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discovery.py
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discovery.py
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# Copyright 2011-2013 James McCauley
#
# This file is part of POX.
#
# POX is free software: you can redistribute it and/or modify
# it under the terms of the GNU General Public License as published by
# the Free Software Foundation, either version 3 of the License, or
# (at your option) any later version.
#
# POX is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
# GNU General Public License for more details.
#
# You should have received a copy of the GNU General Public License
# along with POX. If not, see <http://www.gnu.org/licenses/>.
# This file is loosely based on the discovery component in NOX.
"""
This module discovers the connectivity between OpenFlow switches by sending
out LLDP packets. To be notified of this information, listen to LinkEvents
on core.openflow_discovery.
It's possible that some of this should be abstracted out into a generic
Discovery module, or a Discovery superclass.
"""
from pox.lib.revent import *
from pox.lib.recoco import Timer
from pox.lib.util import dpid_to_str, str_to_bool
from pox.core import core
import pox.openflow.libopenflow_01 as of
import pox.lib.packet as pkt
import struct
import time
from collections import namedtuple
from random import shuffle
log = core.getLogger()
class LLDPSender (object):
"""
Sends out discovery packets
"""
SendItem = namedtuple("LLDPSenderItem", ('dpid','port_num','packet'))
#NOTE: This class keeps the packets to send in a flat list, which makes
# adding/removing them on switch join/leave or (especially) port
# status changes relatively expensive. Could easily be improved.
def __init__ (self, send_cycle_time, ttl = 120):
"""
Initialize an LLDP packet sender
send_cycle_time is the time (in seconds) that this sender will take to
send every discovery packet. Thus, it should be the link timeout
interval at most.
ttl is the time (in seconds) for which a receiving LLDP agent should
consider the rest of the data to be valid. We don't use this, but
other LLDP agents might. Can't be 0 (this means revoke).
"""
# Packets remaining to be sent in this cycle
self._this_cycle = []
# Packets we've already sent in this cycle
self._next_cycle = []
self._timer = None
self._ttl = ttl
self._send_cycle_time = send_cycle_time
core.listen_to_dependencies(self)
def _handle_openflow_PortStatus (self, event):
"""
Track changes to switch ports
"""
if event.added:
self.add_port(event.dpid, event.port, event.ofp.desc.hw_addr)
elif event.deleted:
self.del_port(event.dpid, event.port)
def _handle_openflow_ConnectionUp (self, event):
self.del_switch(event.dpid, set_timer = False)
ports = [(p.port_no, p.hw_addr) for p in event.ofp.ports]
for port_num, port_addr in ports:
self.add_port(event.dpid, port_num, port_addr, set_timer = False)
self._set_timer()
def _handle_openflow_ConnectionDown (self, event):
self.del_switch(event.dpid)
def del_switch (self, dpid, set_timer = True):
self._this_cycle = [p for p in self._this_cycle if p.dpid != dpid]
self._next_cycle = [p for p in self._next_cycle if p.dpid != dpid]
if set_timer: self._set_timer()
def del_port (self, dpid, port_num, set_timer = True):
if port_num > of.OFPP_MAX: return
self._this_cycle = [p for p in self._this_cycle
if p.dpid != dpid or p.port_num != port_num]
self._next_cycle = [p for p in self._next_cycle
if p.dpid != dpid or p.port_num != port_num]
if set_timer: self._set_timer()
def add_port (self, dpid, port_num, port_addr, set_timer = True):
if port_num > of.OFPP_MAX: return
self.del_port(dpid, port_num, set_timer = False)
self._next_cycle.append(LLDPSender.SendItem(dpid, port_num,
self.create_discovery_packet(dpid, port_num, port_addr)))
if set_timer: self._set_timer()
def _set_timer (self):
if self._timer: self._timer.cancel()
self._timer = None
num_packets = len(self._this_cycle) + len(self._next_cycle)
if num_packets != 0:
self._timer = Timer(self._send_cycle_time / float(num_packets),
self._timer_handler, recurring=True)
def _timer_handler (self):
"""
Called by a timer to actually send packets.
Picks the first packet off this cycle's list, sends it, and then puts
it on the next-cycle list. When this cycle's list is empty, starts
the next cycle.
