tunnel: request DHCPv6 leases

8 files changed, 477 insertions, 59 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 6afdfd95..74d1c553 100644
--- a/tunnel/src/main/java/com/wireguard/android/backend/GoBackend.java
+++ b/tunnel/src/main/java/com/wireguard/android/backend/GoBackend.java
@@ -28,7 +28,10 @@ import com.google.protobuf.Empty;
 
 import com.wireguard.android.backend.BackendException.Reason;
 import com.wireguard.android.backend.Tunnel.State;
+import com.wireguard.android.backend.gen.DhcpRequest;
+import com.wireguard.android.backend.gen.DhcpResponse;
 import com.wireguard.android.backend.gen.GetConnectionOwnerUidResponse;
+import com.wireguard.android.backend.gen.Lease;
 import com.wireguard.android.backend.gen.LibwgGrpc;
 import com.wireguard.android.backend.gen.ReverseRequest;
 import com.wireguard.android.backend.gen.ReverseResponse;
@@ -71,6 +74,7 @@ import java.net.URL;
 import java.time.Instant;
 import java.nio.ByteOrder;
 import java.util.Collections;
+import java.util.List;
 import java.util.Optional;
 import java.util.Set;
 import java.util.concurrent.CountDownLatch;
@@ -102,8 +106,10 @@ public final class GoBackend implements Backend {
     private int currentTunnelHandle = -1;
     private ConnectivityManager connectivityManager;
     private ConnectivityManager.NetworkCallback myNetworkCallback = new MyNetworkCallback();
+    private ConnectivityManager.NetworkCallback vpnNetworkCallback;
     @Nullable private Network activeNetwork;
     private ManagedChannel channel;
+    private boolean obtainDhcpLease = false;
 
     /**
      * Public constructor for GoBackend.
@@ -138,6 +144,8 @@ public final class GoBackend implements Backend {
 
     private static native int wgSetConfig(int handle, String settings);
 
+    private static native void wgSetFd(int handle, int tunFd);
+
     private static native void wgTurnOff(int handle);
 
     private static native int wgTurnOn(String ifName, int tunFd, String settings);
@@ -358,6 +366,50 @@ 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.Builder requestBuilder = DhcpRequest.newBuilder();
+        if (source != null) {
+            requestBuilder.setSource(source);
+        }
+        DhcpRequest request = requestBuilder.build();
+        DhcpResponse resp = stub.dhcp(request);
+        Log.i(TAG, "Dhcp: " + resp.getError().getMessage());
+
+        // Replace the vpn tunnel
+        final VpnService.Builder builder = getBuilder(currentTunnel.getName(), currentConfig, service, resp.getLeasesList());
+
+        Log.i(TAG, "Builder: " + builder);
+
+        try (final ParcelFileDescriptor tun = builder.establish()) {
+            if (tun == null)
+                throw new BackendException(Reason.TUN_CREATION_ERROR);
+            Log.d(TAG, "Go backend " + wgVersion());
+            // SetFd
+            wgSetFd(currentTunnelHandle, tun.detachFd());
+        }
+        if (currentTunnelHandle < 0)
+            throw new BackendException(Reason.GO_ACTIVATION_ERROR_CODE, currentTunnelHandle);
+
+        service.protect(wgGetSocketV4(currentTunnelHandle));
+        service.protect(wgGetSocketV6(currentTunnelHandle));
+        Log.i(TAG, "Dhcp done");
+    }
+
     private int getConnectionOwnerUid(int protocol, InetSocketAddress local, InetSocketAddress remote) {
         if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.Q)
             return connectivityManager.getConnectionOwnerUid(protocol, local, remote);
@@ -440,6 +492,94 @@ public final class GoBackend implements Backend {
         Log.i(TAG, "Exit streamReverse");
     }
 
