src/nss-resolve/nss-resolve.c

   1 /* SPDX-License-Identifier: LGPL-2.1-or-later */
   2
   3 #include <errno.h>
   4 #include <netdb.h>
   5 #include <nss.h>
   6 #include <pthread.h>
   7 #include <stdlib.h>
   8 #include <sys/types.h>
   9 #include <unistd.h>
  10
  11 #include "env-util.h"
  12 #include "errno-util.h"
  13 #include "glyph-util.h"
  14 #include "in-addr-util.h"
  15 #include "macro.h"
  16 #include "nss-util.h"
  17 #include "resolved-def.h"
  18 #include "signal-util.h"
  19 #include "string-util.h"
  20 #include "strv.h"
  21 #include "varlink.h"
  22
  23 static JsonDispatchFlags json_dispatch_flags = JSON_ALLOW_EXTENSIONS;
  24
  25 static void setup_logging(void) {
  26         log_parse_environment_variables();
  27
  28         if (DEBUG_LOGGING)
  29                 json_dispatch_flags = JSON_LOG;
  30 }
  31
  32 static void setup_logging_once(void) {
  33         static pthread_once_t once = PTHREAD_ONCE_INIT;
  34         assert_se(pthread_once(&once, setup_logging) == 0);
  35 }
  36
  37 #define NSS_ENTRYPOINT_BEGIN                    \
  38         BLOCK_SIGNALS(NSS_SIGNALS_BLOCK);       \
  39         setup_logging_once()
  40
  41 NSS_GETHOSTBYNAME_PROTOTYPES(resolve);
  42 NSS_GETHOSTBYADDR_PROTOTYPES(resolve);
  43
  44 static bool error_shall_fallback(const char *error_id) {
  45         /* The Varlink errors where we shall signal "please fallback" back to the NSS stack, so that some
  46          * fallback module can be loaded. (These are mostly all Varlink-internal errors, as apparently we
  47          * then were unable to even do IPC with systemd-resolved.) */
  48         return STR_IN_SET(error_id,
  49                           VARLINK_ERROR_DISCONNECTED,
  50                           VARLINK_ERROR_TIMEOUT,
  51                           VARLINK_ERROR_PROTOCOL,
  52                           VARLINK_ERROR_INTERFACE_NOT_FOUND,
  53                           VARLINK_ERROR_METHOD_NOT_FOUND,
  54                           VARLINK_ERROR_METHOD_NOT_IMPLEMENTED);
  55 }
  56
  57 static bool error_shall_try_again(const char *error_id) {
  58         /* The Varlink errors where we shall signal "can't answer now but might be able to later" back to the
  59          * NSS stack. These are all errors that indicate lack of configuration or network problems. */
  60         return STR_IN_SET(error_id,
  61                           "io.systemd.Resolve.NoNameServers",
  62                           "io.systemd.Resolve.QueryTimedOut",
  63                           "io.systemd.Resolve.MaxAttemptsReached",
  64                           "io.systemd.Resolve.NetworkDown");
  65 }
  66
  67 static int connect_to_resolved(Varlink **ret) {
  68         _cleanup_(varlink_unrefp) Varlink *link = NULL;
  69         int r;
  70
  71         r = varlink_connect_address(&link, "/run/systemd/resolve/io.systemd.Resolve");
  72         if (r < 0)
  73                 return r;
  74
  75         r = varlink_set_relative_timeout(link, SD_RESOLVED_QUERY_TIMEOUT_USEC);
  76         if (r < 0)
  77                 return r;
  78
  79         *ret = TAKE_PTR(link);
  80         return 0;
  81 }
  82
  83 static uint32_t ifindex_to_scopeid(int family, const void *a, int ifindex) {
  84         struct in6_addr in6;
  85
  86         if (family != AF_INET6 || ifindex == 0)
  87                 return 0;
  88
  89         /* Some apps can't deal with the scope ID attached to non-link-local addresses. Hence, let's suppress that. */
  90
  91         assert(sizeof(in6) == FAMILY_ADDRESS_SIZE(AF_INET6));
  92         memcpy(&in6, a, sizeof(struct in6_addr));
  93
