Update mobile build for iOS/macOS framework generation

contrib/mobile/mobile_apple.go

@@ -0,0 +1,40 @@
+//go:build ios || darwin
+// +build ios darwin
+
+package mobile
+
+/*
+#cgo CFLAGS: -x objective-c
+#cgo LDFLAGS: -framework Foundation
+#import <Foundation/Foundation.h>
+void Log(const char *text) {
+  NSString *nss = [NSString stringWithUTF8String:text];
+  NSLog(@"%@", nss);
+}
+*/
+import "C"
+import (
+	"unsafe"
+
+	"github.com/yggdrasil-network/yggdrasil-go/src/tun"
+)
+
+type MobileLogger struct {
+}
+
+func (nsl MobileLogger) Write(p []byte) (n int, err error) {
+	p = append(p, 0)
+	cstr := (*C.char)(unsafe.Pointer(&p[0]))
+	C.Log(cstr)
+	return len(p), nil
+}
+
+func (m *Yggdrasil) TakeOverTUN(fd int32) error {
+	options := []tun.SetupOption{
+		tun.FileDescriptor(fd),
+		tun.InterfaceMTU(m.iprwc.MTU()),
+	}
+	var err error
+	m.tun, err = tun.New(m.iprwc, m.logger, options...)
+	return err
+}