VPN: Bring up the tunnel

The app figures out all settings and passes them in the
'options' parameter of startTunnel().

The network extension just takes them as is and just plugs the supplied
values into the right places.

Signed-off-by: Roopesh Chander <roop@roopc.net>

WireGuard/Shared/PacketTunnelOptionKey.swift

@@ -0,0 +1,30 @@
+// SPDX-License-Identifier: MIT
+// Copyright © 2018 WireGuard LLC. All rights reserved.
+
+import Foundation
+
+enum PacketTunnelOptionKey: String {
+
+    case interfaceName, wireguardSettings, remoteAddress, dnsServers, mtu,
+
+    // IPv4 settings
+    ipv4Addresses, ipv4SubnetMasks,
+    ipv4IncludedRouteAddresses, ipv4IncludedRouteSubnetMasks,
+    ipv4ExcludedRouteAddresses, ipv4ExcludedRouteSubnetMasks,
+
+    // IPv6 settings
+    ipv6Addresses, ipv6NetworkPrefixLengths,
+    ipv6IncludedRouteAddresses, ipv6IncludedRouteNetworkPrefixLengths,
+    ipv6ExcludedRouteAddresses, ipv6ExcludedRouteNetworkPrefixLengths
+}
+
+extension Dictionary where Key == String {
+    subscript(key: PacketTunnelOptionKey) -> Value? {
+        get {
+            return self[key.rawValue]
+        }
+        set(value) {
+            self[key.rawValue] = value
+        }
+    }
+}