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use crate::{err::*, *};
/// Slice containing an Ethernet 2 headers & payload.
#[derive(Clone, Eq, PartialEq)]
pub struct Ethernet2Slice<'a> {
fcs_len: usize,
slice: &'a [u8],
}
impl<'a> Ethernet2Slice<'a> {
/// Try creating a [`Ethernet2Slice`] from a slice containing the
/// Ethernet 2 header & payload WITHOUT an FCS (frame check sequence)
/// at the end.
pub fn from_slice_without_fcs(slice: &'a [u8]) -> Result<Ethernet2Slice<'a>, LenError> {
// check length
if slice.len() < Ethernet2Header::LEN {
return Err(LenError {
required_len: Ethernet2Header::LEN,
len: slice.len(),
len_source: LenSource::Slice,
layer: Layer::Ethernet2Header,
layer_start_offset: 0,
});
}
Ok(Ethernet2Slice { fcs_len: 0, slice })
}
/// Try creating a [`Ethernet2Slice`] from a slice containing the
/// Ethernet 2 header & payload with a CRC 32 bit FCS (frame
/// check sequence) at the end.
///
/// In case you are not sure if your ethernet2 frame has a FCS or not
/// use [`Ethernet2Slice::from_slice_without_fcs`] instead and rely on the
/// lower layers (e.g. IP) to determine the correct payload length.
pub fn from_slice_with_crc32_fcs(slice: &'a [u8]) -> Result<Ethernet2Slice<'a>, LenError> {
// check length
let fcs_len = 4;
if slice.len() < Ethernet2Header::LEN + fcs_len {
return Err(LenError {
required_len: Ethernet2Header::LEN + 4,
len: slice.len(),
len_source: LenSource::Slice,
layer: Layer::Ethernet2Header,
layer_start_offset: 0,
});
}
Ok(Ethernet2Slice { fcs_len, slice })
}
/// Returns the slice containing the ethernet 2 header
/// payload and FCS if present.
#[inline]
pub fn slice(&self) -> &'a [u8] {
self.slice
}
/// Read the destination MAC address
#[inline]
pub fn destination(&self) -> [u8; 6] {
// SAFETY:
// Safe as the contructor checks that the slice has
// at least the length of Ethernet2Header::LEN (14).
unsafe { get_unchecked_6_byte_array(self.slice.as_ptr()) }
}
/// Read the source MAC address
#[inline]
pub fn source(&self) -> [u8; 6] {
// SAFETY:
// Safe as the contructor checks that the slice has
// at least the length of Ethernet2Header::LEN (14).
unsafe { get_unchecked_6_byte_array(self.slice.as_ptr().add(6)) }
}
/// Read the ether_type field of the header indicating the protocol
/// after the header.
#[inline]
pub fn ether_type(&self) -> EtherType {
// SAFETY:
// Safe as the contructor checks that the slice has
// at least the length of Ethernet2Header::LEN (14).
EtherType(unsafe { get_unchecked_be_u16(self.slice.as_ptr().add(12)) })
}
/// Returns the frame check sequence if present.
#[inline]
pub fn fcs(&self) -> Option<[u8; 4]> {
if self.fcs_len == 4 {
// SAFETY: Safe as the slice length was verified
// to be at least Ethernet2Header::LEN + fcs_len by
// "from_slice_without_fcs" & "from_slice_with_crc32_fcs".
Some(unsafe {
[
*self.slice.as_ptr().add(self.slice.len() - 4),
*self.slice.as_ptr().add(self.slice.len() - 3),
*self.slice.as_ptr().add(self.slice.len() - 2),
*self.slice.as_ptr().add(self.slice.len() - 1),
]
})
} else {
None
}
}
/// Decode all the fields and copy the results to a [`Ethernet2Header`] struct
pub fn to_header(&self) -> Ethernet2Header {
Ethernet2Header {
source: self.source(),
destination: self.destination(),
ether_type: self.ether_type(),
}
}
/// Slice containing the Ethernet 2 header.
pub fn header_slice(&self) -> &[u8] {
unsafe {
// SAFETY:
// Safe as the contructor checks that the slice has
// at least the length of Ethernet2Header::LEN (14).
core::slice::from_raw_parts(self.slice.as_ptr(), Ethernet2Header::LEN)
}
}
/// Returns the slice containing the Ethernet II payload & ether type
/// identifying it's content type.
#[inline]
pub fn payload(&self) -> EtherPayloadSlice<'a> {
EtherPayloadSlice {
ether_type: self.ether_type(),
payload: self.payload_slice(),
}
}
/// Returns the slice containing the Ethernet II payload.
#[inline]
pub fn payload_slice(&self) -> &'a [u8] {
unsafe {
// SAFETY: Safe as the slice length was verified
// to be at least Ethernet2Header::LEN + fcs_len by
// "from_slice_without_fcs" & "from_slice_with_crc32_fcs".
core::slice::from_raw_parts(
self.slice.as_ptr().add(Ethernet2Header::LEN),
self.slice.len() - Ethernet2Header::LEN - self.fcs_len,
)
}
}
/// Length of the Ethernet 2 header in bytes (equal to
/// [`crate::Ethernet2Header::LEN`]).
