Get failed neighbors from kernel instead of db

Signed-off-by: Lawrence Lee <lawlee@microsoft.com>

files/scripts/arp_update

@@ -77,14 +77,18 @@ while /bin/true; do
       eval `eval $ip6cmd`
   done
 
-  DBNEIGH=$(sonic-db-cli APPL_DB keys NEIGH_TABLE*)
+  # on dual ToR devices, try to resolve failed neighbor entries since
+  # these entries will have tunnel routes installed, preventing normal 
+  # neighbor resolution
+  KERNEL_NEIGHBORS=$(ip -4 neigh show | grep Vlan | cut -d ' ' -f 1,3,6 --output-delimiter=','; \
+                     ip -6 neigh show | grep -v fe80 | grep Vlan | cut -d ' ' -f 1,3,5 --output-delimiter=',')
   TUNNEL_ENTRY=$(sonic-db-cli CONFIG_DB keys "TUNNEL|*")
   if [[ ! -z $TUNNEL_ENTRY ]]; then
-    for neigh in $DBNEIGH; do
-        MAC=$(sonic-db-cli APPL_DB hgetall $neigh | cut -d '{' -f 2 | cut -d ',' -f 1 | cut -d ' ' -f 2 | cut -d "'" -f 2)
-        if [[ $MAC == "00:00:00:00:00:00" ]]; then
-            intf="$( cut -d ':' -f 2 <<< "$neigh" )"
-            ip="$( cut -d ':' -f 3- <<< "$neigh" )"
+    for neigh in $KERNEL_NEIGHBORS; do
+        STATE=$(cut -d ',' -f 3 <<< $neigh)
+        if [[ $STATE == "FAILED" ]] || [[ $STATE == "INCOMPLETE" ]]; then
+            intf=$(cut -d ',' -f 2 <<< $neigh)
+            ip=$(cut -d ',' -f 1 <<< $neigh)
             pingcmd="timeout 0.2 ping -I $intf -n -q -i 0 -c 1 -W 1 $ip >/dev/null"
             eval $pingcmd
             logger "arp_update: resolving failed neighbor entry, pinging ${ip} on ${intf}"