NameError: global name 'get_all_switch' is not defined

Question

I am new to python.I am trying to develop and openflow application.The application that I begin with is the following file.As you can see it implements a simple Ethernet switch.

https://github.com/osrg/ryu/blob/master/ryu/app/simple_switch.py

Now I have another file

https://github.com/osrg/ryu/blob/master/ryu/topology/api.py

Which looks like it exposes the functions to return link and switch information in the topology.

How ever if I try to call the function as below inside init() of simple_switch.py it returns an error?

   def __init__(self, *args, **kwargs):
        super(SimpleSwitch, self).__init__(*args, **kwargs)
        self.mac_to_port = {}
        s_list = get_all_switch(app_manager)

This is the error that I get.

loading app ryu/app/simple_switch.py
loading app ryu.controller.ofp_handler
instantiating app ryu.controller.ofp_handler of OFPHandler
instantiating app ryu/app/simple_switch.py of SimpleSwitch
Traceback (most recent call last):
  File "/usr/local/bin/ryu-manager", line 9, in <module>
    load_entry_point('ryu==3.8', 'console_scripts', 'ryu-manager')()
  File "/usr/local/lib/python2.7/dist-packages/ryu/cmd/manager.py", line 73, in main
    services.extend(app_mgr.instantiate_apps(**contexts))
  File "/usr/local/lib/python2.7/dist-packages/ryu/base/app_manager.py", line 434, in instantiate_apps
    self._instantiate(app_name, cls, *args, **kwargs)
  File "/usr/local/lib/python2.7/dist-packages/ryu/base/app_manager.py", line 420, in _instantiate
    app = cls(*args, **kwargs)
  File "/home/karthik/Projects/ryu/ryu/app/simple_switch.py", line 35, in __init__
    s_list = get_all_switch(app_manager)
NameError: global name 'get_all_switch' is not defined

My questions are as follows.

1) Can I get the topology information about my mininet topology using - get_all_switch() and - get_all_link() defined in ryu/topology/api.py?

2) If yes,Why isn't the code above not working as expected?

I am asking here because my working knowledge of python is not that great.I want to be able to use the functions inside topology/api.py in simple_switch.py

My import lines in the application simple_switch.py are as follows

import logging
import struct

from ryu.base import app_manager
from ryu.controller import mac_to_port
from ryu.controller import ofp_event
from ryu.controller.handler import MAIN_DISPATCHER
from ryu.controller.handler import set_ev_cls
from ryu.ofproto import ofproto_v1_0
from ryu.lib.mac import haddr_to_bin
from ryu.lib.packet import packet
from ryu.lib.packet import ethernet

Updated based on Answer 1:

I have modified my code as follows:

from ryu.base import app_manager
from ryu.controller import mac_to_port
from ryu.controller import ofp_event
from ryu.controller.handler import MAIN_DISPATCHER
from ryu.controller.handler import set_ev_cls
from ryu.ofproto import ofproto_v1_0
from ryu.lib.mac import haddr_to_bin
from ryu.lib.packet import packet
from ryu.lib.packet import ethernet
import ryu.topology.api


 def __init__(self, *args, **kwargs):
        super(SimpleSwitch, self).__init__(*args, **kwargs)
        self.mac_to_port = {}
        s_list = ryu.topology.api.get_all_switch(app_manager.RyuApp)

I am now getting a new error:

loading app ryu/app/simple_switch.py
loading app ryu.topology.switches
loading app ryu.controller.ofp_handler
loading app ryu.controller.ofp_handler
instantiating app ryu.topology.switches of Switches
instantiating app ryu.controller.ofp_handler of OFPHandler
instantiating app ryu/app/simple_switch.py of SimpleSwitch
Traceback (most recent call last):
  File "/usr/local/bin/ryu-manager", line 9, in <module>
    load_entry_point('ryu==3.8', 'console_scripts', 'ryu-manager')()
  File "/usr/local/lib/python2.7/dist-packages/ryu/cmd/manager.py", line 73, in main
    services.extend(app_mgr.instantiate_apps(**contexts))
  File "/usr/local/lib/python2.7/dist-packages/ryu/base/app_manager.py", line 434, in instantiate_apps
    self._instantiate(app_name, cls, *args, **kwargs)
  File "/usr/local/lib/python2.7/dist-packages/ryu/base/app_manager.py", line 420, in _instantiate
    app = cls(*args, **kwargs)
  File "/home/karthik/Projects/ryu/ryu/app/simple_switch.py", line 36, in __init__
    s_list = ryu.topology.api.get_all_switch(app_manager.RyuApp)
  File "/usr/local/lib/python2.7/dist-packages/ryu/topology/api.py", line 26, in get_all_switch
    return get_switch(app)
  File "/usr/local/lib/python2.7/dist-packages/ryu/topology/api.py", line 21, in get_switch
    rep = app.send_request(event.EventSwitchRequest(dpid))
TypeError: unbound method send_request() must be called with RyuApp instance as first argument (got EventSwitchRequest instance instead)

Answer 1

1. Yes.
2. Most likely, you should use a qualified name, something like ryu.topology.api.get_all_switch(). For the exact answer more context will be necessary (say, show your import lines).

