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use crate::{err::*, *};
/// Slice containing the UDP headers & payload.
#[derive(Clone, Debug, Eq, PartialEq)]
pub struct UdpSlice<'a> {
slice: &'a [u8],
}
impl<'a> UdpSlice<'a> {
/// Decode length from UDP header and restrict slice to the length
/// of the header including the payload.
///
/// Note that this method fall backs to the length of the slice
/// in the case the length field in the UDP header is set to zero.
pub fn from_slice(slice: &'a [u8]) -> Result<UdpSlice<'a>, LenError> {
// slice header
let header = UdpHeaderSlice::from_slice(slice)?;
// validate the length of the slice
let len: usize = header.length().into();
if slice.len() < len {
return Err(LenError {
required_len: len,
len: slice.len(),
len_source: LenSource::Slice,
layer: Layer::UdpPayload,
layer_start_offset: 0,
});
}
// fallback to the slice length in case length is set to 0
if len == 0 {
Ok(UdpSlice { slice })
} else {
// validate the length
if len < UdpHeader::LEN {
// TODO: Should this replaced with a custom error?
Err(LenError {
required_len: UdpHeader::LEN,
len,
len_source: LenSource::UdpHeaderLen,
layer: Layer::UdpHeader,
layer_start_offset: 0,
})
} else {
Ok(UdpSlice {
// SAFETY: Safe as slice.len() was validated before to
// be at least as big as "len".
slice: unsafe { core::slice::from_raw_parts(slice.as_ptr(), len) },
})
}
}
}
/// Try decoding length from UDP header and restrict slice to the length
/// of the header including the payload if possible. If not the slice length
/// is used as a fallback value.
///
/// Note that this method fall also backs to the length of the slice
/// in the case the length field in the UDP header is set to zero or smaller
/// then the minimum header length.
pub fn from_slice_lax(slice: &'a [u8]) -> Result<UdpSlice<'a>, LenError> {
// slice header
let header = UdpHeaderSlice::from_slice(slice)?;
// validate the length of the slice and fallback to the slice
// length if the slice is smaller then expected or zero.
let len: usize = header.length().into();
if slice.len() < len || len < UdpHeader::LEN {
Ok(UdpSlice { slice })
} else {
Ok(UdpSlice {
// SAFETY: Safe as slice.len() was validated before to
// be at least as big as "len".
slice: unsafe { core::slice::from_raw_parts(slice.as_ptr(), len) },
})
}
}
/// Return the slice containing the UDP header & payload.
#[inline]
pub fn slice(&self) -> &'a [u8] {
self.slice
}
/// Return the slice containing the UDP header.
#[inline]
pub fn header_slice(&self) -> &'a [u8] {
unsafe {
// SAFETY: Safe as the slice length was verified
// to be at least UdpHeader::LEN by "from_slice".
core::slice::from_raw_parts(self.slice.as_ptr(), UdpHeader::LEN)
}
}
/// Returns the slice containing the UDP payload.
#[inline]
pub fn payload(&self) -> &'a [u8] {
unsafe {
// SAFETY: Safe as the slice length was verified
// to be at least UdpHeader::LEN by "from_slice".
core::slice::from_raw_parts(
self.slice.as_ptr().add(UdpHeader::LEN),
self.slice.len() - UdpHeader::LEN,
)
}
}
/// Value that was used to determine the length of the payload.
#[inline]
pub fn payload_len_source(&self) -> LenSource {
if usize::from(self.length()) == self.slice.len() {
LenSource::UdpHeaderLen
} else {
LenSource::Slice
}
}
/// Reads the "udp source port" in the UDP header.
#[inline]
pub fn source_port(&self) -> u16 {
// SAFETY:
// Safe as the contructor checks that the slice has
// at least the length of UdpHeader::LEN (8).
unsafe { get_unchecked_be_u16(self.slice.as_ptr()) }
}
/// Reads the "udp destination port" in the UDP header.
#[inline]
pub fn destination_port(&self) -> u16 {
// SAFETY:
// Safe as the contructor checks that the slice has
// at least the length of UdpHeader::LEN (8).
unsafe { get_unchecked_be_u16(self.slice.as_ptr().add(2)) }
}
/// Reads the "length" field in the UDP header.
