src/src/search.c

   1 /* $Cambridge: exim/src/src/search.c,v 1.6 2007/08/29 14:02:22 ph10 Exp $ */
   2
   3 /*************************************************
   4 *     Exim - an Internet mail transport agent    *
   5 *************************************************/
   6
   7 /* Copyright (c) University of Cambridge 1995 - 2007 */
   8 /* See the file NOTICE for conditions of use and distribution. */
   9
  10 /* A set of functions to search databases in various formats. An open
  11 database is represented by a void * value which is returned from a lookup-
  12 specific "open" function. These are now all held in individual modules in the
  13 lookups subdirectory and the functions here form a generic interface.
  14
  15 Caching is used to improve performance. Open files are cached until a tidyup
  16 function is called, and for each file the result of the last lookup is cached.
  17 However, if too many files are opened, some of those that are not in use have
  18 to be closed. Those open items that use real files are kept on a LRU chain to
  19 help with this.
  20
  21 All the data is held in permanent store so as to be independent of the stacking
  22 pool that is reset from time to time. In fact, we use malloc'd store so that it
  23 can be freed when the caches are tidied up. It isn't actually clear whether
  24 this is a benefit or not, to be honest. */
  25
  26 #include "exim.h"
  27
  28
  29 /* Tree in which to cache open files until tidyup called. */
  30
  31 static tree_node *search_tree = NULL;
  32
  33 /* Two-way chain of open databases that use real files. This is maintained in
  34 recently-used order for the purposes of closing the least recently used when
  35 too many files are open. */
  36
  37 static tree_node *open_top = NULL;
  38 static tree_node *open_bot = NULL;
  39
  40 /* Count of open databases that use real files */
  41
  42 static int open_filecount = 0;
  43
  44 /* Allow us to reset store used for lookups and lookup caching */
  45
  46 static void *search_reset_point = NULL;
  47
  48
  49
  50 /*************************************************
  51 *      Validate a plain lookup type name         *
  52 *************************************************/
  53
  54 /* Only those names that are recognized and whose code is included in the
  55 binary give an OK response. Use a binary chop search now that the list has got
  56 so long.
  57
  58 Arguments:
  59   name       lookup type name - not necessarily zero terminated (e.g. dbm*)
  60   len        length of the name
  61
  62 Returns:     +ve => valid lookup name; value is offset in lookup_list
  63              -ve => invalid name; message in search_error_message.
  64 */
  65
  66 int
  67 search_findtype(uschar *name, int len)
  68 {
  69 int bot = 0;
  70 int top = lookup_list_count;
  71 while (top > bot)
  72   {
  73   int mid = (top + bot)/2;
  74   int c = Ustrncmp(name, lookup_list[mid].name, len);
  75
  76   /* If c == 0 we have matched the incoming name with the start of the search
  77   type name. However, some search types are substrings of others (e.g. nis and
  78   nisplus) so we need to check that the lengths are the same. The length of the
  79   type name cannot be shorter (else c would not be 0); if it is not equal it
  80   must be longer, and in that case, the incoming name comes before the name we
  81   are testing. By leaving c == 0 when the lengths are different, and doing a
  82   > 0 test below, this all falls out correctly. */
  83
  84   if (c == 0 && Ustrlen(lookup_list[mid].name) == len)
  85     {
  86     if (lookup_list[mid].find != NULL) return mid;
  87     search_error_message  = string_sprintf("lookup type \"%.*s\" is not "
  88       "available (not in the binary - check buildtime LOOKUP configuration)",
  89       len, name);
  90     return -1;
  91     }
  92
  93   if (c > 0) bot = mid + 1; else top = mid;
  94   }
  95
  96 search_error_message = string_sprintf("unknown lookup type \"%.*s\"",len,name);
  97 return -1;
  98 }
  99
 100
 101
 102 /*************************************************
 103 *       Validate a full lookup type name         *
 104 *************************************************/
 105
 106 /* This function recognizes the "partial-" prefix and also terminating * and *@
 107 suffixes.
