0225-ping 请求报文

环境

• Time 2022-11-20
• WSL-Ubuntu 22.04
• Rust 1.65.0
• pnet 0.31.0
• tun-tap 0.1.3

前言

说明

参考：https://docs.rs/pnet/latest/pnet/index.html
RFC 792

目标

查看 ping 请求报文的格式，ping 基于 IP 报文。

ping 命令

ping -I tun0 172.24.49.106

root@jiangbo12490:~# ping  -I tun0  172.24.49.106
PING 172.24.49.106 (172.24.49.106) from 172.24.49.244 tun0: 56(84) bytes of data.
^C
--- 172.24.49.106 ping statistics ---
1 packets transmitted, 0 received, 100% packet loss, time 0ms

main.rs

use pnet::packet::icmp::echo_request::EchoRequestPacket;
use pnet::packet::icmp::{IcmpPacket, IcmpTypes};
use pnet::packet::{ip::IpNextHeaderProtocols, ipv4::Ipv4Packet};
use tun_tap::{Iface, Mode};

fn main() -> std::io::Result<()> {
    let iface = Iface::without_packet_info("tun0", Mode::Tun)?;

    let mut buffer = vec![0; 1500];

    loop {
        let size = iface.recv(&mut buffer)?;
        let packet = Ipv4Packet::new(&buffer).unwrap();

        if packet.get_version() == 6 {
            println!("IPv6 packet, continue");
            continue;
        }

        if packet.get_next_level_protocol() != IpNextHeaderProtocols::Icmp {
            println!("not icmp packet, continue");
            continue;
        }

        // 因为头部长度的单位是 4 字节
        let length = packet.get_header_length() as usize * 4;
        let packet = IcmpPacket::new(&buffer[length..]).unwrap();

        // 类型 8  表示 EchoRequest，0 表示回应
        println!("type {:?}", packet.get_icmp_type());
        // ping 程序的请求和响应都为 0
        println!("code {:?}", packet.get_icmp_code());
        // 校验和
        println!("checksum {:?}", packet.get_checksum());

        if packet.get_icmp_type() != IcmpTypes::EchoRequest {
            println!("not icmp request, continue");
        }

        let packet = EchoRequestPacket::new(&buffer[length..]).unwrap();
        // 类型 8  表示 EchoRequest，0 表示回应
        println!("type {:?}", packet.get_icmp_type());
        // 标识符
        println!("identifier {:?}", packet.get_identifier());
        // 序列号
        println!("sequence_number {:?}", packet.get_sequence_number());
        println!("length: {}, {:?}", size, &buffer[..size]);
    }
}

程序输出

type IcmpType(8)
code IcmpCode(0)
checksum 48637
type IcmpType(8)
identifier 24612
sequence_number 1
length: 84, [69, 0, 0, 84, 194, 81, 64, 0, 64, 1, 188, 200, 172, 24, 49, 244, 172, 24, 49, 106, 8, 0, 189, 253, 96, 36, 0, 1, 241, 40, 126, 99, 0, 0, 0, 0, 170, 125, 1, 0, 0, 0, 0, 0, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51, 52, 53, 54, 55]

总结

了解 ping 请求报文的格式，其中包含 type，code，checksum，identifier，sequence_number 等。

附录