Merge pull request #2947 from keszybz/test-nss

Add a test for nss modules and some related fixes

6 files changed, 565 insertions, 97 deletions

diff --git a/src/basic/nss-util.h b/src/basic/nss-util.h
index df565a3593..bf7c4854fc 100644
--- a/src/basic/nss-util.h
+++ b/src/basic/nss-util.h
@@ -154,3 +154,46 @@ enum nss_status _nss_##module##_getgrgid_r(             \
                 struct group *gr,                       \
                 char *buffer, size_t buflen,            \
                 int *errnop) _public_
+
+typedef enum nss_status (*_nss_gethostbyname4_r_t)(
+                const char *name,
+                struct gaih_addrtuple **pat,
+                char *buffer, size_t buflen,
+                int *errnop, int *h_errnop,
+                int32_t *ttlp);
+
+typedef enum nss_status (*_nss_gethostbyname3_r_t)(
+                const char *name,
+                int af,
+                struct hostent *result,
+                char *buffer, size_t buflen,
+                int *errnop, int *h_errnop,
+                int32_t *ttlp,
+                char **canonp);
+
+typedef enum nss_status (*_nss_gethostbyname2_r_t)(
+                const char *name,
+                int af,
+                struct hostent *result,
+                char *buffer, size_t buflen,
+                int *errnop, int *h_errnop);
+
+typedef enum nss_status (*_nss_gethostbyname_r_t)(
+                const char *name,
+                struct hostent *result,
+                char *buffer, size_t buflen,
+                int *errnop, int *h_errnop);
+
+typedef enum nss_status (*_nss_gethostbyaddr2_r_t)(
+                const void* addr, socklen_t len,
+                int af,
+                struct hostent *result,
+                char *buffer, size_t buflen,
+                int *errnop, int *h_errnop,
+                int32_t *ttlp);
+typedef enum nss_status (*_nss_gethostbyaddr_r_t)(
+                const void* addr, socklen_t len,
+                int af,
+                struct hostent *host,
+                char *buffer, size_t buflen,
+                int *errnop, int *h_errnop);
diff --git a/src/basic/string-table.h b/src/basic/string-table.h
index b180488fe8..d88625fca7 100644
--- a/src/basic/string-table.h
+++ b/src/basic/string-table.h
@@ -56,26 +56,8 @@ ssize_t string_table_lookup(const char * const *table, size_t len, const char *k
                 return (type) string_table_lookup(name##_table, ELEMENTSOF(name##_table), s); \
         }
 
