Add my getaddrinfo(3) stress-tester as gaithrstress. The most obvious

regressions would be to see the program or your kernel crashing.

If you want to give it something to really test out, try a much more
reentrant version of the resolver.
<URL:http://green.homeunix.org/~green/reentrant_resolver.patch>
Any Mozilla-based browser would show you a clear difference.

tools/regression/README

@@ -27,3 +27,4 @@ fsx		General filesystem exerciser
 sysvmsg 	SysV IPC Message Queue Regression Utility
 sysvsem 	SysV IPC Semaphore Regression Utility
 sysvshm 	SysV IPC Shared Memory Regression Utility
+gaithrstress	General threaded getaddrinfo(3) exerciser

tools/regression/gaithrstress/Makefile

@@ -0,0 +1,7 @@
+# $FreeBSD$
+
+PROG=	gaithrstress
+LDADD+=	-pthread
+
+NOMAN=	yes
+.include <bsd.prog.mk>

tools/regression/gaithrstress/gaithrstress.c

@@ -0,0 +1,245 @@
+/*-
+ * Copyright (c) 2004 Brian Fundakowski Feldman
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. 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.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE AUTHOR 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 AUTHOR 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.
+ *
+ * $FreeBSD$
+ * $Id: getaddrinfo-pthreads-stresstest.c,v 1.4 2004/02/20 03:54:17 green Exp green $
+ */
+
+#include <sys/types.h>
+#include <sys/socket.h>
+
+#include <netinet/in.h>
+
+#include <err.h>
+#include <netdb.h>
+#include <pthread.h>
+#include <resolv.h>
+#include <stdio.h>
+#include <stdint.h>
+#include <stdlib.h>
+#include <string.h>
+#include <unistd.h>
+
+/* Per-thread struct containing all important data. */
+struct worker {
+	pthread_t w_thread;			     /* self */
+	uintmax_t w_lookup_success, w_lookup_failure;   /* getaddrinfo stats */
+};
+
+static volatile int workers_stop = 0;
+static double max_random_sleep = 1.0;
+static char **randwords;
+static size_t nrandwords;
+
+/*
+ * We don't have good random(3)-type functions that are thread-safe,
+ * unfortunately.
+ */
+static u_int32_t
+my_arc4random_r(void)
+{
+	static pthread_mutex_t mymutex = PTHREAD_MUTEX_INITIALIZER;
+	u_int32_t ret;
+
+	(void)pthread_mutex_lock(&mymutex);
+	ret = arc4random();
+	(void)pthread_mutex_unlock(&mymutex);
+	return (ret);
+}
+
+static void
+randomsleep(double max_sleep_sec)
+{
+	struct timespec slptime = { 0, 0 };
+	double rndsleep;
+
+	rndsleep = (double)my_arc4random_r() / 4294967296.0 * max_sleep_sec;
+	while (rndsleep >= 1.0) {
+		slptime.tv_sec++;
+		rndsleep -= 1.0;
+	}
+	slptime.tv_nsec = rndsleep * 1e9;
+	(void)nanosleep(&slptime, NULL);
+}
+
+/*
+ * Start looking up arbitrary hostnames and record the successes/failures.
+ * Between lookups, sleep a random amount of time to make sure threads
+ * stay well out of synchronization.
+ */
+static void *
+work(void *arg)
+{
+	struct worker *w = arg;
+
+	/* Turn off domain name list searching. */
+	if (_res.options & RES_INIT || res_init() == 0)
+		_res.options &= ~RES_DNSRCH;
+	do {
+		const char *suffixes[] = { "net", "com", "org" };
+		const size_t nsuffixes = sizeof(suffixes) / sizeof(suffixes[0]);
+		struct addrinfo *res;
+		char *hostname;
+		int error;
+
+		randomsleep(max_random_sleep);
+		if (asprintf(&hostname, "%s%s%s.%s",
+		    (my_arc4random_r() % 2) == 0 ? "www." : "",
+		    randwords[my_arc4random_r() % nrandwords],
+		    (my_arc4random_r() % 3) == 0 ?
+		    randwords[my_arc4random_r() % nrandwords] : "",
