- low-rtt and low-rtt-pct in unbound.conf enable the server selection

of fast servers for some percentage of the time.


git-svn-id: file:///svn/unbound/trunk@4612 be551aaa-1e26-0410-a405-d3ace91eadb9

doc/Changelog

@@ -6,6 +6,8 @@
 	  answer and fallback is enabled.
 	- Accept both option names with and without colon for get_option
 	  and set_option.
+	- low-rtt and low-rtt-pct in unbound.conf enable the server selection
+	  of fast servers for some percentage of the time.
 
 5 April 2018: Wouter
 	- Combine write of tcp length and tcp query for dns over tls.

doc/example.conf.in

@@ -718,6 +718,12 @@ server:
 	# 0 blocks when ip is ratelimited, otherwise let 1/xth traffic through
 	# ip-ratelimit-factor: 10
 
+	# what is considered a low rtt (ping time for upstream server), in msec
+	# low-rtt: 45
+	# select low rtt this many times out of 1000. 0 means the fast server
+	# select is disabled.  prefetches are not sped up.
+	# low-rtt-pct: 0
+
 	# Specific options for ipsecmod. unbound needs to be configured with
 	# --enable-ipsecmod for these to take effect.
 	#

iterator/iter_utils.c

@@ -312,9 +312,9 @@ static int
 iter_filter_order(struct iter_env* iter_env, struct module_env* env,
 	uint8_t* name, size_t namelen, uint16_t qtype, time_t now, 
 	struct delegpt* dp, int* selected_rtt, int open_target, 
-	struct sock_list* blacklist)
+	struct sock_list* blacklist, time_t prefetch)
 {
-	int got_num = 0, low_rtt = 0, swap_to_front;
+	int got_num = 0, low_rtt = 0, swap_to_front, rtt_band = RTT_BAND;
 	struct delegpt_addr* a, *n, *prev=NULL;
 
 	/* fillup sel_rtt and find best rtt in the bunch */
@@ -329,6 +329,16 @@ iter_filter_order(struct iter_env* iter_env, struct module_env* env,
 			     return 0 to force the caller to fetch more */
 	}
 
+	if(env->cfg->low_rtt_pct != 0 && prefetch == 0 &&
+		low_rtt < env->cfg->low_rtt &&
+		ub_random_max(env->rnd, 1000) < env->cfg->low_rtt_pct) {
+		/* the query is not prefetch, but for a downstream client,
+		 * there is a low_rtt (fast) server.  We choose that x% of the
+		 * time */
+		/* pick rtt numbers from 0..LOWBAND_RTT */
+		rtt_band = env->cfg->low_rtt - low_rtt;
+	}
+
 	got_num = 0;
 	a = dp->result_list;
 	while(a) {
@@ -340,10 +350,10 @@ iter_filter_order(struct iter_env* iter_env, struct module_env* env,
 		}
 		/* classify the server address and determine what to do */
 		swap_to_front = 0;
-		if(a->sel_rtt >= low_rtt && a->sel_rtt - low_rtt <= RTT_BAND) {
+		if(a->sel_rtt >= low_rtt && a->sel_rtt - low_rtt <= rtt_band) {
 			got_num++;
 			swap_to_front = 1;
-		} else if(a->sel_rtt<low_rtt && low_rtt-a->sel_rtt<=RTT_BAND) {
+		} else if(a->sel_rtt<low_rtt && low_rtt-a->sel_rtt<=rtt_band) {
 			got_num++;
 			swap_to_front = 1;
 		}
@@ -400,13 +410,14 @@ struct delegpt_addr*
 iter_server_selection(struct iter_env* iter_env, 
 	struct module_env* env, struct delegpt* dp, 
 	uint8_t* name, size_t namelen, uint16_t qtype, int* dnssec_lame,
-	int* chase_to_rd, int open_target, struct sock_list* blacklist)
+	int* chase_to_rd, int open_target, struct sock_list* blacklist,
+	time_t prefetch)
 {
 	int sel;
 	int selrtt;
 	struct delegpt_addr* a, *prev;
 	int num = iter_filter_order(iter_env, env, name, namelen, qtype,
-		*env->now, dp, &selrtt, open_target, blacklist);
+		*env->now, dp, &selrtt, open_target, blacklist, prefetch);
 
