Basic Encapsulation Example (#64)

* Adding initial implementation of basic_encap example

* Updated basic_encap example to count the number of valid packets

* Updated basic_encap example to put encapsulation layer after Ethernet
header.

* Added solution file for basic_encap example

* Changed the name of the basic_encap example to basic_tunnel and called
the new header myTunnel. Also changed the myTunnel field names slightly.

P4D2_2017_Fall/exercises/basic_tunnel/receive.py

@@ -0,0 +1,43 @@
+#!/usr/bin/env python
+import sys
+import struct
+import os
+
+from scapy.all import sniff, sendp, hexdump, get_if_list, get_if_hwaddr
+from scapy.all import Packet, IPOption
+from scapy.all import ShortField, IntField, LongField, BitField, FieldListField, FieldLenField
+from scapy.all import IP, UDP, Raw
+from scapy.layers.inet import _IPOption_HDR
+from myTunnel_header import MyTunnel
+
+def get_if():
+    ifs=get_if_list()
+    iface=None
+    for i in get_if_list():
+        if "eth0" in i:
+            iface=i
+            break;
+    if not iface:
+        print "Cannot find eth0 interface"
+        exit(1)
+    return iface
+
+def handle_pkt(pkt):
+    if MyTunnel in pkt:
+        print "got a packet"
+        pkt.show2()
+#        hexdump(pkt)
+#        print "len(pkt) = ", len(pkt)
+        sys.stdout.flush()
+
+
+def main():
+    ifaces = filter(lambda i: 'eth' in i, os.listdir('/sys/class/net/'))
+    iface = ifaces[0]
+    print "sniffing on %s" % iface
+    sys.stdout.flush()
+    sniff(iface = iface,
+          prn = lambda x: handle_pkt(x))
+
+if __name__ == '__main__':
+    main()