Restructure IO traits.

2019-10-09 15:08:26 +02:00
parent c82d3e554b
commit 761c46064d
16 changed files with 643 additions and 376 deletions
--- a/src/config.rs
+++ b/src/config.rs
@@ -0,0 +1,183 @@
+use std::error::Error;
+use std::net::{IpAddr, SocketAddr};
+use x25519_dalek::{PublicKey, StaticSecret};
+
+use crate::wireguard::Wireguard;
+use crate::types::{Bind, Endpoint, Tun};
+
+///
+/// The goal of the configuration interface is, among others,
+/// to hide the IO implementations (over which the WG device is generic),
+/// from the configuration and UAPI code.
+
+/// Describes a snapshot of the state of a peer
+pub struct PeerState {
+    rx_bytes: u64,
+    tx_bytes: u64,
+    last_handshake_time_sec: u64,
+    last_handshake_time_nsec: u64,
+    public_key: PublicKey,
+    allowed_ips: Vec<(IpAddr, u32)>,
+}
+
+pub enum ConfigError {
+    NoSuchPeer
+}
+
+impl ConfigError {
+
+    fn errno(&self) -> i32 {
+        match self {
+            NoSuchPeer => 1,
+        }
+    }
+}
+
+/// Exposed configuration interface
+pub trait Configuration {
+    /// Updates the private key of the device
+    ///
+    /// # Arguments
+    ///
+    /// - `sk`: The new private key (or None, if the private key should be cleared)
+    fn set_private_key(&self, sk: Option<StaticSecret>);
+
+    /// Returns the private key of the device
+    ///
+    /// # Returns
+    ///
+    /// The private if set, otherwise None.
+    fn get_private_key(&self) -> Option<StaticSecret>;
+
+    /// Returns the protocol version of the device
+    ///
+    /// # Returns
+    ///
+    /// An integer indicating the protocol version
+    fn get_protocol_version(&self) -> usize;
+
+    fn set_listen_port(&self, port: u16) -> Option<ConfigError>;
+
+    /// Set the firewall mark (or similar, depending on platform)
+    ///
+    /// # Arguments
+    ///
+    /// - `mark`: The fwmark value
+    ///
+    /// # Returns
+    ///
+    /// An error if this operation is not supported by the underlying
+    /// "bind" implementation.
+    fn set_fwmark(&self, mark: Option<u32>) -> Option<ConfigError>;
+
+    /// Removes all peers from the device
+    fn replace_peers(&self);
+
+    /// Remove the peer from the
+    ///
+    /// # Arguments
+    ///
+    /// - `peer`: The public key of the peer to remove
+    ///
+    /// # Returns
+    ///
+    /// If the peer does not exists this operation is a noop
+    fn remove_peer(&self, peer: PublicKey);
+
+    /// Adds a new peer to the device
+    ///
+    /// # Arguments
+    ///
+    /// - `peer`: The public key of the peer to add
+    ///
+    /// # Returns
+    ///
+    /// A bool indicating if the peer was added.
+    ///
+    /// If the peer already exists this operation is a noop
+    fn add_peer(&self, peer: PublicKey) -> bool;
+
+    /// Update the psk of a peer
+    ///
+    /// # Arguments
+    ///
+    /// - `peer`: The public key of the peer
+    /// - `psk`: The new psk or None if the psk should be unset
+    ///
+    /// # Returns
+    ///
+    /// An error if no such peer exists
+    fn set_preshared_key(&self, peer: PublicKey, psk: Option<[u8; 32]>) -> Option<ConfigError>;
+
+    /// Update the endpoint of the
+    ///
+    /// # Arguments
+    ///
+    /// - `peer': The public key of the peer
+    /// - `psk`
+    fn set_endpoint(&self, peer: PublicKey, addr: SocketAddr) -> Option<ConfigError>;
+
+    /// Update the endpoint of the
+    ///
+    /// # Arguments
+    ///
+    /// - `peer': The public key of the peer
+    /// - `psk`
+    fn set_persistent_keepalive_interval(&self, peer: PublicKey) -> Option<ConfigError>;
+
+    /// Remove all allowed IPs from the peer
+    ///
+    /// # Arguments
+    ///
+    /// - `peer': The public key of the peer
+    ///
+    /// # Returns
+    ///
+    /// An error if no such peer exists
+    fn replace_allowed_ips(&self, peer: PublicKey) -> Option<ConfigError>;
+
+    /// Add a new allowed subnet to the peer
+    ///
+    /// # Arguments
+    ///
+    /// - `peer`: The public key of the peer
+    /// - `ip`: Subnet mask
+    /// - `masklen`:
+    ///
+    /// # Returns
+    ///
+    /// An error if the peer does not exist
+    ///
+    /// # Note:
+    ///
+    /// The API must itself sanitize the (ip, masklen) set:
+    /// The ip should be masked to remove any set bits right of the first "masklen" bits.
+    fn add_allowed_ip(&self, peer: PublicKey, ip: IpAddr, masklen: u32) -> Option<ConfigError>;
+
+    /// Returns the state of all peers
+    ///
+    /// # Returns
+    ///
+    /// A list of structures describing the state of each peer
+    fn get_peers(&self) -> Vec<PeerState>;
+}
+
+impl <T : Tun, B : Bind>Configuration for Wireguard<T, B> {
+
+    fn set_private_key(&self, sk : Option<StaticSecret>) {
+        self.set_key(sk)
+    }
+
+    fn get_private_key(&self) -> Option<StaticSecret> {
+        self.get_sk()
+    }
+
+    fn get_protocol_version(&self) -> usize {
+        1
+    }
+
+    fn set_listen_port(&self, port : u16) -> Option<ConfigError> {
+
+    }
+
+}
--- a/src/handshake/device.rs
+++ b/src/handshake/device.rs
@@ -76,6 +76,15 @@ impl Device {
        }
    }

+    /// Return the secret key of the device
+    /// 
+    /// # Returns
+    /// 
+    /// A secret key (x25519 scalar)
+    pub fn get_sk(&self) -> StaticSecret {
+        StaticSecret::from(self.sk.to_bytes())
+    }
+
    /// Add a new public key to the state machine
    /// To remove public keys, you must create a new machine instance
    ///
--- a/src/main.rs
+++ b/src/main.rs
@@ -5,6 +5,7 @@ extern crate jemallocator;
 #[global_allocator]
 static ALLOC: jemallocator::Jemalloc = jemallocator::Jemalloc;

+// mod config;
 mod constants;
 mod handshake;
 mod router;
@@ -14,7 +15,8 @@ mod wireguard;

 #[cfg(test)]
 mod tests {
-    use crate::types::{dummy, Bind};
+    use crate::types::tun::Tun;
+    use crate::types::{bind, dummy, tun};
    use crate::wireguard::Wireguard;

    use std::thread;
@@ -27,7 +29,8 @@ mod tests {
    #[test]
    fn test_pure_wireguard() {
        init();
-        let wg = Wireguard::new(dummy::TunTest::new(), dummy::VoidBind::new());
+        let (reader, writer, mtu) = dummy::TunTest::create("name").unwrap();
+        let wg: Wireguard<dummy::TunTest, dummy::PairBind> = Wireguard::new(reader, writer, mtu);
        thread::sleep(Duration::from_millis(500));
    }
 }
--- a/src/router/device.rs
+++ b/src/router/device.rs
@@ -17,21 +17,23 @@ use super::constants::*;
 use super::ip::*;
 use super::messages::{TransportHeader, TYPE_TRANSPORT};
 use super::peer::{new_peer, Peer, PeerInner};
-use super::types::{Callbacks, Opaque, RouterError};
+use super::types::{Callbacks, RouterError};
 use super::workers::{worker_parallel, JobParallel, Operation};
 use super::SIZE_MESSAGE_PREFIX;

