
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SO_ORIGIN_ICMP6 = 3
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# Find the C library.
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libc = ctypes.CDLL(ctypes.util.find_library("c"), use_errno=True)
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# TODO: Unlike most of this file, these functions aren't specific to wrapping C
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# library calls. Move them to a utils.py or constants.py file, once we have one.
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def LinuxVersion():
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# Example: "3.4.67-00753-gb7a556f", "4.4.135+".
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# Get the prefix consisting of digits and dots.
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version = re.search("^[0-9.]*", os.uname()[2]).group()
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# Convert it into a tuple such as (3, 4, 67). That allows comparing versions
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# using < and >, since tuples are compared lexicographically.
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version = tuple(int(i) for i in version.split("."))
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return version
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def AddressVersion(addr):
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return 6 if ":" in addr else 4
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def SetSocketTimeout(sock, ms):
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s = ms / 1000
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us = (ms % 1000) * 1000
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sock.setsockopt(socket.SOL_SOCKET, socket.SO_RCVTIMEO,
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struct.pack("LL", s, us))
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def VoidPointer(s):
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return ctypes.cast(s.CPointer(), ctypes.c_void_p)
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def MaybeRaiseSocketError(ret):
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if ret < 0:
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errno = ctypes.get_errno()
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raise socket.error(errno, os.strerror(errno))
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def Sockaddr(addr):
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if ":" in addr[0]:
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family = socket.AF_INET6
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if len(addr) == 4:
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addr, port, flowinfo, scope_id = addr
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else:
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(addr, port), flowinfo, scope_id = addr, 0, 0
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addr = socket.inet_pton(family, addr)
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return SockaddrIn6((family, socket.ntohs(port), socket.ntohl(flowinfo),
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addr, scope_id))
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else:
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family = socket.AF_INET
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addr, port = addr
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addr = socket.inet_pton(family, addr)
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return SockaddrIn((family, socket.ntohs(port), addr))
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def _MakeMsgControl(optlist):
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"""Creates a msg_control blob from a list of cmsg attributes.
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Takes a list of cmsg attributes. Each attribute is a tuple of:
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- level: An integer, e.g., SOL_IPV6.
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- type: An integer, the option identifier, e.g., IPV6_HOPLIMIT.
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- data: The option data. This is either a string or an integer. If it's an
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integer it will be written as an unsigned integer in host byte order. If
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it's a string, it's used as is.
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Data is padded to an integer multiple of CMSG_ALIGNTO.
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Args:
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optlist: A list of tuples describing cmsg options.
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Returns:
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A string, a binary blob usable as the control data for a sendmsg call.
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Raises:
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TypeError: Option data is neither an integer nor a string.
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"""
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msg_control = ""
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for i, opt in enumerate(optlist):
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msg_level, msg_type, data = opt
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if isinstance(data, int):
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data = struct.pack("=I", data)
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elif isinstance(data, ctypes.c_uint32):
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data = struct.pack("=I", data.value)
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elif not isinstance(data, str):
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raise TypeError("unknown data type for opt (%d, %d): %s" % (
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msg_level, msg_type, type(data)))
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datalen = len(data)
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msg_len = len(CMsgHdr) + datalen
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padding = "\x00" * util.GetPadLength(CMSG_ALIGNTO, datalen)
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msg_control += CMsgHdr((msg_len, msg_level, msg_type)).Pack()
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msg_control += data + padding
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return msg_control
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def _ParseMsgControl(buf):
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"""Parse a raw control buffer into a list of tuples."""
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msglist = []
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while len(buf) > 0:
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cmsghdr, buf = cstruct.Read(buf, CMsgHdr)
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datalen = cmsghdr.len - len(CMsgHdr)
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padlen = util.GetPadLength(CMSG_ALIGNTO, datalen)
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data, buf = buf[:datalen], buf[padlen + datalen:]
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if cmsghdr.level == socket.IPPROTO_IP:
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if cmsghdr.type == IP_PKTINFO:
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data = InPktinfo(data)
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elif cmsghdr.type == IP_TTL:
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data = struct.unpack("@I", data)[0]
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if cmsghdr.level == socket.IPPROTO_IPV6:
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if cmsghdr.type == IPV6_PKTINFO:
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data = In6Pktinfo(data)
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elif cmsghdr.type == IPV6_RECVERR:
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err, source = cstruct.Read(data, SockExtendedErr)
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if err.origin == SO_ORIGIN_ICMP6:
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source, pad = cstruct.Read(source, SockaddrIn6)
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data = (err, source)
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elif cmsghdr.type == IPV6_HOPLIMIT:
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data = struct.unpack("@I", data)[0]
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# If not, leave data as just the raw bytes.
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msglist.append((cmsghdr.level, cmsghdr.type, data))
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return msglist
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def Bind(s, to):
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"""Python wrapper for bind."""
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ret = libc.bind(s.fileno(), VoidPointer(to), len(to))
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MaybeRaiseSocketError(ret)
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return ret
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def Connect(s, to):
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"""Python wrapper for connect."""
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ret = libc.connect(s.fileno(), VoidPointer(to), len(to))
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MaybeRaiseSocketError(ret)
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return ret
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def Sendmsg(s, to, data, control, flags):
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"""Python wrapper for sendmsg.
