Router Final Project

Adam Wolnikowski

16 November 2020

Final project submission for CPSC 435 at Yale University with Prof. Robert Soule

Implementation of an internet router control- and data-plane, in python and p4, respectively.

main.py instantiates the following topology:

(h2)--(r2)-----(r3)--(h3)
        |     / |
        |    /  |
        |   /   |
        |  /    |
        | /     |
(h1)--(r1)-----(r4)--(h4)

Data-Plane Basic Requirements

• Provide a routing table that can store IP address/prefix pairs with their associated port and next-hop IP address.
• Use the routing table to perform a longest prefix match on destination IP addresses and return the appropriate egress port and next-hop address (or 0.0.0.0 for a directly attached destination).
  • NOTE: We will use a ternary match table for the routing table because LPM tables are not fully supported by SDNet yet.
• Provide an ARP table that can store at least 64 entries. This will accept an IP address as a search key and will return the associated MAC address (if found). This table is modified by the software, which runs its own ARP protocol.
• Provide a “local IP address table”. This will accept an IP address as a search key and will return a signal that indicates whether the correspond address was found. This table is used to identify IP addresses that should be forwarded to the CPU.
• Decode incoming IP packets and perform the operations required by a router. These include (but are not limited to):
  • verify that the existing checksum and TTL are valid
  • look up the next-hop port and IP address in the route table
  • look up the MAC address of the next-hop in the ARP table
  • set the src MAC address based on the port the packet is departing from
  • decrement TTL
  • calculate a new IP checksum
  • transmit the new packet via the appropriate egress port
  • local IP packets (destined for the router) should be sent to the software
  • PWOSPF packets should be sent to the software
  • packets for which no matching entry is found in the routing table should be sent to the software
  • any packets that the hardware cannot deal with should be forwarded to the CPU. (e.g. not Version 4 IP)
• Provide counters for the following:
  • IP packets
  • ARP packets
  • Packets forwarded to the control-plane

Control-Plane Basic Requirements

• Sending ARP requests
• Responding to ARP requests (chose to implement in control plane so request sender's info can be cached in ARP table)
• Updating entries in the hardware ARP cache (not possible with current API)
• Timing out entries in the hardware ARP cache
• Queuing packets pending ARP replies
• Responding to ICMP echo requests
• Generating ICMP host unreachable packets
• Handling corrupted or otherwise incorrect IP packets
• Building the forwarding table via a dynamic routing protocol (PWOSPF)
• Support static routing table entries in addition to the routes computed by PWOSPF
• Handling all packets addressed directly to the router

Initial tests:

• Is your router forwarding correctly with statically configured table entries?
• Can you ping each of the router's interfaces?
• Is the router responding to ARP requests?

Running

First, make sure you have p4app (which requires Docker):

cd ~/
git clone --branch rc-2.0.0 https://github.com/p4lang/p4app.git

Then run this p4app:

~/p4app/p4app run router.p4app