src/shared/unit-file.c

   1 /* SPDX-License-Identifier: LGPL-2.1+ */
   2
   3 #include "sd-id128.h"
   4
   5 #include "dirent-util.h"
   6 #include "fd-util.h"
   7 #include "fs-util.h"
   8 #include "macro.h"
   9 #include "path-lookup.h"
  10 #include "set.h"
  11 #include "special.h"
  12 #include "stat-util.h"
  13 #include "string-util.h"
  14 #include "strv.h"
  15 #include "unit-file.h"
  16
  17 bool unit_type_may_alias(UnitType type) {
  18         return IN_SET(type,
  19                       UNIT_SERVICE,
  20                       UNIT_SOCKET,
  21                       UNIT_TARGET,
  22                       UNIT_DEVICE,
  23                       UNIT_TIMER,
  24                       UNIT_PATH);
  25 }
  26
  27 bool unit_type_may_template(UnitType type) {
  28         return IN_SET(type,
  29                       UNIT_SERVICE,
  30                       UNIT_SOCKET,
  31                       UNIT_TARGET,
  32                       UNIT_TIMER,
  33                       UNIT_PATH);
  34 }
  35
  36 int unit_symlink_name_compatible(const char *symlink, const char *target, bool instance_propagation) {
  37         _cleanup_free_ char *template = NULL;
  38         int r, un_type1, un_type2;
  39
  40         un_type1 = unit_name_classify(symlink);
  41
  42         /* The straightforward case: the symlink name matches the target and we have a valid unit */
  43         if (streq(symlink, target) &&
  44             (un_type1 & (UNIT_NAME_PLAIN | UNIT_NAME_INSTANCE)))
  45                 return 1;
  46
  47         r = unit_name_template(symlink, &template);
  48         if (r == -EINVAL)
  49                 return 0; /* Not a template */
  50         if (r < 0)
  51                 return r;
  52
  53         un_type2 = unit_name_classify(target);
  54
  55         /* An instance name points to a target that is just the template name */
  56         if (un_type1 == UNIT_NAME_INSTANCE &&
  57             un_type2 == UNIT_NAME_TEMPLATE &&
  58             streq(template, target))
  59                 return 1;
  60
  61         /* foo@.target.requires/bar@.service: instance will be propagated */
  62         if (instance_propagation &&
  63             un_type1 == UNIT_NAME_TEMPLATE &&
  64             un_type2 == UNIT_NAME_TEMPLATE &&
  65             streq(template, target))
  66                 return 1;
  67
  68         return 0;
  69 }
  70
  71 int unit_validate_alias_symlink_and_warn(const char *filename, const char *target) {
  72         const char *src, *dst;
  73         _cleanup_free_ char *src_instance = NULL, *dst_instance = NULL;
  74         UnitType src_unit_type, dst_unit_type;
  75         int src_name_type, dst_name_type;
  76
  77         /* Check if the *alias* symlink is valid. This applies to symlinks like
  78          * /etc/systemd/system/dbus.service → dbus-broker.service, but not to .wants or .requires symlinks
  79          * and such. Neither does this apply to symlinks which *link* units, i.e. symlinks to outside of the
  80          * unit lookup path.
  81          *
  82          * -EINVAL is returned if the something is wrong with the source filename or the source unit type is
  83          *         not allowed to symlink,
  84          * -EXDEV if the target filename is not a valid unit name or doesn't match the source.
