diff --git a/nss/nss_test.h b/nss/nss_test.h
index 49a9aff2fd..b6c6ad2333 100644
--- a/nss/nss_test.h
+++ b/nss/nss_test.h
@@ -33,10 +33,12 @@
 
 #include <pwd.h>
 #include <grp.h>
+#include <netdb.h>
 
 typedef struct test_tables {
   struct passwd *pwd_table;
   struct group *grp_table;
+  struct hostent *host_table;
 } test_tables;
 
 extern void _nss_test1_init_hook (test_tables *) __attribute__((weak));
@@ -44,9 +46,11 @@ extern void _nss_test2_init_hook (test_tables *) __attribute__((weak));
 
 #define PWD_LAST()    { .pw_name = NULL, .pw_uid = 0 }
 #define GRP_LAST()    { .gr_name = NULL, .gr_gid = 0 }
+#define HOST_LAST()    { .h_name = NULL, .h_aliases = NULL, .h_length = 0, .h_addr_list = NULL }
 
 #define PWD_ISLAST(p)    ((p)->pw_name == NULL && (p)->pw_uid == 0)
 #define GRP_ISLAST(g)    ((g)->gr_name == NULL && (g)->gr_gid == 0)
+#define HOST_ISLAST(h)    ((h)->h_name == NULL && (h)->h_length == 0)
 
 /* Macros to fill in the tables easily.  */
 
@@ -72,6 +76,11 @@ extern void _nss_test2_init_hook (test_tables *) __attribute__((weak));
     { .gr_name = (char *) n, .gr_passwd = (char *) "*", .gr_gid = u, \
       .gr_mem = (char **) m }
 
+#define HOST(u)								\
+    { .h_name = (char *) "name" #u, .h_aliases = NULL, .h_addrtype = u,	\
+      .h_length = 4,							\
+      .h_addr_list = (char **) hostaddr_##u  }
+
 /*------------------------------------------------------------*/
 
 /* Helper functions for testing passwd entries.  Call
diff --git a/nss/nss_test1.c b/nss/nss_test1.c
index 13532cd7ab..612c427c57 100644
--- a/nss/nss_test1.c
+++ b/nss/nss_test1.c
@@ -66,6 +66,9 @@ static int npwd_data = default_npwd_data;
 static struct group *grp_data = NULL;
 static int ngrp_data = 0;
 
+static struct hostent *host_data = NULL;
+static int nhost_data = 0;
+
 /* This function will get called, and once per session, look back into
    the test case's executable for an init hook function, and call
    it.  */
@@ -99,6 +102,13 @@ init(void)
 	    ;
 	  ngrp_data = i;
 	}
+      if (t.host_table)
+	{
+	  host_data = t.host_table;
+	  for (i=0; ! HOST_ISLAST(& host_data[i]); i++)
+	    ;
+	  nhost_data = i;
+	}
     }
   initted = 1;
 }
@@ -280,7 +290,7 @@ NAME(getgrent_r) (struct group *result, char *buffer, size_t buflen,
       ++grp_iter;
     }
 
-  pthread_mutex_unlock (&pwd_lock);
+  pthread_mutex_unlock (&grp_lock);
 
   return res;
 }
@@ -312,3 +322,157 @@ NAME(getgrnam_r) (const char *name, struct group *result, char *buffer,
 