#[inline]
pub fn length(&self) -> u16 {
// SAFETY:
// Safe as the contructor checks that the slice has
// at least the length of UdpHeader::LEN (8).
unsafe { get_unchecked_be_u16(self.slice.as_ptr().add(4)) }
}
/// Reads the "checksum" from the slice.
#[inline]
pub fn checksum(&self) -> u16 {
// SAFETY:
// Safe as the contructor checks that the slice has
// at least the length of UdpHeader::LEN (8).
unsafe { get_unchecked_be_u16(self.slice.as_ptr().add(6)) }
}
/// Length of the UDP header (equal to [`crate::UdpHeader::LEN`]).
#[inline]
pub const fn header_len(&self) -> usize {
UdpHeader::LEN
}
/// Length of the UDP header in an [`u16`] (equal to [`crate::UdpHeader::LEN_U16`]).
#[inline]
pub const fn header_len_u16(&self) -> u16 {
UdpHeader::LEN_U16
}
/// Decode all the fields of the UDP header and copy the results
/// to a UdpHeader struct.
#[inline]
pub fn to_header(&self) -> UdpHeader {
UdpHeader {
source_port: self.source_port(),
destination_port: self.destination_port(),
length: self.length(),
checksum: self.checksum(),
}
}
}
#[cfg(test)]
mod test {
use super::*;
use crate::test_gens::*;
use alloc::{format, vec::Vec};
use proptest::prelude::*;
proptest! {
#[test]
fn debug_clone_eq(
udp_base in udp_any()
) {
let payload: [u8;4] = [1,2,3,4];
let mut data = Vec::with_capacity(
udp_base.header_len() +
payload.len()
);
let mut udp = udp_base.clone();
udp.length = (UdpHeader::LEN + payload.len()) as u16;
data.extend_from_slice(&udp.to_bytes());
data.extend_from_slice(&payload);
// decode packet
let slice = UdpSlice::from_slice(&data).unwrap();
// check debug output
prop_assert_eq!(
format!("{:?}", slice),
format!(
"UdpSlice {{ slice: {:?} }}",
&data[..]
)
);
prop_assert_eq!(slice.clone(), slice);
}
}
proptest! {
#[test]
fn getters(
udp_base in udp_any()
) {
let udp = {
let mut udp = udp_base.clone();
udp.length = UdpHeader::LEN as u16;
udp
};
let data = {
let mut data = Vec::with_capacity(
udp.header_len()
);
data.extend_from_slice(&udp.to_bytes());
data
};
// normal decode
{
let slice = UdpSlice::from_slice(&data).unwrap();
assert_eq!(slice.slice(), &data);
assert_eq!(slice.header_slice(), &data);
assert_eq!(slice.payload(), &[]);
assert_eq!(slice.source_port(), udp.source_port);
assert_eq!(slice.destination_port(), udp.destination_port);
assert_eq!(slice.length(), udp.length);
assert_eq!(slice.checksum(), udp.checksum);
assert_eq!(slice.to_header(), udp);
}
}
}
proptest! {
#[test]
fn from_slice(
udp_base in udp_any()
) {
let payload: [u8;4] = [1,2,3,4];
let udp = {
let mut udp = udp_base.clone();
udp.length = (UdpHeader::LEN + payload.len()) as u16;
udp
};
let data = {
let mut data = Vec::with_capacity(
udp.header_len() +
payload.len()
);
data.extend_from_slice(&udp.to_bytes());
data.extend_from_slice(&payload);
data
};
// normal decode
{
let slice = UdpSlice::from_slice(&data).unwrap();
assert_eq!(udp, slice.to_header());
assert_eq!(payload, slice.payload());
}
// decode a payload smaller then the given slice
{
let mut mod_data = data.clone();
let reduced_len = (UdpHeader::LEN + payload.len() - 1) as u16;
// inject the reduced length
{
let rl_be = reduced_len.to_be_bytes();
mod_data[4] = rl_be[0];
mod_data[5] = rl_be[1];
}
let slice = UdpSlice::from_slice(&mod_data).unwrap();
assert_eq!(
slice.to_header(),
{
let mut expected = slice.to_header();
expected.length = reduced_len;
expected
}
);
assert_eq!(&payload[..payload.len() - 1], slice.payload());
}
// if length is zero the length given by the slice should be used
{
// inject zero as length
let mut mod_data = data.clone();
mod_data[4] = 0;
mod_data[5] = 0;