  85          */
  86
  87         src = basename(filename);
  88         dst = basename(target);
  89
  90         /* src checks */
  91
  92         src_name_type = unit_name_to_instance(src, &src_instance);
  93         if (src_name_type < 0)
  94                 return log_notice_errno(src_name_type,
  95                                         "%s: not a valid unit name \"%s\": %m", filename, src);
  96
  97         src_unit_type = unit_name_to_type(src);
  98         assert(src_unit_type >= 0); /* unit_name_to_instance() checked the suffix already */
  99
 100         if (!unit_type_may_alias(src_unit_type))
 101                 return log_notice_errno(SYNTHETIC_ERRNO(EINVAL),
 102                                         "%s: symlinks are not allowed for units of this type, rejecting.",
 103                                         filename);
 104
 105         if (src_name_type != UNIT_NAME_PLAIN &&
 106             !unit_type_may_template(src_unit_type))
 107                 return log_notice_errno(SYNTHETIC_ERRNO(EINVAL),
 108                                         "%s: templates not allowed for %s units, rejecting.",
 109                                         filename, unit_type_to_string(src_unit_type));
 110
 111         /* dst checks */
 112
 113         dst_name_type = unit_name_to_instance(dst, &dst_instance);
 114         if (dst_name_type < 0)
 115                 return log_notice_errno(dst_name_type == -EINVAL ? SYNTHETIC_ERRNO(EXDEV) : dst_name_type,
 116                                         "%s points to \"%s\" which is not a valid unit name: %m",
 117                                         filename, dst);
 118
 119         if (!(dst_name_type == src_name_type ||
 120               (src_name_type == UNIT_NAME_INSTANCE && dst_name_type == UNIT_NAME_TEMPLATE)))
 121                 return log_notice_errno(SYNTHETIC_ERRNO(EXDEV),
 122                                         "%s: symlink target name type \"%s\" does not match source, rejecting.",
 123                                         filename, dst);
 124
 125         if (dst_name_type == UNIT_NAME_INSTANCE) {
 126                 assert(src_instance);
 127                 assert(dst_instance);
 128                 if (!streq(src_instance, dst_instance))
 129                         return log_notice_errno(SYNTHETIC_ERRNO(EXDEV),
 130                                                 "%s: unit symlink target \"%s\" instance name doesn't match, rejecting.",
 131                                                 filename, dst);
 132         }
 133
 134         dst_unit_type = unit_name_to_type(dst);
 135         if (dst_unit_type != src_unit_type)
 136                 return log_notice_errno(SYNTHETIC_ERRNO(EXDEV),
 137                                         "%s: symlink target \"%s\" has incompatible suffix, rejecting.",
 138                                         filename, dst);
 139
 140         return 0;
 141 }
 142
 143 #define FOLLOW_MAX 8
 144
 145 static int unit_ids_map_get(
 146                 Hashmap *unit_ids_map,
 147                 const char *unit_name,
 148                 const char **ret_fragment_path) {
 149
 150         /* Resolve recursively until we hit an absolute path, i.e. a non-aliased unit.
 151          *
 152          * We distinguish the case where unit_name was not found in the hashmap at all, and the case where
 153          * some symlink was broken.
 154          *
 155          * If a symlink target points to an instance name, then we also check for the template. */
 156
 157         const char *id = NULL;
 158         int r;
 159
 160         for (unsigned n = 0; n < FOLLOW_MAX; n++) {
 161                 const char *t = hashmap_get(unit_ids_map, id ?: unit_name);
 162                 if (!t) {
 163                         _cleanup_free_ char *template = NULL;
 164
 165                         if (!id)
 166                                 return -ENOENT;
 167
 168                         r = unit_name_template(id, &template);
 169                         if (r == -EINVAL)
 170                                 return -ENXIO; /* we failed to find the symlink target */
 171                         if (r < 0)
 172                                 return log_error_errno(r, "Failed to determine template name for %s: %m", id);
 173
 174                         t = hashmap_get(unit_ids_map, template);
 175                         if (!t)
 176                                 return -ENXIO;
 177
 178                         /* We successfully switched from instanced name to a template, let's continue */
 179                 }
 180
 181                 if (path_is_absolute(t)) {
 182                         if (ret_fragment_path)
 183                                 *ret_fragment_path = t;
 184                         return 0;
 185                 }
 186
 187                 id = t;
 188         }
 189
 190         return -ELOOP;
 191 }
 192
 193 static bool lookup_paths_mtime_exclude(const LookupPaths *lp, const char *path) {
 194         /* Paths that are under our exclusive control. Users shall not alter those directly. */
