diff --git a/resolv/Makefile b/resolv/Makefile
index 6942e85..ec7e4fd 100644
--- a/resolv/Makefile
+++ b/resolv/Makefile
@@ -65,7 +65,9 @@ tests-internal += \
   tst-resolv-res_init-thread \
 
 # Needs resolv_context.
-tests-internal += tst-resolv-res_ninit
+tests-internal += \
+  tst-resolv-res_ninit \
+  tst-resolv-threads \
 
 endif
 
@@ -168,6 +170,8 @@ $(objpfx)tst-resolv-res_init-thread: $(libdl) $(objpfx)libresolv.so \
 $(objpfx)tst-resolv-qtypes: $(objpfx)libresolv.so $(shared-thread-library)
 $(objpfx)tst-resolv-rotate: $(objpfx)libresolv.so $(shared-thread-library)
 $(objpfx)tst-resolv-search: $(objpfx)libresolv.so $(shared-thread-library)
+$(objpfx)tst-resolv-threads: \
+  $(libdl) $(objpfx)libresolv.so $(shared-thread-library)
 $(objpfx)tst-resolv-canonname: \
   $(libdl) $(objpfx)libresolv.so $(shared-thread-library)
 
diff --git a/resolv/tst-resolv-threads.c b/resolv/tst-resolv-threads.c
new file mode 100644
index 0000000..7be417b
--- /dev/null
+++ b/resolv/tst-resolv-threads.c
@@ -0,0 +1,484 @@
+/* Test basic nss_dns functionality with multiple threads.
+   Copyright (C) 2016-2017 Free Software Foundation, Inc.
+   This file is part of the GNU C Library.
+
+   The GNU C Library is free software; you can redistribute it and/or
+   modify it under the terms of the GNU Lesser General Public
+   License as published by the Free Software Foundation; either
+   version 2.1 of the License, or (at your option) any later version.
+
+   The GNU C Library is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+   Lesser General Public License for more details.
+
+   You should have received a copy of the GNU Lesser General Public
+   License along with the GNU C Library; if not, see
+   <http://www.gnu.org/licenses/>.  */
+
+/* Unlike tst-resolv-basic, this test does not overwrite the _res
+   structure and relies on namespaces to achieve the redirection to
+   the test servers with a custom /etc/resolv.conf file.  */
+
+#include <dlfcn.h>
+#include <errno.h>
+#include <gnu/lib-names.h>
+#include <netdb.h>
+#include <resolv/resolv-internal.h>
+#include <resolv/resolv_context.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <support/check.h>
+#include <support/namespace.h>
+#include <support/resolv_test.h>
+#include <support/support.h>
+#include <support/temp_file.h>
+#include <support/test-driver.h>
+#include <support/xthread.h>
+#include <support/xunistd.h>
+
+/* Each client thread sends this many queries.  */
+enum { queries_per_thread = 500 };
+
+/* Return a small positive number identifying this thread.  */
+static int
+get_thread_number (void)
+{
+  static int __thread local;
+  if (local != 0)
+    return local;
+  static int global = 1;
+  local = __atomic_fetch_add (&global, 1, __ATOMIC_RELAXED);
+  return local;
+}
+
+static void
+response (const struct resolv_response_context *ctx,
+          struct resolv_response_builder *b,
+          const char *qname, uint16_t qclass, uint16_t qtype)
+{
+  TEST_VERIFY_EXIT (qname != NULL);
+
+  int counter = 0;
+  int thread = 0;
+  int dummy = 0;
+  TEST_VERIFY (sscanf (qname, "counter%d.thread%d.example.com%n",
+                       &counter, &thread, &dummy) == 2);
+  TEST_VERIFY (dummy > 0);
+
+  struct resolv_response_flags flags = { 0 };
+  resolv_response_init (b, flags);
+  resolv_response_add_question (b, qname, qclass, qtype);
+
+  resolv_response_section (b, ns_s_an);
+  resolv_response_open_record (b, qname, qclass, qtype, 0);
+  switch (qtype)
+    {
+    case T_A:
+      {
+        char ipv4[4] = {10, 0, counter, thread};
+        resolv_response_add_data (b, &ipv4, sizeof (ipv4));
+      }
+      break;
+    case T_AAAA:
+      {
+        char ipv6[16]
+          = {0x20, 0x01, 0xd, 0xb8, 0, 0, 0, 0, 0, 0, 0,
+             counter, 0, thread, 0, 0};
+        resolv_response_add_data (b, &ipv6, sizeof (ipv6));
+      }
+      break;
+    default:
+      support_record_failure ();
+      printf ("error: unexpected QTYPE: %s/%u/%u\n",
+              qname, qclass, qtype);
+    }
+  resolv_response_close_record (b);
+}
+
+/* Check that the resolver configuration for this thread has an
+   extended resolver configuration.  */
+static void
+check_have_conf (void)
+{
+  struct resolv_context *ctx = __resolv_context_get ();
+  TEST_VERIFY_EXIT (ctx != NULL);
+  TEST_VERIFY (ctx->conf != NULL);
+  __resolv_context_put (ctx);
+}
+
+/* Verify that E matches the expected response for FAMILY and
+   COUNTER.  */
+static void
+check_hostent (const char *caller, const char *function, const char *qname,
+               int ret, struct hostent *e, int family, int counter)
+{
+  if (ret != 0)
+    {
+      errno = ret;
+      support_record_failure ();
+      printf ("error: %s: %s for %s failed: %m\n", caller, function, qname);
+      return;
+    }
+
+  TEST_VERIFY_EXIT (e != NULL);
+  TEST_VERIFY (strcmp (qname, e->h_name) == 0);
+  TEST_VERIFY (e->h_addrtype == family);
+  TEST_VERIFY_EXIT (e->h_addr_list[0] != NULL);
+  TEST_VERIFY (e->h_addr_list[1] == NULL);
+  switch (family)
+    {
