Add ping stop command. (#1925)

src/cli/README.md

@@ -1272,6 +1272,15 @@ Send an ICMPv6 Echo Request.
 16 bytes from fdde:ad00:beef:0:558:f56b:d688:799: icmp_seq=1 hlim=64 time=28ms
 ```
 
+### ping stop
+
+Stop sending ICMPv6 Echo Requests.
+
+```bash
+> ping stop
+Done
+```
+
 ### pollperiod
 
 Get the customized data poll period of sleepy end device (seconds). Only for certification test

src/cli/cli.cpp

@@ -1623,6 +1623,21 @@ void Interpreter::ProcessPing(int argc, char *argv[])
     long value;
 
     VerifyOrExit(argc > 0, error = OT_ERROR_PARSE);
+
+    if (strcmp(argv[0], "stop") == 0)
+    {
+        if (!mPingTimer.IsRunning())
+        {
+            error = OT_ERROR_INVALID_STATE;
+        }
+        else
+        {
+            mPingTimer.Stop();
+        }
+
+        ExitNow();
+    }
+
     VerifyOrExit(!mPingTimer.IsRunning(), error = OT_ERROR_BUSY);
 
     memset(&mMessageInfo, 0, sizeof(mMessageInfo));