-#define _DEFINE_STRING_TABLE_LOOKUP(name,type,scope)                    \
-        _DEFINE_STRING_TABLE_LOOKUP_TO_STRING(name,type,scope)          \
-        _DEFINE_STRING_TABLE_LOOKUP_FROM_STRING(name,type,scope)        \
-        struct __useless_struct_to_allow_trailing_semicolon__
-
-#define _DEFINE_STRING_TABLE_LOOKUP_WITH_BOOLEAN(name,type,yes,scope)   \
-        _DEFINE_STRING_TABLE_LOOKUP_TO_STRING(name,type,scope)          \
-        _DEFINE_STRING_TABLE_LOOKUP_FROM_STRING_WITH_BOOLEAN(name,type,yes,scope) \
-        struct __useless_struct_to_allow_trailing_semicolon__
-
-#define DEFINE_STRING_TABLE_LOOKUP(name,type) _DEFINE_STRING_TABLE_LOOKUP(name,type,)
-#define DEFINE_PRIVATE_STRING_TABLE_LOOKUP(name,type) _DEFINE_STRING_TABLE_LOOKUP(name,type,static)
-#define DEFINE_PRIVATE_STRING_TABLE_LOOKUP_TO_STRING(name,type) _DEFINE_STRING_TABLE_LOOKUP_TO_STRING(name,type,static)
-#define DEFINE_PRIVATE_STRING_TABLE_LOOKUP_FROM_STRING(name,type) _DEFINE_STRING_TABLE_LOOKUP_FROM_STRING(name,type,static)
-
-#define DEFINE_STRING_TABLE_LOOKUP_WITH_BOOLEAN(name,type,yes) _DEFINE_STRING_TABLE_LOOKUP_WITH_BOOLEAN(name,type,yes,)
-
-/* For string conversions where numbers are also acceptable */
-#define DEFINE_STRING_TABLE_LOOKUP_WITH_FALLBACK(name,type,max)         \
-        int name##_to_string_alloc(type i, char **str) {                \
+#define _DEFINE_STRING_TABLE_LOOKUP_TO_STRING_FALLBACK(name,type,max,scope) \
+        scope int name##_to_string_alloc(type i, char **str) {          \
                 char *s;                                                \
                 if (i < 0 || i > max)                                   \
                         return -ERANGE;                                 \
@@ -89,7 +71,9 @@ ssize_t string_table_lookup(const char * const *table, size_t len, const char *k
                 }                                                       \
                 *str = s;                                               \
                 return 0;                                               \
-        }                                                               \
+        }
+
+#define _DEFINE_STRING_TABLE_LOOKUP_FROM_STRING_FALLBACK(name,type,max,scope) \
         type name##_from_string(const char *s) {                        \
                 type i;                                                 \
                 unsigned u = 0;                                         \
@@ -102,4 +86,32 @@ ssize_t string_table_lookup(const char * const *table, size_t len, const char *k
                         return (type) u;                                \
                 return (type) -1;                                       \
         }                                                               \
+
+
+#define _DEFINE_STRING_TABLE_LOOKUP(name,type,scope)                    \
+        _DEFINE_STRING_TABLE_LOOKUP_TO_STRING(name,type,scope)          \
+        _DEFINE_STRING_TABLE_LOOKUP_FROM_STRING(name,type,scope)        \
+        struct __useless_struct_to_allow_trailing_semicolon__
+
+#define _DEFINE_STRING_TABLE_LOOKUP_WITH_BOOLEAN(name,type,yes,scope)   \
+        _DEFINE_STRING_TABLE_LOOKUP_TO_STRING(name,type,scope)          \
+        _DEFINE_STRING_TABLE_LOOKUP_FROM_STRING_WITH_BOOLEAN(name,type,yes,scope) \
+        struct __useless_struct_to_allow_trailing_semicolon__
+
+#define DEFINE_STRING_TABLE_LOOKUP(name,type) _DEFINE_STRING_TABLE_LOOKUP(name,type,)
+#define DEFINE_PRIVATE_STRING_TABLE_LOOKUP(name,type) _DEFINE_STRING_TABLE_LOOKUP(name,type,static)
+#define DEFINE_PRIVATE_STRING_TABLE_LOOKUP_TO_STRING(name,type) _DEFINE_STRING_TABLE_LOOKUP_TO_STRING(name,type,static)
+#define DEFINE_PRIVATE_STRING_TABLE_LOOKUP_FROM_STRING(name,type) _DEFINE_STRING_TABLE_LOOKUP_FROM_STRING(name,type,static)
+
+#define DEFINE_STRING_TABLE_LOOKUP_WITH_BOOLEAN(name,type,yes) _DEFINE_STRING_TABLE_LOOKUP_WITH_BOOLEAN(name,type,yes,)
+
+/* For string conversions where numbers are also acceptable */
+#define DEFINE_STRING_TABLE_LOOKUP_WITH_FALLBACK(name,type,max)         \
+        _DEFINE_STRING_TABLE_LOOKUP_TO_STRING_FALLBACK(name,type,max,)  \
+        _DEFINE_STRING_TABLE_LOOKUP_FROM_STRING_FALLBACK(name,type,max,) \
         struct __useless_struct_to_allow_trailing_semicolon__
+
+#define DEFINE_PRIVATE_STRING_TABLE_LOOKUP_TO_STRING_FALLBACK(name,type,max) \
+        _DEFINE_STRING_TABLE_LOOKUP_TO_STRING_FALLBACK(name,type,max,static)
+#define DEFINE_PRIVATE_STRING_TABLE_LOOKUP_FROM_STRING_FALLBACK(name,type,max) \
+        _DEFINE_STRING_TABLE_LOOKUP_FROM_STRING_FALLBACK(name,type,max,static)
diff --git a/src/libsystemd/sd-netlink/local-addresses.c b/src/libsystemd/sd-netlink/local-addresses.c
index 6abd8fd0cc..ed9ee041ab 100644
--- a/src/libsystemd/sd-netlink/local-addresses.c
+++ b/src/libsystemd/sd-netlink/local-addresses.c
@@ -155,8 +155,7 @@ int local_addresses(sd_netlink *context, int ifindex, int af, struct local_addre
                 n_list++;
         };
 
-        if (n_list > 0)
-                qsort(list, n_list, sizeof(struct local_address), address_compare);
+        qsort_safe(list, n_list, sizeof(struct local_address), address_compare);
 
