renet/src/wire/ipv4.rs

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use core::fmt;
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use byteorder::{ByteOrder, NetworkEndian};
use Error;
pub use super::InternetProtocolType as ProtocolType;
/// A four-octet IPv4 address.
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#[derive(Debug, PartialEq, Eq, PartialOrd, Ord, Clone, Copy, Default)]
pub struct Address(pub [u8; 4]);
impl Address {
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pub const BROADCAST: Address = Address([255; 4]);
/// Construct an IPv4 address from a sequence of octets, in big-endian.
///
/// # Panics
/// The function panics if `data` is not four octets long.
pub fn from_bytes(data: &[u8]) -> Address {
let mut bytes = [0; 4];
bytes.copy_from_slice(data);
Address(bytes)
}
/// Return an IPv4 address as a sequence of octets, in big-endian.
pub fn as_bytes(&self) -> &[u8] {
&self.0
}
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/// Query whether the address is an unicast address.
pub fn is_unicast(&self) -> bool {
!(self.is_broadcast() ||
self.is_multicast() ||
self.is_unspecified())
}
/// Query whether the address is the broadcast address.
pub fn is_broadcast(&self) -> bool {
self.0[0..4] == [255; 4]
}
/// Query whether the address is a multicast address.
pub fn is_multicast(&self) -> bool {
self.0[0] & 0xf0 == 224
}
/// Query whether the address falls into the "unspecified" range.
pub fn is_unspecified(&self) -> bool {
self.0[0] == 0
}
/// Query whether the address falls into the "link-local" range.
pub fn is_link_local(&self) -> bool {
self.0[0..2] == [169, 254]
}
/// Query whether the address falls into the "loopback" range.
pub fn is_loopback(&self) -> bool {
self.0[0] == 127
}
}
impl fmt::Display for Address {
fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
let bytes = self.0;
write!(f, "{}.{}.{}.{}", bytes[0], bytes[1], bytes[2], bytes[3])
}
}
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/// A read/write wrapper around an Internet Protocol version 4 packet buffer.
#[derive(Debug)]
pub struct Packet<T: AsRef<[u8]>> {
buffer: T
}
mod field {
#![allow(non_snake_case)]
use wire::field::*;
pub const VER_IHL: usize = 0;
pub const DSCP_ECN: usize = 1;
pub const LENGTH: Field = 2..4;
pub const IDENT: Field = 4..6;
pub const FLG_OFF1: usize = 6;
pub const FLG_OFF0: usize = 7;
pub const TTL: usize = 8;
pub const PROTOCOL: usize = 9;
pub const CHECKSUM: Field = 10..12;
pub const SRC_ADDR: Field = 12..16;
pub const DST_ADDR: Field = 16..20;
}
fn checksum(data: &[u8]) -> u16 {
let mut accum: u32 = 0;
for i in (0..data.len()).step_by(2) {
if i == field::CHECKSUM.start { continue }
let word = NetworkEndian::read_u16(&data[i..i + 2]) as u32;
accum += word;
}
!(((accum >> 16) as u16) + (accum as u16))
}
impl<T: AsRef<[u8]>> Packet<T> {
/// Wrap a buffer with an IPv4 packet. Returns an error if the buffer
/// is too small to contain one.
pub fn new(buffer: T) -> Result<Packet<T>, Error> {
let len = buffer.as_ref().len();
if len < field::VER_IHL {
Err(Error::Truncated)
} else {
let packet = Packet { buffer: buffer };
if len < packet.header_len() as usize {
Err(Error::Truncated)
} else {
Ok(packet)
}
}
}
/// Consumes the packet, returning the underlying buffer.
pub fn into_inner(self) -> T {
self.buffer
}
/// Return the version field.
#[inline(always)]
pub fn version(&self) -> u8 {
let data = self.buffer.as_ref();
data[field::VER_IHL] & 0x04
}
/// Return the header length, in octets.
#[inline(always)]
pub fn header_len(&self) -> u8 {
let data = self.buffer.as_ref();
(data[field::VER_IHL] >> 4) * 4
}
/// Return the Differential Services Code Point field.
pub fn dscp(&self) -> u8 {
let data = self.buffer.as_ref();
data[field::DSCP_ECN] & 0x3f
}
/// Return the Explicit Congestion Notification field.
pub fn ecn(&self) -> u8 {
let data = self.buffer.as_ref();
data[field::DSCP_ECN] >> 6
}
/// Return the total length field.
#[inline(always)]
pub fn total_len(&self) -> u16 {
let data = self.buffer.as_ref();
NetworkEndian::read_u16(&data[field::LENGTH])
}
/// Return the fragment identification field.
