pnet_ping.rs

// From https://pastebin.com/m8JMuTWz
extern crate pnet;
 
// use getopts::Options;
use std::env;
use std::net::{IpAddr, Ipv4Addr};
use std::str::FromStr;
use pnet::transport::TransportChannelType::Layer4;
use pnet::transport::TransportProtocol::Ipv4;
use pnet::transport::{transport_channel, ipv4_packet_iter};
use pnet::packet::icmp::{MutableIcmpPacket, IcmpTypes, echo_reply, echo_request, self};
use pnet::packet::ip::IpNextHeaderProtocols;
 
fn create_ping_packet<'a>(sequence_number: u16) -> echo_request::MutableEchoRequestPacket<'a> {
    let mut packet_contents = [0; 48];
    let mut ping_packet = echo_request::MutableEchoRequestPacket::new(&mut packet_contents[20..]).unwrap();
    ping_packet.set_icmp_type(IcmpTypes::EchoRequest);
    ping_packet.set_icmp_code(echo_request::IcmpCodes::NoCode);
    ping_packet.set_identifier(902);
    ping_packet.set_sequence_number(sequence_number);
    ping_packet.set_payload(b"Ring ring");
    ping_packet
}
 
fn main() {
    let args: Vec<String> = env::args().collect();
    let host = args[args.len() - 1].clone();
    let ip_address = IpAddr::V4(Ipv4Addr::from_str(&host).unwrap());
 
    // TODO: Command line arguement checking
    // let mut opts = Options::new();
    // opts.optopt("o", "", "set output file name", "NAME");
    // opts.optflag("h", "help", "print this help menu");
    // let matches = match opts.parse(&args[1..]) {
        // Ok(m) => { m }
        // Err(f) => { panic!(f.to_string()) }
    // };
 
    let icmp_protocol = Layer4(Ipv4(IpNextHeaderProtocols::Icmp));
    let buffer_size = 4096;
    let (mut t_sender, mut t_receiver) = match transport_channel(buffer_size, icmp_protocol) {
        Ok((t_sender, t_receiver)) => (t_sender, t_receiver),
        Err(err) => panic!("{:?}", err),
    };
 
    let mut sequence_number = 0;
    loop {
        let mut iter = ipv4_packet_iter(&mut t_receiver);
        let packet = create_ping_packet(sequence_number);
        match t_sender.send_to(packet, ip_address) {
            Ok(_) => println!("Sent"),
            Err(e) => panic!("{}", e),
        }
        match iter.next() {
            Ok((packet, _)) => println!("Received"),
            Err(e) => println!("{}", e),
        }
        sequence_number += 1;
    }
}

Hi, may I ask why using Layer4 in the protocol instead of Layer3 which IP actually works on?