From f64c597fc67dfc8584bc6494f811c53b6f38c9e7 Mon Sep 17 00:00:00 2001
From: Jonathan Hui <jonhui@google.com>
Date: Tue, 5 Jan 2021 09:35:45 -0800
Subject: [PATCH] [coap] fix order of operations in TxParameters::IsValid()
 (#6027)

To match CalculateInitialRetransmissionTimeout() implementation.
---
 src/core/coap/coap.cpp | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/src/core/coap/coap.cpp b/src/core/coap/coap.cpp
index 36f4c9d2b..48302ca64 100644
--- a/src/core/coap/coap.cpp
+++ b/src/core/coap/coap.cpp
@@ -950,8 +950,8 @@ bool TxParameters::IsValid(void) const
         // Calulate exchange lifetime step by step and verify no overflow.
         uint32_t tmp = Multiply(mAckTimeout, (1U << (mMaxRetransmit + 1)) - 1);
 
-        tmp /= mAckRandomFactorDenominator;
         tmp = Multiply(tmp, mAckRandomFactorNumerator);
+        tmp /= mAckRandomFactorDenominator;
 
         rval = (tmp != 0 && (tmp + mAckTimeout + 2 * kDefaultMaxLatency) > tmp);
     }