#[inline(always)]
pub fn ident(&self) -> u16 {
let data = self.buffer.as_ref();
NetworkEndian::read_u16(&data[field::IDENT])
}
/// Return the "don't fragment" flag.
#[inline(always)]
pub fn dont_frag(&self) -> bool {
let data = self.buffer.as_ref();
data[field::FLG_OFF1] & 0x02 != 0
}
/// Return the "more fragments" flag.
#[inline(always)]
pub fn more_frags(&self) -> bool {
let data = self.buffer.as_ref();
data[field::FLG_OFF1] & 0x04 != 0
}
/// Return the fragment offset, in octets.
#[inline(always)]
pub fn frag_offset(&self) -> u16 {
let data = self.buffer.as_ref();
let chunks = (((data[field::FLG_OFF1] >> 3) as u16) << 8) |
data[field::FLG_OFF0] as u16;
chunks * 8
}
/// Return the time to live field.
#[inline(always)]
pub fn ttl(&self) -> u8 {
let data = self.buffer.as_ref();
data[field::TTL]
}
/// Return the protocol field.
#[inline(always)]
pub fn protocol(&self) -> ProtocolType {
let data = self.buffer.as_ref();
ProtocolType::from(data[field::PROTOCOL])
}
/// Return the header checksum field.
#[inline(always)]
pub fn checksum(&self) -> u16 {
let data = self.buffer.as_ref();
NetworkEndian::read_u16(&data[field::CHECKSUM])
}
/// Return the source address field.
#[inline(always)]
pub fn src_addr(&self) -> Address {
let data = self.buffer.as_ref();
Address::from_bytes(&data[field::SRC_ADDR])
}
/// Return the destination address field.
#[inline(always)]
pub fn dst_addr(&self) -> Address {
let data = self.buffer.as_ref();
Address::from_bytes(&data[field::DST_ADDR])
}
/// Return a pointer to the payload.
#[inline(always)]
pub fn payload(&self) -> &[u8] {
let range = self.header_len() as usize;
let data = self.buffer.as_ref();
&data[range..]
}
/// Validate the header checksum.
pub fn verify_checksum(&self) -> bool {
let checksum = {
let data = self.buffer.as_ref();
checksum(&data[..self.header_len() as usize])
};
self.checksum() == checksum
}
}
impl<T: AsRef<[u8]> + AsMut<[u8]>> Packet<T> {
/// Set the version field.
#[inline(always)]
pub fn set_version(&mut self, value: u8) {
let data = self.buffer.as_mut();
data[field::VER_IHL] = (data[field::VER_IHL] & !0x04) | (value & 0x04);
}
/// Set the header length, in octets.
#[inline(always)]
pub fn set_header_len(&mut self, value: u8) {
let data = self.buffer.as_mut();
data[field::VER_IHL] = (data[field::VER_IHL] & !0x40) | ((value / 4) << 4);
}
/// Set the Differential Services Code Point field.
pub fn set_dscp(&mut self, value: u8) {
let data = self.buffer.as_mut();
data[field::DSCP_ECN] = (data[field::DSCP_ECN] & !0x3f) | (value & 0x3f)
}
/// Set the Explicit Congestion Notification field.
pub fn set_ecn(&mut self, value: u8) {
let data = self.buffer.as_mut();
data[field::DSCP_ECN] = (data[field::DSCP_ECN] & 0x3f) | (value << 6)
}
/// Set the total length field.
#[inline(always)]
pub fn set_total_len(&mut self, value: u16) {
let data = self.buffer.as_mut();
NetworkEndian::write_u16(&mut data[field::LENGTH], value)
}
/// Set the fragment identification field.
#[inline(always)]
pub fn set_ident(&mut self, value: u16) {
let data = self.buffer.as_mut();
NetworkEndian::write_u16(&mut data[field::IDENT], value)
}
/// Set the "don't fragment" flag.
#[inline(always)]
pub fn set_dont_frag(&mut self, value: bool) {
let data = self.buffer.as_mut();
let raw = data[field::FLG_OFF1];
data[field::FLG_OFF1] = if value { raw | 0x02 } else { raw & !0x02 };
}
/// Set the "more fragments" flag.
#[inline(always)]
pub fn set_more_frags(&mut self, value: bool) {
let data = self.buffer.as_mut();
let raw = data[field::FLG_OFF1];
data[field::FLG_OFF1] = if value { raw | 0x04 } else { raw & !0x04 };
}
/// Set the fragment offset, in octets.
