ping

This is a rather basic implementation of the ping command in C. It was created for learning more about raw sockets and how ping works (and for fun).

Features:

• Cross-platform: can compile and run on Windows (MSVC, Cygwin), Linux, macOS
• Supports IPv6
• Displays time with microsecond precision

Example usage:

$ ./ping google.com
PING google.com (142.250.74.206)
Received reply from 142.250.74.206: seq=0, time=103.307 ms
Received reply from 142.250.74.206: seq=1, time=91.200 ms
Received reply from 142.250.74.206: seq=2, time=103.080 ms
Received reply from 142.250.74.206: seq=3, time=94.531 ms
Received reply from 142.250.74.206: seq=4, time=92.204 ms
^C

ping accepts only one argument - the name of the host to ping.

Building

To build ping you'll need a C89 compiler and CMake. Supported platforms include Linux, Mac OS X and Cygwin.

After you cloned this repo run the following commands to build an executable:

cd ping
mkdir build && cd build
cmake ../ -G "Unix Makefiles"
make

Running

Use of raw sockets usually requires administrative privileges, therefore you will need to run ping as root:

sudo ./ping google.com

There is also a way to make it run without typing sudo every time: set the suid bit on the executable and change its owner to root:

sudo chmod +s ./ping
sudo chown root ./ping

After starting ping, it will run indefinitely until you interrupt it, e.g. by doing Ctrl-C in the terminal.

Scripts

The scripts directory contains a couple of scripts to aid debugging:

• capture.sh - captures ICMP traffic with tcpdump and saves it to ping.pcap (needs to be run as root)
• dump.sh - prints the contents of ping.pcap in a nice form (tcpdump may actually display helpful errors there, like a miscalculated checksum)