   return NSS_STATUS_NOTFOUND;
 }
+
+/* -------------------------------------------------- */
+/* Host handling.  */
+
+static size_t host_iter;
+#define CURHOST host_data[host_iter]
+
+static pthread_mutex_t host_lock = PTHREAD_MUTEX_INITIALIZER;
+
+enum nss_status
+NAME(sethostent) (int stayopen)
+{
+  init();
+  host_iter = 0;
+  return NSS_STATUS_SUCCESS;
+}
+
+
+enum nss_status
+NAME(endhostent) (void)
+{
+  init();
+  return NSS_STATUS_SUCCESS;
+}
+
+static enum nss_status
+copy_host (struct hostent *result, struct hostent *local,
+	    char *buffer, size_t buflen, int *errnop)
+{
+  struct alloc_buffer buf = alloc_buffer_create (buffer, buflen);
+  char **memlist;
+  int i, j;
+
+  if (local->h_addr_list)
+    {
+      i = 0;
+      while (local->h_addr_list[i])
+	++i;
+
+      memlist = alloc_buffer_alloc_array (&buf, char *, i + 1);
+
+      if (memlist) {
+	for (j = 0; j < i; ++j)
+	  memlist[j] = alloc_buffer_maybe_copy_string (&buf, local->h_addr_list[j]);
+	memlist[j] = NULL;
+      }
+
+      result->h_addr_list = memlist;
+    }
+  else
+    {
+      result->h_addr_list = NULL;
+    }
+
+  result->h_aliases = NULL;
+  result->h_addrtype = AF_INET;
+  result->h_length = 4;
+  result->h_name = alloc_buffer_maybe_copy_string (&buf, local->h_name);
+
+  if (alloc_buffer_has_failed (&buf))
+    {
+      *errnop = ERANGE;
+      return NSS_STATUS_TRYAGAIN;
+    }
+
+  return NSS_STATUS_SUCCESS;
+}
+
+
+enum nss_status
+NAME(gethostent_r) (struct hostent *ret, char *buffer, size_t buflen,
+		    struct hostent **result, int *errnop)
+{
+  int res = NSS_STATUS_SUCCESS;
+
+  init();
+  pthread_mutex_lock (&host_lock);
+
+  if (host_iter >= nhost_data)
+    {
+      res = NSS_STATUS_NOTFOUND;
+      *result = NULL;
+    }
+  else
+    {
+      res = copy_host (ret, &CURHOST, buffer, buflen, errnop);
+      *result = ret;
+      ++host_iter;
+    }
+
+  pthread_mutex_unlock (&host_lock);
+
+  return res;
+}
+
+enum nss_status
+NAME(gethostbyname3_r) (const char *name, int af, struct hostent *ret,
+			     char *buffer, size_t buflen, int *errnop,
+			     int *h_errnop, int32_t *ttlp, char **canonp)
+{
+  init();
+
+  for (size_t idx = 0; idx < nhost_data; ++idx)
+    if (strcmp (host_data[idx].h_name, name) == 0)
+      return copy_host (ret, & host_data[idx], buffer, buflen, h_errnop);
+
+  return NSS_STATUS_NOTFOUND;
+}
+
+enum nss_status
+NAME(gethostbyname_r) (const char *name, struct hostent *result,
+		       char *buffer, size_t buflen,
+		       int *errnop, int *h_errnop)
+{
+  return NAME(gethostbyname3_r) (name, AF_INET, result, buffer, buflen,
+				 errnop, h_errnop, NULL, NULL);
+}
+
+enum nss_status
+NAME(gethostbyname2_r) (const char *name, int af, struct hostent *result,
+			char *buffer, size_t buflen,
+			int *errnop, int *h_errnop)
+{
+  return NAME(gethostbyname3_r) (name, af, result, buffer, buflen,
+				 errnop, h_errnop, NULL, NULL);
+}
+
+enum nss_status
+NAME(gethostbyaddr2_r) (const void *addr, socklen_t len, int af,
+			struct hostent *result, char *buffer, size_t buflen,
