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authorDaniel Baumann <daniel.baumann@progress-linux.org>2024-04-10 20:49:52 +0000
committerDaniel Baumann <daniel.baumann@progress-linux.org>2024-04-10 20:49:52 +0000
commit55944e5e40b1be2afc4855d8d2baf4b73d1876b5 (patch)
tree33f869f55a1b149e9b7c2b7e201867ca5dd52992 /src/nss-resolve
parentInitial commit. (diff)
downloadsystemd-55944e5e40b1be2afc4855d8d2baf4b73d1876b5.tar.xz
systemd-55944e5e40b1be2afc4855d8d2baf4b73d1876b5.zip
Adding upstream version 255.4.upstream/255.4
Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>
Diffstat (limited to 'src/nss-resolve')
-rw-r--r--src/nss-resolve/meson.build12
-rw-r--r--src/nss-resolve/nss-resolve.c759
-rw-r--r--src/nss-resolve/nss-resolve.sym19
3 files changed, 790 insertions, 0 deletions
diff --git a/src/nss-resolve/meson.build b/src/nss-resolve/meson.build
new file mode 100644
index 0000000..1fae426
--- /dev/null
+++ b/src/nss-resolve/meson.build
@@ -0,0 +1,12 @@
+# SPDX-License-Identifier: LGPL-2.1-or-later
+
+modules += [
+ nss_template + {
+ 'name' : 'nss_resolve',
+ 'conditions' : ['ENABLE_NSS_RESOLVE'],
+ 'sources' : files('nss-resolve.c'),
+ 'version-script' : meson.current_source_dir() / 'nss-resolve.sym',
+ 'include_directories' : includes +
+ include_directories('../resolve'),
+ },
+]
diff --git a/src/nss-resolve/nss-resolve.c b/src/nss-resolve/nss-resolve.c
new file mode 100644
index 0000000..c4e02bc
--- /dev/null
+++ b/src/nss-resolve/nss-resolve.c
@@ -0,0 +1,759 @@
+/* SPDX-License-Identifier: LGPL-2.1-or-later */
+
+#include <errno.h>
+#include <netdb.h>
+#include <nss.h>
+#include <pthread.h>
+#include <stdlib.h>
+#include <sys/types.h>
+#include <unistd.h>
+
+#include "env-util.h"
+#include "errno-util.h"
+#include "glyph-util.h"
+#include "in-addr-util.h"
+#include "macro.h"
+#include "nss-util.h"
+#include "resolved-def.h"
+#include "signal-util.h"
+#include "string-util.h"
+#include "strv.h"
+#include "varlink.h"
+
+static JsonDispatchFlags json_dispatch_flags = 0;
+
+static void setup_logging(void) {
+ log_parse_environment_variables();
+
+ if (DEBUG_LOGGING)
+ json_dispatch_flags = JSON_LOG;
+}
+
+static void setup_logging_once(void) {
+ static pthread_once_t once = PTHREAD_ONCE_INIT;
+ assert_se(pthread_once(&once, setup_logging) == 0);
+}
+
+#define NSS_ENTRYPOINT_BEGIN \
+ BLOCK_SIGNALS(NSS_SIGNALS_BLOCK); \
+ setup_logging_once()
+
+NSS_GETHOSTBYNAME_PROTOTYPES(resolve);
+NSS_GETHOSTBYADDR_PROTOTYPES(resolve);
+
+static bool error_shall_fallback(const char *error_id) {
+ /* The Varlink errors where we shall signal "please fallback" back to the NSS stack, so that some
+ * fallback module can be loaded. (These are mostly all Varlink-internal errors, as apparently we
+ * then were unable to even do IPC with systemd-resolved.) */
