diff --git a/src/llc.cpp b/src/llc.cpp
index 2997ec1..c0c517f 100644
--- a/src/llc.cpp
+++ b/src/llc.cpp
@@ -102,3 +102,12 @@
 
 	timeradd(&now, &csec, tv);
 }
+
+bool gprs_llc::is_frame_expired(struct timeval *tv_now, struct timeval *tv)
+{
+	/* Timeout is infinite */
+	if (tv->tv_sec == 0 && tv->tv_usec == 0)
+		return false;
+
+	return timercmp(tv_now, tv, >);
+}