[cli] mac/mle counters reset (#4341)

* Add counters reset cli command

src/cli/README.md

@@ -247,7 +247,7 @@ Done
 Get the supported counter names.
 
 ```bash
->counters
+> counters
 mac
 mle
 Done
@@ -304,6 +304,17 @@ Parent Changes: 0
 Done
 ```
 
+### counters \<countername\> reset
+
+Reset the counter value.
+
+```bash
+> counters mac reset
+Done
+> counters mle reset
+Done
+```
+
 ### networktime
 
 Get the Thread network time and the time sync parameters.

src/cli/cli.cpp

@@ -892,9 +892,9 @@ void Interpreter::ProcessCounters(int argc, char *argv[])
         mServer->OutputFormat("mac\r\n");
         mServer->OutputFormat("mle\r\n");
     }
-    else if (argc == 1)
+    else if (strcmp(argv[0], "mac") == 0)
     {
-        if (strcmp(argv[0], "mac") == 0)
+        if (argc == 1)
         {
             const otMacCounters *macCounters = otLinkGetCounters(mInstance);
 
@@ -930,7 +930,18 @@ void Interpreter::ProcessCounters(int argc, char *argv[])
             mServer->OutputFormat("    RxErrFcs: %d\r\n", macCounters->mRxErrFcs);
             mServer->OutputFormat("    RxErrOther: %d\r\n", macCounters->mRxErrOther);
         }
-        else if (strcmp(argv[0], "mle") == 0)
+        else if ((argc == 2) && (strcmp(argv[0], "reset") == 0))
+        {
+            otLinkResetCounters(mInstance);
+        }
+        else
+        {
+            ExitNow(error = OT_ERROR_INVALID_ARGS);
+        }
+    }
+    else if (strcmp(argv[0], "mle") == 0)
+    {
+        if (argc == 1)
         {
             const otMleCounters *mleCounters = otThreadGetMleCounters(mInstance);
 
@@ -945,6 +956,10 @@ void Interpreter::ProcessCounters(int argc, char *argv[])
                                   mleCounters->mBetterPartitionAttachAttempts);
             mServer->OutputFormat("Parent Changes: %d\r\n", mleCounters->mParentChanges);
         }
+        else if ((argc == 2) && (strcmp(argv[0], "reset") == 0))
+        {
+            otThreadResetMleCounters(mInstance);
+        }
         else
         {
             ExitNow(error = OT_ERROR_INVALID_ARGS);