Determine MTU automatically

Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>

2 files changed, 12 insertions, 6 deletions

diff --git a/app/tools/libwg-go/api-android.go b/app/tools/libwg-go/api-android.go
index 08367b9c..6b864bce 100644
--- a/app/tools/libwg-go/api-android.go
+++ b/app/tools/libwg-go/api-android.go
@@ -30,7 +30,7 @@ func init() {
 }
 
 //export wgTurnOn
-func wgTurnOn(ifnameRef string, tun_fd int32, mtu int32, settings string) int32 {
+func wgTurnOn(ifnameRef string, tun_fd int32, settings string) int32 {
 	interfaceName := string([]byte(ifnameRef))
 
 	logger := &Logger{
@@ -47,13 +47,19 @@ func wgTurnOn(ifnameRef string, tun_fd int32, mtu int32, settings string) int32
 		errors: make(chan error, 5),
 		nopi:   true,
 	}
+	name, err := tun.Name()
+	if err != nil {
+	    logger.Error.Println(err)
+	    return -1
+	}
+	logger.Info.Println("Attaching to interface", name)
 	device := NewDevice(tun, logger)
-	device.tun.mtu = mtu
+	logger.Debug.Println("Interface has MTU", device.tun.mtu)
 
 	bufferedSettings := bufio.NewReadWriter(bufio.NewReader(strings.NewReader(settings)), bufio.NewWriter(ioutil.Discard))
 	setError := ipcSetOperation(device, bufferedSettings)
 	if setError != nil {
-		logger.Debug.Println(setError)
+		logger.Error.Println(setError)
 		return -1
 	}
 
diff --git a/app/tools/libwg-go/jni.c b/app/tools/libwg-go/jni.c
index d32d64c4..1476dab7 100644
--- a/app/tools/libwg-go/jni.c
+++ b/app/tools/libwg-go/jni.c
@@ -1,12 +1,12 @@
 #include <jni.h>
 
 struct go_string { const char *str; long n; };
-extern int wgTurnOn(struct go_string ifname, int tun_fd, int mtu, struct go_string settings);
+extern int wgTurnOn(struct go_string ifname, int tun_fd, struct go_string settings);
 extern void wgTurnOff(int handle);
 extern int wgGetSocketV4(int handle);
 extern int wgGetSocketV6(int handle);
 
-JNIEXPORT jint JNICALL Java_com_wireguard_android_backend_GoBackend_wgTurnOn(JNIEnv *env, jclass c, jstring ifname, jint tun_fd, jint mtu, jstring settings)
+JNIEXPORT jint JNICALL Java_com_wireguard_android_backend_GoBackend_wgTurnOn(JNIEnv *env, jclass c, jstring ifname, jint tun_fd, jstring settings)
 {
 	const char *ifname_str = (*env)->GetStringUTFChars(env, ifname, 0);
 	size_t ifname_len = (*env)->GetStringUTFLength(env, ifname);
@@ -15,7 +15,7 @@ JNIEXPORT jint JNICALL Java_com_wireguard_android_backend_GoBackend_wgTurnOn(JNI
 	int ret = wgTurnOn((struct go_string){
 		.str = ifname_str,
 		.n = ifname_len
-	}, tun_fd, mtu, (struct go_string){
+	}, tun_fd, (struct go_string){
 		.str = settings_str,
 		.n = settings_len
 	});