timeout estimation code.

git-svn-id: file:///svn/unbound/trunk@317 be551aaa-1e26-0410-a405-d3ace91eadb9

doc/Changelog

@@ -1,6 +1,7 @@
 14 May 2007: Wouter
 	- Port to OS/X and Dec Alpha. Printf format and alignment fixes.
 	- extensive lock debug report on join timeout.
+	- proper RTT calculation, in utility code.
 
 11 May 2007: Wouter
 	- iterator/iterator.c module.

testcode/checklocks.c

@@ -756,7 +756,8 @@ thread_debug_info(struct thr_check* thr)
 		(thr->arg?*(int*)thr->arg:0));
 	log_info("thread num is %d", thr->num);
 	log_info("locks created %d", thr->locks_created);
-	log_info("FILE for lockinfo: %x. flushing.", (int)thr->order_info);
+	log_info("open file for lockinfo: %s", 
+		thr->order_info?"yes, flushing":"no");
 	fflush(thr->order_info);
 	w = thr->waiting;
 	f = thr->holding_first;

testcode/unitmain.c

@@ -119,6 +119,30 @@ net_test()
 	unit_assert( !is_pow2(259) );
 }
 
+#include "util/rtt.h"
+/** test RTT code */
+static void
+rtt_test()
+{
+	int i;
+	struct rtt_info r;
+	rtt_init(&r);
+	/* initial value sensible */
+	unit_assert( rtt_timeout(&r) == 3000 );
+	rtt_lost(&r);
+	unit_assert( rtt_timeout(&r) == 6000 );
+	rtt_lost(&r);
+	unit_assert( rtt_timeout(&r) == 12000 );
+	rtt_update(&r, 4000);
+	unit_assert( rtt_timeout(&r) >= 5000 );
+	rtt_lost(&r);
+	for(i=0; i<100; i++) {
+		rtt_lost(&r); 
+		unit_assert( rtt_timeout(&r) > RTT_MIN_TIMEOUT-1);
+		unit_assert( rtt_timeout(&r) < RTT_MAX_TIMEOUT+1);
+	}
+}
+
 /**
  * Main unit test program. Setup, teardown and report errors.
  * @param argc: arg count.
@@ -137,6 +161,7 @@ main(int argc, char* argv[])
 	checklock_start();
 	net_test();
 	dname_test();
+	rtt_test();
 	alloc_test();
 	lruhash_test();
 	slabhash_test();

util/rtt.c

@@ -0,0 +1,92 @@
+/*
+ * util/rtt.c - UDP round trip time estimator for resend timeouts.
+ *
+ * Copyright (c) 2007, NLnet Labs. All rights reserved.
+ *
+ * This software is open source.
+ * 
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ * 
+ * Redistributions of source code must retain the above copyright notice,
+ * this list of conditions and the following disclaimer.
+ * 
+ * Redistributions in binary form must reproduce the above copyright notice,
+ * this list of conditions and the following disclaimer in the documentation
+ * and/or other materials provided with the distribution.
+ * 
+ * Neither the name of the NLNET LABS nor the names of its contributors may
+ * be used to endorse or promote products derived from this software without
+ * specific prior written permission.
+ * 
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
+ * TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
+ * PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE
+ * LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
+ * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
+ * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
+ * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
+ * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
+ * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
+ * POSSIBILITY OF SUCH DAMAGE.
+ */
+
+/**
+ * \file
+ *
+ * This file contains a data type and functions to help estimate good
+ * round trip times for UDP resend timeout values.
+ */
+#include "config.h"
+#include "util/rtt.h"
+#include "util/log.h"
+
+/** calculate RTO from rtt information */
+static int
+calc_rto(const struct rtt_info* rtt)
+{
+	/* From Stevens, Unix Network Programming, p.598 */
+	int rto = rtt->srtt + 4*rtt->rttvar;
+	if(rto < RTT_MIN_TIMEOUT)
+		rto = RTT_MIN_TIMEOUT;
+	if(rto > RTT_MAX_TIMEOUT)
+		rto = RTT_MAX_TIMEOUT;
+	return rto;
+}
+
+void 
+rtt_init(struct rtt_info* rtt)
+{
+	rtt->srtt = 0;
+	rtt->rttvar = 750;
+	rtt->rto = calc_rto(rtt);
+	/* first RTO is 0 + 4*0.75 = 3 seconds */
+}
+
+int 
+rtt_timeout(const struct rtt_info* rtt)
+{
+	return rtt->rto;
+}
+
+void 
+rtt_update(struct rtt_info* rtt, int ms)
+{
+	int delta = ms - rtt->srtt;
+	rtt->srtt += delta / 8; /* g = 1/8 */
+	if(delta < 0)
+		delta = -delta; /* |delta| */
+	rtt->rttvar += (delta - rtt->rttvar) / 4; /* h = 1/4 */
+	rtt->rto = calc_rto(rtt);
+}
+
+void 
+rtt_lost(struct rtt_info* rtt)
+{
+	/* exponential backoff */
+	rtt->rto *= 2;
+	if(rtt->rto > RTT_MAX_TIMEOUT)
+		rtt->rto = RTT_MAX_TIMEOUT;
+}

