241 lines
8.6 KiB
Rust
241 lines
8.6 KiB
Rust
use std::fmt;
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use std::net::Ipv4Addr;
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use crate::cal_checksum;
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use crate::error::*;
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use crate::ip::ipv4::protocol::Protocol;
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/// ip协议
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/*
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RFC: 791 https://www.ietf.org/rfc/rfc791.txt
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0 15 31
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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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| 版本(4) | 头部长度(4) | 服务类型(8) | 总字节数(16) |
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+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
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| 标识(16) | 标志(3) | 片偏移(13) |
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+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
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| 生存时间(8) | 协议(8) | 头部校验和(16) |
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+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
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| 源ip地址(32) |
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+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
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| 目的ip地址(32) |
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+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
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| 选项 + 填充 |
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+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
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数据体
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注：头部长度单位是4字节，所以ip头最长60字节，选项最长40字节，选项填充按4字节对齐
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*/
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pub struct IpV4Packet<B> {
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pub buffer: B,
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}
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impl<B: AsRef<[u8]>> IpV4Packet<B> {
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pub fn unchecked(buffer: B) -> Self {
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Self { buffer }
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}
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pub fn new(buffer: B) -> Result<Self> {
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if buffer.as_ref()[0] >> 4 != 4 {
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Err(Error::Unimplemented)?
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}
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if buffer.as_ref().len() < 20 {
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Err(Error::SmallBuffer)?
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}
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let packet = Self::unchecked(buffer);
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if packet.buffer.as_ref().len() < packet.header_len() as usize * 4 {
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Err(Error::SmallBuffer)?
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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]>> IpV4Packet<B> {
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pub fn header(&self) -> &[u8] {
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&self.buffer.as_ref()[..(self.header_len() 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.header_len() as usize * 4)..]
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// match self.protocol() {
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// Protocol::Udp => {
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// let udp = UdpPacket::new(IpAddr::V4(self.source_ip()),
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// IpAddr::V4(self.destination_ip()),
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// &self.buffer.as_ref()[(self.header_len() as usize * 4)..])?;
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// Ok(crate::IpUpperLayer::UDP(udp))
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// }
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// _ => {
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// Ok(crate::IpUpperLayer::Unknown(self.buffer.as_ref()));
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// }
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// }
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}
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}
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impl<B: AsRef<[u8]> + AsMut<[u8]>> IpV4Packet<B> {
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pub fn header_mut(&mut self) -> &mut [u8] {
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let len = self.header_len() as usize * 4;
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&mut self.buffer.as_mut()[..len]
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}
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pub fn payload_mut(&mut self) -> &mut [u8] {
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let len = self.header_len() as usize * 4;
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&mut self.buffer.as_mut()[len..]
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}
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pub fn set_source_ip(&mut self, value: Ipv4Addr) {
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self.header_mut()[12..16].copy_from_slice(&value.octets());
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}
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pub fn set_destination_ip(&mut self, value: Ipv4Addr) {
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self.header_mut()[16..20].copy_from_slice(&value.octets());
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}
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fn set_checksum(&mut self, value: u16) {
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self.header_mut()[10..12].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(cal_checksum(self.header()))
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}
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}
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impl<B: AsRef<[u8]>> IpV4Packet<B> {
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/// 版本号，ipv4的为4
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pub fn version(&self) -> u8 {
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self.buffer.as_ref()[0] >> 4
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}
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/// 头部长度，以4字节为单位
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pub fn header_len(&self) -> u8 {
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self.buffer.as_ref()[0] & 0b1111
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}
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/// 差异化服务编码点
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///
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/// 类别(3)+丢失概率(2)+用途(1)
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///
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///
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/// 类别子字段值 | 名称
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/// ---|:---
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/// 000 | 常规(Routine)
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/// 001 | 优先(Priority)
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/// 010 | 立即(Immediate)
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/// 011 | 瞬间(Flash)
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/// 100 | 瞬间覆盖(Flash Override)
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/// 101 | 严重(CRITIC/ECP)
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/// 110 | 网间控制(Internetwork Control)
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/// 111 | 网络控制(Network Control)
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///
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///
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/// 参考：https://www.modb.pro/db/477116
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pub fn dscp(&self) -> u8 {
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self.buffer.as_ref()[1] >> 2
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}
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/// 显示拥塞 00：发送主机不支持ECN 01或者10：发送主机支持ECN 11：路由器正在经历拥塞
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pub fn ecn(&self) -> u8 {
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self.buffer.as_ref()[1] & 0b11
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}
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/// ip报总字节数
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pub fn length(&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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/// 标识. ip报文在数据链路层可能会被拆分，同一报文的不同分组标识字段相同
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pub fn id(&self) -> u16 {
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u16::from_be_bytes(self.buffer.as_ref()[4..6].try_into().unwrap())
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}
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/// 标志 3位.