-use super::super::types::{Bind, KeyPair, Tun};
+use super::super::types::{KeyPair, Endpoint, bind, tun};

-pub struct DeviceInner<C: Callbacks, T: Tun, B: Bind> {
-    // IO & timer callbacks
-    pub tun: T,
-    pub bind: B,
+pub struct DeviceInner<E : Endpoint, C: Callbacks, T: tun::Writer, B: bind::Writer<E>> {
+    // inbound writer (TUN)
+    pub inbound: T,
+
+    // outbound writer (Bind)
+    pub outbound: RwLock<Option<B>>,

    // routing
-    pub recv: RwLock<HashMap<u32, Arc<DecryptionState<C, T, B>>>>, // receiver id -> decryption state
-    pub ipv4: RwLock<IpLookupTable<Ipv4Addr, Arc<PeerInner<C, T, B>>>>, // ipv4 cryptkey routing
-    pub ipv6: RwLock<IpLookupTable<Ipv6Addr, Arc<PeerInner<C, T, B>>>>, // ipv6 cryptkey routing
+    pub recv: RwLock<HashMap<u32, Arc<DecryptionState<E, C, T, B>>>>, // receiver id -> decryption state
+    pub ipv4: RwLock<IpLookupTable<Ipv4Addr, Arc<PeerInner<E, C, T, B>>>>, // ipv4 cryptkey routing
+    pub ipv6: RwLock<IpLookupTable<Ipv6Addr, Arc<PeerInner<E, C, T, B>>>>, // ipv6 cryptkey routing

    // work queues
    pub queue_next: AtomicUsize, // next round-robin index
@@ -45,20 +47,20 @@ pub struct EncryptionState {
    pub death: Instant, // (birth + reject-after-time - keepalive-timeout - rekey-timeout)
 }

-pub struct DecryptionState<C: Callbacks, T: Tun, B: Bind> {
+pub struct DecryptionState<E : Endpoint, C: Callbacks, T: tun::Writer, B: bind::Writer<E>> {
    pub keypair: Arc<KeyPair>,
    pub confirmed: AtomicBool,
    pub protector: Mutex<AntiReplay>,
-    pub peer: Arc<PeerInner<C, T, B>>,
+    pub peer: Arc<PeerInner<E, C, T, B>>,
    pub death: Instant, // time when the key can no longer be used for decryption
 }

-pub struct Device<C: Callbacks, T: Tun, B: Bind> {
-    state: Arc<DeviceInner<C, T, B>>,     // reference to device state
+pub struct Device<E : Endpoint, C: Callbacks, T: tun::Writer, B: bind::Writer<E>> {
+    state: Arc<DeviceInner<E, C, T, B>>,     // reference to device state
    handles: Vec<thread::JoinHandle<()>>, // join handles for workers
 }

-impl<C: Callbacks, T: Tun, B: Bind> Drop for Device<C, T, B> {
+impl<E : Endpoint, C: Callbacks, T: tun::Writer, B: bind::Writer<E>> Drop for Device<E, C, T, B> {
    fn drop(&mut self) {
        debug!("router: dropping device");

@@ -83,10 +85,10 @@ impl<C: Callbacks, T: Tun, B: Bind> Drop for Device<C, T, B> {
 }

 #[inline(always)]
-fn get_route<C: Callbacks, T: Tun, B: Bind>(
-    device: &Arc<DeviceInner<C, T, B>>,
+fn get_route<E : Endpoint, C: Callbacks, T: tun::Writer, B: bind::Writer<E>>(
+    device: &Arc<DeviceInner<E, C, T, B>>,
    packet: &[u8],
-) -> Option<Arc<PeerInner<C, T, B>>> {
+) -> Option<Arc<PeerInner<E, C, T, B>>> {
    // ensure version access within bounds
    if packet.len() < 1 {
        return None;
@@ -122,12 +124,12 @@ fn get_route<C: Callbacks, T: Tun, B: Bind>(
    }
 }

-impl<C: Callbacks, T: Tun, B: Bind> Device<C, T, B> {
-    pub fn new(num_workers: usize, tun: T, bind: B) -> Device<C, T, B> {
+impl<E : Endpoint, C: Callbacks, T: tun::Writer, B: bind::Writer<E>> Device<E, C, T, B> {
+    pub fn new(num_workers: usize, tun: T) -> Device<E, C, T, B> {
        // allocate shared device state
        let mut inner = DeviceInner {
-            tun,
-            bind,
+            inbound: tun,
+            outbound: RwLock::new(None),
            queues: Mutex::new(Vec::with_capacity(num_workers)),
            queue_next: AtomicUsize::new(0),
            recv: RwLock::new(HashMap::new()),
@@ -159,7 +161,7 @@ impl<C: Callbacks, T: Tun, B: Bind> Device<C, T, B> {
    /// # Returns
    ///
    /// A atomic ref. counted peer (with liftime matching the device)
-    pub fn new_peer(&self, opaque: C::Opaque) -> Peer<C, T, B> {
+    pub fn new_peer(&self, opaque: C::Opaque) -> Peer<E, C, T, B> {
        new_peer(self.state.clone(), opaque)
    }

@@ -199,7 +201,7 @@ impl<C: Callbacks, T: Tun, B: Bind> Device<C, T, B> {
    /// # Returns
    ///
    ///
-    pub fn recv(&self, src: B::Endpoint, msg: Vec<u8>) -> Result<(), RouterError> {
+    pub fn recv(&self, src: E, msg: Vec<u8>) -> Result<(), RouterError> {
        // parse / cast
        let (header, _) = match LayoutVerified::new_from_prefix(&msg[..]) {
            Some(v) => v,
@@ -231,4 +233,11 @@ impl<C: Callbacks, T: Tun, B: Bind> Device<C, T, B> {

        Ok(())
    }
+
+    /// Set outbound writer
+    /// 
+    /// 
+    pub fn set_outbound_writer(&self, new : B) {
+        *self.state.outbound.write() = Some(new);
+    }
 }
--- a/src/router/peer.rs
+++ b/src/router/peer.rs
@@ -14,7 +14,7 @@ use treebitmap::IpLookupTable;
 use zerocopy::LayoutVerified;

 use super::super::constants::*;
-use super::super::types::{Bind, Endpoint, KeyPair, Tun};
+use super::super::types::{Endpoint, KeyPair, bind, tun};

 use super::anti_replay::AntiReplay;
 use super::device::DecryptionState;
@@ -39,28 +39,28 @@ pub struct KeyWheel {
    retired: Vec<u32>,              // retired ids
 }

-pub struct PeerInner<C: Callbacks, T: Tun, B: Bind> {
-    pub device: Arc<DeviceInner<C, T, B>>,
+pub struct PeerInner<E : Endpoint, C: Callbacks, T: tun::Writer, B: bind::Writer<E>> {
+    pub device: Arc<DeviceInner<E, C, T, B>>,
    pub opaque: C::Opaque,
    pub outbound: Mutex<SyncSender<JobOutbound>>,
-    pub inbound: Mutex<SyncSender<JobInbound<C, T, B>>>,
+    pub inbound: Mutex<SyncSender<JobInbound<E, C, T, B>>>,
    pub staged_packets: Mutex<ArrayDeque<[Vec<u8>; MAX_STAGED_PACKETS], Wrapping>>,
    pub keys: Mutex<KeyWheel>,
    pub ekey: Mutex<Option<EncryptionState>>,
-    pub endpoint: Mutex<Option<B::Endpoint>>,
+    pub endpoint: Mutex<Option<E>>,
 }