util/rtt.h

@@ -0,0 +1,89 @@
+/*
+ * util/rtt.h - UDP round trip time estimator for resend timeouts.
+ *
+ * Copyright (c) 2007, NLnet Labs. All rights reserved.
+ *
+ * This software is open source.
+ * 
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ * 
+ * Redistributions of source code must retain the above copyright notice,
+ * this list of conditions and the following disclaimer.
+ * 
+ * Redistributions in binary form must reproduce the above copyright notice,
+ * this list of conditions and the following disclaimer in the documentation
+ * and/or other materials provided with the distribution.
+ * 
+ * Neither the name of the NLNET LABS nor the names of its contributors may
+ * be used to endorse or promote products derived from this software without
+ * specific prior written permission.
+ * 
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
+ * TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
+ * PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE
+ * LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
+ * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
+ * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
+ * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
+ * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
+ * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
+ * POSSIBILITY OF SUCH DAMAGE.
+ */
+
+/**
+ * \file
+ *
+ * This file contains a data type and functions to help estimate good
+ * round trip times for UDP resend timeout values.
+ */
+
+#ifndef UTIL_RTT_H
+#define UTIL_RTT_H
+
+/**
+ * RTT information. Keeps packet Round Trip Time.
+ */
+struct rtt_info {
+	/** smoothed rtt estimator, in milliseconds */
+	int srtt;
+	/** smoothed mean deviation, in milliseconds */
+	int rttvar;
+	/** current RTO in use, in milliseconds */
+	int rto;
+};
+
+/** min retransmit timeout value, in milliseconds */
+#define RTT_MIN_TIMEOUT	2000
+/** max retransmit timeout value, in milliseconds */
+#define RTT_MAX_TIMEOUT 120000
+
+/**
+ * Initialize RTT estimators.
+ * @param rtt: The structure. Caller is responsible for allocation of it.
+ */
+void rtt_init(struct rtt_info* rtt);
+
+/** 
+ * Get timeout to use for sending a UDP packet.
+ * @param rtt: round trip statistics structure.
+ * @return: timeout to use in milliseconds. Relative time value.
+ */
+int rtt_timeout(const struct rtt_info* rtt);
+
+/**
+ * Update the statistics with a new roundtrip estimate observation.
+ * @param rtt: round trip statistics structure.
+ * @param ms: estimate of roundtrip time in milliseconds.
+ */
+void rtt_update(struct rtt_info* rtt, int ms);
+
+/**
+ * Update the statistics with a new timout expired observation.
+ * @param rtt: round trip statistics structure.
+ */
+void rtt_lost(struct rtt_info* rtt);
+
+#endif /* UTIL_RTT_H */