From 3694da2dcde998206e0ff2869b279e8ff6686818 Mon Sep 17 00:00:00 2001
From: Andy CA6JAU <juribeparada@gmail.com>
Date: Sat, 21 Jul 2018 21:01:55 -0400
Subject: [PATCH] Drop duplicate and out-of-sequence DMR audio frames from RF

---
 DMRSlot.cpp | 12 ++++++++++++
 DMRSlot.h   |  1 +
 2 files changed, 13 insertions(+)

diff --git a/DMRSlot.cpp b/DMRSlot.cpp
index f50a783..769a114 100644
--- a/DMRSlot.cpp
+++ b/DMRSlot.cpp
@@ -89,6 +89,7 @@ m_rfLC(NULL),
 m_netLC(NULL),
 m_rfSeqNo(0U),
 m_rfN(0U),
+m_lastrfN(0U),
 m_netN(0U),
 m_networkWatchdog(1000U, 0U, 1500U),
 m_rfTimeoutTimer(1000U, timeout),
@@ -529,6 +530,7 @@ bool CDMRSlot::writeModem(unsigned char *data, unsigned int len)
 		}
 	} else if (audioSync) {
 		if (m_rfState == RS_RF_AUDIO) {
+			m_lastrfN = 0;
 			// Convert the Audio Sync to be from the BS or MS as needed
 			CSync::addDMRAudioSync(data + 2U, m_duplex);
 
@@ -574,6 +576,11 @@ bool CDMRSlot::writeModem(unsigned char *data, unsigned int len)
 			m_rfN = data[1U] & 0x0FU;
 			if (m_rfN > 5U)
 				return false;
+			if (m_rfN == m_lastrfN)
+				return false;
+			if (m_rfN != (m_lastrfN + 1U))
+				return false;
+			m_lastrfN = m_rfN;
 
 			unsigned int errors = 0U;
 			unsigned char fid = m_rfLC->getFID();
@@ -816,6 +823,11 @@ bool CDMRSlot::writeModem(unsigned char *data, unsigned int len)
 				m_rfN = data[1U] & 0x0FU;
 				if (m_rfN > 5U)
 					return false;
+				if (m_rfN == m_lastrfN)
+					return false;
+				if (m_rfN != (m_lastrfN + 1U))
+					return false;
+				m_lastrfN = m_rfN;
 
 				// Regenerate the EMB
 				emb.getData(data + 2U);
diff --git a/DMRSlot.h b/DMRSlot.h
index 4dfbde4..ff00617 100644
--- a/DMRSlot.h
+++ b/DMRSlot.h
@@ -79,6 +79,7 @@ private:
 	CDMRLC*                    m_netLC;
 	unsigned char              m_rfSeqNo;
 	unsigned char              m_rfN;
+	unsigned char              m_lastrfN;
 	unsigned char              m_netN;
 	CTimer                     m_networkWatchdog;
 	CTimer                     m_rfTimeoutTimer;