WIP: use first ULA address as DHCPv6 source address

2 files changed, 14 insertions, 2 deletions

diff --git a/tunnel/src/main/java/com/wireguard/android/backend/GoBackend.java b/tunnel/src/main/java/com/wireguard/android/backend/GoBackend.java
index 32e3572a..1d900db0 100644
--- a/tunnel/src/main/java/com/wireguard/android/backend/GoBackend.java
+++ b/tunnel/src/main/java/com/wireguard/android/backend/GoBackend.java
@@ -384,8 +384,20 @@ public final class GoBackend implements Backend {
     private void Dhcp(VpnService service) throws Exception{
         obtainDhcpLease = false;
 
+        // Heuristics: Use first ULA address as client address
+        com.wireguard.android.backend.gen.InetAddress source = null;
+
+        for (final InetNetwork net : currentConfig.getInterface().getAddresses()) {
+            InetAddress addr = net.getAddress();
+            if (addr instanceof Inet6Address) {
+                if (Resolver.isULA((Inet6Address)addr)) {
+                    source = com.wireguard.android.backend.gen.InetAddress.newBuilder().setAddress(ByteString.copyFrom(addr.getAddress())).build();
+                }
+            }
+        }
+
         LibwgGrpc.LibwgBlockingStub stub = LibwgGrpc.newBlockingStub(channel);
-        DhcpRequest request = DhcpRequest.newBuilder().build();
+        DhcpRequest request = DhcpRequest.newBuilder().setSource(source).build();
         DhcpResponse resp = stub.dhcp(request);
         Log.i(TAG, "Dhcp: " + resp.getError().getMessage());
 
diff --git a/tunnel/src/main/java/com/wireguard/util/Resolver.java b/tunnel/src/main/java/com/wireguard/util/Resolver.java
index f401b584..301e03e0 100644
--- a/tunnel/src/main/java/com/wireguard/util/Resolver.java
+++ b/tunnel/src/main/java/com/wireguard/util/Resolver.java
@@ -36,7 +36,7 @@ public class Resolver {
         }
     }
 
-    static boolean isULA(Inet6Address addr) {
+    public static boolean isULA(Inet6Address addr) {
         byte[] raw = addr.getAddress();
         return ((raw[0] & 0xfe) == 0xfc);
     }