4222. [func] Bias IPv6 servers when selecting the next server to

query. [RT #40836]

CHANGES

@@ -1,3 +1,6 @@
+4222.	[func]		Bias IPv6 servers when selecting the next server to
+			query. [RT #40836]
+
 4221.	[bug]		Resource leak on DNS_R_NXDOMAIN in fctx_create.
 			[RT #40583]
 

bin/named/config.c

@@ -184,6 +184,7 @@ options {\n\
 	allow-new-zones no;\n\
 	fetches-per-server 0;\n\
 	require-server-cookie no;\n\
+	v6-bias 50;\n\
 "
 #ifdef HAVE_GEOIP
 "\

bin/named/server.c

@@ -3542,6 +3542,11 @@ configure_view(dns_view_t *view, dns_viewlist_t *viewlist,
 	INSIST(result == ISC_R_SUCCESS);
 	view->requireservercookie = cfg_obj_asboolean(obj);
 
+	obj = NULL;
+	result = ns_config_get(maps, "v6-bias", &obj);
+	INSIST(result == ISC_R_SUCCESS);
+	view->v6bias = cfg_obj_asuint32(obj) * 1000;
+
 	obj = NULL;
 	result = ns_config_get(maps, "max-clients-per-query", &obj);
 	INSIST(result == ISC_R_SUCCESS);

doc/arm/Bv9ARM-book.xml

@@ -5035,6 +5035,7 @@ badresp:1,adberr:0,findfail:0,valfail:0]
       <optional> min-ns-dots <replaceable>number</replaceable> </optional>
       <optional> qname-wait-recurse <replaceable>yes_or_no</replaceable> </optional>
     ; </optional>
+    <optional>v6-bias <replaceable>number</replaceable> ; </optional>
 };
 </programlisting>
 
@@ -9590,6 +9591,17 @@ avoid-v6-udp-ports { 40000; range 50000 60000; };
 		</para>
 	      </listitem>
 	    </varlistentry>
+
+	    <varlistentry>
+	      <term><command>v6-bias</command></term>
+	      <listitem>
+		<para>
+		  When determining the next nameserver to try
+		  preference IPv6 nameservers by this many milliseconds.
+		  The default is <literal>50</literal> milliseconds.
+		</para>
+	      </listitem>
+	    </varlistentry>
 	  </variablelist>
 
 	</sect3>

doc/misc/options

@@ -314,6 +314,7 @@ options {
         use-queryport-pool <boolean>; // obsolete
         use-v4-udp-ports { <portrange>; ... };
         use-v6-udp-ports { <portrange>; ... };
+        v6-bias <integer>;
         version ( <quoted_string> | none );
         zero-no-soa-ttl <boolean>;
         zero-no-soa-ttl-cache <boolean>;
@@ -587,6 +588,7 @@ view <string> [ <class> ] {
         update-check-ksk <boolean>;
         use-alt-transfer-source <boolean>;
         use-queryport-pool <boolean>; // obsolete
+        v6-bias <integer>;
         zero-no-soa-ttl <boolean>;
         zero-no-soa-ttl-cache <boolean>;
         zone <string> [ <class> ] {

lib/dns/include/dns/view.h

@@ -216,6 +216,7 @@ struct dns_view {
 	void				(*cfg_destroy)(void **);
 
 	unsigned char			secret[32];	/* Client secret */
+	unsigned int			v6bias;
 };
 
 #define DNS_VIEW_MAGIC			ISC_MAGIC('V','i','e','w')

lib/dns/resolver.c

@@ -2933,18 +2933,32 @@ add_bad(fetchctx_t *fctx, dns_adbaddrinfo_t *addrinfo, isc_result_t reason,
  * Sort addrinfo list by RTT.
  */
 static void
-sort_adbfind(dns_adbfind_t *find) {
+sort_adbfind(dns_adbfind_t *find, unsigned int bias) {
 	dns_adbaddrinfo_t *best, *curr;
 	dns_adbaddrinfolist_t sorted;
+	int family;
 