+    case AF_INET:
+      {
+        char addr[4] = {10, 0, counter, get_thread_number ()};
+        TEST_VERIFY (e->h_length == sizeof (addr));
+        TEST_VERIFY (memcmp (e->h_addr_list[0], addr, sizeof (addr)) == 0);
+      }
+      break;
+    case AF_INET6:
+      {
+      char addr[16]
+        = {0x20, 0x01, 0xd, 0xb8, 0, 0, 0, 0, 0, 0,
+           0, counter, 0, get_thread_number (), 0, 0};
+      TEST_VERIFY (e->h_length == sizeof (addr));
+      TEST_VERIFY (memcmp (e->h_addr_list[0], addr, sizeof (addr)) == 0);
+      }
+      break;
+    default:
+      FAIL_EXIT1 ("%s: invalid address family %d", caller, family);
+    }
+  check_have_conf ();
+}
+
+/* Check a getaddrinfo result.  */
+static void
+check_addrinfo (const char *caller, const char *qname,
+                int ret, struct addrinfo *ai, int family, int counter)
+{
+  if (ret != 0)
+    {
+      support_record_failure ();
+      printf ("error: %s: getaddrinfo for %s failed: %s\n",
+              caller, qname, gai_strerror (ret));
+      return;
+    }
+
+  TEST_VERIFY_EXIT (ai != NULL);
+
+  /* Check that available data matches the requirements.  */
+  bool have_ipv4 = false;
+  bool have_ipv6 = false;
+  for (struct addrinfo *p = ai; p != NULL; p = p->ai_next)
+    {
+      TEST_VERIFY (p->ai_socktype == SOCK_STREAM);
+      TEST_VERIFY (p->ai_protocol == IPPROTO_TCP);
+      TEST_VERIFY_EXIT (p->ai_addr != NULL);
+      TEST_VERIFY (p->ai_addr->sa_family == p->ai_family);
+
+      switch (p->ai_family)
+        {
+        case AF_INET:
+          {
+            TEST_VERIFY (!have_ipv4);
+            have_ipv4 = true;
+            struct sockaddr_in *sa = (struct sockaddr_in *) p->ai_addr;
+            TEST_VERIFY (p->ai_addrlen == sizeof (*sa));
+            char addr[4] = {10, 0, counter, get_thread_number ()};
+            TEST_VERIFY (memcmp (&sa->sin_addr, addr, sizeof (addr)) == 0);
+            TEST_VERIFY (ntohs (sa->sin_port) == 80);
+          }
+          break;
+        case AF_INET6:
+          {
+            TEST_VERIFY (!have_ipv6);
+            have_ipv6 = true;
+            struct sockaddr_in6 *sa = (struct sockaddr_in6 *) p->ai_addr;
+            TEST_VERIFY (p->ai_addrlen == sizeof (*sa));
+            char addr[16]
+              = {0x20, 0x01, 0xd, 0xb8, 0, 0, 0, 0, 0, 0,
+                 0, counter, 0, get_thread_number (), 0, 0};
+            TEST_VERIFY (memcmp (&sa->sin6_addr, addr, sizeof (addr)) == 0);
+            TEST_VERIFY (ntohs (sa->sin6_port) == 80);
+          }
+          break;
+        default:
+          FAIL_EXIT1 ("%s: invalid address family %d", caller, family);
+        }
+    }
+
+  switch (family)
+    {
+      case AF_INET:
+        TEST_VERIFY (have_ipv4);
+        TEST_VERIFY (!have_ipv6);
+        break;
+      case AF_INET6:
+        TEST_VERIFY (!have_ipv4);
+        TEST_VERIFY (have_ipv6);
+        break;
+      case AF_UNSPEC:
+        TEST_VERIFY (have_ipv4);
+        TEST_VERIFY (have_ipv6);
+        break;
+    default:
+      FAIL_EXIT1 ("%s: invalid address family %d", caller, family);
+    }
+
+  check_have_conf ();
+}
+
+/* This barrier ensures that all test threads begin their work
+   simultaneously.  */
+static pthread_barrier_t barrier;
+
+/* Test gethostbyname2_r (if do_2 is false) or gethostbyname2_r with
+   AF_INET (if do_2 is true).  */
+static void *
+byname (bool do_2)
+{
+  int this_thread = get_thread_number ();
+  xpthread_barrier_wait (&barrier);
+  for (int i = 0; i < queries_per_thread; ++i)
+    {
+      char qname[100];
+      snprintf (qname, sizeof (qname), "counter%d.thread%d.example.com",
+                i, this_thread);
+      struct hostent storage;
+      char buf[1000];
+      struct hostent *e = NULL;
+      int herrno;
+      int ret;
+      if (do_2)
+        ret = gethostbyname_r (qname, &storage, buf, sizeof (buf),
+                               &e, &herrno);
+      else
+        ret = gethostbyname2_r (qname, AF_INET, &storage, buf, sizeof (buf),
+                                &e, &herrno);
+      check_hostent (__func__, do_2 ? "gethostbyname2_r" : "gethostbyname_r",
+                     qname, ret, e, AF_INET, i);
+    }
+  check_have_conf ();
+  return NULL;
+}
+
+/* Test gethostbyname_r.  */
+static void *
+thread_byname (void *closure)
+{
+  return byname (false);
+}
+
+/* Test gethostbyname2_r with AF_INET.  */
+static void *
+thread_byname2 (void *closure)
+{
+  return byname (true);
+}
+
+/* Call gethostbyname_r with RES_USE_INET6 (if do_2 is false), or
+   gethostbyname_r with AF_INET6 (if do_2 is true).  */
+static void *
+byname_inet6 (bool do_2)
+{
+  int this_thread = get_thread_number ();
+  xpthread_barrier_wait (&barrier);
+  if (!do_2)
+    {
+      res_init ();
+      _res.options |= DEPRECATED_RES_USE_INET6;
+      TEST_VERIFY (strcmp (_res.defdname, "example.com") == 0);
+    }
+  for (int i = 0; i < queries_per_thread; ++i)
+    {
+      char qname[100];
+      snprintf (qname, sizeof (qname), "counter%d.thread%d.example.com",
+                i, this_thread);
