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use std::net::Ipv4Addr;
pub struct Ipv4Packet<'p> {
/// The computed size of the IP packet
header_length: usize,
/// The total length of the IP packet when all fragments are combined
total_length: u16,
more_fragments: bool,
fragment_offset: usize,
next_header: IpNextHeader,
pub src: Ipv4Addr,
pub dst: Ipv4Addr,
payload: &'p [u8],
}
impl<'p> Ipv4Packet<'p> {
pub fn new(buffer: &'p [u8]) -> Self {
let ihl = buffer[0].to_be() & 0b0000_1111;
let header_length = ihl as usize * 4;
let total_length = u16::from_be_bytes([buffer[2], buffer[3]]);
// Fragmentation
let more_fragments = (buffer[6] & 0b0010_0000) > 0;
let fragment_offset = u16::from_be_bytes([buffer[6] & 0b0001_1111, buffer[7]]);
// Fragments are in units of 8 bytes
let true_frag_offset = fragment_offset as usize * 8;
let next_header = IpNextHeader::new(buffer[9]);
let src = Ipv4Addr::new(buffer[12], buffer[13], buffer[14], buffer[15]);
let dst = Ipv4Addr::new(buffer[16], buffer[17], buffer[18], buffer[19]);
Self {
header_length,
total_length,
more_fragments,
fragment_offset: true_frag_offset,
next_header,
src,
dst,
payload: &buffer[header_length..],
}
}
pub fn get_source(&self) -> Ipv4Addr {
self.src
}
pub fn get_destination(&self) -> Ipv4Addr {
self.dst
}
pub fn has_more_fragments(&self) -> bool {
self.more_fragments
}
pub fn get_fragment_offset(&self) -> usize {
self.fragment_offset
}
pub fn get_next_header(&self) -> IpNextHeader {
self.next_header
}
pub fn get_payload(&self) -> &[u8] {
&self.payload
}
pub fn get_packet_len(&self) -> usize {
self.total_length as usize
}
pub fn get_payload_len(&self) -> usize {
// An IPv4 header is always 20 bytes long
self.total_length as usize - 20
}
}
#[derive(Copy, Clone, Debug, PartialEq)]
pub enum IpNextHeader {
Icmp,
Igmp,
Tcp,
Udp,
Unknown(u8),
}
impl IpNextHeader {
pub fn new(n: u8) -> Self {
match n {
1 => Self::Icmp,
2 => Self::Igmp,
6 => Self::Tcp,
17 => Self::Udp,
n => Self::Unknown(n),
}
}
}
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