Try to detect Windows Clients by looking for INTERNAL_IP4/6_SERVER attribute

src/libcharon/sa/ike_sa.h

@@ -97,6 +97,11 @@ enum ike_extension_t {
 	 * peer supports EAP-only authentication, draft-eronen-ipsec-ikev2-eap-auth
 	 */
 	EXT_EAP_ONLY_AUTHENTICATION = (1<<5),
+
+	/**
+	 * peer is probably a Windows 7 RAS client
+	 */
+	EXT_MS_WINDOWS = (1<<6),
 };
 
 /**

src/libcharon/sa/tasks/ike_config.c

@@ -174,6 +174,11 @@ static void process_attribute(private_ike_config_t *this,
 			}
 			break;
 		}
+		case INTERNAL_IP4_SERVER:
+		case INTERNAL_IP6_SERVER:
+			/* assume it's a Windows client if we see proprietary attributes */
+			this->ike_sa->enable_extension(this->ike_sa, EXT_MS_WINDOWS);
+			/* fall */
 		default:
 		{
 			if (this->initiator)