 	/* Lame N^2 bubble sort. */
 	ISC_LIST_INIT(sorted);
 	while (!ISC_LIST_EMPTY(find->list)) {
 		best = ISC_LIST_HEAD(find->list);
+		family = isc_sockaddr_pf(&best->sockaddr);
 		curr = ISC_LIST_NEXT(best, publink);
 		while (curr != NULL) {
-			if (curr->srtt < best->srtt)
+			if (isc_sockaddr_pf(&curr->sockaddr) == family) {
-				best = curr;
+				if (curr->srtt < best->srtt)
+					best = curr;
+			} else if (family == AF_INET6) {
+				if (curr->srtt + bias < best->srtt) {
+					best = curr;
+					family = AF_INET;
+				}
+			} else {
+				if (curr->srtt < best->srtt + bias) {
+					best = curr;
+					family = AF_INET6;
+				}
+			}
 			curr = ISC_LIST_NEXT(curr, publink);
 		}
 		ISC_LIST_UNLINK(find->list, best, publink);
@@ -2957,16 +2971,17 @@ sort_adbfind(dns_adbfind_t *find) {
  * Sort a list of finds by server RTT.
  */
 static void
-sort_finds(dns_adbfindlist_t *findlist) {
+sort_finds(dns_adbfindlist_t *findlist, unsigned int bias) {
 	dns_adbfind_t *best, *curr;
 	dns_adbfindlist_t sorted;
 	dns_adbaddrinfo_t *addrinfo, *bestaddrinfo;
+	int family;
 
 	/* Sort each find's addrinfo list by SRTT. */
 	for (curr = ISC_LIST_HEAD(*findlist);
 	     curr != NULL;
 	     curr = ISC_LIST_NEXT(curr, publink))
-		sort_adbfind(curr);
+		sort_adbfind(curr, bias);
 
 	/* Lame N^2 bubble sort. */
 	ISC_LIST_INIT(sorted);
@@ -2974,13 +2989,30 @@ sort_finds(dns_adbfindlist_t *findlist) {
 		best = ISC_LIST_HEAD(*findlist);
 		bestaddrinfo = ISC_LIST_HEAD(best->list);
 		INSIST(bestaddrinfo != NULL);
+		family = isc_sockaddr_pf(&bestaddrinfo->sockaddr);
 		curr = ISC_LIST_NEXT(best, publink);
 		while (curr != NULL) {
 			addrinfo = ISC_LIST_HEAD(curr->list);
 			INSIST(addrinfo != NULL);
-			if (addrinfo->srtt < bestaddrinfo->srtt) {
+			if (isc_sockaddr_pf(&addrinfo->sockaddr) == family) {
-				best = curr;
+				if (addrinfo->srtt < bestaddrinfo->srtt) {
-				bestaddrinfo = addrinfo;
+					best = curr;
+					bestaddrinfo = addrinfo;
+				}
+			} else if (family == AF_INET6) {
+				if (addrinfo->srtt + bias <
+				    bestaddrinfo->srtt) {
+					best = curr;
+					bestaddrinfo = addrinfo;
+					family = AF_INET;
+				}
+			} else {
+				if (addrinfo->srtt <
+				     bestaddrinfo->srtt + bias) {
+					best = curr;
+					bestaddrinfo = addrinfo;
+					family = AF_INET6;
+				}
 			}
 			curr = ISC_LIST_NEXT(curr, publink);
 		}
@@ -3394,8 +3426,8 @@ fctx_getaddresses(fetchctx_t *fctx, isc_boolean_t badcache) {
 		 * We've found some addresses.  We might still be looking
 		 * for more addresses.
 		 */
-		sort_finds(&fctx->finds);
+		sort_finds(&fctx->finds, res->view->v6bias);
-		sort_finds(&fctx->altfinds);
+		sort_finds(&fctx->altfinds, 0);
 		result = ISC_R_SUCCESS;
 	}
 

lib/dns/view.c

@@ -240,6 +240,7 @@ dns_view_create(isc_mem_t *mctx, dns_rdataclass_t rdclass,
 	view->cfg_destroy = NULL;
 	view->fail_ttl = 0;
 	view->failcache = NULL;
+	view->v6bias = 0;
 	dns_badcache_init(view->mctx, DNS_VIEW_FAILCACHESIZE, &view->failcache);
 