+    private VpnService.Builder getBuilder(final String name, @Nullable final Config config, final VpnService service, @Nullable final List<Lease> leases) throws PackageManager.NameNotFoundException {
+        Log.i(TAG, "Builder 1");
+            final VpnService.Builder builder = service.getBuilder();
+        Log.i(TAG, "Builder 2");
+            builder.setSession(name);
+
+        Log.i(TAG, "Builder 3");
+            for (final String excludedApplication : config.getInterface().getExcludedApplications())
+                builder.addDisallowedApplication(excludedApplication);
+
+        Log.i(TAG, "Builder 4");
+            for (final String includedApplication : config.getInterface().getIncludedApplications())
+                builder.addAllowedApplication(includedApplication);
+
+        Log.i(TAG, "Builder 5");
+            if (leases != null) {
+                for (final Lease lease: leases) {
+                    try {
+                        InetAddress addr = InetAddress.getByAddress(lease.getAddress().getAddress().toByteArray());
+                        Log.i(TAG, "Lease: " + addr);
+                        builder.addAddress(addr, 128);
+                    } catch (UnknownHostException ex) {
+                        // Ignore
+                    }
+                }
+            }
+
+        Log.i(TAG, "Builder 6");
+            for (final InetNetwork addr : config.getInterface().getAddresses())
+                builder.addAddress(addr.getAddress(), addr.getMask());
+
+        Log.i(TAG, "Builder 7");
+            for (final InetAddress addr : config.getInterface().getDnsServers())
+                builder.addDnsServer(addr.getHostAddress());
+
+        Log.i(TAG, "Builder 8");
+            for (final String dnsSearchDomain : config.getInterface().getDnsSearchDomains())
+                builder.addSearchDomain(dnsSearchDomain);
+
+        Log.i(TAG, "Builder 9");
+            boolean sawDefaultRoute = false;
+            for (final Peer peer : config.getPeers()) {
+                for (final InetNetwork addr : peer.getAllowedIps()) {
+                    if (addr.getMask() == 0)
+                        sawDefaultRoute = true;
+                    builder.addRoute(addr.getAddress(), addr.getMask());
+                }
+            }
+
+        Log.i(TAG, "Builder 10");
+            // "Kill-switch" semantics
+            if (!(sawDefaultRoute && config.getPeers().size() == 1)) {
+                builder.allowFamily(OsConstants.AF_INET);
+                builder.allowFamily(OsConstants.AF_INET6);
+            }
+
+        Log.i(TAG, "Builder 11");
+            builder.setMtu(config.getInterface().getMtu().orElse(1280));
+
+        Log.i(TAG, "Builder 12");
+            if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.Q)
+                builder.setMetered(false);
+        Log.i(TAG, "Builder 13");
+            if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.M)
+                service.setUnderlyingNetworks(null);
+
+        Log.i(TAG, "Builder 14");
+            Optional<HttpProxy> proxy = config.getInterface().getHttpProxy();
+            if (proxy.isPresent()) {
+                ProxyInfo pi = proxy.get().getProxyInfo();
+                Uri pacFileUrl = pi.getPacFileUrl();
+
+                if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.Q) {
+                    if (pacFileUrl != null && pacFileUrl != Uri.EMPTY) {
+                        int listenPort = startHttpProxy(pacFileUrl);
+                        ProxyInfo localPi = ProxyInfo.buildDirectProxy("localhost", listenPort);
+                        builder.setHttpProxy(localPi);
+                    } else {
+                        builder.setHttpProxy(pi);
+                    }
+                }
+            }
+
+        Log.i(TAG, "Builder 15");
+            builder.setBlocking(true);
+            return builder;
+    }
+
     private void setStateInternal(final Tunnel tunnel, @Nullable final Config config, final State state)
             throws Exception {
         Log.i(TAG, "Bringing tunnel " + tunnel.getName() + ' ' + state);
@@ -503,63 +643,8 @@ public final class GoBackend implements Backend {
             final String goConfig = config.toWgUserspaceString(resolver);
 
