[ot-rfsim] clean up usage of global vars/externs (openthread#769)

The usage of global vars and 'extern' in the RFSIM platform was hard to disentangle.
This fixes the issue by placing all 'extern' references in the header file along with
comments as to what these variables do. This way, all the relevant sources have access
to these global vars.

Author: EskoDijk

ot-rfsim/src/event-sim.c

@@ -37,10 +37,6 @@
 #include "event-sim.h"
 #include "platform-rfsim.h"
 
-// socket communication parameters for events
-extern int          gSockFd;
-extern struct Event gLastRecvEvent;
-
 struct Event gLastSentEvent;
 
 void otSimSendSleepEvent(void)

ot-rfsim/src/misc.c

@@ -1,5 +1,5 @@
 /*
- *  Copyright (c) 2016-2024, The OpenThread Authors.
+ *  Copyright (c) 2016-2026, The OpenThread Authors.
  *  All rights reserved.
  *
  *  Redistribution and use in source and binary forms, with or without
@@ -37,8 +37,7 @@
 
 #include "common/logging.hpp"
 
-extern jmp_buf      gResetJump;
-extern struct Event gLastSentEvent, gLastRecvEvent;
+extern jmp_buf gResetJump;
 
 otPlatResetReason   gPlatResetReason = OT_PLAT_RESET_REASON_POWER_ON;
 bool                gPlatformPseudoResetWasRequested;

ot-rfsim/src/platform-rfsim.c

@@ -57,11 +57,9 @@
 
 static const otIp6Address kUnspecifiedIp6Address = {.mFields = {.m32 = {0, 0, 0, 0}}};
 
-extern int gSockFd;
-
 void platformRfsimInit(void)
 {
-    // No actions currently.
+    // No actions currently. Global structs are automatically zero-initialized.
 }
 
 void platformExit(int exitCode)

ot-rfsim/src/platform-rfsim.h

@@ -1,5 +1,5 @@
 /*
- *  Copyright (c) 2016-2024, The OpenThread Authors.
+ *  Copyright (c) 2016-2026, The OpenThread Authors.
  *  All rights reserved.
  *
  *  Redistribution and use in source and binary forms, with or without
@@ -67,21 +67,29 @@
 
 /**
  * Unique node ID.
- *
  */
 extern uint32_t gNodeId;
 
 /**
- * MsgId of last received event from simulator, or 0 if no MsgId yet received.
+ * Last received event from simulator.
+ */
+extern struct Event gLastRecvEvent;
+
+/**
+ * Last (attempted and/or succeeded) sent event to simulator.
  */
-extern uint64_t gLastMsgId;
+extern struct Event gLastSentEvent;
 
 /**
  * State of requested termination of this node process.
- *
  */
 extern volatile bool gTerminate;
 
+/**
+ * Unix socket file descriptor for communication with simulator.
+ */
+extern int gSockFd;
+
 /**
  * initializes the alarm/time service used by OpenThread.
  *

ot-rfsim/src/system.c

@@ -156,6 +156,7 @@ void otSysProcessDrivers(otInstance *aInstance)
         is_new_event = true;
     }
 
+    // Sleep if nothing more to do
     if (!is_new_event && !otTaskletsArePending(aInstance) && platformAlarmGetNext() > 0 &&
         (!platformRadioIsTransmitPending() || platformRadioIsBusy()) && !platformUartHasPendingData())
     {

radiomodel/radionode.go

@@ -89,7 +89,7 @@ func (rn *RadioNode) SetChannel(ch ChannelId) {
 }
 
 // SetTxDone moves the physical radio state, if currently Tx, to Rx. The RadioSubState is not altered, as
-// the expectation is that the node will report its state/substate soon after using an EventTypeRadioState
+// the expectation is that the node will report its state/substate soon after: with an EventTypeRadioState
 // event. Setting the RadioState to RadioRx here will enable frame dispatching to the node again, which is
 // not done while the radio is in RadioTx state. The RFSIM simulated radio further determines (based on its
 // substate) whether the node will be able to receive the frame dispatched to it.