Don't query the policy usetime if there was no traffic on the SA.

This helps in cases where a policy is assigned to more than one SA. That
is, SAs now should have different usetimes even if they use the same policy.

src/charon/sa/child_sa.c

@@ -374,6 +374,58 @@ static enumerator_t* create_policy_enumerator(private_child_sa_t *this)
 	return &e->public;
 }
 
+/**
+ * update the cached usebytes
+ * returns SUCCESS if the usebytes have changed, FAILED if not or no SPIs
+ * are available, and NOT_SUPPORTED if the kernel interface does not support
+ * quering the usebytes.
+ */
+static bool update_usebytes(private_child_sa_t *this, bool inbound)
+{
+	status_t status = FAILED;
+	u_int64_t bytes;
+	
+	if (inbound)
+	{
+		if (this->my_spi)
+		{
+			status = charon->kernel_interface->query_sa(
+									charon->kernel_interface,
+									this->other_addr, this->my_addr,
+									this->my_spi, this->protocol, &bytes);
+			if (status == SUCCESS)
+			{
+				if (bytes > this->my_usebytes)
+				{
+					this->my_usebytes = bytes;
+					return SUCCESS;
+				}
+				return FAILED;
+			}
+		}
+	}
+	else
+	{
+		if (this->other_spi)
+		{
+			status = charon->kernel_interface->query_sa(
+									charon->kernel_interface,
+									this->my_addr, this->other_addr,
+									this->other_spi, this->protocol, &bytes);
+			if (status == SUCCESS)
+			{
+				if (bytes > this->other_usebytes)
+				{
+					this->other_usebytes = bytes;
+					return SUCCESS;
+				}
+				return FAILED;
+			}
+		}
+	}
+	return status;
+}
+
 /**
  * Implementation of child_sa_t.get_usetime
  */
@@ -383,6 +435,11 @@ static u_int32_t get_usetime(private_child_sa_t *this, bool inbound)
 	traffic_selector_t *my_ts, *other_ts;
 	u_int32_t last_use = 0;
 	
+	if (update_usebytes(this, inbound) == FAILED)
+	{	/* no SPI or no traffic since last update */
+		return inbound ? this->my_usetime : this->other_usetime;
+	}
+	
 	enumerator = create_policy_enumerator(this);
 	while (enumerator->enumerate(enumerator, &my_ts, &other_ts))
 	{
@@ -430,37 +487,8 @@ static u_int32_t get_usetime(private_child_sa_t *this, bool inbound)
  */
 static u_int64_t get_usebytes(private_child_sa_t *this, bool inbound)
 {
-	status_t status;
+	update_usebytes(this, inbound);
-	u_int64_t bytes;
+	return inbound ? this->my_usebytes : this->other_usebytes;
-
-	if (inbound)
-	{
-		if (this->my_spi)
-		{
-			status = charon->kernel_interface->query_sa(charon->kernel_interface,
-									this->other_addr, this->my_addr,
-									this->my_spi, this->protocol, &bytes);
-			if (status == SUCCESS && bytes > this->my_usebytes)
-			{
-				this->my_usebytes = bytes;
-			}
-		}
-		return this->my_usebytes;
-	}
-	else
-	{
-		if (this->other_spi)
-		{
-			status = charon->kernel_interface->query_sa(charon->kernel_interface,
-									this->my_addr, this->other_addr,
-						 			this->other_spi, this->protocol, &bytes);
-			if (status == SUCCESS && bytes > this->other_usebytes)
-			{
-				this->other_usebytes = bytes;
-			}
-		}
-		return this->other_usebytes;
-	}
 }
 
 /**