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/// 第1位没有使用
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/// 第2位表示不分段位（DF）
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/// 0:允许数据报分段
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/// 1:数据报不能分段
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/// 置1之后路由器不能对其分段处理，如果超过MTU值则路由器不能对其转发将其丢弃，并向源点发送错误消息
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/// 第3位表示更多段位
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/// 0:数据包后面没有包，该包为最后的包
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/// 1:数据包后面有更多的包
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pub fn flags(&self) -> u8 {
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self.buffer.as_ref()[6] >> 5
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}
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/// 片偏移 13位.
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/// 以字节为单位,用于指明分段起始点相对于包头起始点的偏移量
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/// 由于分段到达时可能错序，所以分段的偏移字段可以使接收者按照正确的顺序重组数据包
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pub fn offset(&self) -> u16 {
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u16::from_be_bytes(self.buffer.as_ref()[6..8].try_into().unwrap()) & 0x1fff
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}
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/// 生存时间.
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/// 每一跳 减1 到0了则会被丢弃
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pub fn ttl(&self) -> u8 {
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self.buffer.as_ref()[8]
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}
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/// 协议.
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pub fn protocol(&self) -> Protocol {
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self.buffer.as_ref()[9].into()
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}
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/// 首部校验和
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pub fn checksum(&self) -> u16 {
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u16::from_be_bytes(self.buffer.as_ref()[10..12].try_into().unwrap())
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}
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/// 验证校验和
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///
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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 || cal_checksum(self.header()) == 0
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}
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/// 源ip.
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pub fn source_ip(&self) -> Ipv4Addr {
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Ipv4Addr::new(
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self.buffer.as_ref()[12],
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self.buffer.as_ref()[13],
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self.buffer.as_ref()[14],
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self.buffer.as_ref()[15],
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)
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}
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/// 目标ip.
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pub fn destination_ip(&self) -> Ipv4Addr {
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Ipv4Addr::new(
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self.buffer.as_ref()[16],
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self.buffer.as_ref()[17],
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self.buffer.as_ref()[18],
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self.buffer.as_ref()[19],
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)
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}
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/// 选项.
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pub fn options(&self) -> &[u8] {
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&self.buffer.as_ref()[20..(self.header_len() as usize * 4)]
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}
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}
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impl<B: AsRef<[u8]>> fmt::Debug for IpV4Packet<B> {
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fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
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f.debug_struct("ip::v4::Packet")
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.field("version", &self.version())
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.field("header_len", &self.header_len())
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.field("dscp", &self.dscp())
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.field("ecn", &self.ecn())
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.field("length", &self.length())
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.field("id", &self.id())
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.field("flags", &self.flags())
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.field("offset", &self.offset())
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.field("ttl", &self.ttl())
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.field("protocol", &self.protocol())
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.field("checksum", &self.checksum())
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.field("is_valid", &self.is_valid())
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.field("source", &self.source_ip())
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.field("destination", &self.destination_ip())
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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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