From eb5b42a86e8bc58e28b6290045457ad2c4caa223 Mon Sep 17 00:00:00 2001
From: Simon Lin <simonlin@google.com>
Date: Thu, 5 Sep 2019 13:02:26 +0800
Subject: [PATCH] [mle] reset MLE adv timer when cost changes to/from infinite
 (#4129)

---
 src/core/thread/mle_router.cpp | 21 ++++++++++++++++++---
 1 file changed, 18 insertions(+), 3 deletions(-)

diff --git a/src/core/thread/mle_router.cpp b/src/core/thread/mle_router.cpp
index b90c664f5..8927b9ed5 100644
--- a/src/core/thread/mle_router.cpp
+++ b/src/core/thread/mle_router.cpp
@@ -1427,7 +1427,8 @@ void MleRouter::UpdateRoutes(const RouteTlv &aRoute, uint8_t aRouterId)
     uint8_t cost;
     uint8_t linkQuality;
     bool    update;
-    bool    changed = false;
+    bool    resetAdvInterval = false;
+    bool    changed          = false;
 
     neighbor = mRouterTable.GetRouter(aRouterId);
     VerifyOrExit(neighbor != NULL);
@@ -1461,7 +1462,16 @@ void MleRouter::UpdateRoutes(const RouteTlv &aRoute, uint8_t aRouterId)
 
                 if (neighbor->GetLinkQualityOut() != linkQuality)
                 {
+                    uint8_t oldLinkCost = mRouterTable.GetLinkCost(*neighbor);
                     neighbor->SetLinkQualityOut(linkQuality);
+                    nextHop = mRouterTable.GetRouter(neighbor->GetNextHop());
+
+                    // reset MLE advertisement timer if neighbor route cost changed to or from infinite
+                    if (nextHop == NULL &&
+                        (oldLinkCost >= kMaxRouteCost) != (mRouterTable.GetLinkCost(*neighbor) >= kMaxRouteCost))
+                    {
+                        resetAdvInterval = true;
+                    }
                     update = true;
                 }
             }
@@ -1494,7 +1504,7 @@ void MleRouter::UpdateRoutes(const RouteTlv &aRoute, uint8_t aRouterId)
                         {
                             if (nextHop == NULL && mRouterTable.GetLinkCost(*router) >= kMaxRouteCost)
                             {
-                                ResetAdvertiseInterval();
+                                resetAdvInterval = true;
                             }
 
                             router->SetNextHop(aRouterId);
@@ -1505,7 +1515,7 @@ void MleRouter::UpdateRoutes(const RouteTlv &aRoute, uint8_t aRouterId)
                         {
                             if (mRouterTable.GetLinkCost(*router) >= kMaxRouteCost)
                             {
-                                ResetAdvertiseInterval();
+                                resetAdvInterval = true;
                             }
 
                             router->SetNextHop(kInvalidRouterId);
@@ -1538,6 +1548,11 @@ void MleRouter::UpdateRoutes(const RouteTlv &aRoute, uint8_t aRouterId)
 
     } while (update);
 
+    if (resetAdvInterval)
+    {
+        ResetAdvertiseInterval();
+    }
+
 #if (OPENTHREAD_CONFIG_LOG_MLE && (OPENTHREAD_CONFIG_LOG_LEVEL >= OT_LOG_LEVEL_INFO))
 
     VerifyOrExit(changed);