+ return STR_IN_SET(error_id,
+ VARLINK_ERROR_DISCONNECTED,
+ VARLINK_ERROR_TIMEOUT,
+ VARLINK_ERROR_PROTOCOL,
+ VARLINK_ERROR_INTERFACE_NOT_FOUND,
+ VARLINK_ERROR_METHOD_NOT_FOUND,
+ VARLINK_ERROR_METHOD_NOT_IMPLEMENTED);
+}
+
+static bool error_shall_try_again(const char *error_id) {
+ /* The Varlink errors where we shall signal "can't answer now but might be able to later" back to the
+ * NSS stack. These are all errors that indicate lack of configuration or network problems. */
+ return STR_IN_SET(error_id,
+ "io.systemd.Resolve.NoNameServers",
+ "io.systemd.Resolve.QueryTimedOut",
+ "io.systemd.Resolve.MaxAttemptsReached",
+ "io.systemd.Resolve.NetworkDown");
+}
+
+static int connect_to_resolved(Varlink **ret) {
+ _cleanup_(varlink_unrefp) Varlink *link = NULL;
+ int r;
+
+ r = varlink_connect_address(&link, "/run/systemd/resolve/io.systemd.Resolve");
+ if (r < 0)
+ return r;
+
+ r = varlink_set_relative_timeout(link, SD_RESOLVED_QUERY_TIMEOUT_USEC);
+ if (r < 0)
+ return r;
+
+ *ret = TAKE_PTR(link);
+ return 0;
+}
+
+static uint32_t ifindex_to_scopeid(int family, const void *a, int ifindex) {
+ struct in6_addr in6;
+
+ if (family != AF_INET6 || ifindex == 0)
+ return 0;
+
+ /* Some apps can't deal with the scope ID attached to non-link-local addresses. Hence, let's suppress that. */
+
+ assert(sizeof(in6) == FAMILY_ADDRESS_SIZE(AF_INET6));
+ memcpy(&in6, a, sizeof(struct in6_addr));
+
+ return in6_addr_is_link_local(&in6) ? ifindex : 0;
+}
+
+static int json_dispatch_ifindex(const char *name, JsonVariant *variant, JsonDispatchFlags flags, void *userdata) {
+ int *ifi = ASSERT_PTR(userdata);
+ int64_t t;
+
+ assert(variant);
+
+ if (!json_variant_is_integer(variant))
+ return json_log(variant, flags, SYNTHETIC_ERRNO(EINVAL), "JSON field '%s' is not an integer.", strna(name));
+
+ t = json_variant_integer(variant);
+ if (t > INT_MAX)
+ return json_log(variant, flags, SYNTHETIC_ERRNO(EINVAL), "JSON field '%s' is out of bounds for an interface index.", strna(name));
+
+ *ifi = (int) t;
+ return 0;
+}
+
+static int json_dispatch_family(const char *name, JsonVariant *variant, JsonDispatchFlags flags, void *userdata) {
+ int *family = ASSERT_PTR(userdata);
+ int64_t t;
+
+ assert(variant);
+
+ if (!json_variant_is_integer(variant))
+ return json_log(variant, flags, SYNTHETIC_ERRNO(EINVAL), "JSON field '%s' is not an integer.", strna(name));
+
+ t = json_variant_integer(variant);
+ if (t < 0 || t > INT_MAX)
+ return json_log(variant, flags, SYNTHETIC_ERRNO(EINVAL), "JSON field '%s' is not a valid family.", strna(name));
+
+ *family = (int) t;
+ return 0;
+}
+
+typedef struct ResolveHostnameReply {
+ JsonVariant *addresses;
+ char *name;
+ uint64_t flags;
+} ResolveHostnameReply;
+
+static void resolve_hostname_reply_destroy(ResolveHostnameReply *p) {