             // Create the vpn tunnel with android API
-            final VpnService.Builder builder = service.getBuilder();
-            builder.setSession(tunnel.getName());
-
-            for (final String excludedApplication : config.getInterface().getExcludedApplications())
-                builder.addDisallowedApplication(excludedApplication);
-
-            for (final String includedApplication : config.getInterface().getIncludedApplications())
-                builder.addAllowedApplication(includedApplication);
-
-            for (final InetNetwork addr : config.getInterface().getAddresses())
-                builder.addAddress(addr.getAddress(), addr.getMask());
-
-            for (final InetAddress addr : config.getInterface().getDnsServers())
-                builder.addDnsServer(addr.getHostAddress());
-
-            for (final String dnsSearchDomain : config.getInterface().getDnsSearchDomains())
-                builder.addSearchDomain(dnsSearchDomain);
-
-            boolean sawDefaultRoute = false;
-            for (final Peer peer : config.getPeers()) {
-                for (final InetNetwork addr : peer.getAllowedIps()) {
-                    if (addr.getMask() == 0)
-                        sawDefaultRoute = true;
-                    builder.addRoute(addr.getAddress(), addr.getMask());
-                }
-            }
-
-            // "Kill-switch" semantics
-            if (!(sawDefaultRoute && config.getPeers().size() == 1)) {
-                builder.allowFamily(OsConstants.AF_INET);
-                builder.allowFamily(OsConstants.AF_INET6);
-            }
-
-            builder.setMtu(config.getInterface().getMtu().orElse(1280));
-
-            if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.Q)
-                builder.setMetered(false);
-            if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.M)
-                service.setUnderlyingNetworks(null);
-
-            Optional<HttpProxy> proxy = config.getInterface().getHttpProxy();
-            if (proxy.isPresent()) {
-                ProxyInfo pi = proxy.get().getProxyInfo();
-                Uri pacFileUrl = pi.getPacFileUrl();
-
-                if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.Q) {
-                    if (pacFileUrl != null && pacFileUrl != Uri.EMPTY) {
-                        int listenPort = startHttpProxy(pacFileUrl);
-                        ProxyInfo localPi = ProxyInfo.buildDirectProxy("localhost", listenPort);
-                        builder.setHttpProxy(localPi);
-                    } else {
-                        builder.setHttpProxy(pi);
-                    }
-                }
-            }
+            final VpnService.Builder builder = getBuilder(tunnel.getName(), config, service, null);
 
-            builder.setBlocking(true);
             try (final ParcelFileDescriptor tun = builder.establish()) {
                 if (tun == null)
                     throw new BackendException(Reason.TUN_CREATION_ERROR);
@@ -575,8 +660,14 @@ public final class GoBackend implements Backend {
             service.protect(wgGetSocketV4(currentTunnelHandle));
             service.protect(wgGetSocketV6(currentTunnelHandle));
 
+            obtainDhcpLease = true;
+
             NetworkRequest req = new NetworkRequest.Builder().addCapability(NetworkCapabilities.NET_CAPABILITY_NOT_VPN).build();
             connectivityManager.requestNetwork(req,  myNetworkCallback);
+
+            NetworkRequest vpnReq = new NetworkRequest.Builder().addTransportType(NetworkCapabilities.TRANSPORT_VPN).removeCapability(NetworkCapabilities.NET_CAPABILITY_NOT_VPN).build();
+            vpnNetworkCallback = new VpnNetworkCallback(service);
+            connectivityManager.requestNetwork(vpnReq, vpnNetworkCallback);
         } else {
             if (currentTunnelHandle == -1) {
                 Log.w(TAG, "Tunnel already down");
@@ -587,6 +678,9 @@ public final class GoBackend implements Backend {
             currentTunnelHandle = -1;
             currentConfig = null;
             stopHttpProxy();
+            if (vpnNetworkCallback != null)
+                connectivityManager.unregisterNetworkCallback(vpnNetworkCallback);
+            vpnNetworkCallback = null;
             connectivityManager.unregisterNetworkCallback(myNetworkCallback);
             activeNetwork = null;
             wgTurnOff(handleToClose);
@@ -658,6 +752,9 @@ public final class GoBackend implements Backend {
                 final Tunnel tunnel = owner.currentTunnel;
                 if (tunnel != null) {
                     if (owner.currentTunnelHandle != -1) {
+                        if (owner.vpnNetworkCallback != null)
+                            owner.connectivityManager.unregisterNetworkCallback(owner.vpnNetworkCallback);
+                        owner.vpnNetworkCallback = null;
                         owner.connectivityManager.unregisterNetworkCallback(owner.myNetworkCallback);
                         owner.activeNetwork = null;
                         wgTurnOff(owner.currentTunnelHandle);
@@ -688,6 +785,27 @@ public final class GoBackend implements Backend {
         }
     }
 
