ikev1: Ensure DPD_ACK is sent in time

If a lot of QUICK_MODE tasks are queued and the other side
sends a DPD request, there is a good chance for timeouts.

Observed this in cases where other side is quite slow in responding
QUICK_MODE requests (e.g. Cisco ASA v8.x) and about 100 CHILD_SAs
are to be spawned.

Closes strongswan/strongswan#115.

Author: Afschin Hormozdiary

src/libcharon/sa/ikev1/task_manager_v1.c

@@ -544,20 +544,20 @@ METHOD(task_manager_t, initiate, status_t,
 					new_mid = TRUE;
 					break;
 				}
-				if (!mode_config_expected(this) &&
-					activate_task(this, TASK_QUICK_MODE))
+				if (activate_task(this, TASK_ISAKMP_DPD))
 				{
-					exchange = QUICK_MODE;
+					exchange = INFORMATIONAL_V1;
 					new_mid = TRUE;
 					break;
 				}
-				if (activate_task(this, TASK_INFORMATIONAL))
+				if (!mode_config_expected(this) &&
+					activate_task(this, TASK_QUICK_MODE))
 				{
-					exchange = INFORMATIONAL_V1;
+					exchange = QUICK_MODE;
 					new_mid = TRUE;
 					break;
 				}
-				if (activate_task(this, TASK_ISAKMP_DPD))
+				if (activate_task(this, TASK_INFORMATIONAL))
 				{
 					exchange = INFORMATIONAL_V1;
 					new_mid = TRUE;