1224 lines
43 KiB
Rust
1224 lines
43 KiB
Rust
use core::{i32, ops, cmp, fmt};
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use byteorder::{ByteOrder, NetworkEndian};
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use crate::{Error, Result};
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use crate::phy::ChecksumCapabilities;
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use crate::wire::{IpProtocol, IpAddress};
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use crate::wire::ip::checksum;
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/// A TCP sequence number.
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///
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/// A sequence number is a monotonically advancing integer modulo 2<sup>32</sup>.
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/// Sequence numbers do not have a discontiguity when compared pairwise across a signed overflow.
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#[derive(Debug, PartialEq, Eq, Clone, Copy, Default)]
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pub struct SeqNumber(pub i32);
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impl fmt::Display for SeqNumber {
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fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
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write!(f, "{}", self.0 as u32)
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}
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}
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impl ops::Add<usize> for SeqNumber {
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type Output = SeqNumber;
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fn add(self, rhs: usize) -> SeqNumber {
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if rhs > i32::MAX as usize {
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panic!("attempt to add to sequence number with unsigned overflow")
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}
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SeqNumber(self.0.wrapping_add(rhs as i32))
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}
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}
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impl ops::Sub<usize> for SeqNumber {
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type Output = SeqNumber;
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fn sub(self, rhs: usize) -> SeqNumber {
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if rhs > i32::MAX as usize {
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panic!("attempt to subtract to sequence number with unsigned overflow")
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}
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SeqNumber(self.0.wrapping_sub(rhs as i32))
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}
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}
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impl ops::AddAssign<usize> for SeqNumber {
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fn add_assign(&mut self, rhs: usize) {
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*self = *self + rhs;
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}
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}
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impl ops::Sub for SeqNumber {
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type Output = usize;
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fn sub(self, rhs: SeqNumber) -> usize {
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let result = self.0.wrapping_sub(rhs.0);
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if result < 0 {
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panic!("attempt to subtract sequence numbers with underflow")
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}
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result as usize
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}
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}
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impl cmp::PartialOrd for SeqNumber {
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fn partial_cmp(&self, other: &SeqNumber) -> Option<cmp::Ordering> {
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self.0.wrapping_sub(other.0).partial_cmp(&0)
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}
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}
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/// A read/write wrapper around a Transmission Control Protocol packet buffer.
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#[derive(Debug, PartialEq, Clone)]
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pub struct Packet<T: AsRef<[u8]>> {
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buffer: T
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}
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mod field {
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#![allow(non_snake_case)]
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use crate::wire::field::*;
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pub const SRC_PORT: Field = 0..2;
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pub const DST_PORT: Field = 2..4;
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pub const SEQ_NUM: Field = 4..8;
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pub const ACK_NUM: Field = 8..12;
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pub const FLAGS: Field = 12..14;
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pub const WIN_SIZE: Field = 14..16;
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pub const CHECKSUM: Field = 16..18;
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pub const URGENT: Field = 18..20;
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pub fn OPTIONS(length: u8) -> Field {
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URGENT.end..(length as usize)
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}
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pub const FLG_FIN: u16 = 0x001;
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pub const FLG_SYN: u16 = 0x002;
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pub const FLG_RST: u16 = 0x004;
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pub const FLG_PSH: u16 = 0x008;
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pub const FLG_ACK: u16 = 0x010;
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pub const FLG_URG: u16 = 0x020;
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pub const FLG_ECE: u16 = 0x040;
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pub const FLG_CWR: u16 = 0x080;
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pub const FLG_NS: u16 = 0x100;
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pub const OPT_END: u8 = 0x00;
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pub const OPT_NOP: u8 = 0x01;
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pub const OPT_MSS: u8 = 0x02;
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pub const OPT_WS: u8 = 0x03;
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pub const OPT_SACKPERM: u8 = 0x04;
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pub const OPT_SACKRNG: u8 = 0x05;
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}
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impl<T: AsRef<[u8]>> Packet<T> {
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/// Imbue a raw octet buffer with TCP packet structure.
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pub fn new_unchecked(buffer: T) -> Packet<T> {
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Packet { buffer }
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}
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/// Shorthand for a combination of [new_unchecked] and [check_len].
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///
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/// [new_unchecked]: #method.new_unchecked
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/// [check_len]: #method.check_len
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pub fn new_checked(buffer: T) -> Result<Packet<T>> {
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let packet = Self::new_unchecked(buffer);
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packet.check_len()?;
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Ok(packet)
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}
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/// Ensure that no accessor method will panic if called.
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/// Returns `Err(Error::Truncated)` if the buffer is too short.
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/// Returns `Err(Error::Malformed)` if the header length field has a value smaller
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/// than the minimal header length.
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///
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/// The result of this check is invalidated by calling [set_header_len].
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///
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/// [set_header_len]: #method.set_header_len
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pub fn check_len(&self) -> Result<()> {
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let len = self.buffer.as_ref().len();
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if len < field::URGENT.end {
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Err(Error::Truncated)
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} else {
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let header_len = self.header_len() as usize;
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if len < header_len {
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Err(Error::Truncated)
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} else if header_len < field::URGENT.end {
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Err(Error::Malformed)
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} else {
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Ok(())
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}
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}
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}
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/// Consume the packet, returning the underlying buffer.
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pub fn into_inner(self) -> T {
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self.buffer
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}
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/// Return the source port field.
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#[inline]
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pub fn src_port(&self) -> u16 {
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let data = self.buffer.as_ref();
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NetworkEndian::read_u16(&data[field::SRC_PORT])
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}
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/// Return the destination port field.
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#[inline]
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pub fn dst_port(&self) -> u16 {
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let data = self.buffer.as_ref();
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NetworkEndian::read_u16(&data[field::DST_PORT])
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}
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/// Return the sequence number field.
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#[inline]
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pub fn seq_number(&self) -> SeqNumber {
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let data = self.buffer.as_ref();
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SeqNumber(NetworkEndian::read_i32(&data[field::SEQ_NUM]))
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}
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/// Return the acknowledgement number field.
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#[inline]
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pub fn ack_number(&self) -> SeqNumber {
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let data = self.buffer.as_ref();
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SeqNumber(NetworkEndian::read_i32(&data[field::ACK_NUM]))
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}
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/// Return the FIN flag.
