Split GenericSocket and LinkInterface

Keep socket and link logic separated. Allows for setting MTU
specifically for the link.

- UDP: hardcoded 1000
- TCP: ignored (.max)

TunnelKit/Sources/AppExtension/GenericSocket.swift

@@ -9,7 +9,7 @@
 import Foundation
 
 protocol LinkProducer {
-    func link() -> LinkInterface
+    func link(withMTU mtu: Int) -> LinkInterface
 }
 
 protocol GenericSocketDelegate: class {

TunnelKit/Sources/AppExtension/Transport/NETCPInterface.swift

@@ -12,16 +12,13 @@ import SwiftyBeaver
 
 private let log = SwiftyBeaver.self
 
-class NETCPInterface: NSObject, GenericSocket, LinkInterface {
+class NETCPInterface: NSObject, GenericSocket {
     private static var linkContext = 0
     
     private let impl: NWTCPConnection
     
-    private let maxPacketSize: Int
+    init(impl: NWTCPConnection) {
-
-    init(impl: NWTCPConnection, maxPacketSize: Int? = nil) {
         self.impl = impl
-        self.maxPacketSize = maxPacketSize ?? (512 * 1024)
         isActive = false
         isShutdown = false
     }
@@ -79,8 +76,8 @@ class NETCPInterface: NSObject, GenericSocket, LinkInterface {
         return NETCPInterface(impl: NWTCPConnection(upgradeFor: impl))
     }
     
-    func link() -> LinkInterface {
+    func link(withMTU mtu: Int) -> LinkInterface {
-        return self
+        return NETCPLinkInterface(impl: impl)
     }
     
     // MARK: Connection KVO (any queue)
@@ -148,12 +145,28 @@ class NETCPInterface: NSObject, GenericSocket, LinkInterface {
             break
         }
     }
+}
+
+class NETCPLinkInterface: LinkInterface {
+    private let impl: NWTCPConnection
+    
+    private let maxPacketSize: Int
+    
+    init(impl: NWTCPConnection, maxPacketSize: Int? = nil) {
+        self.impl = impl
+        self.mtu = .max
+        self.maxPacketSize = maxPacketSize ?? (512 * 1024)
+    }
 
     // MARK: LinkInterface
     
     let isReliable: Bool = true
 
-    let mtu: Int = .max
+    var remoteAddress: String? {
+        return (impl.remoteAddress as? NWHostEndpoint)?.hostname
+    }
+    
+    let mtu: Int
     
     var packetBufferSize: Int {
         return maxPacketSize

TunnelKit/Sources/AppExtension/Transport/NEUDPInterface.swift

@@ -12,16 +12,13 @@ import SwiftyBeaver
 
 private let log = SwiftyBeaver.self
 
-class NEUDPInterface: NSObject, GenericSocket, LinkInterface {
+class NEUDPInterface: NSObject, GenericSocket {
     private static var linkContext = 0
     
     private let impl: NWUDPSession
     
-    private let maxDatagrams: Int
+    init(impl: NWUDPSession) {
-
-    init(impl: NWUDPSession, maxDatagrams: Int? = nil) {
         self.impl = impl
-        self.maxDatagrams = maxDatagrams ?? 200
 
         isActive = false
         isShutdown = false
@@ -78,8 +75,8 @@ class NEUDPInterface: NSObject, GenericSocket, LinkInterface {
         return NEUDPInterface(impl: NWUDPSession(upgradeFor: impl))
     }
     
-    func link() -> LinkInterface {
+    func link(withMTU mtu: Int) -> LinkInterface {
-        return self
+        return NEUDPLinkInterface(impl: impl, mtu: mtu)
     }
     
     // MARK: Connection KVO (any queue)
@@ -150,12 +147,28 @@ class NEUDPInterface: NSObject, GenericSocket, LinkInterface {
             break
         }
     }
+}
+
+class NEUDPLinkInterface: LinkInterface {
+    private let impl: NWUDPSession
+    
+    private let maxDatagrams: Int
+    
+    init(impl: NWUDPSession, mtu: Int, maxDatagrams: Int? = nil) {
+        self.impl = impl
+        self.mtu = mtu
+        self.maxDatagrams = maxDatagrams ?? 200
+    }
 
     // MARK: LinkInterface
     
     let isReliable: Bool = false
     
-    let mtu: Int = 1000
+    var remoteAddress: String? {
+        return (impl.resolvedEndpoint as? NWHostEndpoint)?.hostname
+    }
+
+    let mtu: Int
 
     var packetBufferSize: Int {
         return maxDatagrams

TunnelKit/Sources/AppExtension/TunnelKitProvider.swift

@@ -335,10 +335,10 @@ extension TunnelKitProvider: GenericSocketDelegate {
             return
         }
         if proxy.canRebindLink() {
-            proxy.rebindLink(socket.link())
+            proxy.rebindLink(socket.link(withMTU: 1000))
             reasserting = false
         } else {
-            proxy.setLink(socket.link())
+            proxy.setLink(socket.link(withMTU: 1000))
         }
     }