lib/dns/adb.c

	adb.c revision 08d131595373326ec4a3af793b536df8c33115ec
/*
 * Copyright (C) 1999  Internet Software Consortium.
 *
 * Permission to use, copy, modify, and distribute this software for any
 * purpose with or without fee is hereby granted, provided that the above
 * copyright notice and this permission notice appear in all copies.
 *
 * THE SOFTWARE IS PROVIDED "AS IS" AND INTERNET SOFTWARE CONSORTIUM DISCLAIMS
 * ALL WARRANTIES WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES
 * OF MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL INTERNET SOFTWARE
 * CONSORTIUM BE LIABLE FOR ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL
 * DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR
 * PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS
 * ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS
 * SOFTWARE.
 */

/*
 * Implementation notes
 * --------------------
 *
 * In handles, if task == NULL, no events will be generated, and no events
 * have been sent.  If task != NULL but taskaction == NULL, an event has been
 * posted but not yet freed.  If neigher are NULL, no event was posted.
 *
 */

#include <config.h>

#include <stdio.h>
#include <string.h>

#include <isc/assertions.h>
#include <isc/condition.h>
#include <isc/event.h>
#include <isc/magic.h>
#include <isc/mutex.h>
#include <isc/mutexblock.h>
#include <isc/random.h>
#include <isc/timer.h>

#include <dns/adb.h>
#include <dns/db.h>
#include <dns/events.h>
#include <dns/fixedname.h>
#include <dns/name.h>
#include <dns/rdata.h>
#include <dns/rdataset.h>
#include <dns/resolver.h>
#include <dns/types.h>
#include <dns/view.h>

#include "../isc/util.h"

#define DNS_ADB_MAGIC         0x44616462    /* Dadb. */
#define DNS_ADB_VALID(x)      ISC_MAGIC_VALID(x, DNS_ADB_MAGIC)
#define DNS_ADBNAME_MAGIC     0x6164624e    /* adbN. */
#define DNS_ADBNAME_VALID(x)      ISC_MAGIC_VALID(x, DNS_ADBNAME_MAGIC)
#define DNS_ADBNAMEHOOK_MAGIC     0x61644e48    /* adNH. */
#define DNS_ADBNAMEHOOK_VALID(x)  ISC_MAGIC_VALID(x, DNS_ADBNAMEHOOK_MAGIC)
#define DNS_ADBZONEINFO_MAGIC     0x6164625a    /* adbZ. */
#define DNS_ADBZONEINFO_VALID(x)  ISC_MAGIC_VALID(x, DNS_ADBZONEINFO_MAGIC)
#define DNS_ADBENTRY_MAGIC    0x61646245    /* adbE. */
#define DNS_ADBENTRY_VALID(x)     ISC_MAGIC_VALID(x, DNS_ADBENTRY_MAGIC)
#define DNS_ADBFETCH_MAGIC    0x61646246    /* adbF. */
#define DNS_ADBFETCH_VALID(x)     ISC_MAGIC_VALID(x, DNS_ADBFETCH_MAGIC)

/*
 * Lengths of lists needs to be powers of two.
 */
#define DNS_ADBNAMELIST_LENGTH  32  /* how many buckets for names */
#define DNS_ADBENTRYLIST_LENGTH 32  /* how many buckets for addresses */

#define CLEAN_SECONDS       20  /* clean this many seconds initially */

#define FREE_ITEMS      16  /* free count for memory pools */
#define FILL_COUNT       8  /* fill count for memory pools */

#define DNS_ADB_INVALIDBUCKET (-1)  /* invalid bucket address */

typedef ISC_LIST(dns_adbname_t) dns_adbnamelist_t;
typedef struct dns_adbnamehook dns_adbnamehook_t;
typedef struct dns_adbzoneinfo dns_adbzoneinfo_t;
typedef ISC_LIST(dns_adbentry_t) dns_adbentrylist_t;
typedef struct dns_adbfetch dns_adbfetch_t;

struct dns_adb {
    unsigned int            magic;

    isc_mutex_t         lock;
    isc_mem_t              *mctx;
    dns_view_t             *view;
    isc_timermgr_t             *timermgr;
    isc_timer_t            *timer;
    isc_taskmgr_t              *taskmgr;
    isc_task_t             *task;
    isc_interval_t          tick_interval;

    unsigned int            irefcnt;
    unsigned int            erefcnt;

    isc_mutex_t         mplock;
    isc_mempool_t              *nmp;    /* dns_adbname_t */
    isc_mempool_t              *nhmp;   /* dns_adbnamehook_t */
    isc_mempool_t              *zimp;   /* dns_adbzoneinfo_t */
    isc_mempool_t              *emp;    /* dns_adbentry_t */
    isc_mempool_t              *ahmp;   /* dns_adbhandle_t */
    isc_mempool_t              *aimp;   /* dns_adbaddrinfo_t */
    isc_mempool_t              *afmp;   /* dns_adbfetch_t */

    isc_random_t            rand;

    /*
     * Bucketized locks and lists for names.
     */
    dns_adbnamelist_t       names[DNS_ADBNAMELIST_LENGTH];
    isc_mutex_t         namelocks[DNS_ADBNAMELIST_LENGTH];
    isc_boolean_t           name_sd[DNS_ADBNAMELIST_LENGTH];
    unsigned int            name_refcnt[DNS_ADBNAMELIST_LENGTH];

    /*
     * Bucketized locks for entries.
     */
    dns_adbentrylist_t      entries[DNS_ADBENTRYLIST_LENGTH];
    isc_mutex_t         entrylocks[DNS_ADBENTRYLIST_LENGTH];
};

struct dns_adbname {
    unsigned int            magic;
    dns_name_t          name;
    isc_boolean_t           partial_result;
    isc_stdtime_t           expire_time;
    ISC_LIST(dns_adbnamehook_t) namehooks;
    ISC_LIST(dns_adbfetch_t)    fetches;
    ISC_LIST(dns_adbhandle_t)   handles;
    ISC_LINK(dns_adbname_t)     link;
};

struct dns_adbfetch {
    unsigned int            magic;
    dns_adbnamehook_t          *namehook;
    dns_adbentry_t             *entry;
    dns_fetch_t            *fetch;
    dns_rdataset_t          rdataset;
    ISC_LINK(dns_adbfetch_t)    link;
};

/*
 * dns_adbnamehook_t
 *
 * This is a small widget that dangles off a dns_adbname_t.  It contains a
 * pointer to the address information about this host, and a link to the next
 * namehook that will contain the next address this host has.
 */
struct dns_adbnamehook {
    unsigned int            magic;
    dns_adbentry_t             *entry;
    ISC_LINK(dns_adbnamehook_t) link;
};

/*
 * dns_adbzoneinfo_t
 *
 * This is a small widget that holds zone-specific information about an
 * address.  Currently limited to lameness, but could just as easily be
 * extended to other types of information about zones.
 */
struct dns_adbzoneinfo {
    unsigned int            magic;

    dns_name_t          zone;
    isc_stdtime_t           lame_timer;

    ISC_LINK(dns_adbzoneinfo_t) link;
};

/*
 * An address entry.  It holds quite a bit of information about addresses,
 * including edns state, rtt, and of course the address of the host.
 */
struct dns_adbentry {
    unsigned int            magic;

    int             lock_bucket;
    unsigned int            refcnt;

    unsigned int            flags;
    int             edns_level; /* must be int! */
    int             goodness;   /* bad < 0 <= good */
    unsigned int            srtt;
    isc_sockaddr_t          sockaddr;

    ISC_LIST(dns_adbzoneinfo_t) zoneinfo;
    ISC_LINK(dns_adbentry_t)    link;
};