         *ret = list;
         list = NULL;
diff --git a/src/nss-myhostname/nss-myhostname.c b/src/nss-myhostname/nss-myhostname.c
index 2536ad2898..2b83d127b7 100644
--- a/src/nss-myhostname/nss-myhostname.c
+++ b/src/nss-myhostname/nss-myhostname.c
@@ -127,7 +127,8 @@ enum nss_status _nss_myhostname_gethostbyname4_r(
         memcpy(r_name, canonical, l+1);
         idx = ALIGN(l+1);
 
-        if (n_addresses <= 0) {
+        assert(n_addresses >= 0);
+        if (n_addresses == 0) {
                 /* Second, fill in IPv6 tuple */
                 r_tuple = (struct gaih_addrtuple*) (buffer + idx);
                 r_tuple->next = r_tuple_prev;
@@ -453,38 +454,33 @@ enum nss_status _nss_myhostname_gethostbyaddr2_r(
         }
 
         n_addresses = local_addresses(NULL, 0, AF_UNSPEC, &addresses);
-        if (n_addresses > 0) {
-                for (a = addresses, n = 0; (int) n < n_addresses; n++, a++) {
-                        if (af != a->family)
-                                continue;
+        for (a = addresses, n = 0; (int) n < n_addresses; n++, a++) {
+                if (af != a->family)
+                        continue;
 
-                        if (memcmp(addr, &a->address, FAMILY_ADDRESS_SIZE(af)) == 0)
-                                goto found;
-                }
+                if (memcmp(addr, &a->address, FAMILY_ADDRESS_SIZE(af)) == 0)
+                        goto found;
         }
 
         addresses = mfree(addresses);
 
         n_addresses = local_gateways(NULL, 0, AF_UNSPEC, &addresses);
-        if (n_addresses > 0) {
-                for (a = addresses, n = 0; (int) n < n_addresses; n++, a++) {
-                        if (af != a->family)
-                                continue;
+        for (a = addresses, n = 0; (int) n < n_addresses; n++, a++) {
+                if (af != a->family)
+                        continue;
 
-                        if (memcmp(addr, &a->address, FAMILY_ADDRESS_SIZE(af)) == 0) {
-                                canonical = "gateway";
-                                goto found;
-                        }
+                if (memcmp(addr, &a->address, FAMILY_ADDRESS_SIZE(af)) == 0) {
+                        canonical = "gateway";
+                        goto found;
                 }
         }
 
         *errnop = ENOENT;
         *h_errnop = HOST_NOT_FOUND;
-
         return NSS_STATUS_NOTFOUND;
 
 found:
-        if (!canonical || (!additional && additional_from_hostname)) {
+        if (!canonical || additional_from_hostname) {
                 hn = gethostname_malloc();
                 if (!hn) {
                         *errnop = ENOMEM;
@@ -494,8 +490,7 @@ found:
 
                 if (!canonical)
                         canonical = hn;
-
-                if (!additional && additional_from_hostname)
+                else
                         additional = hn;
         }
 
diff --git a/src/nss-resolve/nss-resolve.c b/src/nss-resolve/nss-resolve.c
index 0de6bd2241..5ce10f1cbd 100644
--- a/src/nss-resolve/nss-resolve.c
+++ b/src/nss-resolve/nss-resolve.c
@@ -117,13 +117,6 @@ enum nss_status _nss_resolve_gethostbyname4_r(
                 int *errnop, int *h_errnop,
                 int32_t *ttlp) {
 
-        enum nss_status (*fallback)(
-                        const char *name,
-                        struct gaih_addrtuple **pat,
-                        char *buffer, size_t buflen,
-                        int *errnop, int *h_errnop,
-                        int32_t *ttlp);
-
         _cleanup_(sd_bus_message_unrefp) sd_bus_message *req = NULL, *reply = NULL;
         _cleanup_(sd_bus_error_free) sd_bus_error error = SD_BUS_ERROR_NULL;
         struct gaih_addrtuple *r_tuple, *r_tuple_first = NULL;
@@ -275,15 +268,15 @@ enum nss_status _nss_resolve_gethostbyname4_r(
         return NSS_STATUS_SUCCESS;
 
 fallback:
-        fallback = (enum nss_status (*)(const char *name,
-                                        struct gaih_addrtuple **pat,
-                                        char *buffer, size_t buflen,
-                                        int *errnop, int *h_errnop,
-                                        int32_t *ttlp))
-                find_fallback("libnss_dns.so.2", "_nss_dns_gethostbyname4_r");
+        {
+                _nss_gethostbyname4_r_t fallback;
+
+                fallback = (_nss_gethostbyname4_r_t)
+                        find_fallback("libnss_dns.so.2", "_nss_dns_gethostbyname4_r");
 
