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use crate::*;
/// Allows iterating over the options after a TCP header.
#[derive(Clone, Eq, PartialEq)]
pub struct TcpOptionsIterator<'a> {
pub(crate) options: &'a [u8],
}
impl<'a> TcpOptionsIterator<'a> {
/// Creates an options iterator from a slice containing encoded tcp options.
pub fn from_slice(options: &'a [u8]) -> TcpOptionsIterator<'a> {
TcpOptionsIterator { options }
}
/// Returns the non processed part of the options slice.
pub fn rest(&self) -> &'a [u8] {
self.options
}
}
impl<'a> Iterator for TcpOptionsIterator<'a> {
type Item = Result<TcpOptionElement, TcpOptionReadError>;
fn next(&mut self) -> Option<Self::Item> {
use crate::TcpOptionElement::*;
use crate::TcpOptionReadError::*;
let expect_specific_size =
|expected_size: u8, slice: &[u8]| -> Result<(), TcpOptionReadError> {
let id = slice[0];
if slice.len() < expected_size as usize {
Err(UnexpectedEndOfSlice {
option_id: id,
expected_len: expected_size,
actual_len: slice.len(),
})
} else if slice[1] != expected_size {
Err(UnexpectedSize {
option_id: slice[0],
size: slice[1],
})
} else {
Ok(())
}
};
if self.options.is_empty() {
None
} else {
//first determine the result
use tcp_option::*;
let result = match self.options[0] {
//end
KIND_END => None,
KIND_NOOP => {
self.options = &self.options[1..];
Some(Ok(Noop))
}
KIND_MAXIMUM_SEGMENT_SIZE => {
match expect_specific_size(LEN_MAXIMUM_SEGMENT_SIZE, self.options) {
Err(value) => Some(Err(value)),
_ => {
// SAFETY:
// Safe as the slice size is checked beforehand to be at
// least of size LEN_MAXIMUM_SEGMENT_SIZE (4).
let value =
unsafe { get_unchecked_be_u16(self.options.as_ptr().add(2)) };
self.options = &self.options[4..];
Some(Ok(MaximumSegmentSize(value)))
}
}
}
KIND_WINDOW_SCALE => match expect_specific_size(LEN_WINDOW_SCALE, self.options) {
Err(value) => Some(Err(value)),
_ => {
let value = self.options[2];
self.options = &self.options[3..];
Some(Ok(WindowScale(value)))
}
},
KIND_SELECTIVE_ACK_PERMITTED => {
match expect_specific_size(LEN_SELECTIVE_ACK_PERMITTED, self.options) {
Err(value) => Some(Err(value)),
_ => {
self.options = &self.options[2..];
Some(Ok(SelectiveAcknowledgementPermitted))
}
}
}
KIND_SELECTIVE_ACK => {
//check that the length field can be read
if self.options.len() < 2 {
Some(Err(UnexpectedEndOfSlice {
option_id: self.options[0],
expected_len: 2,
actual_len: self.options.len(),
}))
} else {
//check that the length is an allowed one for this option
let len = self.options[1];
if len != 10 && len != 18 && len != 26 && len != 34 {
Some(Err(UnexpectedSize {
option_id: self.options[0],
size: len,
}))
} else if self.options.len() < (len as usize) {
Some(Err(UnexpectedEndOfSlice {
option_id: self.options[0],
expected_len: len,
actual_len: self.options.len(),
}))
} else {
let mut acks: [Option<(u32, u32)>; 3] = [None; 3];
// SAFETY:
// This is safe as above the len is checked
// to be at least 10 and the slice len is
// checked to be at least len bytes.
let first = unsafe {
(
get_unchecked_be_u32(self.options.as_ptr().add(2)),
get_unchecked_be_u32(self.options.as_ptr().add(6)),
)
};
for (i, item) in acks.iter_mut().enumerate().take(3) {
let offset = 2 + 8 + (i * 8);
// SAFETY:
// len can only be 10, 18, 26 or 34
// therefore if the offset is smaller then the
// len, then at least 8 bytes can be read.
unsafe {
if offset < (len as usize) {
*item = Some((
get_unchecked_be_u32(self.options.as_ptr().add(offset)),
get_unchecked_be_u32(
self.options.as_ptr().add(offset + 4),
),
));
}
}
}
//iterate the options
self.options = &self.options[len as usize..];
Some(Ok(SelectiveAcknowledgement(first, acks)))
}
}
}
KIND_TIMESTAMP => {
match expect_specific_size(LEN_TIMESTAMP, self.options) {
Err(value) => Some(Err(value)),
_ => unsafe {
let t = Timestamp(
// SAFETY:
// Safe as the len first gets checked to be equal
// LEN_TIMESTAMP (10).
