Make hostname optional in ConnectionStrategy

Assume preferring resolved addresses.

CHANGELOG.md

@@ -5,6 +5,12 @@ All notable changes to this project will be documented in this file.
 The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/),
 and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0.html).
 
+## Unreleased
+
+### Changed
+
+- Make `hostname` optional and pick `resolvedAddresses` if nil.
+
 ## 1.6.1 (2019-04-07)
 
 ### Fixed

TunnelKit/Sources/AppExtension/ConnectionStrategy.swift

@@ -42,7 +42,7 @@ import SwiftyBeaver
 private let log = SwiftyBeaver.self
 
 class ConnectionStrategy {
-    private let hostname: String
+    private let hostname: String?
 
     private let prefersResolvedAddresses: Bool
 
@@ -52,15 +52,17 @@ class ConnectionStrategy {
     
     private var currentProtocolIndex = 0
 
-    init(hostname: String, configuration: TunnelKitProvider.Configuration) {
+    init(configuration: TunnelKitProvider.Configuration) {
-        precondition(!configuration.prefersResolvedAddresses || !(configuration.resolvedAddresses?.isEmpty ?? true))
+        hostname = configuration.sessionConfiguration.hostname
-        
+        prefersResolvedAddresses = (hostname == nil) || configuration.prefersResolvedAddresses
-        self.hostname = hostname
-        prefersResolvedAddresses = configuration.prefersResolvedAddresses
         resolvedAddresses = configuration.resolvedAddresses
-
+        if prefersResolvedAddresses {
+            guard !(resolvedAddresses?.isEmpty ?? true) else {
+                fatalError("Either hostname or resolved addresses provided")
+            }
+        }
         guard var endpointProtocols = configuration.sessionConfiguration.endpointProtocols else {
-            fatalError("No endpoints defined")
+            fatalError("No endpoints provided")
         }
         if configuration.sessionConfiguration.randomizeEndpoint ?? false {
             endpointProtocols.shuffle()
@@ -92,6 +94,11 @@ class ConnectionStrategy {
         }
         
         // fall back to DNS
+        guard let hostname = hostname else {
+            log.error("DNS resolution unavailable: no hostname provided!")
+            completionHandler(nil, TunnelKitProvider.ProviderError.dnsFailure)
+            return
+        }
         log.debug("DNS resolve hostname: \(hostname.maskedDescription)")
         DNSResolver.resolve(hostname, timeout: timeout, queue: queue) { (addresses, error) in
             

TunnelKit/Sources/AppExtension/TunnelKitProvider+Configuration.swift

@@ -466,7 +466,7 @@ extension TunnelKitProvider {
          - Returns: The generated `NETunnelProviderProtocol` object.
          - Throws: `ProviderError.credentials` if unable to store `credentials.password` to the `appGroup` keychain.
          */
-        public func generatedTunnelProtocol(withBundleIdentifier bundleIdentifier: String, appGroup: String, hostname: String, credentials: SessionProxy.Credentials? = nil) throws -> NETunnelProviderProtocol {
+        public func generatedTunnelProtocol(withBundleIdentifier bundleIdentifier: String, appGroup: String, hostname: String?, credentials: SessionProxy.Credentials? = nil) throws -> NETunnelProviderProtocol {
             let protocolConfiguration = NETunnelProviderProtocol()
             
             protocolConfiguration.providerBundleIdentifier = bundleIdentifier

TunnelKit/Sources/AppExtension/TunnelKitProvider.swift

@@ -123,7 +123,6 @@ open class TunnelKitProvider: NEPacketTunnelProvider {
     open override func startTunnel(options: [String : NSObject]? = nil, completionHandler: @escaping (Error?) -> Void) {
 
         // required configuration
-        let hostname: String
         do {
             guard let tunnelProtocol = protocolConfiguration as? NETunnelProviderProtocol else {
                 throw ProviderConfigurationError.parameter(name: "protocolConfiguration")
@@ -134,9 +133,17 @@ open class TunnelKitProvider: NEPacketTunnelProvider {
             guard let providerConfiguration = tunnelProtocol.providerConfiguration else {
                 throw ProviderConfigurationError.parameter(name: "protocolConfiguration.providerConfiguration")
             }
-            hostname = serverAddress
             try appGroup = Configuration.appGroup(from: providerConfiguration)
             try cfg = Configuration.parsed(from: providerConfiguration)
+            
+            // inject serverAddress into sessionConfiguration.hostname
+            if !serverAddress.isEmpty {
+                var sessionBuilder = cfg.sessionConfiguration.builder()
+                sessionBuilder.hostname = serverAddress
+                var cfgBuilder = cfg.builder()
+                cfgBuilder.sessionConfiguration = sessionBuilder.build()
+                cfg = cfgBuilder.build()
+            }
         } catch let e {
             var message: String?
             if let te = e as? ProviderConfigurationError {
@@ -162,7 +169,7 @@ open class TunnelKitProvider: NEPacketTunnelProvider {
             credentials = nil
         }
 
-        strategy = ConnectionStrategy(hostname: hostname, configuration: cfg)
+        strategy = ConnectionStrategy(configuration: cfg)
 
         if let content = cfg.existingLog(in: appGroup) {
             var existingLog = content.components(separatedBy: "\n")