Ping

A minimal implementation of the ping command

Quick start

make

./ping google.com
64 bytes from sfo07s16-in-f78.1e100.net (216.58.195.78): icmp_seq=1 ttl=61 time=4.859 ms
64 bytes from sfo07s16-in-f78.1e100.net (216.58.195.78): icmp_seq=2 ttl=61 time=4.991 ms
64 bytes from sfo07s16-in-f78.1e100.net (216.58.195.78): icmp_seq=3 ttl=61 time=4.875 ms
64 bytes from sfo07s16-in-f78.1e100.net (216.58.195.78): icmp_seq=4 ttl=61 time=4.843 ms
^C
--- google.com ping statistics ---
4 packets transmitted, 4 packets received, 0.0% packet loss
rtt min/avg/max/mdev = 4.843/4.892/4.991/??? ms

You must be root to run the command. A dockerfile is provided to run inside a Debian VM:

docker-machine create --driver virtualbox ping
docker-machine start ping
eval $(docker-machine env ping)
docker build -t local/ping .
docker run -itv `pwd`:/ping local/ping
make

Usage

usage: ./ping host

Implementation

This program uses a raw ICMP socket to sent an ICMP ECHO request to the destination with the sending time as a payload. It then waits for the matching ICMP response and calculates the time difference. The process is repeated untill a SIGINT signal is captured and the program exits after displaying statistics.

Internals

The core of the project is layered into 3 modules with clear and minimally-overlapping roles. More specific information can be found in the header files.

icmp_socket

Responsible for initializing the socket, and sending/receiving data. Doesn't care what is being sent or recieved.

echo

Manages the ICMP ECHO packet and filtering of incoming packets. Doesn't care how the request is sent or received nor what happens to the payload.

ping

Manages the main loop, request/response lifecyle, statistics and user interface.