179 lines
6.5 KiB
Rust
179 lines
6.5 KiB
Rust
use std::net::Ipv4Addr;
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use std::{fmt, io};
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use crate::tcp::Flags;
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/// tcp
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/*
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https://www.rfc-editor.org/rfc/rfc793
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0 1 2 3
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0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
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+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
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| Source Port | Destination Port |
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+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
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| Sequence Number |
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+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
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| Acknowledgment Number |
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+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
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| Data | |U|A|P|R|S|F| |
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| Offset| Reserved |R|C|S|S|Y|I| Window |
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| | |G|K|H|T|N|N| |
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+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
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| Checksum | Urgent Pointer |
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+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
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| Options | Padding |
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+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
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| data |
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+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
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Source Port: 16位 源端口
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Destination Port:16位 目的端口
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Sequence Number:32位 序列号，如果存在syn标志，则为初始序列号
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Acknowledgment Number:32位 如果设置了ack标志，这个表示确认收到的序号
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Data Offset:4位 数据的开始偏移位，单位是4字节
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Reserved:6位 未使用，全零
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控制位：6位 从左到右
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URG: 紧急指针 表示数据要优先处理
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ACK: 确认位
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PSH: 推送 要求把数据尽快的交给应用层，不做处理
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RST: 重置连接
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SYN: 同步序列号
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FIN: 结束发送
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Window: 16位 能接收的数据大小
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Checksum:16位 校验和，需要加入伪首部
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Urgent Pointer:16位 紧急指针
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Options+Padding:32位整数倍，最多40个字节
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*/
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pub struct TcpPacket<B> {
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source_ip: Ipv4Addr,
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destination_ip: Ipv4Addr,
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buffer: B,
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}
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impl<B: AsRef<[u8]>> TcpPacket<B> {
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pub fn unchecked(source_ip: Ipv4Addr, destination_ip: Ipv4Addr, buffer: B) -> TcpPacket<B> {
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TcpPacket {
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source_ip,
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destination_ip,
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buffer,
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}
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}
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pub fn new(
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source_ip: Ipv4Addr,
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destination_ip: Ipv4Addr,
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buffer: B,
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) -> io::Result<TcpPacket<B>> {
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let packet = TcpPacket::unchecked(source_ip, destination_ip, buffer);
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if packet.buffer.as_ref().len() < 20 {
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Err(io::Error::from(io::ErrorKind::InvalidData))?;
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}
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if packet.buffer.as_ref().len() < packet.data_offset() as usize * 4 {
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Err(io::Error::from(io::ErrorKind::InvalidData))?;
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}
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Ok(packet)
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}
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}
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impl<B: AsRef<[u8]> + AsMut<[u8]>> TcpPacket<B> {
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pub fn set_source_ip(&mut self, value: Ipv4Addr) {
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self.source_ip = value;
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}
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pub fn set_destination_ip(&mut self, value: Ipv4Addr) {
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self.destination_ip = value;
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}
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}
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impl<B: AsRef<[u8]> + AsMut<[u8]>> TcpPacket<B> {
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fn set_checksum(&mut self, value: u16) {
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self.buffer.as_mut()[16..18].copy_from_slice(&value.to_be_bytes())
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}
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pub fn set_source_port(&mut self, value: u16) {
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self.buffer.as_mut()[0..2].copy_from_slice(&value.to_be_bytes())
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}
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pub fn set_destination_port(&mut self, value: u16) {
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self.buffer.as_mut()[2..4].copy_from_slice(&value.to_be_bytes())
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}
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/// 更新校验和
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pub fn update_checksum(&mut self) {
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//先将校验和置0
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self.set_checksum(0);
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self.set_checksum(self.cal_checksum())
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}
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}
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impl<B: AsRef<[u8]>> TcpPacket<B> {
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/// 源端口
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pub fn source_port(&self) -> u16 {
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u16::from_be_bytes(self.buffer.as_ref()[0..2].try_into().unwrap())
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}
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/// 目标端口
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pub fn destination_port(&self) -> u16 {
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u16::from_be_bytes(self.buffer.as_ref()[2..4].try_into().unwrap())
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}
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/// 序列号
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pub fn sequence(&self) -> u32 {
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u32::from_be_bytes(self.buffer.as_ref()[4..8].try_into().unwrap())
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}
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/// 确认号
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pub fn acknowledgment(&self) -> u32 {
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u32::from_be_bytes(self.buffer.as_ref()[8..12].try_into().unwrap())
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}
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/// 数据偏移 4字节为单位
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pub fn data_offset(&self) -> u8 {
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self.buffer.as_ref()[12] >> 4
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}
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pub fn flags(&self) -> Flags {
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Flags(self.buffer.as_ref()[13])
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}
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pub fn window(&self) -> u16 {
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u16::from_be_bytes(self.buffer.as_ref()[14..16].try_into().unwrap())
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}
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pub fn checksum(&self) -> u16 {
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u16::from_be_bytes(self.buffer.as_ref()[16..18].try_into().unwrap())
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}
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/// 验证校验和,ipv4中为0表示不使用校验和，ipv6校验和不能为0
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/// TCP/IP协议栈不会自己计算校验和，而是简单地将一个空的校验和字段(零或随机填充)交给网卡硬件。
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/// 所以抓到发出去的包校验和可能是错误的
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pub fn is_valid(&self) -> bool {
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self.checksum() == 0 || self.cal_checksum() == 0
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}
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fn cal_checksum(&self) -> u16 {
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crate::ipv4_cal_checksum(
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self.buffer.as_ref(),
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&self.source_ip,
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&self.destination_ip,
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6,
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)
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}
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pub fn urgent_pointer(&self) -> u16 {
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u16::from_be_bytes(self.buffer.as_ref()[18..20].try_into().unwrap())
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}
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pub fn options(&self) -> &[u8] {
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&self.buffer.as_ref()[20..(self.data_offset() as usize * 4)]
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}
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pub fn payload(&self) -> &[u8] {
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&self.buffer.as_ref()[(self.data_offset() as usize * 4)..]
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}
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}
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impl<B: AsRef<[u8]>> fmt::Debug for TcpPacket<B> {
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fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
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f.debug_struct("tcp::Packet")
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.field("source", &self.source_port())
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.field("destination", &self.destination_port())
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.field("sequence", &self.sequence())
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.field("acknowledgment", &self.acknowledgment())
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.field("offset", &self.data_offset())
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.field("flags", &self.flags())
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.field("window", &self.window())
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.field("checksum", &self.checksum())
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.field("is_valid", &self.is_valid())
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.field("pointer", &self.urgent_pointer())
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.field("options", &self.options())
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.field("payload", &self.payload())
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.finish()
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}
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}
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