Router Dataplane

Description

The entire project stands under the copyright of University Politehnica of Bucharest, PCOM 2023, being a graded assignment. The implementation uses Miniet for simulating the network in which the router operates. The implementation is targeted at constructing the dataplane of a router which is responsible with forwarding. The following components are implemented:

• Forwarding
• LPM (Longest Prefix Match)
• ARP
• ICMP

Usage

• Start Mininet topology:

sudo python3 topo.py
# topology is considered as follows:
host0                           host2     
      \                       /
       router0 ------- router1 
      /                       \
host1                           host3

• Start router:

make run_router0
make run_router1

• Commands for clients:

ping, arping, netcat

Structures

Located and described in include dir.

Forwarding

Workflow:

• check Layer2 data <=> packet has router or broadcast as destination
• chech packet type: ARP / ICMP
• verfiy Checksum & TTL
• modify IP header (TTL & Checksum) and Ethernet header (detination & source)
• packet reconstruction: ETH_HDR | IP_HDR | PAYLOAD => sent to next hop

LPM

Trie implementation

• initialize with parse_trie() which creates new nodes in trie for each entry in routing table
• address addition works on binary tree model
• representation: address "addr/len" = firest len bits in binary form of addr

ARP

Received

• router can interpret REQUEST/REPLY
• REPLY: cache mac address recieved and send packets waiting for that address
• REQUEST: if router is destination, send ARP REPLY

Sent

• send ARP REQUEST if the mac address asociated with the destination ip of the packet recieved isnt's known and add packets with that target to a waiting list
• send ARP REPLY if router is target

ICMP

• if router is destination of icmp, create and send icmp_reply()
• TIMEOUT if TTL < 2
• DESTINATION UNREACHABLE if destination can't be found in routing table