- Add fast-server-permil and fast-server-num options.

- Deprecate low-rtt and low-rtt-permil options.


git-svn-id: file:///svn/unbound/trunk@4938 be551aaa-1e26-0410-a405-d3ace91eadb9

doc/Changelog

@@ -1,3 +1,7 @@
+8 October 2018: Ralph
+	- Add fast-server-permil and fast-server-num options.
+	- Deprecate low-rtt and low-rtt-permil options.
+
 8 October 2018: Wouter
 	- Squelch log of failed to tcp initiate after TCP Fastopen failure.
 

doc/example.conf.in

@@ -757,12 +757,12 @@ server:
 	# Limit the number of connections simultaneous from a netblock
 	# tcp-connection-limit: 192.0.2.0/24 12
 
-	# 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-permil: 0
-
+	# select from the fastest servers this many times out of 1000. 0 means
+	# the fast server select is disabled. prefetches are not sped up.
+	# fast-server-permil: 0
+	# the number of servers that will be used in the fast server selection.
+	# fast-server-num: 4
+	
 	# Specific options for ipsecmod. unbound needs to be configured with
 	# --enable-ipsecmod for these to take effect.
 	#

doc/unbound.conf.5.in

@@ -1391,22 +1391,20 @@ This can make ordinary queries complete (if repeatedly queried for),
 and enter the cache, whilst also mitigating the traffic flow by the
 factor given.
 .TP 5
-.B low\-rtt: \fI<msec time>
-Set the time in millisecond that is considere a low ping time for fast
-server selection with the low\-rtt\-permil option, that turns this on or off.
-The default is 45 msec, a number from IPv6 quick response documents.
+.B fast\-server\-permil: \fI<number>
+Specify how many times out of 1000 to pick from the set of fastest servers.
+0 turns the feature off.  A value of 900 would pick from the fastest
+servers 90 percent of the time, and would perform normal exploration of random
+servers for the remaining time. When prefetch is enabled (or serve\-expired),
+such prefetches are not sped up, because there is no one waiting for it, and it
+presents a good moment to perform server exploration. The
+\fBfast\-server\-num\fR option can be used to specify the size of the fastest
+servers set. The default for fast\-server\-permil is 0.
 .TP 5
-.B low\-rtt\-permil: \fI<number>
-Specify how many times out of 1000 to pick the fast server from the low
-rtt band.  0 turns the feature off.  A value of 900 would pick the fast
-server when such fast servers are available 90 percent of the time, and
-the remaining time perform normal exploration of random servers.
-When prefetch is enabled (or serve\-expired), such prefetches are not
-sped up, because there is no one waiting for it, and it presents a good
-moment to perform server exploration.  The low\-rtt option can be used
-to specify which servers are picked for fast server selection, servers
-with a ping roundtrip time below that value are considered.
-The default for low\-rtt\-permil is 0.
+.B fast\-server\-num: \fI<number>
+Set the number of servers that should be used for fast server selection. Only
+use the fastest specified number of servers with the fast\-server\-permil
+option, that turns this on or off. The default is to use the fastest 4 servers.
 .SS "Remote Control Options"
 In the
 .B remote\-control:

iterator/iter_utils.c

@@ -282,10 +282,13 @@ iter_filter_unsuitable(struct iter_env* iter_env, struct module_env* env,
 static int
 iter_fill_rtt(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* best_rtt, struct sock_list* blacklist)
+	struct delegpt* dp, int* best_rtt, struct sock_list* blacklist,
+	int* num_suitable_results)
 {
 	int got_it = 0;
 	struct delegpt_addr* a;
+	*num_suitable_results = 0;
+
 	if(dp->bogus)
 		return 0; /* NS bogus, all bogus, nothing found */
 	for(a=dp->result_list; a; a = a->next_result) {
@@ -301,11 +304,57 @@ iter_fill_rtt(struct iter_env* iter_env, struct module_env* env,
 			} else if(a->sel_rtt < *best_rtt) {
 				*best_rtt = a->sel_rtt;
 			}
+			(*num_suitable_results)++;
 		}
 	}
 	return got_it;
 }
 