 108
 109 Arguments:
 110   name         the full lookup type name
 111   ptypeptr     where to put the partial type
 112                  after subtraction of 1024 or 2048:
 113                    negative     => no partial matching
 114                    non-negative => minimum number of non-wild components
 115   ptypeaff     where to put a pointer to the affix
 116                  the affix is within name if supplied therein
 117                  otherwise it's a literal string
 118   afflen       the length of the affix
 119   starflags    where to put the SEARCH_STAR and SEARCH_STARAT flags
 120
 121 Returns:     +ve => valid lookup name; value is offset in lookup_list
 122              -ve => invalid name; message in search_error_message.
 123 */
 124
 125 int
 126 search_findtype_partial(uschar *name, int *ptypeptr, uschar **ptypeaff,
 127   int *afflen, int *starflags)
 128 {
 129 int len, stype;
 130 int pv = -1;
 131 uschar *ss = name;
 132
 133 *starflags = 0;
 134 *ptypeaff = NULL;
 135
 136 /* Check for a partial matching type. It must start with "partial", optionally
 137 followed by a sequence of digits. If this is followed by "-", the affix is the
 138 default "*." string. Otherwise we expect an affix in parentheses. Affixes are a
 139 limited number of characters, not including parens. */
 140
 141 if (Ustrncmp(name, "partial", 7) == 0)
 142   {
 143   ss += 7;
 144   if (isdigit (*ss))
 145     {
 146     pv = 0;
 147     while (isdigit(*ss)) pv = pv*10 + *ss++ - '0';
 148     }
 149   else pv = 2;         /* Default number of wild components */
 150
 151   if (*ss == '(')
 152     {
 153     *ptypeaff = ++ss;
 154     while (ispunct(*ss) && *ss != ')') ss++;
 155     if (*ss != ')') goto BAD_TYPE;
 156     *afflen = ss++ - *ptypeaff;
 157     }
 158   else if (*ss++ == '-')
 159     {
 160     *ptypeaff = US "*.";
 161     *afflen = 2;
 162     }
 163   else
 164     {
 165     BAD_TYPE:
 166     search_error_message = string_sprintf("format error in lookup type \"%s\"",
 167       name);
 168     return -1;
 169     }
 170   }
 171
 172 /* Now we are left with a lookup name, possibly followed by * or *@. */
 173
 174 len = Ustrlen(ss);
 175 if (len >= 2 && Ustrncmp(ss + len - 2, "*@", 2) == 0)
 176   {
 177   *starflags |= SEARCH_STARAT;
 178   len -= 2;
 179   }
 180 else if (len >= 1 && ss[len-1]  == '*')
 181   {
 182   *starflags |= SEARCH_STAR;
 183   len--;
 184   }
 185
 186 /* Check for the individual search type. Only those that are actually in the
 187 binary are valid. For query-style types, "partial" and default types are
 188 erroneous. */
 189
 190 stype = search_findtype(ss, len);
 191 if (stype >= 0 && mac_islookup(stype, lookup_querystyle))
 192   {
 193   if (pv >= 0)
 194     {
 195     search_error_message = string_sprintf("\"partial\" is not permitted "
 196       "for lookup type \"%s\"", ss);
 197     return -1;
 198     }
 199   if ((*starflags & (SEARCH_STAR|SEARCH_STARAT)) != 0)
 200     {
 201     search_error_message = string_sprintf("defaults using \"*\" or \"*@\" are "
 202       "not permitted for lookup type \"%s\"", ss);
 203     return -1;
 204     }
 205   }
 206
 207 *ptypeptr = pv;
 208 return stype;
 209 }
 210
 211
 212
 213 /*************************************************
 214 *               Release cached resources         *
 215 *************************************************/
 216
 217 /* When search_open is called it caches the "file" that it opens in
 218 search_tree. The name of the tree node is a concatenation of the search type
 219 with the file name. For query-style lookups, the file name is empty. Real files
 220 are normally closed only when this tidyup routine is called, typically at the
 221 end of sections of code where a number of lookups might occur. However, if too
 222 many files are open simultaneously, some get closed beforehand. They can't be
 223 removed from the tree. There is also a general tidyup function which is called
 224 for the lookup driver, if it exists.