-        if (fallback)
-                return fallback(name, pat, buffer, buflen, errnop, h_errnop, ttlp);
+                if (fallback)
+                        return fallback(name, pat, buffer, buflen, errnop, h_errnop, ttlp);
+        }
 
 fail:
         *errnop = -r;
@@ -300,15 +293,6 @@ enum nss_status _nss_resolve_gethostbyname3_r(
                 int32_t *ttlp,
                 char **canonp) {
 
-        enum nss_status (*fallback)(
-                        const char *name,
-                        int af,
-                        struct hostent *result,
-                        char *buffer, size_t buflen,
-                        int *errnop, int *h_errnop,
-                        int32_t *ttlp,
-                        char **canonp);
-
         _cleanup_(sd_bus_message_unrefp) sd_bus_message *req = NULL, *reply = NULL;
         _cleanup_(sd_bus_error_free) sd_bus_error error = SD_BUS_ERROR_NULL;
         char *r_name, *r_aliases, *r_addr, *r_addr_list;
@@ -480,16 +464,14 @@ enum nss_status _nss_resolve_gethostbyname3_r(
         return NSS_STATUS_SUCCESS;
 
 fallback:
-        fallback = (enum nss_status (*)(const char *name,
-                                        int af,
-                                        struct hostent *result,
-                                        char *buffer, size_t buflen,
-                                        int *errnop, int *h_errnop,
-                                        int32_t *ttlp,
-                                        char **canonp))
-                find_fallback("libnss_dns.so.2", "_nss_dns_gethostbyname3_r");
-        if (fallback)
-                return fallback(name, af, result, buffer, buflen, errnop, h_errnop, ttlp, canonp);
+        {
+                _nss_gethostbyname3_r_t fallback;
+
+                fallback = (_nss_gethostbyname3_r_t)
+                        find_fallback("libnss_dns.so.2", "_nss_dns_gethostbyname3_r");
+                if (fallback)
+                        return fallback(name, af, result, buffer, buflen, errnop, h_errnop, ttlp, canonp);
+        }
 
 fail:
         *errnop = -r;
@@ -505,15 +487,6 @@ enum nss_status _nss_resolve_gethostbyaddr2_r(
                 int *errnop, int *h_errnop,
                 int32_t *ttlp) {
 
-        enum nss_status (*fallback)(
-                        const void* addr, socklen_t len,
-                        int af,
-                        struct hostent *result,
-                        char *buffer, size_t buflen,
-                        int *errnop, int *h_errnop,
-                        int32_t *ttlp);
-
-
         _cleanup_(sd_bus_message_unrefp) sd_bus_message *req = NULL, *reply = NULL;
         _cleanup_(sd_bus_error_free) sd_bus_error error = SD_BUS_ERROR_NULL;
         char *r_name, *r_aliases, *r_addr, *r_addr_list;
@@ -682,17 +655,15 @@ enum nss_status _nss_resolve_gethostbyaddr2_r(
         return NSS_STATUS_SUCCESS;
 
 fallback:
-        fallback = (enum nss_status (*)(
-                                    const void* addr, socklen_t len,
-                                    int af,
-                                    struct hostent *result,
-                                    char *buffer, size_t buflen,
-                                    int *errnop, int *h_errnop,
-                                    int32_t *ttlp))
-                find_fallback("libnss_dns.so.2", "_nss_dns_gethostbyaddr2_r");
-
-        if (fallback)
-                return fallback(addr, len, af, result, buffer, buflen, errnop, h_errnop, ttlp);
+        {
+                _nss_gethostbyaddr2_r_t fallback;
+
+                fallback = (_nss_gethostbyaddr2_r_t)
+                        find_fallback("libnss_dns.so.2", "_nss_dns_gethostbyaddr2_r");
+
+                if (fallback)
+                        return fallback(addr, len, af, result, buffer, buflen, errnop, h_errnop, ttlp);
+        }
 