get_unchecked_be_u32(self.options.as_ptr().add(2)),
get_unchecked_be_u32(self.options.as_ptr().add(6)),
);
self.options = &self.options[10..];
Some(Ok(t))
},
}
}
//unknown id
_ => Some(Err(UnknownId(self.options[0]))),
};
//in case the result was an error or the end move the slice to an end position
match result {
None | Some(Err(_)) => {
let len = self.options.len();
self.options = &self.options[len..len];
}
_ => {}
}
//finally return the result
result
}
}
}
impl<'a> core::fmt::Debug for TcpOptionsIterator<'a> {
fn fmt(&self, fmt: &mut core::fmt::Formatter) -> Result<(), core::fmt::Error> {
let mut list = fmt.debug_list();
// create a copy and iterate over all elements
for it in self.clone() {
match it {
Ok(e) => {
list.entry(&e);
}
Err(e) => {
list.entry(&Result::<(), TcpOptionReadError>::Err(e.clone()));
}
}
}
list.finish()
}
}
#[cfg(test)]
mod test {
use crate::{tcp_option::*, *};
use alloc::format;
#[test]
fn debug() {
use tcp_option::*;
#[rustfmt::skip]
assert_eq!(
"[MaximumSegmentSize(0), WindowScale(0)]",
format!(
"{:?}",
TcpOptionsIterator::from_slice(&[
KIND_MAXIMUM_SEGMENT_SIZE, 4, 0, 0,
KIND_WINDOW_SCALE, 3, 0,
KIND_END,
])
)
);
#[rustfmt::skip]
assert_eq!(
"[MaximumSegmentSize(0), Err(UnexpectedSize { option_id: 3, size: 0 })]",
format!(
"{:?}",
TcpOptionsIterator::from_slice(&[
KIND_MAXIMUM_SEGMENT_SIZE, 4, 0, 0,
KIND_WINDOW_SCALE, 0, 0, 0,
])
)
);
}
#[test]
fn clone_eq() {
use tcp_option::*;
let it = TcpOptionsIterator::from_slice(&[KIND_END]);
assert_eq!(it, it.clone());
}
#[test]
fn from_slice_and_rest() {
let buffer = [KIND_NOOP, KIND_NOOP, KIND_MAXIMUM_SEGMENT_SIZE, 4];
let it = TcpOptionsIterator::from_slice(&buffer);
assert_eq!(it.rest(), &buffer[..]);
}
#[test]
#[rustfmt::skip]
fn next() {
use crate::TcpOptionElement::*;
// ok test
{
fn expect_elements(buffer: &[u8], expected: &[TcpOptionElement]) {
// options iterator via from_slice()
let mut it = TcpOptionsIterator::from_slice(buffer);
for element in expected.iter() {
assert_eq!(element, &it.next().unwrap().unwrap());
}
//expect no more elements
assert_eq!(None, it.next());
assert_eq!(0, it.rest().len());
}
// nop & max segment size
#[rustfmt::skip]
expect_elements(&[
KIND_NOOP,
KIND_NOOP,
KIND_MAXIMUM_SEGMENT_SIZE, 4,
0, 1,
KIND_WINDOW_SCALE, 3, 2,
KIND_SELECTIVE_ACK_PERMITTED, 2,
KIND_SELECTIVE_ACK, 10,
0, 0, 0, 10,
0, 0, 0, 11,
KIND_SELECTIVE_ACK, 18,
0, 0, 0, 12,
0, 0, 0, 13,
0, 0, 0, 14,
0, 0, 0, 15,
KIND_SELECTIVE_ACK, 26,
0, 0, 0, 16,
0, 0, 0, 17,
0, 0, 0, 18,
0, 0, 0, 19,
0, 0, 0, 20,
0, 0, 0, 21,
KIND_SELECTIVE_ACK, 34,
0, 0, 0, 22,
0, 0, 0, 23,
0, 0, 0, 24,
0, 0, 0, 25,
0, 0, 0, 26,
0, 0, 0, 27,
0, 0, 0, 28,
0, 0, 0, 29,
KIND_TIMESTAMP, 10,
0, 0, 0, 30,
0, 0, 0, 31,
KIND_END, 0, 0, 0, 0
],
&[
Noop,
Noop,
MaximumSegmentSize(1),
WindowScale(2),
SelectiveAcknowledgementPermitted,
SelectiveAcknowledgement((10,11), [None, None, None]),
SelectiveAcknowledgement((12,13), [Some((14,15)), None, None]),
SelectiveAcknowledgement((16,17), [Some((18,19)), Some((20,21)), None]),
SelectiveAcknowledgement((22,23), [Some((24,25)), Some((26,27)), Some((28,29))]),
Timestamp(30,31)
]
);
}
// unknown id
{
let data = [255, 2, 0, 0, 0,
0, 0, 0, 0, 0, //10
0, 0, 0, 0, 0,
0, 0, 0, 0, 0, //20
