1 #!/usr/bin/python 2 # 3 # Copyright 2017 The Android Open Source Project 4 # 5 # Licensed under the Apache License, Version 2.0 (the "License"); 6 # you may not use this file except in compliance with the License. 7 # You may obtain a copy of the License at 8 # 9 # http://www.apache.org/licenses/LICENSE-2.0 10 # 11 # Unless required by applicable law or agreed to in writing, software 12 # distributed under the License is distributed on an "AS IS" BASIS, 13 # WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 14 # See the License for the specific language governing permissions and 15 # limitations under the License. 16 17 """Classes for generic netlink.""" 18 19 import collections 20 from socket import * # pylint: disable=wildcard-import 21 import struct 22 23 import cstruct 24 import netlink 25 26 ### Generic netlink constants. See include/uapi/linux/genetlink.h. 27 # The generic netlink control family. 28 GENL_ID_CTRL = 16 29 30 # Commands. 31 CTRL_CMD_GETFAMILY = 3 32 33 # Attributes. 34 CTRL_ATTR_FAMILY_ID = 1 35 CTRL_ATTR_FAMILY_NAME = 2 36 CTRL_ATTR_VERSION = 3 37 CTRL_ATTR_HDRSIZE = 4 38 CTRL_ATTR_MAXATTR = 5 39 CTRL_ATTR_OPS = 6 40 CTRL_ATTR_MCAST_GROUPS = 7 41 42 # Attributes netsted inside CTRL_ATTR_OPS. 43 CTRL_ATTR_OP_ID = 1 44 CTRL_ATTR_OP_FLAGS = 2 45 46 47 # Data structure formats. 48 # These aren't constants, they're classes. So, pylint: disable=invalid-name 49 Genlmsghdr = cstruct.Struct("genlmsghdr", "BBxx", "cmd version") 50 51 52 class GenericNetlink(netlink.NetlinkSocket): 53 """Base class for all generic netlink classes.""" 54 55 NL_DEBUG = [] 56 57 def __init__(self): 58 super(GenericNetlink, self).__init__(netlink.NETLINK_GENERIC) 59 60 def _SendCommand(self, family, command, version, data, flags): 61 genlmsghdr = Genlmsghdr((command, version)) 62 self._SendNlRequest(family, genlmsghdr.Pack() + data, flags) 63 64 def _Dump(self, family, command, version): 65 msg = Genlmsghdr((command, version)) 66 return super(GenericNetlink, self)._Dump(family, msg, Genlmsghdr, "") 67 68 69 class GenericNetlinkControl(GenericNetlink): 70 """Generic netlink control class. 71 72 This interface is used to manage other generic netlink families. We currently 73 use it only to find the family ID for address families of interest.""" 74 75 def _DecodeOps(self, data): 76 ops = [] 77 Op = collections.namedtuple("Op", ["id", "flags"]) 78 while data: 79 # Skip the nest marker. 80 datalen, index, data = data[:2], data[2:4], data[4:] 81 82 nla, nla_data, data = self._ReadNlAttr(data) 83 if nla.nla_type != CTRL_ATTR_OP_ID: 84 raise ValueError("Expected CTRL_ATTR_OP_ID, got %d" % nla.nla_type) 85 op_id = struct.unpack("=I", nla_data)[0] 86 87 nla, nla_data, data = self._ReadNlAttr(data) 88 if nla.nla_type != CTRL_ATTR_OP_FLAGS: 89 raise ValueError("Expected CTRL_ATTR_OP_FLAGS, got %d" % nla.type) 90 op_flags = struct.unpack("=I", nla_data)[0] 91 92 ops.append(Op(op_id, op_flags)) 93 return ops 94 95 def _Decode(self, command, msg, nla_type, nla_data): 96 """Decodes generic netlink control attributes to human-readable format.""" 97 98 name = self._GetConstantName(__name__, nla_type, "CTRL_ATTR_") 99 100 if name == "CTRL_ATTR_FAMILY_ID": 101 data = struct.unpack("=H", nla_data)[0] 102 elif name == "CTRL_ATTR_FAMILY_NAME": 103 data = nla_data.strip("\x00") 104 elif name in ["CTRL_ATTR_VERSION", "CTRL_ATTR_HDRSIZE", "CTRL_ATTR_MAXATTR"]: 105 data = struct.unpack("=I", nla_data)[0] 106 elif name == "CTRL_ATTR_OPS": 107 data = self._DecodeOps(nla_data) 108 else: 109 data = nla_data 110 111 return name, data 112 113 def GetFamily(self, name): 114 """Returns the family ID for the specified family name.""" 115 data = self._NlAttrStr(CTRL_ATTR_FAMILY_NAME, name) 116 self._SendCommand(GENL_ID_CTRL, CTRL_CMD_GETFAMILY, 0, data, netlink.NLM_F_REQUEST) 117 hdr, attrs = self._GetMsg(Genlmsghdr) 118 return attrs["CTRL_ATTR_FAMILY_ID"] 119 120 121 if __name__ == "__main__": 122 g = GenericNetlinkControl() 123 print g.GetFamily("tcp_metrics") 124