  94         return in6_addr_is_link_local(&in6) ? ifindex : 0;
  95 }
  96
  97 static int json_dispatch_ifindex(const char *name, JsonVariant *variant, JsonDispatchFlags flags, void *userdata) {
  98         int *ifi = ASSERT_PTR(userdata);
  99         int64_t t;
 100
 101         assert(variant);
 102
 103         if (!json_variant_is_integer(variant))
 104                 return json_log(variant, flags, SYNTHETIC_ERRNO(EINVAL), "JSON field '%s' is not an integer.", strna(name));
 105
 106         t = json_variant_integer(variant);
 107         if (t > INT_MAX)
 108                 return json_log(variant, flags, SYNTHETIC_ERRNO(EINVAL), "JSON field '%s' is out of bounds for an interface index.", strna(name));
 109
 110         *ifi = (int) t;
 111         return 0;
 112 }
 113
 114 static int json_dispatch_family(const char *name, JsonVariant *variant, JsonDispatchFlags flags, void *userdata) {
 115         int *family = ASSERT_PTR(userdata);
 116         int64_t t;
 117
 118         assert(variant);
 119
 120         if (!json_variant_is_integer(variant))
 121                 return json_log(variant, flags, SYNTHETIC_ERRNO(EINVAL), "JSON field '%s' is not an integer.", strna(name));
 122
 123         t = json_variant_integer(variant);
 124         if (t < 0 || t > INT_MAX)
 125                 return json_log(variant, flags, SYNTHETIC_ERRNO(EINVAL), "JSON field '%s' is not a valid family.", strna(name));
 126
 127         *family = (int) t;
 128         return 0;
 129 }
 130
 131 typedef struct ResolveHostnameReply {
 132         JsonVariant *addresses;
 133         char *name;
 134         uint64_t flags;
 135 } ResolveHostnameReply;
 136
 137 static void resolve_hostname_reply_destroy(ResolveHostnameReply *p) {
 138         assert(p);
 139
 140         json_variant_unref(p->addresses);
 141         free(p->name);
 142 }
 143
 144 static const JsonDispatch resolve_hostname_reply_dispatch_table[] = {
 145         { "addresses", JSON_VARIANT_ARRAY,         json_dispatch_variant, offsetof(ResolveHostnameReply, addresses), JSON_MANDATORY },
 146         { "name",      JSON_VARIANT_STRING,        json_dispatch_string,  offsetof(ResolveHostnameReply, name),      0              },
 147         { "flags",     _JSON_VARIANT_TYPE_INVALID, json_dispatch_uint64,  offsetof(ResolveHostnameReply, flags),     0              },
 148         {}
 149 };
 150
 151 typedef struct AddressParameters {
 152         int ifindex;
 153         int family;
 154         union in_addr_union address;
 155         size_t address_size;
 156 } AddressParameters;
 157
 158 static int json_dispatch_address(const char *name, JsonVariant *variant, JsonDispatchFlags flags, void *userdata) {
 159         AddressParameters *p = ASSERT_PTR(userdata);
 160         union in_addr_union buf = {};
 161         JsonVariant *i;
 162         size_t n, k = 0;
 163
 164         assert(variant);
 165
 166         if (!json_variant_is_array(variant))
 167                 return json_log(variant, flags, SYNTHETIC_ERRNO(EINVAL), "JSON field '%s' is not an array.", strna(name));
 168
 169         n = json_variant_elements(variant);
 170         if (!IN_SET(n, 4, 16))
 171                 return json_log(variant, flags, SYNTHETIC_ERRNO(EINVAL), "JSON field '%s' is array of unexpected size.", strna(name));
 172
 173         JSON_VARIANT_ARRAY_FOREACH(i, variant) {
 174                 int64_t b;
 175
 176                 if (!json_variant_is_integer(i))
 177                         return json_log(variant, flags, SYNTHETIC_ERRNO(EINVAL), "Element %zu of JSON field '%s' is not an integer.", k, strna(name));
 178