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#[inline]
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pub fn fin(&self) -> bool {
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let data = self.buffer.as_ref();
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let raw = NetworkEndian::read_u16(&data[field::FLAGS]);
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raw & field::FLG_FIN != 0
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}
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/// Return the SYN flag.
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#[inline]
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pub fn syn(&self) -> bool {
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let data = self.buffer.as_ref();
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let raw = NetworkEndian::read_u16(&data[field::FLAGS]);
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raw & field::FLG_SYN != 0
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}
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/// Return the RST flag.
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#[inline]
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pub fn rst(&self) -> bool {
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let data = self.buffer.as_ref();
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let raw = NetworkEndian::read_u16(&data[field::FLAGS]);
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raw & field::FLG_RST != 0
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}
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/// Return the PSH flag.
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#[inline]
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pub fn psh(&self) -> bool {
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let data = self.buffer.as_ref();
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let raw = NetworkEndian::read_u16(&data[field::FLAGS]);
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raw & field::FLG_PSH != 0
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}
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/// Return the ACK flag.
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#[inline]
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pub fn ack(&self) -> bool {
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let data = self.buffer.as_ref();
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let raw = NetworkEndian::read_u16(&data[field::FLAGS]);
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raw & field::FLG_ACK != 0
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}
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/// Return the URG flag.
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#[inline]
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pub fn urg(&self) -> bool {
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let data = self.buffer.as_ref();
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let raw = NetworkEndian::read_u16(&data[field::FLAGS]);
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raw & field::FLG_URG != 0
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}
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/// Return the ECE flag.
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#[inline]
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pub fn ece(&self) -> bool {
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let data = self.buffer.as_ref();
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let raw = NetworkEndian::read_u16(&data[field::FLAGS]);
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raw & field::FLG_ECE != 0
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}
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/// Return the CWR flag.
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#[inline]
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pub fn cwr(&self) -> bool {
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let data = self.buffer.as_ref();
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let raw = NetworkEndian::read_u16(&data[field::FLAGS]);
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raw & field::FLG_CWR != 0
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}
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/// Return the NS flag.
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#[inline]
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pub fn ns(&self) -> bool {
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let data = self.buffer.as_ref();
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let raw = NetworkEndian::read_u16(&data[field::FLAGS]);
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raw & field::FLG_NS != 0
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}
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/// Return the header length, in octets.
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#[inline]
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pub fn header_len(&self) -> u8 {
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let data = self.buffer.as_ref();
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let raw = NetworkEndian::read_u16(&data[field::FLAGS]);
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((raw >> 12) * 4) as u8
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}
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/// Return the window size field.
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#[inline]
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pub fn window_len(&self) -> u16 {
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let data = self.buffer.as_ref();
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NetworkEndian::read_u16(&data[field::WIN_SIZE])
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}
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/// Return the checksum field.
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#[inline]
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pub fn checksum(&self) -> u16 {
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let data = self.buffer.as_ref();
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NetworkEndian::read_u16(&data[field::CHECKSUM])
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}
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/// Return the urgent pointer field.
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#[inline]
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pub fn urgent_at(&self) -> u16 {
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let data = self.buffer.as_ref();
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NetworkEndian::read_u16(&data[field::URGENT])
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}
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/// Return the length of the segment, in terms of sequence space.
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pub fn segment_len(&self) -> usize {
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let data = self.buffer.as_ref();
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let mut length = data.len() - self.header_len() as usize;
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if self.syn() { length += 1 }
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if self.fin() { length += 1 }
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length
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}
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/// Returns whether the selective acknowledgement SYN flag is set or not.
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pub fn selective_ack_permitted(&self) -> Result<bool> {
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let data = self.buffer.as_ref();
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let mut options = &data[field::OPTIONS(self.header_len())];
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while options.len() > 0 {
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let (next_options, option) = TcpOption::parse(options)?;
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match option {
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TcpOption::SackPermitted => {
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return Ok(true);
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},
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_ => {},
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}
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options = next_options;
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}
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Ok(false)
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}
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/// Return the selective acknowledgement ranges, if any. If there are none in the packet, an
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/// array of ``None`` values will be returned.
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///
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pub fn selective_ack_ranges<'s>(
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&'s self
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) -> Result<[Option<(u32, u32)>; 3]> {
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let data = self.buffer.as_ref();
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let mut options = &data[field::OPTIONS(self.header_len())];
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while options.len() > 0 {
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let (next_options, option) = TcpOption::parse(options)?;
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match option {
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TcpOption::SackRange(slice) => {
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return Ok(slice);
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},
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_ => {},
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}
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options = next_options;
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}
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Ok([None, None, None])
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}
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/// Validate the packet checksum.
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///
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/// # Panics
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/// This function panics unless `src_addr` and `dst_addr` belong to the same family,
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/// and that family is IPv4 or IPv6.
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///
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/// # Fuzzing
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/// This function always returns `true` when fuzzing.
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pub fn verify_checksum(&self, src_addr: &IpAddress, dst_addr: &IpAddress) -> bool {
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if cfg!(fuzzing) { return true }
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let data = self.buffer.as_ref();
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checksum::combine(&[
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checksum::pseudo_header(src_addr, dst_addr, IpProtocol::Tcp,
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data.len() as u32),
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checksum::data(data)
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]) == !0
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}
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}
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impl<'a, T: AsRef<[u8]> + ?Sized> Packet<&'a T> {
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/// Return a pointer to the options.
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#[inline]
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pub fn options(&self) -> &'a [u8] {
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let header_len = self.header_len();
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let data = self.buffer.as_ref();
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&data[field::OPTIONS(header_len)]
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}
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/// Return a pointer to the payload.
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#[inline]
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pub fn payload(&self) -> &'a [u8] {
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let header_len = self.header_len() as usize;
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let data = self.buffer.as_ref();
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&data[header_len..]
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}
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}
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impl<T: AsRef<[u8]> + AsMut<[u8]>> Packet<T> {
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/// Set the source port field.
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#[inline]
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pub fn set_src_port(&mut self, value: u16) {
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let data = self.buffer.as_mut();
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NetworkEndian::write_u16(&mut data[field::SRC_PORT], value)
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}
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/// Set the destination port field.
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#[inline]
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pub fn set_dst_port(&mut self, value: u16) {
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let data = self.buffer.as_mut();
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NetworkEndian::write_u16(&mut data[field::DST_PORT], value)
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}
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/// Set the sequence number field.
