cmd/nscd/cache.c

	cache.c revision ad0e80f7538b612141768bfda60009eb76550ee7
/*
 * CDDL HEADER START
 *
 * The contents of this file are subject to the terms of the
 * Common Development and Distribution License (the "License").
 * You may not use this file except in compliance with the License.
 *
 * You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE
 * or http://www.opensolaris.org/os/licensing.
 * See the License for the specific language governing permissions
 * and limitations under the License.
 *
 * When distributing Covered Code, include this CDDL HEADER in each
 * file and include the License file at usr/src/OPENSOLARIS.LICENSE.
 * If applicable, add the following below this CDDL HEADER, with the
 * fields enclosed by brackets "[]" replaced with your own identifying
 * information: Portions Copyright [yyyy] [name of copyright owner]
 *
 * CDDL HEADER END
 */
/*
 * Copyright 2006 Sun Microsystems, Inc.  All rights reserved.
 * Use is subject to license terms.
 */

#pragma ident   "%Z%%M% %I% %E% SMI"

/*
 * Cache routines for nscd
 */
#include <assert.h>
#include <errno.h>
#include <memory.h>
#include <signal.h>
#include <stdlib.h>
#include <stddef.h>
#include <stdio.h>
#include <string.h>
#include <sys/stat.h>
#include <sys/time.h>
#include <sys/types.h>
#include <sys/wait.h>
#include <unistd.h>
#include <ucred.h>
#include <nss_common.h>
#include <locale.h>
#include <ctype.h>
#include <strings.h>
#include <string.h>
#include <umem.h>
#include <fcntl.h>
#include "cache.h"
#include "nscd_door.h"
#include "nscd_log.h"
#include "nscd_config.h"
#include "nscd_frontend.h"
#include "nscd_switch.h"

#define SUCCESS     0
#define NOTFOUND    -1
#define SERVERERROR -2
#define NOSERVER    -3
#define CONTINUE    -4

static nsc_db_t *nsc_get_db(nsc_ctx_t *, int);
static nscd_rc_t lookup_cache(nsc_lookup_args_t *, nscd_cfg_cache_t *,
        nss_XbyY_args_t *, char *, nsc_entry_t **);
static uint_t reap_cache(nsc_ctx_t *, uint_t, uint_t);
static void delete_entry(nsc_db_t *, nsc_ctx_t *, nsc_entry_t *);
static void print_stats(nscd_cfg_stat_cache_t *);
static void print_cfg(nscd_cfg_cache_t *);
static int lookup_int(nsc_lookup_args_t *, int);

#ifdef  NSCD_DEBUG
static void print_entry(nsc_db_t *, time_t, nsc_entry_t *);
static void avl_dump(nsc_db_t *, time_t);
static void hash_dump(nsc_db_t *, time_t);
#endif  /* NSCD_DEBUG */
static nsc_entry_t *hash_find(nsc_db_t *, nsc_entry_t *, uint_t *, nscd_bool_t);

static void queue_adjust(nsc_db_t *, nsc_entry_t *);
static void queue_remove(nsc_db_t *, nsc_entry_t *);
#ifdef  NSCD_DEBUG
static void queue_dump(nsc_db_t *, time_t);
#endif  /* NSCD_DEBUG */

static int launch_update(nsc_lookup_args_t *);
static void do_update(nsc_lookup_args_t *);
static void getxy_keepalive(nsc_ctx_t *, nsc_db_t *, int, int);

static void ctx_info(nsc_ctx_t *);
static void ctx_info_nolock(nsc_ctx_t *);
static void ctx_invalidate(nsc_ctx_t *);

static void nsc_db_str_key_getlogstr(char *, char *, size_t, nss_XbyY_args_t *);
static void nsc_db_int_key_getlogstr(char *, char *, size_t, nss_XbyY_args_t *);
static void nsc_db_any_key_getlogstr(char *, char *, size_t, nss_XbyY_args_t *);

static int nsc_db_cis_key_compar(const void *, const void *);
static int nsc_db_ces_key_compar(const void *, const void *);
static int nsc_db_int_key_compar(const void *, const void *);

static uint_t nsc_db_cis_key_gethash(nss_XbyY_key_t *, int);
static uint_t nsc_db_ces_key_gethash(nss_XbyY_key_t *, int);
static uint_t nsc_db_int_key_gethash(nss_XbyY_key_t *, int);

static umem_cache_t *nsc_entry_cache;

static nsc_ctx_t *init_cache_ctx(int);
static void reaper(nsc_ctx_t *);
static void revalidate(nsc_ctx_t *);

static nss_status_t
dup_packed_buffer(void *src, void *dst) {
    nsc_lookup_args_t   *s = (nsc_lookup_args_t *)src;
    nsc_entry_t     *d = (nsc_entry_t *)dst;
    nss_pheader_t       *sphdr = (nss_pheader_t *)s->buffer;
    nss_pheader_t       *dphdr = (nss_pheader_t *)d->buffer;
    int         slen, new_pbufsiz = 0;

    if (NSCD_GET_STATUS(sphdr) != NSS_SUCCESS) {

        /* no result, copy header only (status, errno, etc) */
        slen = sphdr->data_off;
    } else {
        /*
         * lookup result returned, data to copy is the packed
         * header plus result (add 1 for the terminating NULL
         * just in case)
         */
        slen = sphdr->data_off + sphdr->data_len + 1;
    }

    /* allocate cache packed buffer */
    if (dphdr != NULL && d->bufsize <= slen && d->bufsize != 0) {
        /* old buffer too small, free it */
        free(dphdr);
        d->buffer = NULL;
        d->bufsize = 0;
        dphdr = NULL;
    }
    if (dphdr == NULL) {
        /* get new buffer */
        dphdr = calloc(1, slen + 1);
        if (dphdr == NULL)
            return (NSS_ERROR);
        d->buffer = dphdr;
        d->bufsize = slen + 1;
        new_pbufsiz = slen + 1;
    }

    (void) memcpy(dphdr, sphdr, slen);
    if (new_pbufsiz != 0)
        dphdr->pbufsiz = new_pbufsiz;

    return (NSS_SUCCESS);
}

char *cache_name[CACHE_CTX_COUNT] = {
    NSS_DBNAM_PASSWD,
    NSS_DBNAM_GROUP,
    NSS_DBNAM_HOSTS,
    NSS_DBNAM_IPNODES,
    NSS_DBNAM_EXECATTR,
    NSS_DBNAM_PROFATTR,
    NSS_DBNAM_USERATTR,
    NSS_DBNAM_ETHERS,
    NSS_DBNAM_RPC,
    NSS_DBNAM_PROTOCOLS,
    NSS_DBNAM_NETWORKS,
    NSS_DBNAM_BOOTPARAMS,
    NSS_DBNAM_AUDITUSER,
    NSS_DBNAM_AUTHATTR,
    NSS_DBNAM_SERVICES,
    NSS_DBNAM_NETMASKS,
    NSS_DBNAM_PRINTERS,
    NSS_DBNAM_PROJECT,
    NSS_DBNAM_TSOL_TP,
    NSS_DBNAM_TSOL_RH
};

typedef void (*cache_init_ctx_t)(nsc_ctx_t *);
static cache_init_ctx_t cache_init_ctx[CACHE_CTX_COUNT] = {
    passwd_init_ctx,
    group_init_ctx,
    host_init_ctx,
    ipnode_init_ctx,
    exec_init_ctx,
    prof_init_ctx,
    user_init_ctx,
    ether_init_ctx,
    rpc_init_ctx,
    proto_init_ctx,
    net_init_ctx,
    bootp_init_ctx,
    auuser_init_ctx,
    auth_init_ctx,
    serv_init_ctx,
    netmask_init_ctx,
    printer_init_ctx,
    project_init_ctx,
    tnrhtp_init_ctx,
    tnrhdb_init_ctx
};

nsc_ctx_t *cache_ctx_p[CACHE_CTX_COUNT] = { 0 };
static nscd_cfg_stat_cache_t    null_stats = { 0 };
static nscd_cfg_global_cache_t  global_cfg;

/*
 * Given database name 'dbname' find cache index
 */
int
get_cache_idx(char *dbname) {
    int i;
    char    *nsc_name;

    for (i = 0; i < CACHE_CTX_COUNT; i++) {
        nsc_name = cache_name[i];
        if (strcmp(nsc_name, dbname) == 0)
            return (i);
    }
    return (-1);
}

/*
 * Given database name 'dbname' retrieve cache context,
 * if not created yet, allocate and initialize it.
 */
static nscd_rc_t
get_cache_ctx(char *dbname, nsc_ctx_t **ctx) {
    int i;

    *ctx = NULL;

    i = get_cache_idx(dbname);
    if (i == -1)
        return (NSCD_INVALID_ARGUMENT);
    if ((*ctx = cache_ctx_p[i]) == NULL) {
        *ctx = init_cache_ctx(i);
        if (*ctx == NULL)
            return (NSCD_NO_MEMORY);
    }

    return (NSCD_SUCCESS);
}

/*
 * Generate a log string to identify backend operation in debug logs
 */
static void
nsc_db_str_key_getlogstr(char *name, char *whoami, size_t len,
        nss_XbyY_args_t *argp) {
    (void) snprintf(whoami, len, "%s [key=%s]", name, argp->key.name);
}


static void
nsc_db_int_key_getlogstr(char *name, char *whoami, size_t len,
        nss_XbyY_args_t *argp) {
    (void) snprintf(whoami, len, "%s [key=%d]", name, argp->key.number);
}

/*ARGSUSED*/
static void
nsc_db_any_key_getlogstr(char *name, char *whoami, size_t len,
        nss_XbyY_args_t *argp) {
    (void) snprintf(whoami, len, "%s", name);
}


/*
 * Returns cache based on dbop
 */
static nsc_db_t *
nsc_get_db(nsc_ctx_t *ctx, int dbop) {
    int i;

    for (i = 0; i < ctx->db_count; i++) {
        if (ctx->nsc_db[i] && dbop == ctx->nsc_db[i]->dbop)
            return (ctx->nsc_db[i]);
    }
    return (NULL);
}


/*
 * integer compare routine for _NSC_DB_INT_KEY
 */
static int
nsc_db_int_key_compar(const void *n1, const void *n2) {
    nsc_entry_t *e1, *e2;

    e1 = (nsc_entry_t *)n1;
    e2 = (nsc_entry_t *)n2;
    return (_NSC_INT_KEY_CMP(e1->key.number, e2->key.number));
}