-pub struct Peer<C: Callbacks, T: Tun, B: Bind> {
-    state: Arc<PeerInner<C, T, B>>,
+pub struct Peer<E : Endpoint, C: Callbacks, T: tun::Writer, B: bind::Writer<E>> {
+    state: Arc<PeerInner<E, C, T, B>>,
    thread_outbound: Option<thread::JoinHandle<()>>,
    thread_inbound: Option<thread::JoinHandle<()>>,
 }

-fn treebit_list<A, E, C: Callbacks, T: Tun, B: Bind>(
-    peer: &Arc<PeerInner<C, T, B>>,
-    table: &spin::RwLock<IpLookupTable<A, Arc<PeerInner<C, T, B>>>>,
-    callback: Box<dyn Fn(A, u32) -> E>,
-) -> Vec<E>
+fn treebit_list<A, R, E : Endpoint, C: Callbacks, T: tun::Writer, B: bind::Writer<E>>(
+    peer: &Arc<PeerInner<E, C, T, B>>,
+    table: &spin::RwLock<IpLookupTable<A, Arc<PeerInner<E, C, T, B>>>>,
+    callback: Box<dyn Fn(A, u32) -> R>,
+) -> Vec<R>
 where
    A: Address,
 {
@@ -74,9 +74,9 @@ where
    res
 }

-fn treebit_remove<A: Address, C: Callbacks, T: Tun, B: Bind>(
-    peer: &Peer<C, T, B>,
-    table: &spin::RwLock<IpLookupTable<A, Arc<PeerInner<C, T, B>>>>,
+fn treebit_remove<E : Endpoint, A: Address, C: Callbacks, T: tun::Writer, B: bind::Writer<E>>(
+    peer: &Peer<E, C, T, B>,
+    table: &spin::RwLock<IpLookupTable<A, Arc<PeerInner<E, C, T, B>>>>,
 ) {
    let mut m = table.write();

@@ -107,8 +107,8 @@ impl EncryptionState {
    }
 }

-impl<C: Callbacks, T: Tun, B: Bind> DecryptionState<C, T, B> {
-    fn new(peer: &Arc<PeerInner<C, T, B>>, keypair: &Arc<KeyPair>) -> DecryptionState<C, T, B> {
+impl<E : Endpoint, C: Callbacks, T: tun::Writer, B: bind::Writer<E>> DecryptionState<E, C, T, B> {
+    fn new(peer: &Arc<PeerInner<E, C, T, B>>, keypair: &Arc<KeyPair>) -> DecryptionState<E, C, T, B> {
        DecryptionState {
            confirmed: AtomicBool::new(keypair.initiator),
            keypair: keypair.clone(),
@@ -119,7 +119,7 @@ impl<C: Callbacks, T: Tun, B: Bind> DecryptionState<C, T, B> {
    }
 }

-impl<C: Callbacks, T: Tun, B: Bind> Drop for Peer<C, T, B> {
+impl<E : Endpoint, C: Callbacks, T: tun::Writer, B: bind::Writer<E>> Drop for Peer<E, C, T, B> {
    fn drop(&mut self) {
        let peer = &self.state;

@@ -167,10 +167,10 @@ impl<C: Callbacks, T: Tun, B: Bind> Drop for Peer<C, T, B> {
    }
 }

-pub fn new_peer<C: Callbacks, T: Tun, B: Bind>(
-    device: Arc<DeviceInner<C, T, B>>,
+pub fn new_peer<E : Endpoint, C: Callbacks, T: tun::Writer, B: bind::Writer<E>>(
+    device: Arc<DeviceInner<E, C, T, B>>,
    opaque: C::Opaque,
-) -> Peer<C, T, B> {
+) -> Peer<E, C, T, B> {
    let (out_tx, out_rx) = sync_channel(128);
    let (in_tx, in_rx) = sync_channel(128);

@@ -215,7 +215,7 @@ pub fn new_peer<C: Callbacks, T: Tun, B: Bind>(
    }
 }

-impl<C: Callbacks, T: Tun, B: Bind> PeerInner<C, T, B> {
+impl<E : Endpoint, C: Callbacks, T: tun::Writer, B: bind::Writer<E>> PeerInner<E, C, T, B> {
    fn send_staged(&self) -> bool {
        debug!("peer.send_staged");
        let mut sent = false;
@@ -286,8 +286,8 @@ impl<C: Callbacks, T: Tun, B: Bind> PeerInner<C, T, B> {

    pub fn recv_job(
        &self,
-        src: B::Endpoint,
-        dec: Arc<DecryptionState<C, T, B>>,
+        src: E,
+        dec: Arc<DecryptionState<E, C, T, B>>,
        mut msg: Vec<u8>,
    ) -> Option<JobParallel> {
        let (tx, rx) = oneshot();
@@ -370,7 +370,7 @@ impl<C: Callbacks, T: Tun, B: Bind> PeerInner<C, T, B> {
    }
 }

-impl<C: Callbacks, T: Tun, B: Bind> Peer<C, T, B> {
+impl<E : Endpoint, C: Callbacks, T: tun::Writer, B: bind::Writer<E>> Peer<E, C, T, B> {
    /// Set the endpoint of the peer
    ///
    /// # Arguments
@@ -381,9 +381,9 @@ impl<C: Callbacks, T: Tun, B: Bind> Peer<C, T, B> {
    ///
    /// This API still permits support for the "sticky socket" behavior,
    /// as sockets should be "unsticked" when manually updating the endpoint
-    pub fn set_endpoint(&self, address: SocketAddr) {
+    pub fn set_endpoint(&self, endpoint: E) {
        debug!("peer.set_endpoint");
-        *self.state.endpoint.lock() = Some(B::Endpoint::from_address(address));
+        *self.state.endpoint.lock() = Some(endpoint);
    }

    /// Returns the current endpoint of the peer (for configuration)
@@ -591,11 +591,12 @@ impl<C: Callbacks, T: Tun, B: Bind> Peer<C, T, B> {
        debug!("peer.send");
        let inner = &self.state;
        match inner.endpoint.lock().as_ref() {
-            Some(endpoint) => inner
-                .device
-                .bind
-                .send(msg, endpoint)
-                .map_err(|_| RouterError::SendError),
+            Some(endpoint) => inner.device
+                .outbound
+                .read()
+                .as_ref()
+                .ok_or(RouterError::SendError)
+                .and_then(|w| w.write(msg, endpoint).map_err(|_| RouterError::SendError) ),
            None => Err(RouterError::NoEndpoint),
        }
    }
--- a/src/router/tests.rs
+++ b/src/router/tests.rs
@@ -1,18 +1,18 @@
-use std::error::Error;
-use std::fmt;
-use std::net::{IpAddr, SocketAddr};
+use std::net::IpAddr;
 use std::sync::atomic::Ordering;
-use std::sync::mpsc::{sync_channel, Receiver, SyncSender};
 use std::sync::Arc;
 use std::sync::Mutex;
 use std::thread;
-use std::time::{Duration, Instant};
+use std::time::Duration;

 use num_cpus;
 use pnet::packet::ipv4::MutableIpv4Packet;
 use pnet::packet::ipv6::MutableIpv6Packet;