+/** compare two rtts, return -1, 0 or 1 */
+static int
+rtt_compare(const void* x, const void* y)
+{
+	if(*(int*)x == *(int*)y)
+		return 0;
+	if(*(int*)x > *(int*)y)
+		return 1;
+	return -1;
+}
+
+/** get RTT for the Nth fastest server */
+static int
+nth_rtt(struct delegpt_addr* result_list, int num_results, int n)
+{
+	int rtt_band, i;
+	int* rtt_list, *rtt_index;
+	
+	if(num_results < 1 || n >= num_results) {
+		return -1;
+	}
+
+	rtt_list = calloc(num_results, sizeof(int));
+	if(!rtt_list) {
+		log_err("malloc failure: allocating rtt_list");
+		return -1;
+	}
+	rtt_index = rtt_list;
+
+	for(i=0; i<num_results && result_list; i++) {
+		if(result_list->sel_rtt != -1) {
+			*rtt_index = result_list->sel_rtt;
+			rtt_index++;
+		}
+		result_list=result_list->next_result;
+	}
+	qsort(rtt_list, num_results, sizeof(*rtt_list), rtt_compare);
+
+	log_assert(n > 0);
+	rtt_band = rtt_list[n-1];
+	free(rtt_list);
+
+	return rtt_band;
+}
+
 /** filter the address list, putting best targets at front,
  * returns number of best targets (or 0, no suitable targets) */
 static int
@@ -314,12 +363,13 @@ iter_filter_order(struct iter_env* iter_env, struct module_env* env,
 	struct delegpt* dp, int* selected_rtt, int open_target, 
 	struct sock_list* blacklist, time_t prefetch)
 {
-	int got_num = 0, low_rtt = 0, swap_to_front, rtt_band = RTT_BAND;
+	int got_num = 0, low_rtt = 0, swap_to_front, rtt_band = RTT_BAND,
+		num_results, nth;
 	struct delegpt_addr* a, *n, *prev=NULL;
 
 	/* fillup sel_rtt and find best rtt in the bunch */
 	got_num = iter_fill_rtt(iter_env, env, name, namelen, qtype, now, dp, 
-		&low_rtt, blacklist);
+		&low_rtt, blacklist, &num_results);
 	if(got_num == 0) 
 		return 0;
 	if(low_rtt >= USEFUL_SERVER_TOP_TIMEOUT &&
@@ -329,14 +379,19 @@ 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_permil != 0 && prefetch == 0 &&
-		low_rtt < env->cfg->low_rtt &&
-		ub_random_max(env->rnd, 1000) < env->cfg->low_rtt_permil) {
+	if(env->cfg->fast_server_permil != 0 && prefetch == 0 &&
+		num_results > env->cfg->fast_server_num &&
+		ub_random_max(env->rnd, 1000) < env->cfg->fast_server_permil) {
 		/* 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;
+		 * there are more servers available then the fastest N we want
+		 * to choose from. Limit our choice to the fastest servers. */
+		nth = nth_rtt(dp->result_list, num_results,
+			env->cfg->fast_server_num);
+		if(nth > 0) {
+			rtt_band = nth - low_rtt;
+			if(rtt_band > RTT_BAND)
+				rtt_band = RTT_BAND;
+		}
 	}
 
 	got_num = 0;

