lib/dns/dispatch.c

	dispatch.c revision 42b48d11ca7b296324d7a8a98cdbf0070b0deb1d
/*
 * Copyright (C) 2004  Internet Systems Consortium, Inc. ("ISC")
 * Copyright (C) 1999-2003  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 ISC DISCLAIMS ALL WARRANTIES WITH
 * REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY
 * AND FITNESS.  IN NO EVENT SHALL ISC 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.
 */

/* $Id: dispatch.c,v 1.117 2004/04/15 01:58:24 marka Exp $ */

#include <config.h>

#include <stdlib.h>

#include <isc/entropy.h>
#include <isc/lfsr.h>
#include <isc/mem.h>
#include <isc/mutex.h>
#include <isc/print.h>
#include <isc/string.h>
#include <isc/task.h>
#include <isc/util.h>

#include <dns/acl.h>
#include <dns/dispatch.h>
#include <dns/events.h>
#include <dns/log.h>
#include <dns/message.h>
#include <dns/portlist.h>
#include <dns/tcpmsg.h>
#include <dns/types.h>

typedef ISC_LIST(dns_dispentry_t)   dns_displist_t;

typedef struct dns_qid {
    unsigned int    magic;
    unsigned int    qid_nbuckets;   /* hash table size */
    unsigned int    qid_increment;  /* id increment on collision */
    isc_mutex_t lock;
    isc_lfsr_t  qid_lfsr1;  /* state generator info */
    isc_lfsr_t  qid_lfsr2;  /* state generator info */
    dns_displist_t  *qid_table; /* the table itself */
} dns_qid_t;

struct dns_dispatchmgr {
    /* Unlocked. */
    unsigned int            magic;
    isc_mem_t              *mctx;
    dns_acl_t              *blackhole;
    dns_portlist_t             *portlist;

    /* Locked by "lock". */
    isc_mutex_t         lock;
    unsigned int            state;
    ISC_LIST(dns_dispatch_t)    list;

    /* locked by buffer lock */
    dns_qid_t           *qid;
    isc_mutex_t         buffer_lock;
    unsigned int            buffers;    /* allocated buffers */
    unsigned int            buffersize; /* size of each buffer */
    unsigned int            maxbuffers; /* max buffers */

    /* Locked internally. */
    isc_mutex_t         pool_lock;
    isc_mempool_t              *epool;  /* memory pool for events */
    isc_mempool_t              *rpool;  /* memory pool for replies */
    isc_mempool_t              *dpool;  /* dispatch allocations */
    isc_mempool_t              *bpool;  /* memory pool for buffers */

    isc_entropy_t              *entropy; /* entropy source */
};

#define MGR_SHUTTINGDOWN        0x00000001U
#define MGR_IS_SHUTTINGDOWN(l)  (((l)->state & MGR_SHUTTINGDOWN) != 0)

#define IS_PRIVATE(d)   (((d)->attributes & DNS_DISPATCHATTR_PRIVATE) != 0)

struct dns_dispentry {
    unsigned int            magic;
    dns_dispatch_t             *disp;
    dns_messageid_t         id;
    unsigned int            bucket;
    isc_sockaddr_t          host;
    isc_task_t             *task;
    isc_taskaction_t        action;
    void                   *arg;
    isc_boolean_t           item_out;
    ISC_LIST(dns_dispatchevent_t)   items;
    ISC_LINK(dns_dispentry_t)   link;
};

#define INVALID_BUCKET      (0xffffdead)

struct dns_dispatch {
    /* Unlocked. */
    unsigned int        magic;      /* magic */
    dns_dispatchmgr_t      *mgr;        /* dispatch manager */
    isc_task_t         *task;       /* internal task */
    isc_socket_t           *socket;     /* isc socket attached to */
    isc_sockaddr_t      local;      /* local address */
    unsigned int        maxrequests;    /* max requests */
    isc_event_t        *ctlevent;

    /* Locked by mgr->lock. */
    ISC_LINK(dns_dispatch_t) link;

    /* Locked by "lock". */
    isc_mutex_t     lock;       /* locks all below */
    isc_sockettype_t    socktype;
    unsigned int        attributes;
    unsigned int        refcount;   /* number of users */
    dns_dispatchevent_t    *failsafe_ev;    /* failsafe cancel event */
    unsigned int        shutting_down : 1,
                shutdown_out : 1,
                connected : 1,
                tcpmsg_valid : 1,
                recv_pending : 1; /* is a recv() pending? */
    isc_result_t        shutdown_why;
    unsigned int        requests;   /* how many requests we have */
    unsigned int        tcpbuffers; /* allocated buffers */
    dns_tcpmsg_t        tcpmsg;     /* for tcp streams */
    dns_qid_t       *qid;
};