 179                 b = json_variant_integer(i);
 180                 if (b < 0 || b > 0xff)
 181                         return json_log(variant, flags, SYNTHETIC_ERRNO(EINVAL),
 182                                         "Element %zu of JSON field '%s' is out of range 0%s255.",
 183                                         k, strna(name), special_glyph(SPECIAL_GLYPH_ELLIPSIS));
 184
 185                 buf.bytes[k++] = (uint8_t) b;
 186         }
 187
 188         p->address = buf;
 189         p->address_size = k;
 190
 191         return 0;
 192 }
 193
 194 static const JsonDispatch address_parameters_dispatch_table[] = {
 195         { "ifindex", JSON_VARIANT_INTEGER,  json_dispatch_ifindex, offsetof(AddressParameters, ifindex), 0              },
 196         { "family",  JSON_VARIANT_INTEGER,  json_dispatch_family,  offsetof(AddressParameters, family),  JSON_MANDATORY },
 197         { "address", JSON_VARIANT_ARRAY,    json_dispatch_address, 0,                                    JSON_MANDATORY },
 198         {}
 199 };
 200
 201 static uint64_t query_flag(
 202                 const char *name,
 203                 const int value,
 204                 uint64_t flag) {
 205
 206         int r;
 207
 208         r = secure_getenv_bool(name);
 209         if (r >= 0)
 210                 return r == value ? flag : 0;
 211         if (r != -ENXIO)
 212                 log_debug_errno(r, "Failed to parse $%s, ignoring.", name);
 213         return 0;
 214 }
 215
 216 static uint64_t query_flags(void) {
 217         /* Allow callers to turn off validation, synthetization, caching, etc., when we resolve via
 218          * nss-resolve. */
 219         return  query_flag("SYSTEMD_NSS_RESOLVE_VALIDATE", 0, SD_RESOLVED_NO_VALIDATE) |
 220                 query_flag("SYSTEMD_NSS_RESOLVE_SYNTHESIZE", 0, SD_RESOLVED_NO_SYNTHESIZE) |
 221                 query_flag("SYSTEMD_NSS_RESOLVE_CACHE", 0, SD_RESOLVED_NO_CACHE) |
 222                 query_flag("SYSTEMD_NSS_RESOLVE_ZONE", 0, SD_RESOLVED_NO_ZONE) |
 223                 query_flag("SYSTEMD_NSS_RESOLVE_TRUST_ANCHOR", 0, SD_RESOLVED_NO_TRUST_ANCHOR) |
 224                 query_flag("SYSTEMD_NSS_RESOLVE_NETWORK", 0, SD_RESOLVED_NO_NETWORK);
 225 }
 226
 227 enum nss_status _nss_resolve_gethostbyname4_r(
 228                 const char *name,
 229                 struct gaih_addrtuple **pat,
 230                 char *buffer, size_t buflen,
 231                 int *errnop, int *h_errnop,
 232                 int32_t *ttlp) {
 233
 234         _cleanup_(varlink_unrefp) Varlink *link = NULL;
 235         _cleanup_(json_variant_unrefp) JsonVariant *cparams = NULL;
 236         _cleanup_(resolve_hostname_reply_destroy) ResolveHostnameReply p = {};
 237         JsonVariant *rparams, *entry;
 238         int r;
 239
 240         PROTECT_ERRNO;
 241         NSS_ENTRYPOINT_BEGIN;
 242
 243         assert(name);
 244         assert(pat);
 245         assert(buffer);
 246         assert(errnop);
 247         assert(h_errnop);
 248
 249         r = connect_to_resolved(&link);
 250         if (r < 0)
 251                 goto fail;
 252
 253         r = json_build(&cparams, JSON_BUILD_OBJECT(
 254                                        JSON_BUILD_PAIR("name", JSON_BUILD_STRING(name)),
 255                                        JSON_BUILD_PAIR("flags", JSON_BUILD_UNSIGNED(query_flags()))));
 256         if (r < 0)
 257                 goto fail;
 258
 259         /* Return NSS_STATUS_UNAVAIL when communication with systemd-resolved fails, allowing falling
 260          * back to other nss modules. Treat all other error conditions as NOTFOUND. This includes