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#[inline]
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pub fn set_seq_number(&mut self, value: SeqNumber) {
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let data = self.buffer.as_mut();
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NetworkEndian::write_i32(&mut data[field::SEQ_NUM], value.0)
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}
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/// Set the acknowledgement number field.
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#[inline]
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pub fn set_ack_number(&mut self, value: SeqNumber) {
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let data = self.buffer.as_mut();
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NetworkEndian::write_i32(&mut data[field::ACK_NUM], value.0)
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}
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/// Clear the entire flags field.
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#[inline]
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pub fn clear_flags(&mut self) {
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let data = self.buffer.as_mut();
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let raw = NetworkEndian::read_u16(&data[field::FLAGS]);
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let raw = raw & !0x0fff;
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NetworkEndian::write_u16(&mut data[field::FLAGS], raw)
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}
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/// Set the FIN flag.
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#[inline]
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pub fn set_fin(&mut self, value: bool) {
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let data = self.buffer.as_mut();
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let raw = NetworkEndian::read_u16(&data[field::FLAGS]);
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let raw = if value { raw | field::FLG_FIN } else { raw & !field::FLG_FIN };
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NetworkEndian::write_u16(&mut data[field::FLAGS], raw)
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}
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/// Set the SYN flag.
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#[inline]
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pub fn set_syn(&mut self, value: bool) {
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let data = self.buffer.as_mut();
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let raw = NetworkEndian::read_u16(&data[field::FLAGS]);
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let raw = if value { raw | field::FLG_SYN } else { raw & !field::FLG_SYN };
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NetworkEndian::write_u16(&mut data[field::FLAGS], raw)
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}
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/// Set the RST flag.
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#[inline]
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pub fn set_rst(&mut self, value: bool) {
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let data = self.buffer.as_mut();
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let raw = NetworkEndian::read_u16(&data[field::FLAGS]);
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let raw = if value { raw | field::FLG_RST } else { raw & !field::FLG_RST };
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NetworkEndian::write_u16(&mut data[field::FLAGS], raw)
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}
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/// Set the PSH flag.
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#[inline]
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pub fn set_psh(&mut self, value: bool) {
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let data = self.buffer.as_mut();
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let raw = NetworkEndian::read_u16(&data[field::FLAGS]);
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let raw = if value { raw | field::FLG_PSH } else { raw & !field::FLG_PSH };
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NetworkEndian::write_u16(&mut data[field::FLAGS], raw)
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}
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/// Set the ACK flag.
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#[inline]
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pub fn set_ack(&mut self, value: bool) {
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let data = self.buffer.as_mut();
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let raw = NetworkEndian::read_u16(&data[field::FLAGS]);
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let raw = if value { raw | field::FLG_ACK } else { raw & !field::FLG_ACK };
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NetworkEndian::write_u16(&mut data[field::FLAGS], raw)
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}
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/// Set the URG flag.
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#[inline]
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pub fn set_urg(&mut self, value: bool) {
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let data = self.buffer.as_mut();
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let raw = NetworkEndian::read_u16(&data[field::FLAGS]);
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let raw = if value { raw | field::FLG_URG } else { raw & !field::FLG_URG };
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NetworkEndian::write_u16(&mut data[field::FLAGS], raw)
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}
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/// Set the ECE flag.
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#[inline]
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pub fn set_ece(&mut self, value: bool) {
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let data = self.buffer.as_mut();
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let raw = NetworkEndian::read_u16(&data[field::FLAGS]);
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let raw = if value { raw | field::FLG_ECE } else { raw & !field::FLG_ECE };
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NetworkEndian::write_u16(&mut data[field::FLAGS], raw)
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}
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/// Set the CWR flag.
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#[inline]
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pub fn set_cwr(&mut self, value: bool) {
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let data = self.buffer.as_mut();
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let raw = NetworkEndian::read_u16(&data[field::FLAGS]);
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let raw = if value { raw | field::FLG_CWR } else { raw & !field::FLG_CWR };
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NetworkEndian::write_u16(&mut data[field::FLAGS], raw)
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}
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|
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/// Set the NS flag.
|
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#[inline]
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pub fn set_ns(&mut self, value: bool) {
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let data = self.buffer.as_mut();
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let raw = NetworkEndian::read_u16(&data[field::FLAGS]);
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let raw = if value { raw | field::FLG_NS } else { raw & !field::FLG_NS };
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NetworkEndian::write_u16(&mut data[field::FLAGS], raw)
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}
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|
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/// Set the header length, in octets.
|
|
#[inline]
|
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pub fn set_header_len(&mut self, value: u8) {
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let data = self.buffer.as_mut();
|
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let raw = NetworkEndian::read_u16(&data[field::FLAGS]);
|
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let raw = (raw & !0xf000) | ((value as u16) / 4) << 12;
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|
NetworkEndian::write_u16(&mut data[field::FLAGS], raw)
|
|
}
|
|
|
|
/// Return the window size field.
|
|
#[inline]
|
|
pub fn set_window_len(&mut self, value: u16) {
|
|
let data = self.buffer.as_mut();
|
|
NetworkEndian::write_u16(&mut data[field::WIN_SIZE], value)
|
|
}
|
|
|
|
/// Set the checksum field.
|
|
#[inline]
|
|
pub fn set_checksum(&mut self, value: u16) {
|
|
let data = self.buffer.as_mut();
|
|
NetworkEndian::write_u16(&mut data[field::CHECKSUM], value)
|
|
}
|
|
|
|
/// Set the urgent pointer field.
|
|
#[inline]
|
|
pub fn set_urgent_at(&mut self, value: u16) {
|
|
let data = self.buffer.as_mut();
|
|
NetworkEndian::write_u16(&mut data[field::URGENT], value)
|
|
}
|
|
|
|
/// Compute and fill in the header checksum.
|
|
///
|
|
/// # Panics
|
|
/// This function panics unless `src_addr` and `dst_addr` belong to the same family,
|
|
/// and that family is IPv4 or IPv6.
|
|
pub fn fill_checksum(&mut self, src_addr: &IpAddress, dst_addr: &IpAddress) {
|
|
self.set_checksum(0);
|
|
let checksum = {
|
|
let data = self.buffer.as_ref();
|
|
!checksum::combine(&[
|
|
checksum::pseudo_header(src_addr, dst_addr, IpProtocol::Tcp,
|
|
data.len() as u32),
|
|
checksum::data(data)
|
|
])
|
|
};
|
|
self.set_checksum(checksum)
|
|
}
|
|
|
|
/// Return a pointer to the options.
