daemon/worker: retransmit based on current score

if the score is known (and not glued), the retry
rate is <avg(rtt), 250ms>

if the NS score is unknown or worse than 250ms,
it is always retried at this rate

all other servers in the list use default rate

daemon/worker.c

@@ -745,9 +745,21 @@ static int qr_task_step(struct qr_task *task, const struct sockaddr *packet_sour
 		if (subreq_enqueue(task)) {
 			return kr_ok(); /* Will be notified when outgoing query finishes. */
 		}
+		/* Check current query NSLIST */
+		struct kr_query *qry = array_tail(task->req.rplan.pending);
 		/* Start transmitting */
 		if (retransmit(task)) {
-			ret = timer_start(task, on_retransmit, KR_CONN_RETRY, 0);
+			assert(qry != NULL);
+			/* Retransmit at default interval, or more frequently if the mean
+			 * RTT of the server is better. If the server is glued, use default rate. */
+			size_t timeout = qry->ns.score;
+			if (timeout > KR_NS_GLUED) {
+				/* We don't have information about variance in RTT, expect +10ms */
+				timeout = MIN(qry->ns.score + 10, KR_CONN_RETRY);
+			} else {
+				timeout = KR_CONN_RETRY;
+			}
+			ret = timer_start(task, on_retransmit, timeout, 0);
 		} else {
 			return qr_task_step(task, NULL, NULL);
 		}

lib/defines.h

@@ -51,7 +51,7 @@ static inline int __attribute__((__cold__)) kr_error(int x) {
  * @cond internal
  */
 #define KR_CONN_RTT_MAX 3000 /* Timeout for network activity */
-#define KR_CONN_RETRY 300    /* Retry interval for network activity */
+#define KR_CONN_RETRY 250    /* Retry interval for network activity */
 #define KR_ITER_LIMIT 50     /* Built-in iterator limit */
 #define KR_CNAME_CHAIN_LIMIT 40 /* Built-in maximum CNAME chain length */
 #define KR_TIMEOUT_LIMIT 4   /* Maximum number of retries after timeout. */