 261          * DNSSEC errors and suchlike. (We don't use UNAVAIL in this case so that the nsswitch.conf
 262          * configuration can distinguish such executed but negative replies from complete failure to
 263          * talk to resolved). */
 264         const char *error_id;
 265         r = varlink_call(link, "io.systemd.Resolve.ResolveHostname", cparams, &rparams, &error_id);
 266         if (r < 0)
 267                 goto fail;
 268         if (!isempty(error_id)) {
 269                 if (error_shall_try_again(error_id))
 270                         goto try_again;
 271                 if (error_shall_fallback(error_id))
 272                         goto fail;
 273                 if (streq(error_id, "io.systemd.Resolve.NoSuchResourceRecord"))
 274                         goto no_data;
 275                 goto not_found;
 276         }
 277
 278         r = json_dispatch(rparams, resolve_hostname_reply_dispatch_table, json_dispatch_flags, &p);
 279         if (r < 0)
 280                 goto fail;
 281         if (json_variant_is_blank_object(p.addresses))
 282                 goto not_found;
 283
 284         size_t n_addresses = 0;
 285         JSON_VARIANT_ARRAY_FOREACH(entry, p.addresses) {
 286                 AddressParameters q = {};
 287
 288                 r = json_dispatch(entry, address_parameters_dispatch_table, json_dispatch_flags, &q);
 289                 if (r < 0)
 290                         goto fail;
 291
 292                 if (!IN_SET(q.family, AF_INET, AF_INET6))
 293                         continue;
 294
 295                 if (q.address_size != FAMILY_ADDRESS_SIZE(q.family)) {
 296                         r = -EINVAL;
 297                         goto fail;
 298                 }
 299
 300                 n_addresses++;
 301         }
 302
 303         const char *canonical = p.name ?: name;
 304         size_t l = strlen(canonical);
 305         size_t idx, ms = ALIGN(l+1) + ALIGN(sizeof(struct gaih_addrtuple)) * n_addresses;
 306
 307         if (buflen < ms) {
 308                 UNPROTECT_ERRNO;
 309                 *errnop = ERANGE;
 310                 *h_errnop = NETDB_INTERNAL;
 311                 return NSS_STATUS_TRYAGAIN;
 312         }
 313
 314         /* First, append name */
 315         char *r_name = buffer;
 316         memcpy(r_name, canonical, l + 1);
 317         idx = ALIGN(l + 1);
 318
 319         /* Second, append addresses */
 320         struct gaih_addrtuple *r_tuple = NULL,
 321                 *r_tuple_first = (struct gaih_addrtuple*) (buffer + idx);
 322
 323         JSON_VARIANT_ARRAY_FOREACH(entry, p.addresses) {
 324                 AddressParameters q = {};
 325
 326                 r = json_dispatch(entry, address_parameters_dispatch_table, json_dispatch_flags, &q);
 327                 if (r < 0)
 328                         goto fail;
 329
 330                 if (!IN_SET(q.family, AF_INET, AF_INET6))
 331                         continue;
 332
 333                 r_tuple = (struct gaih_addrtuple*) (buffer + idx);
 334                 r_tuple->next = (struct gaih_addrtuple*) ((char*) r_tuple + ALIGN(sizeof(struct gaih_addrtuple)));
 335                 r_tuple->name = r_name;
 336                 r_tuple->family = q.family;
 337                 r_tuple->scopeid = ifindex_to_scopeid(q.family, &q.address, q.ifindex);
 338                 memcpy(r_tuple->addr, &q.address, q.address_size);
 339
 340                 idx += ALIGN(sizeof(struct gaih_addrtuple));
 341         }
 342
 343         assert(r_tuple);  /* We had at least one address, so r_tuple must be set */