+    private class VpnNetworkCallback extends ConnectivityManager.NetworkCallback {
+        private VpnService service;
+        public VpnNetworkCallback(VpnService service) {
+            this.service = service;
+        }
+        @Override
+        public void onAvailable(Network network) {
+            Log.w(TAG, "VPN onAvailable: " + network);
+            if (obtainDhcpLease) {
+                Log.w(TAG, "Obtaindhcplease");
+                try {
+                    Log.w(TAG, "Before Dhcp");
+                    Dhcp(service);
+                    Log.w(TAG, "After Dhcp");
+                } catch (Exception ex) {
+                    Log.e(TAG, "DHCP failed: " + ex);
+                }
+            }
+        }
+    }
+
     private class MyNetworkCallback extends ConnectivityManager.NetworkCallback {
         @Override
         public void onAvailable(Network network) {
diff --git a/tunnel/src/main/java/com/wireguard/util/Resolver.java b/tunnel/src/main/java/com/wireguard/util/Resolver.java
index 04e6b9a8..62b11286 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);
     }
diff --git a/tunnel/src/main/proto/libwg.proto b/tunnel/src/main/proto/libwg.proto
index c87eb9ef..e0975f60 100644
--- a/tunnel/src/main/proto/libwg.proto
+++ b/tunnel/src/main/proto/libwg.proto
@@ -1,5 +1,7 @@
 syntax = "proto3";
 
+import "google/protobuf/duration.proto";
+
 option java_multiple_files = true;
 option java_package = 'com.wireguard.android.backend.gen';
 option java_outer_classname = "LibwgProto";
@@ -14,6 +16,7 @@ service Libwg {
 	rpc StartHttpProxy(StartHttpProxyRequest) returns (StartHttpProxyResponse);
 	rpc StopHttpProxy(StopHttpProxyRequest) returns (StopHttpProxyResponse);
 	rpc Reverse(stream ReverseRequest) returns (stream ReverseResponse);
+	rpc Dhcp(DhcpRequest) returns (DhcpResponse);
 }
 
 message Error {
@@ -92,3 +95,19 @@ message GetConnectionOwnerUidResponse {
 	int32 uid = 1;
 	string package = 2; // context.getPackageManager().getNameForUid()
 }
+
+message Lease {
+        InetAddress address = 1;
+        google.protobuf.Duration preferred_lifetime = 2;
+        google.protobuf.Duration valid_lifetime = 3;
+}
+
+message DhcpRequest {
+        InetAddress relay = 1;
+        InetAddress source = 2;
+}
+
+message DhcpResponse { 
+       Error error = 1;
+       repeated Lease leases = 2;
+}
diff --git a/tunnel/tools/libwg-go/Makefile b/tunnel/tools/libwg-go/Makefile
index 9bec6fdc..5ae4548d 100644
--- a/tunnel/tools/libwg-go/Makefile
+++ b/tunnel/tools/libwg-go/Makefile
@@ -71,7 +71,7 @@ gen/%_grpc.pb.go: $(PROTODIR)/%.proto $(BUILDDIR)/go-$(GO_VERSION)/.prepared $(P
 	$(PROTOC) -I $(PROTODIR) -I $(PROTO_INCLUDEDIR) --go-grpc_out=./gen --go-grpc_opt=paths=source_relative $<
 
 $(DESTDIR)/libwg-go.so: export PATH := $(BUILDDIR)/go-$(GO_VERSION)/bin/:$(PATH)
-$(DESTDIR)/libwg-go.so: $(BUILDDIR)/go-$(GO_VERSION)/.prepared go.mod api-android.go http-proxy.go service.go gen/libwg.pb.go gen/libwg_grpc.pb.go jni.c
+$(DESTDIR)/libwg-go.so: $(BUILDDIR)/go-$(GO_VERSION)/.prepared go.mod api-android.go dhcp.go http-proxy.go service.go gen/libwg.pb.go gen/libwg_grpc.pb.go jni.c
 	go build -tags linux -ldflags="-X golang.zx2c4.com/wireguard/ipc.socketDirectory=/data/data/$(ANDROID_PACKAGE_NAME)/cache/wireguard -buildid=" -v -trimpath -buildvcs=false -o "$@" -buildmode c-shared
 