 195
 196         return streq_ptr(path, lp->generator) ||
 197                streq_ptr(path, lp->generator_early) ||
 198                streq_ptr(path, lp->generator_late) ||
 199                streq_ptr(path, lp->transient) ||
 200                streq_ptr(path, lp->persistent_control) ||
 201                streq_ptr(path, lp->runtime_control);
 202 }
 203
 204 #define HASH_KEY SD_ID128_MAKE(4e,86,1b,e3,39,b3,40,46,98,5d,b8,11,34,8f,c3,c1)
 205
 206 bool lookup_paths_timestamp_hash_same(const LookupPaths *lp, uint64_t timestamp_hash, uint64_t *ret_new) {
 207         struct siphash state;
 208
 209         siphash24_init(&state, HASH_KEY.bytes);
 210
 211         char **dir;
 212         STRV_FOREACH(dir, (char**) lp->search_path) {
 213                 struct stat st;
 214
 215                 if (lookup_paths_mtime_exclude(lp, *dir))
 216                         continue;
 217
 218                 /* Determine the latest lookup path modification time */
 219                 if (stat(*dir, &st) < 0) {
 220                         if (errno == ENOENT)
 221                                 continue;
 222
 223                         log_debug_errno(errno, "Failed to stat %s, ignoring: %m", *dir);
 224                         continue;
 225                 }
 226
 227                 siphash24_compress_usec_t(timespec_load(&st.st_mtim), &state);
 228         }
 229
 230         uint64_t updated = siphash24_finalize(&state);
 231         if (ret_new)
 232                 *ret_new = updated;
 233         if (updated != timestamp_hash)
 234                 log_debug("Modification times have changed, need to update cache.");
 235         return updated == timestamp_hash;
 236 }
 237
 238 int unit_file_build_name_map(
 239                 const LookupPaths *lp,
 240                 uint64_t *cache_timestamp_hash,
 241                 Hashmap **unit_ids_map,
 242                 Hashmap **unit_names_map,
 243                 Set **path_cache) {
 244
 245         /* Build two mappings: any name → main unit (i.e. the end result of symlink resolution), unit name →
 246          * all aliases (i.e. the entry for a given key is a a list of all names which point to this key). The
 247          * key is included in the value iff we saw a file or symlink with that name. In other words, if we
 248          * have a key, but it is not present in the value for itself, there was an alias pointing to it, but
 249          * the unit itself is not loadable.
 250          *
 251          * At the same, build a cache of paths where to find units. The non-const parameters are for input
 252          * and output. Existing contents will be freed before the new contents are stored.
 253          */
 254
 255         _cleanup_hashmap_free_ Hashmap *ids = NULL, *names = NULL;
 256         _cleanup_set_free_free_ Set *paths = NULL;
 257         uint64_t timestamp_hash;
 258         char **dir;
 259         int r;
 260
 261         /* Before doing anything, check if the timestamp hash that was passed is still valid.
 262          * If yes, do nothing. */
 263         if (cache_timestamp_hash &&
 264             lookup_paths_timestamp_hash_same(lp, *cache_timestamp_hash, &timestamp_hash))
 265                         return 0;
 266
 267         /* The timestamp hash is now set based on the mtimes from before when we start reading files.
 268          * If anything is modified concurrently, we'll consider the cache outdated. */
 269
 270         if (path_cache) {
 271                 paths = set_new(&path_hash_ops_free);
 272                 if (!paths)
 273                         return log_oom();
 274         }
 275
 276         STRV_FOREACH(dir, (char**) lp->search_path) {
 277                 struct dirent *de;
 278                 _cleanup_closedir_ DIR *d = NULL;
 279
 280                 d = opendir(*dir);
 281                 if (!d) {
 282                         if (errno != ENOENT)
 283                                 log_warning_errno(errno, "Failed to open \"%s\", ignoring: %m", *dir);
 284                         continue;
 285                 }
 286
 287                 FOREACH_DIRENT_ALL(de, d, log_warning_errno(errno, "Failed to read \"%s\", ignoring: %m", *dir)) {
 288                         char *filename;
 289                         _cleanup_free_ char *_filename_free = NULL, *simplified = NULL;
 290                         const char *suffix, *dst = NULL;
 291                         bool valid_unit_name;
 292
 293                         valid_unit_name = unit_name_is_valid(de->d_name, UNIT_NAME_ANY);
 294
 295                         /* We only care about valid units and dirs with certain suffixes, let's ignore the
 296                          * rest. */
 297                         if (!valid_unit_name &&
 298                             !ENDSWITH_SET(de->d_name, ".wants", ".requires", ".d"))
 299                                 continue;
 300
 301                         filename = path_join(*dir, de->d_name);
 302                         if (!filename)
 303                                 return log_oom();
