added an option to build a dynamic library

fixes https://github.com/yggdrasil-network/yggstack/issues/17

build

@@ -8,8 +8,9 @@ PKGVER=${PKGVER:-$(sh contrib/semver/version.sh --bare)}
 
 LDFLAGS="-X $PKGSRC.buildName=$PKGNAME -X $PKGSRC.buildVersion=$PKGVER"
 ARGS="-v"
+DLL=false
 
-while getopts "utc:l:dro:ps" option
+while getopts "utc:l:dro:psk" option
 do
   case "$option"
   in
@@ -22,6 +23,7 @@ do
   o) ARGS="$ARGS -o $OPTARG";;
   p) ARGS="$ARGS -buildmode=pie";;
   s) ARGS="$ARGS -tags netgo,osusersgo,static" LDFLAGS="$LDFLAGS -extldflags '-static'" CGO_ENABLED=0;;
+  k) DLL=true;;
   esac
 done
 
@@ -29,11 +31,16 @@ if [ -z $TABLES ] && [ -z $DEBUG ]; then
   LDFLAGS="$LDFLAGS -s -w"
 fi
 
-for CMD in yggstack ; do
+if [ "$DLL" = true ]; then
-  echo "Building: $CMD"
+  echo "Building: shared library"
-  go build $ARGS -ldflags="$LDFLAGS" -gcflags="$GCFLAGS" ./cmd/$CMD
+  CGO_ENABLED=1 go build $ARGS -buildmode=c-shared -ldflags="$LDFLAGS" -gcflags="$GCFLAGS" -o yggstack ./pkg/yggstack
+else
+  for CMD in yggstack ; do
+    echo "Building: $CMD"
+    go build $ARGS -ldflags="$LDFLAGS" -gcflags="$GCFLAGS" ./cmd/$CMD
 
-  if [ $UPX ]; then
+    if [ $UPX ]; then
-    upx --brute $CMD
+      upx --brute $CMD
-  fi
+    fi
-done
+  done
+fi

cmd/yggstack/program.go

@@ -0,0 +1,11 @@
+package main
+
+import (
+	"os"
+
+	"github.com/yggdrasil-network/yggstack/src/driver"
+)
+
+func main() {
+	driver.Run(os.Args[1:])
+}

pkg/yggstack/lib.go

@@ -0,0 +1,28 @@
+//go:build cgo
+// +build cgo
+
+package main
+
+/*
+#include <stdlib.h>
+*/
+import "C"
+import (
+	"unsafe"
+
+	"github.com/yggdrasil-network/yggstack/src/driver"
+)
+
+func main() {}
+
+//export YggstackMain
+func YggstackMain(argc C.int, argv **C.char) {
+	length := int(argc)
+	args := make([]string, length)
+	argvPtr := unsafe.Pointer(argv)
+	for i := 0; i < length; i++ {
+		arg := *(**C.char)(unsafe.Add(argvPtr, uintptr(i)*unsafe.Sizeof((*C.char)(nil))))
+		args[i] = C.GoString(arg)
+	}
+	driver.Run(args)
+}

src/driver/driver.go

@@ -1,4 +1,4 @@
-package main
+package driver
 
 import (
 	"context"
@@ -47,8 +47,7 @@ type UDPSession struct {
 	remoteAddr net.Addr
 }
 
-// The main function is responsible for configuring and starting Yggdrasil.
+func Run(args []string) {
-func main() {
 	var localtcp types.TCPLocalMappings
 	var localudp types.UDPLocalMappings
 	var remotetcp types.TCPRemoteMappings
@@ -72,7 +71,7 @@ func main() {
 	flag.Var(&localudp, "local-udp", "UDP ports to forward to the remote Yggdrasil node, e.g. 22:[a:b:c:d]:2022, 127.0.0.1:[a:b:c:d]:22")
 	flag.Var(&remotetcp, "remote-tcp", "TCP ports to expose to the network, e.g. 22, 2022:22, 22:192.168.1.1:2022")
 	flag.Var(&remoteudp, "remote-udp", "UDP ports to expose to the network, e.g. 22, 2022:22, 22:192.168.1.1:2022")
-	flag.Parse()
+	flag.CommandLine.Parse(args)
 
 	// Catch interrupts from the operating system to exit gracefully.
 	ctx, _ := signal.NotifyContext(context.Background(), os.Interrupt, syscall.SIGTERM)