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4d8a974ddc
This avoids the thundering herd problem when 5000 smbds exit simultaneously because the network went down.
703 lines
16 KiB
C
703 lines
16 KiB
C
/*
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Unix SMB/CIFS implementation.
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Generic, persistent and shared between processes cache mechanism for use
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by various parts of the Samba code
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Copyright (C) Rafal Szczesniak 2002
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Copyright (C) Volker Lendecke 2009
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This program is free software; you can redistribute it and/or modify
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it under the terms of the GNU General Public License as published by
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the Free Software Foundation; either version 3 of the License, or
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(at your option) any later version.
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This program is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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GNU General Public License for more details.
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You should have received a copy of the GNU General Public License
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along with this program. If not, see <http://www.gnu.org/licenses/>.
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*/
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#include "includes.h"
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#undef DBGC_CLASS
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#define DBGC_CLASS DBGC_TDB
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#define TIMEOUT_LEN 12
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#define CACHE_DATA_FMT "%12u/"
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#define READ_CACHE_DATA_FMT_TEMPLATE "%%12u/%%%us"
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#define BLOB_TYPE "DATA_BLOB"
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#define BLOB_TYPE_LEN 9
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static struct tdb_context *cache;
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static struct tdb_context *cache_notrans;
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/**
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* @file gencache.c
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* @brief Generic, persistent and shared between processes cache mechanism
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* for use by various parts of the Samba code
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*
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**/
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/**
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* Cache initialisation function. Opens cache tdb file or creates
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* it if does not exist.
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*
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* @return true on successful initialisation of the cache or
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* false on failure
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**/
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static bool gencache_init(void)
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{
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char* cache_fname = NULL;
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int open_flags = O_RDWR|O_CREAT;
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bool first_try = true;
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/* skip file open if it's already opened */
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if (cache) return True;
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cache_fname = lock_path("gencache.tdb");
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DEBUG(5, ("Opening cache file at %s\n", cache_fname));
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again:
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cache = tdb_open_log(cache_fname, 0, TDB_DEFAULT, open_flags, 0644);
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if (cache) {
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int ret;
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ret = tdb_check(cache, NULL, NULL);
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if (ret != 0) {
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tdb_close(cache);
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cache = NULL;
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if (!first_try) {
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DEBUG(0, ("gencache_init: tdb_check(%s) failed\n",
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cache_fname));
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return false;
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}
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first_try = false;
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DEBUG(0, ("gencache_init: tdb_check(%s) failed - retry after CLEAR_IF_FIRST\n",
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cache_fname));
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cache = tdb_open_log(cache_fname, 0, TDB_CLEAR_IF_FIRST, open_flags, 0644);
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if (cache) {
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tdb_close(cache);
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cache = NULL;
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goto again;
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}
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}
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}
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if (!cache && (errno == EACCES)) {
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open_flags = O_RDONLY;
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cache = tdb_open_log(cache_fname, 0, TDB_DEFAULT, open_flags,
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0644);
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if (cache) {
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DEBUG(5, ("gencache_init: Opening cache file %s read-only.\n", cache_fname));
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}
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}
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if (!cache) {
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DEBUG(5, ("Attempt to open gencache.tdb has failed.\n"));
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return False;
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}
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cache_fname = lock_path("gencache_notrans.tdb");
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DEBUG(5, ("Opening cache file at %s\n", cache_fname));
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cache_notrans = tdb_open_log(cache_fname, 0, TDB_CLEAR_IF_FIRST,
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open_flags, 0644);
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if (cache_notrans == NULL) {
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DEBUG(5, ("Opening %s failed: %s\n", cache_fname,
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strerror(errno)));
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tdb_close(cache);
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cache = NULL;
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return false;
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}
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return True;
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}
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static TDB_DATA last_stabilize_key(void)
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{
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TDB_DATA result;
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result.dptr = (uint8_t *)"@LAST_STABILIZED";
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result.dsize = 17;
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return result;
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}
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/**
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* Set an entry in the cache file. If there's no such
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* one, then add it.