|
|
#[inline]
|
|
pub fn options_mut(&mut self) -> &mut [u8] {
|
|
let header_len = self.header_len();
|
|
let data = self.buffer.as_mut();
|
|
&mut data[field::OPTIONS(header_len)]
|
|
}
|
|
|
|
/// Return a mutable pointer to the payload data.
|
|
#[inline]
|
|
pub fn payload_mut(&mut self) -> &mut [u8] {
|
|
let header_len = self.header_len() as usize;
|
|
let data = self.buffer.as_mut();
|
|
&mut data[header_len..]
|
|
}
|
|
}
|
|
|
|
impl<T: AsRef<[u8]>> AsRef<[u8]> for Packet<T> {
|
|
fn as_ref(&self) -> &[u8] {
|
|
self.buffer.as_ref()
|
|
}
|
|
}
|
|
|
|
/// A representation of a single TCP option.
|
|
#[derive(Debug, PartialEq, Eq, Clone, Copy)]
|
|
pub enum TcpOption<'a> {
|
|
EndOfList,
|
|
NoOperation,
|
|
MaxSegmentSize(u16),
|
|
WindowScale(u8),
|
|
SackPermitted,
|
|
SackRange([Option<(u32, u32)>; 3]),
|
|
Unknown { kind: u8, data: &'a [u8] }
|
|
}
|
|
|
|
impl<'a> TcpOption<'a> {
|
|
pub fn parse(buffer: &'a [u8]) -> Result<(&'a [u8], TcpOption<'a>)> {
|
|
let (length, option);
|
|
match *buffer.get(0).ok_or(Error::Truncated)? {
|
|
field::OPT_END => {
|
|
length = 1;
|
|
option = TcpOption::EndOfList;
|
|
}
|
|
field::OPT_NOP => {
|
|
length = 1;
|
|
option = TcpOption::NoOperation;
|
|
}
|
|
kind => {
|
|
length = *buffer.get(1).ok_or(Error::Truncated)? as usize;
|
|
let data = buffer.get(2..length).ok_or(Error::Truncated)?;
|
|
match (kind, length) {
|
|
(field::OPT_END, _) |
|
|
(field::OPT_NOP, _) =>
|
|
unreachable!(),
|
|
(field::OPT_MSS, 4) =>
|
|
option = TcpOption::MaxSegmentSize(NetworkEndian::read_u16(data)),
|
|
(field::OPT_MSS, _) =>
|
|
return Err(Error::Malformed),
|
|
(field::OPT_WS, 3) =>
|
|
option = TcpOption::WindowScale(data[0]),
|
|
(field::OPT_WS, _) =>
|
|
return Err(Error::Malformed),
|
|
(field::OPT_SACKPERM, 2) =>
|
|
option = TcpOption::SackPermitted,
|
|
(field::OPT_SACKPERM, _) =>
|
|
return Err(Error::Malformed),
|
|
(field::OPT_SACKRNG, n) => {
|
|
if n < 10 || (n-2) % 8 != 0 {
|
|
return Err(Error::Malformed)
|
|
}
|
|
if n > 26 {
|
|
// It's possible for a remote to send 4 SACK blocks, but extremely rare.
|
|
// Better to "lose" that 4th block and save the extra RAM and CPU
|
|
// cycles in the vastly more common case.
|
|
//
|
|
// RFC 2018: SACK option that specifies n blocks will have a length of
|
|
// 8*n+2 bytes, so the 40 bytes available for TCP options can specify a
|
|
// maximum of 4 blocks. It is expected that SACK will often be used in
|
|
// conjunction with the Timestamp option used for RTTM [...] thus a
|
|
// maximum of 3 SACK blocks will be allowed in this case.
|
|
net_debug!("sACK with >3 blocks, truncating to 3");
|
|
}
|
|
let mut sack_ranges: [Option<(u32, u32)>; 3] = [None; 3];
|
|
|
|
// RFC 2018: Each contiguous block of data queued at the data receiver is
|
|
// defined in the SACK option by two 32-bit unsigned integers in network
|
|
// byte order[...]
|
|
sack_ranges.iter_mut().enumerate().for_each(|(i, nmut)| {
|
|
let left = i * 8;
|
|
*nmut = if left < data.len() {
|
|
let mid = left + 4;
|
|
let right = mid + 4;
|
|
let range_left = NetworkEndian::read_u32(
|
|
&data[left..mid]);
|
|
let range_right = NetworkEndian::read_u32(
|
|
&data[mid..right]);
|
|
Some((range_left, range_right))
|
|
} else {
|
|
None
|
|
};
|
|
});
|
|
option = TcpOption::SackRange(sack_ranges);
|
|
},
|
|
(_, _) =>
|
|
option = TcpOption::Unknown { kind: kind, data: data }
|
|
}
|
|
}
|
|
}
|
|
Ok((&buffer[length..], option))
|
|
}
|
|
|
|
pub fn buffer_len(&self) -> usize {
|
|
match *self {
|
|
TcpOption::EndOfList => 1,
|
|
TcpOption::NoOperation => 1,
|
|
TcpOption::MaxSegmentSize(_) => 4,
|
|
TcpOption::WindowScale(_) => 3,
|
|
TcpOption::SackPermitted => 2,
|
|
TcpOption::SackRange(s) => s.iter().filter(|s| s.is_some()).count() * 8 + 2,
|
|
TcpOption::Unknown { data, .. } => 2 + data.len()
|
|
}
|
|
}
|
|
|
|
pub fn emit<'b>(&self, buffer: &'b mut [u8]) -> &'b mut [u8] {
|
|
let length;
|
|
match *self {
|
|
TcpOption::EndOfList => {
|
|
length = 1;
|
|
// There may be padding space which also should be initialized.
