nazrin/api/src/net/cidr.rs

use std::fmt;
use std::net::{AddrParseError, Ipv4Addr};
use std::num::ParseIntError;
use std::str::FromStr;

use serde::{de, Deserialize, Serialize};

#[derive(Debug)]
pub enum Error {
    Malformed,
    AddrParse(AddrParseError),
    SuffixParse(ParseIntError),
    InvalidSize,
    HostBitsTooLarge,
}

impl fmt::Display for Error {
    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
        match self {
            Self::Malformed => write!(f, "Malformed address/cidr combination"),
            Self::AddrParse(er) => write!(f, "Couldn't parse address: {}", er),
            Self::SuffixParse(er) => write!(f, "Couldn't parse CIDR suffix: {}", er),
            Self::InvalidSize => write!(f, "Byte array needs to be at least 5 bytes long"),
            Self::HostBitsTooLarge => write!(
                f,
                "Provided host does not match bits allowed by subnet mask"
            ),
        }
    }
}

impl std::error::Error for Error {}

#[derive(Clone, Debug, PartialEq, Eq, PartialOrd, Ord)]
pub struct CidrV4 {
    pub addr: Ipv4Addr,
    cidr: u8,
    netmask: u32,
}

impl fmt::Display for CidrV4 {
    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
        write!(f, "{}/{}", self.addr, self.cidr)
    }
}

impl FromStr for CidrV4 {
    type Err = Error;
    fn from_str(s: &str) -> Result<Self, Self::Err> {
        let parts = s.split('/').collect::<Vec<&str>>();

        match parts.len() {
            2 => {
                let addr = Ipv4Addr::from_str(parts[0]).map_err(Error::AddrParse)?;
                let cidr = u8::from_str(parts[1]).map_err(Error::SuffixParse)?;
                Ok(CidrV4::new(addr, cidr))
            }
            _ => Err(Error::Malformed),
        }
    }
}

impl Serialize for CidrV4 {
    fn serialize<S>(&self, serializer: S) -> Result<S::Ok, S::Error>
    where
        S: serde::Serializer,
    {
        serializer.serialize_str(&self.to_string())
    }
}

impl<'de> Deserialize<'de> for CidrV4 {
    fn deserialize<D>(deserializer: D) -> Result<Self, D::Error>
    where
        D: serde::Deserializer<'de>,
    {
        let s: String = Deserialize::deserialize(deserializer)?;
        CidrV4::from_str(s.as_str()).map_err(de::Error::custom)
    }
}

impl From<[u8; 5]> for CidrV4 {
    fn from(octets: [u8; 5]) -> Self {
        let addr = Ipv4Addr::new(octets[0], octets[1], octets[2], octets[3]);
        let cidr = octets[4];
        Self::new(addr, cidr)
    }
}

impl TryFrom<&[u8]> for CidrV4 {
    type Error = Error;
    fn try_from(value: &[u8]) -> Result<Self, Self::Error> {
        if value.len() < 5 {
            Err(Error::InvalidSize)
        } else {
            // unwrap should be fine here, since we already validate for size?
            let arr: [u8; 5] = value[0..5].try_into().unwrap();
            Ok(Self::from(arr))
        }
    }
}

impl CidrV4 {
    pub fn new(addr: Ipv4Addr, cidr: u8) -> Self {
        let netmask = match cidr {
            0 => 0,
            32.. => u32::MAX,
            c => ((1u32 << c) - 1) << (32 - c),
        };

        CidrV4 {
            addr,
            cidr,
            netmask,
        }
    }

    /// Get the subnet mask as an Ipv4Addr.
    pub fn netmask(&self) -> Ipv4Addr {
        Ipv4Addr::from(self.netmask)
    }

    /// Get the network address.
    pub fn network(&self) -> CidrV4 {
        CidrV4::new(
            Ipv4Addr::from(u32::from(self.addr) & self.netmask),
            self.cidr,
        )
    }

    /// Get the network bit length in CIDR notation.
    pub fn cidr(&self) -> u8 {
        self.cidr
    }

    /// Get the broadcast address for the network.
    pub fn broadcast(&self) -> Ipv4Addr {
        Ipv4Addr::from(u32::from(self.network().addr) | !self.netmask)
    }

