I am using Ryu as my SDN controller to control a topo that has a loop.
I am using a learning switch technique to route packets. My main functions/handlers are:
@set_ev_cls(ofp_event.EventOFPSwitchFeatures, CONFIG_DISPATCHER)
def switch_features_handler(self, ev):
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)
"""
This is called when Ryu receives an OpenFlow packet_in message. The trick is set_ev_cls decorator. This decorator
tells Ryu when the decorated function should be called.
"""
@set_ev_cls(ofp_event.EventOFPPacketIn, MAIN_DISPATCHER)
def _packet_in_handler(self, ev):
#print(self.mac_to_port)
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)
I need to have loop in my topo. Does any one know how to properly configure the topo/controller so that loops are pingable?
My full controller code: https://github.com/Ehsan70/RyuApps/blob/master/topo_learner.py My topo code: https://github.com/Ehsan70/RyuApps/blob/master/Pkt_Topo_with_loop.py
Ok so after some digging, apparently, ideal networks should not have loops. But in real world design they do. So to cope with that and kinda break the loop, Spanning Tree Algorithm is used. The algorithm finds out the minimum set of edges where you can reach every node.
See this link for info on how to use Ryu's STP. Also clone this repo for some tutorials and sample code.