/*
 * case sensitive name compare routine for _NSC_DB_CES_KEY
 */
static int
nsc_db_ces_key_compar(const void *n1, const void *n2) {
    nsc_entry_t *e1, *e2;
    int     res, l1, l2;

    e1 = (nsc_entry_t *)n1;
    e2 = (nsc_entry_t *)n2;
    l1 = strlen(e1->key.name);
    l2 = strlen(e2->key.name);
    res = strncmp(e1->key.name, e2->key.name, (l1 > l2)?l1:l2);
    return (_NSC_INT_KEY_CMP(res, 0));
}


/*
 * case insensitive name compare routine _NSC_DB_CIS_KEY
 */
static int
nsc_db_cis_key_compar(const void *n1, const void *n2) {
    nsc_entry_t *e1, *e2;
    int     res, l1, l2;

    e1 = (nsc_entry_t *)n1;
    e2 = (nsc_entry_t *)n2;
    l1 = strlen(e1->key.name);
    l2 = strlen(e2->key.name);
    res = strncasecmp(e1->key.name, e2->key.name, (l1 > l2)?l1:l2);
    return (_NSC_INT_KEY_CMP(res, 0));
}

/*
 * macro used to generate elf hashes for strings
 */
#define _NSC_ELF_STR_GETHASH(func, str, htsize, hval) \
    hval = 0; \
    while (*str) { \
        uint_t  g; \
        hval = (hval << 4) + func(*str++); \
        if ((g = (hval & 0xf0000000)) != 0) \
            hval ^= g >> 24; \
        hval &= ~g; \
    } \
    hval %= htsize;


/*
 * cis hash function
 */
uint_t
cis_gethash(const char *key, int htsize) {
    uint_t  hval;
    if (key == NULL)
        return (0);
    _NSC_ELF_STR_GETHASH(tolower, key, htsize, hval);
    return (hval);
}


/*
 * ces hash function
 */
uint_t
ces_gethash(const char *key, int htsize) {
    uint_t  hval;
    if (key == NULL)
        return (0);
    _NSC_ELF_STR_GETHASH(, key, htsize, hval);
    return (hval);
}


/*
 * one-at-a-time hash function
 */
uint_t
db_gethash(const void *key, int len, int htsize) {
    uint_t  hval, i;
    const char *str = key;

    if (str == NULL)
        return (0);

    for (hval = 0, i = 0; i < len; i++) {
        hval += str[i];
        hval += (hval << 10);
        hval ^= (hval >> 6);
    }
    hval += (hval << 3);
    hval ^= (hval >> 11);
    hval += (hval << 15);
    return (hval % htsize);
}


/*
 * case insensitive name gethash routine _NSC_DB_CIS_KEY
 */
static uint_t
nsc_db_cis_key_gethash(nss_XbyY_key_t *key, int htsize) {
    return (cis_gethash(key->name, htsize));
}


/*
 * case sensitive name gethash routine _NSC_DB_CES_KEY
 */
static uint_t
nsc_db_ces_key_gethash(nss_XbyY_key_t *key, int htsize) {
    return (ces_gethash(key->name, htsize));
}


/*
 * integer gethash routine _NSC_DB_INT_KEY
 */
static uint_t
nsc_db_int_key_gethash(nss_XbyY_key_t *key, int htsize) {
    return (db_gethash(&key->number, sizeof (key->number), htsize));
}


/*
 * Find entry in the hash table
 * if cmp == nscd_true)
 *  return entry only if the keys match
 * else
 *  return entry in the hash location without checking the keys
 *
 */
static nsc_entry_t *
hash_find(nsc_db_t *nscdb, nsc_entry_t *entry, uint_t *hash,
            nscd_bool_t cmp) {

    nsc_entry_t *hashentry;

    if (nscdb->gethash)
        *hash = nscdb->gethash(&entry->key, nscdb->htsize);
    else
        return (NULL);

    hashentry = nscdb->htable[*hash];
    if (cmp == nscd_false || hashentry == NULL)
        return (hashentry);
    if (nscdb->compar) {
        if (nscdb->compar(entry, hashentry) == 0)
            return (hashentry);
    }
    return (NULL);
}


#define HASH_REMOVE(nscdb, entry, hash, cmp) \
    if (nscdb->htable) { \
        if (entry == hash_find(nscdb, entry, &hash, cmp)) \
            nscdb->htable[hash] = NULL; \
    }


#define HASH_INSERT(nscdb, entry, hash, cmp) \
    if (nscdb->htable) { \
        (void) hash_find(nscdb, entry, &hash, cmp); \
        nscdb->htable[hash] = entry; \
    }


#ifdef  NSCD_DEBUG
static void
print_entry(nsc_db_t *nscdb, time_t now, nsc_entry_t *entry) {
    nss_XbyY_args_t args;
    char        whoami[512];

    switch (entry->stats.status) {
    case ST_NEW_ENTRY:
        (void) fprintf(stdout, gettext("\t status: new entry\n"));
        return;
    case ST_UPDATE_PENDING:
        (void) fprintf(stdout, gettext("\t status: update pending\n"));
        return;
    case ST_LOOKUP_PENDING:
        (void) fprintf(stdout, gettext("\t status: lookup pending\n"));
        return;
    case ST_DISCARD:
        (void) fprintf(stdout, gettext("\t status: discarded entry\n"));
        return;
    default:
        if (entry->stats.timestamp < now)
            (void) fprintf(stdout,
            gettext("\t status: expired (%d seconds ago)\n"),
            now - entry->stats.timestamp);
        else
            (void) fprintf(stdout,
            gettext("\t status: valid (expiry in %d seconds)\n"),
            entry->stats.timestamp - now);
        break;
    }
    (void) fprintf(stdout, gettext("\t hits: %u\n"), entry->stats.hits);
    args.key = entry->key;
    (void) nscdb->getlogstr(nscdb->name, whoami, sizeof (whoami), &args);
    (void) fprintf(stdout, "\t %s\n", whoami);
}
#endif  /* NSCD_DEBUG */

static void
print_stats(nscd_cfg_stat_cache_t *statsp) {

    (void) fprintf(stdout, gettext("\n\t STATISTICS:\n"));
    (void) fprintf(stdout, gettext("\t positive hits: %lu\n"),
            statsp->pos_hits);
    (void) fprintf(stdout, gettext("\t negative hits: %lu\n"),
            statsp->neg_hits);
    (void) fprintf(stdout, gettext("\t positive misses: %lu\n"),
            statsp->pos_misses);
    (void) fprintf(stdout, gettext("\t negative misses: %lu\n"),
            statsp->neg_misses);
    (void) fprintf(stdout, gettext("\t total entries: %lu\n"),
            statsp->entries);
    (void) fprintf(stdout, gettext("\t queries queued: %lu\n"),
            statsp->wait_count);
    (void) fprintf(stdout, gettext("\t queries dropped: %lu\n"),
            statsp->drop_count);
    (void) fprintf(stdout, gettext("\t cache invalidations: %lu\n"),
            statsp->invalidate_count);

    _NSC_GET_HITRATE(statsp);
    (void) fprintf(stdout, gettext("\t cache hit rate: %10.1f\n"),
            statsp->hitrate);
}


static void
print_cfg(nscd_cfg_cache_t *cfgp) {
    (void) fprintf(stdout, gettext("\n\t CONFIG:\n"));
    (void) fprintf(stdout, gettext("\t enabled: %s\n"),
            yes_no(cfgp->enable));
    (void) fprintf(stdout, gettext("\t per user cache: %s\n"),
            yes_no(cfgp->per_user));
    (void) fprintf(stdout, gettext("\t avoid name service: %s\n"),
            yes_no(cfgp->avoid_ns));
    (void) fprintf(stdout, gettext("\t check file: %s\n"),
            yes_no(cfgp->check_files));
    (void) fprintf(stdout, gettext("\t check file interval: %d\n"),
            cfgp->check_interval);
    (void) fprintf(stdout, gettext("\t positive ttl: %d\n"),
            cfgp->pos_ttl);
    (void) fprintf(stdout, gettext("\t negative ttl: %d\n"),
            cfgp->neg_ttl);
    (void) fprintf(stdout, gettext("\t keep hot count: %d\n"),
            cfgp->keephot);
    (void) fprintf(stdout, gettext("\t hint size: %d\n"),
            cfgp->hint_size);
    (void) fprintf(stdout, gettext("\t max entries: %lu%s"),
            cfgp->maxentries,
            cfgp->maxentries?"\n":" (unlimited)\n");
}


#ifdef  NSCD_DEBUG
static void
hash_dump(nsc_db_t *nscdb, time_t now) {
    nsc_entry_t *entry;
    int     i;

    (void) fprintf(stdout, gettext("\n\nHASH TABLE:\n"));
    for (i = 0; i < nscdb->htsize; i++) {
        if ((entry = nscdb->htable[i]) != NULL) {
            (void) fprintf(stdout, "hash[%d]:\n", i);
            print_entry(nscdb, now, entry);
        }
    }
}
#endif  /* NSCD_DEBUG */


#ifdef  NSCD_DEBUG
static void
avl_dump(nsc_db_t *nscdb, time_t now) {
    nsc_entry_t *entry;
    int     i;

    (void) fprintf(stdout, gettext("\n\nAVL TREE:\n"));
    for (entry = avl_first(&nscdb->tree), i = 0; entry != NULL;
            entry = avl_walk(&nscdb->tree, entry, AVL_AFTER)) {
        (void) fprintf(stdout, "avl node[%d]:\n", i++);
        print_entry(nscdb, now, entry);
    }
}
#endif  /* NSCD_DEBUG */


#ifdef  NSCD_DEBUG
static void
queue_dump(nsc_db_t *nscdb, time_t now) {
    nsc_entry_t *entry;
    int     i;

    (void) fprintf(stdout,
        gettext("\n\nCACHE [name=%s, nodes=%lu]:\n"),
        nscdb->name, avl_numnodes(&nscdb->tree));

