WIP: TUN IO worker

Also removed the type parameters from the handshake device.

src/handshake/types.rs

@@ -1,6 +1,8 @@
 use std::error::Error;
 use std::fmt;
 
+use x25519_dalek::PublicKey;
+
 use crate::types::KeyPair;
 
 /* Internal types for the noise IKpsk2 implementation */
@@ -77,10 +79,10 @@ impl Error for HandshakeError {
     }
 }
 
-pub type Output<T> = (
-    Option<T>,       // external identifier associated with peer
-    Option<Vec<u8>>, // message to send
-    Option<KeyPair>, // resulting key-pair of successful handshake
+pub type Output = (
+    Option<PublicKey>, // external identifier associated with peer
+    Option<Vec<u8>>,   // message to send
+    Option<KeyPair>,   // resulting key-pair of successful handshake
 );
 
 // preshared key