from pox.core import core
import pox.openflow.libopenflow_01 as of
import re
import datetime
from sqlalchemy import create_engine, ForeignKey
from sqlalchemy import Column, Date, Integer, String
from sqlalchemy.ext.declarative import declarative_base
from sqlalchemy.orm import relationship, backref
from sqlalchemy import create_engine
from sqlalchemy.orm import sessionmaker
from sqlalchemy.sql.expression import exists
log = core.getLogger()
engine = create_engine('sqlite:///nwtopology.db', echo=False)
Base = declarative_base()
Session = sessionmaker(bind=engine)
session = Session()
########################################################################
class SourcetoPort(Base):
""""""
__tablename__ = 'source_to_port'
id = Column(Integer, primary_key=True)
port_no = Column(Integer)
src_address = Column(String,index=True)
#----------------------------------------------------------------------
def __init__(self, src_address,port_no):
""""""
self.src_address = src_address
self.port_no = port_no
########################################################################
#create tables
Base.metadata.create_all(engine)
class Tutorial (object):
def __init__ (self, connection):
self.connection = connection
connection.addListeners(self)
# Use this table to keep track of which ethernet address is on
# which switch port (keys are MACs, values are ports).
self.mac_to_port = {}
self.matrix={}
#This will keep track of the traffic matrix.
#matrix[i][j]=number of times a packet from i went to j
def send_packet (self, buffer_id, raw_data, out_port, in_port):
#print "calling send_packet"
#Sends a packet out of the specified switch port.
msg = of.ofp_packet_out()
msg.in_port = in_port
msg.data = raw_data
# Add an action to send to the specified port
action = of.ofp_action_output(port = out_port)
msg.actions.append(action)
# Send message to switch
self.connection.send(msg)
def act_like_hub (self, packet, packet_in):
#flood packet on all ports
self.send_packet(packet_in.buffer_id, packet_in.data,
of.OFPP_FLOOD, packet_in.in_port)
def act_like_switch (self, packet, packet_in):
"""
Implement switch-like behavior.
"""
# Learn the port for the source MAC
#print "RECIEVED FROM PORT ",packet_in.in_port , "SOURCE ",packet.src
# create a Session
#Session = sessionmaker(bind=engine)
#session = Session()
self.mac_to_port[packet.src]=packet_in.in_port
#if self.mac_to_port.get(packet.dst)!=None:
#print "count for dst",session.query(SourcetoPort).filter_by(src_address=str(packet.dst)).count(),str(packet.dst)
#if session.query(SourcetoPort).filter_by(src_address=str(packet.dst)).count():
if session.query(exists().where(SourcetoPort.src_address == str(packet.dst))).scalar() is not None:
#send this packet
print "got info from the database"
q_res = session.query(SourcetoPort).filter_by(src_address=str(packet.dst)).one()
self.send_packet(packet_in.buffer_id, packet_in.data,q_res.port_no, packet_in.in_port)
#create a flow modification message
msg = of.ofp_flow_mod()
#set the fields to match from the incoming packet
msg.match = of.ofp_match.from_packet(packet)
#send the rule to the switch so that it does not query the controller again.
msg.actions.append(of.ofp_action_output(port=q_res.port_no))
#push the rule
self.connection.send(msg)
else:
#flood this packet out as we don't know about this node.
print "flooding the first packet"
self.send_packet(packet_in.buffer_id, packet_in.data,
of.OFPP_FLOOD, packet_in.in_port)
#self.matrix[(packet.src,packet.dst)]+=1
entry = SourcetoPort(src_address=str(packet.src) , port_no=packet_in.in_port)
#add the record to the session object
session.add(entry)
#add the record to the session object
session.commit()
def _handle_PacketIn (self, event):
"""
Handles packet in messages from the switch.
"""
packet = event.parsed # This is the parsed packet data.
if not packet.parsed:
log.warning("Ignoring incomplete packet")
return
packet_in = event.ofp # The actual ofp_packet_in message.