0, 0, 0, 0, 0,
0, 0, 0, 0, 0, //30
0, 0, 0, 0];
let mut it = TcpOptionsIterator::from_slice(&data);
assert_eq!(Some(Err(TcpOptionReadError::UnknownId(255))), it.next());
//expect the iterator slice to be moved to the end
assert_eq!(0, it.rest().len());
assert_eq!(None, it.next());
assert_eq!(0, it.rest().len());
}
// unexpected end of slice
{
fn expect_unexpected_eos(slice: &[u8]) {
for i in 1..slice.len()-1 {
let mut it = TcpOptionsIterator::from_slice(&slice[..i]);
assert_eq!(
Some(
Err(
TcpOptionReadError::UnexpectedEndOfSlice{
option_id: slice[0],
expected_len: match slice[0] {
KIND_MAXIMUM_SEGMENT_SIZE => 4,
KIND_WINDOW_SCALE => 3,
KIND_SELECTIVE_ACK_PERMITTED => 2,
KIND_SELECTIVE_ACK => if i < 2 {
// the inial check only checks if there
// is enough data to read the length field
2
} else {
slice[1]
},
KIND_TIMESTAMP => 10,
_ => panic!("not part of the tests"),
},
actual_len: i
}
)
),
it.next()
);
//expect the iterator slice to be moved to the end
assert_eq!(0, it.rest().len());
assert_eq!(None, it.next());
}
}
expect_unexpected_eos(&[KIND_MAXIMUM_SEGMENT_SIZE, 4, 0, 0]);
expect_unexpected_eos(&[KIND_WINDOW_SCALE, 3, 0]);
expect_unexpected_eos(&[KIND_MAXIMUM_SEGMENT_SIZE, 4, 0, 0]);
expect_unexpected_eos(&[KIND_SELECTIVE_ACK_PERMITTED, 2]);
expect_unexpected_eos(&[KIND_SELECTIVE_ACK, 10, 0, 0, 0,
0, 0, 0, 0, 0]);
expect_unexpected_eos(&[KIND_SELECTIVE_ACK, 18, 0, 0, 0,
0, 0, 0, 0, 0,
0, 0, 0, 0, 0,
0, 0, 0]);
expect_unexpected_eos(&[KIND_SELECTIVE_ACK, 26, 0, 0, 0,
0, 0, 0, 0, 0,
0, 0, 0, 0, 0,
0, 0, 0, 0, 0,
0, 0, 0, 0, 0,
0]);
expect_unexpected_eos(&[KIND_SELECTIVE_ACK, 34, 0, 0, 0,
0, 0, 0, 0, 0, //10
0, 0, 0, 0, 0,
0, 0, 0, 0, 0, //20
0, 0, 0, 0, 0,
0, 0, 0, 0, 0, //30
0, 0, 0, 0]);
expect_unexpected_eos(&[KIND_TIMESTAMP, 10, 0, 0, 0,
0, 0, 0, 0, 0]);
}
// unexpected option size error
{
fn expect_unexpected_size(id: u8, size: u8) {
let data = [
id, size, 0, 0, 0, 0, 0, 0, 0, 0, //10
0, 0, 0, 0, 0, 0, 0, 0, 0, 0, //20
0, 0, 0, 0, 0, 0, 0, 0, 0, 0, //30
0, 0, 0, 0,
];
let mut it = TcpOptionsIterator::from_slice(&data);
assert_eq!(
Some(Err(TcpOptionReadError::UnexpectedSize {
option_id: data[0],
size: data[1]
})),
it.next()
);
//expect the iterator slice to be moved to the end
assert_eq!(0, it.rest().len());
assert_eq!(None, it.next());
assert_eq!(0, it.rest().len());
}
expect_unexpected_size(KIND_MAXIMUM_SEGMENT_SIZE, 3);
expect_unexpected_size(KIND_MAXIMUM_SEGMENT_SIZE, 5);
expect_unexpected_size(KIND_WINDOW_SCALE, 2);
expect_unexpected_size(KIND_WINDOW_SCALE, 4);
expect_unexpected_size(KIND_MAXIMUM_SEGMENT_SIZE, 3);
expect_unexpected_size(KIND_MAXIMUM_SEGMENT_SIZE, 5);
expect_unexpected_size(KIND_SELECTIVE_ACK_PERMITTED, 1);
expect_unexpected_size(KIND_SELECTIVE_ACK_PERMITTED, 3);
expect_unexpected_size(KIND_SELECTIVE_ACK, 9);
expect_unexpected_size(KIND_SELECTIVE_ACK, 11);
expect_unexpected_size(KIND_SELECTIVE_ACK, 17);
expect_unexpected_size(KIND_SELECTIVE_ACK, 19);
expect_unexpected_size(KIND_SELECTIVE_ACK, 25);
expect_unexpected_size(KIND_SELECTIVE_ACK, 27);
expect_unexpected_size(KIND_SELECTIVE_ACK, 33);
expect_unexpected_size(KIND_SELECTIVE_ACK, 35);
expect_unexpected_size(KIND_TIMESTAMP, 9);
expect_unexpected_size(KIND_TIMESTAMP, 11);
}
}
}