    (void) fprintf(stdout,
        gettext("Starting with the most recently accessed:\n"));

    for (entry = nscdb->qtail, i = 0; entry; entry = entry->qnext) {
        (void) fprintf(stdout, "entry[%d]:\n", i++);
        print_entry(nscdb, now, entry);
    }
}
#endif  /* NSCD_DEBUG */

static void
queue_remove(nsc_db_t *nscdb, nsc_entry_t *entry) {

    if (nscdb->qtail == entry)
        nscdb->qtail = entry->qnext;
    else
        entry->qprev->qnext = entry->qnext;

    if (nscdb->qhead == entry)
        nscdb->qhead = entry->qprev;
    else
        entry->qnext->qprev = entry->qprev;

    if (nscdb->reap_node == entry)
        nscdb->reap_node = entry->qnext;
    entry->qnext = entry->qprev = NULL;
}


static void
queue_adjust(nsc_db_t *nscdb, nsc_entry_t *entry) {

#ifdef NSCD_DEBUG
    assert(nscdb->qtail || entry->qnext == NULL &&
            entry->qprev == NULL);

    assert(nscdb->qtail && nscdb->qhead ||
        nscdb->qtail == NULL && nscdb->qhead == NULL);

    assert(entry->qprev || entry->qnext == NULL ||
        nscdb->qtail == entry);
#endif /* NSCD_DEBUG */

    /* already in the desired position */
    if (nscdb->qtail == entry)
        return;

    /* new queue */
    if (nscdb->qtail == NULL) {
        nscdb->qhead = nscdb->qtail = entry;
        return;
    }

    /* new entry (prev == NULL AND tail != entry) */
    if (entry->qprev == NULL) {
        nscdb->qtail->qprev = entry;
        entry->qnext = nscdb->qtail;
        nscdb->qtail = entry;
        return;
    }

    /* existing entry */
    if (nscdb->reap_node == entry)
        nscdb->reap_node = entry->qnext;
    if (nscdb->qhead == entry)
        nscdb->qhead = entry->qprev;
    else
        entry->qnext->qprev = entry->qprev;
    entry->qprev->qnext = entry->qnext;
    entry->qprev = NULL;
    entry->qnext = nscdb->qtail;
    nscdb->qtail->qprev = entry;
    nscdb->qtail = entry;
}


/*
 * Init cache
 */
nscd_rc_t
init_cache(int debug_level) {
    int cflags;

    cflags = (debug_level > 0)?0:UMC_NODEBUG;
    nsc_entry_cache = umem_cache_create("nsc_entry_cache",
                sizeof (nsc_entry_t), 0, NULL, NULL, NULL,
                NULL, NULL, cflags);
    if (nsc_entry_cache == NULL)
        return (NSCD_NO_MEMORY);
    return (NSCD_SUCCESS);
}


/*
 * Create cache
 */
nsc_db_t *
make_cache(enum db_type dbtype, int dbop, char *name,
        int (*compar) (const void *, const void *),
        void (*getlogstr)(char *, char *, size_t, nss_XbyY_args_t *),
        uint_t (*gethash)(nss_XbyY_key_t *, int),
        enum hash_type httype, int htsize) {

    nsc_db_t    *nscdb;
    char        *me = "make_cache";

    nscdb = (nsc_db_t *)malloc(sizeof (*nscdb));
    if (nscdb == NULL) {
        _NSCD_LOG(NSCD_LOG_CACHE, NSCD_LOG_LEVEL_ERROR)
        (me, "%s: memory allocation failure\n", name);
        goto out;
    }
    (void) memset(nscdb, 0, sizeof (*nscdb));

    nscdb->dbop = dbop;
    nscdb->name = name;
    nscdb->db_type = dbtype;

    /* Assign compare routine */
    if (compar == NULL) {
        if (_NSC_DB_CES_KEY(nscdb))
            nscdb->compar = nsc_db_ces_key_compar;
        else if (_NSC_DB_CIS_KEY(nscdb))
            nscdb->compar = nsc_db_cis_key_compar;
        else if (_NSC_DB_INT_KEY(nscdb))
            nscdb->compar = nsc_db_int_key_compar;
        else
            assert(0);
    } else {
        nscdb->compar = compar;
    }

    /* The cache is an AVL tree */
    avl_create(&nscdb->tree, nscdb->compar, sizeof (nsc_entry_t),
            offsetof(nsc_entry_t, avl_link));

    /* Assign log routine */
    if (getlogstr == NULL) {
        if (_NSC_DB_STR_KEY(nscdb))
            nscdb->getlogstr = nsc_db_str_key_getlogstr;
        else if (_NSC_DB_INT_KEY(nscdb))
            nscdb->getlogstr = nsc_db_int_key_getlogstr;
        else
            nscdb->getlogstr = nsc_db_any_key_getlogstr;
    } else {
        nscdb->getlogstr = getlogstr;
    }

    /* The AVL tree based cache uses a hash table for quick access */
    if (htsize != 0) {
        /* Determine hash table size based on type */
        nscdb->hash_type = httype;
        if (htsize < 0) {
            switch (httype) {
            case nsc_ht_power2:
                htsize = _NSC_INIT_HTSIZE_POWER2;
                break;
            case nsc_ht_prime:
            case nsc_ht_default:
            default:
                htsize = _NSC_INIT_HTSIZE_PRIME;
            }
        }
        nscdb->htsize = htsize;

        /* Create the hash table */
        nscdb->htable = calloc(htsize, sizeof (*(nscdb->htable)));
        if (nscdb->htable == NULL) {
            _NSCD_LOG(NSCD_LOG_CACHE, NSCD_LOG_LEVEL_ERROR)
            (me, "%s: memory allocation failure\n", name);
            goto out;
        }

        /* Assign gethash routine */
        if (gethash == NULL) {
            if (_NSC_DB_CES_KEY(nscdb))
                nscdb->gethash = nsc_db_ces_key_gethash;
            else if (_NSC_DB_CIS_KEY(nscdb))
                nscdb->gethash = nsc_db_cis_key_gethash;
            else if (_NSC_DB_INT_KEY(nscdb))
                nscdb->gethash = nsc_db_int_key_gethash;
            else
                assert(0);
        } else {
            nscdb->gethash = gethash;
        }
    }

    (void) mutex_init(&nscdb->db_mutex, USYNC_THREAD, NULL);
    return (nscdb);

out:
    if (nscdb->htable)
        free(nscdb->htable);
    if (nscdb)
        free(nscdb);
    return (NULL);
}


/*
 * verify
 */
/* ARGSUSED */
nscd_rc_t
_nscd_cfg_cache_verify(
    void                *data,
    struct nscd_cfg_param_desc  *pdesc,
    nscd_cfg_id_t           *nswdb,
    nscd_cfg_flag_t         dflag,
    nscd_cfg_error_t        **errorp,
    void                **cookie)
{

    return (NSCD_SUCCESS);
}

/*
 * notify
 */
/* ARGSUSED */
nscd_rc_t
_nscd_cfg_cache_notify(
    void                *data,
    struct nscd_cfg_param_desc  *pdesc,
    nscd_cfg_id_t           *nswdb,
    nscd_cfg_flag_t         dflag,
    nscd_cfg_error_t        **errorp,
    void                **cookie)
{
    nsc_ctx_t   *ctx;
    void        *dp;
    int     i;

    /* group data */
    if (_nscd_cfg_flag_is_set(dflag, NSCD_CFG_DFLAG_GROUP)) {
        if (_nscd_cfg_flag_is_set(pdesc->pflag,
                NSCD_CFG_PFLAG_GLOBAL)) {
            /* global config */
            global_cfg = *(nscd_cfg_global_cache_t *)data;
        } else if (_nscd_cfg_flag_is_set(dflag,
                NSCD_CFG_DFLAG_SET_ALL_DB)) {
            /* non-global config for all dbs */
            for (i = 0; i < CACHE_CTX_COUNT; i++) {
                ctx = cache_ctx_p[i];
                if (ctx == NULL)
                    return (NSCD_CTX_NOT_FOUND);
                (void) rw_wrlock(&ctx->cfg_rwlp);
                ctx->cfg = *(nscd_cfg_cache_t *)data;
                ctx->cfg_mtime = time(NULL);
                (void) rw_unlock(&ctx->cfg_rwlp);
            }
        } else {
            /* non-global config for a specific db */

            /* ignore non-caching databases */
            if (get_cache_ctx(nswdb->name, &ctx) !=
                NSCD_SUCCESS)
                return (NSCD_SUCCESS);
            (void) rw_wrlock(&ctx->cfg_rwlp);
            ctx->cfg = *(nscd_cfg_cache_t *)data;
            ctx->cfg_mtime = time(NULL);
            (void) rw_unlock(&ctx->cfg_rwlp);
        }
        return (NSCD_SUCCESS);
    }

    /* individual data */
    if (_nscd_cfg_flag_is_set(pdesc->pflag,
                NSCD_CFG_PFLAG_GLOBAL)) {
        /* global config */
        dp = (char *)&global_cfg + pdesc->p_offset;
        (void) memcpy(dp, data, pdesc->p_size);
    } else if (_nscd_cfg_flag_is_set(dflag,
            NSCD_CFG_DFLAG_SET_ALL_DB)) {
        /* non-global config for all dbs */
        for (i = 0; i < CACHE_CTX_COUNT; i++) {
            ctx = cache_ctx_p[i];
            if (ctx == NULL)
                return (NSCD_CTX_NOT_FOUND);
            dp = (char *)&ctx->cfg + pdesc->p_offset;
            (void) rw_wrlock(&ctx->cfg_rwlp);
            (void) memcpy(dp, data, pdesc->p_size);
            ctx->cfg_mtime = time(NULL);
            (void) rw_unlock(&ctx->cfg_rwlp);
        }
    } else {
        /* non-global config for a specific db */

        /* ignore non-caching databases */
        if (get_cache_ctx(nswdb->name, &ctx) != NSCD_SUCCESS)
            return (NSCD_SUCCESS);
        dp = (char *)&ctx->cfg + pdesc->p_offset;
        (void) rw_wrlock(&ctx->cfg_rwlp);
        (void) memcpy(dp, data, pdesc->p_size);
        ctx->cfg_mtime = time(NULL);
        (void) rw_unlock(&ctx->cfg_rwlp);
    }
    return (NSCD_SUCCESS);
}