|
|
for p in buffer.iter_mut() {
|
|
*p = field::OPT_END;
|
|
}
|
|
}
|
|
TcpOption::NoOperation => {
|
|
length = 1;
|
|
buffer[0] = field::OPT_NOP;
|
|
}
|
|
_ => {
|
|
length = self.buffer_len();
|
|
buffer[1] = length as u8;
|
|
match self {
|
|
&TcpOption::EndOfList |
|
|
&TcpOption::NoOperation =>
|
|
unreachable!(),
|
|
&TcpOption::MaxSegmentSize(value) => {
|
|
buffer[0] = field::OPT_MSS;
|
|
NetworkEndian::write_u16(&mut buffer[2..], value)
|
|
}
|
|
&TcpOption::WindowScale(value) => {
|
|
buffer[0] = field::OPT_WS;
|
|
buffer[2] = value;
|
|
}
|
|
&TcpOption::SackPermitted => {
|
|
buffer[0] = field::OPT_SACKPERM;
|
|
}
|
|
&TcpOption::SackRange(slice) => {
|
|
buffer[0] = field::OPT_SACKRNG;
|
|
slice.iter().filter(|s| s.is_some()).enumerate().for_each(|(i, s)| {
|
|
let (first, second) = *s.as_ref().unwrap();
|
|
let pos = i * 8 + 2;
|
|
NetworkEndian::write_u32(&mut buffer[pos..], first);
|
|
NetworkEndian::write_u32(&mut buffer[pos+4..], second);
|
|
});
|
|
}
|
|
&TcpOption::Unknown { kind, data: provided } => {
|
|
buffer[0] = kind;
|
|
buffer[2..].copy_from_slice(provided)
|
|
}
|
|
}
|
|
}
|
|
}
|
|
&mut buffer[length..]
|
|
}
|
|
}
|
|
|
|
/// The possible control flags of a Transmission Control Protocol packet.
|
|
#[derive(Debug, PartialEq, Eq, Clone, Copy)]
|
|
pub enum Control {
|
|
None,
|
|
Psh,
|
|
Syn,
|
|
Fin,
|
|
Rst
|
|
}
|
|
|
|
impl Control {
|
|
/// Return the length of a control flag, in terms of sequence space.
|
|
pub fn len(self) -> usize {
|
|
match self {
|
|
Control::Syn | Control::Fin => 1,
|
|
_ => 0
|
|
}
|
|
}
|
|
|
|
/// Turn the PSH flag into no flag, and keep the rest as-is.
|
|
pub fn quash_psh(self) -> Control {
|
|
match self {
|
|
Control::Psh => Control::None,
|
|
_ => self
|
|
}
|
|
}
|
|
}
|
|
|
|
/// A high-level representation of a Transmission Control Protocol packet.
|
|
#[derive(Debug, PartialEq, Eq, Clone, Copy)]
|
|
pub struct Repr<'a> {
|
|
pub src_port: u16,
|
|
pub dst_port: u16,
|
|
pub control: Control,
|
|
pub seq_number: SeqNumber,
|
|
pub ack_number: Option<SeqNumber>,
|
|
pub window_len: u16,
|
|
pub window_scale: Option<u8>,
|
|
pub max_seg_size: Option<u16>,
|
|
pub sack_permitted: bool,
|
|
pub sack_ranges: [Option<(u32, u32)>; 3],
|
|
pub payload: &'a [u8]
|
|
}
|
|
|
|
impl<'a> Repr<'a> {
|
|
/// Parse a Transmission Control Protocol packet and return a high-level representation.
|
|
pub fn parse<T>(packet: &Packet<&'a T>, src_addr: &IpAddress, dst_addr: &IpAddress,
|
|
checksum_caps: &ChecksumCapabilities) -> Result<Repr<'a>>
|
|
where T: AsRef<[u8]> + ?Sized {
|
|
// Source and destination ports must be present.
|
|
if packet.src_port() == 0 { return Err(Error::Malformed) }
|
|
if packet.dst_port() == 0 { return Err(Error::Malformed) }
|
|
// Valid checksum is expected.
|
|
if checksum_caps.tcp.rx() && !packet.verify_checksum(src_addr, dst_addr) {
|
|
return Err(Error::Checksum)
|
|
}
|
|
|
|
let control =
|
|
match (packet.syn(), packet.fin(), packet.rst(), packet.psh()) {
|
|
(false, false, false, false) => Control::None,
|
|
(false, false, false, true) => Control::Psh,
|
|
(true, false, false, _) => Control::Syn,
|
|
(false, true, false, _) => Control::Fin,
|
|
(false, false, true , _) => Control::Rst,
|
|
_ => return Err(Error::Malformed)
|
|
};
|
|
let ack_number =
|
|
match packet.ack() {
|
|
true => Some(packet.ack_number()),
|
|
false => None
|
|
};
|
|
// The PSH flag is ignored.
|
|
// The URG flag and the urgent field is ignored. This behavior is standards-compliant,
|
|
// however, most deployed systems (e.g. Linux) are *not* standards-compliant, and would
|
|
// cut the byte at the urgent pointer from the stream.
|
|
|
|
let mut max_seg_size = None;
|
|
let mut window_scale = None;
|
|
let mut options = packet.options();
|
|
let mut sack_permitted = false;
|
|
let mut sack_ranges = [None, None, None];
|
|
while options.len() > 0 {
|
|
let (next_options, option) = TcpOption::parse(options)?;
|
|
match option {
|
|
TcpOption::EndOfList => break,
|
|
TcpOption::NoOperation => (),
|
|
TcpOption::MaxSegmentSize(value) =>
|
|
max_seg_size = Some(value),
|
|
TcpOption::WindowScale(value) => {
|
|
// RFC 1323: Thus, the shift count must be limited to 14 (which allows windows
|
|
// of 2**30 = 1 Gbyte). If a Window Scale option is received with a shift.cnt
|
|
// value exceeding 14, the TCP should log the error but use 14 instead of the
|
|
// specified value.
|
|
window_scale = if value > 14 {
|
|
net_debug!("{}:{}:{}:{}: parsed window scaling factor >14, setting to 14", src_addr, packet.src_port(), dst_addr, packet.dst_port());
|
|
Some(14)
|
|
} else {
|
|
Some(value)
|
|
};
|
|
},
|
|
TcpOption::SackPermitted =>
|
|
sack_permitted = true,
|
|
TcpOption::SackRange(slice) =>
|
|
sack_ranges = slice,
|
|
_ => (),
|
|
}
|
|
options = next_options;
|
|
}
|
|
|
|
Ok(Repr {
|
|
src_port: packet.src_port(),
|
|
dst_port: packet.dst_port(),
|
|
control: control,
|
|
seq_number: packet.seq_number(),
|
|
ack_number: ack_number,
|
|
window_len: packet.window_len(),
|
|
window_scale: window_scale,
|
|
max_seg_size: max_seg_size,
|
|
sack_permitted: sack_permitted,
|
|
sack_ranges: sack_ranges,
|
|
payload: packet.payload()
|
|
})
|
|
}
|
|
|
|
/// Return the length of a header that will be emitted from this high-level representation.
