Avoid adding loopback interface (ip link add) when setting nat zone on loopback interface (sonic-net#1434)

Signed-off-by: Akhilesh Samineni <[email protected]>

Author: AkhileshSamineni

cfgmgr/intfmgr.cpp

@@ -495,7 +495,12 @@ bool IntfMgr::doIntfGeneralTask(const vector<string>& keys,
 
         if (is_lo)
         {
-            addLoopbackIntf(alias);
+            if (m_loopbackIntfList.find(alias) == m_loopbackIntfList.end())
+            {
+                addLoopbackIntf(alias);
+                m_loopbackIntfList.insert(alias);
+                SWSS_LOG_INFO("Added %s loopback interface", alias.c_str());
+            }
         }
         else
         {
@@ -598,6 +603,7 @@ bool IntfMgr::doIntfGeneralTask(const vector<string>& keys,
         if (is_lo)
         {
             delLoopbackIntf(alias);
+            m_loopbackIntfList.erase(alias);
         }
 
         if (!subIntfAlias.empty())

cfgmgr/intfmgr.h

@@ -22,6 +22,7 @@ class IntfMgr : public Orch
     Table m_statePortTable, m_stateLagTable, m_stateVlanTable, m_stateVrfTable, m_stateIntfTable;
 
     std::set<std::string> m_subIntfList;
+    std::set<std::string> m_loopbackIntfList;
 
     void setIntfIp(const std::string &alias, const std::string &opCmd, const IpPrefix &ipPrefix);
     void setIntfVrf(const std::string &alias, const std::string &vrfName);