ft_ping

A from-scratch reimplementation of the ping command in C, matching the inetutils-2.0 reference (ping -V) as required by the 42 ft_ping subject.

It sends ICMP ECHO_REQUEST packets over a raw IPv4 socket, one per second, and reports round-trip times and loss statistics — output, indentation and timing are aligned with inetutils.

Build

make            # builds ./ft_ping
make re         # rebuild from scratch
make clean      # remove object files
make fclean     # remove objects + binary

ft_ping needs raw-socket privileges (CAP_NET_RAW): run it as root, with sudo, after setcap cap_net_raw+ep ./ft_ping, or inside the provided Docker container.

Run

sudo ./ft_ping 8.8.8.8
sudo ./ft_ping -c 4 google.com
sudo ./ft_ping -v --ttl 1 8.8.8.8      # force a "Time to live exceeded" error

Options

Mandatory (per the subject): -v (verbose) and -? (help).

Flag	Long	Meaning
-v	--verbose	verbose output (shows packet id and error IP-header dumps)
-? -h	--help	help list
	--usage	short usage synopsis
-V	--version	version
-c N	--count=N	stop after N packets
-i N	--interval=N	seconds between packets (default 1)
-s N	--size=N	payload size in bytes (default 56)
-q	--quiet	only header + statistics
-w N	--timeout=N	overall deadline in seconds
-W N	--linger=N	seconds to wait for a reply
-t N	--ttl=N	outgoing TTL
-T N	--tos=N	type of service
-f	--flood	flood mode
-l N	--preload=N	send N packets up front

Controlled environment (Docker / Debian)

The subject requires a Debian (>= 7.0) environment with raw-socket privileges. docker/Dockerfile builds a Debian image that also carries the inetutils reference ping, used only by the test suite for side-by-side comparison — ft_ping itself never calls any external ping.

make docker-build    # build the Debian image
make docker-shell    # interactive shell in the container
make test            # build + run the full test suite in the container

Notes

• ping sends one probe per second until interrupted, then prints statistics.

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Resources:

https://networklessons.com/ip-routing/ipv4-packet-header https://sites.uclouvain.be/SystInfo/usr/include/netinet/ip_icmp.h.html https://networklessons.com/ip-routing/icmp-internet-control-message-protocol https://book.huihoo.com/iptables-tutorial/x1078.htm https://www.iana.org/assignments/icmp-parameters/icmp-parameters.xml#icmp-parameters-codes-0 https://datatracker.ietf.org/doc/html/rfc2780 https://support.huawei.com/enterprise/en/doc/EDOC1100174721/9dff3e87/icmp-echo-request-reply-message https://www.rfc-editor.org/info/rfc1071/ https://sites.uclouvain.be/SystInfo/usr/include/netinet/ip.h.html