+			int *errnop, int *h_errnop, int32_t *ttlp)
+{
+  init();
+
+  /* Support this later.  */
+  if (len != 4)
+    return NSS_STATUS_NOTFOUND;
+
+  for (size_t idx = 0; idx < nhost_data; ++idx)
+    if (memcmp (host_data[idx].h_addr, addr, len) == 0)
+      return copy_host (result, & host_data[idx], buffer, buflen, h_errnop);
+
+  return NSS_STATUS_NOTFOUND;
+}
+
+/* Note: only the first address is supported, intentionally.  */
+enum nss_status
+NAME(gethostbyaddr_r) (const void *addr, socklen_t len, int af,
+		       struct hostent *result, char *buffer, size_t buflen,
+		       int *errnop, int *h_errnop)
+{
+  return NAME(gethostbyaddr2_r) (addr, len, af, result, buffer, buflen,
+				 errnop, h_errnop, NULL);
+}
diff --git a/nss/tst-reload1.c b/nss/tst-reload1.c
new file mode 100644
index 0000000000..b17b11d9da
--- /dev/null
+++ b/nss/tst-reload1.c
@@ -0,0 +1,341 @@
+/* Test that nsswitch.conf reloading actually works.
+   Copyright (C) 2020 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
+   <https://www.gnu.org/licenses/>.  */
+
+#include <nss.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <sys/types.h>
+#include <errno.h>
+#include <pwd.h>
+
+#include <support/support.h>
+#include <support/check.h>
+
+#include "nss_test.h"
+
+/* Size of buffers used by *_r functions.  */
+#define TESTBUFLEN 4096
+
+static struct passwd pwd_table_1[] = {
+    PWD (100),
+    PWD (30),
+    PWD (200),
+    PWD (60),
+    PWD (20000),
+    PWD_LAST ()
+  };
+
+static const char *hostaddr_5[] =
+  {
+   "ABCD", "abcd", "1234", NULL
+  };
+
+static const char *hostaddr_15[] =
+  {
+   "4321", "ghij", NULL
+  };
+
+static const char *hostaddr_25[] =
+  {
+   "WXYZ", NULL
+  };
+
+
+static struct hostent host_table_1[] = {
+  HOST (5),
+  HOST (15),
+  HOST (25),
+  HOST_LAST ()
+};
+
+void
+_nss_test1_init_hook(test_tables *t)
+{
+  t->pwd_table = pwd_table_1;
+  t->host_table = host_table_1;
+}
+
+/* The first of these must not appear in pwd_table_1.  */
+static struct passwd pwd_table_2[] = {
+    PWD (5),
+    PWD_N(200, "name30"),
+    PWD (16),
+    PWD_LAST ()
+  };
+
+static const char *hostaddr_6[] =
+  {
+   "mnop", NULL
+  };
+
+static const char *hostaddr_16[] =
+  {
+   "7890", "a1b2", NULL
+  };
+
+static const char *hostaddr_26[] =
+  {
+   "qwer", "tyui", NULL
+  };
+
+static struct hostent host_table_2[] = {
+  HOST (6),
+  HOST (16),
+  HOST (26),
+  HOST_LAST ()
+};
+
+void
+_nss_test2_init_hook(test_tables *t)
+{
+  t->pwd_table = pwd_table_2;
+  t->host_table = host_table_2;
+}
+
+static void
+must_be_tests (struct passwd *pt, struct hostent *ht)
+{
+  int i;
+  struct hostent *h;
+
+  struct passwd *p;
+  for (i = 0; !PWD_ISLAST (&pt[i]); ++ i)
+    {
+      p = getpwuid (pt[i].pw_uid);
+      TEST_VERIFY (p != NULL);
+      if (p != NULL)
+	{
+	  TEST_VERIFY (strcmp (p->pw_name, pt[i].pw_name) == 0);
+	}
+    }
+
+  setpwent ();
+  for (i = 0; !PWD_ISLAST (&pt[i]); ++ i)
+    {
+      p = getpwent ();
+      TEST_VERIFY (p != NULL);
+      if (p != NULL)
+	{
+	  TEST_VERIFY (strcmp (p->pw_name, pt[i].pw_name) == 0);
