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#!/usr/bin/python
#
# Copyright 2014 The Android Open Source Project
#
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
#
# http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.
"""Partial Python implementation of iproute functionality."""
# pylint: disable=g-bad-todo
import os
import socket
import struct
import sys
import cstruct
import util
### Base netlink constants. See include/uapi/linux/netlink.h.
NETLINK_ROUTE = 0
NETLINK_SOCK_DIAG = 4
NETLINK_XFRM = 6
NETLINK_GENERIC = 16
# Request constants.
NLM_F_REQUEST = 1
NLM_F_ACK = 4
NLM_F_REPLACE = 0x100
NLM_F_EXCL = 0x200
NLM_F_CREATE = 0x400
NLM_F_DUMP = 0x300
# Message types.
NLMSG_ERROR = 2
NLMSG_DONE = 3
# Data structure formats.
# These aren't constants, they're classes. So, pylint: disable=invalid-name
NLMsgHdr = cstruct.Struct("NLMsgHdr", "=LHHLL", "length type flags seq pid")
NLMsgErr = cstruct.Struct("NLMsgErr", "=i", "error")
NLAttr = cstruct.Struct("NLAttr", "=HH", "nla_len nla_type")
# Alignment / padding.
NLA_ALIGNTO = 4
# List of attributes that can appear more than once in a given netlink message.
# These can appear more than once but don't seem to contain any data.
DUP_ATTRS_OK = ["INET_DIAG_NONE", "IFLA_PAD"]
class NetlinkSocket(object):
"""A basic netlink socket object."""
BUFSIZE = 65536
DEBUG = False
# List of netlink messages to print, e.g., [], ["NEIGH", "ROUTE"], or ["ALL"]
NL_DEBUG = []
def _Debug(self, s):
if self.DEBUG:
print(s)
def _NlAttr(self, nla_type, data):
datalen = len(data)
# Pad the data if it's not a multiple of NLA_ALIGNTO bytes long.
padding = "\x00" * util.GetPadLength(NLA_ALIGNTO, datalen)
nla_len = datalen + len(NLAttr)
return NLAttr((nla_len, nla_type)).Pack() + data + padding
def _NlAttrIPAddress(self, nla_type, family, address):
return self._NlAttr(nla_type, socket.inet_pton(family, address))
def _NlAttrStr(self, nla_type, value):
value = value + "\x00"
return self._NlAttr(nla_type, value.encode("UTF-8"))
def _NlAttrU32(self, nla_type, value):
return self._NlAttr(nla_type, struct.pack("=I", value))
def _GetConstantName(self, module, value, prefix):
thismodule = sys.modules[module]
for name in dir(thismodule):
if name.startswith("INET_DIAG_BC"):
continue
if (name.startswith(prefix) and
not name.startswith(prefix + "F_") and
name.isupper() and getattr(thismodule, name) == value):
return name
return value
def _Decode(self, command, msg, nla_type, nla_data):
"""No-op, nonspecific version of decode."""
return nla_type, nla_data
def _ReadNlAttr(self, data):
# Read the nlattr header.
nla, data = cstruct.Read(data, NLAttr)
# Read the data.
datalen = nla.nla_len - len(nla)
padded_len = util.GetPadLength(NLA_ALIGNTO, datalen) + datalen
nla_data, data = data[:datalen], data[padded_len:]
return nla, nla_data, data
def _ParseAttributes(self, command, msg, data, nested=0):
"""Parses and decodes netlink attributes.
Takes a block of NLAttr data structures, decodes them using Decode, and
returns the result in a dict keyed by attribute number.
Args:
command: An integer, the rtnetlink command being carried out.
msg: A Struct, the type of the data after the netlink header.
data: A byte string containing a sequence of NLAttr data structures.
nested: An integer, how deep we're currently nested.
Returns:
A dictionary mapping attribute types (integers) to decoded values.
Raises:
ValueError: There was a duplicate attribute type.