 .DELETE_ON_ERROR:
diff --git a/tunnel/tools/libwg-go/api-android.go b/tunnel/tools/libwg-go/api-android.go
index 484a89b0..943ba628 100644
--- a/tunnel/tools/libwg-go/api-android.go
+++ b/tunnel/tools/libwg-go/api-android.go
@@ -49,6 +49,7 @@ type TunnelHandle struct {
 	device *device.Device
 	uapi   net.Listener
 	logger *device.Logger
+	tun *tun.NativeTun
 }
 
 var tunnelHandles map[int32]TunnelHandle
@@ -143,10 +144,29 @@ func wgTurnOn(interfaceName string, tunFd int32, settings string) int32 {
 		device.Close()
 		return -1
 	}
-	tunnelHandles[i] = TunnelHandle{device: device, uapi: uapi}
+	tunnelHandles[i] = TunnelHandle{device: device, uapi: uapi, tun: tun}
 	return i
 }
 
+//export wgSetFd
+func wgSetFd(tunnelHandle int32, tunFd int32) {
+        tag := cstring(fmt.Sprintf("WireGuard/GoBackend/%x", tunnelHandle))
+        logger := &device.Logger{
+                Verbosef: AndroidLogger{level: C.ANDROID_LOG_DEBUG, tag: tag}.Printf,
+                Errorf:   AndroidLogger{level: C.ANDROID_LOG_ERROR, tag: tag}.Printf,
+        }
+
+        handle, ok := tunnelHandles[tunnelHandle]
+        if !ok {
+		unix.Close(int(tunFd))
+		logger.Errorf("Tunnel not found")
+                return
+        }
+
+	handle.tun.SetFd(int(tunFd))
+        logger.Verbosef("wgSetFd: %v", tunFd)
+}
+
 //export wgTurnOff
 func wgTurnOff(tunnelHandle int32) {
 	handle, ok := tunnelHandles[tunnelHandle]
diff --git a/tunnel/tools/libwg-go/dhcp.go b/tunnel/tools/libwg-go/dhcp.go
new file mode 100644
index 00000000..b7919151
--- /dev/null
+++ b/tunnel/tools/libwg-go/dhcp.go
@@ -0,0 +1,192 @@
+package main
+
+import (
+        "context"
+        "net"
+        "net/netip"
+        "time"
+
+        "github.com/insomniacslk/dhcp/dhcpv4"
+        "github.com/insomniacslk/dhcp/dhcpv6"
+        "github.com/insomniacslk/dhcp/dhcpv6/nclient6"
+        "github.com/insomniacslk/dhcp/iana"
+
+	gen "golang.zx2c4.com/wireguard/android/gen"
+)
+
+const (
+        ENABLE_PD = true
+)
+
+type dhcp struct {
+        fqdn string
+        hwAddr net.HardwareAddr
+        conn *net.UDPConn
+        serverAddr net.UDPAddr
+        client *nclient6.Client
+        linkAddr net.IP
+        peerAddr net.IP
+}
+
+func newClientIDOpt(duid dhcpv6.DUID) dhcpv4.Option {
+	iaid := []byte{0, 0, 0, 3}
+	ident := []byte{255}                     // Type IAID+DUID
+	ident = append(ident, iaid...)           // IAID
+	ident = append(ident, duid.ToBytes()...) // DUID
+	return dhcpv4.OptClientIdentifier(ident)
+}
+
+func getDuid(hwAddr net.HardwareAddr) dhcpv6.DUID {
+	duid := &dhcpv6.DUIDLLT{
+		HWType:        iana.HWTypeEthernet,
+		Time:          uint32(time.Now().Unix()),
+		LinkLayerAddr: hwAddr,
+	}
+
+        return duid
+}
+
+func (d *dhcp) encapSendAndRead(ctx context.Context, msg *dhcpv6.Message, match nclient6.Matcher) (*dhcpv6.Message, error) {
+	packet, err := dhcpv6.EncapsulateRelay(msg, dhcpv6.MessageTypeRelayForward, d.linkAddr, d.peerAddr)
+	if err != nil {
+		return nil, err
+	}
+
+        relay, err := d.client.SendAndReadRelay(ctx, &d.serverAddr, packet, match)
+	if err != nil {
+		return nil, err
+	}
+
+        inner, err := relay.GetInnerMessage()
+        if err != nil {
+                return nil, err
+        }
+
+        return inner, nil
+}
+
+// isRelayMessageType returns a matcher that checks for the message type.
+func isRelayMessageType(t dhcpv6.MessageType, tt ...dhcpv6.MessageType) nclient6.Matcher {
+	return func(p dhcpv6.DHCPv6) bool {
+                inner, err := p.GetInnerMessage()
+                if err != nil {
+                        return false
+                }
+		if inner.Type() == t {