/*
 * Internal functions (and prototypes).
 */
static inline dns_adbname_t *new_adbname(dns_adb_t *, dns_name_t *);
static inline void free_adbname(dns_adb_t *, dns_adbname_t **);
static inline dns_adbnamehook_t *new_adbnamehook(dns_adb_t *,
                         dns_adbentry_t *);
static inline void free_adbnamehook(dns_adb_t *, dns_adbnamehook_t **);
static inline dns_adbzoneinfo_t *new_adbzoneinfo(dns_adb_t *, dns_name_t *);
static inline void free_adbzoneinfo(dns_adb_t *, dns_adbzoneinfo_t **);
static inline dns_adbentry_t *new_adbentry(dns_adb_t *);
static inline void free_adbentry(dns_adb_t *, dns_adbentry_t **);
static inline dns_adbhandle_t *new_adbhandle(dns_adb_t *);
static inline void free_adbhandle(dns_adb_t *, dns_adbhandle_t **);
static inline dns_adbaddrinfo_t *new_adbaddrinfo(dns_adb_t *,
                         dns_adbentry_t *);

static inline dns_adbname_t *find_name_and_lock(dns_adb_t *, dns_name_t *,
                        int *);
static inline dns_adbentry_t *find_entry_and_lock(dns_adb_t *,
                          isc_sockaddr_t *, int *);
static void print_dns_name(FILE *, dns_name_t *);
static void print_namehook_list(FILE *, dns_adbname_t *);
static void print_handle_list(FILE *, dns_adbname_t *);
static inline void inc_adb_irefcnt(dns_adb_t *, isc_boolean_t);
static inline isc_boolean_t dec_adb_irefcnt(dns_adb_t *, isc_boolean_t);
static inline void inc_adb_erefcnt(dns_adb_t *, isc_boolean_t);
static inline isc_boolean_t dec_adb_erefcnt(dns_adb_t *, isc_boolean_t);
static inline void inc_entry_refcnt(dns_adb_t *, dns_adbentry_t *,
                    isc_boolean_t);
static inline void dec_entry_refcnt(dns_adb_t *, dns_adbentry_t *,
                    isc_boolean_t);
static inline void violate_locking_hierarchy(isc_mutex_t *, isc_mutex_t *);
static void clean_namehooks_at_name(dns_adb_t *, dns_adbname_t *);
static void clean_handles_at_name(dns_adbname_t *, isc_eventtype_t);
static isc_result_t construct_name(dns_adb_t *, dns_adbhandle_t *,
                   dns_name_t *, dns_name_t *,
                   dns_adbname_t *, int, isc_stdtime_t);
static inline isc_boolean_t check_exit(dns_adb_t *);
static void timer_cleanup(isc_task_t *, isc_event_t *);

static inline void
violate_locking_hierarchy(isc_mutex_t *have, isc_mutex_t *want)
{
    if (isc_mutex_trylock(want) != ISC_R_SUCCESS) {
        UNLOCK(have);
        LOCK(want);
        LOCK(have);
    }
}

/*
 * The ADB _MUST_ be locked before calling.  Also, exit conditions must be
 * checked after calling this function.
 */
static void
shutdown_names(dns_adb_t *adb, isc_boolean_t kill_fetches)
{
    int bucket;
    dns_adbname_t *name;

    (void)kill_fetches;  /* XXX need to implement */

    for (bucket = 0 ; bucket < DNS_ADBNAMELIST_LENGTH ; bucket++) {
        LOCK(&adb->namelocks[bucket]);
        adb->name_sd[bucket] = ISC_TRUE;

        /*
         * Run through the list.  For each name, clean up handles
         * found there, and cancel any fetches running.  When
         * all the fetches are canceled, the name will destroy
         * itself.
         */
        name = ISC_LIST_HEAD(adb->names[bucket]);
        while (name != NULL) {
            clean_handles_at_name(name, DNS_EVENT_ADBSHUTDOWN);

            clean_namehooks_at_name(adb, name);

            /* XXX TODO: cancel fetches */

            /* if no fetches, kill! */
            ISC_LIST_UNLINK(adb->names[bucket], name, link);
            free_adbname(adb, &name);
            INSIST(adb->name_refcnt[bucket] > 0);
            adb->name_refcnt[bucket]--;

            name = ISC_LIST_HEAD(adb->names[bucket]);
        }

        if (adb->name_refcnt[bucket] == 0)
            dec_adb_irefcnt(adb, ISC_FALSE);

        UNLOCK(&adb->namelocks[bucket]);
    }
}

/*
 * Assumes the name bucket is locked.
 */
static void
clean_namehooks_at_name(dns_adb_t *adb, dns_adbname_t *name)
{
    dns_adbentry_t *entry;
    dns_adbnamehook_t *namehook;
    int addr_bucket;

    addr_bucket = DNS_ADB_INVALIDBUCKET;
    namehook = ISC_LIST_HEAD(name->namehooks);
    while (namehook != NULL) {
        INSIST(DNS_ADBNAMEHOOK_VALID(namehook));

        /*
         * Clean up the entry if needed.
         */
        entry = namehook->entry;
        if (entry != NULL) {
            INSIST(DNS_ADBENTRY_VALID(entry));

            if (addr_bucket != entry->lock_bucket) {
                if (addr_bucket != DNS_ADB_INVALIDBUCKET)
                    UNLOCK(&adb->entrylocks[addr_bucket]);
                addr_bucket = entry->lock_bucket;
                LOCK(&adb->entrylocks[addr_bucket]);
            }

            dec_entry_refcnt(adb, entry, ISC_FALSE);
        }

        /*
         * Free the namehook
         */
        namehook->entry = NULL;
        ISC_LIST_UNLINK(name->namehooks, namehook, link);
        free_adbnamehook(adb, &namehook);

        namehook = ISC_LIST_HEAD(name->namehooks);
    }

    if (addr_bucket != DNS_ADB_INVALIDBUCKET)
        UNLOCK(&adb->entrylocks[addr_bucket]);
}

/*
 * Assumes the name bucket is locked.
 */
static void
clean_handles_at_name(dns_adbname_t *name, isc_eventtype_t evtype)
{
    isc_event_t *ev;
    isc_task_t *task;
    dns_adbhandle_t *handle;

    handle = ISC_LIST_HEAD(name->handles);
    while (handle != NULL) {
        LOCK(&handle->lock);

        ev = &handle->event;
        task = ev->sender;
        ev->sender = handle;
        ev->type = evtype;
        isc_task_sendanddetach(&task, &ev);

        /*
         * Unlink the handle from the name, letting the caller
         * call dns_adb_done() on it to clean it up later.
         */
        ISC_LIST_UNLINK(name->handles, handle, link);
        handle->adbname = NULL;
        handle->name_bucket = DNS_ADB_INVALIDBUCKET;

        UNLOCK(&handle->lock);

        handle = ISC_LIST_HEAD(name->handles);
    }
}

static inline isc_boolean_t
check_exit(dns_adb_t *adb)
{
    if ((adb->irefcnt == 0)
        && (adb->erefcnt == 0)
        && (isc_mempool_getallocated(adb->ahmp) == 0))
        return (ISC_TRUE);
    return (ISC_FALSE);
}

static inline void
inc_adb_irefcnt(dns_adb_t *adb, isc_boolean_t lock)
{
    if (lock)
        LOCK(&adb->lock);

    adb->irefcnt++;

    if (lock)
        UNLOCK(&adb->lock);
}

static inline isc_boolean_t
dec_adb_irefcnt(dns_adb_t *adb, isc_boolean_t lock)
{
    isc_boolean_t kill;

    if (lock)
        LOCK(&adb->lock);

    INSIST(adb->irefcnt > 0);
    adb->irefcnt--;

    kill = check_exit(adb);

    if (lock)
        UNLOCK(&adb->lock);

    return (kill);
}

static inline void
inc_adb_erefcnt(dns_adb_t *adb, isc_boolean_t lock)
{
    if (lock)
        LOCK(&adb->lock);

    adb->erefcnt++;

    if (lock)
        UNLOCK(&adb->lock);
}

static inline isc_boolean_t
dec_adb_erefcnt(dns_adb_t *adb, isc_boolean_t lock)
{
    isc_boolean_t kill;

    if (lock)
        LOCK(&adb->lock);

    INSIST(adb->erefcnt > 0);
    adb->erefcnt--;

    kill = check_exit(adb);

    if (lock)
        UNLOCK(&adb->lock);

    return (kill);
}

static inline void
inc_entry_refcnt(dns_adb_t *adb, dns_adbentry_t *entry, isc_boolean_t lock)
{
    int bucket;

    bucket = entry->lock_bucket;

    if (lock)
        LOCK(&adb->entrylocks[bucket]);

    entry->refcnt++;

    if (lock)
        UNLOCK(&adb->entrylocks[bucket]);
}

static inline void
dec_entry_refcnt(dns_adb_t *adb, dns_adbentry_t *entry, isc_boolean_t lock)
{
    int bucket;
    isc_boolean_t destroy_entry;

    bucket = entry->lock_bucket;

    if (lock)
        LOCK(&adb->entrylocks[bucket]);