#self.act_like_hub(packet, packet_in)
self.act_like_switch(packet, packet_in)
def launch ():
"""
Starts the component
"""
def start_switch (event):
log.debug("Controlling %s" % (event.connection,))
Tutorial(event.connection)
core.openflow.addListenerByName("ConnectionUp", start_switch)
当我运行上面的代码时，我收到以下错误：
如果我使用
，我面临的问题是出于某种原因if session.query(exists().where(SourcetoPort.src_address == str(packet.dst))).scalar() is not None:
in place of count query.
#if session.query(SourcetoPort).filter_by(src_address=str(packet.dst)).count():
从数据库查询
q_res = session.query(SourcetoPort).filter_by(src_address=str(packet.dst)).first()
self.send_packet(packet_in.buffer_id, packet_in.data,q_res.port_no, packet_in.in_port)
发出以下错误：
DEBUG:core:POX 0.1.0 (betta) going up...
DEBUG:core:Running on CPython (2.7.3/Aug 1 2012 05:14:39)
DEBUG:core:Platform is Linux-3.5.0-23-generic-x86_64-with-Ubuntu-12.04-precise
INFO:core:POX 0.1.0 (betta) is up.
DEBUG:openflow.of_01:Listening on 0.0.0.0:6633
INFO:openflow.of_01:[00-00-00-00-00-02 1] connected
DEBUG:tutorial:Controlling [00-00-00-00-00-02 1]
got info from the database
ERROR:core:Exception while handling Connection!PacketIn...
Traceback (most recent call last):
File "/home/karthik/pox/pox/lib/revent/revent.py", line 234, in raiseEventNoErrors
return self.raiseEvent(event, *args, **kw)
File "/home/karthik/pox/pox/lib/revent/revent.py", line 281, in raiseEvent
rv = event._invoke(handler, *args, **kw)
File "/home/karthik/pox/pox/lib/revent/revent.py", line 159, in _invoke
return handler(self, *args, **kw)
File "/home/karthik/pox/tutorial.py", line 118, in _handle_PacketIn
self.act_like_switch(packet, packet_in)
File "/home/karthik/pox/tutorial.py", line 86, in act_like_switch
self.send_packet(packet_in.buffer_id, packet_in.data,q_res.port_no, packet_in.in_port)
AttributeError: 'NoneType' object has no attribute 'port_no'
got info from the database
ERROR:core:Exception while handling Connection!PacketIn...
答案 0 :(得分：4)
这一行：
if session.query(exists().where(SourcetoPort.src_address == str(packet.dst))).scalar() is not None:
总是如此。原因是scalar()仅在没有行时才会返回None。但是，您的查询看起来像SELECT EXISTS (SELECT * FROM source_to_port WHERE source_to_port.src_address=?)。这将始终返回一行一行。因此结果为True或False，而不是None。
转到引发异常的行之前的行：first()如果没有匹配则返回None，因此q_res为None。由于q_res为None，因此下一行的q_res.port_no会引发异常。
（注意如果你想要在没有匹配的情况下抛出异常，你可以使用one()。）
如果您希望匹配，请仔细检查您的数据和filter_by()条件，以确保他们按照您认为的方式进行操作。
但我建议您使用first()或one()使用一个查询而不是两个查询。使用first()，您可以根据q_res是否None进行分支：
q_res = session.query(SourcetoPort).filter_by(src_address=str(packet.dst)).first()
if q_res is not None:
print "got info from the database"
self.send_packet(....)
...
else:
print "flooding the first packet"
...
或者使用one()，将“flooding”分支放在异常处理程序中：
from sqlalchemy.orm.exc import (NoResultFound, MultipleResultsFound)
try:
q_res = session.query(SourcetoPort).filter_by(src_address=str(packet.dst)).one()
except NoResultFound:
print "flooding the first packet"
...
# except MultipleResultsFound:
# print "More than one result found! WUT?!"
else:
print "got info from the database"
...
这两种方法之间的区别在于one()将确保只有一个且只有一个结果，而first()并不关心是否存在多个结果。< / p>