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*
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* @param keystr string that represents a key of this entry
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* @param blob DATA_BLOB value being cached
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* @param timeout time when the value is expired
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*
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* @retval true when entry is successfuly stored
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* @retval false on failure
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**/
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bool gencache_set_data_blob(const char *keystr, const DATA_BLOB *blob,
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time_t timeout)
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{
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int ret;
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TDB_DATA databuf;
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char* val;
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time_t last_stabilize;
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static int writecount;
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if (tdb_data_cmp(string_term_tdb_data(keystr),
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last_stabilize_key()) == 0) {
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DEBUG(10, ("Can't store %s as a key\n", keystr));
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return false;
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}
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if ((keystr == NULL) || (blob == NULL)) {
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return false;
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}
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if (!gencache_init()) return False;
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val = talloc_asprintf(talloc_tos(), CACHE_DATA_FMT, (int)timeout);
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if (val == NULL) {
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return False;
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}
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val = talloc_realloc(NULL, val, char, talloc_array_length(val)-1);
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if (val == NULL) {
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return false;
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}
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val = (char *)talloc_append_blob(NULL, val, *blob);
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if (val == NULL) {
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return false;
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}
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DEBUG(10, ("Adding cache entry with key = %s and timeout ="
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" %s (%d seconds %s)\n", keystr, ctime(&timeout),
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(int)(timeout - time(NULL)),
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timeout > time(NULL) ? "ahead" : "in the past"));
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ret = tdb_store_bystring(
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cache_notrans, keystr,
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make_tdb_data((uint8_t *)val, talloc_array_length(val)),
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0);
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TALLOC_FREE(val);
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if (ret != 0) {
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return false;
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}
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/*
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* Every 100 writes within a single process, stabilize the cache with
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* a transaction. This is done to prevent a single transaction to
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* become huge and chew lots of memory.
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*/
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writecount += 1;
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if (writecount > lp_parm_int(-1, "gencache", "stabilize_count", 100)) {
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gencache_stabilize();
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writecount = 0;
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goto done;
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}
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/*
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* Every 5 minutes, call gencache_stabilize() to not let grow
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* gencache_notrans.tdb too large.
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*/
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last_stabilize = 0;
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databuf = tdb_fetch(cache_notrans, last_stabilize_key());
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if ((databuf.dptr != NULL)
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&& (databuf.dptr[databuf.dsize-1] == '\0')) {
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last_stabilize = atoi((char *)databuf.dptr);
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SAFE_FREE(databuf.dptr);
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}
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if ((last_stabilize
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+ lp_parm_int(-1, "gencache", "stabilize_interval", 300))
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< time(NULL)) {
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gencache_stabilize();
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}
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done:
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return ret == 0;
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}
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/**
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* Delete one entry from the cache file.
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*
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* @param keystr string that represents a key of this entry
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*
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* @retval true upon successful deletion
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* @retval false in case of failure
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**/
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bool gencache_del(const char *keystr)
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{
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bool exists, was_expired;
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bool ret = false;
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DATA_BLOB value;
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if (keystr == NULL) {
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return false;
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}
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if (!gencache_init()) return False;
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DEBUG(10, ("Deleting cache entry (key = %s)\n", keystr));
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/*
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* We delete an element by setting its timeout to 0. This way we don't
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* have to do a transaction on gencache.tdb every time we delete an
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* element.
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*/
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exists = gencache_get_data_blob(keystr, &value, NULL, &was_expired);
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if (!exists && was_expired) {
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/*
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* gencache_get_data_blob has implicitly deleted this
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* entry, so we have to return success here.
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*/
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return true;
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}
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if (exists) {
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data_blob_free(&value);
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ret = gencache_set(keystr, "", 0);
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}
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return ret;
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}
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static bool gencache_pull_timeout(char *val, time_t *pres, char **pendptr)
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{
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time_t res;
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char *endptr;
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res = strtol(val, &endptr, 10);
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if ((endptr == NULL) || (*endptr != '/')) {
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DEBUG(2, ("Invalid gencache data format: %s\n", val));
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return false;
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}
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if (pres != NULL) {
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*pres = res;
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}
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if (pendptr != NULL) {
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*pendptr = endptr;
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}
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return true;
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}
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/**
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* Get existing entry from the cache file.
