Use message to extension to obtain version info.

Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>

Shared/ExtensionMessage.swift

@@ -0,0 +1,25 @@
+//
+//  Copyright © 2018 WireGuard LLC. All rights reserved.
+//
+
+import Foundation
+
+public class ExtensionMessage: Equatable {
+
+    public static let requestVersion = ExtensionMessage(0xff)
+
+    public let data: Data
+
+    private init(_ byte: UInt8) {
+        data = Data(bytes: [byte])
+    }
+
+    init(_ data: Data) {
+        self.data = data
+    }
+
+    // MARK: Equatable
+    public static func ==(lhs: ExtensionMessage, rhs: ExtensionMessage) -> Bool {
+        return (lhs.data == rhs.data)
+    }
+}