 225
 226 First, there is an internal, recursive subroutine.
 227
 228 Argument:    a pointer to a search_openfile tree node
 229 Returns:     nothing
 230 */
 231
 232 static void
 233 tidyup_subtree(tree_node *t)
 234 {
 235 search_cache *c = (search_cache *)(t->data.ptr);
 236 if (t->left != NULL) tidyup_subtree(t->left);
 237 if (t->right != NULL) tidyup_subtree(t->right);
 238 if (c != NULL &&
 239     c->handle != NULL &&
 240     lookup_list[c->search_type].close != NULL)
 241   lookup_list[c->search_type].close(c->handle);
 242 }
 243
 244
 245 /* The external entry point
 246
 247 Argument: none
 248 Returns:  nothing
 249 */
 250
 251 void
 252 search_tidyup(void)
 253 {
 254 int i;
 255 int old_pool = store_pool;
 256
 257 DEBUG(D_lookup) debug_printf("search_tidyup called\n");
 258
 259 /* Close individually each cached open file. */
 260
 261 store_pool = POOL_SEARCH;
 262 if (search_tree != NULL)
 263   {
 264   tidyup_subtree(search_tree);
 265   search_tree = NULL;
 266   }
 267 open_top = open_bot = NULL;
 268 open_filecount = 0;
 269
 270 /* Call the general tidyup entry for any drivers that have one. */
 271
 272 for (i = 0; i < lookup_list_count; i++)
 273   if (lookup_list[i].tidy != NULL) (lookup_list[i].tidy)();
 274
 275 if (search_reset_point != NULL) store_reset(search_reset_point);
 276 search_reset_point = NULL;
 277 store_pool = old_pool;
 278 }
 279
 280
 281
 282
 283 /*************************************************
 284 *             Open search database               *
 285 *************************************************/
 286
 287 /* A mode, and lists of owners and groups, are passed over for checking in
 288 the cases where the database is one or more files. Return NULL, with a message
 289 pointed to by message, in cases of error.
 290
 291 For search types that use a file or files, check up on the mode after
 292 opening. It is tempting to do a stat before opening the file, and use it as
 293 an existence check. However, doing that opens a small security loophole in
 294 that the status could be changed before the file is opened. Can't quite see
 295 what problems this might lead to, but you can't be too careful where security
 296 is concerned. Fstat() on an open file can normally be expected to succeed,
 297 but there are some NFS states where it does not.
 298
 299 There are two styles of query: (1) in the "single-key+file" style, a single
 300 key string and a file name are given, for example, for linear searches, DBM
 301 files, or for NIS. (2) In the "query" style, no "filename" is given; instead
 302 just a single query string is passed. This applies to multiple-key lookup
 303 types such as NIS+.
 304
 305 Before opening, scan the tree of cached files to see if this file is already
 306 open for the correct search type. If so, return the saved handle. If not, put
 307 the handle in the tree for possible subsequent use. See search_tidyup above for
 308 closing all the cached files.
 309
 310 A count of open databases which use real files is maintained, and if this
 311 gets too large, we have to close a cached file. Its entry remains in the tree,
 312 but is marked closed.