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*
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* @param keystr string that represents a key of this entry
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* @param blob DATA_BLOB that is filled with entry's blob
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* @param timeout pointer to a time_t that is filled with entry's
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* timeout
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*
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* @retval true when entry is successfuly fetched
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* @retval False for failure
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**/
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bool gencache_get_data_blob(const char *keystr, DATA_BLOB *blob,
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time_t *timeout, bool *was_expired)
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{
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TDB_DATA databuf;
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time_t t;
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char *endptr;
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bool expired = false;
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if (keystr == NULL) {
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goto fail;
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}
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if (tdb_data_cmp(string_term_tdb_data(keystr),
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last_stabilize_key()) == 0) {
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DEBUG(10, ("Can't get %s as a key\n", keystr));
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goto fail;
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}
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if (!gencache_init()) {
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goto fail;
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}
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databuf = tdb_fetch_bystring(cache_notrans, keystr);
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if (databuf.dptr == NULL) {
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databuf = tdb_fetch_bystring(cache, keystr);
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}
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if (databuf.dptr == NULL) {
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DEBUG(10, ("Cache entry with key = %s couldn't be found \n",
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keystr));
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goto fail;
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}
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if (!gencache_pull_timeout((char *)databuf.dptr, &t, &endptr)) {
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SAFE_FREE(databuf.dptr);
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goto fail;
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}
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DEBUG(10, ("Returning %s cache entry: key = %s, value = %s, "
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"timeout = %s", t > time(NULL) ? "valid" :
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"expired", keystr, endptr+1, ctime(&t)));
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if (t == 0) {
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/* Deleted */
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SAFE_FREE(databuf.dptr);
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goto fail;
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}
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if (t <= time(NULL)) {
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/*
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* We're expired, delete the entry. We can't use gencache_del
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* here, because that uses gencache_get_data_blob for checking
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* the existence of a record. We know the thing exists and
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* directly store an empty value with 0 timeout.
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*/
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gencache_set(keystr, "", 0);
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SAFE_FREE(databuf.dptr);
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expired = true;
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goto fail;
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}
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if (blob != NULL) {
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*blob = data_blob(
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endptr+1,
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databuf.dsize - PTR_DIFF(endptr+1, databuf.dptr));
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if (blob->data == NULL) {
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SAFE_FREE(databuf.dptr);
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DEBUG(0, ("memdup failed\n"));
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goto fail;
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}
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}
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SAFE_FREE(databuf.dptr);
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if (timeout) {
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*timeout = t;
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}
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return True;
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fail:
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if (was_expired != NULL) {
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*was_expired = expired;
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}
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return false;
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}
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struct stabilize_state {
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bool written;
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bool error;
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};
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static int stabilize_fn(struct tdb_context *tdb, TDB_DATA key, TDB_DATA val,
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void *priv);
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/**
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* Stabilize gencache
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*
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* Migrate the clear-if-first gencache data to the stable,
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* transaction-based gencache.tdb
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*/
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bool gencache_stabilize(void)
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{
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struct stabilize_state state;
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int res;
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char *now;
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if (!gencache_init()) {
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return false;
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}
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res = tdb_transaction_start_nonblock(cache);
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if (res == -1) {
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if (tdb_error(cache) == TDB_ERR_NOLOCK) {
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/*
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* Someone else already does the stabilize,
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* this does not have to be done twice
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*/
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return true;
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}
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DEBUG(10, ("Could not start transaction on gencache.tdb: "
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"%s\n", tdb_errorstr(cache)));
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return false;
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}
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res = tdb_transaction_start(cache_notrans);
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if (res == -1) {
