Use LLDP to get switch port mapping
Provides a function to listen for LLDP packets on the network. Listens on one or all of the network interfaces, and then parses the found packets. Change-Id: I1545a41f46cd0916aab9c43ce036865454fa66e0 Co-Authored-By: Josh Gachnang <josh@pcsforeducation.com>
This commit is contained in:
Jim Rollenhagen
committed by
Josh Gachnang
Josh Gachnang
parent
cfdedd30d3
commit
15aaa03833
ironic_python_agent
197
ironic_python_agent/netutils.py
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197
ironic_python_agent/netutils.py
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# Copyright 2014 Rackspace, Inc.
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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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import ctypes
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import fcntl
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import logging
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import select
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import socket
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import struct
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import sys
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from oslo.config import cfg
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LOG = logging.getLogger(__name__)
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CONF = cfg.CONF
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LLDP_ETHERTYPE = 0x88cc
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IFF_PROMISC = 0x100
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SIOCGIFFLAGS = 0x8913
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SIOCSIFFLAGS = 0x8914
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class ifreq(ctypes.Structure):
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"""Class for setting flags on a socket."""
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_fields_ = [("ifr_ifrn", ctypes.c_char * 16),
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("ifr_flags", ctypes.c_short)]
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class RawPromiscuousSockets(object):
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def __init__(self, interface_names, protocol):
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"""Initialize context manager.
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:param interface_names: a list of interface names to bind to
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:param protocol: the protocol to listen for
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:returns: A list of tuple of (interface_name, bound_socket), or [] if
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there is an exception binding or putting the sockets in
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promiscuous mode
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"""
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if not interface_names:
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raise ValueError('interface_names must be a non-empty list of '
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'network interface names to bind to.')
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self.protocol = protocol
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# A 3-tuple of (interface_name, socket, ifreq object)
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self.interfaces = [(name, self._get_socket(), ifreq())
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for name in interface_names]
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def __enter__(self):
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for interface_name, sock, ifr in self.interfaces:
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LOG.info('Interface %s entering promiscuous mode to capture ',
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interface_name)
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try:
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ifr.ifr_ifrn = interface_name
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# Get current flags
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fcntl.ioctl(sock.fileno(), SIOCGIFFLAGS, ifr) # G for Get
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# bitwise or the flags with promiscuous mode, set the new flags
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ifr.ifr_flags |= IFF_PROMISC
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fcntl.ioctl(sock.fileno(), SIOCSIFFLAGS, ifr) # S for Set
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# Bind the socket so it can be used
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LOG.debug('Binding interface %(interface) for protocol '
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'%(proto)s: %s', {'interface': interface_name,
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'proto': self.protocol})
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sock.bind((interface_name, self.protocol))
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except Exception:
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LOG.warning('Failed to open all RawPromiscuousSockets, '
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'attempting to close any opened sockets.')
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if self.__exit__(*sys.exc_info()):
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return []
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else:
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LOG.exception('Could not successfully close all opened '
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'RawPromiscuousSockets.')
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raise
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# No need to return each interfaces ifreq.
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return [(sock[0], sock[1]) for sock in self.interfaces]
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def __exit__(self, exception_type, exception_val, trace):
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if exception_type:
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LOG.exception('Error while using raw socket: %(type)s: %(val)',
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{'type': exception_type, 'val': exception_val})
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for _name, sock, ifr in self.interfaces:
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# bitwise or with the opposite of promiscuous mode to remove
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ifr.ifr_flags &= ~IFF_PROMISC
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# If these raise, they shouldn't be caught
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fcntl.ioctl(sock.fileno(), SIOCSIFFLAGS, ifr)
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sock.close()
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# Return True to signify exit correctly, only used internally
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return True
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def _get_socket(self):
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return socket.socket(socket.AF_PACKET, socket.SOCK_RAW, self.protocol)
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def get_lldp_info(interface_names):
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"""Get LLDP info from the switch(es) the agent is connected to.
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Listens on either a single or all interfaces for LLDP packets, then
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parses them. If no LLDP packets are received before lldp_timeout,
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returns a dictionary in the form {'interface': [],...}.
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:param interface_names: The interface to listen for packets on. If
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None, will listen on each interface.
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:return: A dictionary in the form
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{'interface': [(lldp_type, lldp_data)],...}
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"""
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with RawPromiscuousSockets(interface_names, LLDP_ETHERTYPE) as interfaces:
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try:
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return _get_lldp_info(interfaces)
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except Exception as e:
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LOG.exception('Error while getting LLDP info: %s', str(e))
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raise
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def _parse_tlv(buff):
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"""Iterate over a buffer and generate structured TLV data.
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:param buff: An ethernet packet with the header trimmed off (first
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14 bytes)
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"""
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lldp_info = []
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while buff:
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# TLV structure: type (7 bits), length (9 bits), val (0-511 bytes)
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tlvhdr = struct.unpack('!H', buff[:2])[0]
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tlvtype = (tlvhdr & 0xfe00) >> 9
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tlvlen = (tlvhdr & 0x01ff)
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tlvdata = buff[2:tlvlen + 2]
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buff = buff[tlvlen + 2:]
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lldp_info.append((tlvtype, tlvdata))
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return lldp_info
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def _receive_lldp_packets(sock):
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"""Receive LLDP packets and process them.
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:param sock: A bound socket
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:return: A list of tuples in the form (lldp_type, lldp_data)
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"""
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pkt = sock.recv(1600)
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# Filter invalid packets
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if not pkt or len(pkt) < 14:
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return
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# Skip header (dst MAC, src MAC, ethertype)
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pkt = pkt[14:]
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return _parse_tlv(pkt)
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def _get_lldp_info(interfaces):
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"""Wait for packets on each socket, parse the received LLDP packets."""
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LOG.debug('Getting LLDP info for interfaces %s', interfaces)
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lldp_info = {}
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if not interfaces:
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return {}
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socks = [interface[1] for interface in interfaces]
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while interfaces:
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LOG.info('Waiting on LLDP info for interfaces: %(interfaces)s, '
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'timeout: %(timeout)s', {'interfaces': interfaces,
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'timeout': CONF.lldp_timeout})
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# rlist is a list of sockets ready for reading
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rlist, _, _ = select.select(socks, [], [], CONF.lldp_timeout)
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if not rlist:
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# Empty read list means timeout on all interfaces
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LOG.warning('LLDP timed out, remaining interfaces: %s',
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interfaces)
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break
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for s in rlist:
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# Find interface name matching socket ready for read
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# Create a copy of interfaces to avoid deleting while iterating.
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for index, interface in enumerate(list(interfaces)):
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if s == interface[1]:
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LOG.info('Found LLDP info for interface: %s',
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interface[0])
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lldp_info[interface[0]] = (
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_receive_lldp_packets(s))
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# Remove interface from the list, only need one packet
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del interfaces[index]
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# Add any interfaces that didn't get a packet as empty lists
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for name, _sock in interfaces:
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lldp_info[name] = []
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return lldp_info
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