+		    suffixes[my_arc4random_r() % nsuffixes]) == -1)
+			continue;
+		error = getaddrinfo(hostname, NULL, NULL, &res);
+		free(hostname);
+		if (error == 0) {
+			w->w_lookup_success++;
+			freeaddrinfo(res);
+		} else {
+			w->w_lookup_failure++;
+		}
+	} while (!workers_stop);
+
+	pthread_exit(NULL);
+}
+
+int
+dowordfile(const char *fname)
+{
+	FILE *fp;
+	char newword[64];
+	size_t n;
+
+	fp = fopen(fname, "r");
+	if (fp == NULL)
+		return (-1);
+	nrandwords = 0;
+	while (fgets(newword, sizeof(newword), fp) != NULL)
+		nrandwords++;
+	if (ferror(fp) || fseek(fp, 0, SEEK_SET) != 0)
+		goto fail;
+	randwords = calloc(nrandwords, sizeof(char *));
+	if (randwords == NULL)
+		goto fail;
+	n = nrandwords;
+	nrandwords = 0;
+	while (fgets(newword, sizeof(newword), fp) != NULL) {
+		newword[strcspn(newword, "\r\n")] = '\0';
+		randwords[nrandwords] = strdup(newword);
+		if (randwords[nrandwords] == NULL)
+			err(1, "reading words file");
+		if (++nrandwords == n)
+			break;
+	}
+	nrandwords = n;
+	fclose(fp);
+	return (0);
+fail:
+	fclose(fp);
+	return (-1);
+}
+
+int
+main(int argc, char **argv) {
+	unsigned long nworkers = 1;
+	struct worker *workers;
+	size_t i;
+	char waiting[3], *send, *wordfile = "/usr/share/dict/words";
+	int ch;
+
+	if (getprogname() == NULL)
+		setprogname(argv[0]);
+	printf("%s: threaded stress-tester for getaddrinfo(3)\n",
+	    getprogname());
+	printf("(c) 2004 Brian Feldman <green@FreeBSD.org>\n");
+	while ((ch = getopt(argc, argv, "s:t:w:")) != -1) {
+		switch (ch) {
+		case 's':
+			max_random_sleep = strtod(optarg, &send);
+			if (*send != '\0')
+				goto usage;
+			break;
+		case 't':
+			nworkers = strtoul(optarg, &send, 0);
+			if (*send != '\0')
+				goto usage;
+			break;
+		case 'w':
+			wordfile = optarg;
+			break;
+		default:
+usage:
+			fprintf(stderr, "usage: %s [-s sleep] [-t threads] "
+			    "[-w wordfile]\n", getprogname());
+			exit(2);
+		}
+	}
+	argc -= optind;
+	argv += optind;
+
+	if (nworkers < 1 || nworkers != (size_t)nworkers)
+		goto usage;
+	if (dowordfile(wordfile) == -1)
+		err(1, "reading word file %s", wordfile);
+	if (nrandwords < 1)
+		errx(1, "word file %s did not have >0 words", wordfile);
+	printf("Read %u random words from %s.\n", nrandwords, wordfile);
+	workers = calloc(nworkers, sizeof(*workers));
+	if (workers == NULL)
+		err(1, "allocating workers");
+	printf("Intra-query delay time is from 0 to %g seconds (random).\n",
+	    max_random_sleep);
+
+	printf("Starting %lu worker%.*s: ", nworkers, nworkers > 1, "s");
+	fflush(stdout);
+	for (i = 0; i < nworkers; i++) {
+		if (pthread_create(&workers[i].w_thread, NULL, work,
+		    &workers[i]) == -1)
+			err(1, "creating worker %u", i);
+		printf("%u%s", i, i == nworkers - 1 ? ".\n" : ", ");
+		fflush(stdout);
+	}
+
+	printf("<Press enter key to end test.>\n");
+	(void)fgets(waiting, sizeof(waiting), stdin);
+	workers_stop = 1;
+
+	printf("Stopping %lu worker%.*s: ", nworkers, nworkers > 1, "s");
+	fflush(stdout);
+	for (i = 0; i < nworkers; i++) {
+		pthread_join(workers[i].w_thread, NULL);
+		printf("%u%s", i, i == nworkers - 1 ? ".\n" : ", ");
+		fflush(stdout);
+	}
+
+	printf("%-10s%-20s%-20s\n", "Worker", "Successful GAI", "Failed GAI");
+	printf("%-10s%-20s%-20s\n", "------", "--------------", "----------");
+	for (i = 0; i < nworkers; i++) {
+		printf("%-10u%-20ju%-20ju\n", i, workers[i].w_lookup_success,
+		    workers[i].w_lookup_failure);
+	}
+
+	exit(0);
+}