-use super::super::types::{dummy, Bind, Endpoint, Key, KeyPair, Tun};
+use super::super::types::bind::*;
+use super::super::types::tun::*;
+use super::super::types::*;
+
 use super::{Callbacks, Device, SIZE_MESSAGE_PREFIX};

 extern crate test;
@@ -145,8 +145,9 @@ mod tests {
        }

        // create device
-        let router: Device<BencherCallbacks, dummy::TunTest, dummy::VoidBind> =
-            Device::new(num_cpus::get(), dummy::TunTest {}, dummy::VoidBind::new());
+        let (_reader, tun_writer, _mtu) = dummy::TunTest::create("name").unwrap();
+        let router: Device<_, BencherCallbacks, dummy::TunTest, dummy::VoidBind> =
+            Device::new(num_cpus::get(), tun_writer);

        // add new peer
        let opaque = Arc::new(AtomicUsize::new(0));
@@ -174,8 +175,9 @@ mod tests {
        init();

        // create device
-        let router: Device<TestCallbacks, _, _> =
-            Device::new(1, dummy::TunTest::new(), dummy::VoidBind::new());
+        let (_reader, tun_writer, _mtu) = dummy::TunTest::create("name").unwrap();
+        let router: Device<_, TestCallbacks, _, _> = Device::new(1, tun_writer);
+        router.set_outbound_writer(dummy::VoidBind::new());

        let tests = vec![
            ("192.168.1.0", 24, "192.168.1.20", true),
@@ -315,12 +317,18 @@ mod tests {
        ];

        for (stage, p1, p2) in tests.iter() {
-            // create matching devices
-            let (bind1, bind2) = dummy::PairBind::pair();
-            let router1: Device<TestCallbacks, _, _> =
-                Device::new(1, dummy::TunTest::new(), bind1.clone());
-            let router2: Device<TestCallbacks, _, _> =
-                Device::new(1, dummy::TunTest::new(), bind2.clone());
+            let ((bind_reader1, bind_writer1), (bind_reader2, bind_writer2)) =
+                dummy::PairBind::pair();
+
+            // create matching device
+            let (tun_writer1, _, _) = dummy::TunTest::create("tun1").unwrap();
+            let (tun_writer2, _, _) = dummy::TunTest::create("tun1").unwrap();
+
+            let router1: Device<_, TestCallbacks, _, _> = Device::new(1, tun_writer1);
+            router1.set_outbound_writer(bind_writer1);
+
+            let router2: Device<_, TestCallbacks, _, _> = Device::new(1, tun_writer2);
+            router2.set_outbound_writer(bind_writer2);

            // prepare opaque values for tracing callbacks

@@ -339,7 +347,7 @@ mod tests {
            let peer2 = router2.new_peer(opaq2.clone());
            let mask: IpAddr = mask.parse().unwrap();
            peer2.add_subnet(mask, *len);
-            peer2.set_endpoint("127.0.0.1:8080".parse().unwrap());
+            peer2.set_endpoint(dummy::UnitEndpoint::new());

            if *stage {
                // stage a packet which can be used for confirmation (in place of a keepalive)
@@ -372,7 +380,7 @@ mod tests {

            // read confirming message received by the other end ("across the internet")
            let mut buf = vec![0u8; 2048];
-            let (len, from) = bind1.recv(&mut buf).unwrap();
+            let (len, from) = bind_reader1.read(&mut buf).unwrap();
            buf.truncate(len);
            router1.recv(from, buf).unwrap();

@@ -411,7 +419,7 @@ mod tests {

                // receive ("across the internet") on the other end
                let mut buf = vec![0u8; 2048];
-                let (len, from) = bind2.recv(&mut buf).unwrap();
+                let (len, from) = bind_reader2.read(&mut buf).unwrap();
                buf.truncate(len);
                router2.recv(from, buf).unwrap();

--- a/src/router/types.rs
+++ b/src/router/types.rs
@@ -1,6 +1,8 @@
 use std::error::Error;
 use std::fmt;

+use super::super::types::Endpoint;
+
 pub trait Opaque: Send + Sync + 'static {}

 impl<T> Opaque for T where T: Send + Sync + 'static {}
--- a/src/router/workers.rs
+++ b/src/router/workers.rs
@@ -17,7 +17,7 @@ use super::messages::{TransportHeader, TYPE_TRANSPORT};
 use super::peer::PeerInner;
 use super::types::Callbacks;

-use super::super::types::{Bind, Tun};
+use super::super::types::{Endpoint, tun, bind};
 use super::ip::*;

 const SIZE_TAG: usize = 16;
@@ -38,18 +38,18 @@ pub struct JobBuffer {
 pub type JobParallel = (oneshot::Sender<JobBuffer>, JobBuffer);

 #[allow(type_alias_bounds)]
-pub type JobInbound<C, T, B: Bind> = (
-    Arc<DecryptionState<C, T, B>>,
-    B::Endpoint,
+pub type JobInbound<E, C, T, B: bind::Writer<E>> = (
+    Arc<DecryptionState<E, C, T, B>>,
+    E,
    oneshot::Receiver<JobBuffer>,
 );

 pub type JobOutbound = oneshot::Receiver<JobBuffer>;

 #[inline(always)]
-fn check_route<C: Callbacks, T: Tun, B: Bind>(
-    device: &Arc<DeviceInner<C, T, B>>,
-    peer: &Arc<PeerInner<C, T, B>>,
+fn check_route<E : Endpoint, C: Callbacks, T: tun::Writer, B: bind::Writer<E>>(
+    device: &Arc<DeviceInner<E, C, T, B>>,
+    peer: &Arc<PeerInner<E, C, T, B>>,
    packet: &[u8],
 ) -> Option<usize> {
    match packet[0] >> 4 {
@@ -93,10 +93,10 @@ fn check_route<C: Callbacks, T: Tun, B: Bind>(
    }
 }

-pub fn worker_inbound<C: Callbacks, T: Tun, B: Bind>(
-    device: Arc<DeviceInner<C, T, B>>, // related device
-    peer: Arc<PeerInner<C, T, B>>,     // related peer
-    receiver: Receiver<JobInbound<C, T, B>>,
+pub fn worker_inbound<E : Endpoint, C: Callbacks, T: tun::Writer, B: bind::Writer<E>>(
+    device: Arc<DeviceInner<E, C, T, B>>, // related device
+    peer: Arc<PeerInner<E, C, T, B>>,     // related peer
+    receiver: Receiver<JobInbound<E, C, T, B>>,
 ) {
    loop {
        // fetch job
@@ -153,7 +153,7 @@ pub fn worker_inbound<C: Callbacks, T: Tun, B: Bind>(
                        if let Some(inner_len) = check_route(&device, &peer, &packet[..length]) {
                            debug_assert!(inner_len <= length, "should be validated");
                            if inner_len <= length {
-                                sent = match device.tun.write(&packet[..inner_len]) {
+                                sent = match device.inbound.write(&packet[..inner_len]) {
                                    Err(e) => {
                                        debug!("failed to write inbound packet to TUN: {:?}", e);
                                        false
@@ -176,9 +176,9 @@ pub fn worker_inbound<C: Callbacks, T: Tun, B: Bind>(
    }
 }