#define QID_MAGIC       ISC_MAGIC('Q', 'i', 'd', ' ')
#define VALID_QID(e)        ISC_MAGIC_VALID((e), QID_MAGIC)

#define RESPONSE_MAGIC      ISC_MAGIC('D', 'r', 's', 'p')
#define VALID_RESPONSE(e)   ISC_MAGIC_VALID((e), RESPONSE_MAGIC)

#define DISPATCH_MAGIC      ISC_MAGIC('D', 'i', 's', 'p')
#define VALID_DISPATCH(e)   ISC_MAGIC_VALID((e), DISPATCH_MAGIC)

#define DNS_DISPATCHMGR_MAGIC   ISC_MAGIC('D', 'M', 'g', 'r')
#define VALID_DISPATCHMGR(e)    ISC_MAGIC_VALID((e), DNS_DISPATCHMGR_MAGIC)

#define DNS_QID(disp) ((disp)->socktype == isc_sockettype_tcp) ? \
               (disp)->qid : (disp)->mgr->qid
/*
 * Statics.
 */
static dns_dispentry_t *bucket_search(dns_qid_t *, isc_sockaddr_t *,
                      dns_messageid_t, unsigned int);
static isc_boolean_t destroy_disp_ok(dns_dispatch_t *);
static void destroy_disp(isc_task_t *task, isc_event_t *event);
static void udp_recv(isc_task_t *, isc_event_t *);
static void tcp_recv(isc_task_t *, isc_event_t *);
static inline void startrecv(dns_dispatch_t *);
static dns_messageid_t dns_randomid(dns_qid_t *);
static isc_uint32_t dns_hash(dns_qid_t *, isc_sockaddr_t *, dns_messageid_t);
static void free_buffer(dns_dispatch_t *disp, void *buf, unsigned int len);
static void *allocate_udp_buffer(dns_dispatch_t *disp);
static inline void free_event(dns_dispatch_t *disp, dns_dispatchevent_t *ev);
static inline dns_dispatchevent_t *allocate_event(dns_dispatch_t *disp);
static void do_cancel(dns_dispatch_t *disp, dns_dispentry_t *resp);
static dns_dispentry_t *linear_first(dns_qid_t *disp);
static dns_dispentry_t *linear_next(dns_qid_t *disp,
                    dns_dispentry_t *resp);
static void dispatch_free(dns_dispatch_t **dispp);
static isc_result_t dispatch_createudp(dns_dispatchmgr_t *mgr,
                       isc_socketmgr_t *sockmgr,
                       isc_taskmgr_t *taskmgr,
                       isc_sockaddr_t *localaddr,
                       unsigned int maxrequests,
                       unsigned int attributes,
                       dns_dispatch_t **dispp);
static isc_boolean_t destroy_mgr_ok(dns_dispatchmgr_t *mgr);
static void destroy_mgr(dns_dispatchmgr_t **mgrp);
static isc_result_t qid_allocate(dns_dispatchmgr_t *mgr, unsigned int buckets,
                 unsigned int increment, dns_qid_t **qidp);
static void qid_destroy(isc_mem_t *mctx, dns_qid_t **qidp);

#define LVL(x) ISC_LOG_DEBUG(x)

static void
mgr_log(dns_dispatchmgr_t *mgr, int level, const char *fmt, ...)
     ISC_FORMAT_PRINTF(3, 4);

static void
mgr_log(dns_dispatchmgr_t *mgr, int level, const char *fmt, ...) {
    char msgbuf[2048];
    va_list ap;

    if (! isc_log_wouldlog(dns_lctx, level))
        return;

    va_start(ap, fmt);
    vsnprintf(msgbuf, sizeof(msgbuf), fmt, ap);
    va_end(ap);

    isc_log_write(dns_lctx,
              DNS_LOGCATEGORY_DISPATCH, DNS_LOGMODULE_DISPATCH,
              level, "dispatchmgr %p: %s", mgr, msgbuf);
}

static void
dispatch_log(dns_dispatch_t *disp, int level, const char *fmt, ...)
     ISC_FORMAT_PRINTF(3, 4);

static void
dispatch_log(dns_dispatch_t *disp, int level, const char *fmt, ...) {
    char msgbuf[2048];
    va_list ap;

    if (! isc_log_wouldlog(dns_lctx, level))
        return;

