Remove policies in kernel interfaces based on their priority.

This allows to unroute a connection while the same connection is
currently established.  In this case both CHILD_SAs share the same
reqid but the installed policies have different priorities.

src/libhydra/kernel/kernel_interface.h

@@ -188,7 +188,7 @@ struct kernel_interface_t {
 	 * @param type			type of policy, POLICY_(IPSEC|PASS|DROP)
 	 * @param sa			details about the SA(s) tied to this policy
 	 * @param mark			mark for this policy
-	 * @param routed		TRUE, if this policy is routed in the kernel
+	 * @param priority		priority of this policy
 	 * @return				SUCCESS if operation completed
 	 */
 	status_t (*add_policy) (kernel_interface_t *this,
@@ -196,7 +196,8 @@ struct kernel_interface_t {
 							traffic_selector_t *src_ts,
 							traffic_selector_t *dst_ts,
 							policy_dir_t direction, policy_type_t type,
-							ipsec_sa_cfg_t *sa, mark_t mark, bool routed);
+							ipsec_sa_cfg_t *sa, mark_t mark,
+							policy_priority_t priority);
 
 	/**
 	 * Query the use time of a policy.
@@ -230,14 +231,14 @@ struct kernel_interface_t {
 	 * @param direction		direction of traffic, POLICY_(IN|OUT|FWD)
 	 * @param reqid			unique ID of the associated SA
 	 * @param mark			optional mark
-	 * @param unrouted		TRUE, if this policy is unrouted from the kernel
+	 * @param priority		priority of the policy
 	 * @return				SUCCESS if operation completed
 	 */
 	status_t (*del_policy) (kernel_interface_t *this,
 							traffic_selector_t *src_ts,
 							traffic_selector_t *dst_ts,
 							policy_dir_t direction, u_int32_t reqid,
-							mark_t mark, bool unrouted);
+							mark_t mark, policy_priority_t priority);
 
 	/**
 	 * Get our outgoing source address for a destination.