    INSIST(entry->refcnt > 0);
    entry->refcnt--;

    destroy_entry = ISC_FALSE;
    if (entry->refcnt == 0) {
        destroy_entry = ISC_TRUE;
        ISC_LIST_UNLINK(adb->entries[bucket], entry, link);
    }

    if (lock)
        UNLOCK(&adb->entrylocks[bucket]);

    if (!destroy_entry)
        return;

    entry->lock_bucket = DNS_ADB_INVALIDBUCKET;

    free_adbentry(adb, &entry);
}

static inline dns_adbname_t *
new_adbname(dns_adb_t *adb, dns_name_t *dnsname)
{
    dns_adbname_t *name;

    name = isc_mempool_get(adb->nmp);
    if (name == NULL)
        return (NULL);

    dns_name_init(&name->name, NULL);
    if (dns_name_dup(dnsname, adb->mctx, &name->name) != ISC_R_SUCCESS) {
        isc_mempool_put(adb->nmp, name);
        return (NULL);
    }

    name->magic = DNS_ADBNAME_MAGIC;
    name->partial_result = ISC_FALSE;
    name->expire_time = 0;
    ISC_LIST_INIT(name->namehooks);
    ISC_LIST_INIT(name->fetches);
    ISC_LIST_INIT(name->handles);
    ISC_LINK_INIT(name, link);

    return (name);
}

static inline void
free_adbname(dns_adb_t *adb, dns_adbname_t **name)
{
    dns_adbname_t *n;

    INSIST(name != NULL && DNS_ADBNAME_VALID(*name));
    n = *name;
    *name = NULL;

    INSIST(ISC_LIST_EMPTY(n->namehooks));
    INSIST(ISC_LIST_EMPTY(n->fetches));
    INSIST(ISC_LIST_EMPTY(n->handles));
    INSIST(!ISC_LINK_LINKED(n, link));

    n->magic = 0;
    dns_name_free(&n->name, adb->mctx);

    isc_mempool_put(adb->nmp, n);
}

static inline dns_adbnamehook_t *
new_adbnamehook(dns_adb_t *adb, dns_adbentry_t *entry)
{
    dns_adbnamehook_t *nh;

    nh = isc_mempool_get(adb->nhmp);
    if (nh == NULL)
        return (NULL);

    nh->magic = DNS_ADBNAMEHOOK_MAGIC;
    nh->entry = entry;
    ISC_LINK_INIT(nh, link);

    return (nh);
}

static inline void
free_adbnamehook(dns_adb_t *adb, dns_adbnamehook_t **namehook)
{
    dns_adbnamehook_t *nh;

    INSIST(namehook != NULL && DNS_ADBNAMEHOOK_VALID(*namehook));
    nh = *namehook;
    *namehook = NULL;

    INSIST(nh->entry == NULL);
    INSIST(!ISC_LINK_LINKED(nh, link));

    nh->magic = 0;
    isc_mempool_put(adb->nhmp, nh);
}

static inline dns_adbzoneinfo_t *
new_adbzoneinfo(dns_adb_t *adb, dns_name_t *zone)
{
    dns_adbzoneinfo_t *zi;

    zi = isc_mempool_get(adb->zimp);
    if (zi == NULL)
        return (NULL);

    dns_name_init(&zi->zone, NULL);
    if (dns_name_dup(zone, adb->mctx, &zi->zone) != ISC_R_SUCCESS) {
        isc_mempool_put(adb->zimp, zi);
        return (NULL);
    }

    zi->magic = DNS_ADBZONEINFO_MAGIC;
    zi->lame_timer = 0;
    ISC_LINK_INIT(zi, link);

    return (zi);
}

static inline void
free_adbzoneinfo(dns_adb_t *adb, dns_adbzoneinfo_t **zoneinfo)
{
    dns_adbzoneinfo_t *zi;

    INSIST(zoneinfo != NULL && DNS_ADBZONEINFO_VALID(*zoneinfo));
    zi = *zoneinfo;
    *zoneinfo = NULL;

    INSIST(!ISC_LINK_LINKED(zi, link));

    dns_name_free(&zi->zone, adb->mctx);

    zi->magic = 0;

    isc_mempool_put(adb->zimp, zi);
}

static inline dns_adbentry_t *
new_adbentry(dns_adb_t *adb)
{
    dns_adbentry_t *e;
    isc_uint32_t r;

    e = isc_mempool_get(adb->emp);
    if (e == NULL)
        return (NULL);

    e->magic = DNS_ADBENTRY_MAGIC;
    e->lock_bucket = DNS_ADB_INVALIDBUCKET;
    e->refcnt = 0;
    e->flags = 0;
    e->goodness = 0;
    isc_random_get(&adb->rand, &r);
    e->srtt = (r & 0x1f) + 1;
    ISC_LIST_INIT(e->zoneinfo);
    ISC_LINK_INIT(e, link);

    return (e);
}

static inline void
free_adbentry(dns_adb_t *adb, dns_adbentry_t **entry)
{
    dns_adbentry_t *e;
    dns_adbzoneinfo_t *zi;

    INSIST(entry != NULL && DNS_ADBENTRY_VALID(*entry));
    e = *entry;
    *entry = NULL;

    INSIST(e->lock_bucket == DNS_ADB_INVALIDBUCKET);
    INSIST(e->refcnt == 0);
    INSIST(!ISC_LINK_LINKED(e, link));

    e->magic = 0;

    zi = ISC_LIST_HEAD(e->zoneinfo);
    while (zi != NULL) {
        ISC_LIST_UNLINK(e->zoneinfo, zi, link);
        free_adbzoneinfo(adb, &zi);
        zi = ISC_LIST_HEAD(e->zoneinfo);
    }

    isc_mempool_put(adb->emp, e);
}

static inline dns_adbhandle_t *
new_adbhandle(dns_adb_t *adb)
{
    dns_adbhandle_t *h;
    isc_result_t result;

    h = isc_mempool_get(adb->ahmp);
    if (h == NULL)
        return (NULL);

    /*
     * public members
     */
    h->magic = 0;
    h->adb = adb;
    h->query_pending = ISC_FALSE;
    h->partial_result = ISC_FALSE;
    h->result = ISC_R_UNEXPECTED;
    ISC_LIST_INIT(h->list);
    ISC_LINK_INIT(h, next);
    h->name_bucket = DNS_ADB_INVALIDBUCKET;
    h->adbname = NULL;

    /*
     * private members
     */
    result = isc_mutex_init(&h->lock);
    if (result != ISC_R_SUCCESS) {
        UNEXPECTED_ERROR(__FILE__, __LINE__,
                 "isc_mutex_init failed in new_adbhandle()");
        isc_mempool_put(adb->ahmp, h);
        return (NULL);
    }
    ISC_LINK_INIT(h, link);

    ISC_EVENT_INIT(&h->event, sizeof (isc_event_t), 0, 0, 0, NULL, NULL,
               NULL, NULL, h);

    h->magic = DNS_ADBHANDLE_MAGIC;
    return (h);
}

static inline dns_adbfetch_t *
new_adbfetch(dns_adb_t *adb)
{
    dns_adbfetch_t *f;

    f = isc_mempool_get(adb->afmp);
    if (f == NULL)
        return (NULL);

    f->magic = 0;
    f->namehook = NULL;
    f->entry = NULL;
    f->fetch = NULL;

    f->namehook = new_adbnamehook(adb, NULL);
    if (f->namehook == NULL)
        goto err;

    f->entry = new_adbentry(adb);
    if (f->entry == NULL)
        goto err;

    dns_rdataset_init(&f->rdataset);
    ISC_LINK_INIT(f, link);

    f->magic = DNS_ADBFETCH_MAGIC;

    return (f);

 err:
    if (f->namehook != NULL)
        free_adbnamehook(adb, &f->namehook);
    if (f->entry != NULL)
        free_adbentry(adb, &f->entry);
    isc_mempool_put(adb->afmp, f);
    return (NULL);
}

static inline void
free_adbfetch(dns_adb_t *adb, dns_adbfetch_t **fetch)
{
    dns_adbfetch_t *f;

    INSIST(fetch != NULL && DNS_ADBFETCH_VALID(*fetch));
    f = *fetch;
    *fetch = NULL;

    INSIST(!ISC_LINK_LINKED(f, link));

    f->magic = 0;

    if (f->namehook != NULL)
        free_adbnamehook(adb, &f->namehook);
    if (f->entry != NULL)
        free_adbentry(adb, &f->entry);

    if (dns_rdataset_isassociated(&f->rdataset))
        dns_rdataset_disassociate(&f->rdataset);

    isc_mempool_put(adb->afmp, f);
}

static inline void
free_adbhandle(dns_adb_t *adb, dns_adbhandle_t **handlep)
{
    dns_adbhandle_t *handle;