util/config_file.c

@@ -167,8 +167,8 @@ 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_permil = 0;
-	cfg->low_rtt = 45;
+	cfg->fast_server_permil = 0;
+	cfg->fast_server_num = 4;
 	cfg->donotqueryaddrs = NULL;
 	cfg->donotquery_localhost = 1;
 	cfg->root_hints = NULL;
@@ -642,9 +642,8 @@ int config_set_option(struct config_file* cfg, const char* opt,
 	else S_POW2("ratelimit-slabs:", ratelimit_slabs)
 	else S_NUMBER_OR_ZERO("ip-ratelimit-factor:", ip_ratelimit_factor)
 	else S_NUMBER_OR_ZERO("ratelimit-factor:", ratelimit_factor)
-	else S_NUMBER_OR_ZERO("low-rtt:", low_rtt)
-	else S_NUMBER_OR_ZERO("low-rtt-pct:", low_rtt_permil)
-	else S_NUMBER_OR_ZERO("low-rtt-permil:", low_rtt_permil)
+	else S_NUMBER_NONZERO("fast-server-num:", fast_server_num)
+	else S_NUMBER_OR_ZERO("fast-server-permil:", fast_server_permil)
 	else S_YNO("qname-minimisation:", qname_minimisation)
 	else S_YNO("qname-minimisation-strict:", qname_minimisation_strict)
 #ifdef USE_IPSECMOD
@@ -1036,9 +1035,8 @@ config_get_option(struct config_file* cfg, const char* opt,
 	else O_LS2(opt, "ratelimit-below-domain", ratelimit_below_domain)
 	else O_DEC(opt, "ip-ratelimit-factor", ip_ratelimit_factor)
 	else O_DEC(opt, "ratelimit-factor", ratelimit_factor)
-	else O_DEC(opt, "low-rtt", low_rtt)
-	else O_DEC(opt, "low-rtt-pct", low_rtt_permil)
-	else O_DEC(opt, "low-rtt-permil", low_rtt_permil)
+	else O_DEC(opt, "fast-server-num", fast_server_num)
+	else O_DEC(opt, "fast-server-permil", fast_server_permil)
 	else O_DEC(opt, "val-sig-skew-min", val_sig_skew_min)
 	else O_DEC(opt, "val-sig-skew-max", val_sig_skew_max)
 	else O_YNO(opt, "qname-minimisation", qname_minimisation)

util/config_file.h

@@ -159,10 +159,11 @@ 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_permil;
-	/** what time in msec is a low rtt destination */
-	int low_rtt;
+	/** percent*10, how many times in 1000 to pick from the fastest
+	 * destinations */
+	int fast_server_permil;
+	/** number of fastest server to select from */
+	int fast_server_num;
 
 	/** automatic interface for incoming messages. Uses ipv6 remapping,
 	 * and recvmsg/sendmsg ancillary data to detect interfaces, boolean */

util/configlexer.lex

@@ -441,8 +441,10 @@ 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_PERMIL) }
-low-rtt-permil{COLON}		{ YDVAR(1, VAR_LOW_RTT_PERMIL) }
+fast-server-num{COLON}		{ YDVAR(1, VAR_FAST_SERVER_NUM) }
+low-rtt-pct{COLON}		{ YDVAR(1, VAR_FAST_SERVER_PERMIL) }
+low-rtt-permil{COLON}		{ YDVAR(1, VAR_FAST_SERVER_PERMIL) }
+fast-server-permil{COLON}	{ YDVAR(1, VAR_FAST_SERVER_PERMIL) }
 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