 304
 305                         if (paths) {
 306                                 r = set_consume(paths, filename);
 307                                 if (r < 0)
 308                                         return log_oom();
 309                                 /* We will still use filename below. This is safe because we know the set
 310                                  * holds a reference. */
 311                         } else
 312                                 _filename_free = filename; /* Make sure we free the filename. */
 313
 314                         if (!valid_unit_name)
 315                                 continue;
 316                         assert_se(suffix = strrchr(de->d_name, '.'));
 317
 318                         /* search_path is ordered by priority (highest first). If the name is already mapped
 319                          * to something (incl. itself), it means that we have already seen it, and we should
 320                          * ignore it here. */
 321                         if (hashmap_contains(ids, de->d_name))
 322                                 continue;
 323
 324                         dirent_ensure_type(d, de);
 325                         if (de->d_type == DT_LNK) {
 326                                 /* We don't explicitly check for alias loops here. unit_ids_map_get() which
 327                                  * limits the number of hops should be used to access the map. */
 328
 329                                 _cleanup_free_ char *target = NULL;
 330
 331                                 r = readlinkat_malloc(dirfd(d), de->d_name, &target);
 332                                 if (r < 0) {
 333                                         log_warning_errno(r, "Failed to read symlink %s/%s, ignoring: %m",
 334                                                           *dir, de->d_name);
 335                                         continue;
 336                                 }
 337
 338                                 const bool is_abs = path_is_absolute(target);
 339                                 if (lp->root_dir || !is_abs) {
 340                                         char *target_abs = path_join(is_abs ? lp->root_dir : *dir, target);
 341                                         if (!target_abs)
 342                                                 return log_oom();
 343
 344                                         free_and_replace(target, target_abs);
 345                                 }
 346
 347                                 /* Get rid of "." and ".." components in target path */
 348                                 r = chase_symlinks(target, lp->root_dir, CHASE_NOFOLLOW | CHASE_NONEXISTENT, &simplified, NULL);
 349                                 if (r < 0) {
 350                                         log_warning_errno(r, "Failed to resolve symlink %s pointing to %s, ignoring: %m",
 351                                                           filename, target);
 352                                         continue;
 353                                 }
 354
 355                                 /* Check if the symlink goes outside of our search path.
 356                                  * If yes, it's a linked unit file or mask, and we don't care about the target name.
 357                                  * Let's just store the link destination directly.
 358                                  * If not, let's verify that it's a good symlink. */
 359                                 char *tail = path_startswith_strv(simplified, lp->search_path);
 360                                 if (tail) {
 361                                         bool self_alias;
 362
 363                                         dst = basename(simplified);
 364                                         self_alias = streq(dst, de->d_name);
 365
 366                                         if (is_path(tail))
 367                                                 log_full(self_alias ? LOG_DEBUG : LOG_WARNING,
 368                                                          "Suspicious symlink %s→%s, treating as alias.",
 369                                                          filename, simplified);
 370
 371                                         r = unit_validate_alias_symlink_and_warn(filename, simplified);
 372                                         if (r < 0)
 373                                                 continue;
 374
 375                                         if (self_alias) {
 376                                                 /* A self-alias that has no effect */
 377                                                 log_debug("%s: self-alias: %s/%s → %s, ignoring.",
 378                                                           __func__, *dir, de->d_name, dst);
 379                                                 continue;
 380                                         }
 381
 382                                         log_debug("%s: alias: %s/%s → %s", __func__, *dir, de->d_name, dst);
 383                                 } else {
