Add experimental high-speed tunnel engine

Android/app/build.gradle

@@ -21,6 +21,10 @@ def goSourcePackages = ["${goSourceDir}/backend",
                         "${goSourceDir}/intra/split",
                         "${goSourceDir}/intra/protect"]
 def goBuildDir = file("${buildDir}/go")
+def goExecutableSuffix = System.getProperty('os.name').toLowerCase().contains('windows') ?
+                         '.exe' : ''
+def goMobileExecutable = file("${goBuildDir}/gomobile${goExecutableSuffix}")
+def goBindExecutable = file("${goBuildDir}/gobind${goExecutableSuffix}")
 def goBackendAAR = file("${goBuildDir}/backend.aar")
 
 // gomobile won't use the Go version in go.mod. So we need to manually read it from go.mod and
@@ -156,7 +160,7 @@ tasks.register('compileGoBackend', Exec) {
                         System.getProperty('path.separator') +
                         System.getenv('PATH')
 
-    commandLine("${goBuildDir}/gomobile", 'bind',
+    commandLine(goMobileExecutable, 'bind',
                 '-ldflags=-s -w',
                 '-target=android',
                 "-androidapi=${android.defaultConfig.minSdk}",
@@ -166,8 +170,8 @@ tasks.register('compileGoBackend', Exec) {
 
 tasks.register('ensureGoMobile', Exec) {
     // install gomobile and gobind into the build folder
-    outputs.file("${goBuildDir}/gomobile")
-    outputs.file("${goBuildDir}/gobind")
+    outputs.file(goMobileExecutable)
+    outputs.file(goBindExecutable)
 
     doFirst { goBuildDir.mkdirs() }
 

Android/app/src/go/backend/doh.go

@@ -104,16 +104,13 @@ type DoHListener interface {
 	OnResponse(DoHQueryToken, *DoHQuerySumary)
 }
 
-// DoHStatus is an integer representing the status of a DoH transaction.
-type DoHStatus = int
-
 const (
-	DoHStatusComplete      DoHStatus = doh.Complete      // Transaction completed successfully
-	DoHStatusSendFailed    DoHStatus = doh.SendFailed    // Failed to send query
-	DoHStatusHTTPError     DoHStatus = doh.HTTPError     // Got a non-200 HTTP status
-	DoHStatusBadQuery      DoHStatus = doh.BadQuery      // Malformed input
-	DoHStatusBadResponse   DoHStatus = doh.BadResponse   // Response was invalid
-	DoHStatusInternalError DoHStatus = doh.InternalError // This should never happen
+	DoHStatusComplete      = doh.Complete      // Transaction completed successfully
+	DoHStatusSendFailed    = doh.SendFailed    // Failed to send query
+	DoHStatusHTTPError     = doh.HTTPError     // Got a non-200 HTTP status
+	DoHStatusBadQuery      = doh.BadQuery      // Malformed input
+	DoHStatusBadResponse   = doh.BadResponse   // Response was invalid
+	DoHStatusInternalError = doh.InternalError // This should never happen
 )
 
 // DoHQuerySumary is the summary of a DNS transaction.
@@ -122,12 +119,12 @@ type DoHQuerySumary struct {
 	summ *doh.Summary
 }
 
-func (q DoHQuerySumary) GetQuery() []byte     { return q.summ.Query }
-func (q DoHQuerySumary) GetResponse() []byte  { return q.summ.Response }
-func (q DoHQuerySumary) GetServer() string    { return q.summ.Server }
-func (q DoHQuerySumary) GetStatus() DoHStatus { return q.summ.Status }
-func (q DoHQuerySumary) GetHTTPStatus() int   { return q.summ.HTTPStatus }
-func (q DoHQuerySumary) GetLatency() float64  { return q.summ.Latency }
+func (q DoHQuerySumary) GetQuery() []byte    { return q.summ.Query }
+func (q DoHQuerySumary) GetResponse() []byte { return q.summ.Response }
+func (q DoHQuerySumary) GetServer() string   { return q.summ.Server }
+func (q DoHQuerySumary) GetStatus() int      { return q.summ.Status }
+func (q DoHQuerySumary) GetHTTPStatus() int  { return q.summ.HTTPStatus }
+func (q DoHQuerySumary) GetLatency() float64 { return q.summ.Latency }
 
 // dohListenerAdapter is an adapter for the internal [doh.Listener].
 type dohListenerAdapter struct {

Android/app/src/go/intra/engine.go

@@ -0,0 +1,32 @@
+// Copyright 2026 Jigsaw Operations LLC
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package intra
+
+import (
+	"context"
+
+	"localhost/Intra/Android/app/src/go/logging"
+
+	"github.com/Jigsaw-Code/outline-sdk/network"
+)
+
+func newTunnelEngine(ctx context.Context, sd *intraStreamDialer, pp *intraPacketProxy) (network.IPDevice, error) {
+	if useXJasonlyuEngine {
+		logging.Debug("Intra tunnel engine selected", "engine", "xjasonlyu")
+		return newXJasonlyuEngine(ctx, sd, pp)
+	}
+	logging.Debug("Intra tunnel engine selected", "engine", "lwip")
+	return newLWIPTunnelEngine(sd, pp)
+}

Android/app/src/go/intra/engine_default.go

@@ -0,0 +1,19 @@
+// Copyright 2026 Jigsaw Operations LLC
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+//go:build !xjasonlyu_experiment
+
+package intra
+
+const useXJasonlyuEngine = false

Android/app/src/go/intra/engine_lwip.go

@@ -0,0 +1,24 @@
+// Copyright 2026 Jigsaw Operations LLC
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package intra
+
+import (
+	"github.com/Jigsaw-Code/outline-sdk/network"
+	"github.com/Jigsaw-Code/outline-sdk/network/lwip2transport"
+)
+
+func newLWIPTunnelEngine(sd *intraStreamDialer, pp *intraPacketProxy) (network.IPDevice, error) {
+	return lwip2transport.ConfigureDevice(sd, pp)
+}