[Fdbsyncd] Adding extern_learn flag with fdb entry so Kernel doesn't …

…age out (sonic-net#2985)

* Adding extern_learn flag with fdb entry so that Kernel doesn't age out the MAC

* [Fdbsyncd] Adding extern_learn flag with fdb entry so Kernel doesn't age out

What I did
extern_learn flag is added while programming the fdb entry into the Kernel. This will make sure that kernel doesn't age out the fdb entry. (#15004)

How I did it
A flag extern_learn will be passed while programing the fdb entry. (#15004)

How to verify it
Tested MAC add/del to the Kernel from the local FDB entry. (#15004)

Signed-off-by: kishore.kunal@broadcom.com

---------

Signed-off-by: kishore.kunal@broadcom.com
Co-authored-by: Sudharsan Dhamal Gopalarathnam <sudharsand@nvidia.com>

fdbsyncd/fdbsync.cpp

@@ -324,7 +324,7 @@ void FdbSync::updateLocalMac (struct m_fdb_info *info)
 
     if (fdb_type == FDB_TYPE_DYNAMIC)
     {
-        type = "dynamic";
+        type = "dynamic extern_learn";
     }
     else
     {
@@ -384,7 +384,7 @@ void FdbSync::addLocalMac(string key, string op)
 
         if (m_fdb_mac[key].type == FDB_TYPE_DYNAMIC)
         {
-            type = "dynamic";
+            type = "dynamic extern_learn";
         }
         else
         {
@@ -432,7 +432,7 @@ void FdbSync::updateMclagRemoteMac (struct m_fdb_info *info)
 
     if (fdb_type == FDB_TYPE_DYNAMIC)
     {
-        type = "dynamic";
+        type = "dynamic extern_learn";
     }
     else
     {
@@ -511,7 +511,7 @@ void FdbSync::macRefreshStateDB(int vlan, string kmac)
 
         if (m_fdb_mac[key].type == FDB_TYPE_DYNAMIC)
         {
-            type = "dynamic";
+            type = "dynamic extern_learn";
         }
         else
         {