#[inline]
pub const fn header_len(&self) -> usize {
Ethernet2Header::LEN
}
}
impl<'a> core::fmt::Debug for Ethernet2Slice<'a> {
fn fmt(&self, f: &mut core::fmt::Formatter<'_>) -> core::fmt::Result {
f.debug_struct("Ethernet2Slice")
.field("header", &self.to_header())
.field("payload", &self.payload())
.field("fcs", &self.fcs())
.finish()
}
}
#[cfg(test)]
mod test {
use super::*;
use crate::test_gens::*;
use alloc::{format, vec::Vec};
use proptest::prelude::*;
proptest! {
#[test]
fn debug_clone_eq(
eth in ethernet_2_any(),
has_fcs in any::<bool>()
) {
let payload: [u8;8] = [1,2,3,4,5,6,7,8];
let mut data = Vec::with_capacity(
eth.header_len() +
payload.len()
);
data.extend_from_slice(ð.to_bytes());
data.extend_from_slice(&payload);
// decode packet
let slice = if has_fcs {
Ethernet2Slice::from_slice_with_crc32_fcs(&data).unwrap()
} else {
Ethernet2Slice::from_slice_without_fcs(&data).unwrap()
};
// check debug output
prop_assert_eq!(
format!("{:?}", slice),
format!(
"Ethernet2Slice {{ header: {:?}, payload: {:?}, fcs: {:?} }}",
slice.to_header(),
slice.payload(),
slice.fcs()
)
);
prop_assert_eq!(slice.clone(), slice);
}
}
proptest! {
#[test]
fn getters(eth in ethernet_2_any()) {
let payload: [u8;8] = [1,2,3,4,5,6,7,8];
let mut data = Vec::with_capacity(
eth.header_len() +
payload.len()
);
data.extend_from_slice(ð.to_bytes());
data.extend_from_slice(&payload);
// without fcs
{
let slice = Ethernet2Slice::from_slice_without_fcs(&data).unwrap();
assert_eq!(eth.destination, slice.destination());
assert_eq!(eth.source, slice.source());
assert_eq!(eth.ether_type, slice.ether_type());
assert_eq!(&payload, slice.payload_slice());
assert_eq!(
EtherPayloadSlice{
payload: &payload,
ether_type: eth.ether_type,
},
slice.payload()
);
assert_eq!(None, slice.fcs());
assert_eq!(eth, slice.to_header());
assert_eq!(&data, slice.slice());
assert_eq!(&data[..Ethernet2Header::LEN], slice.header_slice());
}
// with fcs
{
let slice = Ethernet2Slice::from_slice_with_crc32_fcs(&data).unwrap();
assert_eq!(eth.destination, slice.destination());
assert_eq!(eth.source, slice.source());
assert_eq!(eth.ether_type, slice.ether_type());
assert_eq!(&payload[..payload.len() - 4], slice.payload_slice());
assert_eq!(
EtherPayloadSlice{
payload: &payload[..payload.len() - 4],
ether_type: eth.ether_type,
},
slice.payload()
);
assert_eq!(Some([5, 6, 7, 8]), slice.fcs());
assert_eq!(eth, slice.to_header());
assert_eq!(&data, slice.slice());
assert_eq!(&data[..Ethernet2Header::LEN], slice.header_slice());
}
}
}
proptest! {
#[test]
fn from_slice_without_fcs(eth in ethernet_2_any()) {
let payload: [u8;10] = [1,2,3,4,5,6,7,8,9,10];
let data = {
let mut data = Vec::with_capacity(
eth.header_len() +
payload.len()
);
data.extend_from_slice(ð.to_bytes());
data.extend_from_slice(&payload);
data
};
// normal decode
{
let slice = Ethernet2Slice::from_slice_without_fcs(&data).unwrap();
assert_eq!(slice.to_header(), eth);
assert_eq!(slice.payload_slice(), &payload);
assert_eq!(slice.fcs(), None);
}
// decode without payload
{
let slice = Ethernet2Slice::from_slice_without_fcs(&data[..Ethernet2Header::LEN]).unwrap();
assert_eq!(slice.to_header(), eth);
assert_eq!(slice.payload_slice(), &[]);
assert_eq!(slice.fcs(), None);
}
// length error
for len in 0..Ethernet2Header::LEN {
assert_eq!(
Ethernet2Slice::from_slice_without_fcs(&data[..len]).unwrap_err(),
LenError{
required_len: Ethernet2Header::LEN,
len,
len_source: LenSource::Slice,
layer: Layer::Ethernet2Header,
layer_start_offset: 0
}
);
}
}
}
proptest! {
#[test]
fn from_slice_with_crc32_fcs(
eth in ethernet_2_any()
) {
let payload: [u8;10] = [1,2,3,4,5,6,7,8,9,10];
let fcs: [u8;4] = [11,12,13,14];
let data = {
let mut data = Vec::with_capacity(
eth.header_len() +
payload.len()
);
data.extend_from_slice(ð.to_bytes());
data.extend_from_slice(&payload);
data.extend_from_slice(&fcs);
data
};
// normal decode
{
let slice = Ethernet2Slice::from_slice_with_crc32_fcs(&data).unwrap();
assert_eq!(slice.to_header(), eth);
assert_eq!(slice.payload_slice(), &payload);
assert_eq!(slice.fcs(), Some(fcs));
}
// decode without payload
{
let slice = Ethernet2Slice::from_slice_with_crc32_fcs(&data[..Ethernet2Header::LEN + 4]).unwrap();
assert_eq!(slice.to_header(), eth);
assert_eq!(slice.payload_slice(), &[]);
assert_eq!(slice.fcs(), Some([1,2,3,4]));
}
// length error
for len in 0..Ethernet2Header::LEN + 4 {
assert_eq!(
Ethernet2Slice::from_slice_with_crc32_fcs(&data[..len]).unwrap_err(),
LenError{
required_len: Ethernet2Header::LEN + 4,
len,
len_source: LenSource::Slice,
layer: Layer::Ethernet2Header,
layer_start_offset: 0
}
);
}
}
}
}