CS 600.444 Group 7
Project 3: VNS Router
Members: Josh Smith, Leah Hanson, Matt Morris

We have implemented all features of the assignment except Traceroutes to the router (Note a traceroute through the router will send things from the other side back, it just won't include our router in the route.)

Our router has the added bonus of being able to hold an infinite number of flows in the flow table.

Compililation:
Compile using the make command.

Running:
In order to run, specify ./sr -s vns-2.stanford.edu -t 958
Also make sure to use appropriate entries of -u and -a to properly authenticate yourself.

Options:
Firewall: By default the firewall is disabled. In order to turn on the routing table specify -e <interface name>.
For example, to make the outside world outside the firewall specify -e eth0.
Rule Table: By default no rules are used. In order to use a rule table, specify -b <rule table file name>.
The rule table file should contain new-line separated entries of the following form:
<sourceIP> <sourcePort> <dstIP> <dstPort> <proto>
The IP's should be specified as A.B.C.D, and none of their sections should contain leading 0's.
Any of the fields of the rule table can be replaced by a * to denote that this entry is a wildcard.

Implementation Choices Made:
ARP_TIMEOUT = time until the router resends an arp request = 1 second.
              Note the router does not use a timer, so it will not resend an arp request until the first time it receives a packet after 1 second has passed.
ARP_CACHE_TIMEOUT = time until arp cache entry expires = 20 seconds
INIT_TTL = Initial time to live for ICMP packets generated at the router = 255
           This is the maximum value and it seemed best to try to make sure our ICMP packets reach their destination.

Note, we only maintain a single flow table entry for both directions of a flow. A packet coming in either direction will refresh the flow table entry extending its TTD.