source3/lib/server_id_db_util.c

   1 /*
   2  * Unix SMB/CIFS implementation.
   3  * Utils around server_id_db with more dependencies
   4  * Copyright (C) Volker Lendecke 2014
   5  *
   6  * This program is free software; you can redistribute it and/or modify
   7  * it under the terms of the GNU General Public License as published by
   8  * the Free Software Foundation; either version 3 of the License, or
   9  * (at your option) any later version.
  10  *
  11  * This program is distributed in the hope that it will be useful,
  12  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  13  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  14  * GNU General Public License for more details.
  15  *
  16  * You should have received a copy of the GNU General Public License
  17  * along with this program.  If not, see <http://www.gnu.org/licenses/>.
  18  */
  19
  20 #include "replace.h"
  21 #include "server_id_db_util.h"
  22 #include "serverid.h"
  23
  24 static int server_id_db_check_exclusive(
  25         struct server_id_db *db, const char *name,
  26         unsigned num_servers, struct server_id *servers);
  27
  28 int server_id_db_set_exclusive(struct server_id_db *db, const char *name)
  29 {
  30         int ret;
  31         unsigned num_servers;
  32         struct server_id *servers;
  33
  34         ret = server_id_db_add(db, name);
  35         if (ret != 0) {
  36                 return ret;
  37         }
  38
  39         ret = server_id_db_lookup(db, name, talloc_tos(),
  40                                   &num_servers, &servers);
  41         if (ret != 0) {
  42                 goto done;
  43         }
  44
  45         /*
  46          * Remove entries from the server_id_db for processes that have died
  47          * and could not clean up. This is racy, as two processes could
  48          * simultaneously try to register a name. Both would succeed in the
  49          * server_id_db_add call, and both would see their peer active during
  50          * the check_exclusive call. Both would get an EEXIST, and nobody
  51          * would be able to register itself. But this is okay, as this is
  52          * meant to be a cleanup routine, and normally only one daemon should
  53          * start up at a time anyway. Getting this "right" would mean we would
  54          * have to add locking to server_id_db, or add a dependency on
  55          * serverids_exist to server_id_db. Both are too heavy-weight for my
  56          * taste.
  57          */
  58
  59         ret = server_id_db_check_exclusive(db, name, num_servers, servers);
  60         TALLOC_FREE(servers);
  61
  62 done:
  63         if (ret != 0) {
  64                 server_id_db_remove(db, name);
  65         }
  66         return ret;
  67 }
  68
  69 static int server_id_db_check_exclusive(
  70         struct server_id_db *db, const char *name,
  71         unsigned num_servers, struct server_id *servers)
  72 {
  73         struct server_id me = server_id_db_pid(db);
  74         bool exists[num_servers];
  75         bool ok;
  76         int i;
  77
  78         ok = serverids_exist(servers, num_servers, exists);
  79         if (!ok) {
  80                 return ENOMEM;
  81         }
  82
  83         for (i=0; i<num_servers; i++) {
  84                 int ret;
  85
  86                 if (server_id_same_process(&me, &servers[i])) {
  87                         /*
  88                          * I am always around ... :-)
  89                          */
  90                         continue;
  91                 }
  92
  93                 if (exists[i]) {
  94                         return EEXIST;
  95                 }
  96
  97                 ret = server_id_db_prune_name(db, name, servers[i]);
  98                 if (ret != 0) {
  99                         return ret;
 100                 }
 101         }
 102
 103         return 0;
 104 }