feat(outline/electron): ✨ expose checkConnectivity as a library function

Author: jyyi1

.gitignore

@@ -1,5 +1,6 @@
 /build
 /bin
+/_obj
 intra/split/example/example
 
 # General

Makefile

@@ -42,23 +42,33 @@ ELECTRON_PATH=$(IMPORT_PATH)/outline/electron
 
 LINUX_BUILDDIR=$(BUILDDIR)/linux
 
-linux: $(LINUX_BUILDDIR)/tun2socks
+linux: $(LINUX_BUILDDIR)/tun2socks $(LINUX_BUILDDIR)/libtun2socks.so
 
 $(LINUX_BUILDDIR)/tun2socks: $(XGO)
 	mkdir -p "$(LINUX_BUILDDIR)"
 	$(XGO) -ldflags $(XGO_LDFLAGS) --targets=linux/amd64 -dest "$(LINUX_BUILDDIR)" "$(ELECTRON_PATH)"
 	mv "$(LINUX_BUILDDIR)/electron-linux-amd64" "$@"
 
+$(LINUX_BUILDDIR)/libtun2socks.so: $(XGO)
+	mkdir -p "$(LINUX_BUILDDIR)"
+	$(XGO) -buildmode c-shared -ldflags $(XGO_LDFLAGS) --targets=linux/amd64 -dest "$(LINUX_BUILDDIR)" "$(ELECTRON_PATH)"
+	mv "$(LINUX_BUILDDIR)/electron-linux-amd64.so" "$@"
+
 
 WINDOWS_BUILDDIR=$(BUILDDIR)/windows
 
-windows: $(WINDOWS_BUILDDIR)/tun2socks.exe
+windows: $(WINDOWS_BUILDDIR)/tun2socks.exe $(WINDOWS_BUILDDIR)/tun2socks.dll
 
 $(WINDOWS_BUILDDIR)/tun2socks.exe: $(XGO)
 	mkdir -p "$(WINDOWS_BUILDDIR)"
 	$(XGO) -ldflags $(XGO_LDFLAGS) --targets=windows/386 -dest "$(WINDOWS_BUILDDIR)" "$(ELECTRON_PATH)"
 	mv "$(WINDOWS_BUILDDIR)/electron-windows-386.exe" "$@"
 
+$(WINDOWS_BUILDDIR)/tun2socks.dll: $(XGO)
+	mkdir -p "$(WINDOWS_BUILDDIR)"
+	$(XGO) -buildmode c-shared -ldflags $(XGO_LDFLAGS) --targets=windows/386 -dest "$(WINDOWS_BUILDDIR)" "$(ELECTRON_PATH)"
+	mv "$(WINDOWS_BUILDDIR)/electron-windows-386.dll" "$@"
+
 
 $(GOMOBILE): go.mod
 	env GOBIN="$(GOBIN)" go install golang.org/x/mobile/cmd/gomobile

outline/electron/libtun2socks.go

@@ -0,0 +1,63 @@
+// Copyright 2023 The Outline Authors
+//
+// 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.
+
+// Use the following command line to generate a C header file:
+//   go tool cgo -exportheader ./build/libtun2socks.h ./outline/electron/lib.go
+
+package main
+
+/*
+#include <stdint.h> // for uint32_t
+*/
+import "C"
+
+import (
+	"runtime/cgo"
+	"unsafe"
+
+	oss "github.com/Jigsaw-Code/outline-go-tun2socks/outline/shadowsocks"
+)
+
+// Function returns a tuple [status, pErr]. If pErr is nil (means no errors),
+// status is one of the following:
+//   - 0 (NoError): can connect by TCP and UDP
+//   - 4 (UDPConnectivity): can only connect by TCP (UDP failed)
+//   - 3 (AuthenticationFailure): wrong server credentials
+//   - 5 (Unreachable): server is not reachable at all
+//
+// Otherwise if pErr is not nil, it means there are unexpected errors (status
+// will be 1 (Unexpected)).
+//
+// The caller must call ReleaseError(pErr) later to make sure Go will garbage
+// collect the error object, otherwise memory leak will happen.
+//
+//export CheckConnectivity
+func CheckConnectivity() (status C.uint32_t, pErr unsafe.Pointer) {
+	status = oss.Unexpected
+	pErr = nil
+	return
+}
+
+// If pErr points to an existing error object, this function will return pErr
+// object to Go's garbage collector. If pErr is nil, we will do nothing.
+//
+// In either case, the caller should not use pErr object any more.
+//
+//export ReleaseError
+func ReleaseError(pErr unsafe.Pointer) {
+	p := (*cgo.Handle)(pErr)
+	if p != nil {
+		(*p).Delete()
+	}
+}