-pub fn worker_outbound<C: Callbacks, T: Tun, B: Bind>(
-    device: Arc<DeviceInner<C, T, B>>, // related device
-    peer: Arc<PeerInner<C, T, B>>,     // related peer
+pub fn worker_outbound<E : Endpoint, C: Callbacks, T: tun::Writer, B: bind::Writer<E>>(
+    device: Arc<DeviceInner<E, C, T, B>>, // related device
+    peer: Arc<PeerInner<E, C, T, B>>,     // related peer
    receiver: Receiver<JobOutbound>,
 ) {
    loop {
@@ -198,12 +198,17 @@ pub fn worker_outbound<C: Callbacks, T: Tun, B: Bind>(
                if buf.okay {
                    // write to UDP bind
                    let xmit = if let Some(dst) = peer.endpoint.lock().as_ref() {
-                        match device.bind.send(&buf.msg[..], dst) {
-                            Err(e) => {
-                                debug!("failed to send outbound packet: {:?}", e);
-                                false
+                        let send : &Option<B> = &*device.outbound.read();
+                        if let Some(writer) = send.as_ref() {
+                            match writer.write(&buf.msg[..], dst) {
+                                Err(e) => {
+                                    debug!("failed to send outbound packet: {:?}", e);
+                                    false
+                                }
+                                Ok(_) => true,
                            }
-                            Ok(_) => true,
+                        } else {
+                            false
                        }
                    } else {
                        false
--- a/src/timers.rs
+++ b/src/timers.rs
@@ -7,7 +7,7 @@ use hjul::{Runner, Timer};

 use crate::constants::*;
 use crate::router::Callbacks;
-use crate::types::{Bind, Tun};
+use crate::types::{tun, bind};
 use crate::wireguard::{Peer, PeerInner};

 pub struct Timers {
@@ -23,8 +23,8 @@ pub struct Timers {
 impl Timers {
    pub fn new<T, B>(runner: &Runner, peer: Peer<T, B>) -> Timers
    where
-        T: Tun,
-        B: Bind,
+        T: tun::Tun,
+        B: bind::Bind,
    {
        // create a timer instance for the provided peer
        Timers {
@@ -103,7 +103,7 @@ impl Timers {

 pub struct Events<T, B>(PhantomData<(T, B)>);

-impl<T: Tun, B: Bind> Callbacks for Events<T, B> {
+impl<T: tun::Tun, B: bind::Bind> Callbacks for Events<T, B> {
    type Opaque = Arc<PeerInner<B>>;

    fn send(peer: &Self::Opaque, size: usize, data: bool, sent: bool) {
--- a/src/types/bind.rs
+++ b/src/types/bind.rs
@@ -1,73 +1,28 @@
 use super::Endpoint;
-use std::error;
+use std::error::Error;

-/// Traits representing the "internet facing" end of the VPN.
-///
-/// In practice this is a UDP socket (but the router interface is agnostic).
-/// Often these traits will be implemented on the same type.
+pub trait Reader<E: Endpoint>: Send + Sync {
+    type Error: Error;

-/// Bind interface provided to the router code
-pub trait RouterBind: Send + Sync {
-    type Error: error::Error;
+    fn read(&self, buf: &mut [u8]) -> Result<(usize, E), Self::Error>;
+}
+
+pub trait Writer<E: Endpoint>: Send + Sync + Clone + 'static {
+    type Error: Error;
+
+    fn write(&self, buf: &[u8], dst: &E) -> Result<(), Self::Error>;
+}
+
+pub trait Bind: Send + Sync + 'static {
+    type Error: Error;
    type Endpoint: Endpoint;

-    /// Receive a buffer on the bind
-    ///
-    /// # Arguments
-    ///
-    /// - `buf`, buffer for storing the packet. If the buffer is too short, the packet should just be truncated.
-    ///
-    /// # Note
-    ///
-    /// The size of the buffer is derieved from the MTU of the Tun device.
-    fn recv(&self, buf: &mut [u8]) -> Result<(usize, Self::Endpoint), Self::Error>;
+    /* Until Rust gets type equality constraints these have to be generic */
+    type Writer: Writer<Self::Endpoint>;
+    type Reader: Reader<Self::Endpoint>;

-    /// Send a buffer to the endpoint
-    ///
-    /// # Arguments
-    ///
-    /// - `buf`, packet src buffer (in practice the body of a UDP datagram)
-    /// - `dst`, destination endpoint (in practice, src: (ip, port) + dst: (ip, port) for sticky sockets)
-    ///
-    /// # Returns
-    ///
-    /// The unit type or an error if transmission failed
-    fn send(&self, buf: &[u8], dst: &Self::Endpoint) -> Result<(), Self::Error>;
-}
-
-/// Bind interface provided for configuration (setting / getting the port)
-pub trait ConfigBind {
-    type Error: error::Error;
-
-    /// Return a new (unbound) instance of a configuration bind
-    fn new() -> Self;
-
-    /// Updates the port of the bind
-    ///
-    /// # Arguments
-    ///
-    /// - `port`, the new port to bind to. 0 means any available port.
-    ///
-    /// # Returns
-    ///
-    /// The unit type or an error, if binding fails
-    fn set_port(&self, port: u16) -> Result<(), Self::Error>;
-
-    /// Returns the current port of the bind
-    fn get_port(&self) -> Option<u16>;
-
-    /// Set the mark (e.g. on Linus this is the fwmark) on the bind
-    ///
-    /// # Arguments
-    ///
-    /// - `mark`, the mark to set
-    ///
-    /// # Note
-    ///
-    /// The mark should be retained accross calls to `set_port`.
-    ///
-    /// # Returns
-    ///
-    /// The unit type or an error, if the operation fails due to permission errors
-    fn set_mark(&self, mark: u16) -> Result<(), Self::Error>;
+    /* Used to close the reader/writer when binding to a new port */
+    type Closer;
+
+    fn bind(port: u16) -> Result<(Self::Reader, Self::Writer, Self::Closer, u16), Self::Error>;
 }
--- a/src/types/dummy.rs
+++ b/src/types/dummy.rs
@@ -5,8 +5,9 @@ use std::sync::mpsc::{sync_channel, Receiver, SyncSender};
 use std::sync::Arc;
 use std::sync::Mutex;
 use std::time::Instant;
+use std::marker;

-use super::{Bind, Endpoint, Key, KeyPair, Tun};
+use super::*;

 /* This submodule provides pure/dummy implementations of the IO interfaces
 * for use in unit tests thoughout the project.
@@ -72,104 +73,103 @@ impl Endpoint for UnitEndpoint {
    }
 }

+impl UnitEndpoint {
+    pub fn new() -> UnitEndpoint {
+        UnitEndpoint{}
+    }
+}
+
+/* */
+
 #[derive(Clone, Copy)]
 pub struct TunTest {}

-impl Tun for TunTest {
+impl tun::Reader for TunTest {
    type Error = TunError;

-    fn mtu(&self) -> usize {
-        1500
-    }
-
    fn read(&self, _buf: &mut [u8], _offset: usize) -> Result<usize, Self::Error> {
        Ok(0)
    }
+}
+
+impl tun::MTU for TunTest {
+    fn mtu(&self) -> usize {
+        1500
+    }
+}
+
+impl tun::Writer for TunTest {
+    type Error = TunError;

    fn write(&self, _src: &[u8]) -> Result<(), Self::Error> {
        Ok(())
    }
 }

+impl tun::Tun for TunTest {
+    type Writer = TunTest;
+    type Reader = TunTest;
+    type MTU = TunTest;
+    type Error = TunError;
+}
+
 impl TunTest {
-    pub fn new() -> TunTest {
-        TunTest {}
+    pub fn create(_name: &str) -> Result<(TunTest, TunTest, TunTest), TunError> {
+        Ok((TunTest {},TunTest {}, TunTest{}))
    }
 }