 344         r_tuple->next = NULL;  /* Override last next pointer */
 345
 346         assert(idx == ms);
 347
 348         if (*pat)
 349                 **pat = *r_tuple_first;
 350         else
 351                 *pat = r_tuple_first;
 352
 353         if (ttlp)
 354                 *ttlp = 0;
 355
 356         /* Explicitly reset both *h_errnop and h_errno to work around
 357          * https://bugzilla.redhat.com/show_bug.cgi?id=1125975 */
 358         *h_errnop = NETDB_SUCCESS;
 359         h_errno = 0;
 360
 361         return NSS_STATUS_SUCCESS;
 362
 363 fail:
 364         UNPROTECT_ERRNO;
 365         *errnop = -r;
 366         *h_errnop = NO_RECOVERY;
 367         return NSS_STATUS_UNAVAIL;
 368
 369 not_found:
 370         *h_errnop = HOST_NOT_FOUND;
 371         return NSS_STATUS_NOTFOUND;
 372
 373 no_data:
 374         *h_errnop = NO_DATA;
 375         return NSS_STATUS_NOTFOUND;
 376
 377 try_again:
 378         UNPROTECT_ERRNO;
 379         *errnop = -r;
 380         *h_errnop = TRY_AGAIN;
 381         return NSS_STATUS_TRYAGAIN;
 382 }
 383
 384 enum nss_status _nss_resolve_gethostbyname3_r(
 385                 const char *name,
 386                 int af,
 387                 struct hostent *result,
 388                 char *buffer, size_t buflen,
 389                 int *errnop, int *h_errnop,
 390                 int32_t *ttlp,
 391                 char **canonp) {
 392
 393         _cleanup_(varlink_unrefp) Varlink *link = NULL;
 394         _cleanup_(json_variant_unrefp) JsonVariant *cparams = NULL;
 395         _cleanup_(resolve_hostname_reply_destroy) ResolveHostnameReply p = {};
 396         JsonVariant *rparams, *entry;
 397         int r;
 398
 399         PROTECT_ERRNO;
 400         NSS_ENTRYPOINT_BEGIN;
 401
 402         assert(name);
 403         assert(result);
 404         assert(buffer);
 405         assert(errnop);
 406         assert(h_errnop);
 407
 408         if (af == AF_UNSPEC)
 409                 af = AF_INET;
 410
 411         if (!IN_SET(af, AF_INET, AF_INET6)) {
 412                 r = -EAFNOSUPPORT;
 413                 goto fail;
 414         }
 415
 416         r = connect_to_resolved(&link);
 417         if (r < 0)
 418                 goto fail;
 419
 420         r = json_build(&cparams, JSON_BUILD_OBJECT(JSON_BUILD_PAIR("name", JSON_BUILD_STRING(name)),
 421                                                    JSON_BUILD_PAIR("family", JSON_BUILD_INTEGER(af)),
 422                                                    JSON_BUILD_PAIR("flags", JSON_BUILD_UNSIGNED(query_flags()))));
 423         if (r < 0)
 424                 goto fail;
 425
 426         const char *error_id;
 427         r = varlink_call(link, "io.systemd.Resolve.ResolveHostname", cparams, &rparams, &error_id);
 428         if (r < 0)
 429                 goto fail;
 430         if (!isempty(error_id)) {
 431                 if (error_shall_try_again(error_id))
 432                         goto try_again;
 433                 if (error_shall_fallback(error_id))
 434                         goto fail;
 435                 if (streq(error_id, "io.systemd.Resolve.NoSuchResourceRecord"))
 436                         goto no_data;
 437                 goto not_found;
 438         }
 439
 440         r = json_dispatch(rparams, resolve_hostname_reply_dispatch_table, json_dispatch_flags, &p);
 441         if (r < 0)
 442                 goto fail;
 443         if (json_variant_is_blank_object(p.addresses))
 444                 goto not_found;
 445
 446         size_t n_addresses = 0;
 447         JSON_VARIANT_ARRAY_FOREACH(entry, p.addresses) {
 448                 AddressParameters q = {};
 449