 384                                         dst  = simplified;
 385
 386                                         log_debug("%s: linked unit file: %s/%s → %s", __func__, *dir, de->d_name, dst);
 387                                 }
 388
 389                         } else {
 390                                 dst = filename;
 391                                 log_debug("%s: normal unit file: %s", __func__, dst);
 392                         }
 393
 394                         r = hashmap_put_strdup(&ids, de->d_name, dst);
 395                         if (r < 0)
 396                                 return log_warning_errno(r, "Failed to add entry to hashmap (%s→%s): %m",
 397                                                          de->d_name, dst);
 398                 }
 399         }
 400
 401         /* Let's also put the names in the reverse db. */
 402         const char *dummy, *src;
 403         HASHMAP_FOREACH_KEY(dummy, src, ids) {
 404                 const char *dst;
 405
 406                 r = unit_ids_map_get(ids, src, &dst);
 407                 if (r < 0)
 408                         continue;
 409
 410                 if (null_or_empty_path(dst) != 0)
 411                         continue;
 412
 413                 /* Do not treat instance symlinks that point to the template as aliases */
 414                 if (unit_name_is_valid(basename(dst), UNIT_NAME_TEMPLATE) &&
 415                     unit_name_is_valid(src, UNIT_NAME_INSTANCE))
 416                         continue;
 417
 418                 r = string_strv_hashmap_put(&names, basename(dst), src);
 419                 if (r < 0)
 420                         return log_warning_errno(r, "Failed to add entry to hashmap (%s→%s): %m",
 421                                                  basename(dst), src);
 422         }
 423
 424         if (cache_timestamp_hash)
 425                 *cache_timestamp_hash = timestamp_hash;
 426
 427         hashmap_free_and_replace(*unit_ids_map, ids);
 428         hashmap_free_and_replace(*unit_names_map, names);
 429         if (path_cache)
 430                 set_free_and_replace(*path_cache, paths);
 431
 432         return 1;
 433 }
 434
 435 int unit_file_find_fragment(
 436                 Hashmap *unit_ids_map,
 437                 Hashmap *unit_name_map,
 438                 const char *unit_name,
 439                 const char **ret_fragment_path,
 440                 Set **ret_names) {
 441
 442         const char *fragment = NULL;
 443         _cleanup_free_ char *template = NULL, *instance = NULL;
 444         _cleanup_set_free_free_ Set *names = NULL;
 445         char **t, **nnn;
 446         int r, name_type;
 447
 448         /* Finds a fragment path, and returns the set of names:
 449          * if we have …/foo.service and …/foo-alias.service→foo.service,
 450          * and …/foo@.service and …/foo-alias@.service→foo@.service,
 451          * and …/foo@inst.service,
 452          * this should return:
 453          * foo.service → …/foo.service, {foo.service, foo-alias.service},
 454          * foo-alias.service → …/foo.service, {foo.service, foo-alias.service},
 455          * foo@.service → …/foo@.service, {foo@.service, foo-alias@.service},
 456          * foo-alias@.service → …/foo@.service, {foo@.service, foo-alias@.service},
 457          * foo@bar.service → …/foo@.service, {foo@bar.service, foo-alias@bar.service},
 458          * foo-alias@bar.service → …/foo@.service, {foo@bar.service, foo-alias@bar.service},
 459          * foo-alias@inst.service → …/foo@inst.service, {foo@inst.service, foo-alias@inst.service}.
 460          */
 461
 462         name_type = unit_name_to_instance(unit_name, &instance);
 463         if (name_type < 0)
 464                 return name_type;
 465
 466         names = set_new(&string_hash_ops);
 467         if (!names)
 468                 return -ENOMEM;
 469
 470         /* The unit always has its own name if it's not a template. */
 471         if (IN_SET(name_type, UNIT_NAME_PLAIN, UNIT_NAME_INSTANCE)) {
 472                 r = set_put_strdup(&names, unit_name);
 473                 if (r < 0)
 474                         return r;
 475         }
 476
 477         /* First try to load fragment under the original name */
 478         r = unit_ids_map_get(unit_ids_map, unit_name, &fragment);
 479         if (r < 0 && !IN_SET(r, -ENOENT, -ENXIO))
 480                 return log_debug_errno(r, "Cannot load unit %s: %m", unit_name);
 481
 482         if (fragment) {
 483                 /* Add any aliases of the original name to the set of names */
 484                 nnn = hashmap_get(unit_name_map, basename(fragment));
 485                 STRV_FOREACH(t, nnn) {
 486                         if (name_type == UNIT_NAME_INSTANCE && unit_name_is_valid(*t, UNIT_NAME_TEMPLATE)) {
 487                                 char *inst;
 488
 489                                 r = unit_name_replace_instance(*t, instance, &inst);
 490                                 if (r < 0)