    INSIST(handlep != NULL && DNS_ADBHANDLE_VALID(*handlep));
    handle = *handlep;
    *handlep = NULL;

    INSIST(ISC_LIST_EMPTY(handle->list));
    INSIST(!ISC_LINK_LINKED(handle, next));
    INSIST(!ISC_LINK_LINKED(handle, link));
    INSIST(handle->name_bucket == DNS_ADB_INVALIDBUCKET);
    INSIST(handle->adbname == NULL);

    handle->magic = 0;

    isc_mutex_destroy(&handle->lock);
    isc_mempool_put(adb->ahmp, handle);
}

/*
 * Copy bits from the entry into the newly allocated addrinfo.  The entry
 * must be locked, and the reference count must be bumped up by one
 * if this function returns a valid pointer.
 */
static inline dns_adbaddrinfo_t *
new_adbaddrinfo(dns_adb_t *adb, dns_adbentry_t *entry)
{
    dns_adbaddrinfo_t *ai;

    ai = isc_mempool_get(adb->aimp);
    if (ai == NULL)
        return (NULL);

    ai->magic = DNS_ADBADDRINFO_MAGIC;
    ai->sockaddr = &entry->sockaddr;
    ai->goodness = entry->goodness;
    ai->srtt = entry->srtt;
    ai->flags = entry->flags;
    ai->entry = entry;
    ISC_LINK_INIT(ai, link);

    return (ai);
}

static inline void
free_adbaddrinfo(dns_adb_t *adb, dns_adbaddrinfo_t **ainfo)
{
    dns_adbaddrinfo_t *ai;

    INSIST(ainfo != NULL && DNS_ADBADDRINFO_VALID(*ainfo));
    ai = *ainfo;
    *ainfo = NULL;

    INSIST(ai->sockaddr == NULL);
    INSIST(ai->entry == NULL);
    INSIST(!ISC_LINK_LINKED(ai, link));

    ai->magic = 0;

    isc_mempool_put(adb->aimp, ai);
}

/*
 * Search for the name.  NOTE:  The bucket is kept locked on both
 * success and failure, so it must always be unlocked by the caller!
 *
 * On the first call to this function, *bucketp must be set to
 * DNS_ADB_INVALIDBUCKET.
 */
static inline dns_adbname_t *
find_name_and_lock(dns_adb_t *adb, dns_name_t *name, int *bucketp)
{
    dns_adbname_t *adbname;
    int bucket;

    bucket = dns_name_hash(name, ISC_FALSE);
    bucket &= (DNS_ADBNAMELIST_LENGTH - 1);

    if (*bucketp == DNS_ADB_INVALIDBUCKET) {
        LOCK(&adb->namelocks[bucket]);
        *bucketp = bucket;
    } else if (*bucketp != bucket) {
        UNLOCK(&adb->namelocks[*bucketp]);
        LOCK(&adb->namelocks[bucket]);
        *bucketp = bucket;
    }

    adbname = ISC_LIST_HEAD(adb->names[bucket]);
    while (adbname != NULL) {
        if (dns_name_equal(name, &adbname->name))
            return (adbname);
        adbname = ISC_LIST_NEXT(adbname, link);
    }

    return (NULL);
}

/*
 * Search for the address.  NOTE:  The bucket is kept locked on both
 * success and failure, so it must always be unlocked by the caller.
 *
 * On the first call to this function, *bucketp must be set to
 * DNS_ADB_INVALIDBUCKET.  This will cause a lock to occur.  On
 * later calls (within the same "lock path") it can be left alone, so
 * if this function is called multiple times locking is only done if
 * the bucket changes.
 */
static inline dns_adbentry_t *
find_entry_and_lock(dns_adb_t *adb, isc_sockaddr_t *addr, int *bucketp)
{
    dns_adbentry_t *entry;
    int bucket;

    bucket = isc_sockaddr_hash(addr, ISC_TRUE);
    bucket &= (DNS_ADBENTRYLIST_LENGTH - 1);

    if (*bucketp == DNS_ADB_INVALIDBUCKET) {
        LOCK(&adb->entrylocks[bucket]);
        *bucketp = bucket;
    } else if (*bucketp != bucket) {
        UNLOCK(&adb->entrylocks[*bucketp]);
        LOCK(&adb->entrylocks[bucket]);
        *bucketp = bucket;
    }

    entry = ISC_LIST_HEAD(adb->entries[bucket]);
    while (entry != NULL) {
        if (isc_sockaddr_equal(addr, &entry->sockaddr))
            return (entry);
        entry = ISC_LIST_NEXT(entry, link);
    }

    return (NULL);
}

/*
 * Entry bucket MUST be locked!
 */
static isc_boolean_t
entry_is_bad_for_zone(dns_adb_t *adb, dns_adbentry_t *entry, dns_name_t *zone,
              isc_stdtime_t now)
{
    dns_adbzoneinfo_t *zi, *next_zi;
    isc_boolean_t is_bad;

    is_bad = ISC_FALSE;

    zi = ISC_LIST_HEAD(entry->zoneinfo);
    if (zi == NULL)
        return (ISC_FALSE);
    while (zi != NULL) {
        next_zi = ISC_LIST_NEXT(zi, link);

        /*
         * Has the entry expired?
         */
        if (zi->lame_timer < now) {
            ISC_LIST_UNLINK(entry->zoneinfo, zi, link);
            free_adbzoneinfo(adb, &zi);
        }

        /*
         * Order tests from least to most expensive.
         */
        if (zi != NULL && !is_bad) {
            if (dns_name_equal(zone, &zi->zone))
                is_bad = ISC_TRUE;
        }

        zi = next_zi;
    }

    return (is_bad);
}

static void
copy_namehook_list(dns_adb_t *adb, dns_adbhandle_t *handle,
           dns_adbname_t *name, dns_name_t *zone, isc_stdtime_t now)
{
    dns_adbnamehook_t *namehook;
    dns_adbaddrinfo_t *addrinfo;
    int bucket;

    handle->query_pending = ISC_FALSE;
    bucket = DNS_ADB_INVALIDBUCKET;

    namehook = ISC_LIST_HEAD(name->namehooks);
    while (namehook != NULL) {
        bucket = namehook->entry->lock_bucket;
        LOCK(&adb->entrylocks[bucket]);
        if (entry_is_bad_for_zone(adb, namehook->entry, zone, now))
            goto next;
        addrinfo = new_adbaddrinfo(adb, namehook->entry);
        if (addrinfo == NULL) {
            handle->partial_result = ISC_TRUE;
            handle->result = ISC_R_NOMEMORY;
            goto out;
        }
        /*
         * Found a valid entry.  Add it to the handle's list.
         */
        inc_entry_refcnt(adb, namehook->entry, ISC_FALSE);
        ISC_LIST_APPEND(handle->list, addrinfo, link);
        addrinfo = NULL;
    next:
        UNLOCK(&adb->entrylocks[bucket]);
        bucket = DNS_ADB_INVALIDBUCKET;
        namehook = ISC_LIST_NEXT(namehook, link);
    }

    handle->result = ISC_R_SUCCESS; /* all were copied */
 out:
    if (bucket != DNS_ADB_INVALIDBUCKET)
        UNLOCK(&adb->entrylocks[bucket]);
}

static void
shutdown_task(isc_task_t *task, isc_event_t *ev)
{
    dns_adb_t *adb;
    isc_result_t result;

    adb = ev->arg;
    INSIST(DNS_ADB_VALID(adb));

    /*
     * Kill the timer, and then the ADB itself.  Note that this implies
     * that this task was the one scheduled to get timer events.  If
     * this is not true (and it is unfortunate there is no way to INSIST()
     * this) baddness will occur.
     */
    LOCK(&adb->lock);
    isc_timer_detach(&adb->timer);
    UNLOCK(&adb->lock);
    destroy(adb);

    isc_event_free(&ev);
}

/*
 * ADB must be locked
 */
static void
cleanup(dns_adb_t *adb)
{
}

static void
timer_cleanup(isc_task_t *task, isc_event_t *ev)
{
    dns_adb_t *adb;
    isc_result_t result;

    adb = ev->arg;
    INSIST(DNS_ADB_VALID(adb));

    printf("Tick!\n");

    LOCK(&adb->lock);

    /*
     * Call our cleanup routine.
     */
    cleanup(adb);

    /*
     * Reset the timer.
     */
    result = isc_timer_reset(adb->timer, isc_timertype_once, NULL,
                 &adb->tick_interval, ISC_FALSE);