+ assert(p);
+
+ json_variant_unref(p->addresses);
+ free(p->name);
+}
+
+static const JsonDispatch resolve_hostname_reply_dispatch_table[] = {
+ { "addresses", JSON_VARIANT_ARRAY, json_dispatch_variant, offsetof(ResolveHostnameReply, addresses), JSON_MANDATORY },
+ { "name", JSON_VARIANT_STRING, json_dispatch_string, offsetof(ResolveHostnameReply, name), 0 },
+ { "flags", _JSON_VARIANT_TYPE_INVALID, json_dispatch_uint64, offsetof(ResolveHostnameReply, flags), 0 },
+ {}
+};
+
+typedef struct AddressParameters {
+ int ifindex;
+ int family;
+ union in_addr_union address;
+ size_t address_size;
+} AddressParameters;
+
+static int json_dispatch_address(const char *name, JsonVariant *variant, JsonDispatchFlags flags, void *userdata) {
+ AddressParameters *p = ASSERT_PTR(userdata);
+ union in_addr_union buf = {};
+ JsonVariant *i;
+ size_t n, k = 0;
+
+ assert(variant);
+
+ if (!json_variant_is_array(variant))
+ return json_log(variant, flags, SYNTHETIC_ERRNO(EINVAL), "JSON field '%s' is not an array.", strna(name));
+
+ n = json_variant_elements(variant);
+ if (!IN_SET(n, 4, 16))
+ return json_log(variant, flags, SYNTHETIC_ERRNO(EINVAL), "JSON field '%s' is array of unexpected size.", strna(name));
+
+ JSON_VARIANT_ARRAY_FOREACH(i, variant) {
+ int64_t b;
+
+ if (!json_variant_is_integer(i))
+ return json_log(variant, flags, SYNTHETIC_ERRNO(EINVAL), "Element %zu of JSON field '%s' is not an integer.", k, strna(name));
+
+ b = json_variant_integer(i);
+ if (b < 0 || b > 0xff)
+ return json_log(variant, flags, SYNTHETIC_ERRNO(EINVAL),
+ "Element %zu of JSON field '%s' is out of range 0%s255.",
+ k, strna(name), special_glyph(SPECIAL_GLYPH_ELLIPSIS));
+
+ buf.bytes[k++] = (uint8_t) b;
+ }
+
+ p->address = buf;
+ p->address_size = k;
+
+ return 0;
+}
+
+static const JsonDispatch address_parameters_dispatch_table[] = {
+ { "ifindex", JSON_VARIANT_INTEGER, json_dispatch_ifindex, offsetof(AddressParameters, ifindex), 0 },
+ { "family", JSON_VARIANT_INTEGER, json_dispatch_family, offsetof(AddressParameters, family), JSON_MANDATORY },
+ { "address", JSON_VARIANT_ARRAY, json_dispatch_address, 0, JSON_MANDATORY },
+ {}
+};
+
+static uint64_t query_flag(
+ const char *name,
+ const int value,
+ uint64_t flag) {
+ int r;
+
+ r = getenv_bool_secure(name);
+ if (r >= 0)
+ return r == value ? flag : 0;
+ if (r != -ENXIO)
+ log_debug_errno(r, "Failed to parse $%s, ignoring.", name);
+ return 0;
+}
+
+static uint64_t query_flags(void) {
+ /* Allow callers to turn off validation, synthetization, caching, etc., when we resolve via
+ * nss-resolve. */
+ return query_flag("SYSTEMD_NSS_RESOLVE_VALIDATE", 0, SD_RESOLVED_NO_VALIDATE) |
+ query_flag("SYSTEMD_NSS_RESOLVE_SYNTHESIZE", 0, SD_RESOLVED_NO_SYNTHESIZE) |