-/* Bind implemenentations */
+/* Void Bind */

 #[derive(Clone, Copy)]
 pub struct VoidBind {}

-impl Bind for VoidBind {
+impl bind::Reader<UnitEndpoint> for VoidBind {
    type Error = BindError;
-    type Endpoint = UnitEndpoint;

-    fn new() -> VoidBind {
-        VoidBind {}
-    }
-
-    fn set_port(&self, _port: u16) -> Result<(), Self::Error> {
-        Ok(())
-    }
-
-    fn get_port(&self) -> Option<u16> {
-        None
-    }
-
-    fn recv(&self, _buf: &mut [u8]) -> Result<(usize, Self::Endpoint), Self::Error> {
+    fn read(&self, _buf: &mut [u8]) -> Result<(usize, UnitEndpoint), Self::Error> {
        Ok((0, UnitEndpoint {}))
    }
+}

-    fn send(&self, _buf: &[u8], _dst: &Self::Endpoint) -> Result<(), Self::Error> {
+impl bind::Writer<UnitEndpoint> for VoidBind {
+    type Error = BindError;
+
+    fn write(&self, _buf: &[u8], _dst: &UnitEndpoint) -> Result<(), Self::Error> {
        Ok(())
    }
 }

-#[derive(Clone)]
-pub struct PairBind {
-    send: Arc<Mutex<SyncSender<Vec<u8>>>>,
-    recv: Arc<Mutex<Receiver<Vec<u8>>>>,
-}
-
-impl PairBind {
-    pub fn pair() -> (PairBind, PairBind) {
-        let (tx1, rx1) = sync_channel(128);
-        let (tx2, rx2) = sync_channel(128);
-        (
-            PairBind {
-                send: Arc::new(Mutex::new(tx1)),
-                recv: Arc::new(Mutex::new(rx2)),
-            },
-            PairBind {
-                send: Arc::new(Mutex::new(tx2)),
-                recv: Arc::new(Mutex::new(rx1)),
-            },
-        )
-    }
-}
-
-impl Bind for PairBind {
+impl bind::Bind for VoidBind {
    type Error = BindError;
    type Endpoint = UnitEndpoint;

-    fn new() -> PairBind {
-        PairBind {
-            send: Arc::new(Mutex::new(sync_channel(0).0)),
-            recv: Arc::new(Mutex::new(sync_channel(0).1)),
-        }
-    }
+    type Reader = VoidBind;
+    type Writer = VoidBind;
+    type Closer = ();

-    fn set_port(&self, _port: u16) -> Result<(), Self::Error> {
-        Ok(())
+    fn bind(_ : u16) -> Result<(Self::Reader, Self::Writer, Self::Closer, u16), Self::Error> {
+        Ok((VoidBind{}, VoidBind{}, (), 2600))
    }
+}

-    fn get_port(&self) -> Option<u16> {
-        None
+impl VoidBind {
+    pub fn new() -> VoidBind {
+        VoidBind{}
    }
+}

-    fn recv(&self, buf: &mut [u8]) -> Result<(usize, Self::Endpoint), Self::Error> {
+/* Pair Bind */
+
+#[derive(Clone)]
+pub struct PairReader<E> {
+    recv: Arc<Mutex<Receiver<Vec<u8>>>>,
+    _marker: marker::PhantomData<E>,
+}
+
+impl bind::Reader<UnitEndpoint> for PairReader<UnitEndpoint> {
+    type Error = BindError;
+    fn read(&self, buf: &mut [u8]) -> Result<(usize, UnitEndpoint), Self::Error> {
        let vec = self
            .recv
            .lock()
@@ -180,8 +180,11 @@ impl Bind for PairBind {
        buf[..len].copy_from_slice(&vec[..]);
        Ok((vec.len(), UnitEndpoint {}))
    }
+}

-    fn send(&self, buf: &[u8], _dst: &Self::Endpoint) -> Result<(), Self::Error> {
+impl bind::Writer<UnitEndpoint> for PairWriter<UnitEndpoint> {
+    type Error = BindError;
+    fn write(&self, buf: &[u8], _dst: &UnitEndpoint) -> Result<(), Self::Error> {
        let owned = buf.to_owned();
        match self.send.lock().unwrap().send(owned) {
            Err(_) => Err(BindError::Disconnected),
@@ -190,6 +193,57 @@ impl Bind for PairBind {
    }
 }

+#[derive(Clone)]
+pub struct PairWriter<E> {
+    send: Arc<Mutex<SyncSender<Vec<u8>>>>,
+    _marker: marker::PhantomData<E>,
+}
+
+#[derive(Clone)]
+pub struct PairBind {}
+
+impl PairBind {
+    pub fn pair<E>() -> ((PairReader<E>, PairWriter<E>), (PairReader<E>, PairWriter<E>)) {
+        let (tx1, rx1) = sync_channel(128);
+        let (tx2, rx2) = sync_channel(128);
+        (
+            (
+                PairReader{ 
+                    
+                    recv: Arc::new(Mutex::new(rx1)), 
+                    _marker: marker::PhantomData 
+                }, 
+                PairWriter{ 
+                    send: Arc::new(Mutex::new(tx2)),
+                    _marker: marker::PhantomData
+                }
+            ),
+            (
+                PairReader{ 
+                    recv: Arc::new(Mutex::new(rx2)),
+                    _marker: marker::PhantomData 
+                }, 
+                PairWriter{ 
+                    send: Arc::new(Mutex::new(tx1)),
+                    _marker: marker::PhantomData 
+                }
+            ),
+        )
+    }
+}
+
+impl bind::Bind for PairBind {
+    type Closer = ();
+    type Error = BindError;
+    type Endpoint = UnitEndpoint;
+    type Reader = PairReader<Self::Endpoint>;
+    type Writer = PairWriter<Self::Endpoint>;
+    
+    fn bind(_port: u16) -> Result<(Self::Reader, Self::Writer, Self::Closer, u16), Self::Error> {
+        Err(BindError::Disconnected)
+    }
+}
+
 pub fn keypair(initiator: bool) -> KeyPair {
    let k1 = Key {
        key: [0x53u8; 32],
--- a/src/types/endpoint.rs
+++ b/src/types/endpoint.rs
@@ -1,6 +1,6 @@
 use std::net::SocketAddr;

-pub trait Endpoint: Send {
+pub trait Endpoint: Send + 'static {
    fn from_address(addr: SocketAddr) -> Self;
    fn into_address(&self) -> SocketAddr;
 }
--- a/src/types/mod.rs
+++ b/src/types/mod.rs
@@ -1,12 +1,10 @@
 mod endpoint;
 mod keys;
-mod tun;
-mod udp;
+pub mod tun;
+pub mod bind;

 #[cfg(test)]
 pub mod dummy;

 pub use endpoint::Endpoint;
-pub use keys::{Key, KeyPair};
-pub use tun::Tun;
-pub use udp::Bind;
+pub use keys::{Key, KeyPair};
--- a/src/types/tun.rs
+++ b/src/types/tun.rs
@@ -1,18 +1,22 @@
-use std::error;
+use std::error::Error;

-pub trait Tun: Send + Sync + Clone + 'static {
-    type Error: error::Error;
+pub trait Writer: Send + Sync + 'static {
+    type Error: Error;

-    /// Returns the MTU of the device
+    /// Receive a cryptkey routed IP packet
    ///
-    /// This function needs to be efficient (called for every read).
-    /// The goto implementation strategy is to .load an atomic variable,
-    /// then use e.g. netlink to update the variable in a separate thread.
+    /// # Arguments
+    ///
+    /// - src: Buffer containing the IP packet to be written
    ///
    /// # Returns
    ///
-    /// The MTU of the interface in bytes
-    fn mtu(&self) -> usize;
+    /// Unit type or an error
+    fn write(&self, src: &[u8]) -> Result<(), Self::Error>;
+}
+
+pub trait Reader: Send + 'static {
+    type Error: Error;

