add lab 3 materials

examples/exercises/applayer/blastee.py

+#!/usr/bin/env python3
+
+from switchyard.lib.address import *
+from switchyard.lib.packet import *
+from switchyard.lib.userlib import *
+from threading import *
+import time
+
+def switchy_main(net):
+    my_interfaces = net.interfaces()
+    mymacs = [intf.ethaddr for intf in my_interfaces]
+
+    while True:
+        gotpkt = True
+        try:
+            timestamp,dev,pkt = net.recv_packet()
+            log_debug("Device is {}".format(dev))
+        except NoPackets:
+            log_debug("No packets available in recv_packet")
+            gotpkt = False
+        except Shutdown:
+            log_debug("Got shutdown signal")
+            break
+
+        if gotpkt:
+            log_debug("I got a packet from {}".format(dev))
+            log_debug("Pkt: {}".format(pkt))
+
+
+    net.shutdown()

examples/exercises/applayer/blaster.py

+#!/usr/bin/env python3
+
+from switchyard.lib.address import *
+from switchyard.lib.packet import *
+from switchyard.lib.userlib import *
+from random import randint
+import time
+
+
+def switchy_main(net):
+    my_intf = net.interfaces()
+    mymacs = [intf.ethaddr for intf in my_intf]
+    myips = [intf.ipaddr for intf in my_intf]
+
+    while True:
+        gotpkt = True
+        try:
+            #Timeout value will be parameterized!
+            timestamp,dev,pkt = net.recv_packet(timeout=0.15)
+        except NoPackets:
+            log_debug("No packets available in recv_packet")
+            gotpkt = False
+        except Shutdown:
+            log_debug("Got shutdown signal")
+            break
+
+        if gotpkt:
+            log_debug("I got a packet")
+        else:
+            log_debug("Didn't receive anything")
+
+            '''
+            Creating the headers for the packet
+            '''
+            pkt = Ethernet() + IPv4() + UDP()
+            pkt[1].protocol = IPProtocol.UDP
+
+            '''
+            Do other things here and send packet
+            '''
+
+    net.shutdown()

examples/exercises/applayer/middlebox.py

+#!/usr/bin/env python3
+
+from switchyard.lib.address import *
+from switchyard.lib.packet import *
+from switchyard.lib.userlib import *
+from threading import *
+from random import randint
+import time
+
+def switchy_main(net):
+
+    my_intf = net.interfaces()
+    mymacs = [intf.ethaddr for intf in my_intf]
+    myips = [intf.ipaddr for intf in my_intf]
+
+    while True:
+        gotpkt = True
+        try:
+            timestamp,dev,pkt = net.recv_packet()
+            log_debug("Device is {}".format(dev))
+        except NoPackets:
+            log_debug("No packets available in recv_packet")
+            gotpkt = False
+        except Shutdown:
+            log_debug("Got shutdown signal")
+            break
+
+        if gotpkt:
+            log_debug("I got a packet {}".format(pkt))
+
+        if dev == "middlebox-eth0":
+            log_debug("Received from blaster")
+            '''
+            Received data packet
+            Should I drop it?
+            If not, modify headers & send to blastee
+            '''
+            net.send_packet("middlebox-eth1", pkt)
+        elif dev == "middlebox-eth1":
+            log_debug("Received from blastee")
+            '''
+            Received ACK
+            Modify headers & send to blaster. Not dropping ACK packets!
+            net.send_packet("middlebox-eth0", pkt)
+            '''
+        else:
+            log_debug("Oops :))")
+
+    net.shutdown()