nsc/src/sniffing/headers.rs

use tun::Error;
use std::fmt;

// Here we will recieve bytes and try to get their destanation & apply Rules for them.
use crate::config::Config;

#[derive(Debug, PartialEq)]
pub enum Protocol {
    TCP,
    UDP,
    Unsupported(u8)
}
type SourceV4Ip = Ipv4;
type SourceV6Ip = Ipv6;
pub enum IpVersion {
    V4,
    V6
}
// type IpVersion = String;
type Ipv4 = [u8; 4];
type Ipv6 = [u8; 16];
type Port = u16;
#[derive(Debug, PartialEq)]
pub enum PacketInfo {
    // <https://www.geeksforgeeks.org/computer-networks/what-is-ipv4/>
    V4 {
        src_ip: Ipv4,
        src_port: Port,
        dst_ip: Ipv4,
        dst_port: Port,
        protocol: Protocol,
        dns: bool
    },
    // <https://www.geeksforgeeks.org/computer-networks/internet-protocol-version-6-ipv6-header/>
    V6 {
        src_ip: Ipv6,
        src_port: Port,
        dst_ip: Ipv6,
        dst_port: Port,
        protocol: Protocol,
        dns: bool
    }
}

impl fmt::Display for PacketInfo {
    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
        if self.version() == "Ipv4" {
             let src_ip = self.src_ipv4_ip();
             let dst_ip = self.dst_ipv4_ip();
             write!(f, "{} {}.{}.{}.{}:{} -> {}.{}.{}.{}:{} PROTO {} DNS? {}", self.version(), src_ip[0], src_ip[1], src_ip[2], src_ip[3], self.src_port, dst_ip[0], dst_ip[1], dst_ip[2], dst_ip[3], self.dst_port(), self.protocol(), self.dns())
        }
        // write!(f, "{} {}:{} -> {}:{} PROTO {} DNS? {}", self.version(), self.)
    }
}

impl PacketInfo {
    pub fn dns(&self) -> &bool {
        match self {
            PacketInfo::V4 { dns, ..} => dns,
            PacketInfo::V6 { dns, ..} => dns,
        }
    }
    pub fn dst_ipv4_ip(&self) -> &SourceV4Ip {
        match self {
            PacketInfo::V4 { dst_ip, .. } => dst_ip,
            _ => &[0x0, 0x0, 0x0, 0x0].try_into().expect("this never should fail or even be called in the first place.")
        }
    }
    pub fn src_ipv6_ip(&self) -> &SourceV6Ip {
        match self {
            PacketInfo::V6 { src_ip, .. } => src_ip,
            _ => &[0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0].try_into().expect("this never should fail or even be called in the first place.")
        }
    }
    pub fn src_ipv4_ip(&self) -> &SourceV4Ip {
        match self {
            PacketInfo::V4 { src_ip, .. } => src_ip,
            _ => &[0x0, 0x0, 0x0, 0x0].try_into().expect("this never should fail or even be called in the first place.")
        }
    }
    pub fn src_ipv6_ip(&self) -> &SourceV6Ip {
            PacketInfo::V6.src_ip
    }
    pub fn version(&self) -> &IpVersion {
        match self {
            PacketInfo::V4 { .. }=> &IpVersion::V4,
            PacketInfo::V6 { .. }=> &IpVersion::V6
        }
    }
    pub fn protocol(&self) -> &Protocol {
        match self {
            PacketInfo::V4 { protocol, .. } => protocol,
            PacketInfo::V6 { protocol, .. } => protocol,
        }
    }
}

// TODO: move these to some appropriate file for code readability.
type GenericError = Box<dyn std::error::Error + Send + Sync + 'static>;
type SniffedPacket = Result<PacketInfo, Box<dyn std::error::Error + Send + Sync + 'static>>;
type Packet = [u8];

pub fn sniff_raw_packets(packet: &Packet) -> SniffedPacket {
    let ver = packet[0] >> 4;
    match ver {
        4 => {
            // Internet Header Length (IHL).
            let ihl = (packet[0] & 0x0F) as usize * 4;
            let dst_port = Port::from_be_bytes([packet[ihl+2], packet[ihl+3]]);
            let dns;
            if dst_port == 53 { dns = true; } else { dns = false; };
            // FIXME: hardcoded IPv4 port offset
            let v4 = PacketInfo::V4{
                src_ip: <Ipv4>::try_from(&packet[12..16])?,
                src_port: Port::from_be_bytes([packet[ihl], packet[ihl+1]]),
                dst_ip: <Ipv4>::try_from(&packet[16..20])?,
                dst_port,
                protocol: match packet[9] {
                    6 => Protocol::TCP,
                    17 => Protocol::UDP,
                    p => Protocol::Unsupported(p)
                },
                dns
            };
        if !matches!(v4.protocol(), Protocol::Unsupported(_)) {
            println!("{v4:?}");
        } else {
            // TODO: make --debug option which will include this diagnostic, for general use this
                // should be off
            // println!("oppsie unsupported protocol: {:?}", v4.protocol());
            }
            Ok(v4)
        },
        6 => {
            let dst_port = Port::from_be_bytes([packet[22], packet[23]]);
            let dns;
            if dst_port == 53 { dns = true; } else { dns = false; };
            let v6 = PacketInfo::V6{
                src_ip: <Ipv6>::try_from(&packet[8..24])?,
                src_port: Port::from_be_bytes([packet[40], packet[41]]),
                dst_ip: <Ipv6>::try_from(&packet[24..40])?,
                dst_port,
                protocol: match packet[6] {
                    6 => Protocol::TCP,
                    17 => Protocol::UDP,
                    p => Protocol::Unsupported(p)
                },
                dns
            };
        if !matches!(v6.protocol(), Protocol::Unsupported(_)) {
            println!("{v6:?}");
        } else {
            // TODO: make --debug option which will include this diagnostic, for general use this
                // should be off
            // println!("oppsie unsupported protocol: {:?}", v6.protocol());
            }
            Ok(v6)
        },
        ver => {
            Err(format!("unsuppiorted ver: {ver}").into())
        }
    }
}

pub fn apply_rules(config: Config, pinfo: PacketInfo) {
    todo!()
}