 450                 r = json_dispatch(entry, address_parameters_dispatch_table, json_dispatch_flags, &q);
 451                 if (r < 0)
 452                         goto fail;
 453
 454                 if (!IN_SET(q.family, AF_INET, AF_INET6))
 455                         continue;
 456
 457                 if (q.address_size != FAMILY_ADDRESS_SIZE(q.family)) {
 458                         r = -EINVAL;
 459                         goto fail;
 460                 }
 461
 462                 n_addresses++;
 463         }
 464
 465         const char *canonical = p.name ?: name;
 466
 467         size_t alen = FAMILY_ADDRESS_SIZE(af);
 468         size_t l = strlen(canonical);
 469
 470         size_t idx, ms = ALIGN(l + 1) + n_addresses * ALIGN(alen) + (n_addresses + 2) * sizeof(char*);
 471
 472         if (buflen < ms) {
 473                 UNPROTECT_ERRNO;
 474                 *errnop = ERANGE;
 475                 *h_errnop = NETDB_INTERNAL;
 476                 return NSS_STATUS_TRYAGAIN;
 477         }
 478
 479         /* First, append name */
 480         char *r_name = buffer;
 481         memcpy(r_name, canonical, l+1);
 482         idx = ALIGN(l+1);
 483
 484         /* Second, create empty aliases array */
 485         char *r_aliases = buffer + idx;
 486         ((char**) r_aliases)[0] = NULL;
 487         idx += sizeof(char*);
 488
 489         /* Third, append addresses */
 490         char *r_addr = buffer + idx;
 491
 492         size_t i = 0;
 493         JSON_VARIANT_ARRAY_FOREACH(entry, p.addresses) {
 494                 AddressParameters q = {};
 495
 496                 r = json_dispatch(entry, address_parameters_dispatch_table, json_dispatch_flags, &q);
 497                 if (r < 0)
 498                         goto fail;
 499
 500                 if (q.family != af)
 501                         continue;
 502
 503                 if (q.address_size != alen) {
 504                         r = -EINVAL;
 505                         goto fail;
 506                 }
 507
 508                 memcpy(r_addr + i*ALIGN(alen), &q.address, alen);
 509                 i++;
 510         }
 511
 512         assert(i == n_addresses);
 513         idx += n_addresses * ALIGN(alen);
 514
 515         /* Fourth, append address pointer array */
 516         char *r_addr_list = buffer + idx;
 517         for (i = 0; i < n_addresses; i++)
 518                 ((char**) r_addr_list)[i] = r_addr + i*ALIGN(alen);
 519
 520         ((char**) r_addr_list)[i] = NULL;
 521         idx += (n_addresses + 1) * sizeof(char*);
 522
 523         assert(idx == ms);
 524
 525         result->h_name = r_name;
 526         result->h_aliases = (char**) r_aliases;
 527         result->h_addrtype = af;
 528         result->h_length = alen;
 529         result->h_addr_list = (char**) r_addr_list;
 530
 531         if (ttlp)
 532                 *ttlp = 0;
 533
 534         if (canonp)
 535                 *canonp = r_name;
 536
 537         /* Explicitly reset both *h_errnop and h_errno to work around
 538          * https://bugzilla.redhat.com/show_bug.cgi?id=1125975 */
 539         *h_errnop = NETDB_SUCCESS;
 540         h_errno = 0;
 541
 542         return NSS_STATUS_SUCCESS;
 543
 544 fail:
 545         UNPROTECT_ERRNO;
 546         *errnop = -r;
 547         *h_errnop = NO_RECOVERY;
 548         return NSS_STATUS_UNAVAIL;
 549
 550 not_found:
 551         *h_errnop = HOST_NOT_FOUND;
 552         return NSS_STATUS_NOTFOUND;
 553
 554 no_data:
 555         *h_errnop = NO_DATA;
 556         return NSS_STATUS_NOTFOUND;
 557
 558 try_again:
 559         UNPROTECT_ERRNO;
 560         *errnop = -r;