+      struct hostent storage;
+      char buf[1000];
+      struct hostent *e = NULL;
+      int herrno;
+      int ret;
+      if (do_2)
+        ret = gethostbyname2_r (qname, AF_INET6, &storage, buf, sizeof (buf),
+                                &e, &herrno);
+      else
+        ret = gethostbyname_r (qname, &storage, buf, sizeof (buf),
+                               &e, &herrno);
+      check_hostent (__func__,
+                     do_2 ? "gethostbyname2_r" : "gethostbyname_r",
+                     qname, ret, e, AF_INET6, i);
+    }
+  return NULL;
+}
+
+/* Test gethostbyname_r with AF_INET6.  */
+static void *
+thread_byname_inet6 (void *closure)
+{
+  return byname_inet6 (false);
+}
+
+/* Test gethostbyname2_r with AF_INET6.  */
+static void *
+thread_byname2_af_inet6 (void *closure)
+{
+  return byname_inet6 (true);
+}
+
+/* Run getaddrinfo tests for FAMILY.  */
+static void *
+gai (int family, bool do_inet6)
+{
+  int this_thread = get_thread_number ();
+  xpthread_barrier_wait (&barrier);
+  if (do_inet6)
+    {
+      res_init ();
+      _res.options |= DEPRECATED_RES_USE_INET6;
+      check_have_conf ();
+    }
+  for (int i = 0; i < queries_per_thread; ++i)
+    {
+      char qname[100];
+      snprintf (qname, sizeof (qname), "counter%d.thread%d.example.com",
+                i, this_thread);
+      struct addrinfo hints =
+        {
+          .ai_family = family,
+          .ai_socktype = SOCK_STREAM,
+          .ai_protocol = IPPROTO_TCP,
+        };
+      struct addrinfo *ai;
+      int ret = getaddrinfo (qname, "80", &hints, &ai);
+      check_addrinfo (__func__, qname, ret, ai, family, i);
+      if (ret == 0)
+        freeaddrinfo (ai);
+    }
+  return NULL;
+}
+
+/* Test getaddrinfo with AF_INET.  */
+static void *
+thread_gai_inet (void *closure)
+{
+  return gai (AF_INET, false);
+}
+
+/* Test getaddrinfo with AF_INET6.  */
+static void *
+thread_gai_inet6 (void *closure)
+{
+  return gai (AF_INET6, false);
+}
+
+/* Test getaddrinfo with AF_UNSPEC.  */
+static void *
+thread_gai_unspec (void *closure)
+{
+  return gai (AF_UNSPEC, false);
+}
+
+/* Test getaddrinfo with AF_INET.  */
+static void *
+thread_gai_inet_inet6 (void *closure)
+{
+  return gai (AF_INET, true);
+}
+
+/* Test getaddrinfo with AF_INET6.  */
+static void *
+thread_gai_inet6_inet6 (void *closure)
+{
+  return gai (AF_INET6, true);
+}
+
+/* Test getaddrinfo with AF_UNSPEC.  */
+static void *
+thread_gai_unspec_inet6 (void *closure)
+{
+  return gai (AF_UNSPEC, true);
+}
+
+/* Description of the chroot environment used to run the tests.  */
+static struct support_chroot *chroot_env;
+
+/* Set up the chroot environment.  */
+static void
+prepare (int argc, char **argv)
+{
+  chroot_env = support_chroot_create
+    ((struct support_chroot_configuration)
+     {
+       .resolv_conf =
+         "search example.com\n"
+         "nameserver 127.0.0.1\n"
+         "nameserver 127.0.0.2\n"
+         "nameserver 127.0.0.3\n",
+     });
+}
+
+static int
+do_test (void)
+{
+  support_become_root ();
+  if (!support_enter_network_namespace ())
+    return EXIT_UNSUPPORTED;
+  if (!support_can_chroot ())
+    return EXIT_UNSUPPORTED;
+
+  /* Load the shared object outside of the chroot.  */
+  TEST_VERIFY (dlopen (LIBNSS_DNS_SO, RTLD_LAZY) != NULL);
+
+  xchroot (chroot_env->path_chroot);
+  TEST_VERIFY_EXIT (chdir ("/") == 0);
+
+  struct sockaddr_in server_address =
+    {
+      .sin_family = AF_INET,
+      .sin_addr = { .s_addr = htonl (INADDR_LOOPBACK) },
+      .sin_port = htons (53)
+    };
+  const struct sockaddr *server_addresses[1] =
+    { (const struct sockaddr *) &server_address };
+
+  struct resolv_test *aux = resolv_test_start
+    ((struct resolv_redirect_config)
+     {
+       .response_callback = response,
+       .nscount = 1,
+       .disable_redirect = true,
+       .server_address_overrides = server_addresses,
+     });
+
+  enum { thread_count = 10 };
+  xpthread_barrier_init (&barrier, NULL, thread_count + 1);
+  pthread_t threads[thread_count];
+  typedef void *(*thread_func) (void *);
+  thread_func thread_funcs[thread_count] =
+    {
+      thread_byname,
+      thread_byname2,
+      thread_byname_inet6,
+      thread_byname2_af_inet6,
+      thread_gai_inet,
+      thread_gai_inet6,
+      thread_gai_unspec,
+      thread_gai_inet_inet6,
+      thread_gai_inet6_inet6,
+      thread_gai_unspec_inet6,
+    };
+  for (int i = 0; i < thread_count; ++i)
+    threads[i] = xpthread_create (NULL, thread_funcs[i], NULL);
+  xpthread_barrier_wait (&barrier); /* Start the test threads.  */
+  for (int i = 0; i < thread_count; ++i)
+    xpthread_join (threads[i]);
+
+  resolv_test_end (aux);
+  support_chroot_free (chroot_env);
+
+  return 0;
+}
+
+#define PREPARE prepare
+#include <support/test-driver.c>
diff --git a/support/resolv_test.c b/support/resolv_test.c
index 050cd71..1625dcf 100644
--- a/support/resolv_test.c
+++ b/support/resolv_test.c
@@ -1004,6 +1004,29 @@ make_server_sockets (struct resolv_test_server *server)
     }
 }
 