+			return true
+		}
+		for _, mt := range tt {
+			if inner.Type() == mt {
+				return true
+			}
+		}
+		return false
+	}
+}
+
+// func New() *dhcp {
+// }
+
+func RunDhcp(ctx context.Context, laddr, raddr netip.Addr) ([]*gen.Lease, error) {
+        d := &dhcp{}
+        
+        d.linkAddr = net.ParseIP("fe80::101")
+	d.peerAddr = net.ParseIP("::1")
+
+        // TODO generate hostname and hwAddr from public key
+	hostName := "foobar"
+	d.fqdn = hostName + ".m7n.se"
+        d.hwAddr = []byte{41, 42, 43, 44, 45, 46}
+
+
+        src := net.UDPAddr{IP: laddr.AsSlice(),
+                Port: 0,        // Use non-restrict UDP source port
+        }
+
+
+        d.serverAddr = net.UDPAddr{IP: raddr.AsSlice(),
+                Port: 547,
+        }
+
+        err := d.Start(&src)
+        if err != nil {
+                return nil, err
+        }
+
+        defer d.Close()
+
+        reply, err := d.ObtainLease(ctx) // Use reply
+        if err != nil {
+                return nil, err
+        }
+
+        return getAddressesFromReply(reply), nil
+}
+
+func getAddressesFromReply(reply *dhcpv6.Message) []*gen.Lease{
+        var leases []*gen.Lease = make([]*gen.Lease, 0, 4)
+
+        if opt := reply.GetOneOption(dhcpv6.OptionIANA); opt != nil {
+                iana := opt.(*dhcpv6.OptIANA)
+                ianaOpts := iana.Options.Get(dhcpv6.OptionIAAddr)
+
+                for _, opt := range ianaOpts {
+                        addr :=opt.(*dhcpv6.OptIAAddress).IPv6Addr
+                        lease := &gen.Lease{
+                                Address: &gen.InetAddress{
+                                        Address: addr,
+                                },
+                                // PreferredLifetime: ,
+                                // ValidLifetime: ,
+                        }
+                        leases = append(leases, lease)
+                }
+        }
+
+        return leases
+}
+
+func (d *dhcp) Start(localAddr *net.UDPAddr) error {
+        conn, err := net.ListenUDP("udp6", localAddr)
+	if err != nil {
+                return err
+        }
+        
+	d.client, err = nclient6.NewWithConn(conn, d.hwAddr, nclient6.WithDebugLogger())
+	return err
+}
+
+func (d *dhcp) Close() error {
+        err := d.client.Close()
+
+        d.client = nil
+        return err
+}
+
+func (d *dhcp) ObtainLease(ctx context.Context) (*dhcpv6.Message, error){
+        duidOpt := dhcpv6.WithClientID(getDuid(d.hwAddr))
+	fqdnOpt := dhcpv6.WithFQDN(0x1, d.fqdn)
+
+        solicit, err := dhcpv6.NewSolicit(d.hwAddr, duidOpt, fqdnOpt, dhcpv6.WithRapidCommit)
+        if err != nil {
+                return nil, err
+        }
+
+        msg, err := d.encapSendAndRead(ctx, solicit, isRelayMessageType(dhcpv6.MessageTypeReply, dhcpv6.MessageTypeAdvertise))
+        if err != nil {
+                return nil, err
+        }
+
+        if msg.Type() == dhcpv6.MessageTypeReply {
+		// We got RapidCommitted.
+		return msg, nil
+        }
+
+        // We didn't get RapidCommitted. Request regular lease.
+        req, err := dhcpv6.NewRequestFromAdvertise(msg, fqdnOpt)
+        if err != nil {
+                return nil, err
+        }
+
+        return d.encapSendAndRead(ctx, req, nil)
+}
diff --git a/tunnel/tools/libwg-go/jni.c b/tunnel/tools/libwg-go/jni.c
index b386579c..443848e8 100644
--- a/tunnel/tools/libwg-go/jni.c
+++ b/tunnel/tools/libwg-go/jni.c
@@ -16,6 +16,7 @@ extern char *wgGetConfig(int handle);
 extern char *wgVersion();
 extern int wgSetConfig(int handle, struct go_string settings);
 extern int wgStartGrpc();
+extern int wgSetFd(int handle, int tun_fd);
 