Answer 2

Based on the above answers and some digging I have my code as below and it works perfectly:

from ryu.base import app_manager
from ryu.controller import ofp_event
from ryu.controller.handler import CONFIG_DISPATCHER, MAIN_DISPATCHER
from ryu.controller.handler import set_ev_cls
from ryu.ofproto import ofproto_v1_3
from ryu.lib.packet import packet
from ryu.lib.packet import ethernet

from ryu.topology import event
from ryu.topology.api import get_all_switch, get_all_link


class SimpleSwitch13(app_manager.RyuApp):
    OFP_VERSIONS = [ofproto_v1_3.OFP_VERSION]

    def __init__(self, *args, **kwargs):
        super(SimpleSwitch13, self).__init__(*args, **kwargs)
        self.mac_to_port = {}

    @set_ev_cls(ofp_event.EventOFPSwitchFeatures, CONFIG_DISPATCHER)
    def switch_features_handler(self, ev):
        self.logger.info("Received EventOFPSwitchFeatures")
        msg = ev.msg
        self.logger.info('OFPSwitchFeatures received: '
                         '\n\tdatapath_id=0x%016x n_buffers=%d '
                         '\n\tn_tables=%d auxiliary_id=%d '
                         '\n\tcapabilities=0x%08x',
                         msg.datapath_id, msg.n_buffers, msg.n_tables,
                         msg.auxiliary_id, msg.capabilities)

        datapath = ev.msg.datapath
        ofproto = datapath.ofproto
        parser = datapath.ofproto_parser
        match = parser.OFPMatch()
        actions = [parser.OFPActionOutput(ofproto.OFPP_CONTROLLER,
                                          ofproto.OFPCML_NO_BUFFER)]
        self.add_flow(datapath, 0, match, actions)

    def add_flow(self, datapath, priority, match, actions, buffer_id=None):
        ofproto = datapath.ofproto
        parser = datapath.ofproto_parser

        inst = [parser.OFPInstructionActions(ofproto.OFPIT_APPLY_ACTIONS,
                                             actions)]
        if buffer_id:
            mod = parser.OFPFlowMod(datapath=datapath, buffer_id=buffer_id,
                                    priority=priority, match=match,
                                    instructions=inst)
        else:
            mod = parser.OFPFlowMod(datapath=datapath, priority=priority,
                                    match=match, instructions=inst)
        datapath.send_msg(mod)

    @set_ev_cls(ofp_event.EventOFPPacketIn, MAIN_DISPATCHER)
    def _packet_in_handler(self, ev):
        #self.logger.info("Received EventOFPPacketIn")
        # If you hit this you might want to increase
        # the "miss_send_length" of your switch
        if ev.msg.msg_len < ev.msg.total_len:
            self.logger.debug("packet truncated: only %s of %s bytes",
                              ev.msg.msg_len, ev.msg.total_len)
        msg = ev.msg
        datapath = msg.datapath
        ofproto = datapath.ofproto
        parser = datapath.ofproto_parser
        in_port = msg.match['in_port']

        pkt = packet.Packet(msg.data)
        eth = pkt.get_protocols(ethernet.ethernet)[0]

        dst = eth.dst
        src = eth.src

        dpid = datapath.id
        self.mac_to_port.setdefault(dpid, {})

        self.logger.info("\tpacket in %s %s %s %s", dpid, src, dst, in_port)

        # learn a mac address to avoid FLOOD next time.
        self.mac_to_port[dpid][src] = in_port

        if dst in self.mac_to_port[dpid]:
            out_port = self.mac_to_port[dpid][dst]
        else:
            out_port = ofproto.OFPP_FLOOD

        actions = [parser.OFPActionOutput(out_port)]

        # install a flow to avoid packet_in next time
        if out_port != ofproto.OFPP_FLOOD:
            match = parser.OFPMatch(in_port=in_port, eth_dst=dst)
            # verify if we have a valid buffer_id, if yes avoid to send both
            # flow_mod & packet_out
            if msg.buffer_id != ofproto.OFP_NO_BUFFER:
                self.add_flow(datapath, 1, match, actions, msg.buffer_id)
                return
            else:
                self.add_flow(datapath, 1, match, actions)
        data = None
        if msg.buffer_id == ofproto.OFP_NO_BUFFER:
            data = msg.data

        out = parser.OFPPacketOut(datapath=datapath, buffer_id=msg.buffer_id,
                                  in_port=in_port, actions=actions, data=data)
        datapath.send_msg(out)

    """
    The event EventSwitchEnter will trigger the activation of get_topology_data().
    """
    @set_ev_cls(event.EventSwitchEnter, [MAIN_DISPATCHER,CONFIG_DISPATCHER])
    def get_topology_data(self, ev):
        self.logger.info("[Ehsan] Received EventSwitchEnter")
        # Call get_switch() to get the list of objects Switch.
        switch_list = get_all_switch(self)

        # Build a list with all the switches ([switches])
        topo_switches = [switch.dp.id for switch in switch_list]

        # Call get_link() to get the list of objects Link.
        links_list = get_all_link(self)

        # Build a  list with all the links [(srcNode, dstNode, port)].
        topo_links = [(link.src.dpid,link.dst.dpid,{'port':link.src.port_no}) for link in links_list]

        print ("\tLinks: "+str(topo_links))
        print ("\tSwitches: "+str(topo_switches))

At the moment I have the function triggered when a switch is connected, but you could modify get_topology_data() to call it for any event. For example, you call it when a port_status is received or a link is deleted/added/modified to update the topo.

Note that I am still in the developing stage of this code. I will probably add the full code to my repo sometime later.

Answer 3

try to use this line instead:

s_list = ryu.topology.api.get_all_switch(self)