Expose the incoming transfers' rates in the statistics channel

Expose the average transfer rate (in bytes-per-second) during the
last full 'min-transfer-rate-in <bytes> <minutes>' minutes interval.
If no such interval has passed yet, then the overall average rate is
reported instead.

bin/named/bind9.xsl

@@ -931,6 +931,7 @@
                   <th>Messages Received</th>
                   <th>Records Received</th>
                   <th>Bytes Received</th>
+                  <th>Transfer Rate (B/s)</th>
                 </tr>
               </thead>
               <tbody>
@@ -959,6 +960,7 @@
                     <td><xsl:value-of select="nmsg"/></td>
                     <td><xsl:value-of select="nrecs"/></td>
                     <td><xsl:value-of select="nbytes"/></td>
+                    <td><xsl:value-of select="rate"/></td>
                   </tr>
                 </xsl:for-each>
               </tbody>

bin/named/statschannel.c

@@ -1488,6 +1488,7 @@ xfrin_xmlrender(dns_zone_t *zone, void *arg) {
 	unsigned int nmsg = 0;
 	unsigned int nrecs = 0;
 	uint64_t nbytes = 0;
+	uint64_t rate = 0;
 
 	statlevel = dns_zone_getstatlevel(zone);
 	if (statlevel == dns_zonestat_none) {
@@ -1701,7 +1702,7 @@ xfrin_xmlrender(dns_zone_t *zone, void *arg) {
 	TRY0(xmlTextWriterEndElement(writer));
 
 	if (is_running) {
-		dns_xfrin_getstats(xfr, &nmsg, &nrecs, &nbytes);
+		dns_xfrin_getstats(xfr, &nmsg, &nrecs, &nbytes, &rate);
 	}
 	TRY0(xmlTextWriterStartElement(writer, ISC_XMLCHAR "nmsg"));
 	TRY0(xmlTextWriterWriteFormatString(writer, "%u", nmsg));
@@ -1712,6 +1713,9 @@ xfrin_xmlrender(dns_zone_t *zone, void *arg) {
 	TRY0(xmlTextWriterStartElement(writer, ISC_XMLCHAR "nbytes"));
 	TRY0(xmlTextWriterWriteFormatString(writer, "%" PRIu64, nbytes));
 	TRY0(xmlTextWriterEndElement(writer));
+	TRY0(xmlTextWriterStartElement(writer, ISC_XMLCHAR "rate"));
+	TRY0(xmlTextWriterWriteFormatString(writer, "%" PRIu64, rate));
+	TRY0(xmlTextWriterEndElement(writer));
 
 	TRY0(xmlTextWriterStartElement(writer, ISC_XMLCHAR "ixfr"));
 	if (is_running && is_first_data_received) {
@@ -2559,6 +2563,7 @@ xfrin_jsonrender(dns_zone_t *zone, void *arg) {
 	unsigned int nmsg = 0;
 	unsigned int nrecs = 0;
 	uint64_t nbytes = 0;
+	uint64_t rate = 0;
 
 	statlevel = dns_zone_getstatlevel(zone);
 	if (statlevel == dns_zonestat_none) {
@@ -2756,7 +2761,7 @@ xfrin_jsonrender(dns_zone_t *zone, void *arg) {
 	}
 
 	if (is_running) {
-		dns_xfrin_getstats(xfr, &nmsg, &nrecs, &nbytes);
+		dns_xfrin_getstats(xfr, &nmsg, &nrecs, &nbytes, &rate);
 	}
 	json_object_object_add(xfrinobj, "nmsg",
 			       json_object_new_int64((int64_t)nmsg));
@@ -2766,6 +2771,10 @@ xfrin_jsonrender(dns_zone_t *zone, void *arg) {
 		xfrinobj, "nbytes",
 		json_object_new_int64(nbytes > INT64_MAX ? INT64_MAX
 							 : (int64_t)nbytes));
+	json_object_object_add(xfrinobj, "rate",
+			       json_object_new_int64(rate > INT64_MAX
+							     ? INT64_MAX
+							     : (int64_t)rate));
 
 	if (is_running && is_first_data_received) {
 		json_object_object_add(

doc/arm/reference.rst

@@ -7835,6 +7835,12 @@ Incoming Zone Transfers
       64-bit unsigned Integer. This is the number of usable bytes
       of DNS data. It does not include transport overhead.
 