 fail:
         *errnop = -r;
diff --git a/src/test/test-nss.c b/src/test/test-nss.c
new file mode 100644
index 0000000000..9c13288d2e
--- /dev/null
+++ b/src/test/test-nss.c
@@ -0,0 +1,448 @@
+/***
+  This file is part of systemd.
+
+  Copyright 2016 Zbigniew Jędrzejewski-Szmek
+
+  systemd 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.
+
+  systemd 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 systemd; If not, see <http://www.gnu.org/licenses/>.
+***/
+
+#include <dlfcn.h>
+#include <stdlib.h>
+#include <net/if.h>
+
+#include "log.h"
+#include "nss-util.h"
+#include "path-util.h"
+#include "string-util.h"
+#include "alloc-util.h"
+#include "in-addr-util.h"
+#include "hexdecoct.h"
+#include "af-list.h"
+#include "stdio-util.h"
+#include "strv.h"
+#include "errno-list.h"
+#include "hostname-util.h"
+#include "local-addresses.h"
+
+static const char* nss_status_to_string(enum nss_status status, char *buf, size_t buf_len) {
+        switch (status) {
+        case NSS_STATUS_TRYAGAIN:
+                return "NSS_STATUS_TRYAGAIN";
+        case NSS_STATUS_UNAVAIL:
+                return "NSS_STATUS_UNAVAIL";
+        case NSS_STATUS_NOTFOUND:
+                return "NSS_STATUS_NOTFOUND";
+        case NSS_STATUS_SUCCESS:
+                return "NSS_STATUS_SUCCESS";
+        case NSS_STATUS_RETURN:
+                return "NSS_STATUS_RETURN";
+        default:
+                snprintf(buf, buf_len, "%i", status);
+                return buf;
+        }
+};
+
+static const char* af_to_string(int family, char *buf, size_t buf_len) {
+        const char *name;
+
+        if (family == AF_UNSPEC)
+                return "*";
+
+        name = af_to_name(family);
+        if (name)
+                return name;
+
+        snprintf(buf, buf_len, "%i", family);
+        return buf;
+}
+
+static void* open_handle(const char* dir, const char* module, int flags) {
+        const char *path;
+        void *handle;
+
+        if (dir)
+                path = strjoina(dir, "/.libs/libnss_", module, ".so.2");
+        else
+                path = strjoina("libnss_", module, ".so.2");
+
+        handle = dlopen(path, flags);
+        assert_se(handle);
+        return handle;
+}
+
+static int print_gaih_addrtuples(const struct gaih_addrtuple *tuples) {
+        const struct gaih_addrtuple *it;
+        int n = 0;
+
+        for (it = tuples; it; it = it->next) {
+                _cleanup_free_ char *a = NULL;
+                union in_addr_union u;
+                int r;
+                char family_name[DECIMAL_STR_MAX(int)];
+                char ifname[IF_NAMESIZE];
+
+                memcpy(&u, it->addr, 16);
+                r = in_addr_to_string(it->family, &u, &a);
+                assert_se(r == 0 || r == -EAFNOSUPPORT);
+                if (r == -EAFNOSUPPORT)
+                        assert_se((a = hexmem(it->addr, 16)));
+
+                if (it->scopeid == 0)
+                        goto numerical_index;
+
+                if (if_indextoname(it->scopeid, ifname) == NULL) {
+                        log_warning("if_indextoname(%d) failed: %m", it->scopeid);
+                numerical_index:
+                        xsprintf(ifname, "%i", it->scopeid);
+                };
+
+                log_info("        \"%s\" %s %s %%%s",
+                         it->name,
+                         af_to_string(it->family, family_name, sizeof family_name),
+                         a,
+                         ifname);
+                n ++;
+        }
+        return n;
+}
+
+static void print_struct_hostent(struct hostent *host, const char *canon) {
+        char **s;
+
+        log_info("        \"%s\"", host->h_name);
+        STRV_FOREACH(s, host->h_aliases)
+                log_info("        alias \"%s\"", *s);
+        STRV_FOREACH(s, host->h_addr_list) {
+                union in_addr_union u;
+                _cleanup_free_ char *a = NULL;
+                char family_name[DECIMAL_STR_MAX(int)];
+                int r;
+
+                assert_se((unsigned) host->h_length == FAMILY_ADDRESS_SIZE(host->h_addrtype));
+                memcpy(&u, *s, host->h_length);
+                r = in_addr_to_string(host->h_addrtype, &u, &a);
+                assert_se(r == 0);
+                log_info("        %s %s",