+	  TEST_VERIFY (p->pw_uid == pt[i].pw_uid);
+	}
+    }
+  endpwent ();
+
+  for (i = 0; !HOST_ISLAST (&ht[i]); ++ i)
+    {
+      h = gethostbyname (ht[i].h_name);
+      TEST_VERIFY (h != NULL);
+      if (h != NULL)
+	{
+	  TEST_VERIFY (strcmp (h->h_name, ht[i].h_name) == 0);
+	  TEST_VERIFY (h->h_addr_list[0] != NULL);
+	  if (h->h_addr_list[0])
+	    TEST_VERIFY (strcmp (h->h_addr_list[0], ht[i].h_addr_list[0]) == 0);
+	}
+    }
+
+  for (i = 0; !HOST_ISLAST (&ht[i]); ++ i)
+    {
+      struct hostent r, *rp;
+      char buf[TESTBUFLEN];
+      int herrno, res;
+
+      res = gethostbyname2_r (ht[i].h_name, AF_INET,
+			    &r, buf, TESTBUFLEN, &rp, &herrno);
+      TEST_VERIFY (res == 0);
+      if (res == 0)
+	{
+	  TEST_VERIFY (strcmp (r.h_name, ht[i].h_name) == 0);
+	  TEST_VERIFY (r.h_addr_list[0] != NULL);
+	  if (r.h_addr_list[0])
+	    TEST_VERIFY (strcmp (r.h_addr_list[0], ht[i].h_addr_list[0]) == 0);
+	}
+    }
+
+  for (i = 0; !HOST_ISLAST (&ht[i]); ++ i)
+    {
+      h = gethostbyaddr (ht[i].h_addr, 4, AF_INET);
+      TEST_VERIFY (h != NULL);
+      if (h != NULL)
+	{
+	  TEST_VERIFY (strcmp (h->h_name, ht[i].h_name) == 0);
+	  TEST_VERIFY (h->h_addr_list[0] != NULL);
+	  if (h->h_addr_list[0])
+	    TEST_VERIFY (strcmp (h->h_addr_list[0], ht[i].h_addr_list[0]) == 0);
+	}
+    }
+
+  /* getaddrinfo */
+
+  for (i = 0; !HOST_ISLAST (&ht[i]); ++ i)
+    {
+      struct addrinfo *ap;
+      struct addrinfo hint;
+      int res, j;
+
+      memset (&hint, 0, sizeof (hint));
+      hint.ai_family = AF_INET;
+      hint.ai_socktype = SOCK_STREAM;
+      hint.ai_protocol = 0;
+      hint.ai_flags = 0;
+
+      ap = NULL;
+      res = getaddrinfo (ht[i].h_name, NULL, &hint, &ap);
+      TEST_VERIFY (res == 0);
+      TEST_VERIFY (ap != NULL);
+      if (res == 0 && ap != NULL)
+	{
+	  j = 0; /* which address in the list */
+	  while (ap)
+	    {
+	      struct sockaddr_in *in = (struct sockaddr_in *)ap->ai_addr;
+	      unsigned char *up = (unsigned char *)&in->sin_addr;
+
+	      TEST_VERIFY (memcmp (up, ht[i].h_addr_list[j], 4) == 0);
+
+	      ap = ap->ai_next;
+	      ++ j;
+	    }
+	}
+    }
+
+  /* getnameinfo */
+
+  for (i = 0; !HOST_ISLAST (&ht[i]); ++ i)
+    {
+      struct sockaddr_in addr;
+      int res;
+      char host_buf[NI_MAXHOST];
+
+      memset (&addr, 0, sizeof (addr));
+      addr.sin_family = AF_INET;
+      addr.sin_port = 80;
+      memcpy (& addr.sin_addr, ht[i].h_addr_list[0], 4);
+
+      res = getnameinfo ((struct sockaddr *) &addr, sizeof(addr),
+			 host_buf, sizeof(host_buf),
+			 NULL, 0, NI_NOFQDN);
+
+      TEST_VERIFY (res == 0);
+      if (res == 0)
+	TEST_VERIFY (strcmp (ht[i].h_name, host_buf) == 0);
+      else
+	printf ("error %s\n", gai_strerror (res));
+    }
+}
+
+static void
+must_be_1 (void)
+{
+  struct passwd *p;
+
+  must_be_tests (pwd_table_1, host_table_1);
+  p = getpwnam("name5");
+  TEST_VERIFY (p == NULL);
+}
+
+static void
+must_be_2 (void)
+{
+  struct passwd *p;
+
+  must_be_tests (pwd_table_2, host_table_2);
