kernel-pfkey: Update priority calculation formula to the new one in kernel-netlink

Since the selectors are not exactly the same (no port masks, no interface)
some small tweaks have been applied.

1 files changed, 25 insertions, 14 deletions

diff --git a/src/libcharon/plugins/kernel_pfkey/kernel_pfkey_ipsec.c b/src/libcharon/plugins/kernel_pfkey/kernel_pfkey_ipsec.c
index 7eb6c5808..8de33d33e 100644
--- a/src/libcharon/plugins/kernel_pfkey/kernel_pfkey_ipsec.c
+++ b/src/libcharon/plugins/kernel_pfkey/kernel_pfkey_ipsec.c
@@ -141,8 +141,8 @@
 #define SOL_UDP IPPROTO_UDP
 #endif
 
-/** base priority for installed policies */
-#define PRIO_BASE 384
+/** Base priority for installed policies */
+#define PRIO_BASE 100000
 
 #ifdef __APPLE__
 /** from xnu/bsd/net/pfkeyv2.h */
@@ -590,33 +590,44 @@ static inline bool policy_entry_match_byindex(policy_entry_t *current,
 
 /**
  * Calculate the priority of a policy
+ *
+ * This is the same formula we use in the kernel-netlink interface, but some
+ * features are currently not or only partially supported by PF_KEY.
+ *
+ * bits 0-0:  reserved for interface restriction (0..1)     1 bit
+ * bits 1-6:  src + dst port mask bits (2 * 0..16)          6 bits
+ * bits 7-7:  restriction to protocol (0..1)                1 bit
+ * bits 8-16: src + dst network mask bits (2 * 0..128)      9 bits
+ *                                                         17 bits
+ *
+ * smallest value: 000000000 0 000000 0:      0, lowest priority = 100'000
+ * largest value : 100000000 1 100000 0: 65'728, highst priority =  34'272
  */
 static inline uint32_t get_priority(policy_entry_t *policy,
 									 policy_priority_t prio)
 {
 	uint32_t priority = PRIO_BASE;
+
 	switch (prio)
 	{
 		case POLICY_PRIORITY_FALLBACK:
-			priority <<= 1;
+			priority += PRIO_BASE;
 			/* fall-through */
 		case POLICY_PRIORITY_ROUTED:
-			priority <<= 1;
+			priority += PRIO_BASE;
 			/* fall-through */
 		case POLICY_PRIORITY_DEFAULT:
-			priority <<= 1;
-			/* fall-trough */
+			priority += PRIO_BASE;
+			/* fall-through */
 		case POLICY_PRIORITY_PASS:
 			break;
 	}
-	/* calculate priority based on selector size, small size = high prio */
-	priority -= policy->src.mask;
-	priority -= policy->dst.mask;
-	priority <<= 2; /* make some room for the two flags */
-	priority += policy->src.net->get_port(policy->src.net) ||
-				policy->dst.net->get_port(policy->dst.net) ?
-				0 : 2;
-	priority += policy->src.proto != IPSEC_PROTO_ANY ? 0 : 1;
+
+	/* calculate priority */
+	priority -= (policy->src.mask + policy->dst.mask) * 256;
+	priority -=  policy->src.proto != IPSEC_PROTO_ANY ? 128 : 0;
+	priority -= policy->src.net->get_port(policy->src.net) ? 32 : 0;
+	priority -= policy->dst.net->get_port(policy->dst.net) ? 32 : 0;
 	return priority;
 }