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 "lib/util/server_id.h"
  23 #include "serverid.h"
  24 #include "lib/util/samba_util.h"
  25
  26 static int server_id_db_check_exclusive(
  27         struct server_id_db *db, const char *name,
  28         unsigned num_servers, struct server_id *servers);
  29
  30 int server_id_db_set_exclusive(struct server_id_db *db, const char *name)
  31 {
  32         int ret;
  33         unsigned num_servers;
  34         struct server_id *servers;
  35
  36         ret = server_id_db_add(db, name);
  37         if (ret != 0) {
  38                 return ret;
  39         }
  40
  41         ret = server_id_db_lookup(db, name, talloc_tos(),
  42                                   &num_servers, &servers);
  43         if (ret != 0) {
  44                 goto done;
  45         }
  46
  47         /*
  48          * Remove entries from the server_id_db for processes that have died
  49          * and could not clean up. This is racy, as two processes could
  50          * simultaneously try to register a name. Both would succeed in the
  51          * server_id_db_add call, and both would see their peer active during
  52          * the check_exclusive call. Both would get an EEXIST, and nobody
  53          * would be able to register itself. But this is okay, as this is
  54          * meant to be a cleanup routine, and normally only one daemon should
  55          * start up at a time anyway. Getting this "right" would mean we would
  56          * have to add locking to server_id_db, or add a dependency on
  57          * serverids_exist to server_id_db. Both are too heavy-weight for my
  58          * taste.
  59          */
  60
  61         ret = server_id_db_check_exclusive(db, name, num_servers, servers);
  62         TALLOC_FREE(servers);
  63
  64 done:
  65         if (ret != 0) {
  66                 server_id_db_remove(db, name);
  67         }
  68         return ret;
  69 }
  70
  71 static int server_id_db_check_exclusive(
  72         struct server_id_db *db, const char *name,
  73         unsigned num_servers, struct server_id *servers)
  74 {
  75         struct server_id me = server_id_db_pid(db);
  76         unsigned i;
  77
  78         for (i=0; i<num_servers; i++) {
  79                 int ret;
  80
  81                 if (server_id_same_process(&me, &servers[i])) {
  82                         /*
  83                          * I am always around ... :-)
  84                          */
  85                         continue;
  86                 }
  87
  88                 if (serverid_exists(&servers[i])) {
  89                         return EEXIST;
  90                 }
  91
  92                 ret = server_id_db_prune_name(db, name, servers[i]);
  93                 if (ret != 0) {
  94                         return ret;
  95                 }
  96         }
  97
  98         return 0;
  99 }