+ query_flag("SYSTEMD_NSS_RESOLVE_CACHE", 0, SD_RESOLVED_NO_CACHE) |
+ query_flag("SYSTEMD_NSS_RESOLVE_ZONE", 0, SD_RESOLVED_NO_ZONE) |
+ query_flag("SYSTEMD_NSS_RESOLVE_TRUST_ANCHOR", 0, SD_RESOLVED_NO_TRUST_ANCHOR) |
+ query_flag("SYSTEMD_NSS_RESOLVE_NETWORK", 0, SD_RESOLVED_NO_NETWORK);
+}
+
+enum nss_status _nss_resolve_gethostbyname4_r(
+ const char *name,
+ struct gaih_addrtuple **pat,
+ char *buffer, size_t buflen,
+ int *errnop, int *h_errnop,
+ int32_t *ttlp) {
+
+ _cleanup_(varlink_unrefp) Varlink *link = NULL;
+ _cleanup_(json_variant_unrefp) JsonVariant *cparams = NULL;
+ _cleanup_(resolve_hostname_reply_destroy) ResolveHostnameReply p = {};
+ JsonVariant *rparams, *entry;
+ int r;
+
+ PROTECT_ERRNO;
+ NSS_ENTRYPOINT_BEGIN;
+
+ assert(name);
+ assert(pat);
+ assert(buffer);
+ assert(errnop);
+ assert(h_errnop);
+
+ r = connect_to_resolved(&link);
+ if (r < 0)
+ goto fail;
+
+ r = json_build(&cparams, JSON_BUILD_OBJECT(
+ JSON_BUILD_PAIR("name", JSON_BUILD_STRING(name)),
+ JSON_BUILD_PAIR("flags", JSON_BUILD_UNSIGNED(query_flags()))));
+ if (r < 0)
+ goto fail;
+
+ /* Return NSS_STATUS_UNAVAIL when communication with systemd-resolved fails, allowing falling
+ * back to other nss modules. Treat all other error conditions as NOTFOUND. This includes
+ * DNSSEC errors and suchlike. (We don't use UNAVAIL in this case so that the nsswitch.conf
+ * configuration can distinguish such executed but negative replies from complete failure to
+ * talk to resolved). */
+ const char *error_id;
+ r = varlink_call(link, "io.systemd.Resolve.ResolveHostname", cparams, &rparams, &error_id, NULL);
+ if (r < 0)
+ goto fail;
+ if (!isempty(error_id)) {
+ if (error_shall_try_again(error_id))
+ goto try_again;
+ if (error_shall_fallback(error_id))
+ goto fail;
+ if (streq(error_id, "io.systemd.Resolve.NoSuchResourceRecord"))
+ goto no_data;
+ goto not_found;
+ }
+
+ r = json_dispatch(rparams, resolve_hostname_reply_dispatch_table, json_dispatch_flags, &p);
+ if (r < 0)
+ goto fail;
+ if (json_variant_is_blank_object(p.addresses))
+ goto not_found;
+
+ size_t n_addresses = 0;
+ JSON_VARIANT_ARRAY_FOREACH(entry, p.addresses) {
+ AddressParameters q = {};
+
+ r = json_dispatch(entry, address_parameters_dispatch_table, json_dispatch_flags, &q);
+ if (r < 0)
+ goto fail;
+
+ if (!IN_SET(q.family, AF_INET, AF_INET6))
+ continue;
+
+ if (q.address_size != FAMILY_ADDRESS_SIZE(q.family)) {
+ r = -EINVAL;
+ goto fail;
+ }
+
+ n_addresses++;
+ }
+
+ const char *canonical = p.name ?: name;
+ size_t l = strlen(canonical);
+ size_t idx, ms = ALIGN(l+1) + ALIGN(sizeof(struct gaih_addrtuple)) * n_addresses;
+
+ if (buflen < ms) {
+ UNPROTECT_ERRNO;
+ *errnop = ERANGE;
+ *h_errnop = NETDB_INTERNAL;
+ return NSS_STATUS_TRYAGAIN;
+ }
+
+ /* First, append name */
+ char *r_name = buffer;