/*
 * get stat
 */
/* ARGSUSED */
nscd_rc_t
_nscd_cfg_cache_get_stat(
    void                **stat,
    struct nscd_cfg_stat_desc   *sdesc,
    nscd_cfg_id_t           *nswdb,
    nscd_cfg_flag_t         *dflag,
    void                (**free_stat)(void *stat),
    nscd_cfg_error_t        **errorp)
{
    nscd_cfg_stat_cache_t   *statsp, stats;
    nsc_ctx_t       *ctx;
    int         i;
    nscd_rc_t       rc;

    statsp = calloc(1, sizeof (*statsp));
    if (statsp == NULL)
        return (NSCD_NO_MEMORY);

    if (_nscd_cfg_flag_is_set(sdesc->sflag, NSCD_CFG_SFLAG_GLOBAL)) {
        for (i = 0; i < CACHE_CTX_COUNT; i++) {
            if (cache_ctx_p[i] == NULL)
                stats = null_stats;
            else {
                (void) mutex_lock(&cache_ctx_p[i]->stats_mutex);
                stats = cache_ctx_p[i]->stats;
                (void) mutex_unlock(
                    &cache_ctx_p[i]->stats_mutex);
            }
            statsp->pos_hits += stats.pos_hits;
            statsp->neg_hits += stats.neg_hits;
            statsp->pos_misses += stats.pos_misses;
            statsp->neg_misses += stats.neg_misses;
            statsp->entries += stats.entries;
            statsp->drop_count += stats.drop_count;
            statsp->wait_count += stats.wait_count;
            statsp->invalidate_count +=
                stats.invalidate_count;
        }
    } else {
        if ((rc = get_cache_ctx(nswdb->name, &ctx)) != NSCD_SUCCESS) {
            free(statsp);
            return (rc);
        }
        (void) mutex_lock(&ctx->stats_mutex);
        *statsp = ctx->stats;
        (void) mutex_unlock(&ctx->stats_mutex);
    }

    _NSC_GET_HITRATE(statsp);
    *stat = statsp;
    return (NSCD_SUCCESS);
}

/*
 * This function should only be called when nscd is
 * not a daemon.
 */
void
nsc_info(nsc_ctx_t *ctx, char *dbname, nscd_cfg_cache_t cfg[],
    nscd_cfg_stat_cache_t stats[])
{
    int     i;
    char        *me = "nsc_info";
    nsc_ctx_t   *ctx1;
    nsc_ctx_t   ctx2;
    nscd_rc_t   rc;

    if (ctx) {
        ctx_info(ctx);
        return;
    }

    if (dbname) {
        rc = get_cache_ctx(dbname, &ctx1);
        if (rc == NSCD_INVALID_ARGUMENT) {
            _NSCD_LOG(NSCD_LOG_CACHE, NSCD_LOG_LEVEL_WARNING)
            (me, "%s: no cache context found\n", dbname);
            return;
        } else if (rc == NSCD_NO_MEMORY) {
            _NSCD_LOG(NSCD_LOG_CACHE, NSCD_LOG_LEVEL_WARNING)
    (me, "%s: unable to create cache context - no memory\n",
                dbname);
            return;
        }
        ctx_info(ctx1);
        return;
    }

    if (cfg == NULL || stats == NULL)
        return;

    for (i = 0; i < CACHE_CTX_COUNT; i++) {

        ctx2.dbname = cache_name[i];
        ctx2.cfg = cfg[i];
        ctx2.stats = stats[i];
        ctx_info_nolock(&ctx2);
    }
}

static void
ctx_info_nolock(nsc_ctx_t *ctx) {
    nscd_cfg_cache_t    cfg;
    nscd_cfg_stat_cache_t   stats;

    cfg = ctx->cfg;
    (void) fprintf(stdout, gettext("\n\nCACHE: %s\n"), ctx->dbname);
    (void) print_cfg(&cfg);

    if (cfg.enable == nscd_false)
        return;

    stats = ctx->stats;
    (void) print_stats(&stats);
}

static void
ctx_info(nsc_ctx_t *ctx) {
    nscd_cfg_cache_t    cfg;
    nscd_cfg_stat_cache_t   stats;

    (void) rw_rdlock(&ctx->cfg_rwlp);
    cfg = ctx->cfg;
    (void) rw_unlock(&ctx->cfg_rwlp);
    (void) fprintf(stdout, gettext("\n\nCACHE: %s\n"), ctx->dbname);
    (void) print_cfg(&cfg);

    if (cfg.enable == nscd_false)
        return;

    (void) mutex_lock(&ctx->stats_mutex);
    stats = ctx->stats;
    (void) mutex_unlock(&ctx->stats_mutex);
    (void) print_stats(&stats);
}

#ifdef  NSCD_DEBUG
/*
 * This function should only be called when nscd is
 * not a daemon.
 */
int
nsc_dump(char *dbname, int dbop) {
    nsc_ctx_t   *ctx;
    nsc_db_t    *nscdb;
    nscd_bool_t enabled;
    time_t      now;
    char        *me = "nsc_dump";
    int     i;

    if ((i = get_cache_idx(dbname)) == -1) {
        (void) fprintf(stdout, gettext("invalid cache name\n"));

        _NSCD_LOG(NSCD_LOG_CACHE, NSCD_LOG_LEVEL_WARNING)
        (me, "%s: invalid cache name\n", dbname);
        return (NSCD_CACHE_INVALID_CACHE_NAME);
    }

    if ((ctx = cache_ctx_p[i]) == NULL)  {
        (void) fprintf(stdout, gettext("no cache context\n"));

        _NSCD_LOG(NSCD_LOG_CACHE, NSCD_LOG_LEVEL_WARNING)
        (me, "%s: no cache context\n", dbname);
        return (NSCD_CACHE_NO_CACHE_CTX);
    }

    now = time(NULL);
    (void) rw_rdlock(&ctx->cfg_rwlp);
    enabled = ctx->cfg.enable;
    (void) rw_unlock(&ctx->cfg_rwlp);

    if (enabled == nscd_false)
        return (NSCD_CACHE_DISABLED);

    nscdb = nsc_get_db(ctx, dbop);
    if (nscdb == NULL) {
        _NSCD_LOG(NSCD_LOG_CACHE, NSCD_LOG_LEVEL_WARNING)
        (me, "%s:%d: no cache found\n", dbname, dbop);
        return (NSCD_CACHE_NO_CACHE_FOUND);
    }

    (void) mutex_lock(&nscdb->db_mutex);
    (void) queue_dump(nscdb, now);
    (void) hash_dump(nscdb, now);
    (void) avl_dump(nscdb, now);
    (void) mutex_unlock(&nscdb->db_mutex);
    return (NSCD_SUCCESS);
}
#endif  /* NSCD_DEBUG */

/*
 * These macros are for exclusive use of nsc_lookup
 */
#define NSC_LOOKUP_RETURN(retcode, loglevel, fmt) \
    (void) mutex_unlock(&nscdb->db_mutex); \
    _NSCD_LOG(NSCD_LOG_CACHE, NSCD_LOG_LEVEL_##loglevel) \
        (me, fmt, whoami); \
    return (retcode);

#define NSC_LOOKUP_NO_CACHE(str) \
    _NSCD_LOG(NSCD_LOG_CACHE, NSCD_LOG_LEVEL_DEBUG) \
        (me, "%s: name service lookup (bypassing cache\n", \
        str); \
    nss_psearch(largs->buffer, largs->bufsize); \
    status = NSCD_GET_STATUS(largs->buffer); \
    _NSCD_LOG(NSCD_LOG_CACHE, NSCD_LOG_LEVEL_DEBUG) \
        (me, "%s: name service lookup status = %d\n", \
        str, status); \
    if (status == NSS_SUCCESS) { \
        return (SUCCESS); \
    } else if (status == NSS_NOTFOUND) \
        return (NOTFOUND); \
    else \
        return (SERVERERROR);

/*
 * This function starts the revalidation and reaper threads
 * for a cache
 */
static void
start_threads(nsc_ctx_t *ctx) {

    int errnum;
    char    *me = "start_threads";

    /*
     *  kick off the revalidate thread (if necessary)
     */
    if (ctx->revalidate_on != nscd_true) {
        if (thr_create(NULL, NULL, (void *(*)(void *))revalidate,
            ctx, 0, NULL) != 0) {
            errnum = errno;
            _NSCD_LOG(NSCD_LOG_CACHE, NSCD_LOG_LEVEL_ERROR)
        (me, "thr_create (revalidate thread for %s): %s\n",
            ctx->dbname, strerror(errnum));
            exit(1);
        }
        ctx->revalidate_on = nscd_true;
    }

    /*
     *  kick off the reaper thread (if necessary)
     */
    if (ctx->reaper_on != nscd_true) {
        if (thr_create(NULL, NULL, (void *(*)(void *))reaper,
            ctx, 0, NULL) != 0) {
            errnum = errno;
            _NSCD_LOG(NSCD_LOG_CACHE, NSCD_LOG_LEVEL_ERROR)
        (me, "thr_create (reaper thread for %s): %s\n",
            ctx->dbname, strerror(errnum));
            exit(1);
        }
        ctx->reaper_on = nscd_true;
    }
}

/*
 * Examine the packed buffer, see if the front-end parameters
 * indicate that the caller specified nsswitch config should be
 * used for the lookup. Return 1 if yes, otherwise 0.
 */
static int
nsw_config_in_phdr(void *buf)
{
    nss_pheader_t       *pbuf = (nss_pheader_t *)buf;
    nssuint_t       off;
    nss_dbd_t       *pdbd;
    char            *me = "nsw_config_in_phdr";

    off = pbuf->dbd_off;
    if (off == 0)
        return (0);
    pdbd = (nss_dbd_t *)((void *)((char *)pbuf + off));
    if (pdbd->o_default_config == 0)
        return (0);

    if ((enum nss_dbp_flags)pdbd->flags & NSS_USE_DEFAULT_CONFIG) {
        _NSCD_LOG(NSCD_LOG_CACHE, NSCD_LOG_LEVEL_DEBUG)
        (me, "use caller specified nsswitch config\n");
        return (1);
    } else
        return (0);
}

static nss_status_t
copy_result(void *rbuf, void *cbuf)
{
    nss_pheader_t   *rphdr = (nss_pheader_t *)rbuf;
    nss_pheader_t   *cphdr = (nss_pheader_t *)cbuf;
    char        *me = "copy_result";