    UNLOCK(&adb->lock);

    isc_event_free(&ev);
}

static void
destroy(dns_adb_t *adb)
{
    adb->magic = 0;

    /*
     * The timer is already dead, from the task's shutdown callback.
     */
    isc_task_detach(&adb->task);

    isc_mempool_destroy(&adb->nmp);
    isc_mempool_destroy(&adb->nhmp);
    isc_mempool_destroy(&adb->zimp);
    isc_mempool_destroy(&adb->emp);
    isc_mempool_destroy(&adb->ahmp);
    isc_mempool_destroy(&adb->aimp);
    isc_mempool_destroy(&adb->afmp);

    isc_mutexblock_destroy(adb->entrylocks, DNS_ADBENTRYLIST_LENGTH);
    isc_mutexblock_destroy(adb->namelocks, DNS_ADBNAMELIST_LENGTH);

    isc_mutex_destroy(&adb->lock);
    isc_mutex_destroy(&adb->mplock);

    isc_random_invalidate(&adb->rand);

    isc_mem_put(adb->mctx, adb, sizeof (dns_adb_t));
}


/*
 * Public functions.
 */

isc_result_t
dns_adb_create(isc_mem_t *mem, dns_view_t *view, isc_timermgr_t *timermgr,
           isc_taskmgr_t *taskmgr, dns_adb_t **newadb)
{
    dns_adb_t *adb;
    isc_result_t result;
    int i;

    REQUIRE(mem != NULL);
    REQUIRE(view != NULL);
    REQUIRE(timermgr != NULL);
    REQUIRE(taskmgr != NULL);
    REQUIRE(newadb != NULL && *newadb == NULL);

    adb = isc_mem_get(mem, sizeof (dns_adb_t));
    if (adb == NULL)
        return (ISC_R_NOMEMORY);

    /*
     * Initialize things here that cannot fail, and especially things
     * that must be NULL for the error return to work properly.
     */
    adb->magic = 0;
    adb->erefcnt = 1;
    adb->irefcnt = 0;
    adb->nmp = NULL;
    adb->nhmp = NULL;
    adb->zimp = NULL;
    adb->emp = NULL;
    adb->ahmp = NULL;
    adb->aimp = NULL;
    adb->afmp = NULL;
    adb->task = NULL;
    adb->timer = NULL;
    adb->mctx = mem;
    adb->view = view;
    adb->timermgr = timermgr;
    adb->taskmgr = taskmgr;

    result = isc_random_init(&adb->rand);
    if (result != ISC_R_SUCCESS)
        goto fail0a;

    result = isc_mutex_init(&adb->lock);
    if (result != ISC_R_SUCCESS)
        goto fail0b;
    result = isc_mutex_init(&adb->mplock);
    if (result != ISC_R_SUCCESS)
        goto fail0c;

    /*
     * Initialize the bucket locks for names and elements.
     * May as well initialize the list heads, too.
     */
    result = isc_mutexblock_init(adb->namelocks, DNS_ADBNAMELIST_LENGTH);
    if (result != ISC_R_SUCCESS)
        goto fail1;
    for (i = 0 ; i < DNS_ADBNAMELIST_LENGTH ; i++) {
        ISC_LIST_INIT(adb->names[i]);
        adb->name_sd[i] = ISC_FALSE;
        adb->name_refcnt[i] = 0;
        adb->irefcnt++;
    }
    for (i = 0 ; i < DNS_ADBENTRYLIST_LENGTH ; i++)
        ISC_LIST_INIT(adb->entries[i]);
    result = isc_mutexblock_init(adb->entrylocks, DNS_ADBENTRYLIST_LENGTH);
    if (result != ISC_R_SUCCESS)
        goto fail2;

    /*
     * Memory pools
     */
#define MPINIT(t, p, l, n) do { \
    result = isc_mempool_create(mem, sizeof (t), &(p)); \
    if (result != ISC_R_SUCCESS) \
        goto fail3; \
    isc_mempool_setfreemax((p), FREE_ITEMS); \
    isc_mempool_setfillcount((p), FILL_COUNT); \
    isc_mempool_setname((p), n); \
    if (l) \
        isc_mempool_associatelock((p), &adb->mplock); \
} while (0)

    MPINIT(dns_adbname_t, adb->nmp, ISC_TRUE, "adbname");
    MPINIT(dns_adbnamehook_t, adb->nhmp, ISC_TRUE, "adbnamehook");
    MPINIT(dns_adbzoneinfo_t, adb->zimp, ISC_TRUE, "adbzoneinfo");
    MPINIT(dns_adbentry_t, adb->emp, ISC_TRUE, "adbentry");
    MPINIT(dns_adbhandle_t, adb->ahmp, ISC_TRUE, "adbhandle");
    MPINIT(dns_adbaddrinfo_t, adb->aimp, ISC_TRUE, "adbaddrinfo");
    MPINIT(dns_adbfetch_t, adb->afmp, ISC_TRUE, "adbfetch");

#undef MPINIT

    /*
     * Allocate a timer and a task for our periodic cleanup.
     */
    result = isc_task_create(adb->taskmgr, adb->mctx, 0, &adb->task);
    if (result != ISC_R_SUCCESS)
        goto fail3;
    result = isc_task_onshutdown(adb->task, shutdown_task, adb);
    isc_interval_set(&adb->tick_interval, CLEAN_SECONDS, 0);
    result = isc_timer_create(adb->timermgr, isc_timertype_once,
                  NULL, &adb->tick_interval, adb->task,
                  timer_cleanup, adb, &adb->timer);
    if (result != ISC_R_SUCCESS)
        goto fail3;

    /*
     * Normal return.
     */
    adb->magic = DNS_ADB_MAGIC;
    *newadb = adb;
    return (ISC_R_SUCCESS);

 fail3:
    if (adb->task != NULL)
        isc_task_detach(&adb->task);
    if (adb->timer != NULL)
        isc_timer_detach(&adb->timer);

    /* clean up entrylocks */
    isc_mutexblock_destroy(adb->entrylocks, DNS_ADBENTRYLIST_LENGTH);

 fail2: /* clean up namelocks */
    isc_mutexblock_destroy(adb->namelocks, DNS_ADBNAMELIST_LENGTH);

 fail1: /* clean up only allocated memory */
    if (adb->nmp != NULL)
        isc_mempool_destroy(&adb->nmp);
    if (adb->nhmp != NULL)
        isc_mempool_destroy(&adb->nhmp);
    if (adb->zimp != NULL)
        isc_mempool_destroy(&adb->zimp);
    if (adb->emp != NULL)
        isc_mempool_destroy(&adb->emp);
    if (adb->ahmp != NULL)
        isc_mempool_destroy(&adb->ahmp);
    if (adb->aimp != NULL)
        isc_mempool_destroy(&adb->aimp);
    if (adb->aimp != NULL)
        isc_mempool_destroy(&adb->afmp);

 fail0d:
    isc_mutex_destroy(&adb->mplock);
 fail0c:
    isc_mutex_destroy(&adb->lock);
 fail0b:
    isc_random_invalidate(&adb->rand);
 fail0a:
    isc_mem_put(mem, adb, sizeof (dns_adb_t));

    return (result);
}

void
dns_adb_detach(dns_adb_t **adbx)
{
    dns_adb_t *adb;
    isc_boolean_t kill;

    REQUIRE(adbx != NULL && DNS_ADB_VALID(*adbx));

    adb = *adbx;
    *adbx = NULL;

    LOCK(&adb->lock);
    dec_adb_erefcnt(adb, ISC_FALSE);
    if (adb->erefcnt == 0)
        shutdown_names(adb, ISC_TRUE);
    kill = check_exit(adb);

    if (kill)
        isc_task_shutdown(adb->task);
    UNLOCK(&adb->lock);
}

isc_result_t
dns_adb_lookup(dns_adb_t *adb, isc_task_t *task, isc_taskaction_t action,
           void *arg, dns_name_t *name, dns_name_t *zone,
           isc_stdtime_t now, dns_adbhandle_t **handlep)
{
    dns_adbhandle_t *handle;
    dns_adbname_t *adbname;
    int bucket;
    isc_result_t result;
    isc_boolean_t attach_to_task;

    REQUIRE(DNS_ADB_VALID(adb));
    if (task != NULL) {
        REQUIRE(action != NULL);
    }
    REQUIRE(name != NULL);
    REQUIRE(zone != NULL);
    REQUIRE(handlep != NULL && *handlep == NULL);

    attach_to_task = ISC_FALSE;
    result = ISC_R_UNEXPECTED;

    if (now == 0) {
        result = isc_stdtime_get(&now);
        if (result != ISC_R_SUCCESS)
            return (result);
    }

