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use core::mem;
use byteorder::BigEndian;
use zerocopy::byteorder::U16;
use zerocopy::LayoutVerified;
use zerocopy::{AsBytes, FromBytes};
pub const VERSION_IP4: u8 = 4;
pub const VERSION_IP6: u8 = 6;
#[repr(packed)]
#[derive(Copy, Clone, FromBytes, AsBytes)]
pub struct IPv4Header {
_f_space1: [u8; 2],
pub f_total_len: U16<BigEndian>,
_f_space2: [u8; 8],
pub f_source: [u8; 4],
pub f_destination: [u8; 4],
}
#[repr(packed)]
#[derive(Copy, Clone, FromBytes, AsBytes)]
pub struct IPv6Header {
_f_space1: [u8; 4],
pub f_len: U16<BigEndian>,
_f_space2: [u8; 2],
pub f_source: [u8; 16],
pub f_destination: [u8; 16],
}
#[inline(always)]
pub fn inner_length(packet: &[u8]) -> Option<usize> {
match packet.get(0)? >> 4 {
VERSION_IP4 => {
let (header, _): (LayoutVerified<&[u8], IPv4Header>, _) =
LayoutVerified::new_from_prefix(packet)?;
Some(header.f_total_len.get() as usize)
}
VERSION_IP6 => {
// check length and cast to IPv6 header
let (header, _): (LayoutVerified<&[u8], IPv6Header>, _) =
LayoutVerified::new_from_prefix(packet)?;
Some(header.f_len.get() as usize + mem::size_of::<IPv6Header>())
}
_ => None,
}
}
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