Remove redundant nonterminating actions except the last one

Currently, this applies only to "state-timeout", but may extend to more
actions in the future.

This logic supports progressive refinement, such as initial rules setting a
general TCP timeout and subsequent rules refining specifics.

controlplane/acl_value.cpp

@@ -43,6 +43,28 @@ void value_t::ensure_termination(IntermediateActions& actions)
 	}
 }
 
+void value_t::remove_redundant_actions(IntermediateActions& actions)
+{
+	constexpr std::array<size_t, 1> affected_nonterminating_rules = {
+	        common::variant::get_index<common::StateTimeoutAction, common::RawAction>::value};
+
+	for (size_t index : affected_nonterminating_rules)
+	{
+		if (actions.action_counts[index] <= 1)
+			continue;
+
+		size_t count_to_remove = actions.action_counts[index] - 1;
+
+		auto pred = [index, &count_to_remove](const common::Action& action) {
+			return action.raw_action.index() == index && count_to_remove-- > 0;
+		};
+
+		auto new_end = std::remove_if(actions.path.begin(), actions.path.end(), pred);
+
+		actions.path.erase(new_end, actions.path.end());
+	}
+}
+
 void value_t::finalize_actions(IntermediateActions&& actions)
 {
 	if (actions.check_state_index.has_value())
@@ -60,6 +82,7 @@ void value_t::compile()
 	for (auto& actions : intermediate_vector)
 	{
 		ensure_termination(actions);
+		remove_redundant_actions(actions);
 		finalize_actions(std::move(actions));
 	}
 }

controlplane/acl_value.h

@@ -13,6 +13,13 @@ class value_t
 	 */
 	void ensure_termination(IntermediateActions& actions);
 
+	/**
+	 * Removes all but the last occurrence of some non-terminating actions
+	 *
+	 * Affected non-terminating actions: StateTimeout
+	 */
+	void remove_redundant_actions(IntermediateActions& actions);
+
 	/**
 	 * Finalizes the intermediate actions into a vector of BaseActions objects.
 	 */
@@ -52,7 +59,8 @@ class value_t
 	 * The compile process involves:
 	 * 1. Ensuring that the last action in the path is terminating.
 	 *    If not, a default "drop" rule is added.
-	 * 2. Finalizing the actions into a vector of BaseActions objects
+	 * 2. Removing all but the last occurrence of some non-terminating actions
+	 * 3. Finalizing the actions into a vector of BaseActions objects
 	 */
 	void compile();