android: Don't use infinite keying tries on Android 5+

This way we get some feedback about the issue in the GUI (otherwise it
would just switch to connecting state) and also some delays between retries.

src/frontends/android/app/src/main/jni/libandroidbridge/android_jni.h

@@ -57,6 +57,7 @@ typedef enum {
 	ANDROID_JELLY_BEAN = 16,
 	ANDROID_JELLY_BEAN_MR1 = 17,
 	ANDROID_JELLY_BEAN_MR2 = 18,
+	ANDROID_LOLLIPOP = 21,
 } android_sdk_version_t;
 
 /**

src/frontends/android/app/src/main/jni/libandroidbridge/backend/android_service.c

@@ -18,6 +18,7 @@
 #include <errno.h>
 #include <unistd.h>
 
+#include "android_jni.h"
 #include "android_service.h"
 #include "android_dns_proxy.h"
 #include "../charonservice.h"
@@ -761,6 +762,11 @@ static job_requeue_t initiate(private_android_service_t *this)
 	int port;
 	bool certreq;
 
+	if (android_sdk_version >= ANDROID_LOLLIPOP)
+	{   /* only try once and notify the GUI on Android 5+ where we have a blocking TUN device */
+		peer.keyingtries = 1;
+	}
+
 	server = this->settings->get_str(this->settings, "connection.server", NULL);
 	port = this->settings->get_int(this->settings, "connection.port",
 								   IKEV2_UDP_PORT);