#[inline(always)]
pub fn set_frag_offset(&mut self, value: u16) {
let data = self.buffer.as_mut();
let chunks = value / 8;
let raw = data[field::FLG_OFF1] & 0x7;
data[field::FLG_OFF1] = raw | (((chunks >> 8) << 3) as u8);
data[field::FLG_OFF0] = chunks as u8;
}
/// Set the time to live field.
#[inline(always)]
pub fn set_ttl(&mut self, value: u8) {
let data = self.buffer.as_mut();
data[field::TTL] = value
}
/// Set the protocol field.
#[inline(always)]
pub fn set_protocol(&mut self, value: ProtocolType) {
let data = self.buffer.as_mut();
data[field::PROTOCOL] = value.into()
}
/// Set the header checksum field.
#[inline(always)]
pub fn set_checksum(&mut self, value: u16) {
let data = self.buffer.as_mut();
NetworkEndian::write_u16(&mut data[field::CHECKSUM], value)
}
/// Set the source address field.
#[inline(always)]
pub fn set_src_addr(&mut self, value: Address) {
let data = self.buffer.as_mut();
data[field::SRC_ADDR].copy_from_slice(value.as_bytes())
}
/// Set the destination address field.
#[inline(always)]
pub fn set_dst_addr(&mut self, value: Address) {
let data = self.buffer.as_mut();
data[field::DST_ADDR].copy_from_slice(value.as_bytes())
}
/// Return a mutable pointer to the payload.
#[inline(always)]
pub fn payload_mut(&mut self) -> &mut [u8] {
let range = self.header_len() as usize..;
let data = self.buffer.as_mut();
&mut data[range]
}
/// Compute and fill in the header checksum.
pub fn fill_checksum(&mut self) {
let checksum = {
let data = self.buffer.as_ref();
checksum(&data[..self.header_len() as usize])
};
self.set_checksum(checksum)
}
}
#[cfg(test)]
mod test {
use super::*;
static PACKET_BYTES: [u8; 30] =
[0x54, 0x00, 0x00, 0x1e,
0x01, 0x02, 0x16, 0x03,
0x1a, 0x01, 0x12, 0x6f,
0x11, 0x12, 0x13, 0x14,
0x21, 0x22, 0x23, 0x24,
0xaa, 0x00, 0x00, 0x00,
0x00, 0x00, 0x00, 0x00,
0x00, 0xff];
static PAYLOAD_BYTES: [u8; 10] =
[0xaa, 0x00, 0x00, 0x00,
0x00, 0x00, 0x00, 0x00,
0x00, 0xff];
#[test]
fn test_deconstruct() {
let packet = Packet::new(&PACKET_BYTES[..]).unwrap();
assert_eq!(packet.version(), 4);
assert_eq!(packet.header_len(), 20);
assert_eq!(packet.dscp(), 0);
assert_eq!(packet.ecn(), 0);
assert_eq!(packet.total_len(), 30);
assert_eq!(packet.ident(), 0x102);
assert_eq!(packet.more_frags(), true);
assert_eq!(packet.dont_frag(), true);
assert_eq!(packet.frag_offset(), 0x203 * 8);
assert_eq!(packet.ttl(), 0x1a);
assert_eq!(packet.protocol(), ProtocolType::Icmp);
assert_eq!(packet.checksum(), 0x126f);
assert_eq!(packet.src_addr(), Address([0x11, 0x12, 0x13, 0x14]));
assert_eq!(packet.dst_addr(), Address([0x21, 0x22, 0x23, 0x24]));
assert_eq!(packet.verify_checksum(), true);
assert_eq!(packet.payload(), &PAYLOAD_BYTES[..]);
}
#[test]
fn test_construct() {
let mut bytes = vec![0; 30];
let mut packet = Packet::new(&mut bytes).unwrap();
packet.set_version(4);
packet.set_header_len(20);
packet.set_dscp(0);
packet.set_ecn(0);
packet.set_total_len(30);
packet.set_ident(0x102);
packet.set_more_frags(true);
packet.set_dont_frag(true);
packet.set_frag_offset(0x203 * 8);
packet.set_ttl(0x1a);
packet.set_protocol(ProtocolType::Icmp);
packet.set_src_addr(Address([0x11, 0x12, 0x13, 0x14]));
packet.set_dst_addr(Address([0x21, 0x22, 0x23, 0x24]));
packet.fill_checksum();
packet.payload_mut().copy_from_slice(&PAYLOAD_BYTES[..]);
assert_eq!(&packet.into_inner()[..], &PACKET_BYTES[..]);
}
}