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Args:
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s: A Python socket object. Becomes sockfd.
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to: An address tuple, or a SockaddrIn[6] struct. Becomes msg->msg_name.
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data: A string, the data to write. Goes into msg->msg_iov.
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control: A list of cmsg options. Becomes msg->msg_control.
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flags: An integer. Becomes msg->msg_flags.
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Returns:
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If sendmsg succeeds, returns the number of bytes written as an integer.
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Raises:
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socket.error: If sendmsg fails.
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"""
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# Create ctypes buffers and pointers from our structures. We need to hang on
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# to the underlying Python objects, because we don't want them to be garbage
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# collected and freed while we have C pointers to them.
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# Convert the destination address into a struct sockaddr.
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if to:
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if isinstance(to, tuple):
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to = Sockaddr(to)
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msg_name = to.CPointer()
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msg_namelen = len(to)
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else:
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msg_name = 0
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msg_namelen = 0
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# Convert the data to a data buffer and a struct iovec pointing at it.
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if data:
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databuf = ctypes.create_string_buffer(data)
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iov = Iovec((ctypes.addressof(databuf), len(data)))
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msg_iov = iov.CPointer()
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msg_iovlen = 1
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else:
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msg_iov = 0
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msg_iovlen = 0
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# Marshal the cmsg options.
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if control:
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control = _MakeMsgControl(control)
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controlbuf = ctypes.create_string_buffer(control)
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msg_control = ctypes.addressof(controlbuf)
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msg_controllen = len(control)
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else:
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msg_control = 0
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msg_controllen = 0
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# Assemble the struct msghdr.
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msghdr = MsgHdr((msg_name, msg_namelen, msg_iov, msg_iovlen,
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msg_control, msg_controllen, flags)).Pack()
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# Call sendmsg.
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ret = libc.sendmsg(s.fileno(), msghdr, 0)
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MaybeRaiseSocketError(ret)
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return ret
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def _ToSocketAddress(addr, alen):
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addr = addr[:alen]
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# Attempt to convert the address to something we understand.
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if alen == 0:
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return None
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elif alen == len(SockaddrIn) and SockaddrIn(addr).family == socket.AF_INET:
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return SockaddrIn(addr)
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elif alen == len(SockaddrIn6) and SockaddrIn6(addr).family == socket.AF_INET6:
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return SockaddrIn6(addr)
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elif alen == len(SockaddrStorage): # Can this ever happen?
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return SockaddrStorage(addr)
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else:
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return addr # Unknown or malformed. Return the raw bytes.
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def Recvmsg(s, buflen, controllen, flags, addrlen=len(SockaddrStorage)):
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"""Python wrapper for recvmsg.
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Args:
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s: A Python socket object. Becomes sockfd.
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buflen: An integer, the maximum number of bytes to read.
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addrlen: An integer, the maximum size of the source address.
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controllen: An integer, the maximum size of the cmsg buffer.
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Returns:
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A tuple of received bytes, socket address tuple, and cmg list.
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Raises:
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socket.error: If recvmsg fails.
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"""
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addr = ctypes.create_string_buffer(addrlen)
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msg_name = ctypes.addressof(addr)
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msg_namelen = addrlen
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buf = ctypes.create_string_buffer(buflen)
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iov = Iovec((ctypes.addressof(buf), buflen))
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msg_iov = iov.CPointer()
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msg_iovlen = 1
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control = ctypes.create_string_buffer(controllen)
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msg_control = ctypes.addressof(control)
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msg_controllen = controllen
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msghdr = MsgHdr((msg_name, msg_namelen, msg_iov, msg_iovlen,
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msg_control, msg_controllen, flags))
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ret = libc.recvmsg(s.fileno(), VoidPointer(msghdr), flags)
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MaybeRaiseSocketError(ret)
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data = buf.raw[:ret]
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msghdr = MsgHdr(str(msghdr._buffer.raw))
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addr = _ToSocketAddress(addr, msghdr.namelen)
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control = control.raw[:msghdr.msg_controllen]
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msglist = _ParseMsgControl(control)
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return data, addr, msglist
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def Recvfrom(s, size, flags=0):
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"""Python wrapper for recvfrom."""
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buf = ctypes.create_string_buffer(size)
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addr = ctypes.create_string_buffer(len(SockaddrStorage))
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alen = ctypes.c_int(len(addr))
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ret = libc.recvfrom(s.fileno(), buf, len(buf), flags,
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addr, ctypes.byref(alen))
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MaybeRaiseSocketError(ret)
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data = buf[:ret]
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alen = alen.value
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addr = _ToSocketAddress(addr.raw, alen)
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return data, addr
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def Setsockopt(s, level, optname, optval, optlen):
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"""Python wrapper for setsockopt.
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Mostly identical to the built-in setsockopt, but allows passing in arbitrary
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binary blobs, including NULL options, which the built-in python setsockopt does
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not allow.
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Args:
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s: The socket object on which to set the option.
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level: The level parameter.
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optname: The option to set.
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optval: A raw byte string, the value to set the option to (None for NULL).
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optlen: An integer, the length of the option.
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Raises:
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socket.error: if setsockopt fails.
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"""
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ret = libc.setsockopt(s.fileno(), level, optname, optval, optlen)
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MaybeRaiseSocketError(ret)
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