+ memcpy(r_name, canonical, l + 1);
+ idx = ALIGN(l + 1);
+
+ /* Second, append addresses */
+ struct gaih_addrtuple *r_tuple = NULL,
+ *r_tuple_first = (struct gaih_addrtuple*) (buffer + idx);
+
+ JSON_VARIANT_ARRAY_FOREACH(entry, p.addresses) {
+ AddressParameters q = {};
+
+ r = json_dispatch(entry, address_parameters_dispatch_table, json_dispatch_flags, &q);
+ if (r < 0)
+ goto fail;
+
+ if (!IN_SET(q.family, AF_INET, AF_INET6))
+ continue;
+
+ r_tuple = (struct gaih_addrtuple*) (buffer + idx);
+ r_tuple->next = (struct gaih_addrtuple*) ((char*) r_tuple + ALIGN(sizeof(struct gaih_addrtuple)));
+ r_tuple->name = r_name;
+ r_tuple->family = q.family;
+ r_tuple->scopeid = ifindex_to_scopeid(q.family, &q.address, q.ifindex);
+ memcpy(r_tuple->addr, &q.address, q.address_size);
+
+ idx += ALIGN(sizeof(struct gaih_addrtuple));
+ }
+
+ assert(r_tuple); /* We had at least one address, so r_tuple must be set */
+ r_tuple->next = NULL; /* Override last next pointer */
+
+ assert(idx == ms);
+
+ if (*pat)
+ **pat = *r_tuple_first;
+ else
+ *pat = r_tuple_first;
+
+ if (ttlp)
+ *ttlp = 0;
+
+ /* Explicitly reset both *h_errnop and h_errno to work around
+ * https://bugzilla.redhat.com/show_bug.cgi?id=1125975 */
+ *h_errnop = NETDB_SUCCESS;
+ h_errno = 0;
+
+ return NSS_STATUS_SUCCESS;
+
+fail:
+ UNPROTECT_ERRNO;
+ *errnop = -r;
+ *h_errnop = NO_RECOVERY;
+ return NSS_STATUS_UNAVAIL;
+
+not_found:
+ *h_errnop = HOST_NOT_FOUND;
+ return NSS_STATUS_NOTFOUND;
+
+no_data:
+ *h_errnop = NO_DATA;
+ return NSS_STATUS_NOTFOUND;
+
+try_again:
+ UNPROTECT_ERRNO;
+ *errnop = -r;
+ *h_errnop = TRY_AGAIN;
+ return NSS_STATUS_TRYAGAIN;
+}
+
+enum nss_status _nss_resolve_gethostbyname3_r(
+ const char *name,
+ int af,
+ struct hostent *result,
+ char *buffer, size_t buflen,
+ int *errnop, int *h_errnop,
+ int32_t *ttlp,
+ char **canonp) {
+
+ _cleanup_(varlink_unrefp) Varlink *link = NULL;
+ _cleanup_(json_variant_unrefp) JsonVariant *cparams = NULL;
+ _cleanup_(resolve_hostname_reply_destroy) ResolveHostnameReply p = {};
+ JsonVariant *rparams, *entry;
+ int r;
+
+ PROTECT_ERRNO;
+ NSS_ENTRYPOINT_BEGIN;
+
+ assert(name);
+ assert(result);
+ assert(buffer);
+ assert(errnop);
+ assert(h_errnop);
+
+ if (af == AF_UNSPEC)
+ af = AF_INET;
+
+ if (!IN_SET(af, AF_INET, AF_INET6)) {
+ r = -EAFNOSUPPORT;
+ goto fail;
+ }
+
+ r = connect_to_resolved(&link);
+ if (r < 0)
+ goto fail;
+
+ r = json_build(&cparams, JSON_BUILD_OBJECT(JSON_BUILD_PAIR("name", JSON_BUILD_STRING(name)),
+ JSON_BUILD_PAIR("family", JSON_BUILD_INTEGER(af)),
+ JSON_BUILD_PAIR("flags", JSON_BUILD_UNSIGNED(query_flags()))));
+ if (r < 0)
+ goto fail;
+
+ const char *error_id;
+ r = varlink_call(link, "io.systemd.Resolve.ResolveHostname", cparams, &rparams, &error_id, NULL);
+ if (r < 0)