"""
attributes = {}
while data:
nla, nla_data, data = self._ReadNlAttr(data)
# If it's an attribute we know about, try to decode it.
nla_name, nla_data = self._Decode(command, msg, nla.nla_type, nla_data)
if nla_name in attributes and nla_name not in DUP_ATTRS_OK:
raise ValueError("Duplicate attribute %s" % nla_name)
attributes[nla_name] = nla_data
if not nested:
self._Debug(" %s" % (str((nla_name, nla_data))))
return attributes
def _OpenNetlinkSocket(self, family, groups):
sock = socket.socket(socket.AF_NETLINK, socket.SOCK_RAW, family)
if groups:
sock.bind((0, groups))
sock.connect((0, 0)) # The kernel.
return sock
def __init__(self, family, groups=None):
# Global sequence number.
self.seq = 0
self.sock = self._OpenNetlinkSocket(family, groups)
self.pid = self.sock.getsockname()[1]
def MaybeDebugCommand(self, command, flags, data):
# Default no-op implementation to be overridden by subclasses.
pass
def _Send(self, msg):
# self._Debug(msg.encode("hex"))
self.seq += 1
self.sock.send(msg)
def _Recv(self):
data = self.sock.recv(self.BUFSIZE)
# self._Debug(data.encode("hex"))
return data
def _ExpectDone(self):
response = self._Recv()
hdr = NLMsgHdr(response)
if hdr.type != NLMSG_DONE:
raise ValueError("Expected DONE, got type %d" % hdr.type)
def _ParseAck(self, response):
# Find the error code.
hdr, data = cstruct.Read(response, NLMsgHdr)
if hdr.type == NLMSG_ERROR:
error = NLMsgErr(data).error
if error:
raise IOError(-error, os.strerror(-error))
else:
raise ValueError("Expected ACK, got type %d" % hdr.type)
def _ExpectAck(self):
response = self._Recv()
self._ParseAck(response)
def _SendNlRequest(self, command, data, flags):
"""Sends a netlink request and expects an ack."""
length = len(NLMsgHdr) + len(data)
nlmsg = NLMsgHdr((length, command, flags, self.seq, self.pid)).Pack()
self.MaybeDebugCommand(command, flags, nlmsg + data)
# Send the message.
self._Send(nlmsg + data)
if flags & NLM_F_ACK:
self._ExpectAck()
def _ParseNLMsg(self, data, msgtype):
"""Parses a Netlink message into a header and a dictionary of attributes."""
nlmsghdr, data = cstruct.Read(data, NLMsgHdr)
self._Debug(" %s" % nlmsghdr)
if nlmsghdr.type == NLMSG_ERROR or nlmsghdr.type == NLMSG_DONE:
print("done")
return (None, None), data
nlmsg, data = cstruct.Read(data, msgtype)
self._Debug(" %s" % nlmsg)
# Parse the attributes in the nlmsg.
attrlen = nlmsghdr.length - len(nlmsghdr) - len(nlmsg)
attributes = self._ParseAttributes(nlmsghdr.type, nlmsg, data[:attrlen])
data = data[attrlen:]
return (nlmsg, attributes), data
def _GetMsg(self, msgtype):
data = self._Recv()
if NLMsgHdr(data).type == NLMSG_ERROR:
self._ParseAck(data)
return self._ParseNLMsg(data, msgtype)[0]
def _GetMsgList(self, msgtype, data, expect_done):
out = []
while data:
msg, data = self._ParseNLMsg(data, msgtype)
if msg is None:
break
out.append(msg)
if expect_done:
self._ExpectDone()
return out
def _Dump(self, command, msg, msgtype, attrs):
"""Sends a dump request and returns a list of decoded messages.
Args:
command: An integer, the command to run (e.g., RTM_NEWADDR).
msg: A struct, the request (e.g., a RTMsg). May be None.
msgtype: A cstruct.Struct, the data type to parse the dump results as.
attrs: A string, the raw bytes of any request attributes to include.
Returns:
A list of (msg, attrs) tuples where msg is of type msgtype and attrs is
a dict of attributes.
"""
# Create a netlink dump request containing the msg.
flags = NLM_F_DUMP | NLM_F_REQUEST
msg = "" if msg is None else msg.Pack()
length = len(NLMsgHdr) + len(msg) + len(attrs)
nlmsghdr = NLMsgHdr((length, command, flags, self.seq, self.pid))
# Send the request.
request = nlmsghdr.Pack() + msg + attrs
self.MaybeDebugCommand(command, flags, request)
self._Send(request)
# Keep reading netlink messages until we get a NLMSG_DONE.
out = []
while True:
data = self._Recv()
response_type = NLMsgHdr(data).type
if response_type == NLMSG_DONE:
break
elif response_type == NLMSG_ERROR:
# Likely means that the kernel didn't like our dump request.
# Parse the error and throw an exception.
self._ParseAck(data)
out.extend(self._GetMsgList(msgtype, data, False))
return out