let slice = UdpSlice::from_slice(&mod_data).unwrap();
assert_eq!(slice.source_port(), udp_base.source_port);
assert_eq!(slice.destination_port(), udp_base.destination_port);
assert_eq!(slice.checksum(), udp_base.checksum);
assert_eq!(slice.length(), 0);
assert_eq!(&payload, slice.payload());
}
// too little data to even decode the header
for len in 0..UdpHeader::LEN {
assert_eq!(
UdpSlice::from_slice(&data[..len]).unwrap_err(),
LenError {
required_len: UdpHeader::LEN,
len,
len_source: LenSource::Slice,
layer: Layer::UdpHeader,
layer_start_offset: 0,
}
);
}
// slice length smaller then the length described in the header
assert_eq!(
UdpSlice::from_slice(&data[..data.len() - 1]).unwrap_err(),
LenError {
required_len: data.len(),
len: data.len() - 1,
len_source: LenSource::Slice,
layer: Layer::UdpPayload,
layer_start_offset: 0,
}
);
// length in header smaller than the header itself
{
let mut mod_data = data.clone();
// inject the reduced length
{
let len_be = ((UdpHeader::LEN - 1) as u16).to_be_bytes();
mod_data[4] = len_be[0];
mod_data[5] = len_be[1];
}
assert_eq!(
UdpSlice::from_slice(&mod_data).unwrap_err(),
LenError {
required_len: UdpHeader::LEN,
len: UdpHeader::LEN - 1,
len_source: LenSource::UdpHeaderLen,
layer: Layer::UdpHeader,
layer_start_offset: 0
}
);
}
}
}
proptest! {
#[test]
fn from_slice_lax(
udp_base in udp_any()
) {
let payload: [u8;4] = [1,2,3,4];
let udp = {
let mut udp = udp_base.clone();
udp.length = (UdpHeader::LEN + payload.len()) as u16;
udp
};
let data = {
let mut data = Vec::with_capacity(
udp.header_len() +
payload.len()
);
data.extend_from_slice(&udp.to_bytes());
data.extend_from_slice(&payload);
data
};
// normal decode
{
let slice = UdpSlice::from_slice_lax(&data).unwrap();
assert_eq!(udp, slice.to_header());
assert_eq!(payload, slice.payload());
assert_eq!(slice.payload_len_source(), LenSource::UdpHeaderLen);
}
// decode a payload smaller then the given slice
{
let mut mod_data = data.clone();
let reduced_len = (UdpHeader::LEN + payload.len() - 1) as u16;
// inject the reduced length
{
let rl_be = reduced_len.to_be_bytes();
mod_data[4] = rl_be[0];
mod_data[5] = rl_be[1];
}
let slice = UdpSlice::from_slice_lax(&mod_data).unwrap();
assert_eq!(
slice.to_header(),
{
let mut expected = slice.to_header();
expected.length = reduced_len;
expected
}
);
assert_eq!(&payload[..payload.len() - 1], slice.payload());
assert_eq!(slice.payload_len_source(), LenSource::UdpHeaderLen);
}
// if length is zero the length given by the slice should be used
for len in 0..UdpHeader::LEN_U16{
// inject zero as length
let mut mod_data = data.clone();
mod_data[4] = len.to_be_bytes()[0];
mod_data[5] = len.to_be_bytes()[1];
let slice = UdpSlice::from_slice_lax(&mod_data).unwrap();
assert_eq!(slice.source_port(), udp_base.source_port);
assert_eq!(slice.destination_port(), udp_base.destination_port);
assert_eq!(slice.checksum(), udp_base.checksum);
assert_eq!(slice.length(), len);
assert_eq!(&payload, slice.payload());
assert_eq!(slice.payload_len_source(), LenSource::Slice);
}
// too little data to even decode the header
for len in 0..UdpHeader::LEN {
assert_eq!(
UdpSlice::from_slice_lax(&data[..len]).unwrap_err(),
LenError {
required_len: UdpHeader::LEN,
len,
len_source: LenSource::Slice,
layer: Layer::UdpHeader,
layer_start_offset: 0,
}
);
}
// slice length smaller then the length described in the header
{
let slice = UdpSlice::from_slice_lax(&data[..data.len() - 1]).unwrap();
assert_eq!(udp, slice.to_header());
assert_eq!(&payload[..payload.len() - 1], slice.payload());
assert_eq!(slice.payload_len_source(), LenSource::Slice);
}
}
}
}