    /// Determine if a network contains a given address.
    ///
    /// This method is not affected by the object's host address.
    pub fn contains(&self, addr: &Ipv4Addr) -> bool {
        if self.cidr == 32 {
            &self.addr == addr
        } else {
            &self.broadcast() > addr && addr > &self.network().addr
        }
    }

    /// Gets only the host bits for a given Ipv4 address.
    ///
    /// This method is not affected by the object's host address.
    pub fn host_bits(&self, addr: &Ipv4Addr) -> u32 {
        let addr_bits = u32::from(*addr);
        addr_bits & !self.netmask
    }

    /// Create an IP from a given u32 of host bits.
    ///
    /// This method is not affected by the object's host address.
    pub fn make_ip(&self, host_bits: u32) -> Result<Ipv4Addr, Error> {
        if host_bits > !self.netmask {
            Err(Error::HostBitsTooLarge)
        } else {
            Ok((host_bits | u32::from(self.network().addr)).into())
        }
    }

    /// Get the address and CIDR bit length as an array of bytes.
    ///
    /// This is in big endian format, so e.g., 192.168.0.5/24 would
    /// be returned as `[192, 168, 0, 5, 24]`.
    pub fn octets(&self) -> [u8; 5] {
        [self.network().addr.octets().as_slice(), &[self.cidr]]
            .concat()
            .try_into()
            .unwrap()
    }
}

#[cfg(test)]
mod test {
    use crate::net::cidr::CidrV4;
    use std::{net::Ipv4Addr, str::FromStr};

    const ADDR_BYTES: u32 = 0xc0_a8_02_a9; // 192.168.2.169
    #[allow(clippy::unusual_byte_groupings)]
    const NETWORK_TRUTH_MAP: &[(u8, u32, u32, [u8; 5])] = &[
        (
            8,
            0b11111111_00000000_00000000_00000000,
            0xc0_00_00_00,
            [0xc0, 0, 0, 0, 8],
        ),
        (
            16,
            0b11111111_11111111_00000000_00000000,
            0xc0_a8_00_00,
            [0xc0, 0xa8, 0, 0, 16],
        ),
        (
            25,
            0b11111111_11111111_11111111_10000000,
            0xc0_a8_02_80,
            [0xc0, 0xa8, 0x02, 0x80, 25],
        ),
        (0, 0, 0, [0u8; 5]),
        (
            32,
            0b11111111_11111111_11111111_11111111,
            0xc0_a8_02_a9,
            [0xc0, 0xa8, 0x02, 0xa9, 32],
        ),
    ];

    #[test]
    fn v4_constructor() {
        for (cidr, netmask, net_addr, _) in NETWORK_TRUTH_MAP {
            let test = CidrV4::new(Ipv4Addr::from(ADDR_BYTES), *cidr);
            assert_eq!(u32::from(test.netmask()), *netmask);
            assert_eq!(test.cidr(), *cidr);
            assert_eq!(u32::from(test.network().addr), *net_addr);
        }
    }

    #[test]
    fn v4_fromstr() {
        let addr = Ipv4Addr::from(ADDR_BYTES);
        for (cidr, _netmask, net_addr, _) in NETWORK_TRUTH_MAP {
            let addr_str = format!("{}/{}", addr, cidr);
            println!(">> {}", addr_str);
            let cidr = CidrV4::from_str(&addr_str).unwrap();
            assert_eq!(cidr.network().addr, Ipv4Addr::from(*net_addr));
            assert!(cidr.contains(&addr));
        }
    }

    #[test]
    fn v4_contains() {
        let yes = Ipv4Addr::from(ADDR_BYTES);
        let no = Ipv4Addr::from(0x08_08_08_08);

        let cidr = CidrV4::new(yes, 8);
        assert!(cidr.contains(&yes));
        assert!(!cidr.contains(&no));
    }

    #[test]
    fn v4_octets() {
        for (cidr, _, _, netbytes) in NETWORK_TRUTH_MAP {
            let test = CidrV4::new(Ipv4Addr::from(ADDR_BYTES), *cidr);
            assert_eq!(&test.octets(), netbytes);
        }
    }
}