    /* return NSS_ERROR if not enough room to copy result */
    if (cphdr->data_len + 1 > rphdr->data_len) {
        NSCD_SET_STATUS(rphdr, NSS_ERROR, ERANGE);
        return (NSS_ERROR);
    } else {
        char    *dst;

        if (cphdr->data_len == 0)
            return (NSS_SUCCESS);

        dst = (char *)rphdr + rphdr->data_off;
        (void) memcpy(dst, (char *)cphdr + cphdr->data_off,
            cphdr->data_len);
        rphdr->data_len = cphdr->data_len;
        /* some frontend code expects a terminating NULL char */
        *(dst + rphdr->data_len) = '\0';

        _NSCD_LOG(NSCD_LOG_CACHE, NSCD_LOG_LEVEL_DEBUG)
        (me, "cache data (len = %lld): %s\n",
        cphdr->data_len, (char *)cphdr + cphdr->data_off);

        return (NSS_SUCCESS);
    }
}

static int
get_dns_ttl(void *pbuf, char *dbname)
{
    nss_pheader_t   *phdr = (nss_pheader_t *)pbuf;
    int     ttl;
    char        *me = "get_dns_ttl";

    /* if returned, dns ttl is stored in the extended data area */
    if (phdr->ext_off == 0)
        return (-1);

    if (strcmp(dbname, NSS_DBNAM_HOSTS) != 0 &&
        strcmp(dbname, NSS_DBNAM_IPNODES) != 0)
        return (-1);

    ttl = *(nssuint_t *)((void *)((char *)pbuf + phdr->ext_off));

    _NSCD_LOG(NSCD_LOG_CACHE, NSCD_LOG_LEVEL_DEBUG)
    (me, "dns ttl is %d seconds\n", ttl);

    return (ttl);
}

static int
check_config(nsc_lookup_args_t *largs, nscd_cfg_cache_t *cfgp,
    char *whoami, int flag)
{
    nsc_db_t    *nscdb;
    nsc_ctx_t   *ctx;
    nss_status_t    status;
    char        *me = "check_config";

    ctx = largs->ctx;
    nscdb = largs->nscdb;

    /* see if the cached config needs update */
    if (nscdb->cfg_mtime != ctx->cfg_mtime) {
        (void) rw_rdlock(&ctx->cfg_rwlp);
        nscdb->cfg = ctx->cfg;
        nscdb->cfg_mtime = ctx->cfg_mtime;
        (void) rw_unlock(&ctx->cfg_rwlp);
        _NSCD_LOG(NSCD_LOG_CACHE, NSCD_LOG_LEVEL_DEBUG)
        (me, "config for context %s, database %s updated\n",
            ctx->dbname, nscdb->name);
    }
    *cfgp = nscdb->cfg;

    if (cfgp->enable == nscd_false) {
        _NSCD_LOG(NSCD_LOG_CACHE, NSCD_LOG_LEVEL_DEBUG)
            (me, "%s: cache disabled\n", ctx->dbname);

        if (UPDATEBIT & flag)
            return (NOTFOUND);
        else {
            NSC_LOOKUP_NO_CACHE(whoami);
        }
    }

    /*
     * if caller requests lookup using his
     * own nsswitch config, bypass cache
     */
    if (nsw_config_in_phdr(largs->buffer)) {
        NSC_LOOKUP_NO_CACHE(whoami);
    }

    /* no need of cache if we are dealing with 0 ttls */
    if (cfgp->pos_ttl <= 0 && cfgp->neg_ttl <= 0) {
        if (flag & UPDATEBIT)
            return (NOTFOUND);
        else if (cfgp->avoid_ns == nscd_true)
            return (SERVERERROR);
        NSC_LOOKUP_NO_CACHE(whoami);
    }

    return (CONTINUE);
}

/*
 * Invalidate cache if database file has been modified.
 * See check_files config param for details.
 */
static void
check_db_file(nsc_ctx_t *ctx, nscd_cfg_cache_t cfg,
    char *whoami, time_t now)
{
    struct stat buf;
    nscd_bool_t file_modified = nscd_false;
    char        *me = "check_db_file";

    if (cfg.check_interval != 0 &&
        (now - ctx->file_chktime) < cfg.check_interval)
        return;

    ctx->file_chktime = now;
    if (stat(ctx->file_name, &buf) == 0) {
        if (ctx->file_mtime == 0) {
            (void) mutex_lock(&ctx->file_mutex);
            if (ctx->file_mtime == 0) {
                ctx->file_mtime = buf.st_mtime;
                ctx->file_size = buf.st_size;
                ctx->file_ino = buf.st_ino;
            }
            (void) mutex_unlock(&ctx->file_mutex);
        } else if (ctx->file_mtime < buf.st_mtime ||
                ctx->file_size != buf.st_size ||
                ctx->file_ino != buf.st_ino) {
            (void) mutex_lock(&ctx->file_mutex);
            if (ctx->file_mtime < buf.st_mtime ||
                ctx->file_size != buf.st_size ||
                ctx->file_ino != buf.st_ino) {
                file_modified = nscd_true;
                ctx->file_mtime = buf.st_mtime;
                ctx->file_size = buf.st_size;
                ctx->file_ino = buf.st_ino;
            }
            (void) mutex_unlock(&ctx->file_mutex);
        }
    }

    if (file_modified == nscd_true) {
        _NSCD_LOG(NSCD_LOG_CACHE, NSCD_LOG_LEVEL_DEBUG)
    (me, "%s: file %s has been modified - invalidating cache\n",
        whoami, ctx->file_name);
        ctx_invalidate(ctx);
    }
}

static int
lookup_int(nsc_lookup_args_t *largs, int flag) {

    nsc_ctx_t       *ctx;
    nsc_db_t        *nscdb;
    nscd_cfg_cache_t    cfg;
    nsc_entry_t     *this_entry;
    nsc_entry_stat_t    *this_stats;
    nsc_action_t        next_action;
    nss_status_t        status;
    nscd_bool_t     delete;
    nscd_rc_t       rc;
    char            *dbname;
    int         dbop, errnum;
    int         cfg_rc;
    nss_XbyY_args_t     args;
    char            whoami[128];
    time_t          now = time(NULL); /* current time */
    char            *me = "lookup_int";

    /* extract dbop, dbname, key and cred */
    status = nss_packed_getkey(largs->buffer, largs->bufsize, &dbname,
                &dbop, &args);
    if (status != NSS_SUCCESS) {
        _NSCD_LOG(NSCD_LOG_CACHE, NSCD_LOG_LEVEL_ERROR)
            (me, "nss_packed_getkey failure (%d)\n", status);
        return (SERVERERROR);
    }

    /* get the cache context */
    if (largs->ctx == NULL) {
        if (get_cache_ctx(dbname, &largs->ctx) != NSCD_SUCCESS) {
            _NSCD_LOG(NSCD_LOG_CACHE, NSCD_LOG_LEVEL_WARNING)
                (me, "%s: no cache context found\n", dbname);

            if (UPDATEBIT & flag)
                return (NOTFOUND);
            else {
                NSC_LOOKUP_NO_CACHE(dbname);
            }
        }
    }
    ctx = largs->ctx;

    if (largs->nscdb == NULL) {
        if ((largs->nscdb = nsc_get_db(ctx, dbop)) == NULL) {
            _NSCD_LOG(NSCD_LOG_CACHE, NSCD_LOG_LEVEL_WARNING)
                (me, "%s:%d: no cache found\n",
                dbname, dbop);

            if (UPDATEBIT & flag)
                return (NOTFOUND);
            else {
                NSC_LOOKUP_NO_CACHE(dbname);
            }
        }
    }

    nscdb = largs->nscdb;

    _NSCD_LOG_IF(NSCD_LOG_CACHE, NSCD_LOG_LEVEL_ALL) {
        (void) nscdb->getlogstr(nscdb->name, whoami,
            sizeof (whoami), &args);
    }

    if (UPDATEBIT & flag) {
        _NSCD_LOG(NSCD_LOG_CACHE, NSCD_LOG_LEVEL_DEBUG)
            (me, "%s: refresh start\n", whoami);
    } else {
        _NSCD_LOG(NSCD_LOG_CACHE, NSCD_LOG_LEVEL_DEBUG)
            (me, "%s: lookup start\n", whoami);
    }

    cfg_rc = check_config(largs, &cfg, whoami, flag);
    if (cfg_rc != CONTINUE)
        return (cfg_rc);

    /*
     * Invalidate cache if file has been modified.
     */
    if (cfg.check_files == nscd_true)
        check_db_file(ctx, cfg, whoami, now);

    (void) mutex_lock(&nscdb->db_mutex);

    /* Lookup the cache table */
    for (;;) {
        delete = nscd_false;
        rc = lookup_cache(largs, &cfg, &args, whoami, &this_entry);
        if (rc != NSCD_SUCCESS) {
            (void) mutex_unlock(&nscdb->db_mutex);

            /* Either no entry and avoid name service */
            if (rc == NSCD_DB_ENTRY_NOT_FOUND ||
                    rc == NSCD_INVALID_ARGUMENT)
                return (NOTFOUND);

            /* OR memory error */
            return (SERVERERROR);
        }

        /* get the stats from the entry */
        this_stats = &this_entry->stats;

        /*
         * What should we do next ?
         */
        switch (this_stats->status) {
        case ST_NEW_ENTRY:
            delete = nscd_true;
            next_action = _NSC_NSLOOKUP;
            break;
        case ST_UPDATE_PENDING:
            if (flag & UPDATEBIT) {
                (void) mutex_unlock(&nscdb->db_mutex);
                return (NOTFOUND);
            } else if (this_stats->timestamp < now)
                next_action = _NSC_WAIT;
            else
                next_action = _NSC_USECACHED;
            break;
        case ST_LOOKUP_PENDING:
            if (flag & UPDATEBIT) {
                (void) mutex_unlock(&nscdb->db_mutex);
                return (NOTFOUND);
            }
            next_action = _NSC_WAIT;
            break;
        case ST_DISCARD:
            if (cfg.avoid_ns == nscd_true) {
                (void) mutex_unlock(&nscdb->db_mutex);
                return (NOTFOUND);
            }
            /* otherwise reuse the entry */
            (void) memset(this_stats, 0, sizeof (*this_stats));
            next_action = _NSC_NSLOOKUP;
            break;
        default:
            if (cfg.avoid_ns == nscd_true)
                next_action = _NSC_USECACHED;
            else if ((flag & UPDATEBIT) ||
                    (this_stats->timestamp < now)) {
                _NSCD_LOG(NSCD_LOG_CACHE, NSCD_LOG_LEVEL_DEBUG)
            (me, "%s: cached entry needs to be updated\n",
                whoami);
                next_action = _NSC_NSLOOKUP;
            } else
                next_action = _NSC_USECACHED;
            break;
        }

        if (next_action == _NSC_WAIT) {
            _NSCD_LOG(NSCD_LOG_CACHE, NSCD_LOG_LEVEL_DEBUG)
            (me, "%s: need to wait\n", whoami);

