Add ClientQuota statistics channel counter

This counter indicates the number of the resolver's spilled
queries due to reaching the clients per query quota.

bin/named/statschannel.c

@@ -464,6 +464,8 @@ init_desc(void) {
 	SET_RESSTATDESC(zonequota, "spilled due to zone quota", "ZoneQuota");
 	SET_RESSTATDESC(serverquota, "spilled due to server quota",
 			"ServerQuota");
+	SET_RESSTATDESC(clientquota, "spilled due to clients per query quota",
+			"ClientQuota");
 	SET_RESSTATDESC(nextitem, "waited for next item", "NextItem");
 	SET_RESSTATDESC(priming, "priming queries", "Priming");
 

lib/dns/include/dns/stats.h

@@ -71,9 +71,10 @@ enum {
 	dns_resstatscounter_badcookie = 40,
 	dns_resstatscounter_zonequota = 41,
 	dns_resstatscounter_serverquota = 42,
-	dns_resstatscounter_nextitem = 43,
-	dns_resstatscounter_priming = 44,
-	dns_resstatscounter_max = 45,
+	dns_resstatscounter_clientquota = 43,
+	dns_resstatscounter_nextitem = 44,
+	dns_resstatscounter_priming = 45,
+	dns_resstatscounter_max = 46,
 
 	/*
 	 * DNSSEC stats.

lib/dns/resolver.c

@@ -10399,6 +10399,7 @@ dns_resolver_createfetch(dns_resolver_t *res, const dns_name_t *name,
 				fctx->spilled = true;
 			}
 			if (fctx->spilled) {
+				inc_stats(res, dns_resstatscounter_clientquota);
 				result = DNS_R_DROP;
 				goto unlock;
 			}