 	if (isc_bind9) {

lib/isccfg/namedconf.c

@@ -1578,6 +1578,18 @@ view_clauses[] = {
 	{ "fetch-quota-params", &cfg_type_fetchquota, 0 },
 	{ "fetches-per-server", &cfg_type_fetchesper, 0 },
 	{ "fetches-per-zone", &cfg_type_fetchesper, 0 },
+#ifdef ALLOW_FILTER_AAAA
+	{ "filter-aaaa", &cfg_type_bracketed_aml, 0 },
+	{ "filter-aaaa-on-v4", &cfg_type_filter_aaaa, 0 },
+	{ "filter-aaaa-on-v6", &cfg_type_filter_aaaa, 0 },
+#else
+	{ "filter-aaaa", &cfg_type_bracketed_aml,
+	   CFG_CLAUSEFLAG_NOTCONFIGURED },
+	{ "filter-aaaa-on-v4", &cfg_type_filter_aaaa,
+	   CFG_CLAUSEFLAG_NOTCONFIGURED },
+	{ "filter-aaaa-on-v6", &cfg_type_filter_aaaa,
+	   CFG_CLAUSEFLAG_NOTCONFIGURED },
+#endif
 	{ "ixfr-from-differences", &cfg_type_ixfrdifftype, 0 },
 	{ "lame-ttl", &cfg_type_ttlval, 0 },
 	{ "nocookie-udp-size", &cfg_type_uint32, 0 },
@@ -1608,11 +1620,13 @@ view_clauses[] = {
 	{ "queryport-pool-ports", &cfg_type_uint32, CFG_CLAUSEFLAG_OBSOLETE },
 	{ "queryport-pool-updateinterval", &cfg_type_uint32,
 	  CFG_CLAUSEFLAG_OBSOLETE },
+	{ "rate-limit", &cfg_type_rrl, 0 },
 	{ "recursion", &cfg_type_boolean, 0 },
 	{ "request-sit", &cfg_type_boolean, CFG_CLAUSEFLAG_OBSOLETE },
 	{ "request-nsid", &cfg_type_boolean, 0 },
 	{ "require-server-cookie", &cfg_type_boolean, 0 },
 	{ "resolver-query-timeout", &cfg_type_uint32, 0 },
+	{ "response-policy", &cfg_type_rpz, 0 },
 	{ "rfc2308-type1", &cfg_type_boolean, CFG_CLAUSEFLAG_NYI },
 	{ "root-delegation-only",  &cfg_type_optional_exclude, 0 },
 	{ "rrset-order", &cfg_type_rrsetorder, 0 },
@@ -1623,21 +1637,8 @@ view_clauses[] = {
 	{ "topology", &cfg_type_bracketed_aml, CFG_CLAUSEFLAG_NOTIMP },
 	{ "transfer-format", &cfg_type_transferformat, 0 },
 	{ "use-queryport-pool", &cfg_type_boolean, CFG_CLAUSEFLAG_OBSOLETE },
+	{ "v6-bias", &cfg_type_uint32, 0 },
 	{ "zero-no-soa-ttl-cache", &cfg_type_boolean, 0 },
-#ifdef ALLOW_FILTER_AAAA
-	{ "filter-aaaa", &cfg_type_bracketed_aml, 0 },
-	{ "filter-aaaa-on-v4", &cfg_type_filter_aaaa, 0 },
-	{ "filter-aaaa-on-v6", &cfg_type_filter_aaaa, 0 },
-#else
-	{ "filter-aaaa", &cfg_type_bracketed_aml,
-	   CFG_CLAUSEFLAG_NOTCONFIGURED },
-	{ "filter-aaaa-on-v4", &cfg_type_filter_aaaa,
-	   CFG_CLAUSEFLAG_NOTCONFIGURED },
-	{ "filter-aaaa-on-v6", &cfg_type_filter_aaaa,
-	   CFG_CLAUSEFLAG_NOTCONFIGURED },
-#endif
-	{ "response-policy", &cfg_type_rpz, 0 },
-	{ "rate-limit", &cfg_type_rrl, 0 },
 	{ NULL, NULL, 0 }
 };
 
@@ -1815,8 +1816,11 @@ view_clausesets[] = {
 	zone_clauses,
 	NULL
 };
+
 static cfg_type_t cfg_type_viewopts = {
-	"view", cfg_parse_map, cfg_print_map, cfg_doc_map, &cfg_rep_map, view_clausesets };
+	"view", cfg_parse_map, cfg_print_map, cfg_doc_map, &cfg_rep_map,
+	view_clausesets
+};
 
 /*% The "zone" statement syntax. */