+   ``Transfer Rate (B/s)`` (``rate``)
+      64 bit unsigned Integer. This is the average zone transfer rate in
+      bytes-per-second during the latest full interval that is configured by the
+      :any:`min-transfer-rate-in` configuration option. If no such interval
+      has passed yet, then the overall average rate is reported instead.
+
    .. note::
       Depending on the current state of the transfer, some of the
       values may be empty or set to ``-`` (meaning "not available").

lib/dns/include/dns/xfrin.h

@@ -140,10 +140,13 @@ dns_xfrin_getendserial(dns_xfrin_t *xfr);
 
 void
 dns_xfrin_getstats(dns_xfrin_t *xfr, unsigned int *nmsgp, unsigned int *nrecsp,
-		   uint64_t *nbytesp);
+		   uint64_t *nbytesp, uint64_t *ratep);
 /*%<
  * Get various statistics values of the xfrin object: number of the received
- * messages, number of the received records, number of the received bytes.
+ * messages, number of the received records, number of the received bytes,
+ * and the average transfer rate (in bytes-per-second) during the last full
+ * 'min-transfer-rate-in <bytes> <minutes>' minutes interval. If no such
+ * interval has passed yet, then the overall average rate is reported instead.
  *
  * Requires:
  *\li	'xfr' is a valid dns_xfrin_t.

lib/dns/xfrin.c

@@ -154,6 +154,7 @@ struct dns_xfrin {
 	atomic_uint nrecs;	     /*%< Number of records recvd */
 	atomic_uint_fast64_t nbytes; /*%< Number of bytes received */
 	_Atomic(isc_time_t) start;   /*%< Start time of the transfer */
+	atomic_uint_fast64_t rate_bytes_per_second;
 	_Atomic(dns_transport_type_t) soa_transport_type;
 	atomic_uint_fast32_t end_serial;
 
@@ -975,13 +976,21 @@ xfrin_minratecheck(void *arg) {
 
 	const uint64_t nbytes = atomic_load_relaxed(&xfr->nbytes);
 	const uint64_t min = dns_zone_getminxfrratebytesin(xfr->zone);
+	uint64_t rate = nbytes - xfr->nbytes_saved;
 
-	if (nbytes - xfr->nbytes_saved < min) {
+	if (rate < min) {
 		isc_timer_stop(xfr->min_rate_timer);
 		xfrin_fail(xfr, ISC_R_TIMEDOUT,
 			   "minimum transfer rate reached");
 	} else {
 		xfr->nbytes_saved = nbytes;
+
+		/*
+		 * Calculate and store for the statistics channel the transfer
+		 * rate in bytes-per-second for the latest interval.
+		 */
+		rate /= dns_zone_getminxfrratesecondsin(xfr->zone);
+		atomic_store_relaxed(&xfr->rate_bytes_per_second, rate);
 	}
 }
 
@@ -1046,13 +1055,29 @@ dns_xfrin_getendserial(dns_xfrin_t *xfr) {
 
 void
 dns_xfrin_getstats(dns_xfrin_t *xfr, unsigned int *nmsgp, unsigned int *nrecsp,
-		   uint64_t *nbytesp) {
+		   uint64_t *nbytesp, uint64_t *ratep) {
 	REQUIRE(VALID_XFRIN(xfr));
 	REQUIRE(nmsgp != NULL && nrecsp != NULL && nbytesp != NULL);
 
+	uint64_t rate = atomic_load_relaxed(&xfr->rate_bytes_per_second);
+	if (rate == 0) {
+		/*
+		 * Likely the first 'min-transfer-rate-in <bytes> <minutes>'
+		 * minutes interval hasn't passed yet. Calculate the overall
+		 * average transfer rate instead.
+		 */
+		isc_time_t now = isc_time_now();
+		isc_time_t start = atomic_load_relaxed(&xfr->start);
+		uint64_t sec = isc_time_microdiff(&now, &start) / US_PER_SEC;
+		if (sec > 0) {
+			rate = atomic_load_relaxed(&xfr->nbytes) / sec;
+		}
+	}
+
 	SET_IF_NOT_NULL(nmsgp, atomic_load_relaxed(&xfr->nmsg));
 	SET_IF_NOT_NULL(nrecsp, atomic_load_relaxed(&xfr->nrecs));
 	SET_IF_NOT_NULL(nbytesp, atomic_load_relaxed(&xfr->nbytes));
+	SET_IF_NOT_NULL(ratep, rate);
 }
 
 const isc_sockaddr_t *