Default to unspecified MTU

Hardcode control channel packets to 1000 bytes.

TunnelKit/Sources/AppExtension/LinkProducer.swift

@@ -30,8 +30,6 @@ public protocol LinkProducer {
 
     /**
      Returns a `LinkInterface`.
- 
-     - Parameter mtu: The MTU value.
      **/
-    func link(withMTU mtu: Int) -> LinkInterface
+    func link() -> LinkInterface
 }

TunnelKit/Sources/Core/LinkInterface.swift

@@ -45,9 +45,6 @@ public protocol LinkInterface: IOInterface {
     /// The literal address of the remote host.
     var remoteAddress: String? { get }
 
-    /// The maximum size of a packet.
-    var mtu: Int { get }
-    
     /// The number of packets that this interface is able to bufferize.
     var packetBufferSize: Int { get }
 }

TunnelKit/Sources/Protocols/OpenVPN/AppExtension/NETCPLink.swift

@@ -32,9 +32,8 @@ class NETCPLink: LinkInterface {
     
     private let maxPacketSize: Int
     
-    init(impl: NWTCPConnection, mtu: Int, maxPacketSize: Int? = nil) {
+    init(impl: NWTCPConnection, maxPacketSize: Int? = nil) {
         self.impl = impl
-        self.mtu = mtu
         self.maxPacketSize = maxPacketSize ?? (512 * 1024)
     }
     
@@ -46,8 +45,6 @@ class NETCPLink: LinkInterface {
         return (impl.remoteAddress as? NWHostEndpoint)?.hostname
     }
     
-    let mtu: Int
-    
     var packetBufferSize: Int {
         return maxPacketSize
     }
@@ -98,7 +95,7 @@ class NETCPLink: LinkInterface {
 
 /// :nodoc:
 extension NETCPSocket: LinkProducer {
-    public func link(withMTU mtu: Int) -> LinkInterface {
-        return NETCPLink(impl: impl, mtu: mtu)
+    public func link() -> LinkInterface {
+        return NETCPLink(impl: impl)
     }
 }

TunnelKit/Sources/Protocols/OpenVPN/AppExtension/NEUDPLink.swift

@@ -31,9 +31,8 @@ class NEUDPLink: LinkInterface {
     
     private let maxDatagrams: Int
     
-    init(impl: NWUDPSession, mtu: Int, maxDatagrams: Int? = nil) {
+    init(impl: NWUDPSession, maxDatagrams: Int? = nil) {
         self.impl = impl
-        self.mtu = mtu
         self.maxDatagrams = maxDatagrams ?? 200
     }
     
@@ -45,8 +44,6 @@ class NEUDPLink: LinkInterface {
         return (impl.resolvedEndpoint as? NWHostEndpoint)?.hostname
     }
     
-    let mtu: Int
-    
     var packetBufferSize: Int {
         return maxDatagrams
     }
@@ -79,7 +76,7 @@ class NEUDPLink: LinkInterface {
 
 /// :nodoc:
 extension NEUDPSocket: LinkProducer {
-    public func link(withMTU mtu: Int) -> LinkInterface {
-        return NEUDPLink(impl: impl, mtu: mtu)
+    public func link() -> LinkInterface {
+        return NEUDPLink(impl: impl)
     }
 }

TunnelKit/Sources/Protocols/OpenVPN/AppExtension/OpenVPNTunnelProvider+Configuration.swift

@@ -725,6 +725,10 @@ private extension OpenVPN.Configuration {
         if let proxyBypassDomains = proxyBypassDomains {
             log.info("\tProxy bypass domains: \(proxyBypassDomains.maskedDescription)")
         }
-        log.info("\tMTU: \(fallbackMTU)")
+        if let mtu = mtu {
+            log.info("\tMTU: \(mtu)")
+        } else {
+            log.info("\tMTU: default")
+        }
     }
 }

TunnelKit/Sources/Protocols/OpenVPN/AppExtension/OpenVPNTunnelProvider.swift

@@ -451,10 +451,10 @@ extension OpenVPNTunnelProvider: GenericSocketDelegate {
             return
         }
         if session.canRebindLink() {
-            session.rebindLink(producer.link(withMTU: cfg.sessionConfiguration.fallbackMTU))
+            session.rebindLink(producer.link())
             reasserting = false
         } else {
-            session.setLink(producer.link(withMTU: cfg.sessionConfiguration.fallbackMTU))
+            session.setLink(producer.link())
         }
     }
     
@@ -788,7 +788,9 @@ extension OpenVPNTunnelProvider: OpenVPNSessionDelegate {
         newSettings.ipv6Settings = ipv6Settings
         newSettings.dnsSettings = dnsSettings
         newSettings.proxySettings = proxySettings
-        newSettings.mtu = NSNumber(value: cfg.sessionConfiguration.fallbackMTU)
+        if let mtu = cfg.sessionConfiguration.mtu {
+            newSettings.mtu = NSNumber(value: mtu)
+        }
 
         setTunnelNetworkSettings(newSettings, completionHandler: completionHandler)
     }

TunnelKit/Sources/Protocols/OpenVPN/Configuration.swift

@@ -165,8 +165,6 @@ extension OpenVPN {
         static let digest: Digest = .sha1
         
         static let compressionFraming: CompressionFraming = .disabled
-        
-        static let mtu = 1250
     }
     
     /// The way to create a `Configuration` object for a `OpenVPNSession`.
@@ -460,11 +458,6 @@ extension OpenVPN {
         public var fallbackCompressionFraming: CompressionFraming {
             return compressionFraming ?? Fallback.compressionFraming
         }
-        
-        /// :nodoc:
-        public var fallbackMTU: Int {
-            return mtu ?? Fallback.mtu
-        }
     }
 }
 

TunnelKit/Sources/Protocols/OpenVPN/OpenVPNSession.swift

@@ -1015,12 +1015,12 @@ public class OpenVPNSession: Session {
     
     // Ruby: q_ctrl
     private func enqueueControlPackets(code: PacketCode, key: UInt8, payload: Data) {
-        guard let link = link else {
+        guard let _ = link else {
             log.warning("Not writing to LINK, interface is down")
             return
         }
 
-        controlChannel.enqueueOutboundPackets(withCode: code, key: key, payload: payload, maxPacketSize: link.mtu)
+        controlChannel.enqueueOutboundPackets(withCode: code, key: key, payload: payload, maxPacketSize: 1000)
         flushControlQueue()
     }