+                         af_to_string(host->h_addrtype, family_name, sizeof family_name),
+                         a);
+        }
+        if (canon)
+                log_info("        canonical: \"%s\"", canon);
+}
+
+static void test_gethostbyname4_r(void *handle, const char *module, const char *name) {
+        const char *fname;
+        _nss_gethostbyname4_r_t f;
+        char buffer[2000];
+        struct gaih_addrtuple *pat = NULL;
+        int errno1 = 999, errno2 = 999; /* nss-dns doesn't set those */
+        int32_t ttl = INT32_MAX; /* nss-dns wants to return the lowest ttl,
+                                    and will access this variable through *ttlp,
+                                    so we need to set it to something.
+                                    I'm not sure if this is a bug in nss-dns
+                                    or not. */
+        enum nss_status status;
+        char pretty_status[DECIMAL_STR_MAX(enum nss_status)];
+        int n;
+
+        fname = strjoina("_nss_", module, "_gethostbyname4_r");
+        f = dlsym(handle, fname);
+        log_debug("dlsym(0x%p, %s) → 0x%p", handle, fname, f);
+        assert_se(f);
+
+        status = f(name, &pat, buffer, sizeof buffer, &errno1, &errno2, &ttl);
+        if (status == NSS_STATUS_SUCCESS) {
+                log_info("%s(\"%s\") → status=%s%-20spat=buffer+0x%tx errno=%d/%s h_errno=%d/%s ttl=%"PRIi32,
+                         fname, name,
+                         nss_status_to_string(status, pretty_status, sizeof pretty_status), "\n",
+                         pat ? (char*) pat - buffer : 0,
+                         errno1, errno_to_name(errno1) ?: "---",
+                         errno2, hstrerror(errno2),
+                         ttl);
+                n = print_gaih_addrtuples(pat);
+        } else {
+                log_info("%s(\"%s\") → status=%s%-20spat=0x%p errno=%d/%s h_errno=%d/%s",
+                         fname, name,
+                         nss_status_to_string(status, pretty_status, sizeof pretty_status), "\n",
+                         pat,
+                         errno1, errno_to_name(errno1) ?: "---",
+                         errno2, hstrerror(errno2));
+                n = 0;
+        }
+
+        if (STR_IN_SET(module, "resolve", "mymachines") && status == NSS_STATUS_UNAVAIL)
+                return;
+
+        if (STR_IN_SET(module, "myhostname", "resolve") && streq(name, "localhost")) {
+                assert_se(status == NSS_STATUS_SUCCESS);
+                assert_se(n == 2);
+        }
+}
+
+
+static void test_gethostbyname3_r(void *handle, const char *module, const char *name, int af) {
+        const char *fname;
+        _nss_gethostbyname3_r_t f;
+        char buffer[2000];
+        int errno1 = 999, errno2 = 999; /* nss-dns doesn't set those */
+        int32_t ttl = INT32_MAX; /* nss-dns wants to return the lowest ttl,
+                                    and will access this variable through *ttlp,
+                                    so we need to set it to something.
+                                    I'm not sure if this is a bug in nss-dns
+                                    or not. */
+        enum nss_status status;
+        char pretty_status[DECIMAL_STR_MAX(enum nss_status)];
+        struct hostent host;
+        char *canon;
+        char family_name[DECIMAL_STR_MAX(int)];
+
+        fname = strjoina("_nss_", module, "_gethostbyname3_r");
+        f = dlsym(handle, fname);
+        log_debug("dlsym(0x%p, %s) → 0x%p", handle, fname, f);
+        assert_se(f);
+
+        status = f(name, af, &host, buffer, sizeof buffer, &errno1, &errno2, &ttl, &canon);
+        log_info("%s(\"%s\", %s) → status=%s%-20serrno=%d/%s h_errno=%d/%s ttl=%"PRIi32,
+                 fname, name, af_to_string(af, family_name, sizeof family_name),
+                 nss_status_to_string(status, pretty_status, sizeof pretty_status), "\n",
+                 errno1, errno_to_name(errno1) ?: "---",
+                 errno2, hstrerror(errno2),
+                 ttl);
+        if (status == NSS_STATUS_SUCCESS)
+                print_struct_hostent(&host, canon);
+}
+
+static void test_gethostbyname2_r(void *handle, const char *module, const char *name, int af) {
+        const char *fname;