            /* do we have clearance ? */
            if (_nscd_get_clearance(&ctx->throttle_sema) != 0) {
                /* nope. quit */
                (void) mutex_lock(&ctx->stats_mutex);
                ctx->stats.drop_count++;
                (void) mutex_unlock(&ctx->stats_mutex);
                NSC_LOOKUP_RETURN(NOSERVER, WARNING,
                "%s: no clearance to wait\n");
            }
            /* yes can wait */
            (void) nscd_wait(&ctx->wait, &nscdb->db_mutex,
                    &this_stats->status);
            (void) _nscd_release_clearance(&ctx->throttle_sema);
            continue;
        }

        break;
    }


    if (!(UPDATEBIT & flag))
        this_stats->hits++;     /* update hit count */

    if (next_action == _NSC_NSLOOKUP) {

        _NSCD_LOG(NSCD_LOG_CACHE, NSCD_LOG_LEVEL_DEBUG)
        (me, "%s: name service lookup required\n", whoami);

        if (_nscd_get_clearance(&ctx->throttle_sema) != 0) {
            if (delete == nscd_true)
                delete_entry(nscdb, ctx, this_entry);
            else
                this_stats->status = ST_DISCARD;
            (void) mutex_lock(&ctx->stats_mutex);
            ctx->stats.drop_count++;
            (void) mutex_unlock(&ctx->stats_mutex);
            NSC_LOOKUP_RETURN(NOSERVER, WARNING,
            "%s: no clearance for lookup\n");
        }

        /* block any threads accessing this entry */
        this_stats->status = (flag & UPDATEBIT)?
                ST_UPDATE_PENDING:ST_LOOKUP_PENDING;

        /* release lock and do name service lookup */
        (void) mutex_unlock(&nscdb->db_mutex);
        nss_psearch(largs->buffer, largs->bufsize);
        status = NSCD_GET_STATUS(largs->buffer);
        (void) mutex_lock(&nscdb->db_mutex);
        this_stats->status = 0;
        (void) _nscd_release_clearance(&ctx->throttle_sema);

        /* signal waiting threads */
        (void) nscd_signal(&ctx->wait, &this_stats->status);

        _NSCD_LOG(NSCD_LOG_CACHE, NSCD_LOG_LEVEL_DEBUG)
        (me, "%s: name service lookup status = %d\n",
            whoami, status);

        if (status == NSS_SUCCESS) {
            int ttl;

            /*
             * data found in name service
             * update cache
             */
            status = dup_packed_buffer(largs, this_entry);
            if (status != NSS_SUCCESS) {
                delete_entry(nscdb, ctx, this_entry);
                NSC_LOOKUP_RETURN(SERVERERROR, ERROR,
                "%s: failed to update cache\n");
            }

            /*
             * store unpacked key in cache
             */
            status = nss_packed_getkey(this_entry->buffer,
                    this_entry->bufsize,
                    &dbname, &dbop, &args);
            if (status != NSS_SUCCESS) {
                delete_entry(nscdb, ctx, this_entry);
                NSC_LOOKUP_RETURN(SERVERERROR, ERROR,
                "%s: failed to extract key\n");
            }
            this_entry->key = args.key; /* struct copy */

            /* update +ve miss count */
            if (!(UPDATEBIT & flag)) {
                (void) mutex_lock(&ctx->stats_mutex);
                ctx->stats.pos_misses++;
                (void) mutex_unlock(&ctx->stats_mutex);
            }

            /* update +ve ttl */
            ttl = get_dns_ttl(largs->buffer, dbname);
            /* honor the dns ttl less than postive ttl */
            if (ttl < 0 || ttl > cfg.pos_ttl)
                ttl = cfg.pos_ttl;
            this_stats->timestamp = time(NULL) + ttl;

            /*
             * start the revalidation and reaper threads
             * if not already started
             */
            start_threads(ctx);

            NSC_LOOKUP_RETURN(SUCCESS, DEBUG,
            "%s: cache updated with positive entry\n");
        } else if (status == NSS_NOTFOUND) {
            /*
             * data not found in name service
             * update cache
             */

            if (NSCD_GET_ERRNO(largs->buffer) == ERANGE) {
                delete_entry(nscdb, ctx, this_entry);
                NSC_LOOKUP_RETURN(NOTFOUND, DEBUG,
        "%s: ERANGE, cache not updated with negative entry\n");
            }

            status = dup_packed_buffer(largs, this_entry);
            if (status != NSS_SUCCESS) {
                delete_entry(nscdb, ctx, this_entry);
                NSC_LOOKUP_RETURN(SERVERERROR, ERROR,
                "%s: failed to update cache\n");
            }

            /* store unpacked key in cache */
            status = nss_packed_getkey(this_entry->buffer,
                    this_entry->bufsize,
                    &dbname, &dbop, &args);
            if (status != NSS_SUCCESS) {
                delete_entry(nscdb, ctx, this_entry);
                NSC_LOOKUP_RETURN(SERVERERROR, ERROR,
                "%s: failed to extract key\n");
            }
            this_entry->key = args.key; /* struct copy */

            /* update -ve ttl */
            this_stats->timestamp = time(NULL) + cfg.neg_ttl;

            /* update -ve miss count */
            if (!(UPDATEBIT & flag)) {
                (void) mutex_lock(&ctx->stats_mutex);
                ctx->stats.neg_misses++;
                (void) mutex_unlock(&ctx->stats_mutex);
            }

            /*
             * start the revalidation and reaper threads
             * if not already started
             */
            start_threads(ctx);

            NSC_LOOKUP_RETURN(NOTFOUND, DEBUG,
            "%s: cache updated with negative entry\n");
        } else {
            /*
             * name service lookup failed
             */
            errnum = NSCD_GET_ERRNO(largs->buffer);
            if (delete == nscd_true)
                delete_entry(nscdb, ctx, this_entry);
            else
                this_stats->status = ST_DISCARD;

            (void) mutex_unlock(&nscdb->db_mutex);
            _NSCD_LOG(NSCD_LOG_CACHE, NSCD_LOG_LEVEL_WARNING)
    (me, "%s: name service lookup failed (status=%d, errno=%d)\n",
                whoami, status, errnum);

            return (SERVERERROR);
        }
    } else if (next_action == _NSC_USECACHED) {
        /*
         * found entry in cache
         */
        if (UPDATEBIT & flag) {
            NSC_LOOKUP_RETURN(SUCCESS, DEBUG,
            "%s: no need to update\n");
        }

        if (NSCD_GET_STATUS((nss_pheader_t *)this_entry->buffer) ==
            NSS_SUCCESS) {
            /* positive hit */
            (void) mutex_lock(&ctx->stats_mutex);
            ctx->stats.pos_hits++;
            (void) mutex_unlock(&ctx->stats_mutex);

            /* update response buffer */
            if (copy_result(largs->buffer,
                this_entry->buffer) != NSS_SUCCESS) {
                NSC_LOOKUP_RETURN(SERVERERROR, ERROR,
                "%s: response buffer insufficient\n");
            }

            NSC_LOOKUP_RETURN(SUCCESS, DEBUG,
            "%s: positive entry in cache\n");
        } else {
            /* negative hit */
            (void) mutex_lock(&ctx->stats_mutex);
            ctx->stats.neg_hits++;
            (void) mutex_unlock(&ctx->stats_mutex);

            NSCD_SET_STATUS((nss_pheader_t *)largs->buffer,
                NSCD_GET_STATUS(this_entry->buffer),
                NSCD_GET_ERRNO(this_entry->buffer));
            NSCD_SET_HERRNO((nss_pheader_t *)largs->buffer,
                NSCD_GET_HERRNO(this_entry->buffer));

            NSC_LOOKUP_RETURN(NOTFOUND, DEBUG,
            "%s: negative entry in cache\n");
        }
    }

    NSC_LOOKUP_RETURN(SERVERERROR, ERROR,
    "%s: cache backend failure\n");
}

/*
 * NSCD cache backend lookup function
 */
/*ARGSUSED*/
void
nsc_lookup(nsc_lookup_args_t *largs, int flag) {

    nss_pheader_t   *phdr = (nss_pheader_t *)largs->buffer;
    int     rc;

    rc = lookup_int(largs, 0);

    if (NSCD_GET_STATUS(phdr) == NSS_TRYLOCAL)
        return;

    switch (rc) {

    case SUCCESS:
        NSCD_RETURN_STATUS(phdr, NSS_SUCCESS, 0);
        break;

    case NOTFOUND:
        NSCD_RETURN_STATUS(phdr, NSS_NOTFOUND, -1);
        break;

    case SERVERERROR:
        /* status and errno already set in the phdr */
        break;

    case NOSERVER:
        NSCD_RETURN_STATUS(phdr, NSS_UNAVAIL, -1);
        break;
    }
}


static nsc_ctx_t *
init_cache_ctx(int i) {
    nsc_ctx_t   *ctx;

    ctx = calloc(1, sizeof (nsc_ctx_t));
    if (ctx == NULL)
        return (NULL);

    /* init locks and semaphores */
    (void) mutex_init(&ctx->file_mutex, USYNC_THREAD, NULL);
    (void) rwlock_init(&ctx->cfg_rwlp, USYNC_THREAD, NULL);
    (void) mutex_init(&ctx->stats_mutex, USYNC_THREAD, NULL);
    (void) _nscd_init_cache_sema(&ctx->throttle_sema, cache_name[i]);
    cache_init_ctx[i](ctx);
    cache_ctx_p[i] = ctx;

    return (ctx);
}


static void
revalidate(nsc_ctx_t *ctx)
{
    for (;;) {
        int         i, slp, interval, count;

