[radio-spinel] fix tracking of current MAC frame counter (#10635)

This commit fixes an issue in `RadioSpinel` related to the tracking of
the MAC frame counter used during RCP restoration. Previously,
`RadioSpinel` tracked the last seen counter on any secured
received/transmitted frame. However, the frame counter should only be
tracked for frames that use Key ID Mode 1 and where the included Key
ID in the frame matches the current Key ID being used. The `SubMac`
module also tracks the current MAC frame counter, and it does perform
Key ID Mode and Key ID checks.

This commit adds a new public API `otLinkGetFrameCounter()` to get the
current frame counter. This is used by `RadioSpinel` to get the frame
counter instead of having `RadioSpinel` track the frame counter
itself.

include/openthread/instance.h

@@ -53,7 +53,7 @@ extern "C" {
  * @note This number versions both OpenThread platform and user APIs.
  *
  */
-#define OPENTHREAD_API_VERSION (437)
+#define OPENTHREAD_API_VERSION (438)
 
 /**
  * @addtogroup api-instance

include/openthread/link.h

@@ -690,6 +690,16 @@ uint8_t otLinkGetMaxFrameRetriesIndirect(otInstance *aInstance);
  */
 void otLinkSetMaxFrameRetriesIndirect(otInstance *aInstance, uint8_t aMaxFrameRetriesIndirect);
 
+/**
+ * Gets the current MAC frame counter value.
+ *
+ * @param[in] aInstance    A pointer to the OpenThread instance.
+ *
+ * @returns The current MAC frame counter value.
+ *
+ */
+uint32_t otLinkGetFrameCounter(otInstance *aInstance);
+
 /**
  * Gets the address mode of MAC filter.
  *

src/core/api/link_api.cpp

@@ -188,6 +188,11 @@ void otLinkSetMaxFrameRetriesIndirect(otInstance *aInstance, uint8_t aMaxFrameRe
 
 #endif // OPENTHREAD_FTD
 
+uint32_t otLinkGetFrameCounter(otInstance *aInstance)
+{
+    return AsCoreType(aInstance).Get<Mac::SubMac>().GetFrameCounter();
+}
+
 #if OPENTHREAD_CONFIG_MAC_FILTER_ENABLE
 
 otMacFilterAddressMode otLinkFilterGetAddressMode(otInstance *aInstance)

src/lib/spinel/radio_spinel.cpp

@@ -38,6 +38,7 @@
 #include <stdarg.h>
 #include <stdlib.h>
 
+#include <openthread/link.h>
 #include <openthread/logging.h>
 #include <openthread/platform/diag.h>
 #include <openthread/platform/time.h>
@@ -703,7 +704,6 @@ otError RadioSpinel::ParseRadioFrame(otRadioFrame   &aFrame,
         if (flags & SPINEL_MD_FLAG_ACKED_SEC)
         {
             mMacFrameCounterSet = true;
-            mMacFrameCounter    = aFrame.mInfo.mRxInfo.mAckFrameCounter;
         }
 #endif
     }
@@ -926,7 +926,6 @@ otError RadioSpinel::SetMacFrameCounter(uint32_t aMacFrameCounter, bool aSetIfLa
                                 aMacFrameCounter, aSetIfLarger));
 #if OPENTHREAD_SPINEL_CONFIG_RCP_RESTORATION_MAX_COUNT > 0
     mMacFrameCounterSet = true;
-    mMacFrameCounter    = aMacFrameCounter;
 #endif
 
 exit:
@@ -1578,7 +1577,6 @@ void RadioSpinel::HandleTransmitDone(uint32_t          aCommand,
 
 #if OPENTHREAD_SPINEL_CONFIG_RCP_RESTORATION_MAX_COUNT > 0
         mMacFrameCounterSet = true;
-        mMacFrameCounter    = frameCounter;
 #endif
     }
 
@@ -2150,7 +2148,7 @@ void RadioSpinel::RestoreProperties(void)
 
     if (mMacFrameCounterSet)
     {
-        // There is a chance that radio/RCP has used some counters after `mMacFrameCounter` (for enh ack) and they
+        // There is a chance that radio/RCP has used some counters after otLinkGetFrameCounter() (for enh ack) and they
         // are in queue to be sent to host (not yet processed by host RadioSpinel). Here we add some guard jump
         // when we restore the frame counter.
         // Consider the worst case: the radio/RCP continuously receives the shortest data frame and replies with the
@@ -2162,8 +2160,8 @@ void RadioSpinel::RestoreProperties(void)
         // CounterGuard: 2000ms(Timeout) / [(28bytes(Data) + 29bytes(Ack)) * 32us/byte + 192us(Ifs)] = 992
         static constexpr uint16_t kFrameCounterGuard = 1000;
 
-        SuccessOrDie(
-            Set(SPINEL_PROP_RCP_MAC_FRAME_COUNTER, SPINEL_DATATYPE_UINT32_S, mMacFrameCounter + kFrameCounterGuard));
+        SuccessOrDie(Set(SPINEL_PROP_RCP_MAC_FRAME_COUNTER, SPINEL_DATATYPE_UINT32_S,
+                         otLinkGetFrameCounter(mInstance) + kFrameCounterGuard));
     }
 
     for (int i = 0; i < mSrcMatchShortEntryCount; ++i)

src/lib/spinel/radio_spinel.hpp

@@ -1316,7 +1316,6 @@ private:
     int8_t       mCcaEnergyDetectThreshold;
     int8_t       mTransmitPower;
     int8_t       mFemLnaGain;
-    uint32_t     mMacFrameCounter;
     bool         mCoexEnabled : 1;
     bool         mSrcMatchEnabled : 1;