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tdb_transaction_cancel(cache);
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DEBUG(10, ("Could not start transaction on "
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"gencache_notrans.tdb: %s\n",
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tdb_errorstr(cache_notrans)));
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return false;
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}
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state.error = false;
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state.written = false;
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res = tdb_traverse(cache_notrans, stabilize_fn, &state);
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if ((res == -1) || state.error) {
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if ((tdb_transaction_cancel(cache_notrans) == -1)
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|| (tdb_transaction_cancel(cache) == -1)) {
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smb_panic("tdb_transaction_cancel failed\n");
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}
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return false;
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}
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if (!state.written) {
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if ((tdb_transaction_cancel(cache_notrans) == -1)
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|| (tdb_transaction_cancel(cache) == -1)) {
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smb_panic("tdb_transaction_cancel failed\n");
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}
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return true;
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}
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res = tdb_transaction_commit(cache);
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if (res == -1) {
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DEBUG(10, ("tdb_transaction_commit on gencache.tdb failed: "
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"%s\n", tdb_errorstr(cache)));
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if (tdb_transaction_cancel(cache_notrans) == -1) {
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smb_panic("tdb_transaction_cancel failed\n");
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}
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return false;
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}
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res = tdb_transaction_commit(cache_notrans);
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if (res == -1) {
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DEBUG(10, ("tdb_transaction_commit on gencache.tdb failed: "
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"%s\n", tdb_errorstr(cache)));
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return false;
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}
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now = talloc_asprintf(talloc_tos(), "%d", (int)time(NULL));
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if (now != NULL) {
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tdb_store(cache_notrans, last_stabilize_key(),
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string_term_tdb_data(now), 0);
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TALLOC_FREE(now);
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}
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return true;
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}
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static int stabilize_fn(struct tdb_context *tdb, TDB_DATA key, TDB_DATA val,
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void *priv)
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{
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struct stabilize_state *state = (struct stabilize_state *)priv;
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int res;
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time_t timeout;
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if (tdb_data_cmp(key, last_stabilize_key()) == 0) {
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return 0;
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}
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if (!gencache_pull_timeout((char *)val.dptr, &timeout, NULL)) {
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DEBUG(10, ("Ignoring invalid entry\n"));
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return 0;
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}
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if ((timeout < time(NULL)) || (val.dsize == 0)) {
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res = tdb_delete(cache, key);
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if ((res == -1) && (tdb_error(cache) == TDB_ERR_NOEXIST)) {
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res = 0;
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} else {
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state->written = true;
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}
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} else {
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res = tdb_store(cache, key, val, 0);
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if (res == 0) {
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state->written = true;
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}
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}
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if (res == -1) {
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DEBUG(10, ("Transfer to gencache.tdb failed: %s\n",
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tdb_errorstr(cache)));
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state->error = true;
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return -1;
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}
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if (tdb_delete(cache_notrans, key) == -1) {
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DEBUG(10, ("tdb_delete from gencache_notrans.tdb failed: "
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"%s\n", tdb_errorstr(cache_notrans)));
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state->error = true;
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return -1;
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}
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return 0;
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}
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/**
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* Get existing entry from the cache file.
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*
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* @param keystr string that represents a key of this entry
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* @param valstr buffer that is allocated and filled with the entry value
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* buffer's disposing must be done outside
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* @param timeout pointer to a time_t that is filled with entry's
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* timeout
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*
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* @retval true when entry is successfuly fetched
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* @retval False for failure
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**/
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bool gencache_get(const char *keystr, char **value, time_t *ptimeout)
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{
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DATA_BLOB blob;
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bool ret = False;
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ret = gencache_get_data_blob(keystr, &blob, ptimeout, NULL);
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if (!ret) {
|
|
return false;
|
|
}
|
|
if ((blob.data == NULL) || (blob.length == 0)) {
|
|
SAFE_FREE(blob.data);
|
|
return false;
|
|
}
|
|
if (blob.data[blob.length-1] != '\0') {
|
|
/* Not NULL terminated, can't be a string */
|
|
SAFE_FREE(blob.data);
|
|
return false;
|
|
}
|
|
if (value) {
|
|
*value = SMB_STRDUP((char *)blob.data);
|
|
data_blob_free(&blob);
|
|
if (*value == NULL) {
|
|
return false;
|
|
}
|
|
return true;
|
|
}
|
|
data_blob_free(&blob);
|
|
return true;
|
|
}
|
|
|
|
/**
|
|
* Set an entry in the cache file. If there's no such
|
|
* one, then add it.