 313
 314 Arguments:
 315   filename       the name of the file for single-key+file style lookups,
 316                  NULL for query-style lookups
 317   search_type    the type of search required
 318   modemask       if a real single file is used, this specifies mode bits that
 319                  must not be set; otherwise it is ignored
 320   owners         if a real single file is used, this specifies the possible
 321                  owners of the file; otherwise it is ignored
 322   owngroups      if a real single file is used, this specifies the possible
 323                  group owners of the file; otherwise it is ignored
 324
 325 Returns:         an identifying handle for the open database;
 326                  this is the pointer to the tree block in the
 327                  cache of open files; return NULL on open failure, with
 328                  a message in search_error_message
 329 */
 330
 331 void *
 332 search_open(uschar *filename, int search_type, int modemask, uid_t *owners,
 333   gid_t *owngroups)
 334 {
 335 void *handle;
 336 tree_node *t;
 337 search_cache *c;
 338 lookup_info *lk = lookup_list + search_type;
 339 uschar keybuffer[256];
 340 int old_pool = store_pool;
 341
 342 /* Change to the search store pool and remember our reset point */
 343
 344 store_pool = POOL_SEARCH;
 345 if (search_reset_point == NULL) search_reset_point = store_get(0);
 346
 347 DEBUG(D_lookup) debug_printf("search_open: %s \"%s\"\n", lk->name,
 348   (filename == NULL)? US"NULL" : filename);
 349
 350 /* See if we already have this open for this type of search, and if so,
 351 pass back the tree block as the handle. The key for the tree node is the search
 352 type plus '0' concatenated with the file name. There may be entries in the tree
 353 with closed files if a lot of files have been opened. */
 354
 355 sprintf(CS keybuffer, "%c%.254s", search_type + '0',
 356   (filename == NULL)? US"" : filename);
 357
 358 if ((t = tree_search(search_tree, keybuffer)) != NULL)
 359   {
 360   c = (search_cache *)(t->data.ptr);
 361   if (c->handle != NULL)
 362     {
 363     DEBUG(D_lookup) debug_printf("  cached open\n");
 364     store_pool = old_pool;
 365     return t;
 366     }
 367   DEBUG(D_lookup) debug_printf("  cached closed\n");
 368   }
 369
 370 /* Otherwise, we need to open the file or database - each search type has its
 371 own code, which is now split off into separately compiled modules. Before doing
 372 this, if the search type is one that uses real files, check on the number that
 373 we are holding open in the cache. If the limit is reached, close the least
 374 recently used one. */
 375
 376 if (lk->type == lookup_absfile && open_filecount >= lookup_open_max)
 377   {
 378   if (open_bot == NULL)
 379     log_write(0, LOG_MAIN|LOG_PANIC, "too many lookups open, but can't find "
 380       "one to close");
 381   else
 382     {
 383     search_cache *c = (search_cache *)(open_bot->data.ptr);
 384     DEBUG(D_lookup) debug_printf("Too many lookup files open\n  closing %s\n",
 385       open_bot->name);
 386     open_bot = c->up;
 387     if (open_bot != NULL)
 388       ((search_cache *)(open_bot->data.ptr))->down = NULL;
 389     else
 390       open_top = NULL;
 391     ((lookup_list + c->search_type)->close)(c->handle);
 392     c->handle = NULL;
 393     open_filecount--;
 394     }
 395   }
 396
 397 /* If opening is successful, call the file-checking function if there is one,
 398 and if all is still well, enter the open database into the tree. */
 399
 400 handle = (lk->open)(filename, &search_error_message);
 401 if (handle == NULL)
 402   {
 403   store_pool = old_pool;
 404   return NULL;
 405   }
 406
 407 if (lk->check != NULL &&
 408    !lk->check(handle, filename, modemask, owners, owngroups,
 409      &search_error_message))
 410   {
 411   lk->close(handle);
 412   store_pool = old_pool;
 413   return NULL;
 414   }
 415
 416 /* If this is a search type that uses real files, keep count. */
 417
 418 if (lk->type == lookup_absfile) open_filecount++;
 419
 420 /* If we found a previously opened entry in the tree, re-use it; otherwise
 421 insert a new entry. On re-use, leave any cached lookup data and the lookup
 422 count alone. */
 423
 424 if (t == NULL)
 425   {
 426   t = store_get(sizeof(tree_node) + Ustrlen(keybuffer));
 427   t->data.ptr = c = store_get(sizeof(search_cache));
 428   c->item_cache = NULL;
 429   Ustrcpy(t->name, keybuffer);
 430   tree_insertnode(&search_tree, t);
 431   }
 432 else c = t->data.ptr;
 433
 434 c->handle = handle;
 435 c->search_type = search_type;
 436 c->up = c->down = NULL;
 437
 438 store_pool = old_pool;
 439 return t;
 440 }
 441
 442
 443
 444
 445
 446 /*************************************************
 447 *  Internal function: Find one item in database  *
 448 *************************************************/
 449
 450 /* The answer is always put into dynamic store. The last lookup for each handle
 451 is cached.