 	if(num == 0)
 		return NULL;

iterator/iter_utils.h

@@ -87,13 +87,18 @@ int iter_apply_cfg(struct iter_env* iter_env, struct config_file* cfg);
  * @param open_target: number of currently outstanding target queries.
  * 	If we wait for these, perhaps more server addresses become available.
  * @param blacklist: the IP blacklist to use.
+ * @param prefetch: if not 0, prefetch is in use for this query.
+ * 	This means the query can have different timing, because prefetch is
+ * 	not waited upon by the downstream client, and thus a good time to
+ * 	perform exploration of other targets.
  * @return best target or NULL if no target.
  *	if not null, that target is removed from the result list in the dp.
  */
 struct delegpt_addr* iter_server_selection(struct iter_env* iter_env, 
 	struct module_env* env, struct delegpt* dp, uint8_t* name, 
 	size_t namelen, uint16_t qtype, int* dnssec_lame,
-	int* chase_to_rd, int open_target, struct sock_list* blacklist);
+	int* chase_to_rd, int open_target, struct sock_list* blacklist,
+	time_t prefetch);
 
 /**
  * Allocate dns_msg from parsed msg, in regional.

iterator/iterator.c

@@ -2268,7 +2268,8 @@ processQueryTargets(struct module_qstate* qstate, struct iter_qstate* iq,
 	target = iter_server_selection(ie, qstate->env, iq->dp, 
 		iq->dp->name, iq->dp->namelen, iq->qchase.qtype,
 		&iq->dnssec_lame_query, &iq->chase_to_rd, 
-		iq->num_target_queries, qstate->blacklist);
+		iq->num_target_queries, qstate->blacklist,
+		qstate->prefetch_leeway);
 
 	/* If no usable target was selected... */
 	if(!target) {

util/config_file.c

@@ -161,6 +161,8 @@ config_create(void)
 	if(!(cfg->logfile = strdup(""))) goto error_exit;
 	if(!(cfg->pidfile = strdup(PIDFILE))) goto error_exit;
 	if(!(cfg->target_fetch_policy = strdup("3 2 1 0 0"))) goto error_exit;
+	cfg->low_rtt_pct = 0;
+	cfg->low_rtt = 45;
 	cfg->donotqueryaddrs = NULL;
 	cfg->donotquery_localhost = 1;
 	cfg->root_hints = NULL;

util/config_file.h

@@ -143,6 +143,10 @@ struct config_file {
 
 	/** the target fetch policy for the iterator */
 	char* target_fetch_policy;
+	/** percent*10, how many times in 1000 to pick low rtt destinations */
+	int low_rtt_pct;
+	/** what time in msec is a low rtt destination */
+	int low_rtt;
 
 	/** automatic interface for incoming messages. Uses ipv6 remapping,
 	 * and recvmsg/sendmsg ancillary data to detect interfaces, boolean */

util/configlexer.lex

@@ -425,6 +425,8 @@ ratelimit-for-domain{COLON}	{ YDVAR(2, VAR_RATELIMIT_FOR_DOMAIN) }
 ratelimit-below-domain{COLON}	{ YDVAR(2, VAR_RATELIMIT_BELOW_DOMAIN) }
 ip-ratelimit-factor{COLON}		{ YDVAR(1, VAR_IP_RATELIMIT_FACTOR) }
 ratelimit-factor{COLON}		{ YDVAR(1, VAR_RATELIMIT_FACTOR) }
+low-rtt{COLON}			{ YDVAR(1, VAR_LOW_RTT) }
+low-rtt-pct{COLON}		{ YDVAR(1, VAR_LOW_RTT_PCT) }
 response-ip-tag{COLON}		{ YDVAR(2, VAR_RESPONSE_IP_TAG) }
 response-ip{COLON}		{ YDVAR(2, VAR_RESPONSE_IP) }
 response-ip-data{COLON}		{ YDVAR(2, VAR_RESPONSE_IP_DATA) }

