vpncloud/src/ethernet.rs

use std::{mem, ptr, fmt, fs};
use std::net::SocketAddr;
use std::collections::HashMap;
use std::os::unix::io::{AsRawFd, RawFd};
use std::io::{Result as IoResult, Error as IoError, Read, Write};

use super::cloud::{Error, Table, InterfaceMessage, VirtualInterface};
use super::util::{as_bytes, as_obj};

use time::{Duration, SteadyTime};

extern {
    fn setup_tap_device(fd: i32, ifname: *mut u8) -> i32;
}


#[derive(Clone, Copy, Hash, PartialEq, Eq, PartialOrd, Ord)]
pub struct Mac(pub [u8; 6]);

impl fmt::Debug for Mac {
    fn fmt(&self, formatter: &mut fmt::Formatter) -> Result<(), fmt::Error> {
        write!(formatter, "{:x}:{:x}:{:x}:{:x}:{:x}:{:x}",
            self.0[0], self.0[1], self.0[2], self.0[3], self.0[4], self.0[5])
    }
}

pub type VlanId = u16;

#[derive(Debug, Clone, Copy, PartialEq, Eq, Hash)]
pub struct EthAddr {
    pub mac: Mac,
    pub vlan: Option<VlanId>
}


#[derive(PartialEq)]
pub struct Frame {
    pub src: EthAddr,
    pub dst: EthAddr
}

impl fmt::Debug for Frame {
    fn fmt(&self, formatter: &mut fmt::Formatter) -> Result<(), fmt::Error> {
        write!(formatter, "src: {:?}, dst: {:?}, vlan: {:?}", self.src.mac, self.dst.mac, self.src.vlan)
    }
}

impl InterfaceMessage for Frame {
    type Address = EthAddr;

    fn src(&self) -> Self::Address {
        self.src
    }

    fn dst(&self) -> Self::Address {
        self.dst
    }

    fn encode_to(&self, payload: &[u8], data: &mut [u8]) -> usize {
        assert!(data.len() >= 16 + payload.len());
        let mut pos = 0;
        unsafe {
            let dst_dat = as_bytes::<Mac>(&self.dst.mac);
            ptr::copy_nonoverlapping(dst_dat.as_ptr(), data[pos..].as_mut_ptr(), dst_dat.len());
            pos += dst_dat.len();
            let src_dat = as_bytes::<Mac>(&self.src.mac);
            ptr::copy_nonoverlapping(src_dat.as_ptr(), data[pos..].as_mut_ptr(), src_dat.len());
            pos += src_dat.len();
            if let Some(vlan) = self.src.vlan {
                data[pos] = 0x81; data[pos+1] = 0x00;
                pos += 2;
                let vlan_dat = mem::transmute::<u16, [u8; 2]>(vlan.to_be());
                ptr::copy_nonoverlapping(vlan_dat.as_ptr(), data[pos..].as_mut_ptr(), vlan_dat.len());
                pos += vlan_dat.len();
            }
            ptr::copy_nonoverlapping(payload.as_ptr(), data[pos..].as_mut_ptr(), payload.len());
        }
        pos += payload.len();
        pos
    }

    fn parse_from(data: &[u8]) -> Result<(Frame, &[u8]), Error> {
        if data.len() < 14 {
            return Err(Error::ParseError("Frame is too short"));
        }
        let mut pos = 0;
        let dst = *unsafe { as_obj::<Mac>(&data[pos..]) };
        pos += mem::size_of::<Mac>();
        let src = *unsafe { as_obj::<Mac>(&data[pos..]) };
        pos += mem::size_of::<Mac>();
        let mut vlan = None;
        let mut payload = &data[pos..];
        if data[pos] == 0x81 && data[pos+1] == 0x00 {
            pos += 2;
            if data.len() < pos + 2 {
                return Err(Error::ParseError("Vlan frame is too short"));
            }
            vlan = Some(u16::from_be(* unsafe { as_obj::<u16>(&data[pos..]) }));
            pos += 2;
            payload = &data[pos..];
        }
        Ok((Frame{src: EthAddr{mac: src, vlan: vlan}, dst: EthAddr{mac: dst, vlan: vlan}}, payload))
    }
}


pub struct TapDevice {
    fd: fs::File,
    ifname: String
}

impl TapDevice {
    pub fn new(ifname: &str) -> IoResult<Self> {
        let fd = try!(fs::OpenOptions::new().read(true).write(true).open("/dev/net/tun"));
        let mut ifname_string = String::with_capacity(32);
        ifname_string.push_str(ifname);
        ifname_string.push('\0');
        let mut ifname_c = ifname_string.into_bytes();
        let res = unsafe { setup_tap_device(fd.as_raw_fd(), ifname_c.as_mut_ptr()) };
        match res {
            0 => Ok(TapDevice{fd: fd, ifname: String::from_utf8(ifname_c).unwrap()}),
            _ => Err(IoError::last_os_error())
        }
    }