+ goto fail;
+ if (!isempty(error_id)) {
+ if (error_shall_try_again(error_id))
+ goto try_again;
+ if (error_shall_fallback(error_id))
+ goto fail;
+ if (streq(error_id, "io.systemd.Resolve.NoSuchResourceRecord"))
+ goto no_data;
+ goto not_found;
+ }
+
+ r = json_dispatch(rparams, resolve_hostname_reply_dispatch_table, json_dispatch_flags, &p);
+ if (r < 0)
+ goto fail;
+ if (json_variant_is_blank_object(p.addresses))
+ goto not_found;
+
+ size_t n_addresses = 0;
+ JSON_VARIANT_ARRAY_FOREACH(entry, p.addresses) {
+ AddressParameters q = {};
+
+ r = json_dispatch(entry, address_parameters_dispatch_table, json_dispatch_flags, &q);
+ if (r < 0)
+ goto fail;
+
+ if (!IN_SET(q.family, AF_INET, AF_INET6))
+ continue;
+
+ if (q.address_size != FAMILY_ADDRESS_SIZE(q.family)) {
+ r = -EINVAL;
+ goto fail;
+ }
+
+ n_addresses++;
+ }
+
+ const char *canonical = p.name ?: name;
+
+ size_t alen = FAMILY_ADDRESS_SIZE(af);
+ size_t l = strlen(canonical);
+
+ size_t idx, ms = ALIGN(l + 1) + n_addresses * ALIGN(alen) + (n_addresses + 2) * sizeof(char*);
+
+ if (buflen < ms) {
+ UNPROTECT_ERRNO;
+ *errnop = ERANGE;
+ *h_errnop = NETDB_INTERNAL;
+ return NSS_STATUS_TRYAGAIN;
+ }
+
+ /* First, append name */
+ char *r_name = buffer;
+ memcpy(r_name, canonical, l+1);
+ idx = ALIGN(l+1);
+
+ /* Second, create empty aliases array */
+ char *r_aliases = buffer + idx;
+ ((char**) r_aliases)[0] = NULL;
+ idx += sizeof(char*);
+
+ /* Third, append addresses */
+ char *r_addr = buffer + idx;
+
+ size_t i = 0;
+ JSON_VARIANT_ARRAY_FOREACH(entry, p.addresses) {
+ AddressParameters q = {};
+
+ r = json_dispatch(entry, address_parameters_dispatch_table, json_dispatch_flags, &q);
+ if (r < 0)
+ goto fail;
+
+ if (q.family != af)
+ continue;
+
+ if (q.address_size != alen) {
+ r = -EINVAL;
+ goto fail;
+ }
+
+ memcpy(r_addr + i*ALIGN(alen), &q.address, alen);
+ i++;
+ }
+
+ assert(i == n_addresses);
+ idx += n_addresses * ALIGN(alen);
+
+ /* Fourth, append address pointer array */
+ char *r_addr_list = buffer + idx;
+ for (i = 0; i < n_addresses; i++)
+ ((char**) r_addr_list)[i] = r_addr + i*ALIGN(alen);
+
+ ((char**) r_addr_list)[i] = NULL;
+ idx += (n_addresses + 1) * sizeof(char*);
+
+ assert(idx == ms);
+
+ result->h_name = r_name;
+ result->h_aliases = (char**) r_aliases;
+ result->h_addrtype = af;
+ result->h_length = alen;
+ result->h_addr_list = (char**) r_addr_list;
+
+ if (ttlp)
+ *ttlp = 0;
+
+ if (canonp)
+ *canonp = r_name;
+
+ /* Explicitly reset both *h_errnop and h_errno to work around
+ * https://bugzilla.redhat.com/show_bug.cgi?id=1125975 */
+ *h_errnop = NETDB_SUCCESS;
+ h_errno = 0;
+
+ return NSS_STATUS_SUCCESS;
+
+fail:
+ UNPROTECT_ERRNO;
+ *errnop = -r;
+ *h_errnop = NO_RECOVERY;
+ return NSS_STATUS_UNAVAIL;
+
+not_found:
+ *h_errnop = HOST_NOT_FOUND;