|
|
///
|
|
/// This should be used for buffer space calculations.
|
|
/// The TCP header length is a multiple of 4.
|
|
pub fn header_len(&self) -> usize {
|
|
let mut length = field::URGENT.end;
|
|
if self.max_seg_size.is_some() {
|
|
length += 4
|
|
}
|
|
if self.window_scale.is_some() {
|
|
length += 3
|
|
}
|
|
if self.sack_permitted {
|
|
length += 2;
|
|
}
|
|
let sack_range_len: usize = self.sack_ranges.iter().map(
|
|
|o| o.map(|_| 8).unwrap_or(0)
|
|
).sum();
|
|
if sack_range_len > 0 {
|
|
length += sack_range_len + 2;
|
|
}
|
|
if length % 4 != 0 {
|
|
length += 4 - length % 4;
|
|
}
|
|
length
|
|
}
|
|
|
|
/// Return the length of the header for the TCP protocol.
|
|
///
|
|
/// Per RFC 6691, this should be used for MSS calculations. It may be smaller than the buffer
|
|
/// space required to accomodate this packet's data.
|
|
pub fn mss_header_len(&self) -> usize {
|
|
field::URGENT.end
|
|
}
|
|
|
|
/// Return the length of a packet that will be emitted from this high-level representation.
|
|
pub fn buffer_len(&self) -> usize {
|
|
self.header_len() + self.payload.len()
|
|
}
|
|
|
|
/// Emit a high-level representation into a Transmission Control Protocol packet.
|
|
pub fn emit<T>(&self, packet: &mut Packet<&mut T>, src_addr: &IpAddress, dst_addr: &IpAddress,
|
|
checksum_caps: &ChecksumCapabilities)
|
|
where T: AsRef<[u8]> + AsMut<[u8]> + ?Sized {
|
|
packet.set_src_port(self.src_port);
|
|
packet.set_dst_port(self.dst_port);
|
|
packet.set_seq_number(self.seq_number);
|
|
packet.set_ack_number(self.ack_number.unwrap_or(SeqNumber(0)));
|
|
packet.set_window_len(self.window_len);
|
|
packet.set_header_len(self.header_len() as u8);
|
|
packet.clear_flags();
|
|
match self.control {
|
|
Control::None => (),
|
|
Control::Psh => packet.set_psh(true),
|
|
Control::Syn => packet.set_syn(true),
|
|
Control::Fin => packet.set_fin(true),
|
|
Control::Rst => packet.set_rst(true)
|
|
}
|
|
packet.set_ack(self.ack_number.is_some());
|
|
{
|
|
let mut options = packet.options_mut();
|
|
if let Some(value) = self.max_seg_size {
|
|
let tmp = options; options = TcpOption::MaxSegmentSize(value).emit(tmp);
|
|
}
|
|
if let Some(value) = self.window_scale {
|
|
let tmp = options; options = TcpOption::WindowScale(value).emit(tmp);
|
|
}
|
|
if self.sack_permitted {
|
|
let tmp = options; options = TcpOption::SackPermitted.emit(tmp);
|
|
} else if self.ack_number.is_some() && self.sack_ranges.iter().any(|s| s.is_some()) {
|
|
let tmp = options; options = TcpOption::SackRange(self.sack_ranges).emit(tmp);
|
|
}
|
|
|
|
if options.len() > 0 {
|
|
TcpOption::EndOfList.emit(options);
|
|
}
|
|
}
|
|
packet.set_urgent_at(0);
|
|
packet.payload_mut()[..self.payload.len()].copy_from_slice(self.payload);
|
|
|
|
if checksum_caps.tcp.tx() {
|
|
packet.fill_checksum(src_addr, dst_addr)
|
|
} else {
|
|
// make sure we get a consistently zeroed checksum,
|
|
// since implementations might rely on it
|
|
packet.set_checksum(0);
|
|
}
|
|
}
|
|
|
|
/// Return the length of the segment, in terms of sequence space.
|
|
pub fn segment_len(&self) -> usize {
|
|
self.payload.len() + self.control.len()
|
|
}
|
|
|
|
/// Return whether the segment has no flags set (except PSH) and no data.
|
|
pub fn is_empty(&self) -> bool {
|
|
match self.control {
|
|
_ if self.payload.len() != 0 => false,
|
|
Control::Syn | Control::Fin | Control::Rst => false,
|
|
Control::None | Control::Psh => true
|
|
}
|
|
}
|
|
}
|
|
|
|
impl<'a, T: AsRef<[u8]> + ?Sized> fmt::Display for Packet<&'a T> {
|
|
fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
|
|
// Cannot use Repr::parse because we don't have the IP addresses.