 JNIEXPORT jint JNICALL Java_com_wireguard_android_backend_GoBackend_wgTurnOn(JNIEnv *env, jclass c, jstring ifname, jint tun_fd, jstring settings)
 {
@@ -95,3 +96,8 @@ JNIEXPORT jint JNICALL Java_com_wireguard_android_backend_GoBackend_wgStartGrpc(
 	(*env)->ReleaseStringUTFChars(env, sockname, sockname_str);
 	return res;
 }
+
+JNIEXPORT void JNICALL Java_com_wireguard_android_backend_GoBackend_wgSetFd(JNIEnv *env, jclass c, jint handle, jint tun_fd)
+{
+	wgSetFd(handle, tun_fd);
+}
diff --git a/tunnel/tools/libwg-go/service.go b/tunnel/tools/libwg-go/service.go
index 72916a8e..30fe650b 100644
--- a/tunnel/tools/libwg-go/service.go
+++ b/tunnel/tools/libwg-go/service.go
@@ -5,6 +5,7 @@ import (
 	"fmt"
 	"io"
 	"net"
+	"net/netip"
 	"net/url"
 	"os"
 
@@ -224,3 +225,65 @@ func (e *LibwgServiceImpl) Reverse(stream gen.Libwg_ReverseServer) error {
 	e.logger.Verbosef("Reverse returns")
 	return nil
 }
+
+func (e *LibwgServiceImpl) Dhcp(ctx context.Context, req *gen.DhcpRequest) (*gen.DhcpResponse, error) {
+	var relayAddr netip.Addr
+	var sourceAddr netip.Addr
+
+	source := req.GetSource()
+	if source != nil {
+		sourceAddr, _ = netip.AddrFromSlice(source.GetAddress())
+	}
+
+	if !sourceAddr.IsValid() || !sourceAddr.Is6() {
+		r := &gen.DhcpResponse{
+			Error: &gen.Error{
+				Message: fmt.Sprintf("DHCPv6 source address missing"),
+			},
+		}
+		return r, nil
+	}
+
+	relay := req.GetRelay()
+	if relay != nil {
+		relayAddr, _ = netip.AddrFromSlice(relay.GetAddress())
+	} else {
+		// Construct relay address from source prefix
+		relayRaw := source.GetAddress()[:8]
+		relayRaw = append(relayRaw, 0)
+		relayRaw = append(relayRaw, 0)
+		relayRaw = append(relayRaw, 0)
+		relayRaw = append(relayRaw, 0)
+		relayRaw = append(relayRaw, 0)
+		relayRaw = append(relayRaw, 0)
+		relayRaw = append(relayRaw, 0)
+		relayRaw = append(relayRaw, 1)
+		relayAddr, _ = netip.AddrFromSlice(relayRaw)
+	}
+
+	if !relayAddr.IsValid() || !relayAddr.Is6() {
+		r := &gen.DhcpResponse{
+			Error: &gen.Error{
+				Message: fmt.Sprintf("DHCPv6 relay address calculation failed"),
+			},
+		}
+		return r, nil
+	}
+
+	e.logger.Verbosef("RunDhcp %v %v", sourceAddr, relayAddr)
+
+	leases, err := RunDhcp(ctx, sourceAddr, relayAddr)
+	if err != nil {
+		r := &gen.DhcpResponse{
+			Error: &gen.Error{
+				Message: fmt.Sprintf("RunDhcp failed: %v", err),
+			},
+		}
+		return r, nil
+	}
+
+	r := &gen.DhcpResponse{
+		Leases: leases,
+	}
+	return r, nil
+}