 452
 453 Arguments:
 454   handle       the handle from search_open; points to tree node
 455   filename     the filename that was handed to search_open, or
 456                NULL for query-style searches
 457   keystring    the keystring for single-key+file lookups, or
 458                the querystring for query-style lookups
 459
 460 Returns:       a pointer to a dynamic string containing the answer,
 461                or NULL if the query failed or was deferred; in the
 462                latter case, search_find_defer is set TRUE; after an unusual
 463                failure, there may be a message in search_error_message.
 464 */
 465
 466 static uschar *
 467 internal_search_find(void *handle, uschar *filename, uschar *keystring)
 468 {
 469 tree_node *t = (tree_node *)handle;
 470 search_cache *c = (search_cache *)(t->data.ptr);
 471 uschar *data = NULL;
 472 int search_type = t->name[0] - '0';
 473 int old_pool = store_pool;
 474
 475 /* Lookups that return DEFER may not always set an error message. So that
 476 the callers don't have to test for NULL, set an empty string. */
 477
 478 search_error_message = US"";
 479 search_find_defer = FALSE;
 480
 481 DEBUG(D_lookup) debug_printf("internal_search_find: file=\"%s\"\n  "
 482   "type=%s key=\"%s\"\n", filename,
 483   lookup_list[search_type].name, keystring);
 484
 485 /* Insurance. If the keystring is empty, just fail. */
 486
 487 if (keystring[0] == 0) return NULL;
 488
 489 /* Use the special store pool for search data */
 490
 491 store_pool = POOL_SEARCH;
 492
 493 /* Look up the data for the key, unless it is already in the cache for this
 494 file. No need to check c->item_cache for NULL, tree_search will do so. */
 495
 496 if ((t = tree_search(c->item_cache, keystring)) == NULL)
 497   {
 498   BOOL do_cache = TRUE;
 499   int keylength = Ustrlen(keystring);
 500
 501   DEBUG(D_lookup)
 502     {
 503     if (filename != NULL)
 504       debug_printf("file lookup required for %s\n  in %s\n",
 505         keystring, filename);
 506     else
 507       debug_printf("database lookup required for %s\n", keystring);
 508     }
 509
 510   /* Call the code for the different kinds of search. DEFER is handled
 511   like FAIL, except that search_find_defer is set so the caller can
 512   distinguish if necessary. */
 513
 514   if (lookup_list[search_type].find(c->handle, filename, keystring, keylength,
 515       &data, &search_error_message, &do_cache) == DEFER)
 516     {
 517     search_find_defer = TRUE;
 518     }
 519
 520   /* A record that has been found is now in data, which is either NULL
 521   or points to a bit of dynamic store. Cache the result of the lookup if
 522   caching is permitted. Lookups can disable caching, when they did something
 523   that changes their data. The mysql and pgsql lookups do this when an
 524   UPDATE/INSERT query was executed. */
 525
 526   else if (do_cache)
 527     {
 528     int len = keylength + 1;
 529     t = store_get(sizeof(tree_node) + len);
 530     memcpy(t->name, keystring, len);
 531     t->data.ptr = data;
 532     tree_insertnode(&c->item_cache, t);
 533     }
 534
 535   /* If caching was disabled, empty the cache tree. We just set the cache
 536   pointer to NULL here, because we cannot release the store at this stage. */
 537
 538   else