util/configparser.h

@@ -279,7 +279,9 @@ extern int yydebug;
     VAR_URL = 489,
     VAR_FOR_DOWNSTREAM = 490,
     VAR_FALLBACK_ENABLED = 491,
-    VAR_ADDITIONAL_TLS_PORT = 492
+    VAR_ADDITIONAL_TLS_PORT = 492,
+    VAR_LOW_RTT = 493,
+    VAR_LOW_RTT_PCT = 494
   };
 #endif
 /* Tokens.  */
@@ -518,6 +520,8 @@ extern int yydebug;
 #define VAR_FOR_DOWNSTREAM 490
 #define VAR_FALLBACK_ENABLED 491
 #define VAR_ADDITIONAL_TLS_PORT 492
+#define VAR_LOW_RTT 493
+#define VAR_LOW_RTT_PCT 494
 
 /* Value type.  */
 #if ! defined YYSTYPE && ! defined YYSTYPE_IS_DECLARED
@@ -528,7 +532,7 @@ union YYSTYPE
 
 	char*	str;
 
-#line 532 "util/configparser.h" /* yacc.c:1909  */
+#line 536 "util/configparser.h" /* yacc.c:1909  */
 };
 
 typedef union YYSTYPE YYSTYPE;

util/configparser.y

@@ -155,7 +155,7 @@ extern struct config_parser_state* cfg_parser;
 %token VAR_CACHEDB_REDISHOST VAR_CACHEDB_REDISPORT VAR_CACHEDB_REDISTIMEOUT
 %token VAR_UDP_UPSTREAM_WITHOUT_DOWNSTREAM VAR_FOR_UPSTREAM
 %token VAR_AUTH_ZONE VAR_ZONEFILE VAR_MASTER VAR_URL VAR_FOR_DOWNSTREAM
-%token VAR_FALLBACK_ENABLED VAR_ADDITIONAL_TLS_PORT
+%token VAR_FALLBACK_ENABLED VAR_ADDITIONAL_TLS_PORT VAR_LOW_RTT VAR_LOW_RTT_PCT
 
 %%
 toplevelvars: /* empty */ | toplevelvars toplevelvar ;
@@ -245,7 +245,8 @@ content_server: server_num_threads | server_verbosity | server_port |
 	server_ipsecmod_ignore_bogus | server_ipsecmod_max_ttl |
 	server_ipsecmod_whitelist | server_ipsecmod_strict |
 	server_udp_upstream_without_downstream | server_aggressive_nsec |
-	server_tls_cert_bundle | server_additional_tls_port
+	server_tls_cert_bundle | server_additional_tls_port | server_low_rtt |
+	server_low_rtt_pct
 	;
 stubstart: VAR_STUB_ZONE
 	{
@@ -1860,6 +1861,24 @@ server_ratelimit_factor: VAR_RATELIMIT_FACTOR STRING_ARG
 		free($2);
 	}
 	;
+server_low_rtt: VAR_LOW_RTT STRING_ARG 
+	{ 
+		OUTYY(("P(server_low_rtt:%s)\n", $2)); 
+		if(atoi($2) == 0 && strcmp($2, "0") != 0)
+			yyerror("number expected");
+		else cfg_parser->cfg->low_rtt = atoi($2);
+		free($2);
+	}
+	;
+server_low_rtt_pct: VAR_LOW_RTT_PCT STRING_ARG 
+	{ 
+		OUTYY(("P(server_low_rtt_pct:%s)\n", $2)); 
+		if(atoi($2) == 0 && strcmp($2, "0") != 0)
+			yyerror("number expected");
+		else cfg_parser->cfg->low_rtt_pct = atoi($2);
+		free($2);
+	}
+	;
 server_qname_minimisation: VAR_QNAME_MINIMISATION STRING_ARG
 	{
 		OUTYY(("P(server_qname_minimisation:%s)\n", $2));