Fix routing cost comparison issue when chosing BR (#1759)

* Fix routing cost comparison issue when chosing BR

* remove extra space

* update for comments

src/core/thread/mle_router.cpp

@@ -3376,6 +3376,26 @@ exit:
     return rval;
 }
 
+uint8_t MleRouter::GetCost(uint16_t aRloc16)
+{
+    uint8_t routerId = GetRouterId(aRloc16);
+    uint8_t cost = GetLinkCost(routerId);
+    Router *router = GetRouter(routerId);
+    uint8_t routeCost;
+
+    VerifyOrExit(router != NULL && GetRouter(router->GetNextHop()) != NULL);
+
+    routeCost = GetRouteCost(aRloc16) + GetLinkCost(GetRouter(routerId)->GetNextHop());
+
+    if (cost > routeCost)
+    {
+        cost = routeCost;
+    }
+
+exit:
+    return cost;
+}
+
 uint8_t MleRouter::GetRouteCost(uint16_t aRloc16) const
 {
     uint8_t rval = kMaxRouteCost;

src/core/thread/mle_router_ftd.hpp

@@ -264,6 +264,16 @@ public:
      */
     uint8_t GetLinkCost(uint8_t aRouterId);
 
+    /**
+     * This method returns the minimum cost to the given router.
+     *
+     * @param[in]  aRloc16  The short address of the given router.
+     *
+     * @returns The minimum cost to the given router (via direct link or forwarding).
+     *
+     */
+    uint8_t GetCost(uint16_t aRloc16);
+
     /**
      * This method returns the ROUTER_SELECTION_JITTER value.
      *

src/core/thread/mle_router_mtd.hpp

@@ -69,6 +69,7 @@ public:
 
     uint8_t GetRouteCost(uint16_t) const { return 0; }
     uint8_t GetLinkCost(uint16_t) { return 0; }
+    uint8_t GetCost(uint16_t) { return 0; }
 
     uint8_t GetRouterIdSequence(void) const { return 0; }
 

src/core/thread/network_data_leader.cpp

@@ -329,8 +329,7 @@ ThreadError LeaderBase::ExternalRouteLookup(uint8_t aDomainId, const Ip6::Addres
                     if (rvalRoute == NULL ||
                         entry->GetPreference() > rvalRoute->GetPreference() ||
                         (entry->GetPreference() == rvalRoute->GetPreference() &&
-                         mNetif.GetMle().GetRouteCost(entry->GetRloc()) <
-                         mNetif.GetMle().GetRouteCost(rvalRoute->GetRloc())))
+                         mNetif.GetMle().GetCost(entry->GetRloc()) < mNetif.GetMle().GetCost(rvalRoute->GetRloc())))
                     {
                         rvalRoute = entry;
                         rval_plen = static_cast<uint8_t>(plen);
@@ -387,7 +386,7 @@ ThreadError LeaderBase::DefaultRouteLookup(PrefixTlv &aPrefix, uint16_t *aRloc16
             if (route == NULL ||
                 entry->GetPreference() > route->GetPreference() ||
                 (entry->GetPreference() == route->GetPreference() &&
-                 mNetif.GetMle().GetRouteCost(entry->GetRloc()) < mNetif.GetMle().GetRouteCost(route->GetRloc())))
+                 mNetif.GetMle().GetCost(entry->GetRloc()) < mNetif.GetMle().GetCost(route->GetRloc())))
             {
                 route = entry;
             }

tests/scripts/thread-cert/node_cli.py

@@ -382,7 +382,7 @@ class otCli:
         self.pexpect.expect('Done')
 
     def remove_prefix(self, prefix):
-        cmd = ' prefix remove ' + prefix
+        cmd = 'prefix remove ' + prefix
         self.send_command(cmd)
         self.pexpect.expect('Done')