[spinel] do not update the sent frame when the diag is enabled

When running command `diag frame -s fd874f68f1ca00efbe00adde5d4f4913e953845a154d4cbab10000000001820e390005009bb8ea011c58a065c39fbd` and `diag send 20` to send diag frames,
we found that the frame is modified by the RadioSpinel module. Which causes the diag sent frames are not the same.

This commit disables the RadioSpinel module from changing the sent frame when the diag mode is enabled.

src/core/diags/README.md

@@ -80,13 +80,14 @@ Done
 
 ### diag frame
 
-Usage: `diag frame [-c] [-p TX_POWER] [-s] <frame>`
+Usage: `diag frame [-c] [-p TX_POWER] [-s] [-u] <frame>`
 
 Set the frame (hex encoded) to be used by `diag send` and `diag repeat`. The frame may be overwritten by `diag send` and `diag repeat`.
 
-- Specify `-s` to indicate that tx security is already processed so that it should be skipped in the radio layer.
 - Specify `-c` to enable CSMA/CA for this frame in the radio layer.
 - Specify `-p` to specify the tx power in dBm for this frame.
+- Specify `-s` to indicate that tx security is already processed so that it should be skipped in the radio layer.
+- Specify `-u` to specify the `mInfo.mTxInfo.mIsHeaderUpdated` filed for this frame.
 
 ```bash
 > diag frame 11223344

src/core/diags/factory_diags.cpp

@@ -213,6 +213,7 @@ Diags::Diags(Instance &aInstance)
 
 void Diags::ResetTxPacket(void)
 {
+    mIsHeaderUpdated                               = false;
     mTxPacket->mInfo.mTxInfo.mTxDelayBaseTime      = 0;
     mTxPacket->mInfo.mTxInfo.mTxDelay              = 0;
     mTxPacket->mInfo.mTxInfo.mMaxCsmaBackoffs      = 0;
@@ -232,13 +233,15 @@ Error Diags::ProcessFrame(uint8_t aArgsLength, char *aArgs[])
     uint16_t size              = OT_RADIO_FRAME_MAX_SIZE;
     bool     securityProcessed = false;
     bool     csmaCaEnabled     = false;
+    bool     isHeaderUpdated   = false;
     int8_t   txPower           = OT_RADIO_POWER_INVALID;
 
     while (aArgsLength > 1)
     {
         if (StringMatch(aArgs[0], "-s"))
         {
             securityProcessed = true;
+            isHeaderUpdated   = true;
         }
         else if (StringMatch(aArgs[0], "-p"))
         {
@@ -255,6 +258,10 @@ Error Diags::ProcessFrame(uint8_t aArgsLength, char *aArgs[])
         {
             csmaCaEnabled = true;
         }
+        else if (StringMatch(aArgs[0], "-u"))
+        {
+            isHeaderUpdated = true;
+        }
         else
         {
             ExitNow(error = kErrorInvalidArgs);
@@ -276,6 +283,7 @@ Error Diags::ProcessFrame(uint8_t aArgsLength, char *aArgs[])
     mTxPacket->mInfo.mTxInfo.mTxPower             = txPower;
     mTxPacket->mLength                            = size;
     mIsTxPacketSet                                = true;
+    mIsHeaderUpdated                              = isHeaderUpdated;
 
 exit:
     AppendErrorResult(error);
@@ -514,7 +522,13 @@ void Diags::TransmitPacket(void)
 {
     mTxPacket->mChannel = mChannel;
 
-    if (!mIsTxPacketSet)
+    if (mIsTxPacketSet)
+    {
+        // The `mInfo.mTxInfo.mIsHeaderUpdated` field may be updated by the radio driver after the frame is sent,
+        // set the `mInfo.mTxInfo.mIsHeaderUpdated` field before transmitting the frame.
+        mTxPacket->mInfo.mTxInfo.mIsHeaderUpdated = mIsHeaderUpdated;
+    }
+    else
     {
         ResetTxPacket();
         mTxPacket->mLength = mTxLen;

src/core/diags/factory_diags.hpp

@@ -218,9 +218,10 @@ class Diags : public InstanceLocator, private NonCopyable
     uint8_t       mChannel;
     int8_t        mTxPower;
     uint8_t       mTxLen;
-    bool          mIsTxPacketSet;
-    bool          mRepeatActive;
-    bool          mDiagSendOn;
+    bool          mIsHeaderUpdated : 1;
+    bool          mIsTxPacketSet : 1;
+    bool          mRepeatActive : 1;
+    bool          mDiagSendOn : 1;
 #endif
 
     otDiagOutputCallback mOutputCallback;

src/lib/spinel/radio_spinel.cpp

@@ -1582,10 +1582,8 @@ void RadioSpinel::HandleTransmitDone(uint32_t          aCommand,
         error = SpinelStatusToOtError(status);
     }
 
-    static_cast<Mac::TxFrame *>(mTransmitFrame)->SetIsHeaderUpdated(headerUpdated);
-
-    if ((sRadioCaps & OT_RADIO_CAPS_TRANSMIT_SEC) && headerUpdated &&
-        static_cast<Mac::TxFrame *>(mTransmitFrame)->GetSecurityEnabled())
+    if ((sRadioCaps & OT_RADIO_CAPS_TRANSMIT_SEC) && (!mTransmitFrame->mInfo.mTxInfo.mIsHeaderUpdated) &&
+        headerUpdated && static_cast<Mac::TxFrame *>(mTransmitFrame)->GetSecurityEnabled())
     {
         uint8_t  keyId;
         uint32_t frameCounter;
@@ -1602,6 +1600,8 @@ void RadioSpinel::HandleTransmitDone(uint32_t          aCommand,
 #endif
     }
 
+    static_cast<Mac::TxFrame *>(mTransmitFrame)->SetIsHeaderUpdated(headerUpdated);
+
 exit:
     // A parse error indicates an RCP misbehavior, so recover the RCP immediately.
     mState = kStateTransmitDone;