+ return NSS_STATUS_NOTFOUND;
+
+no_data:
+ *h_errnop = NO_DATA;
+ return NSS_STATUS_NOTFOUND;
+
+try_again:
+ UNPROTECT_ERRNO;
+ *errnop = -r;
+ *h_errnop = TRY_AGAIN;
+ return NSS_STATUS_TRYAGAIN;
+}
+
+typedef struct ResolveAddressReply {
+ JsonVariant *names;
+ uint64_t flags;
+} ResolveAddressReply;
+
+static void resolve_address_reply_destroy(ResolveAddressReply *p) {
+ assert(p);
+
+ json_variant_unref(p->names);
+}
+
+static const JsonDispatch resolve_address_reply_dispatch_table[] = {
+ { "names", JSON_VARIANT_ARRAY, json_dispatch_variant, offsetof(ResolveAddressReply, names), JSON_MANDATORY },
+ { "flags", _JSON_VARIANT_TYPE_INVALID, json_dispatch_uint64, offsetof(ResolveAddressReply, flags), 0 },
+ {}
+};
+
+typedef struct NameParameters {
+ int ifindex;
+ char *name;
+} NameParameters;
+
+static void name_parameters_destroy(NameParameters *p) {
+ assert(p);
+
+ free(p->name);
+}
+
+static const JsonDispatch name_parameters_dispatch_table[] = {
+ { "ifindex", JSON_VARIANT_INTEGER, json_dispatch_ifindex, offsetof(NameParameters, ifindex), 0 },
+ { "name", JSON_VARIANT_STRING, json_dispatch_string, offsetof(NameParameters, name), JSON_MANDATORY },
+ {}
+};
+
+enum nss_status _nss_resolve_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) {
+
+ _cleanup_(varlink_unrefp) Varlink *link = NULL;
+ _cleanup_(json_variant_unrefp) JsonVariant *cparams = NULL;
+ _cleanup_(resolve_address_reply_destroy) ResolveAddressReply p = {};
+ JsonVariant *rparams, *entry;
+ int r;
+
+ PROTECT_ERRNO;
+ NSS_ENTRYPOINT_BEGIN;
+
+ assert(addr);
+ assert(result);
+ assert(buffer);
+ assert(errnop);
+ assert(h_errnop);
+
+ if (!IN_SET(af, AF_INET, AF_INET6)) {
+ UNPROTECT_ERRNO;
+ *errnop = EAFNOSUPPORT;
+ *h_errnop = NO_DATA;
+ return NSS_STATUS_UNAVAIL;
+ }
+
+ if (len != FAMILY_ADDRESS_SIZE(af)) {
+ r = -EINVAL;
+ goto fail;
+ }
+
+ r = connect_to_resolved(&link);
+ if (r < 0)
+ goto fail;
+
+ r = json_build(&cparams, JSON_BUILD_OBJECT(JSON_BUILD_PAIR("address", JSON_BUILD_BYTE_ARRAY(addr, len)),
+ JSON_BUILD_PAIR("family", JSON_BUILD_INTEGER(af)),
+ JSON_BUILD_PAIR("flags", JSON_BUILD_UNSIGNED(query_flags()))));
+ if (r < 0)
+ goto fail;
+
+ const char* error_id;
+ r = varlink_call(link, "io.systemd.Resolve.ResolveAddress", cparams, &rparams, &error_id, NULL);
+ if (r < 0)
+ goto fail;
+ if (!isempty(error_id)) {
+ if (error_shall_try_again(error_id))
+ goto try_again;
+ if (error_shall_fallback(error_id))
+ goto fail;
+ goto not_found;
+ }
+
+ r = json_dispatch(rparams, resolve_address_reply_dispatch_table, json_dispatch_flags, &p);
+ if (r < 0)
+ goto fail;
+ if (json_variant_is_blank_object(p.names))
+ goto not_found;
+
+ size_t ms = 0, idx;
+
+ JSON_VARIANT_ARRAY_FOREACH(entry, p.names) {
+ _cleanup_(name_parameters_destroy) NameParameters q = {};