    /// Reads an IP packet into dst[offset:] from the tunnel device
    ///
@@ -29,15 +33,24 @@ pub trait Tun: Send + Sync + Clone + 'static {
    ///
    /// The size of the IP packet (ignoring the header) or an std::error::Error instance:
    fn read(&self, buf: &mut [u8], offset: usize) -> Result<usize, Self::Error>;
+}

-    /// Writes an IP packet to the tunnel device
+pub trait MTU: Send + Sync + Clone + 'static {
+    /// Returns the MTU of the device
    ///
-    /// # Arguments
-    ///
-    /// - src: Buffer containing the IP packet to be written
+    /// This function needs to be efficient (called for every read).
+    /// The goto implementation strategy is to .load an atomic variable,
+    /// then use e.g. netlink to update the variable in a separate thread.
    ///
    /// # Returns
    ///
-    /// Unit type or an error
-    fn write(&self, src: &[u8]) -> Result<(), Self::Error>;
+    /// The MTU of the interface in bytes
+    fn mtu(&self) -> usize;
+}
+
+pub trait Tun: Send + Sync + 'static {
+    type Writer: Writer;
+    type Reader: Reader;
+    type MTU: MTU;
+    type Error: Error;
 }
--- a/src/types/udp.rs
+++ b/src/types/udp.rs
@@ -1,29 +0,0 @@
-use super::Endpoint;
-use std::error;
-
-/* Often times an a file descriptor in an atomic might suffice.
- */
-pub trait Bind: Send + Sync + Clone + 'static {
-    type Error: error::Error + Send;
-    type Endpoint: Endpoint;
-
-    fn new() -> Self;
-
-    /// Updates the port of the Bind
-    ///
-    /// # Arguments
-    ///
-    /// - port, The new port to bind to. 0 means any available port.
-    ///
-    /// # Returns
-    ///
-    /// The unit type or an error, if binding fails
-    fn set_port(&self, port: u16) -> Result<(), Self::Error>;
-
-    /// Returns the current port of the bind
-    fn get_port(&self) -> Option<u16>;
-
-    fn recv(&self, buf: &mut [u8]) -> Result<(usize, Self::Endpoint), Self::Error>;
-
-    fn send(&self, buf: &[u8], dst: &Self::Endpoint) -> Result<(), Self::Error>;
-}
--- a/src/wireguard.rs
+++ b/src/wireguard.rs
@@ -2,11 +2,13 @@ use crate::constants::*;
 use crate::handshake;
 use crate::router;
 use crate::timers::{Events, Timers};
-use crate::types::{Bind, Endpoint, Tun};
+
+use crate::types::Endpoint;
+use crate::types::tun::{Tun, Reader, MTU};
+use crate::types::bind::{Bind, Writer};

 use hjul::Runner;

-use std::cmp;
 use std::ops::Deref;
 use std::sync::atomic::{AtomicBool, AtomicU64, AtomicUsize, Ordering};
 use std::sync::Arc;
@@ -27,12 +29,20 @@ const SIZE_HANDSHAKE_QUEUE: usize = 128;
 const THRESHOLD_UNDER_LOAD: usize = SIZE_HANDSHAKE_QUEUE / 4;
 const DURATION_UNDER_LOAD: Duration = Duration::from_millis(10_000);

-#[derive(Clone)]
 pub struct Peer<T: Tun, B: Bind> {
-    pub router: Arc<router::Peer<Events<T, B>, T, B>>,
+    pub router: Arc<router::Peer<B::Endpoint, Events<T, B>, T::Writer, B::Writer>>,
    pub state: Arc<PeerInner<B>>,
 }

+impl <T  : Tun, B : Bind> Clone for Peer<T, B > {
+    fn clone(&self) -> Peer<T, B> {
+        Peer{
+            router: self.router.clone(),
+            state: self.state.clone()
+        }
+    }
+}
+
 pub struct PeerInner<B: Bind> {
    pub keepalive: AtomicUsize, // keepalive interval
    pub rx_bytes: AtomicU64,
@@ -66,20 +76,22 @@ pub enum HandshakeJob<E> {
 }

 struct WireguardInner<T: Tun, B: Bind> {
+    // provides access to the MTU value of the tun device 
+    // (otherwise owned solely by the router and a dedicated read IO thread)
+    mtu: T::MTU,
+    send: RwLock<Option<B::Writer>>,
+
    // identify and configuration map
    peers: RwLock<HashMap<[u8; 32], Peer<T, B>>>,

    // cryptkey router
-    router: router::Device<Events<T, B>, T, B>,
+    router: router::Device<B::Endpoint, Events<T, B>, T::Writer, B::Writer>,

    // handshake related state
    handshake: RwLock<Handshake>,
    under_load: AtomicBool,
    pending: AtomicUsize, // num of pending handshake packets in queue
    queue: Mutex<Sender<HandshakeJob<B::Endpoint>>>,
-
-    // IO
-    bind: B,
 }

 pub struct Wireguard<T: Tun, B: Bind> {
@@ -87,6 +99,17 @@ pub struct Wireguard<T: Tun, B: Bind> {
    state: Arc<WireguardInner<T, B>>,
 }

+/* Returns the padded length of a message:
+ *
+ * # Arguments
+ *
+ * - `size` : Size of unpadded message
+ * - `mtu` : Maximum transmission unit of the device
+ *
+ * # Returns
+ *
+ * The padded length (always less than or equal to the MTU)
+ */
 #[inline(always)]
 const fn padding(size: usize, mtu: usize) -> usize {
    #[inline(always)]
@@ -114,6 +137,15 @@ impl<T: Tun, B: Bind> Wireguard<T, B> {
        }
    }

+    pub fn get_sk(&self) -> Option<StaticSecret> {
+        let mut handshake = self.state.handshake.read();
+        if handshake.active {
+            Some(handshake.device.get_sk())
+        } else {
+            None
+        }
+    }
+
    pub fn new_peer(&self, pk: PublicKey) -> Peer<T, B> {
        let state = Arc::new(PeerInner {
            pk,
@@ -137,113 +169,36 @@ impl<T: Tun, B: Bind> Wireguard<T, B> {
        peer
    }

-    pub fn new(tun: T, bind: B) -> Wireguard<T, B> {
-        // create device state
-        let mut rng = OsRng::new().unwrap();
-        let (tx, rx): (Sender<HandshakeJob<B::Endpoint>>, _) = bounded(SIZE_HANDSHAKE_QUEUE);
-        let wg = Arc::new(WireguardInner {
-            peers: RwLock::new(HashMap::new()),
-            router: router::Device::new(num_cpus::get(), tun.clone(), bind.clone()),
-            pending: AtomicUsize::new(0),
-            handshake: RwLock::new(Handshake {
-                device: handshake::Device::new(StaticSecret::new(&mut rng)),
-                active: false,
-            }),
-            under_load: AtomicBool::new(false),
-            bind: bind.clone(),
-            queue: Mutex::new(tx),
-        });
+    pub fn new_bind(
+        reader: B::Reader,
+        writer: B::Writer,
+        closer: B::Closer
+    ) {