"""
if len(self._this_cycle) == 0:
self._this_cycle = self._next_cycle
self._next_cycle = []
shuffle(self._this_cycle)
item = self._this_cycle.pop(0)
self._next_cycle.append(item)
core.openflow.sendToDPID(item.dpid, item.packet)
def create_discovery_packet (self, dpid, port_num, port_addr):
"""
Build discovery packet
"""
chassis_id = pkt.chassis_id(subtype=pkt.chassis_id.SUB_LOCAL)
chassis_id.id = bytes('dpid:' + hex(long(dpid))[2:-1])
# Maybe this should be a MAC. But a MAC of what? Local port, maybe?
port_id = pkt.port_id(subtype=pkt.port_id.SUB_PORT, id=str(port_num))
ttl = pkt.ttl(ttl = self._ttl)
sysdesc = pkt.system_description()
sysdesc.payload = bytes('dpid:' + hex(long(dpid))[2:-1])
discovery_packet = pkt.lldp()
discovery_packet.tlvs.append(chassis_id)
discovery_packet.tlvs.append(port_id)
discovery_packet.tlvs.append(ttl)
discovery_packet.tlvs.append(sysdesc)
discovery_packet.tlvs.append(pkt.end_tlv())
eth = pkt.ethernet(type=pkt.ethernet.LLDP_TYPE)
eth.src = port_addr
eth.dst = pkt.ETHERNET.NDP_MULTICAST
eth.payload = discovery_packet
po = of.ofp_packet_out(action = of.ofp_action_output(port=port_num))
po.data = eth.pack()
return po.pack()
class LinkEvent (Event):
"""
Link up/down event
"""
def __init__ (self, add, link):
Event.__init__(self)
self.link = link
self.added = add
self.removed = not add
def port_for_dpid (self, dpid):
if self.link.dpid1 == dpid:
return self.link.port1
if self.link.dpid2 == dpid:
return self.link.port2
return None
class Discovery (EventMixin):
"""
Component that attempts to discover network toplogy.
Sends out specially-crafted LLDP packets, and monitors their arrival.
"""
_flow_priority = 65000 # Priority of LLDP-catching flow (if any)
_link_timeout = 10 # How long until we consider a link dead
_timeout_check_period = 5 # How often to check for timeouts
_eventMixin_events = set([
LinkEvent,
])
_core_name = "openflow_discovery" # we want to be core.openflow_discovery
Link = namedtuple("Link",("dpid1","port1","dpid2","port2"))
def __init__ (self, install_flow = True, explicit_drop = True,
link_timeout = None, eat_early_packets = False):
self._eat_early_packets = eat_early_packets
self._explicit_drop = explicit_drop
self._install_flow = install_flow
if link_timeout: self._link_timeout = link_timeout
self.adjacency = {} # From Link to time.time() stamp
self._sender = LLDPSender(self.send_cycle_time)
# Listen with a high priority (mostly so we get PacketIns early)
core.listen_to_dependencies(self,
listen_args={'openflow':{'priority':0xffffffff}})
Timer(self._timeout_check_period, self._expire_links, recurring=True)
@property
def send_cycle_time (self):
return self._link_timeout / 2.0
def _handle_openflow_ConnectionUp (self, event):
if self._install_flow:
# Make sure we get appropriate traffic
log.debug("Installing flow for %s", dpid_to_str(event.dpid))
match = of.ofp_match(dl_type = pkt.ethernet.LLDP_TYPE,
dl_dst = pkt.ETHERNET.NDP_MULTICAST)
msg = of.ofp_flow_mod()
msg.priority = self._flow_priority
msg.match = match
msg.actions.append(of.ofp_action_output(port = of.OFPP_CONTROLLER))
event.connection.send(msg)
def _handle_openflow_ConnectionDown (self, event):
# Delete all links on this switch
self._delete_links([link for link in self.adjacency
if link.dpid1 == event.dpid
or link.dpid2 == event.dpid])
def _expire_links (self):
"""
Remove apparently dead links
"""
now = time.time()
expired = [link for link,timestamp in self.adjacency.iteritems()
if timestamp + self._link_timeout < now]
if expired:
for link in expired:
log.info('link timeout: %s.%i -> %s.%i' %
(dpid_to_str(link.dpid1), link.port1,
dpid_to_str(link.dpid2), link.port2))
self._delete_links(expired)
def _handle_openflow_PacketIn (self, event):
"""
Receive and process LLDP packets
"""
packet = event.parsed
if (packet.effective_ethertype != pkt.ethernet.LLDP_TYPE
or packet.dst != pkt.ETHERNET.NDP_MULTICAST):
if not self._eat_early_packets: return
if not event.connection.connect_time: return
enable_time = time.time() - self.send_cycle_time - 1
if event.connection.connect_time > enable_time:
return EventHalt
return
if self._explicit_drop:
if event.ofp.buffer_id is not None:
log.debug("Dropping LLDP packet %i", event.ofp.buffer_id)
msg = of.ofp_packet_out()
msg.buffer_id = event.ofp.buffer_id
msg.in_port = event.port
event.connection.send(msg)
lldph = packet.find(pkt.lldp)
if lldph is None or not lldph.parsed:
log.error("LLDP packet could not be parsed")
return EventHalt
if len(lldph.tlvs) < 3:
log.error("LLDP packet without required three TLVs")
return EventHalt
if lldph.tlvs[0].tlv_type != pkt.lldp.CHASSIS_ID_TLV:
log.error("LLDP packet TLV 1 not CHASSIS_ID")
return EventHalt
if lldph.tlvs[1].tlv_type != pkt.lldp.PORT_ID_TLV:
log.error("LLDP packet TLV 2 not PORT_ID")
return EventHalt
if lldph.tlvs[2].tlv_type != pkt.lldp.TTL_TLV:
log.error("LLDP packet TLV 3 not TTL")
return EventHalt
def lookInSysDesc ():
r = None
for t in lldph.tlvs[3:]:
if t.tlv_type == pkt.lldp.SYSTEM_DESC_TLV:
# This is our favored way...
for line in t.payload.split('\n'):
if line.startswith('dpid:'):
try:
return int(line[5:], 16)
except:
pass
if len(t.payload) == 8:
# Maybe it's a FlowVisor LLDP...
# Do these still exist?
try:
return struct.unpack("!Q", t.payload)[0]
except:
pass
return None
originatorDPID = lookInSysDesc()
if originatorDPID == None:
# We'll look in the CHASSIS ID
if lldph.tlvs[0].subtype == pkt.chassis_id.SUB_LOCAL:
if lldph.tlvs[0].id.startswith('dpid:'):
# This is how NOX does it at the time of writing
try:
originatorDPID = int(lldph.tlvs[0].id[5:], 16)
except:
pass
if originatorDPID == None:
if lldph.tlvs[0].subtype == pkt.chassis_id.SUB_MAC:
# Last ditch effort -- we'll hope the DPID was small enough
# to fit into an ethernet address
if len(lldph.tlvs[0].id) == 6:
try:
s = lldph.tlvs[0].id
originatorDPID = struct.unpack("!Q",'\x00\x00' + s)[0]
except:
pass
if originatorDPID == None:
log.warning("Couldn't find a DPID in the LLDP packet")
return EventHalt
if originatorDPID not in core.openflow.connections:
log.info('Received LLDP packet from unknown switch')
return EventHalt
# Get port number from port TLV
if lldph.tlvs[1].subtype != pkt.port_id.SUB_PORT:
log.warning("Thought we found a DPID, but packet didn't have a port")
return EventHalt
originatorPort = None
if lldph.tlvs[1].id.isdigit():
# We expect it to be a decimal value
originatorPort = int(lldph.tlvs[1].id)
elif len(lldph.tlvs[1].id) == 2:
# Maybe it's a 16 bit port number...
try:
originatorPort = struct.unpack("!H", lldph.tlvs[1].id)[0]
except:
pass
if originatorPort is None:
log.warning("Thought we found a DPID, but port number didn't " +
"make sense")
return EventHalt
if (event.dpid, event.port) == (originatorDPID, originatorPort):
log.warning("Port received its own LLDP packet; ignoring")
return EventHalt
link = Discovery.Link(originatorDPID, originatorPort, event.dpid,
event.port)
if link not in self.adjacency:
self.adjacency[link] = time.time()
log.info('link detected: %s.%i -> %s.%i' %
(dpid_to_str(link.dpid1), link.port1,
dpid_to_str(link.dpid2), link.port2))
self.raiseEventNoErrors(LinkEvent, True, link)
else:
# Just update timestamp
self.adjacency[link] = time.time()
return EventHalt # Probably nobody else needs this event
def _delete_links (self, links):
for link in links:
del self.adjacency[link]
self.raiseEventNoErrors(LinkEvent, False, link)
def is_edge_port (self, dpid, port):
"""
Return True if given port does not connect to another switch
"""
for link in self.adjacency:
if link.dpid1 == dpid and link.port1 == port:
return False
if link.dpid2 == dpid and link.port2 == port:
return False
return True
def launch (no_flow = False, explicit_drop = True, link_timeout = None,
eat_early_packets = False):
explicit_drop = str_to_bool(explicit_drop)
eat_early_packets = str_to_bool(eat_early_packets)
install_flow = not str_to_bool(no_flow)
if link_timeout: link_timeout = int(link_timeout)
core.registerNew(Discovery, explicit_drop=explicit_drop,
install_flow=install_flow, link_timeout=link_timeout,
eat_early_packets=eat_early_packets)