|
|
write!(f, "TCP src={} dst={}",
|
|
self.src_port(), self.dst_port())?;
|
|
if self.syn() { write!(f, " syn")? }
|
|
if self.fin() { write!(f, " fin")? }
|
|
if self.rst() { write!(f, " rst")? }
|
|
if self.psh() { write!(f, " psh")? }
|
|
if self.ece() { write!(f, " ece")? }
|
|
if self.cwr() { write!(f, " cwr")? }
|
|
if self.ns() { write!(f, " ns" )? }
|
|
write!(f, " seq={}", self.seq_number())?;
|
|
if self.ack() {
|
|
write!(f, " ack={}", self.ack_number())?;
|
|
}
|
|
write!(f, " win={}", self.window_len())?;
|
|
if self.urg() {
|
|
write!(f, " urg={}", self.urgent_at())?;
|
|
}
|
|
write!(f, " len={}", self.payload().len())?;
|
|
|
|
let mut options = self.options();
|
|
while options.len() > 0 {
|
|
let (next_options, option) =
|
|
match TcpOption::parse(options) {
|
|
Ok(res) => res,
|
|
Err(err) => return write!(f, " ({})", err)
|
|
};
|
|
match option {
|
|
TcpOption::EndOfList => break,
|
|
TcpOption::NoOperation => (),
|
|
TcpOption::MaxSegmentSize(value) =>
|
|
write!(f, " mss={}", value)?,
|
|
TcpOption::WindowScale(value) =>
|
|
write!(f, " ws={}", value)?,
|
|
TcpOption::SackPermitted =>
|
|
write!(f, " sACK")?,
|
|
TcpOption::SackRange(slice) =>
|
|
write!(f, " sACKr{:?}", slice)?, // debug print conveniently includes the []s
|
|
TcpOption::Unknown { kind, .. } =>
|
|
write!(f, " opt({})", kind)?,
|
|
}
|
|
options = next_options;
|
|
}
|
|
Ok(())
|
|
}
|
|
}
|
|
|
|
impl<'a> fmt::Display for Repr<'a> {
|
|
fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
|
|
write!(f, "TCP src={} dst={}",
|
|
self.src_port, self.dst_port)?;
|
|
match self.control {
|
|
Control::Syn => write!(f, " syn")?,
|
|
Control::Fin => write!(f, " fin")?,
|
|
Control::Rst => write!(f, " rst")?,
|
|
Control::Psh => write!(f, " psh")?,
|
|
Control::None => ()
|
|
}
|
|
write!(f, " seq={}", self.seq_number)?;
|
|
if let Some(ack_number) = self.ack_number {
|
|
write!(f, " ack={}", ack_number)?;
|
|
}
|
|
write!(f, " win={}", self.window_len)?;
|
|
write!(f, " len={}", self.payload.len())?;
|
|
if let Some(max_seg_size) = self.max_seg_size {
|
|
write!(f, " mss={}", max_seg_size)?;
|
|
}
|
|
Ok(())
|
|
}
|
|
}
|
|
|
|
use crate::wire::pretty_print::{PrettyPrint, PrettyIndent};
|
|
|
|
impl<T: AsRef<[u8]>> PrettyPrint for Packet<T> {
|
|
fn pretty_print(buffer: &dyn AsRef<[u8]>, f: &mut fmt::Formatter,
|
|
indent: &mut PrettyIndent) -> fmt::Result {
|
|
match Packet::new_checked(buffer) {
|
|
Err(err) => write!(f, "{}({})", indent, err),
|
|
Ok(packet) => write!(f, "{}{}", indent, packet)
|
|
}
|
|
}
|
|
}
|
|
|
|
#[cfg(test)]
|
|
mod test {
|
|
#[cfg(feature = "proto-ipv4")]
|
|
use crate::wire::Ipv4Address;
|
|
use super::*;
|
|
|
|
#[cfg(feature = "proto-ipv4")]
|
|
const SRC_ADDR: Ipv4Address = Ipv4Address([192, 168, 1, 1]);
|
|
#[cfg(feature = "proto-ipv4")]
|
|
const DST_ADDR: Ipv4Address = Ipv4Address([192, 168, 1, 2]);
|
|
|
|
#[cfg(feature = "proto-ipv4")]
|
|
static PACKET_BYTES: [u8; 28] =
|
|
[0xbf, 0x00, 0x00, 0x50,
|
|
0x01, 0x23, 0x45, 0x67,
|
|
0x89, 0xab, 0xcd, 0xef,
|
|
0x60, 0x35, 0x01, 0x23,
|
|
0x01, 0xb6, 0x02, 0x01,
|
|
0x03, 0x03, 0x0c, 0x01,
|
|
0xaa, 0x00, 0x00, 0xff];
|
|
|
|
#[cfg(feature = "proto-ipv4")]
|
|
static OPTION_BYTES: [u8; 4] =
|
|
[0x03, 0x03, 0x0c, 0x01];
|
|
|
|
#[cfg(feature = "proto-ipv4")]
|
|
static PAYLOAD_BYTES: [u8; 4] =
|
|
[0xaa, 0x00, 0x00, 0xff];
|
|
|
|
#[test]
|
|
#[cfg(feature = "proto-ipv4")]
|
|
fn test_deconstruct() {
|
|
let packet = Packet::new_unchecked(&PACKET_BYTES[..]);
|
|
assert_eq!(packet.src_port(), 48896);
|
|
assert_eq!(packet.dst_port(), 80);
|
|
assert_eq!(packet.seq_number(), SeqNumber(0x01234567));
|
|
assert_eq!(packet.ack_number(), SeqNumber(0x89abcdefu32 as i32));
|
|
assert_eq!(packet.header_len(), 24);
|
|
assert_eq!(packet.fin(), true);
|
|
assert_eq!(packet.syn(), false);
|
|
assert_eq!(packet.rst(), true);
|
|
assert_eq!(packet.psh(), false);
|
|
assert_eq!(packet.ack(), true);
|
|
assert_eq!(packet.urg(), true);
|
|
assert_eq!(packet.window_len(), 0x0123);
|
|
assert_eq!(packet.urgent_at(), 0x0201);
|
|
assert_eq!(packet.checksum(), 0x01b6);
|
|
assert_eq!(packet.options(), &OPTION_BYTES[..]);
|
|
assert_eq!(packet.payload(), &PAYLOAD_BYTES[..]);
|
|
assert_eq!(packet.verify_checksum(&SRC_ADDR.into(), &DST_ADDR.into()), true);
|
|
}
|
|
|
|
#[test]
|
|
#[cfg(feature = "proto-ipv4")]
|
|
fn test_construct() {
|
|
let mut bytes = vec![0xa5; PACKET_BYTES.len()];
|
|
let mut packet = Packet::new_unchecked(&mut bytes);
|
|
packet.set_src_port(48896);
|
|
packet.set_dst_port(80);
|
|
packet.set_seq_number(SeqNumber(0x01234567));
|
|
packet.set_ack_number(SeqNumber(0x89abcdefu32 as i32));
