Detect Link down in mininet

Question

How does controller detect if a link gets down in mininet? I have tried HostTracker but it doesn't give desired output. What i need to do is, whenever a link goes down controller should ask all the switches to delete corresponding destination host entry from their flow table.

Answer 1

An OpenFlow switch should report port status events to the controller. Assuming you're using POX, listen for those events in your SwitchHandler class, e.g. with this code from the POX Wiki:

def _handle_PortStatus (self, event):
    if event.added:
        action = "added"
    elif event.deleted:
        action = "removed"
    else:
        action = "modified"
    print "Port %s on Switch %s has been %s." % (event.port, event.dpid, action)

You'll need to have topology information - what host is connected to what port. host_tracker should give you that.