        (void) rw_rdlock(&ctx->cfg_rwlp);
        slp = ctx->cfg.pos_ttl;
        count = ctx->cfg.keephot;
        (void) rw_unlock(&ctx->cfg_rwlp);

        if (slp < 60)
            slp = 60;
        if (count != 0) {
            interval = (slp/2)/count;
            if (interval == 0)
                interval = 1;
            (void) sleep(slp*2/3);
            for (i = 0; i < ctx->db_count; i++) {
                getxy_keepalive(ctx, ctx->nsc_db[i],
                        count, interval);
            }
        } else {
            (void) sleep(slp);
        }
    }
}


static void
getxy_keepalive(nsc_ctx_t *ctx, nsc_db_t *nscdb, int keep, int interval)
{
    nsc_keephot_t       *table;
    nsc_entry_t     *entry, *ptr;
    int         i;
    nsc_lookup_args_t   *largs;
    nss_pheader_t       *phdr;
    int         bufsiz;
    char            *me = "getxy_keepalive";

    /* we won't be here if keep == 0 so need to check that */

    _NSCD_LOG(NSCD_LOG_CACHE, NSCD_LOG_LEVEL_DEBUG)
    (me, "%s: keep alive\n", nscdb->name);

    if ((table = maken(keep)) == NULL) {
        _NSCD_LOG(NSCD_LOG_CACHE, NSCD_LOG_LEVEL_ERROR)
            (me, "memory allocation failure\n");
        exit(1);
    }

    (void) mutex_lock(&nscdb->db_mutex);
    entry = nscdb->qtail;
    while (entry != NULL) {
        /* leave pending calls alone */
        if (!(entry->stats.status & ST_PENDING)) {
            /* do_revalidate */
            (void) insertn(table, entry->stats.hits,
                    entry);
        }
        entry = entry->qnext;
    }
    for (i = 1; i <= keep; i++) {
        if (table[i].ptr == NULL)
            continue;
        ptr = (nsc_entry_t *)table[i].ptr;
        phdr = (nss_pheader_t *)ptr->buffer;
        if (NSCD_GET_STATUS(phdr) == NSS_SUCCESS)
            /*
             * for positive cache, in addition to the packed
             * header size, allocate twice the size of the
             * existing result (in case the result grows
             * larger) plus 2K (for the file/compat backend to
             * process a possible large entry in the /etc files)
             */
            bufsiz = phdr->data_off + 2 * phdr->data_len + 2048;
        else
            /*
             * for negative cache, allocate 8K buffer to
             * hold result in case the next lookup may
             * return something (in addition to the
             * packed header size)
             */
            bufsiz = phdr->data_off + 8096;
        table[i].ptr = malloc(bufsiz);
        if (table[i].ptr == NULL) {
            (void) mutex_unlock(&nscdb->db_mutex);
            _NSCD_LOG(NSCD_LOG_CACHE, NSCD_LOG_LEVEL_ERROR)
                (me, "memory allocation failure\n");
            exit(1);
        }
        (void) memcpy(table[i].ptr, ptr->buffer,  ptr->bufsize);
        ((nss_pheader_t *)table[i].ptr)->pbufsiz = bufsiz;
        table[i].num = bufsiz;
    }
    (void) mutex_unlock(&nscdb->db_mutex);

    /* launch update thread for each keep hot entry */
    for (i = keep; i > 0; i--) {
        if (table[i].ptr == NULL)
            continue; /* unused slot in table */
        _NSCD_LOG(NSCD_LOG_CACHE, NSCD_LOG_LEVEL_DEBUG)
        (me, "%s: launching update\n", nscdb->name);
        largs = (nsc_lookup_args_t *)malloc(sizeof (*largs));
        if (largs == NULL) {
            _NSCD_LOG(NSCD_LOG_CACHE, NSCD_LOG_LEVEL_ERROR)
                (me, "memory allocation failure\n");
            exit(1);
        }
        largs->buffer = table[i].ptr;
        largs->bufsize = table[i].num;
        largs->ctx = ctx;
        largs->nscdb = nscdb;
        if (launch_update(largs) < 0)
            exit(1);
        (void) sleep(interval);
    }

    /*
     * The update thread will handle freeing of buffer and largs.
     * Free the table here.
     */
    free(table);
}


static int
launch_update(nsc_lookup_args_t *in)
{
    char    *me = "launch_update";
    int errnum;

    errnum = thr_create(NULL, NULL, (void *(*)(void*))do_update,
            in, 0|THR_DETACHED, NULL);
    if (errnum != 0) {
        _NSCD_LOG(NSCD_LOG_CACHE, NSCD_LOG_LEVEL_ERROR)
            (me, "%s: thread creation failure (%d)\n",
            in->nscdb->name, errnum);
        return (-1);
    }
    return (0);
}


static void
do_update(nsc_lookup_args_t *in) {
    nss_pheader_t   *phdr = (nss_pheader_t *)in->buffer;

    /* update the length of the data buffer */
    phdr->data_len = phdr->pbufsiz - phdr->data_off;

    (void) lookup_int(in, UPDATEBIT);
    if (in->buffer)
        free(in->buffer);
    free(in);
}


/*
 * Invalidate cache
 */
void
nsc_invalidate(nsc_ctx_t *ctx, char *dbname, nsc_ctx_t **ctxs) {
    int i;
    char    *me = "nsc_invalidate";

    if (ctx) {
        ctx_invalidate(ctx);
        return;
    }

    if (dbname) {
        if ((i = get_cache_idx(dbname)) == -1) {
            _NSCD_LOG(NSCD_LOG_CACHE,
                NSCD_LOG_LEVEL_WARNING)
            (me, "%s: invalid cache name\n", dbname);
            return;
        }
        if ((ctx = cache_ctx_p[i]) == NULL)  {
            _NSCD_LOG(NSCD_LOG_CACHE,
                NSCD_LOG_LEVEL_WARNING)
            (me, "%s: no cache context found\n",
                dbname);
            return;
        }
        ctx_invalidate(ctx);
        return;
    }

    if (ctxs == NULL)
        ctxs =  cache_ctx_p;

    for (i = 0; i < CACHE_CTX_COUNT; i++) {
        if (ctxs[i] != NULL)
        ctx_invalidate(ctxs[i]);
    }
}


/*
 * Invalidate cache by context
 */
static void
ctx_invalidate(nsc_ctx_t *ctx) {
    int         i;
    nsc_entry_t *entry;
    char        *me = "ctx_invalidate";

    _NSCD_LOG(NSCD_LOG_CACHE, NSCD_LOG_LEVEL_DEBUG)
    (me, "%s: invalidate cache\n", ctx->dbname);

    for (i = 0; i < ctx->db_count; i++) {
        if (ctx->nsc_db[i] == NULL)
            continue;
        (void) mutex_lock(&ctx->nsc_db[i]->db_mutex);
        entry = ctx->nsc_db[i]->qtail;
        while (entry != NULL) {
            /* leave pending calls alone */
            if (!(entry->stats.status & ST_PENDING))
                entry->stats.status = ST_DISCARD;
            entry = entry->qnext;
        }
        (void) mutex_unlock(&ctx->nsc_db[i]->db_mutex);
    }

    (void) mutex_lock(&ctx->stats_mutex);
    ctx->stats.invalidate_count++;
    (void) mutex_unlock(&ctx->stats_mutex);
}


/*
 * Free nsc_entry_t
 *
 * Pre-reqs:
 * nscdb->db_mutex lock must be held before calling this function
 */
static void
delete_entry(nsc_db_t *nscdb, nsc_ctx_t *ctx, nsc_entry_t *entry) {
    uint_t      hash;

    avl_remove(&nscdb->tree, entry);
    HASH_REMOVE(nscdb, entry, hash, nscd_false);
    queue_remove(nscdb, entry);
    if (entry->buffer != NULL) {
        free(entry->buffer);
        entry->buffer = NULL;
    }
    umem_cache_free(nsc_entry_cache, entry);
    (void) mutex_lock(&ctx->stats_mutex);
    ctx->stats.entries--;
    (void) mutex_unlock(&ctx->stats_mutex);
}


static nscd_rc_t
lookup_cache(nsc_lookup_args_t *largs, nscd_cfg_cache_t *cfgp,
    nss_XbyY_args_t *argp, char *whoami, nsc_entry_t **entry) {

    nsc_db_t    *nscdb;
    nsc_ctx_t   *ctx;
    uint_t      hash;
    avl_index_t pos;
    ulong_t     nentries;
    nsc_entry_t find_entry, *node;
    char        *me = "lookup_cache";

    ctx = largs->ctx;
    nscdb = largs->nscdb;

    /* set the search key */
    find_entry.key = argp->key; /* struct copy (not deep) */

    /* lookup the hash table ==> O(1) */
    if (nscdb->htable) {
        *entry = hash_find(nscdb, &find_entry, &hash, nscd_true);
        if (*entry != NULL) {
            (void) queue_adjust(nscdb, *entry);
            return (NSCD_SUCCESS);
        }
    }

    /* if not found, lookup the AVL tree ==> O(log n) */
    *entry = (nsc_entry_t *)avl_find(&nscdb->tree, &find_entry, &pos);
    if (*entry != NULL) {
        (void) queue_adjust(nscdb, *entry);
        /* move it to the hash table */
        if (nscdb->htable) {
            if (nscdb->htable[hash] == NULL ||
                    (*entry)->stats.hits >=
                    nscdb->htable[hash]->stats.hits) {
                nscdb->htable[hash] = *entry;
            }
        }
        return (NSCD_SUCCESS);
    }

    /* entry not found in the cache */
    _NSCD_LOG(NSCD_LOG_CACHE, NSCD_LOG_LEVEL_DEBUG)
        (me, "%s: cache miss\n", whoami);

    if (cfgp->avoid_ns == nscd_true) {
        _NSCD_LOG(NSCD_LOG_CACHE,
            NSCD_LOG_LEVEL_DEBUG)
            (me, "%s: avoid name service\n", whoami);
        return (NSCD_DB_ENTRY_NOT_FOUND);
    }