|
|
*
|
|
* @param keystr string that represents a key of this entry
|
|
* @param value text representation value being cached
|
|
* @param timeout time when the value is expired
|
|
*
|
|
* @retval true when entry is successfuly stored
|
|
* @retval false on failure
|
|
**/
|
|
|
|
bool gencache_set(const char *keystr, const char *value, time_t timeout)
|
|
{
|
|
DATA_BLOB blob = data_blob_const(value, strlen(value)+1);
|
|
return gencache_set_data_blob(keystr, &blob, timeout);
|
|
}
|
|
|
|
/**
|
|
* Iterate through all entries which key matches to specified pattern
|
|
*
|
|
* @param fn pointer to the function that will be supplied with each single
|
|
* matching cache entry (key, value and timeout) as an arguments
|
|
* @param data void pointer to an arbitrary data that is passed directly to the fn
|
|
* function on each call
|
|
* @param keystr_pattern pattern the existing entries' keys are matched to
|
|
*
|
|
**/
|
|
|
|
struct gencache_iterate_state {
|
|
void (*fn)(const char *key, const char *value, time_t timeout,
|
|
void *priv);
|
|
const char *pattern;
|
|
void *priv;
|
|
bool in_persistent;
|
|
};
|
|
|
|
static int gencache_iterate_fn(struct tdb_context *tdb, TDB_DATA key,
|
|
TDB_DATA value, void *priv)
|
|
{
|
|
struct gencache_iterate_state *state =
|
|
(struct gencache_iterate_state *)priv;
|
|
char *keystr;
|
|
char *free_key = NULL;
|
|
char *valstr;
|
|
char *free_val = NULL;
|
|
unsigned long u;
|
|
time_t timeout;
|
|
char *timeout_endp;
|
|
|
|
if (tdb_data_cmp(key, last_stabilize_key()) == 0) {
|
|
return 0;
|
|
}
|
|
|
|
if (state->in_persistent && tdb_exists(cache_notrans, key)) {
|
|
return 0;
|
|
}
|
|
|
|
if (key.dptr[key.dsize-1] == '\0') {
|
|
keystr = (char *)key.dptr;
|
|
} else {
|
|
/* ensure 0-termination */
|
|
keystr = SMB_STRNDUP((char *)key.dptr, key.dsize);
|
|
free_key = keystr;
|
|
}
|
|
|
|
if ((value.dptr == NULL) || (value.dsize <= TIMEOUT_LEN)) {
|
|
goto done;
|
|
}
|
|
|
|
if (fnmatch(state->pattern, keystr, 0) != 0) {
|
|
goto done;
|
|
}
|
|
|
|
if (value.dptr[value.dsize-1] == '\0') {
|
|
valstr = (char *)value.dptr;
|
|
} else {
|
|
/* ensure 0-termination */
|
|
valstr = SMB_STRNDUP((char *)value.dptr, value.dsize);
|
|
free_val = valstr;
|
|
}
|
|
|
|
u = strtoul(valstr, &timeout_endp, 10);
|
|
|
|
if ((*timeout_endp != '/') || ((timeout_endp-valstr) != TIMEOUT_LEN)) {
|
|
goto done;
|
|
}
|
|
|
|
timeout = u;
|
|
timeout_endp += 1;
|
|
|
|
DEBUG(10, ("Calling function with arguments "
|
|
"(key = %s, value = %s, timeout = %s)\n",
|
|
keystr, timeout_endp, ctime(&timeout)));
|
|
state->fn(keystr, timeout_endp, timeout, state->priv);
|
|
|
|
done:
|
|
SAFE_FREE(free_key);
|
|
SAFE_FREE(free_val);
|
|
return 0;
|
|
}
|
|
|
|
void gencache_iterate(void (*fn)(const char* key, const char *value, time_t timeout, void* dptr),
|
|
void* data, const char* keystr_pattern)
|
|
{
|
|
struct gencache_iterate_state state;
|
|
|
|
if ((fn == NULL) || (keystr_pattern == NULL)) {
|
|
return;
|
|
}
|
|
|
|
if (!gencache_init()) return;
|
|
|
|
DEBUG(5, ("Searching cache keys with pattern %s\n", keystr_pattern));
|
|
|
|
state.fn = fn;
|
|
state.pattern = keystr_pattern;
|
|
state.priv = data;
|
|
|
|
state.in_persistent = false;
|
|
tdb_traverse(cache_notrans, gencache_iterate_fn, &state);
|
|
|
|
state.in_persistent = true;
|
|
tdb_traverse(cache, gencache_iterate_fn, &state);
|
|
}
|