    /*
     * Look up the name in our internal database.
     *
     * Possibilities:  Note that these are not always exclusive.
     *
     *  No name found.  In this case, allocate a new name header and
     *  an initial namehook or two.  If any of these allocations
     *  fail, clean up and return ISC_R_NOMEMORY.
     *
     *  Name found, valid addresses present.  Allocate one addrinfo
     *  structure for each found and append it to the linked list
     *  of addresses for this header.
     *
     *  Name found, queries pending.  In this case, if a task was
     *  passed in, allocate a job id, attach it to the name's job
     *  list and remember to tell the caller that there will be
     *  more info coming later.
     */

    handle = new_adbhandle(adb);
    if (handle == NULL) {
        result = ISC_R_NOMEMORY;
        goto out;
    }

    /*
     * Look things up in our database first.
     */
    bucket = DNS_ADB_INVALIDBUCKET;
    adbname = find_name_and_lock(adb, name, &bucket);
    if (adb->name_sd[bucket]) {
            result = ISC_R_SHUTTINGDOWN;
            goto fail;
    }

    /*
     * Found!  Run through the name and copy out the bits we are
     * interested in.  If we cannot copy at least one address, return
     * ISC_R_NOMEMORY, otherwise copy out what we can and set the
     * missing_data bit in the header.
     */
 again:
    if (adbname != NULL) {
        copy_namehook_list(adb, handle, adbname, zone, now);
        if (handle->result == ISC_R_NOMEMORY
            && ISC_LIST_EMPTY(handle->list)) {
            result = ISC_R_NOMEMORY;
            goto fail;
        }

        /*
         * Attach to the name's query list if there are queries
         * already running.
         */
        if (!ISC_LIST_EMPTY(adbname->fetches) && (task != NULL)) {
            handle->adbname = adbname;
            handle->name_bucket = bucket;
            ISC_LIST_APPEND(adbname->handles, handle, link);
            attach_to_task = ISC_TRUE;
        }

        result = ISC_R_SUCCESS;
        goto out;
    }

    /*
     * Nothing found.  Allocate a new adbname structure for this name
     * and look in the database for details.  If the database has
     * nothing useful, start a fetch if we can.
     */
    adbname = new_adbname(adb, name);
    if (adbname == NULL) {
        result = ISC_R_NOMEMORY;
        goto fail;
    }

    /*
     * Try to populate the name from the database and/or start fetches.
     * If this function returns ISC_R_SUCCESS at least ONE new bit
     * of data was added, and/or fetches were started.  If nothing new
     * can ever be found it will return DNS_R_NOMEMORY more than likely.
     */
    result = construct_name(adb, handle, name, zone, adbname, bucket, now);
    if (result == ISC_R_SUCCESS) {
        ISC_LIST_PREPEND(adb->names[bucket], adbname, link);
        adb->name_refcnt[bucket]++;
        if (adbname->partial_result)
            handle->partial_result = ISC_TRUE;
        goto again;
    }

    /*
     * If anything other than success is returned, free the name
     * (since it will have nothing useful in it) and return via the
     * failure return.
     */
 fail:
    free_adbhandle(adb, &handle);

    /*
     * If the name isn't on a list it means we allocated it here, and it
     * should be killed.
     */
    if (adbname != NULL) {
        INSIST(!ISC_LINK_LINKED(adbname, link));
        free_adbname(adb, &adbname);
    }

    /*
     * "goto out" if the handle will be returned to the caller.  This
     * is a non-fatal return, since it will give the caller a handle
     * at the very least.
     */
 out:
    if (handle != NULL) {
        *handlep = handle;

        if (attach_to_task) {
            isc_task_t *taskp;

            taskp = NULL;
            isc_task_attach(task, &taskp);
            handle->event.sender = taskp;
            handle->event.action = action;
            handle->event.arg = arg;
        }
    }

    if (bucket != DNS_ADB_INVALIDBUCKET)
        UNLOCK(&adb->namelocks[bucket]);

    return (result);
}

isc_result_t
dns_adb_deletename(dns_adb_t *adb, dns_name_t *host)
{
    int name_bucket;
    dns_adbname_t *name;
    isc_boolean_t decr_adbrefcnt;

    REQUIRE(DNS_ADB_VALID(adb));
    REQUIRE(host != NULL);

    name = NULL;

    /*
     * Find the name.
     */
    name_bucket = DNS_ADB_INVALIDBUCKET;
    name = find_name_and_lock(adb, host, &name_bucket);
    if (name == NULL) {
        UNLOCK(&adb->namelocks[name_bucket]);
        return (ISC_R_NOTFOUND);
    }

    /*
     * If any handles are attached to this name, notify them that things
     * are going away by canceling their requests.
     */
    clean_handles_at_name(name, DNS_EVENT_ADBNAMEDELETED);

    /* XXX TODO:
     * If fetches are running for this name, cancel them all.
     */

    /*
     * Loop through the name and kill any namehooks and entries they
     * point to.
     */
    clean_namehooks_at_name(adb, name);

    ISC_LIST_UNLINK(adb->names[name_bucket], name, link);
    free_adbname(adb, &name);

    INSIST(adb->name_refcnt[name_bucket] > 0);
    adb->name_refcnt[name_bucket]--;

    decr_adbrefcnt = ISC_FALSE;
    if (adb->name_sd[name_bucket] && (adb->name_refcnt[name_bucket] == 0))
        decr_adbrefcnt = ISC_TRUE;

    if (name_bucket != DNS_ADB_INVALIDBUCKET)
        UNLOCK(&adb->namelocks[name_bucket]);

    if (decr_adbrefcnt)
        dec_adb_irefcnt(adb, ISC_TRUE);

    return (DNS_R_SUCCESS);
}

isc_result_t
dns_adb_insert(dns_adb_t *adb, dns_name_t *host, isc_sockaddr_t *addr)
{
    dns_adbname_t *name;
    isc_boolean_t free_name;
    dns_adbentry_t *entry;
    isc_boolean_t free_entry;
    dns_adbnamehook_t *namehook;
    isc_boolean_t free_namehook;
    int name_bucket, addr_bucket; /* unlock if != DNS_ADB_INVALIDBUCKET */
    isc_result_t result;

    REQUIRE(DNS_ADB_VALID(adb));
    REQUIRE(host != NULL);
    REQUIRE(addr != NULL);

    name = NULL;
    free_name = ISC_FALSE;
    entry = NULL;
    free_entry = ISC_FALSE;
    namehook = NULL;
    free_namehook = ISC_FALSE;
    result = ISC_R_UNEXPECTED;

    /*
     * First, see if the host is already in the database.  If it is,
     * don't make a new host entry.  If not, copy the name and name's
     * contents into our structure and allocate what we'll need
     * to attach things together.
     */
    name_bucket = DNS_ADB_INVALIDBUCKET;
    name = find_name_and_lock(adb, host, &name_bucket);
    if (name == NULL) {
        name = new_adbname(adb, host);
        if (name == NULL) {
            result = ISC_R_NOMEMORY;
            goto out;
        }
        free_name = ISC_TRUE;
    }

    /*
     * Now, while keeping the name locked, search for the address.
     * Three possibilities:  One, the address doesn't exist.
     * Two, the address exists, but we aren't linked to it.
     * Three, the address exists and we are linked to it.
     * (1) causes a new entry and namehook to be created.
     * (2) causes only a new namehook.
     * (3) is an error.
     */
    addr_bucket = DNS_ADB_INVALIDBUCKET;
    entry = find_entry_and_lock(adb, addr, &addr_bucket);
    /*
     * Case (1):  new entry and namehook.
     */
    if (entry == NULL) {
        entry = new_adbentry(adb);
        if (entry == NULL) {
            result = ISC_R_NOMEMORY;
            goto out;
        }
        free_entry = ISC_TRUE;
    }

    /*
     * Case (3):  entry exists, we're linked.
     */
    namehook = ISC_LIST_HEAD(name->namehooks);
    while (namehook != NULL) {
        if (namehook->entry == entry) {
            result = ISC_R_EXISTS;
            goto out;
        }
        namehook = ISC_LIST_NEXT(namehook, link);
    }