+  p = getpwnam("name100");
+  TEST_VERIFY (p == NULL);
+}
+
+static void
+xrename (const char *a, const char *b)
+{
+  int i = rename (a, b);
+  if (i != 0)
+    FAIL_EXIT1 ("rename(%s,%s) failed: %s\n", a, b, strerror(errno));
+}
+
+/* If the actions change while in the midst of doing a series of
+   lookups, make sure they're consistent.  */
+static void
+test_cross_switch_consistency (void)
+{
+  int i;
+  struct passwd *p;
+
+  /* We start by initiating a set/get/end loop on conf1.  */
+  setpwent ();
+  for (i = 0; !PWD_ISLAST (&pwd_table_1[i]); ++ i)
+    {
+      p = getpwent ();
+      TEST_VERIFY (p != NULL);
+      if (p != NULL)
+	{
+	  TEST_VERIFY (strcmp (p->pw_name, pwd_table_1[i].pw_name) == 0);
+	  TEST_VERIFY (p->pw_uid == pwd_table_1[i].pw_uid);
+	}
+
+      /* After the first lookup, switch to conf2 and verify */
+      if (i == 0)
+	{
+	  xrename ("/etc/nsswitch.conf", "/etc/nsswitch.conf1");
+	  xrename ("/etc/nsswitch.conf2", "/etc/nsswitch.conf");
+
+	  p = getpwnam (pwd_table_2[0].pw_name);
+	  TEST_VERIFY (p->pw_uid == pwd_table_2[0].pw_uid);
+	}
+
+      /* But the original loop should still be on conf1.  */
+    }
+  endpwent ();
+
+  /* Make sure the set/get/end loop sees conf2 now.  */
+  setpwent ();
+  for (i = 0; !PWD_ISLAST (&pwd_table_2[i]); ++ i)
+    {
+      p = getpwent ();
+      TEST_VERIFY (p != NULL);
+      if (p != NULL)
+	{
+	  TEST_VERIFY (strcmp (p->pw_name, pwd_table_2[i].pw_name) == 0);
+	  TEST_VERIFY (p->pw_uid == pwd_table_2[i].pw_uid);
+	}
+    }
+  endpwent ();
+
+}
+
+static int
+do_test (void)
+{
+  /* The test1 module was configured at program start.  */
+  must_be_1 ();
+
+  xrename ("/etc/nsswitch.conf", "/etc/nsswitch.conf1");
+  xrename ("/etc/nsswitch.conf2", "/etc/nsswitch.conf");
+  must_be_2 ();
+
+  xrename ("/etc/nsswitch.conf", "/etc/nsswitch.conf2");
+  xrename ("/etc/nsswitch.conf1", "/etc/nsswitch.conf");
+  must_be_1 ();
+
+  test_cross_switch_consistency ();
+
+  return 0;
+}
+
+#include <support/test-driver.c>
diff --git a/nss/tst-reload1.root/etc/nsswitch.conf b/nss/tst-reload1.root/etc/nsswitch.conf
new file mode 100644
index 0000000000..606d8f51d6
--- /dev/null
+++ b/nss/tst-reload1.root/etc/nsswitch.conf
@@ -0,0 +1,3 @@
+passwd:	test1
+group:	test1
+hosts:	test1
diff --git a/nss/tst-reload1.root/etc/nsswitch.conf2 b/nss/tst-reload1.root/etc/nsswitch.conf2
new file mode 100644
index 0000000000..2e93977efb
--- /dev/null
+++ b/nss/tst-reload1.root/etc/nsswitch.conf2
@@ -0,0 +1,3 @@
+passwd:	test2
+group:	test2
+hosts:	test2
diff --git a/nss/tst-reload1.root/etc/services b/nss/tst-reload1.root/etc/services
new file mode 100644
index 0000000000..94d4f07612
--- /dev/null
+++ b/nss/tst-reload1.root/etc/services
@@ -0,0 +1 @@
+http 80/tcp
diff --git a/nss/tst-reload1.root/tst-reload1.script b/nss/tst-reload1.root/tst-reload1.script
new file mode 100644
index 0000000000..a10beb1e6c
--- /dev/null
+++ b/nss/tst-reload1.root/tst-reload1.script
@@ -0,0 +1,2 @@
+cp $B/nss/libnss_test1.so $L/libnss_test1.so.2
+cp $B/nss/libnss_test2.so $L/libnss_test2.so.2
