147 lines
3.7 KiB
Rust
147 lines
3.7 KiB
Rust
use std::net::Ipv4Addr;
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use byteorder::BigEndian;
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use byteorder::ReadBytesExt;
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pub mod icmp;
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pub mod igmp;
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pub mod ip;
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pub mod tcp;
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pub mod udp;
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pub mod ethernet;
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pub mod arp;
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// pub enum IpUpperLayer<B> {
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// UDP(UdpPacket<B>),
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// Unknown(B),
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// }
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//
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// impl<B: AsRef<[u8]>> fmt::Debug for IpUpperLayer<B> {
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// fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
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// match self {
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// IpUpperLayer::UDP(p) => {
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// f.debug_struct("udp::Packet")
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// .field("data", p).finish()
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// }
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// IpUpperLayer::Unknown(p) => {
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// f.debug_struct("Unknown")
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// .field("data", &p.as_ref()).finish()
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// }
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// }
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// }
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// }
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/// https://datatracker.ietf.org/doc/html/rfc1071 4.1节
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///
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/// 计算校验和，各协议都是通用的
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/// 计算：
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/// 首先将校验和置0，然后对首部每个16位数进行二进制反码求和，
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/// 得到校验和之后，持续取高16位加到低16位，直到高16位全为0
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/// 最后取反
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///
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/// 校验：
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/// 在已有校验和的情况下，再计算校验和，正确的数据计算得到的值为0
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/*
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unsigned short getChecksum(unsigned short * iphead, int count)
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{
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unsigned long int sum = 0;
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unsigned short checksum = 0;
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printf("\nStarting adress: %p\n", iphead);
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while(count > 1) {
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sum += * (unsigned short *) (iphead);
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count -=2;
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printf("a: %p, content is: %d, new sum: %ld\n", iphead, (unsigned short) *(iphead), sum);
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iphead++;
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}
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if(count > 0) {
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sum += * (unsigned short *) (iphead);
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}
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while(sum >> 16) {
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sum = (sum & 0xffff) + (sum >> 16);
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}
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checksum = ~sum;
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return checksum;
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}
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*/
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pub fn cal_checksum(buffer: &[u8]) -> u16 {
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use std::io::Cursor;
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let mut sum = 0;
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let length = buffer.len();
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let mut buffer = Cursor::new(buffer);
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while let Ok(value) = buffer.read_u16::<BigEndian>() {
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sum += u32::from(value);
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}
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if length & 1 == 1 {
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//奇数,说明还有一位,不足的补0
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sum += u32c(buffer.read_u8().unwrap(), 0);
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}
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while sum >> 16 != 0 {
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sum = (sum & 0xffff) + (sum >> 16);
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}
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!sum as u16
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}
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/// ipv4上层协议校验和计算方式
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/// ipv4 udp伪首部 用于参与计算首部校验和
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/*
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0 7 8 15 16 23 24 31
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+--------+--------+--------+--------+
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| source address |
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+--------+--------+--------+--------+
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| destination address |
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+--------+--------+--------+--------+
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| zero |protocol| length |
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+--------+--------+--------+--------+
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*/
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pub fn ipv4_cal_checksum(
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buffer: &[u8],
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src_ip: &Ipv4Addr,
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dest_ip: &Ipv4Addr,
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protocol: u8,
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length: u16,
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) -> u16 {
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use std::io::Cursor;
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let mut sum = 0;
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let src_ip = src_ip.octets();
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sum += u32c(src_ip[0], src_ip[1]);
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sum += u32c(src_ip[2], src_ip[3]);
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let dest_ip = dest_ip.octets();
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sum += u32c(dest_ip[0], dest_ip[1]);
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sum += u32c(dest_ip[2], dest_ip[3]);
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sum += u32c(0, protocol);
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sum += length as u32;
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let mut buffer = Cursor::new(buffer);
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while let Ok(value) = buffer.read_u16::<BigEndian>() {
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sum += u32::from(value);
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}
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if length & 1 == 1 {
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//奇数,说明还有一位
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sum += u32c(buffer.read_u8().unwrap(), 0);
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}
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while sum >> 16 != 0 {
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sum = (sum & 0xffff) + (sum >> 16);
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}
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!sum as u16
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}
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#[inline]
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fn u32c(x: u8, y: u8) -> u32 {
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((x as u32) << 8) | y as u32
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}
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#[cfg(test)]
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mod tests {
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use super::*;
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#[test]
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fn it_works() {
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let sum = cal_checksum(&[255, 255]);
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println!("{:?}", sum);
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}
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}
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