 491                                         return log_debug_errno(r, "Cannot build instance name %s+%s: %m", *t, instance);
 492
 493                                 if (!streq(unit_name, inst))
 494                                         log_debug("%s: %s has alias %s", __func__, unit_name, inst);
 495
 496                                 log_info("%s: %s+%s → %s", __func__, *t, instance, inst);
 497                                 r = set_consume(names, inst);
 498                         } else {
 499                                 if (!streq(unit_name, *t))
 500                                         log_debug("%s: %s has alias %s", __func__, unit_name, *t);
 501
 502                                 r = set_put_strdup(&names, *t);
 503                         }
 504                         if (r < 0)
 505                                 return r;
 506                 }
 507         }
 508
 509         if (!fragment && name_type == UNIT_NAME_INSTANCE) {
 510                 /* Look for a fragment under the template name */
 511
 512                 r = unit_name_template(unit_name, &template);
 513                 if (r < 0)
 514                         return log_error_errno(r, "Failed to determine template name: %m");
 515
 516                 r = unit_ids_map_get(unit_ids_map, template, &fragment);
 517                 if (r < 0 && !IN_SET(r, -ENOENT, -ENXIO))
 518                         return log_debug_errno(r, "Cannot load template %s: %m", template);
 519
 520                 if (fragment) {
 521                         /* Add any aliases of the original name to the set of names */
 522                         nnn = hashmap_get(unit_name_map, basename(fragment));
 523                         STRV_FOREACH(t, nnn) {
 524                                 _cleanup_free_ char *inst = NULL;
 525                                 const char *inst_fragment = NULL;
 526
 527                                 r = unit_name_replace_instance(*t, instance, &inst);
 528                                 if (r < 0)
 529                                         return log_debug_errno(r, "Cannot build instance name %s+%s: %m", template, instance);
 530
 531                                 /* Exclude any aliases that point in some other direction. */
 532                                 r = unit_ids_map_get(unit_ids_map, inst, &inst_fragment);
 533                                 if (r < 0 && !IN_SET(r, -ENOENT, -ENXIO))
 534                                         return log_debug_errno(r, "Cannot find instance fragment %s: %m", inst);
 535
 536                                 if (inst_fragment &&
 537                                     !streq(basename(inst_fragment), basename(fragment))) {
 538                                         log_debug("Instance %s has fragment %s and is not an alias of %s.",
 539                                                   inst, inst_fragment, unit_name);
 540                                         continue;
 541                                 }
 542
 543                                 if (!streq(unit_name, inst))
 544                                         log_debug("%s: %s has alias %s", __func__, unit_name, inst);
 545                                 r = set_consume(names, TAKE_PTR(inst));
 546                                 if (r < 0)
 547                                         return r;
 548                         }
 549                 }
 550         }
 551
 552         *ret_fragment_path = fragment;
 553         *ret_names = TAKE_PTR(names);
 554
 555         // FIXME: if instance, consider any unit names with different template name
 556         return 0;
 557 }
 558
 559 static const char * const rlmap[] = {
 560         "emergency", SPECIAL_EMERGENCY_TARGET,
 561         "-b",        SPECIAL_EMERGENCY_TARGET,
 562         "rescue",    SPECIAL_RESCUE_TARGET,
 563         "single",    SPECIAL_RESCUE_TARGET,
 564         "-s",        SPECIAL_RESCUE_TARGET,
 565         "s",         SPECIAL_RESCUE_TARGET,
 566         "S",         SPECIAL_RESCUE_TARGET,
 567         "1",         SPECIAL_RESCUE_TARGET,
 568         "2",         SPECIAL_MULTI_USER_TARGET,
 569         "3",         SPECIAL_MULTI_USER_TARGET,
 570         "4",         SPECIAL_MULTI_USER_TARGET,
 571         "5",         SPECIAL_GRAPHICAL_TARGET,
 572         NULL
 573 };
 574
 575 static const char * const rlmap_initrd[] = {
 576         "emergency", SPECIAL_EMERGENCY_TARGET,
 577         "rescue",    SPECIAL_RESCUE_TARGET,
 578         NULL
 579 };
 580
 581 const char* runlevel_to_target(const char *word) {
 582         const char * const *rlmap_ptr;
 583         size_t i;
 584
 585         if (!word)
 586                 return NULL;
 587
 588         if (in_initrd()) {
 589                 word = startswith(word, "rd.");
 590                 if (!word)
 591                         return NULL;
 592         }
 593
 594         rlmap_ptr = in_initrd() ? rlmap_initrd : rlmap;
 595
 596         for (i = 0; rlmap_ptr[i]; i += 2)
 597                 if (streq(word, rlmap_ptr[i]))
 598                         return rlmap_ptr[i+1];
 599
 600         return NULL;
 601 }