Allow state db to take modified entries made to the tunnel decap table (sonic-net#3960)

What I did
Allow state db to take modified entries made to the tunnel decap table

Why I did it
Prevent DB inconsistency between state, asic and appl db

How I verified it
redis-cli -n 6 HGETALL "TUNNEL_DECAP_TABLE|IPINIP_V6_TUNNEL"

"tunnel_type"
"IPINIP"
"dscp_mode"
"pipe"
"ecn_mode"
"standard"
"ttl_mode"
"pipe"
/var/log/syslog.1:2025 Nov 10 19:18:32.730385 bjw-can-2700-2 NOTICE swss#orchagent: :- doDecapTunnelTask: Fields for TUNNEL_DECAP_TABLE entry 'IPINIP_TUNNEL' have been synchronised in STATE_DB
/var/log/syslog.1:2025 Nov 10 19:18:32.740298 bjw-can-2700-2 NOTICE swss#orchagent: :- doDecapTunnelTask: Fields for TUNNEL_DECAP_TABLE entry 'IPINIP_V6_TUNNEL' have been synchronised in STATE_DB

Author: developfast

orchagent/tunneldecaporch.cpp

@@ -160,6 +160,7 @@ void TunnelDecapOrch::doDecapTunnelTask(Consumer &consumer)
                     }
                     if (exists)
                     {
+                        // Apply to SAI; only touch cache/flag on success
                         setTunnelAttribute(fvField(i), dscp_mode, tunnel_id);
                         tunnelTable[key].dscp_mode = dscp_mode;
                     }
@@ -207,6 +208,7 @@ void TunnelDecapOrch::doDecapTunnelTask(Consumer &consumer)
                     }
                     if (exists)
                     {
+                        // Apply to SAI; only touch cache/flag on success
                         setTunnelAttribute(fvField(i), ttl_mode, tunnel_id);
                     }
                 }
@@ -221,6 +223,7 @@ void TunnelDecapOrch::doDecapTunnelTask(Consumer &consumer)
                     }
                     if (exists)
                     {
+                        // Apply to SAI; only touch cache/flag on success
                         setTunnelAttribute(fvField(i), dscp_to_tc_map_id, tunnel_id);
                     }
                 }
@@ -235,6 +238,7 @@ void TunnelDecapOrch::doDecapTunnelTask(Consumer &consumer)
                     }
                     if (exists)
                     {
+                        // Apply to SAI; only touch cache/flag on success
                         setTunnelAttribute(fvField(i), tc_to_pg_map_id, tunnel_id);
                     }
                 }
@@ -276,6 +280,13 @@ void TunnelDecapOrch::doDecapTunnelTask(Consumer &consumer)
                 }
             }
 
+            if (exists)
+            {
+                // Publish to STATE_DB if any mirrored field changed
+                setDecapTunnelStatus(key);
+                SWSS_LOG_NOTICE("Fields for TUNNEL_DECAP_TABLE entry '%s' have been synchronised in STATE_DB", key.c_str());
+            }
+
             if (task_status == task_process_status::task_need_retry)
             {
                 ++it;

tests/mock_tests/Makefile.am

@@ -41,6 +41,7 @@ tests_SOURCES = aclorch_ut.cpp \
                 saispy_ut.cpp \
                 consumer_ut.cpp \
                 sfloworh_ut.cpp \
+                tunneldecaporch_ut.cpp \
                 ut_saihelper.cpp \
                 mock_orchagent_main.cpp \
                 mock_dbconnector.cpp \