@@ -290,12 +290,14 @@ extern int yydebug;
     VAR_TLS_ADDITIONAL_PORT = 500,
     VAR_LOW_RTT = 501,
     VAR_LOW_RTT_PERMIL = 502,
-    VAR_ALLOW_NOTIFY = 503,
-    VAR_TLS_WIN_CERT = 504,
-    VAR_TCP_CONNECTION_LIMIT = 505,
-    VAR_FORWARD_NO_CACHE = 506,
-    VAR_STUB_NO_CACHE = 507,
-    VAR_LOG_SERVFAIL = 508
+    VAR_FAST_SERVER_PERMIL = 503,
+    VAR_FAST_SERVER_NUM = 504,
+    VAR_ALLOW_NOTIFY = 505,
+    VAR_TLS_WIN_CERT = 506,
+    VAR_TCP_CONNECTION_LIMIT = 507,
+    VAR_FORWARD_NO_CACHE = 508,
+    VAR_STUB_NO_CACHE = 509,
+    VAR_LOG_SERVFAIL = 510
   };
 #endif
 /* Tokens.  */
@@ -544,12 +546,14 @@ extern int yydebug;
 #define VAR_TLS_ADDITIONAL_PORT 500
 #define VAR_LOW_RTT 501
 #define VAR_LOW_RTT_PERMIL 502
-#define VAR_ALLOW_NOTIFY 503
-#define VAR_TLS_WIN_CERT 504
-#define VAR_TCP_CONNECTION_LIMIT 505
-#define VAR_FORWARD_NO_CACHE 506
-#define VAR_STUB_NO_CACHE 507
-#define VAR_LOG_SERVFAIL 508
+#define VAR_FAST_SERVER_PERMIL 503
+#define VAR_FAST_SERVER_NUM 504
+#define VAR_ALLOW_NOTIFY 505
+#define VAR_TLS_WIN_CERT 506
+#define VAR_TCP_CONNECTION_LIMIT 507
+#define VAR_FORWARD_NO_CACHE 508
+#define VAR_STUB_NO_CACHE 509
+#define VAR_LOG_SERVFAIL 510
 
 /* Value type.  */
 #if ! defined YYSTYPE && ! defined YYSTYPE_IS_DECLARED
@@ -560,7 +564,7 @@ union YYSTYPE
 
 	char*	str;
 
-#line 564 "util/configparser.h" /* yacc.c:1909  */
+#line 568 "util/configparser.h" /* yacc.c:1909  */
 };
 
 typedef union YYSTYPE YYSTYPE;

util/configparser.y

@@ -159,6 +159,7 @@ extern struct config_parser_state* cfg_parser;
 %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_TLS_ADDITIONAL_PORT VAR_LOW_RTT VAR_LOW_RTT_PERMIL
+%token VAR_FAST_SERVER_PERMIL VAR_FAST_SERVER_NUM
 %token VAR_ALLOW_NOTIFY VAR_TLS_WIN_CERT VAR_TCP_CONNECTION_LIMIT
 %token VAR_FORWARD_NO_CACHE VAR_STUB_NO_CACHE VAR_LOG_SERVFAIL
 
@@ -255,7 +256,7 @@ content_server: server_num_threads | server_verbosity | server_port |
 	server_ipsecmod_whitelist | server_ipsecmod_strict |
 	server_udp_upstream_without_downstream | server_aggressive_nsec |
 	server_tls_cert_bundle | server_tls_additional_port | server_low_rtt |
-	server_low_rtt_permil | server_tls_win_cert |
+	server_fast_server_permil | server_fast_server_num  | server_tls_win_cert |
 	server_tcp_connection_limit | server_log_servfail
 	;
 stubstart: VAR_STUB_ZONE
@@ -1974,19 +1975,25 @@ server_ratelimit_factor: VAR_RATELIMIT_FACTOR STRING_ARG
 	;
 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);
+		OUTYY(("P(low-rtt option is deprecated, use fast-server-num instead)\n"));
 		free($2);
 	}
 	;
-server_low_rtt_permil: VAR_LOW_RTT_PERMIL STRING_ARG 
+server_fast_server_num: VAR_FAST_SERVER_NUM STRING_ARG 
 	{ 
-		OUTYY(("P(server_low_rtt_permil:%s)\n", $2)); 
+		OUTYY(("P(server_fast_server_num:%s)\n", $2)); 
+		if(atoi($2) <= 0)
+			yyerror("number expected");
+		else cfg_parser->cfg->fast_server_num = atoi($2);
+		free($2);
+	}
+	;
+server_fast_server_permil: VAR_FAST_SERVER_PERMIL STRING_ARG 
+	{ 
+		OUTYY(("P(server_fast_server_permil:%s)\n", $2)); 
 		if(atoi($2) == 0 && strcmp($2, "0") != 0)
 			yyerror("number expected");
-		else cfg_parser->cfg->low_rtt_permil = atoi($2);
+		else cfg_parser->cfg->fast_server_permil = atoi($2);
 		free($2);
 	}
 	;