 561         *h_errnop = TRY_AGAIN;
 562         return NSS_STATUS_TRYAGAIN;
 563 }
 564
 565 typedef struct ResolveAddressReply {
 566         JsonVariant *names;
 567         uint64_t flags;
 568 } ResolveAddressReply;
 569
 570 static void resolve_address_reply_destroy(ResolveAddressReply *p) {
 571         assert(p);
 572
 573         json_variant_unref(p->names);
 574 }
 575
 576 static const JsonDispatch resolve_address_reply_dispatch_table[] = {
 577         { "names", JSON_VARIANT_ARRAY,         json_dispatch_variant, offsetof(ResolveAddressReply, names), JSON_MANDATORY },
 578         { "flags", _JSON_VARIANT_TYPE_INVALID, json_dispatch_uint64,  offsetof(ResolveAddressReply, flags), 0              },
 579         {}
 580 };
 581
 582 typedef struct NameParameters {
 583         int ifindex;
 584         char *name;
 585 } NameParameters;
 586
 587 static void name_parameters_destroy(NameParameters *p) {
 588         assert(p);
 589
 590         free(p->name);
 591 }
 592
 593 static const JsonDispatch name_parameters_dispatch_table[] = {
 594         { "ifindex", JSON_VARIANT_INTEGER, json_dispatch_ifindex, offsetof(NameParameters, ifindex), 0              },
 595         { "name",    JSON_VARIANT_STRING,  json_dispatch_string,  offsetof(NameParameters, name),    JSON_MANDATORY },
 596         {}
 597 };
 598
 599 enum nss_status _nss_resolve_gethostbyaddr2_r(
 600                 const void* addr, socklen_t len,
 601                 int af,
 602                 struct hostent *result,
 603                 char *buffer, size_t buflen,
 604                 int *errnop, int *h_errnop,
 605                 int32_t *ttlp) {
 606
 607         _cleanup_(varlink_unrefp) Varlink *link = NULL;
 608         _cleanup_(json_variant_unrefp) JsonVariant *cparams = NULL;
 609         _cleanup_(resolve_address_reply_destroy) ResolveAddressReply p = {};
 610         JsonVariant *rparams, *entry;
 611         int r;
 612
 613         PROTECT_ERRNO;
 614         NSS_ENTRYPOINT_BEGIN;
 615
 616         assert(addr);
 617         assert(result);
 618         assert(buffer);
 619         assert(errnop);
 620         assert(h_errnop);
 621
 622         if (!IN_SET(af, AF_INET, AF_INET6)) {
 623                 UNPROTECT_ERRNO;
 624                 *errnop = EAFNOSUPPORT;
 625                 *h_errnop = NO_DATA;
 626                 return NSS_STATUS_UNAVAIL;
 627         }
 628
 629         if (len != FAMILY_ADDRESS_SIZE(af)) {
 630                 r = -EINVAL;
 631                 goto fail;
 632         }
 633
 634         r = connect_to_resolved(&link);
 635         if (r < 0)
 636                 goto fail;
 637
 638         r = json_build(&cparams, JSON_BUILD_OBJECT(JSON_BUILD_PAIR("address", JSON_BUILD_BYTE_ARRAY(addr, len)),
 639                                                    JSON_BUILD_PAIR("family", JSON_BUILD_INTEGER(af)),
 640                                                    JSON_BUILD_PAIR("flags", JSON_BUILD_UNSIGNED(query_flags()))));
 641         if (r < 0)
 642                 goto fail;
 643
 644         const char* error_id;
 645         r = varlink_call(link, "io.systemd.Resolve.ResolveAddress", cparams, &rparams, &error_id);
 646         if (r < 0)
 647                 goto fail;
 648         if (!isempty(error_id)) {
 649                 if (error_shall_try_again(error_id))
 650                         goto try_again;
 651                 if (error_shall_fallback(error_id))
 652                         goto fail;
 653                 goto not_found;
 654         }
 655
 656         r = json_dispatch(rparams, resolve_address_reply_dispatch_table, json_dispatch_flags, &p);