+/* Like make_server_sockets, but the caller supplies the address to
+   use.  */
+static void
+make_server_sockets_for_address (struct resolv_test_server *server,
+                                 const struct sockaddr *addr)
+{
+  server->socket_udp = xsocket (AF_INET, SOCK_DGRAM, IPPROTO_UDP);
+  server->socket_tcp = xsocket (AF_INET, SOCK_STREAM, IPPROTO_TCP);
+
+  if (addr->sa_family == AF_INET)
+    server->address = *(const struct sockaddr_in *) addr;
+  else
+    /* We cannot store the server address in the socket.  This should
+       not matter if disable_redirect is used.  */
+    server->address = (struct sockaddr_in) { .sin_family = 0, };
+
+  xbind (server->socket_udp,
+         (struct sockaddr *)&server->address, sizeof (server->address));
+  xbind (server->socket_tcp,
+         (struct sockaddr *)&server->address, sizeof (server->address));
+  xlisten (server->socket_tcp, 5);
+}
+
 /* One-time initialization of NSS.  */
 static void
 resolv_redirect_once (void)
@@ -1064,11 +1087,17 @@ resolv_test_start (struct resolv_redirect_config config)
     .lock = PTHREAD_MUTEX_INITIALIZER,
   };
 
-  resolv_test_init ();
+  if (!config.disable_redirect)
+    resolv_test_init ();
 