 539     {
 540     DEBUG(D_lookup) debug_printf("lookup forced cache cleanup\n");
 541     c->item_cache = NULL;
 542     }
 543   }
 544
 545 /* Data was in the cache already; set the pointer from the tree node */
 546
 547 else
 548   {
 549   data = US t->data.ptr;
 550   DEBUG(D_lookup) debug_printf("cached data used for lookup of %s%s%s\n",
 551     keystring,
 552     (filename == NULL)? US"" : US"\n  in ",
 553     (filename == NULL)? US"" : filename);
 554   }
 555
 556 /* Debug: output the answer */
 557
 558 DEBUG(D_lookup)
 559   {
 560   if (data == NULL)
 561     {
 562     if (search_find_defer) debug_printf("lookup deferred: %s\n",
 563       search_error_message);
 564     else debug_printf("lookup failed\n");
 565     }
 566   else debug_printf("lookup yielded: %s\n", data);
 567   }
 568
 569 /* Return it in new dynamic store in the regular pool */
 570
 571 store_pool = old_pool;
 572 return (data == NULL)? NULL : string_copy(data);
 573 }
 574
 575
 576
 577
 578 /*************************************************
 579 * Find one item in database, possibly wildcarded *
 580 *************************************************/
 581
 582 /* This function calls the internal function above; once only if there
 583 is no partial matching, but repeatedly when partial matching is requested.
 584
 585 Arguments:
 586   handle         the handle from search_open
 587   filename       the filename that was handed to search_open, or
 588                    NULL for query-style searches
 589   keystring      the keystring for single-key+file lookups, or
 590                    the querystring for query-style lookups
 591   partial        -1 means no partial matching;
 592                    otherwise it's the minimum number of components;
 593   affix          the affix string for partial matching
 594   affixlen       the length of the affix string
 595   starflags      SEARCH_STAR and SEARCH_STARAT flags
 596   expand_setup   pointer to offset for setting up expansion strings;
 597                  don't do any if < 0
 598
 599 Returns:         a pointer to a dynamic string containing the answer,
 600                  or NULL if the query failed or was deferred; in the
 601                  latter case, search_find_defer is set TRUE
 602 */
 603
 604 uschar *
 605 search_find(void *handle, uschar *filename, uschar *keystring, int partial,
 606   uschar *affix, int affixlen, int starflags, int *expand_setup)
 607 {
 608 tree_node *t = (tree_node *)handle;
 609 BOOL set_null_wild = FALSE;
 610 uschar *yield;
 611
 612 DEBUG(D_lookup)
 613   {
 614   if (partial < 0) affixlen = 99;   /* So that "NULL" prints */
 615   debug_printf("search_find: file=\"%s\"\n  key=\"%s\" "
 616     "partial=%d affix=%.*s starflags=%x\n",
 617     (filename == NULL)? US"NULL" : filename,
 618     keystring, partial, affixlen, affix, starflags);
 619   }
 620
 621 /* Arrange to put this database at the top of the LRU chain if it is a type
 622 that opens real files. */
 623
 624 if (open_top != (tree_node *)handle &&
 625     lookup_list[t->name[0]-'0'].type == lookup_absfile)
 626   {
 627   search_cache *c = (search_cache *)(t->data.ptr);
 628   tree_node *up = c->up;
 629   tree_node *down = c->down;
 630
 631   /* Cut it out of the list. A newly opened file will a NULL up pointer.