 657         if (r < 0)
 658                 goto fail;
 659         if (json_variant_is_blank_object(p.names))
 660                 goto not_found;
 661
 662         size_t ms = 0, idx;
 663
 664         JSON_VARIANT_ARRAY_FOREACH(entry, p.names) {
 665                 _cleanup_(name_parameters_destroy) NameParameters q = {};
 666
 667                 r = json_dispatch(entry, name_parameters_dispatch_table, json_dispatch_flags, &q);
 668                 if (r < 0)
 669                         goto fail;
 670
 671                 ms += ALIGN(strlen(q.name) + 1);
 672         }
 673
 674         size_t n_names = json_variant_elements(p.names);
 675         ms += ALIGN(len) +                    /* the address */
 676               2 * sizeof(char*) +             /* pointer to the address, plus trailing NULL */
 677               n_names * sizeof(char*);        /* pointers to aliases, plus trailing NULL */
 678
 679         if (buflen < ms) {
 680                 UNPROTECT_ERRNO;
 681                 *errnop = ERANGE;
 682                 *h_errnop = NETDB_INTERNAL;
 683                 return NSS_STATUS_TRYAGAIN;
 684         }
 685
 686         /* First, place address */
 687         char *r_addr = buffer;
 688         memcpy(r_addr, addr, len);
 689         idx = ALIGN(len);
 690
 691         /* Second, place address list */
 692         char *r_addr_list = buffer + idx;
 693         ((char**) r_addr_list)[0] = r_addr;
 694         ((char**) r_addr_list)[1] = NULL;
 695         idx += sizeof(char*) * 2;
 696
 697         /* Third, reserve space for the aliases array, plus trailing NULL */
 698         char *r_aliases = buffer + idx;
 699         idx += sizeof(char*) * n_names;
 700
 701         /* Fourth, place aliases */
 702         char *r_name = buffer + idx;
 703
 704         size_t i = 0;
 705         JSON_VARIANT_ARRAY_FOREACH(entry, p.names) {
 706                 _cleanup_(name_parameters_destroy) NameParameters q = {};
 707
 708                 r = json_dispatch(entry, name_parameters_dispatch_table, json_dispatch_flags, &q);
 709                 if (r < 0)
 710                         goto fail;
 711
 712                 size_t l = strlen(q.name);
 713                 char *z = buffer + idx;
 714                 memcpy(z, q.name, l + 1);
 715
 716                 if (i > 0)
 717                         ((char**) r_aliases)[i - 1] = z;
 718                 i++;
 719
 720                 idx += ALIGN(l + 1);
 721         }
 722         ((char**) r_aliases)[n_names - 1] = NULL;
 723
 724         assert(idx == ms);
 725
 726         result->h_name = r_name;
 727         result->h_aliases = (char**) r_aliases;
 728         result->h_addrtype = af;
 729         result->h_length = len;
 730         result->h_addr_list = (char**) r_addr_list;
 731
 732         if (ttlp)
 733                 *ttlp = 0;
 734
 735         /* Explicitly reset both *h_errnop and h_errno to work around
 736          * https://bugzilla.redhat.com/show_bug.cgi?id=1125975 */
 737         *h_errnop = NETDB_SUCCESS;
 738         h_errno = 0;
 739
 740         return NSS_STATUS_SUCCESS;
 741
 742 fail:
 743         UNPROTECT_ERRNO;
 744         *errnop = -r;
 745         *h_errnop = NO_RECOVERY;
 746         return NSS_STATUS_UNAVAIL;
 747
 748 not_found:
 749         *h_errnop = HOST_NOT_FOUND;
 750         return NSS_STATUS_NOTFOUND;
 751
 752 try_again:
 753         UNPROTECT_ERRNO;
 754         *errnop = -r;
 755         *h_errnop = TRY_AGAIN;
 756         return NSS_STATUS_TRYAGAIN;
 757 }
 758
 759 NSS_GETHOSTBYNAME_FALLBACKS(resolve);
 760 NSS_GETHOSTBYADDR_FALLBACKS(resolve);