    /*
     * Case (2):  New namehook, link to entry from above.
     */
    namehook = new_adbnamehook(adb, entry);
    if (namehook == NULL) {
        result = ISC_R_NOMEMORY;
        goto out;
    }
    free_namehook = ISC_TRUE;
    ISC_LIST_APPEND(name->namehooks, namehook, link);

    entry->lock_bucket = addr_bucket;
    inc_entry_refcnt(adb, entry, ISC_FALSE);
    entry->sockaddr = *addr;

    /*
     * If needed, string up the name and entry.
     */
    if (!ISC_LINK_LINKED(name, link)) {
        ISC_LIST_PREPEND(adb->names[name_bucket], name, link);
        adb->name_refcnt[name_bucket]++;
    }
    if (!ISC_LINK_LINKED(entry, link))
        ISC_LIST_PREPEND(adb->entries[addr_bucket], entry, link);
    UNLOCK(&adb->namelocks[name_bucket]);
    name_bucket = DNS_ADB_INVALIDBUCKET;
    UNLOCK(&adb->entrylocks[addr_bucket]);
    addr_bucket = DNS_ADB_INVALIDBUCKET;

    return (ISC_R_SUCCESS);

 out:
    if (free_name)
        free_adbname(adb, &name);
    if (free_entry)
        isc_mempool_put(adb->emp, entry);
    if (free_namehook)
        isc_mempool_put(adb->nhmp, namehook);
    if (name_bucket != DNS_ADB_INVALIDBUCKET)
        UNLOCK(&adb->namelocks[name_bucket]);
    if (addr_bucket != DNS_ADB_INVALIDBUCKET)
        UNLOCK(&adb->entrylocks[addr_bucket]);

    return (result);
}

void
dns_adb_done(dns_adbhandle_t **handlep)
{
    dns_adbhandle_t *handle;
    dns_adbentry_t *entry;
    dns_adbaddrinfo_t *ai;
    int bucket;
    dns_adb_t *adb;
    isc_boolean_t kill;

    REQUIRE(handlep != NULL && DNS_ADBHANDLE_VALID(*handlep));
    handle = *handlep;
    *handlep = NULL;

    LOCK(&handle->lock);

    adb = handle->adb;
    REQUIRE(DNS_ADB_VALID(adb));
    REQUIRE(!ISC_LINK_LINKED(handle, next));

    bucket = handle->name_bucket;
    if (bucket == DNS_ADB_INVALIDBUCKET)
        goto cleanup;

    /*
     * We need to get the adbname's lock to unlink the handle.
     */
    violate_locking_hierarchy(&handle->lock, &adb->namelocks[bucket]);
    bucket = handle->name_bucket;
    if (bucket != DNS_ADB_INVALIDBUCKET) {
        ISC_LIST_UNLINK(handle->adbname->handles, handle, link);
        handle->adbname = NULL;
        handle->name_bucket = DNS_ADB_INVALIDBUCKET;
    }
    UNLOCK(&adb->namelocks[bucket]);
    bucket = DNS_ADB_INVALIDBUCKET;

 cleanup:
    UNLOCK(&handle->lock);

    /*
     * The handle doesn't exist on any list, and nothing is locked.
     * Return the handle to the memory pool, and decrement the adb's
     * reference count.
     */
    ai = ISC_LIST_HEAD(handle->list);
    while (ai != NULL) {
        ISC_LIST_UNLINK(handle->list, ai, link);
        entry = ai->entry;
        ai->entry = NULL;
        ai->sockaddr = NULL;
        INSIST(DNS_ADBENTRY_VALID(entry));
        dec_entry_refcnt(adb, entry, ISC_TRUE);
        free_adbaddrinfo(adb, &ai);
        ai = ISC_LIST_HEAD(handle->list);
    }

    LOCK(&adb->lock);
    free_adbhandle(adb, &handle);
    kill = check_exit(adb);

    if (kill)
        isc_task_shutdown(adb->task);
    UNLOCK(&adb->lock);
}

void
dns_adb_dump(dns_adb_t *adb, FILE *f)
{
    int i;
    isc_sockaddr_t *sa;
    dns_adbname_t *name;
    dns_adbentry_t *entry;
    char tmp[512];
    const char *tmpp;

    REQUIRE(DNS_ADB_VALID(adb));
    REQUIRE(f != NULL);

    /*
     * Lock the adb itself, lock all the name buckets, then lock all
     * the entry buckets.  This should put the adb into a state where
     * nothing can change, so we can iterate through everything and
     * print at our leasure.
     */

    LOCK(&adb->lock);

    fprintf(f, "ADB %p DUMP:\n", adb);
    fprintf(f, "erefcnt %u, irefcnt %u\n", adb->erefcnt, adb->irefcnt);

    for (i = 0 ; i < DNS_ADBNAMELIST_LENGTH ; i++)
        LOCK(&adb->namelocks[i]);
    for (i = 0 ; i < DNS_ADBENTRYLIST_LENGTH ; i++)
        LOCK(&adb->entrylocks[i]);

    /*
     * Dump the names
     */
    fprintf(f, "Names:\n");
    for (i = 0 ; i < DNS_ADBNAMELIST_LENGTH ; i++) {
        name = ISC_LIST_HEAD(adb->names[i]);
        if (name == NULL)
            continue;
        fprintf(f, "Name bucket %d:\n", i);
        while (name != NULL) {
            fprintf(f, "name %p\n", name);
            if (!DNS_ADBNAME_VALID(name))
                fprintf(f, "\tMAGIC %08x\n", name->magic);
            fprintf(f, "\t");
            print_dns_name(f, &name->name);
            fprintf(f, "\n");
            print_namehook_list(f, name);
            print_handle_list(f, name);
            fprintf(f, "\n");

            name = ISC_LIST_NEXT(name, link);
        }
    }

    /*
     * Dump the entries
     */
    fprintf(f, "Entries:\n");
    for (i = 0 ; i < DNS_ADBENTRYLIST_LENGTH ; i++) {
        entry = ISC_LIST_HEAD(adb->entries[i]);
        if (entry == NULL)
            continue;
        fprintf(f, "Entry bucket %d:\n", i);
        while (entry != NULL) {
            if (!DNS_ADBENTRY_VALID(entry))
                fprintf(f, "\tMAGIC %08x\n", entry->magic);
            if (entry->lock_bucket != i)
                fprintf(f, "\tWRONG BUCKET!  lock_bucket %d\n",
                    entry->lock_bucket);

            sa = &entry->sockaddr;
            switch (sa->type.sa.sa_family) {
            case AF_INET:
                tmpp = inet_ntop(AF_INET,
                         &sa->type.sin.sin_addr,
                         tmp, sizeof tmp);
                break;
            case AF_INET6:
                tmpp = inet_ntop(AF_INET6,
                         &sa->type.sin6.sin6_addr,
                         tmp, sizeof tmp);
                break;
            default:
                tmpp = "UnkFamily";
            }

            if (tmpp == NULL)
                tmpp = "CANNOT TRANSLATE ADDRESS!";

            fprintf(f, "\t%p: refcnt %u flags %08x goodness %d"
                " srtt %u addr %s\n",
                entry, entry->refcnt, entry->flags,
                entry->goodness, entry->srtt, tmpp);

            entry = ISC_LIST_NEXT(entry, link);
        }
    }

    /*
     * Unlock everything
     */
    for (i = 0 ; i < DNS_ADBENTRYLIST_LENGTH ; i++)
        UNLOCK(&adb->entrylocks[i]);
    for (i = 0 ; i < DNS_ADBNAMELIST_LENGTH ; i++)
        UNLOCK(&adb->namelocks[i]);
    UNLOCK(&adb->lock);
}

void
dns_adb_dumphandle(dns_adb_t *adb, dns_adbhandle_t *handle, FILE *f)
{
    char tmp[512];
    const char *tmpp;
    dns_adbaddrinfo_t *ai;
    isc_sockaddr_t *sa;

    /*
     * Not used currently, in the API Just In Case we
     * want to dump out the name and/or entries too.
     */
    (void)adb;