 632   Otherwise there will be a non-NULL up pointer, since we checked above that
 633   this block isn't already at the top of the list. */
 634
 635   if (up != NULL)
 636     {
 637     ((search_cache *)(up->data.ptr))->down = down;
 638     if (down != NULL)
 639       ((search_cache *)(down->data.ptr))->up = up;
 640     else open_bot = up;
 641     }
 642
 643   /* Now put it at the head of the list. */
 644
 645   c->up = NULL;
 646   c->down = open_top;
 647   if (open_top == NULL) open_bot = t; else
 648     ((search_cache *)(open_top->data.ptr))->up = t;
 649   open_top = t;
 650   }
 651
 652 DEBUG(D_lookup)
 653   {
 654   tree_node *t = open_top;
 655   debug_printf("LRU list:\n");
 656   while (t != NULL)
 657     {
 658     search_cache *c = (search_cache *)(t->data.ptr);
 659     debug_printf("  %s\n", t->name);
 660     if (t == open_bot) debug_printf("  End\n");
 661     t = c->down;
 662     }
 663   }
 664
 665 /* First of all, try to match the key string verbatim. If matched a complete
 666 entry but could have been partial, flag to set up variables. */
 667
 668 yield = internal_search_find(handle, filename, keystring);
 669 if (search_find_defer) return NULL;
 670 if (yield != NULL) { if (partial >= 0) set_null_wild = TRUE; }
 671
 672 /* Not matched a complete entry; handle partial lookups, but only if the full
 673 search didn't defer. Don't use string_sprintf() to construct the initial key,
 674 just in case the original key is too long for the string_sprintf() buffer (it
 675 *has* happened!). The case of a zero-length affix has to be treated specially.
 676 */
 677
 678 else if (partial >= 0)
 679   {
 680   int len = Ustrlen(keystring);
 681   uschar *keystring2;
 682
 683   /* Try with the affix on the front, except for a zero-length affix */
 684
 685   if (affixlen == 0) keystring2 = keystring; else
 686     {
 687     keystring2 = store_get(len + affixlen + 1);
 688     Ustrncpy(keystring2, affix, affixlen);
 689     Ustrcpy(keystring2 + affixlen, keystring);
 690     DEBUG(D_lookup) debug_printf("trying partial match %s\n", keystring2);
 691     yield = internal_search_find(handle, filename, keystring2);
 692     if (search_find_defer) return NULL;
 693     }
 694
 695   /* The key in its entirety did not match a wild entry; try chopping off
 696   leading components. */
 697
 698   if (yield == NULL)
 699     {
 700     int dotcount = 0;
 701     uschar *keystring3 = keystring2 + affixlen;
 702     uschar *s = keystring3;
 703     while (*s != 0) if (*s++ == '.') dotcount++;
 704
 705     while (dotcount-- >= partial)
 706       {
 707       while (*keystring3 != 0 && *keystring3 != '.') keystring3++;
 708
 709       /* If we get right to the end of the string (which will be the last time
 710       through this loop), we've failed if the affix is null. Otherwise do one
 711       last lookup for the affix itself, but if it is longer than 1 character,
 712       remove the last character if it is ".". */
 713
 714       if (*keystring3 == 0)
 715         {
 716         if (affixlen < 1) break;
 717         if (affixlen > 1 && affix[affixlen-1] == '.') affixlen--;
 718         Ustrncpy(keystring2, affix, affixlen);
 719         keystring2[affixlen] = 0;
 720         keystring3 = keystring2;
 721         }
 722       else
 723         {
 724         keystring3 -= affixlen - 1;
 725         if (affixlen > 0) Ustrncpy(keystring3, affix, affixlen);
 726         }
 727
 728       DEBUG(D_lookup) debug_printf("trying partial match %s\n", keystring3);
 729       yield = internal_search_find(handle, filename, keystring3);
 730       if (search_find_defer) return NULL;
