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use nom::bits::{bits, streaming::take};
use nom::combinator::map_res;
use nom::error::{Error, ErrorKind};
use nom::multi::count;
use nom::number::complete::{be_u16, be_u32, u8};
use nom::sequence::tuple;
use nom::{Err, IResult};
use std::net::Ipv4Addr;
const VRRP_REQUIRED_VERSION: u8 = 2;
const VRRP_REQUIRED_TYPE: u8 = 1; // Advertisement
#[derive(Debug, Clone, PartialEq)]
pub enum VRRPv2Error {
VRRPv2ParseError,
}
type NomError<'a> = nom::Err<nom::error::Error<&'a [u8]>>;
impl From<NomError<'_>> for VRRPv2Error {
fn from(_: NomError) -> Self {
Self::VRRPv2ParseError
}
}
#[derive(Debug, PartialEq)]
pub enum VRRPVersion {
V2,
}
#[derive(Debug, PartialEq)]
pub enum VRRPv2Type {
VRRPv2Advertisement,
}
#[derive(Debug, PartialEq)]
pub enum VRRPv2AuthType {
VRRPv2AuthNoAuth = 0x00,
VRRPv2AuthReserved1 = 0x01,
VRRPv2AuthReserved2 = 0x02,
}
#[derive(Debug, PartialEq)]
pub struct VRRPv2 {
pub version: VRRPVersion,
pub type_: VRRPv2Type,
pub virtual_router_id: u8,
pub priority: u8,
pub count_ip_addrs: u8,
pub auth_type: VRRPv2AuthType,
pub advertisement_interval: u8,
pub checksum: u16,
pub ip_addrs: Vec<Ipv4Addr>,
}
fn two_nibbles(input: &[u8]) -> IResult<&[u8], (u8, u8)> {
bits::<_, _, Error<(&[u8], usize)>, _, _>(tuple((take(4usize), take(4usize))))(input)
}
fn parse_version_type(input: &[u8]) -> IResult<&[u8], (VRRPVersion, VRRPv2Type)> {
let (input, pair) = two_nibbles(input)?;
match pair {
(VRRP_REQUIRED_VERSION, VRRP_REQUIRED_TYPE) => {
Ok((input, (VRRPVersion::V2, VRRPv2Type::VRRPv2Advertisement)))
}
_ => Err(Err::Error(Error::new(input, ErrorKind::Alt))),
}
}
fn parse_auth_type(input: &[u8]) -> IResult<&[u8], VRRPv2AuthType> {
map_res(u8, |auth_type| {
Ok(match auth_type {
0 => VRRPv2AuthType::VRRPv2AuthNoAuth,
1 => VRRPv2AuthType::VRRPv2AuthReserved1,
2 => VRRPv2AuthType::VRRPv2AuthReserved2,
_ => return Err(Err::Error(Error::new(input, ErrorKind::Alt))),
})
})(input)
}
// Nightly has a nicer array_chunks API to express it more succinctly.
// let mut chunks = bytes.array_chunks(2);
// let mut sum = chunks.map(u16::from_ne_bytes).map(|b| b as u32).sum::<u32>();
// // handle the remainder
// if let Some([b]) = chunks.remainder() {
// sum += *b as u32
// }
// Shadowing can be used to avoid `mut`...
// let sum =...;
// let sum = (sum & 0xffff) + (sum >> 16);
// let sum = (sum & 0xffff) + (sum >> 16);
// manually un-rolling while loop since it's needed atmost twice for an u32.
fn validate_checksum(bytes: &[u8]) -> bool {
let mut sum: u32 = bytes.chunks(2).fold(0, |acc: u32, x| {
acc + u32::from(u16::from_ne_bytes(x.try_into().unwrap()))
});
while (sum >> 16) > 0 {
sum = (sum & 0xffff) + (sum >> 16);
}
let checksum = !(sum as u16);
checksum == 0
}
fn parse(input: &[u8]) -> IResult<&[u8], VRRPv2> {
if !validate_checksum(input) {
return Err(Err::Error(Error::new(input, ErrorKind::Alt)));
}
let (input, (version, type_)) = parse_version_type(input)?;
let (input, virtual_router_id) = u8(input)?;
let (input, priority) = u8(input)?;
let (input, count_ip_addrs) = u8(input)?;
let (input, auth_type) = parse_auth_type(input)?;
let (input, advertisement_interval) = u8(input)?;
let (input, checksum) = be_u16(input)?;
let (input, xs) = count(be_u32, usize::from(count_ip_addrs))(input)?;
let ip_addrs = xs.into_iter().map(Ipv4Addr::from).collect();
Ok((
input,
VRRPv2 {
version,
type_,
virtual_router_id,
priority,
count_ip_addrs,
auth_type,
advertisement_interval,
checksum,
ip_addrs,
},
))
}
pub fn from_bytes(bytes: &[u8]) -> Result<VRRPv2, VRRPv2Error> {
match parse(bytes) {
Ok((_, v)) => Ok(v),
Err(e) => Err(e.into()),
}
}
#[test]
fn test_standard_bytes() {
let bytes = [
0x21, 0x01, 0x64, 0x01, 0x00, 0x01, 0xba, 0x52, 0xc0, 0xa8, 0x00, 0x01, 0x00, 0x00, 0x00,
0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
];
let got = from_bytes(&bytes).unwrap();
let expected = VRRPv2 {
version: VRRPVersion::V2,
type_: VRRPv2Type::VRRPv2Advertisement,
virtual_router_id: 1,
priority: 100,
count_ip_addrs: 1,
auth_type: VRRPv2AuthType::VRRPv2AuthNoAuth,
checksum: 47698,
advertisement_interval: 1,
ip_addrs: vec![Ipv4Addr::from([192, 168, 0, 1])],
};
assert_eq!(got, expected);
}
#[test]
fn test_incomplete_bytes() {
let bytes = [0x21, 0x01];
let got = from_bytes(&bytes);
assert_eq!(got.is_err(), true);
assert_eq!(got.err(), Some(VRRPv2Error::VRRPv2ParseError));
}
#[test]
fn test_invalid_version_type() {
let bytes = [
0x00, 0x01, 0x64, 0x01, 0x00, 0x01, 0xba, 0x52, 0xc0, 0xa8, 0x00, 0x01, 0x00, 0x00, 0x00,
0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
];
let got = from_bytes(&bytes);
assert_eq!(got.is_err(), true);
assert_eq!(got.err(), Some(VRRPv2Error::VRRPv2ParseError));
}
#[test]
fn test_invalid_auth_type() {
let bytes = [
0x21, 0x01, 0x64, 0x01, 0x03, 0x01, 0xba, 0x52, 0xc0, 0xa8, 0x00, 0x01, 0x00, 0x00, 0x00,
0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
];
let got = from_bytes(&bytes);
assert_eq!(got.is_err(), true);
assert_eq!(got.err(), Some(VRRPv2Error::VRRPv2ParseError));
}
#[test]
fn test_invalid_checksum() {
let bytes = [
0x21, 0x01, 0x64, 0x01, 0x00, 0x01, 0xbb, 0x52, 0xc0, 0xa8, 0x00, 0x01, 0x00, 0x00, 0x00,
0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
];
let got = from_bytes(&bytes);
assert_eq!(got.is_err(), true);
assert_eq!(got.err(), Some(VRRPv2Error::VRRPv2ParseError));
}
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