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 #include "lib/util/samba_util.h"
  24
  25 static int server_id_db_check_exclusive(
  26         struct server_id_db *db, const char *name,
  27         unsigned num_servers, struct server_id *servers);
  28
  29 int server_id_db_set_exclusive(struct server_id_db *db, const char *name)
  30 {
  31         int ret;
  32         unsigned num_servers;
  33         struct server_id *servers;
  34
  35         ret = server_id_db_add(db, name);
  36         if (ret != 0) {
  37                 return ret;
  38         }
  39
  40         ret = server_id_db_lookup(db, name, talloc_tos(),
  41                                   &num_servers, &servers);
  42         if (ret != 0) {
  43                 goto done;
  44         }
  45
  46         /*
  47          * Remove entries from the server_id_db for processes that have died
  48          * and could not clean up. This is racy, as two processes could
  49          * simultaneously try to register a name. Both would succeed in the
  50          * server_id_db_add call, and both would see their peer active during
  51          * the check_exclusive call. Both would get an EEXIST, and nobody
  52          * would be able to register itself. But this is okay, as this is
  53          * meant to be a cleanup routine, and normally only one daemon should
  54          * start up at a time anyway. Getting this "right" would mean we would
  55          * have to add locking to server_id_db, or add a dependency on
  56          * serverids_exist to server_id_db. Both are too heavy-weight for my
  57          * taste.
  58          */
  59
  60         ret = server_id_db_check_exclusive(db, name, num_servers, servers);
  61         TALLOC_FREE(servers);
  62
  63 done:
  64         if (ret != 0) {
  65                 server_id_db_remove(db, name);
  66         }
  67         return ret;
  68 }
  69
  70 static int server_id_db_check_exclusive(
  71         struct server_id_db *db, const char *name,
  72         unsigned num_servers, struct server_id *servers)
  73 {
  74         struct server_id me = server_id_db_pid(db);
  75         int i;
  76
  77         for (i=0; i<num_servers; i++) {
  78                 int ret;
  79
  80                 if (server_id_same_process(&me, &servers[i])) {
  81                         /*
  82                          * I am always around ... :-)
  83                          */
  84                         continue;
  85                 }
  86
  87                 if (serverid_exists(&servers[i])) {
  88                         return EEXIST;
  89                 }
  90
  91                 ret = server_id_db_prune_name(db, name, servers[i]);
  92                 if (ret != 0) {
  93                         return ret;
  94                 }
  95         }
  96
  97         return 0;
  98 }