-        // start handshake workers
-        for _ in 0..num_cpus::get() {
-            let wg = wg.clone();
-            let rx = rx.clone();
-            let bind = bind.clone();
-            thread::spawn(move || {
-                // prepare OsRng instance for this thread
-                let mut rng = OsRng::new().unwrap();
+        // drop existing closer

-                // process elements from the handshake queue
-                for job in rx {
-                    wg.pending.fetch_sub(1, Ordering::SeqCst);
-                    let state = wg.handshake.read();
-                    if !state.active {
-                        continue;
-                    }

-                    match job {
-                        HandshakeJob::Message(msg, src) => {
-                            // feed message to handshake device
-                            let src_validate = (&src).into_address(); // TODO avoid
+        // swap IO thread for new reader

-                            // process message
-                            match state.device.process(
-                                &mut rng,
-                                &msg[..],
-                                if wg.under_load.load(Ordering::Relaxed) {
-                                    Some(&src_validate)
-                                } else {
-                                    None
-                                },
-                            ) {
-                                Ok((pk, msg, keypair)) => {
-                                    // send response
-                                    if let Some(msg) = msg {
-                                        let _ = bind.send(&msg[..], &src).map_err(|e| {
-                                            debug!(
-                                        "handshake worker, failed to send response, error = {:?}",
-                                        e
-                                    )
-                                        });
-                                    }
-
-                                    // update timers
-                                    if let Some(pk) = pk {
-                                        if let Some(peer) = wg.peers.read().get(pk.as_bytes()) {
-                                            // update endpoint (DISCUSS: right semantics?)
-                                            peer.router.set_endpoint(src_validate);
-
-                                            // add keypair to peer and free any unused ids
-                                            if let Some(keypair) = keypair {
-                                                for id in peer.router.add_keypair(keypair) {
-                                                    state.device.release(id);
-                                                }
-                                            }
-                                        }
-                                    }
-                                }
-                                Err(e) => debug!("handshake worker, error = {:?}", e),
-                            }
-                        }
-                        HandshakeJob::New(pk) => {
-                            let msg = state.device.begin(&mut rng, &pk).unwrap(); // TODO handle
-                            if let Some(peer) = wg.peers.read().get(pk.as_bytes()) {
-                                peer.router.send(&msg[..]);
-                                peer.timers.read().handshake_sent();
-                            }
-                        }
-                    }
-                }
-            });
-        }

        // start UDP read IO thread
+
+        /*
        {
            let wg = wg.clone();
-            let tun = tun.clone();
-            let bind = bind.clone();
+            let mtu = mtu.clone();
            thread::spawn(move || {
                let mut last_under_load =
                    Instant::now() - DURATION_UNDER_LOAD - Duration::from_millis(1000);

                loop {
                    // create vector big enough for any message given current MTU
-                    let size = tun.mtu() + handshake::MAX_HANDSHAKE_MSG_SIZE;
+                    let size = mtu.mtu() + handshake::MAX_HANDSHAKE_MSG_SIZE;
                    let mut msg: Vec<u8> = Vec::with_capacity(size);
                    msg.resize(size, 0);

                    // read UDP packet into vector
-                    let (size, src) = bind.recv(&mut msg).unwrap(); // TODO handle error
+                    let (size, src) = reader.read(&mut msg).unwrap(); // TODO handle error
                    msg.truncate(size);

                    // message type de-multiplexer
@@ -276,19 +231,120 @@ impl<T: Tun, B: Bind> Wireguard<T, B> {
                }
            });
        }
+        */
+
+    
+    }
+
+    pub fn new(
+        reader: T::Reader, 
+        writer: T::Writer, 
+        mtu: T::MTU,
+    ) -> Wireguard<T, B> {
+        // create device state
+        let mut rng = OsRng::new().unwrap();
+        let (tx, rx): (Sender<HandshakeJob<B::Endpoint>>, _) = bounded(SIZE_HANDSHAKE_QUEUE);
+        let wg = Arc::new(WireguardInner {
+            mtu: mtu.clone(),
+            peers: RwLock::new(HashMap::new()),
+            send: RwLock::new(None),
+            router: router::Device::new(num_cpus::get(), writer), // router owns the writing half
+            pending: AtomicUsize::new(0),
+            handshake: RwLock::new(Handshake {
+                device: handshake::Device::new(StaticSecret::new(&mut rng)),
+                active: false,
+            }),
+            under_load: AtomicBool::new(false),
+            queue: Mutex::new(tx),
+        });
+
+        // start handshake workers
+        for _ in 0..num_cpus::get() {
+            let wg = wg.clone();
+            let rx = rx.clone();
+            thread::spawn(move || {
+                // prepare OsRng instance for this thread
+                let mut rng = OsRng::new().unwrap();
+
+                // process elements from the handshake queue
+                for job in rx {
+                    wg.pending.fetch_sub(1, Ordering::SeqCst);
+                    let state = wg.handshake.read();
+                    if !state.active {
+                        continue;
+                    }
+
+                    match job {
+                        HandshakeJob::Message(msg, src) => {
+                            // feed message to handshake device
+                            let src_validate = (&src).into_address(); // TODO avoid
+
+                            // process message
+                            match state.device.process(
+                                &mut rng,
+                                &msg[..],
+                                if wg.under_load.load(Ordering::Relaxed) {
+                                    Some(&src_validate)
+                                } else {
+                                    None
+                                },
+                            ) {
+                                Ok((pk, msg, keypair)) => {
+                                    // send response
+                                    if let Some(msg) = msg {
+                                        let send : &Option<B::Writer> = &*wg.send.read();
+                                        if let Some(writer) = send.as_ref() {
+                                            let _ = writer.write(&msg[..], &src).map_err(|e| {
+                                                debug!(
+                                                    "handshake worker, failed to send response, error = {:?}",
+                                                    e
+                                                )
+                                            });
+                                        }
+                                    }
+
+                                    // update timers
+                                    if let Some(pk) = pk {
+                                        if let Some(peer) = wg.peers.read().get(pk.as_bytes()) {
+                                            // update endpoint
+                                            peer.router.set_endpoint(src);
+
+                                            // add keypair to peer and free any unused ids
+                                            if let Some(keypair) = keypair {
+                                                for id in peer.router.add_keypair(keypair) {
+                                                    state.device.release(id);
+                                                }
+                                            }
+                                        }
+                                    }
+                                }
+                                Err(e) => debug!("handshake worker, error = {:?}", e),
+                            }
+                        }
+                        HandshakeJob::New(pk) => {
+                            let msg = state.device.begin(&mut rng, &pk).unwrap(); // TODO handle
+                            if let Some(peer) = wg.peers.read().get(pk.as_bytes()) {
+                                peer.router.send(&msg[..]);
+                                peer.timers.read().handshake_sent();
+                            }
+                        }
+                    }
+                }
+            });
+        }

        // start TUN read IO thread
        {
            let wg = wg.clone();
            thread::spawn(move || loop {
                // create vector big enough for any transport message (based on MTU)
-                let mtu = tun.mtu();
+                let mtu = mtu.mtu();
                let size = mtu + router::SIZE_MESSAGE_PREFIX;
                let mut msg: Vec<u8> = Vec::with_capacity(size + router::CAPACITY_MESSAGE_POSTFIX);
                msg.resize(size, 0);

                // read a new IP packet
-                let payload = tun.read(&mut msg[..], router::SIZE_MESSAGE_PREFIX).unwrap();
+                let payload = reader.read(&mut msg[..], router::SIZE_MESSAGE_PREFIX).unwrap();
                debug!("TUN worker, IP packet of {} bytes (MTU = {})", payload, mtu);

                // truncate padding