    #[inline(always)]
    pub fn ifname(&self) -> &str {
        &self.ifname
    }
}

impl AsRawFd for TapDevice {
    fn as_raw_fd(&self) -> RawFd {
        self.fd.as_raw_fd()
    }
}

impl VirtualInterface for TapDevice {
    fn read<'a, T: InterfaceMessage>(&mut self, mut buffer: &'a mut [u8]) -> Result<(T, &'a[u8]), Error> {
        let size = match self.fd.read(&mut buffer) {
            Ok(size) => size,
            Err(_) => return Err(Error::TunTapDevError("Read error"))
        };
        T::parse_from(&buffer[..size])
    }

    fn write<T: InterfaceMessage>(&mut self, msg: &T, payload: &[u8]) -> Result<(), Error> {
        let mut buffer = [0u8; 64*1024];
        let size = msg.encode_to(payload, &mut buffer);
        match self.fd.write_all(&buffer[..size]) {
            Ok(_) => Ok(()),
            Err(_) => Err(Error::TunTapDevError("Write error"))
        }
    }
}


struct MacTableValue {
    address: SocketAddr,
    timeout: SteadyTime
}


pub struct MacTable {
    table: HashMap<EthAddr, MacTableValue>,
    timeout: Duration
}

impl MacTable {
    pub fn new(timeout: Duration) -> MacTable {
        MacTable{table: HashMap::new(), timeout: timeout}
    }
}

impl Table for MacTable {
    type Address = EthAddr;

    fn housekeep(&mut self) {
        let now = SteadyTime::now();
        let mut del: Vec<Self::Address> = Vec::new();
        for (&key, val) in &self.table {
            if val.timeout < now {
                del.push(key);
            }
        }
        for key in del {
            info!("Forgot mac: {:?} (vlan {:?})", key.mac, key.vlan);
            self.table.remove(&key);
        }
    }

    fn learn(&mut self, key: Self::Address, addr: SocketAddr) {
       let value = MacTableValue{address: addr, timeout: SteadyTime::now()+self.timeout};
       if self.table.insert(key, value).is_none() {
           info!("Learned mac: {:?} (vlan {:?}) => {}", key.mac, key.vlan, addr);
       }
    }

    fn lookup(&self, key: Self::Address) -> Option<SocketAddr> {
       match self.table.get(&key) {
           Some(value) => Some(value.address),
           None => None
       }
    }
}


#[test]
fn without_vlan() {
    let src = Mac([1,2,3,4,5,6]);
    let dst = Mac([6,5,4,3,2,1]);
    let payload = [1,2,3,4,5,6,7,8];
    let mut buf = [0u8; 1024];
    let frame = Frame{src: EthAddr{mac: src, vlan: None}, dst: EthAddr{mac: dst, vlan: None}};
    let size = frame.encode_to(&payload, &mut buf);
    assert_eq!(size, 20);
    assert_eq!(&buf[..size], &[6,5,4,3,2,1,1,2,3,4,5,6,1,2,3,4,5,6,7,8]);
    let (frame2, payload2) = Frame::parse_from(&buf[..size]).unwrap();
    assert_eq!(frame, frame2);
    assert_eq!(payload, payload2);
}

#[test]
fn with_vlan() {
    let src = Mac([1,2,3,4,5,6]);
    let dst = Mac([6,5,4,3,2,1]);
    let payload = [1,2,3,4,5,6,7,8];
    let mut buf = [0u8; 1024];
    let frame = Frame{src: EthAddr{mac: src, vlan: Some(1234)}, dst: EthAddr{mac: dst, vlan: Some(1234)}};
    let size = frame.encode_to(&payload, &mut buf);
    assert_eq!(size, 24);
    assert_eq!(&buf[..size], &[6,5,4,3,2,1,1,2,3,4,5,6,0x81,0,4,210,1,2,3,4,5,6,7,8]);
    let (frame2, payload2) = Frame::parse_from(&buf[..size]).unwrap();
    assert_eq!(frame, frame2);
    assert_eq!(payload, payload2);
}