|
|
packet.set_header_len(24);
|
|
packet.clear_flags();
|
|
packet.set_fin(true);
|
|
packet.set_syn(false);
|
|
packet.set_rst(true);
|
|
packet.set_psh(false);
|
|
packet.set_ack(true);
|
|
packet.set_urg(true);
|
|
packet.set_window_len(0x0123);
|
|
packet.set_urgent_at(0x0201);
|
|
packet.set_checksum(0xEEEE);
|
|
packet.options_mut().copy_from_slice(&OPTION_BYTES[..]);
|
|
packet.payload_mut().copy_from_slice(&PAYLOAD_BYTES[..]);
|
|
packet.fill_checksum(&SRC_ADDR.into(), &DST_ADDR.into());
|
|
assert_eq!(&packet.into_inner()[..], &PACKET_BYTES[..]);
|
|
}
|
|
|
|
#[test]
|
|
#[cfg(feature = "proto-ipv4")]
|
|
fn test_truncated() {
|
|
let packet = Packet::new_unchecked(&PACKET_BYTES[..23]);
|
|
assert_eq!(packet.check_len(), Err(Error::Truncated));
|
|
}
|
|
|
|
#[test]
|
|
fn test_impossible_len() {
|
|
let mut bytes = vec![0; 20];
|
|
let mut packet = Packet::new_unchecked(&mut bytes);
|
|
packet.set_header_len(10);
|
|
assert_eq!(packet.check_len(), Err(Error::Malformed));
|
|
}
|
|
|
|
#[cfg(feature = "proto-ipv4")]
|
|
static SYN_PACKET_BYTES: [u8; 24] =
|
|
[0xbf, 0x00, 0x00, 0x50,
|
|
0x01, 0x23, 0x45, 0x67,
|
|
0x00, 0x00, 0x00, 0x00,
|
|
0x50, 0x02, 0x01, 0x23,
|
|
0x7a, 0x8d, 0x00, 0x00,
|
|
0xaa, 0x00, 0x00, 0xff];
|
|
|
|
#[cfg(feature = "proto-ipv4")]
|
|
fn packet_repr() -> Repr<'static> {
|
|
Repr {
|
|
src_port: 48896,
|
|
dst_port: 80,
|
|
seq_number: SeqNumber(0x01234567),
|
|
ack_number: None,
|
|
window_len: 0x0123,
|
|
window_scale: None,
|
|
control: Control::Syn,
|
|
max_seg_size: None,
|
|
sack_permitted: false,
|
|
sack_ranges: [None, None, None],
|
|
payload: &PAYLOAD_BYTES
|
|
}
|
|
}
|
|
|
|
#[test]
|
|
#[cfg(feature = "proto-ipv4")]
|
|
fn test_parse() {
|
|
let packet = Packet::new_unchecked(&SYN_PACKET_BYTES[..]);
|
|
let repr = Repr::parse(&packet, &SRC_ADDR.into(), &DST_ADDR.into(), &ChecksumCapabilities::default()).unwrap();
|
|
assert_eq!(repr, packet_repr());
|
|
}
|
|
|
|
#[test]
|
|
#[cfg(feature = "proto-ipv4")]
|
|
fn test_emit() {
|
|
let repr = packet_repr();
|
|
let mut bytes = vec![0xa5; repr.buffer_len()];
|
|
let mut packet = Packet::new_unchecked(&mut bytes);
|
|
repr.emit(&mut packet, &SRC_ADDR.into(), &DST_ADDR.into(), &ChecksumCapabilities::default());
|
|
assert_eq!(&packet.into_inner()[..], &SYN_PACKET_BYTES[..]);
|
|
}
|
|
|
|
#[test]
|
|
#[cfg(feature = "proto-ipv4")]
|
|
fn test_header_len_multiple_of_4() {
|
|
let mut repr = packet_repr();
|
|
repr.window_scale = Some(0); // This TCP Option needs 3 bytes.
|
|
assert_eq!(repr.header_len() % 4, 0); // Should e.g. be 28 instead of 27.
|
|
}
|
|
|
|
macro_rules! assert_option_parses {
|
|
($opt:expr, $data:expr) => ({
|
|
assert_eq!(TcpOption::parse($data), Ok((&[][..], $opt)));
|
|
let buffer = &mut [0; 40][..$opt.buffer_len()];
|
|
assert_eq!($opt.emit(buffer), &mut []);
|
|
assert_eq!(&*buffer, $data);
|
|
})
|
|
}
|
|
|
|
#[test]
|
|
fn test_tcp_options() {
|
|
assert_option_parses!(TcpOption::EndOfList,
|
|
&[0x00]);
|
|
assert_option_parses!(TcpOption::NoOperation,
|
|
&[0x01]);
|
|
assert_option_parses!(TcpOption::MaxSegmentSize(1500),
|
|
&[0x02, 0x04, 0x05, 0xdc]);
|
|
assert_option_parses!(TcpOption::WindowScale(12),
|
|
&[0x03, 0x03, 0x0c]);
|
|
assert_option_parses!(TcpOption::SackPermitted,
|
|
&[0x4, 0x02]);
|
|
assert_option_parses!(TcpOption::SackRange([Some((500, 1500)), None, None]),
|
|
&[0x05, 0x0a,
|
|
0x00, 0x00, 0x01, 0xf4, 0x00, 0x00, 0x05, 0xdc]);
|
|
assert_option_parses!(TcpOption::SackRange([Some((875, 1225)), Some((1500, 2500)), None]),
|
|
&[0x05, 0x12,
|
|
0x00, 0x00, 0x03, 0x6b, 0x00, 0x00, 0x04, 0xc9,
|
|
0x00, 0x00, 0x05, 0xdc, 0x00, 0x00, 0x09, 0xc4]);
|
|
assert_option_parses!(TcpOption::SackRange([Some((875000, 1225000)),
|
|
Some((1500000, 2500000)),
|
|
Some((876543210, 876654320))]),
|
|
&[0x05, 0x1a,
|
|
0x00, 0x0d, 0x59, 0xf8, 0x00, 0x12, 0xb1, 0x28,
|
|
0x00, 0x16, 0xe3, 0x60, 0x00, 0x26, 0x25, 0xa0,
|
|
0x34, 0x3e, 0xfc, 0xea, 0x34, 0x40, 0xae, 0xf0]);
|
|
assert_option_parses!(TcpOption::Unknown { kind: 12, data: &[1, 2, 3][..] },
|
|
&[0x0c, 0x05, 0x01, 0x02, 0x03])
|
|
}
|
|
|
|
#[test]
|
|
fn test_malformed_tcp_options() {
|
|
assert_eq!(TcpOption::parse(&[]),
|
|
Err(Error::Truncated));
|
|
assert_eq!(TcpOption::parse(&[0xc]),
|
|
Err(Error::Truncated));
|
|
assert_eq!(TcpOption::parse(&[0xc, 0x05, 0x01, 0x02]),
|
|
Err(Error::Truncated));
|
|
assert_eq!(TcpOption::parse(&[0xc, 0x01]),
|
|
Err(Error::Truncated));
|
|
assert_eq!(TcpOption::parse(&[0x2, 0x02]),
|
|
Err(Error::Malformed));
|
|
assert_eq!(TcpOption::parse(&[0x3, 0x02]),
|
|
Err(Error::Malformed));
|
|
}
|
|
}
|