    /* allocate memory for new entry (stub) */
    *entry = (nsc_entry_t *)umem_cache_alloc(nsc_entry_cache,
        UMEM_DEFAULT);
    if (*entry == NULL) {
        _NSCD_LOG(NSCD_LOG_CACHE,
            NSCD_LOG_LEVEL_ERROR)
            (me, "%s: memory allocation failure\n", whoami);
        return (NSCD_NO_MEMORY);
    }
    (void) memset(*entry, 0, sizeof (**entry));

    /*
     * Note that the actual data for the key is stored within
     * the largs->buffer (input buffer to nsc_lookup).
     * find_entry.key only contains pointers to this data.
     *
     * If largs->buffer will be re-allocated by nss_psearch
     * then (*entry)->key will have dangling pointers.
     * In such case, the following assignment needs to be
     * replaced by code that duplicates the key.
     */
    (*entry)->key = find_entry.key;

    /*
     * Add the entry to the cache.
     */
    avl_insert(&nscdb->tree, *entry, pos);  /* O(log n) */
    (void) queue_adjust(nscdb, *entry); /* constant */
    if (nscdb->htable)          /* constant */
        nscdb->htable[hash] = *entry;
    (*entry)->stats.status = ST_NEW_ENTRY;

    (void) mutex_lock(&ctx->stats_mutex);
    nentries = ++(ctx->stats.entries);
    (void) mutex_unlock(&ctx->stats_mutex);

    /* Have we exceeded max entries ? */
    if (cfgp->maxentries > 0 && nentries > cfgp->maxentries) {
        _NSCD_LOG(NSCD_LOG_CACHE, NSCD_LOG_LEVEL_DEBUG)
            (me, "%s: maximum entries exceeded -- "
                "deleting least recently used entry\n",
            whoami);

        node = nscdb->qhead;
        while (node != NULL && node != *entry) {
            if (node->stats.status == ST_DISCARD ||
                    !(node->stats.status & ST_PENDING)) {
                delete_entry(nscdb, ctx, node);
                break;
            }
            node = node->qprev;
        }

        /*
         * It's okay if we were not able to find one to delete.
         * The reaper (when invoked) will return the cache to a
         * safe level.
         */
    }

    return (NSCD_SUCCESS);
}

static void
reaper(nsc_ctx_t *ctx) {
    uint_t      ttl, extra_sleep, total_sleep, intervals;
    uint_t      nodes_per_interval, seconds_per_interval;
    ulong_t     nsc_entries;
    char        *me = "reaper";

    for (;;) {
        (void) mutex_lock(&ctx->stats_mutex);
        nsc_entries = ctx->stats.entries;
        (void) mutex_unlock(&ctx->stats_mutex);

        (void) rw_rdlock(&ctx->cfg_rwlp);
        ttl = ctx->cfg.pos_ttl;
        (void) rw_unlock(&ctx->cfg_rwlp);

        if (nsc_entries == 0) {
            _NSCD_LOG(NSCD_LOG_CACHE, NSCD_LOG_LEVEL_DEBUG)
                (me, "%s: nothing to reap\n", ctx->dbname);

            /* sleep for atleast 60 seconds */
            if (ttl < 60)
                ttl = 60;
            _NSCD_LOG(NSCD_LOG_CACHE, NSCD_LOG_LEVEL_DEBUG)
            (me, "%s: sleep %d\n", ctx->dbname, ttl);
            (void) sleep(ttl);
            continue;
        }

        if (ttl < 32) ttl = 32;
        if (ttl > (1<<28)) ttl = 1<<28;

        /*
         * minimum nodes_per_interval = 256 or 1<<8
         * maximum nodes_per_interval = nsc_entries
         * minimum seconds_per_interval = 32 or 1<<5
         * maximum_seconds_per_interval = ttl
         */
        if (nsc_entries <= ttl) {
            intervals = (nsc_entries >> 8) + 1;
            seconds_per_interval = ttl / intervals;
            nodes_per_interval = 256;
        } else {
            intervals = (ttl >> 5) + 1;
            seconds_per_interval = 32;
            nodes_per_interval = nsc_entries / intervals;
            if (nodes_per_interval < 256)
                nodes_per_interval = 256;
        }

        _NSCD_LOG(NSCD_LOG_CACHE, NSCD_LOG_LEVEL_DEBUG)
            (me, "%s: total entries = %d, "
            "seconds per interval = %d, "
            "nodes per interval = %d\n",
            ctx->dbname, nsc_entries, seconds_per_interval,
            nodes_per_interval);
        total_sleep = reap_cache(ctx, nodes_per_interval,
                seconds_per_interval);
        extra_sleep = 1 + ttl - total_sleep;
        if (extra_sleep > 0)
            (void) sleep(extra_sleep);
    }
}


static uint_t
reap_cache(nsc_ctx_t *ctx, uint_t nodes_per_interval,
        uint_t seconds_per_interval) {
    uint_t      nodes_togo, total_sleep;
    time_t      now;
    nsc_entry_t *node, *next_node;
    nsc_db_t    *nscdb;
    uint_t      primes[] = {_NSC_HTSIZE_PRIMES};
    ulong_t     count, nentries, maxentries;
    int     i, slot, value, newhtsize;
    char        *me = "reap_cache";

    count = 0;
    total_sleep = 0;
    nodes_togo = nodes_per_interval;
    now = time(NULL);

    for (i = 0; i < ctx->db_count; i++) {
        nscdb = ctx->nsc_db[i];
        (void) mutex_lock(&nscdb->db_mutex);
        nscdb->reap_node = nscdb->qtail;
        while (nscdb->reap_node != NULL) {
            if (nodes_togo == 0) {
                (void) mutex_unlock(&nscdb->db_mutex);
                (void) sleep(seconds_per_interval);
                total_sleep += seconds_per_interval;
                nodes_togo = nodes_per_interval;
                now = time(NULL);
                (void) mutex_lock(&nscdb->db_mutex);
            }
            /* delete ST_DISCARD and expired nodes */
            if ((node = nscdb->reap_node) == NULL)
                break;
            if (node->stats.status == ST_DISCARD ||
                    (!(node->stats.status & ST_PENDING) &&
                    node->stats.timestamp < now)) {
                /*
                 * Delete entry if its discard flag is
                 * set OR if it has expired. Entries
                 * with pending updates are not
                 * deleted.
                 * nscdb->reap_node will be adjusted
                 * by delete_entry()
                 */
                delete_entry(nscdb, ctx, node);
                count++;
            } else {
                nscdb->reap_node = node->qnext;
            }
            nodes_togo--;
        }

        if (nscdb->htsize == 0) {
            (void) mutex_unlock(&nscdb->db_mutex);
            continue;
        }

        /*
         * Dynamic adjustment of hash table size.
         *
         * Hash table size is roughly 1/8th of the
         * total entries. However the size is changed
         * only when the number of entries double or
         * reduced by half
         */
        nentries = avl_numnodes(&nscdb->tree);
        for (slot = 0, value = _NSC_INIT_HTSIZE_SLOT_VALUE;
            slot < _NSC_HTSIZE_NUM_SLOTS && nentries > value;
            value = (value << 1) + 1, slot++);
        if (nscdb->hash_type == nsc_ht_power2)
            newhtsize = _NSC_INIT_HTSIZE_POWER2 << slot;
        else
            newhtsize = primes[slot];

        /* Recommended size is same as the current size. Done */
        if (nscdb->htsize == newhtsize) {
            (void) mutex_unlock(&nscdb->db_mutex);
            continue;
        }

        _NSCD_LOG(NSCD_LOG_CACHE, NSCD_LOG_LEVEL_DEBUG)
            (me, "%s: resizing hash table from %d to %d\n",
            nscdb->name, nscdb->htsize, newhtsize);

        /*
         * Dump old hashes because it would be time
         * consuming to rehash them.
         */
        (void) free(nscdb->htable);
        nscdb->htable = calloc(newhtsize, sizeof (*(nscdb->htable)));
        if (nscdb->htable == NULL) {
            _NSCD_LOG(NSCD_LOG_CACHE, NSCD_LOG_LEVEL_ERROR)
                (me,
                "%s: memory allocation failure\n",
                nscdb->name);
            /* -1 to try later */
            nscdb->htsize = -1;
        } else {
            nscdb->htsize = newhtsize;
        }
        (void) mutex_unlock(&nscdb->db_mutex);
    }

    _NSCD_LOG(NSCD_LOG_CACHE, NSCD_LOG_LEVEL_DEBUG)
        (me, "%s: reaped %lu entries\n", ctx->dbname, count);

    /*
     * if cache is almost full then reduce it to a safe level by
     * evicting LRU entries
     */

    (void) rw_rdlock(&ctx->cfg_rwlp);
    maxentries = ctx->cfg.maxentries;
    (void) rw_unlock(&ctx->cfg_rwlp);

    /* No limit on number of entries. Done */
    if (maxentries == 0)
        goto out;

    (void) mutex_lock(&ctx->stats_mutex);
    nentries = ctx->stats.entries;
    (void) mutex_unlock(&ctx->stats_mutex);

    /* what is the percentage of cache used ? */
    value = (nentries * 100) / maxentries;
    if (value < _NSC_EVICTION_START_LEVEL)
        goto out;

    /*
     * cache needs to be reduced to a safe level
     */
    value -= _NSC_EVICTION_SAFE_LEVEL;
    for (i = 0, count = 0; i < ctx->db_count; i++) {
        /*
         * Reduce each subcache by 'value' percent
         */
        nscdb = ctx->nsc_db[i];
        (void) mutex_lock(&nscdb->db_mutex);
        nodes_togo = (value * avl_numnodes(&nscdb->tree)) / 100;

        /* Start from LRU entry i.e queue head */
        next_node = nscdb->qhead;
        while (nodes_togo > 0 && next_node != NULL) {
            node = next_node;
            next_node = next_node->qprev;
            if (node->stats.status == ST_DISCARD ||
                    !(node->stats.status & ST_PENDING)) {
                /* Leave nodes with pending updates alone  */
                delete_entry(nscdb, ctx, node);
                count++;
                nodes_togo--;
            }
        }
        (void) mutex_unlock(&nscdb->db_mutex);
    }

    _NSCD_LOG(NSCD_LOG_CACHE, NSCD_LOG_LEVEL_DEBUG)
        (me, "%s: evicted %lu LRU entries\n", ctx->dbname, count);

out:
    return (total_sleep);
}