   /* Create all the servers, to reserve the necessary ports.  */
   for (int server_index = 0; server_index < config.nscount; ++server_index)
-    make_server_sockets (obj->servers + server_index);
+    if (config.disable_redirect && config.server_address_overrides != NULL)
+      make_server_sockets_for_address
+        (obj->servers + server_index,
+         config.server_address_overrides[server_index]);
+    else
+      make_server_sockets (obj->servers + server_index);
 
   /* Start server threads.  Disable the server ports, as
      requested.  */
@@ -1095,6 +1124,9 @@ resolv_test_start (struct resolv_redirect_config config)
   if (config.single_thread_udp)
     start_server_thread_udp_single (obj);
 
+  if (config.disable_redirect)
+    return obj;
+
   int timeout = 1;
 
   /* Initialize libresolv.  */
@@ -1129,6 +1161,7 @@ resolv_test_start (struct resolv_redirect_config config)
     }
   for (int server_index = 0; server_index < config.nscount; ++server_index)
     {
+      TEST_VERIFY_EXIT (obj->servers[server_index].address.sin_port != 0);
       _res.nsaddr_list[server_index] = obj->servers[server_index].address;
       if (test_verbose)
         {
diff --git a/support/resolv_test.h b/support/resolv_test.h
index 6498751..b953dc1 100644
--- a/support/resolv_test.h
+++ b/support/resolv_test.h
@@ -93,6 +93,16 @@ struct resolv_redirect_config
      may results in more predictable ordering of queries and
      responses.  */
   bool single_thread_udp;
+
+  /* Do not rewrite the _res variable or change NSS defaults.  Use
+     server_address_overrides below to tell the testing framework on
+     which addresses to create the servers.  */
+  bool disable_redirect;
+
+  /* Use these addresses for creating the DNS servers.  The array must
+     have ns_count (or resolv_max_test_servers) sockaddr * elements if
+     not NULL.  */
+  const struct sockaddr *const *server_address_overrides;
 };
 
 /* Configure NSS to use, nss_dns only for aplicable databases, and try