+
+ r = json_dispatch(entry, name_parameters_dispatch_table, json_dispatch_flags, &q);
+ if (r < 0)
+ goto fail;
+
+ ms += ALIGN(strlen(q.name) + 1);
+ }
+
+ size_t n_names = json_variant_elements(p.names);
+ ms += ALIGN(len) + /* the address */
+ 2 * sizeof(char*) + /* pointer to the address, plus trailing NULL */
+ n_names * sizeof(char*); /* pointers to aliases, plus trailing NULL */
+
+ if (buflen < ms) {
+ UNPROTECT_ERRNO;
+ *errnop = ERANGE;
+ *h_errnop = NETDB_INTERNAL;
+ return NSS_STATUS_TRYAGAIN;
+ }
+
+ /* First, place address */
+ char *r_addr = buffer;
+ memcpy(r_addr, addr, len);
+ idx = ALIGN(len);
+
+ /* Second, place address list */
+ char *r_addr_list = buffer + idx;
+ ((char**) r_addr_list)[0] = r_addr;
+ ((char**) r_addr_list)[1] = NULL;
+ idx += sizeof(char*) * 2;
+
+ /* Third, reserve space for the aliases array, plus trailing NULL */
+ char *r_aliases = buffer + idx;
+ idx += sizeof(char*) * n_names;
+
+ /* Fourth, place aliases */
+ char *r_name = buffer + idx;
+
+ size_t i = 0;
+ JSON_VARIANT_ARRAY_FOREACH(entry, p.names) {
+ _cleanup_(name_parameters_destroy) NameParameters q = {};
+
+ r = json_dispatch(entry, name_parameters_dispatch_table, json_dispatch_flags, &q);
+ if (r < 0)
+ goto fail;
+
+ size_t l = strlen(q.name);
+ char *z = buffer + idx;
+ memcpy(z, q.name, l + 1);
+
+ if (i > 0)
+ ((char**) r_aliases)[i - 1] = z;
+ i++;
+
+ idx += ALIGN(l + 1);
+ }
+ ((char**) r_aliases)[n_names - 1] = NULL;
+
+ assert(idx == ms);
+
+ result->h_name = r_name;
+ result->h_aliases = (char**) r_aliases;
+ result->h_addrtype = af;
+ result->h_length = len;
+ result->h_addr_list = (char**) r_addr_list;
+
+ if (ttlp)
+ *ttlp = 0;
+
+ /* Explicitly reset both *h_errnop and h_errno to work around
+ * https://bugzilla.redhat.com/show_bug.cgi?id=1125975 */
+ *h_errnop = NETDB_SUCCESS;
+ h_errno = 0;
+
+ return NSS_STATUS_SUCCESS;
+
+fail:
+ UNPROTECT_ERRNO;
+ *errnop = -r;
+ *h_errnop = NO_RECOVERY;
+ return NSS_STATUS_UNAVAIL;
+
+not_found:
+ *h_errnop = HOST_NOT_FOUND;
+ return NSS_STATUS_NOTFOUND;
+
+try_again:
+ UNPROTECT_ERRNO;
+ *errnop = -r;
+ *h_errnop = TRY_AGAIN;
+ return NSS_STATUS_TRYAGAIN;
+}
+
+NSS_GETHOSTBYNAME_FALLBACKS(resolve);
+NSS_GETHOSTBYADDR_FALLBACKS(resolve);
diff --git a/src/nss-resolve/nss-resolve.sym b/src/nss-resolve/nss-resolve.sym
new file mode 100644
index 0000000..ecc958e
--- /dev/null
+++ b/src/nss-resolve/nss-resolve.sym
@@ -0,0 +1,19 @@
+/***
+ SPDX-License-Identifier: LGPL-2.1-or-later
+
+ 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.
+***/
+
+{
+global:
+ _nss_resolve_gethostbyname_r;
+ _nss_resolve_gethostbyname2_r;
+ _nss_resolve_gethostbyname3_r;
+ _nss_resolve_gethostbyname4_r;
+ _nss_resolve_gethostbyaddr_r;
+ _nss_resolve_gethostbyaddr2_r;
+local: *;
+};