+        _nss_gethostbyname2_r_t f;
+        char buffer[2000];
+        int errno1 = 999, errno2 = 999; /* nss-dns doesn't set those */
+        enum nss_status status;
+        char pretty_status[DECIMAL_STR_MAX(enum nss_status)];
+        struct hostent host;
+        char family_name[DECIMAL_STR_MAX(int)];
+
+        fname = strjoina("_nss_", module, "_gethostbyname2_r");
+        f = dlsym(handle, fname);
+        log_debug("dlsym(0x%p, %s) → 0x%p", handle, fname, f);
+        assert_se(f);
+
+        status = f(name, af, &host, buffer, sizeof buffer, &errno1, &errno2);
+        log_info("%s(\"%s\", %s) → status=%s%-20serrno=%d/%s h_errno=%d/%s",
+                 fname, name, af_to_string(af, family_name, sizeof family_name),
+                 nss_status_to_string(status, pretty_status, sizeof pretty_status), "\n",
+                 errno1, errno_to_name(errno1) ?: "---",
+                 errno2, hstrerror(errno2));
+        if (status == NSS_STATUS_SUCCESS)
+                print_struct_hostent(&host, NULL);
+}
+
+static void test_gethostbyname_r(void *handle, const char *module, const char *name) {
+        const char *fname;
+        _nss_gethostbyname_r_t f;
+        char buffer[2000];
+        int errno1 = 999, errno2 = 999; /* nss-dns doesn't set those */
+        enum nss_status status;
+        char pretty_status[DECIMAL_STR_MAX(enum nss_status)];
+        struct hostent host;
+
+        fname = strjoina("_nss_", module, "_gethostbyname_r");
+        f = dlsym(handle, fname);
+        log_debug("dlsym(0x%p, %s) → 0x%p", handle, fname, f);
+        assert_se(f);
+
+        status = f(name, &host, buffer, sizeof buffer, &errno1, &errno2);
+        log_info("%s(\"%s\") → status=%s%-20serrno=%d/%s h_errno=%d/%s",
+                 fname, name,
+                 nss_status_to_string(status, pretty_status, sizeof pretty_status), "\n",
+                 errno1, errno_to_name(errno1) ?: "---",
+                 errno2, hstrerror(errno2));
+        if (status == NSS_STATUS_SUCCESS)
+                print_struct_hostent(&host, NULL);
+}
+
+static void test_gethostbyaddr2_r(void *handle,
+                                  const char *module,
+                                  const void* addr, socklen_t len,
+                                  int af) {
+
+        const char *fname;
+        _nss_gethostbyaddr2_r_t f;
+        char buffer[2000];
+        int errno1 = 999, errno2 = 999; /* nss-dns doesn't set those */
+        enum nss_status status;
+        char pretty_status[DECIMAL_STR_MAX(enum nss_status)];
+        struct hostent host;
+        int32_t ttl = INT32_MAX;
+        _cleanup_free_ char *addr_pretty = NULL;
+
+        fname = strjoina("_nss_", module, "_gethostbyaddr2_r");
+        f = dlsym(handle, fname);
+
+        log_full_errno(f ? LOG_DEBUG : LOG_INFO,  errno,
+                       "dlsym(0x%p, %s) → 0x%p: %m", handle, fname, f);
+        if (!f)
+                return;
+
+        assert_se(in_addr_to_string(af, addr, &addr_pretty) >= 0);
+
+        status = f(addr, len, af, &host, buffer, sizeof buffer, &errno1, &errno2, &ttl);
+        log_info("%s(\"%s\") → status=%s%-20serrno=%d/%s h_errno=%d/%s ttl=%"PRIi32,
+                 fname, addr_pretty,
+                 nss_status_to_string(status, pretty_status, sizeof pretty_status), "\n",
+                 errno1, errno_to_name(errno1) ?: "---",
+                 errno2, hstrerror(errno2),
+                 ttl);
+        if (status == NSS_STATUS_SUCCESS)
+                print_struct_hostent(&host, NULL);
+}
+
+static void test_gethostbyaddr_r(void *handle,
+                                 const char *module,
+                                 const void* addr, socklen_t len,
+                                 int af) {
+
+        const char *fname;
+        _nss_gethostbyaddr_r_t f;
+        char buffer[2000];
+        int errno1 = 999, errno2 = 999; /* nss-dns doesn't set those */
+        enum nss_status status;
+        char pretty_status[DECIMAL_STR_MAX(enum nss_status)];
+        struct hostent host;
+        _cleanup_free_ char *addr_pretty = NULL;
+
+        fname = strjoina("_nss_", module, "_gethostbyaddr_r");
+        f = dlsym(handle, fname);
+
+        log_full_errno(f ? LOG_DEBUG : LOG_INFO,  errno,
