Fix issue with ipset or iptables chain removal during NodeNetworkPoli…

…cy updates or deletions (#6707) (#6727)

This commit addresses an issue where stale ipset or iptables chain is
not deleted during NodeNetworkPolicy updates or deletions. The root cause
is that the ipset or iptables chain is still referenced by other iptables
rules during the deletion or update attempt. The fix ensures proper order
of ipset and iptables synchronization.

Signed-off-by: Hongliang Liu <[email protected]>

pkg/agent/controller/networkpolicy/node_reconciler_linux.go

@@ -297,13 +297,13 @@ func (r *nodeReconciler) Forget(ruleID string) error {
 		if err := r.deleteCoreIPTRule(ruleID, coreIPTChain, isIPv6); err != nil {
 			return err
 		}
-		if lastRealized.ipsets[ipProtocol] != "" {
-			if err := r.routeClient.DeleteNodeNetworkPolicyIPSet(lastRealized.ipsets[ipProtocol], isIPv6); err != nil {
+		if lastRealized.serviceIPTChain != "" {
+			if err := r.routeClient.DeleteNodeNetworkPolicyIPTables([]string{lastRealized.serviceIPTChain}, isIPv6); err != nil {
 				return err
 			}
 		}
-		if lastRealized.serviceIPTChain != "" {
-			if err := r.routeClient.DeleteNodeNetworkPolicyIPTables([]string{lastRealized.serviceIPTChain}, isIPv6); err != nil {
+		if lastRealized.ipsets[ipProtocol] != "" {
+			if err := r.routeClient.DeleteNodeNetworkPolicyIPSet(lastRealized.ipsets[ipProtocol], isIPv6); err != nil {
 				return err
 			}
 		}
@@ -440,18 +440,39 @@ func (r *nodeReconciler) update(lastRealized *nodePolicyLastRealized, newRule *C
 		prevIPSet := lastRealized.ipsets[ipProtocol]
 		ipset := newLastRealized.ipsets[ipProtocol]
 
+		// Core iptables rules should be updated in the following cases:
+		// - Single IP change: A -> B (prevIPSet = "", ipset = "", prevIPNet = A, ipnet = B).
+		// - Transition from multiple addresses to a single IP: {A, B} -> A (prevIPSet = "ipset name", ipset = "", prevIPNet = "", ipnet = A).
+		// - Transition from a single IP to multiple addresses: A -> {A, B} (prevIPNet = A, ipnet = "", prevIPSet = "", ipset = "ipset name").
+		shouldUpdateCoreIPTRules := prevIPSet != ipset || prevIPNet != ipnet
+		// The name of ipset for a rule will never change during updates.
 		if ipset != "" {
+			// If the current rule uses an ipset, sync the ipset first, then sync the core iptables rule that
+			// references it.
 			if err := r.routeClient.AddOrUpdateNodeNetworkPolicyIPSet(iptRule.IPSet, iptRule.IPSetMembers, iptRule.IsIPv6); err != nil {
 				return err
 			}
+			if shouldUpdateCoreIPTRules {
+				if err := r.addOrUpdateCoreIPTRules(iptRule.CoreIPTChain, iptRule.IsIPv6, true, &coreIPTRule{ruleID, iptRule.Priority, iptRule.CoreIPTRule}); err != nil {
+					return err
+				}
+			}
 		} else if prevIPSet != "" {
+			// If the previous rule used an ipset, sync the new core iptables rule first to remove its reference, then
+			// delete the unused ipset.
+			if shouldUpdateCoreIPTRules {
+				if err := r.addOrUpdateCoreIPTRules(iptRule.CoreIPTChain, iptRule.IsIPv6, true, &coreIPTRule{ruleID, iptRule.Priority, iptRule.CoreIPTRule}); err != nil {
+					return err
+				}
+			}
 			if err := r.routeClient.DeleteNodeNetworkPolicyIPSet(lastRealized.ipsets[ipProtocol], iptRule.IsIPv6); err != nil {
 				return err
 			}
-		}
-		if prevIPSet != ipset || prevIPNet != ipnet {
-			if err := r.addOrUpdateCoreIPTRules(iptRule.CoreIPTChain, iptRule.IsIPv6, true, &coreIPTRule{ruleID, iptRule.Priority, iptRule.CoreIPTRule}); err != nil {
-				return err
+		} else {
+			if shouldUpdateCoreIPTRules {
+				if err := r.addOrUpdateCoreIPTRules(iptRule.CoreIPTChain, iptRule.IsIPv6, true, &coreIPTRule{ruleID, iptRule.Priority, iptRule.CoreIPTRule}); err != nil {
+					return err
+				}
 			}
 		}
 	}