    va_start(ap, fmt);
    vsnprintf(msgbuf, sizeof(msgbuf), fmt, ap);
    va_end(ap);

    isc_log_write(dns_lctx,
              DNS_LOGCATEGORY_DISPATCH, DNS_LOGMODULE_DISPATCH,
              level, "dispatch %p: %s", disp, msgbuf);
}

static void
request_log(dns_dispatch_t *disp, dns_dispentry_t *resp,
        int level, const char *fmt, ...)
     ISC_FORMAT_PRINTF(4, 5);

static void
request_log(dns_dispatch_t *disp, dns_dispentry_t *resp,
        int level, const char *fmt, ...)
{
    char msgbuf[2048];
    char peerbuf[256];
    va_list ap;

    if (! isc_log_wouldlog(dns_lctx, level))
        return;

    va_start(ap, fmt);
    vsnprintf(msgbuf, sizeof(msgbuf), fmt, ap);
    va_end(ap);

    if (VALID_RESPONSE(resp)) {
        isc_sockaddr_format(&resp->host, peerbuf, sizeof(peerbuf));
        isc_log_write(dns_lctx, DNS_LOGCATEGORY_DISPATCH,
                  DNS_LOGMODULE_DISPATCH, level,
                  "dispatch %p response %p %s: %s", disp, resp,
                  peerbuf, msgbuf);
    } else {
        isc_log_write(dns_lctx, DNS_LOGCATEGORY_DISPATCH,
                  DNS_LOGMODULE_DISPATCH, level,
                  "dispatch %p req/resp %p: %s", disp, resp,
                  msgbuf);
    }
}

static void
reseed_lfsr(isc_lfsr_t *lfsr, void *arg)
{
    dns_dispatchmgr_t *mgr = arg;
    isc_result_t result;
    isc_uint32_t val;

    REQUIRE(VALID_DISPATCHMGR(mgr));

    if (mgr->entropy != NULL) {
        result = isc_entropy_getdata(mgr->entropy, &val, sizeof(val),
                         NULL, 0);
        INSIST(result == ISC_R_SUCCESS);
        lfsr->count = (val & 0x1f) + 32;
        lfsr->state = val;
        return;
    }

    lfsr->count = (random() & 0x1f) + 32;   /* From 32 to 63 states */
    lfsr->state = random();
}

/*
 * Return an unpredictable message ID.
 */
static dns_messageid_t
dns_randomid(dns_qid_t *qid) {
    isc_uint32_t id;

    id = isc_lfsr_generate32(&qid->qid_lfsr1, &qid->qid_lfsr2);

    return (dns_messageid_t)(id & 0xFFFF);
}

/*
 * Return a hash of the destination and message id.
 */
static isc_uint32_t
dns_hash(dns_qid_t *qid, isc_sockaddr_t *dest, dns_messageid_t id) {
    unsigned int ret;

    ret = isc_sockaddr_hash(dest, ISC_TRUE);
    ret ^= id;
    ret %= qid->qid_nbuckets;

    INSIST(ret < qid->qid_nbuckets);

    return (ret);
}

/*
 * Find the first entry in 'qid'.  Returns NULL if there are no entries.
 */
static dns_dispentry_t *
linear_first(dns_qid_t *qid) {
    dns_dispentry_t *ret;
    unsigned int bucket;

    bucket = 0;

    while (bucket < qid->qid_nbuckets) {
        ret = ISC_LIST_HEAD(qid->qid_table[bucket]);
        if (ret != NULL)
            return (ret);
        bucket++;
    }

    return (NULL);
}

/*
 * Find the next entry after 'resp' in 'qid'.  Return NULL if there are
 * no more entries.
 */
static dns_dispentry_t *
linear_next(dns_qid_t *qid, dns_dispentry_t *resp) {
    dns_dispentry_t *ret;
    unsigned int bucket;

    ret = ISC_LIST_NEXT(resp, link);
    if (ret != NULL)
        return (ret);

    bucket = resp->bucket;
    bucket++;
    while (bucket < qid->qid_nbuckets) {
        ret = ISC_LIST_HEAD(qid->qid_table[bucket]);
        if (ret != NULL)
            return (ret);
        bucket++;
    }

    return (NULL);
}

/*
 * The dispatch must be locked.
 */
static isc_boolean_t
destroy_disp_ok(dns_dispatch_t *disp)
{
    if (disp->refcount != 0)
        return (ISC_FALSE);

    if (disp->recv_pending != 0)
        return (ISC_FALSE);

    if (disp->shutting_down == 0)
        return (ISC_FALSE);

    return (ISC_TRUE);
}


/*
 * Called when refcount reaches 0 (and safe to destroy).
 *
 * The dispatcher must not be locked.
 * The manager must be locked.
 */
static void
destroy_disp(isc_task_t *task, isc_event_t *event) {
    dns_dispatch_t *disp;
    dns_dispatchmgr_t *mgr;
    isc_boolean_t killmgr;