+                       "dlsym(0x%p, %s) → 0x%p: %m", handle, fname, f);
+        if (!f)
+                return;
+
+        assert_se(in_addr_to_string(af, addr, &addr_pretty) >= 0);
+
+        status = f(addr, len, af, &host, buffer, sizeof buffer, &errno1, &errno2);
+        log_info("%s(\"%s\") → status=%s%-20serrno=%d/%s h_errno=%d/%s",
+                 fname, addr_pretty,
+                 nss_status_to_string(status, pretty_status, sizeof pretty_status), "\n",
+                 errno1, errno_to_name(errno1) ?: "---",
+                 errno2, hstrerror(errno2));
+        if (status == NSS_STATUS_SUCCESS)
+                print_struct_hostent(&host, NULL);
+}
+
+static void test_byname(void *handle, const char *module, const char *name) {
+        test_gethostbyname4_r(handle, module, name);
+        puts("");
+
+        test_gethostbyname3_r(handle, module, name, AF_INET);
+        puts("");
+        test_gethostbyname3_r(handle, module, name, AF_INET6);
+        puts("");
+        test_gethostbyname3_r(handle, module, name, AF_UNSPEC);
+        puts("");
+        test_gethostbyname3_r(handle, module, name, AF_LOCAL);
+        puts("");
+
+        test_gethostbyname2_r(handle, module, name, AF_INET);
+        puts("");
+        test_gethostbyname2_r(handle, module, name, AF_INET6);
+        puts("");
+        test_gethostbyname2_r(handle, module, name, AF_UNSPEC);
+        puts("");
+        test_gethostbyname2_r(handle, module, name, AF_LOCAL);
+        puts("");
+
+        test_gethostbyname_r(handle, module, name);
+        puts("");
+}
+
+static void test_byaddr(void *handle,
+                        const char *module,
+                        const void* addr, socklen_t len,
+                        int af) {
+        test_gethostbyaddr2_r(handle, module, addr, len, af);
+        puts("");
+
+        test_gethostbyaddr_r(handle, module, addr, len, af);
+        puts("");
+}
+
+#ifdef HAVE_MYHOSTNAME
+#  define MODULE1 "myhostname\0"
+#endif
+#ifdef HAVE_RESOLVED
+#  define MODULE2 "resolve\0"
+#endif
+#ifdef HAVE_MACHINED
+#  define MODULE3 "mymachines\0"
+#endif
+#define MODULE4 "dns\0"
+
+int main(int argc, char **argv) {
+        _cleanup_free_ char *dir = NULL, *hostname = NULL;
+        const char *module;
+
+        const uint32_t local_address_ipv4 = htonl(0x7F000001);
+        const uint32_t local_address_ipv4_2 = htonl(0x7F000002);
+        _cleanup_free_ struct local_address *addresses = NULL;
+        int n_addresses;
+
+        log_set_max_level(LOG_INFO);
+        log_parse_environment();
+
+        dir = dirname_malloc(argv[0]);
+        assert_se(dir);
+
+        hostname = gethostname_malloc();
+        assert_se(hostname);
+
+        n_addresses = local_addresses(NULL, 0, AF_UNSPEC, &addresses);
+        if (n_addresses < 0) {
+                log_info_errno(n_addresses, "Failed to query local addresses: %m");
+                n_addresses = 0;
+        }
+
+        NULSTR_FOREACH(module, MODULE1 MODULE2 MODULE3 MODULE4) {
+                void *handle;
+                const char *name;
+                int i;
+
+                log_info("======== %s ========", module);
+
+                handle = open_handle(streq(module, "dns") ? NULL : dir,
+                                     module,
+                                     RTLD_LAZY|RTLD_NODELETE);
+                NULSTR_FOREACH(name, "localhost\0" "gateway\0" "foo_no_such_host\0")
+                        test_byname(handle, module, name);
+
+                test_byname(handle, module, hostname);
+
+                test_byaddr(handle, module, &local_address_ipv4, sizeof local_address_ipv4, AF_INET);
+                test_byaddr(handle, module, &local_address_ipv4_2, sizeof local_address_ipv4_2, AF_INET);
+                test_byaddr(handle, module, &in6addr_loopback, sizeof in6addr_loopback, AF_INET6);
+
+                for (i = 0; i < n_addresses; i++)
+                        test_byaddr(handle, module,
+                                    &addresses[i].address,
+                                    FAMILY_ADDRESS_SIZE(addresses[i].family),
+                                    addresses[i].family);
+
+                dlclose(handle);
+
+                log_info(" ");
+        }
+
+        return EXIT_SUCCESS;
+}