 731       if (yield != NULL)
 732         {
 733         /* First variable is the wild part; second is the fixed part. Take care
 734         to get it right when keystring3 is just "*". */
 735
 736         if (expand_setup != NULL && *expand_setup >= 0)
 737           {
 738           int fixedlength = Ustrlen(keystring3) - affixlen;
 739           int wildlength = Ustrlen(keystring) - fixedlength - 1;
 740           *expand_setup += 1;
 741           expand_nstring[*expand_setup] = keystring;
 742           expand_nlength[*expand_setup] = wildlength;
 743           *expand_setup += 1;
 744           expand_nstring[*expand_setup] = keystring + wildlength + 1;
 745           expand_nlength[*expand_setup] = (fixedlength < 0)? 0 : fixedlength;
 746           }
 747         break;
 748         }
 749       keystring3 += affixlen;
 750       }
 751     }
 752
 753   else set_null_wild = TRUE; /* Matched a wild entry without any wild part */
 754   }
 755
 756 /* If nothing has been matched, but the option to look for "*@" is set, try
 757 replacing everthing to the left of @ by *. After a match, the wild part
 758 is set to the string to the left of the @. */
 759
 760 if (yield == NULL && (starflags & SEARCH_STARAT) != 0)
 761   {
 762   uschar *atat = Ustrrchr(keystring, '@');
 763   if (atat != NULL && atat > keystring)
 764     {
 765     int savechar;
 766     savechar = *(--atat);
 767     *atat = '*';
 768
 769     DEBUG(D_lookup) debug_printf("trying default match %s\n", atat);
 770     yield = internal_search_find(handle, filename, atat);
 771     *atat = savechar;
 772     if (search_find_defer) return NULL;
 773
 774     if (yield != NULL && expand_setup != NULL && *expand_setup >= 0)
 775       {
 776       *expand_setup += 1;
 777       expand_nstring[*expand_setup] = keystring;
 778       expand_nlength[*expand_setup] = atat - keystring + 1;
 779       *expand_setup += 1;
 780       expand_nstring[*expand_setup] = keystring;
 781       expand_nlength[*expand_setup] = 0;
 782       }
 783     }
 784   }
 785
 786 /* If we still haven't matched anything, and the option to look for "*" is set,
 787 try that. If we do match, the first variable (the wild part) is the whole key,
 788 and the second is empty. */
 789
 790 if (yield == NULL && (starflags & (SEARCH_STAR|SEARCH_STARAT)) != 0)
 791   {
 792   DEBUG(D_lookup) debug_printf("trying to match *\n");
 793   yield = internal_search_find(handle, filename, US"*");
 794   if (yield != NULL && expand_setup != NULL && *expand_setup >= 0)
 795     {
 796     *expand_setup += 1;
 797     expand_nstring[*expand_setup] = keystring;
 798     expand_nlength[*expand_setup] = Ustrlen(keystring);
 799     *expand_setup += 1;
 800     expand_nstring[*expand_setup] = keystring;
 801     expand_nlength[*expand_setup] = 0;
 802     }
 803   }
 804
 805 /* If this was a potentially partial lookup, and we matched either a
 806 complete non-wild domain entry, or we matched a wild-carded entry without
 807 chopping off any of the domain components, set up the expansion variables
 808 (if required) so that the first one is empty, and the second one is the
 809 fixed part of the domain. The set_null_wild flag is set only when yield is not
 810 NULL. */
 811
 812 if (set_null_wild && expand_setup != NULL && *expand_setup >= 0)
 813   {
 814   *expand_setup += 1;
 815   expand_nstring[*expand_setup] = keystring;
 816   expand_nlength[*expand_setup] = 0;
 817   *expand_setup += 1;
 818   expand_nstring[*expand_setup] = keystring;
 819   expand_nlength[*expand_setup] = Ustrlen(keystring);
 820   }
 821
 822 return yield;
 823 }
 824
 825 /* End of search.c */