    LOCK(&handle->lock);

    fprintf(f, "Handle %p\n", handle);
    fprintf(f, "\tquery_pending %d, result %d (%s)\n",
        handle->query_pending, handle->result,
        isc_result_totext(handle->result));
    fprintf(f, "\tname_bucket %d, name %p, event sender %p\n",
        handle->name_bucket, handle->adbname, handle->event.sender);

    ai = ISC_LIST_HEAD(handle->list);
    if (ai != NULL)
        fprintf(f, "\tAddresses:\n");
    while (ai != NULL) {
        sa = ai->sockaddr;
        switch (sa->type.sa.sa_family) {
        case AF_INET:
            tmpp = inet_ntop(AF_INET, &sa->type.sin.sin_addr,
                     tmp, sizeof tmp);
            break;
        case AF_INET6:
            tmpp = inet_ntop(AF_INET6, &sa->type.sin6.sin6_addr,
                     tmp, sizeof tmp);
            break;
        default:
            tmpp = "UnkFamily";
        }

        if (tmpp == NULL)
            tmpp = "CANNOT TRANSLATE ADDRESS!";

        fprintf(f, "\t\tentry %p, flags %08x goodness %d"
            " srtt %u addr %s\n",
            ai->entry, ai->flags, ai->goodness, ai->srtt, tmpp);

        ai = ISC_LIST_NEXT(ai, link);
    }

    UNLOCK(&handle->lock);
}

static void
print_dns_name(FILE *f, dns_name_t *name)
{
    char buf[257];
    isc_buffer_t b;

    INSIST(f != NULL);

    memset(buf, 0, sizeof (buf));
    isc_buffer_init(&b, buf, sizeof (buf) - 1, ISC_BUFFERTYPE_TEXT);

    dns_name_totext(name, ISC_FALSE, &b);
    fprintf(f, buf); /* safe, since names < 256 chars, and we memset */
}

static void
print_namehook_list(FILE *f, dns_adbname_t *n)
{
    dns_adbnamehook_t *nh;

    nh = ISC_LIST_HEAD(n->namehooks);
    while (nh != NULL) {
        fprintf(f, "\t\tHook %p -> entry %p\n", nh, nh->entry);
        nh = ISC_LIST_NEXT(nh, link);
    }
}

static void
print_handle_list(FILE *f, dns_adbname_t *name)
{
    dns_adbhandle_t *handle;

    handle = ISC_LIST_HEAD(name->handles);
    while (handle != NULL) {
        fprintf(f, "\t\tHandle %p\n", handle);
        handle = ISC_LIST_NEXT(handle, link);
    }
}

/*
 * On entry, "bucket" refers to a locked name bucket, "handle" is not NULL,
 * and "name" is the name we are looking for.  We will allocate an adbname
 * and return a pointer to it in *adbnamep.
 *
 * If we return ISC_R_SUCCESS, the new name will have been allocated, and
 * perhaps some namehooks will have been filled in with valid entries, and
 * perhaps some fetches have been started.
 */
static isc_result_t
construct_name(dns_adb_t *adb, dns_adbhandle_t *handle, dns_name_t *name,
           dns_name_t *zone, dns_adbname_t *adbname, int bucket,
           isc_stdtime_t now)
{
    dns_adbnamehook_t *nh;
    isc_result_t result;
    int addr_bucket;
    isc_boolean_t return_success;
    isc_boolean_t use_hints;
    dns_rdataset_t rdataset;
    dns_rdata_t rdata;
    struct in_addr ina;
    isc_sockaddr_t sockaddr;
    dns_adbentry_t *foundentry;  /* NO CLEAN UP! */

    INSIST(DNS_ADB_VALID(adb));
    INSIST(DNS_ADBHANDLE_VALID(handle));
    INSIST(name != NULL);
    INSIST(DNS_ADBNAME_VALID(adbname));
    INSIST(bucket != DNS_ADB_INVALIDBUCKET);

    if (adb->view == NULL)
        return (ISC_R_NOTIMPLEMENTED);

    result = ISC_R_UNEXPECTED;
    addr_bucket = DNS_ADB_INVALIDBUCKET;
    return_success = ISC_FALSE;
    nh = NULL;

    use_hints = dns_name_equal(zone, dns_rootname);
    dns_rdataset_init(&rdataset);
    adbname->partial_result = ISC_FALSE;

    result = dns_view_find(adb->view, name, dns_rdatatype_a,
                   now, DNS_DBFIND_GLUEOK, use_hints,
                   &rdataset, NULL);
    switch (result) {
    case DNS_R_GLUE:
    case DNS_R_HINT:
    case DNS_R_SUCCESS:
        result = dns_rdataset_first(&rdataset);
        while (result == ISC_R_SUCCESS) {
            nh = new_adbnamehook(adb, NULL);
            if (nh == NULL) {
                adbname->partial_result = ISC_TRUE;
                result = ISC_R_NOMEMORY;
                goto fail;
            }
            dns_rdataset_current(&rdataset, &rdata);
            INSIST(rdata.length == 4);
            memcpy(&ina.s_addr, rdata.data, 4);
            isc_sockaddr_fromin(&sockaddr, &ina, 53);

            foundentry = find_entry_and_lock(adb, &sockaddr,
                             &addr_bucket);
            if (foundentry == NULL) {
                dns_adbentry_t *entry;

                entry = new_adbentry(adb);
                if (entry == NULL) {
                    adbname->partial_result = ISC_TRUE;
                    result = ISC_R_NOMEMORY;
                    goto fail;
                }

                entry->sockaddr = sockaddr;
                entry->refcnt = 1;
                entry->lock_bucket = addr_bucket;

                nh->entry = entry;

                ISC_LIST_APPEND(adb->entries[addr_bucket],
                        entry, link);
            } else {
                foundentry->refcnt++;
                nh->entry = foundentry;
            }

            ISC_LIST_APPEND(adbname->namehooks, nh, link);
            nh = NULL;

            return_success = ISC_TRUE;

            result = dns_rdataset_next(&rdataset);
        }
    }

 fail:
    if (dns_rdataset_isassociated(&rdataset))
        dns_rdataset_disassociate(&rdataset);

    if (nh != NULL)
        free_adbnamehook(adb, &nh);

    if (addr_bucket != DNS_ADB_INVALIDBUCKET)
        UNLOCK(&adb->entrylocks[addr_bucket]);

    if (return_success)
        return (ISC_R_SUCCESS);
    return (result);
}

isc_result_t
dns_adb_marklame(dns_adb_t *adb, dns_adbaddrinfo_t *addr, dns_name_t *zone,
         isc_stdtime_t expire_time)
{
    dns_adbzoneinfo_t *zi;
    int bucket;

    REQUIRE(DNS_ADB_VALID(adb));
    REQUIRE(DNS_ADBADDRINFO_VALID(addr));
    REQUIRE(zone != NULL);

    zi = new_adbzoneinfo(adb, zone);
    if (zi == NULL)
        return (ISC_R_NOMEMORY);

    zi->lame_timer = expire_time;

    bucket = addr->entry->lock_bucket;
    LOCK(&adb->entrylocks[bucket]);
    ISC_LIST_PREPEND(addr->entry->zoneinfo, zi, link);
    UNLOCK(&adb->entrylocks[bucket]);

    return (ISC_R_SUCCESS);
}

void
dns_adb_adjustgoodness(dns_adb_t *adb, dns_adbaddrinfo_t *addr,
               int goodness_adjustment)
{
    int bucket;
    int old_goodness, new_goodness;

    REQUIRE(DNS_ADB_VALID(adb));
    REQUIRE(DNS_ADBADDRINFO_VALID(addr));

    if (goodness_adjustment == 0)
        return;

    bucket = addr->entry->lock_bucket;
    LOCK(&adb->entrylocks[bucket]);

    old_goodness = addr->entry->goodness;

    if (goodness_adjustment > 0) {
        if (old_goodness > INT_MAX - goodness_adjustment)
            new_goodness = INT_MAX;
        else
            new_goodness = old_goodness + goodness_adjustment;
    } else {
        if (old_goodness < INT_MIN - goodness_adjustment)
            new_goodness = INT_MAX;
        else
            new_goodness = old_goodness + goodness_adjustment;
    }

    addr->entry->goodness = new_goodness;
    addr->goodness = new_goodness;

    UNLOCK(&adb->entrylocks[bucket]);
}

void
dns_adb_adjustsrtt(dns_adb_t *adb, dns_adbaddrinfo_t *addr,
           unsigned int rtt, unsigned int factor)
{
    int bucket;
    unsigned int new_srtt;

    REQUIRE(DNS_ADB_VALID(adb));
    REQUIRE(DNS_ADBADDRINFO_VALID(addr));

    if (factor == 0)
        factor = 4;

    bucket = addr->entry->lock_bucket;
    LOCK(&adb->entrylocks[bucket]);

    new_srtt = (addr->entry->srtt * (factor - 1) + rtt) / factor;
    addr->entry->srtt = new_srtt;
    addr->srtt = new_srtt;

    UNLOCK(&adb->entrylocks[bucket]);
}