    INSIST(event->ev_type == DNS_EVENT_DISPATCHCONTROL);

    UNUSED(task);

    disp = event->ev_arg;
    mgr = disp->mgr;

    LOCK(&mgr->lock);
    ISC_LIST_UNLINK(mgr->list, disp, link);

    dispatch_log(disp, LVL(90),
             "shutting down; detaching from sock %p, task %p",
             disp->socket, disp->task);

    isc_socket_detach(&disp->socket);
    isc_task_detach(&disp->task);
    isc_event_free(&event);

    dispatch_free(&disp);

    killmgr = destroy_mgr_ok(mgr);
    UNLOCK(&mgr->lock);
    if (killmgr)
        destroy_mgr(&mgr);
}


/*
 * Find an entry for query ID 'id' and socket address 'dest' in 'qid'.
 * Return NULL if no such entry exists.
 */
static dns_dispentry_t *
bucket_search(dns_qid_t *qid, isc_sockaddr_t *dest, dns_messageid_t id,
          unsigned int bucket)
{
    dns_dispentry_t *res;

    REQUIRE(bucket < qid->qid_nbuckets);

    res = ISC_LIST_HEAD(qid->qid_table[bucket]);

    while (res != NULL) {
        if ((res->id == id) && isc_sockaddr_equal(dest, &res->host))
            return (res);
        res = ISC_LIST_NEXT(res, link);
    }

    return (NULL);
}

static void
free_buffer(dns_dispatch_t *disp, void *buf, unsigned int len) {
    INSIST(buf != NULL && len != 0);


    switch (disp->socktype) {
    case isc_sockettype_tcp:
        INSIST(disp->tcpbuffers > 0);
        disp->tcpbuffers--;
        isc_mem_put(disp->mgr->mctx, buf, len);
        break;
    case isc_sockettype_udp:
        LOCK(&disp->mgr->buffer_lock);
        INSIST(disp->mgr->buffers > 0);
        INSIST(len == disp->mgr->buffersize);
        disp->mgr->buffers--;
        isc_mempool_put(disp->mgr->bpool, buf);
        UNLOCK(&disp->mgr->buffer_lock);
        break;
    default:
        INSIST(0);
        break;
    }
}

static void *
allocate_udp_buffer(dns_dispatch_t *disp) {
    void *temp;

    LOCK(&disp->mgr->buffer_lock);
    temp = isc_mempool_get(disp->mgr->bpool);

    if (temp != NULL)
        disp->mgr->buffers++;
    UNLOCK(&disp->mgr->buffer_lock);

    return (temp);
}

static inline void
free_event(dns_dispatch_t *disp, dns_dispatchevent_t *ev) {
    if (disp->failsafe_ev == ev) {
        INSIST(disp->shutdown_out == 1);
        disp->shutdown_out = 0;

        return;
    }

    isc_mempool_put(disp->mgr->epool, ev);
}

static inline dns_dispatchevent_t *
allocate_event(dns_dispatch_t *disp) {
    dns_dispatchevent_t *ev;

    ev = isc_mempool_get(disp->mgr->epool);
    if (ev == NULL)
        return (NULL);
    ISC_EVENT_INIT(ev, sizeof(*ev), 0, NULL, 0,
               NULL, NULL, NULL, NULL, NULL);

    return (ev);
}

/*
 * General flow:
 *
 * If I/O result == CANCELED or error, free the buffer.
 *
 * If query, free the buffer, restart.
 *
 * If response:
 *  Allocate event, fill in details.
 *      If cannot allocate, free buffer, restart.
 *  find target.  If not found, free buffer, restart.
 *  if event queue is not empty, queue.  else, send.
 *  restart.
 */
static void
udp_recv(isc_task_t *task, isc_event_t *ev_in) {
    isc_socketevent_t *ev = (isc_socketevent_t *)ev_in;
    dns_dispatch_t *disp = ev_in->ev_arg;
    dns_messageid_t id;
    isc_result_t dres;
    isc_buffer_t source;
    unsigned int flags;
    dns_dispentry_t *resp;
    dns_dispatchevent_t *rev;
    unsigned int bucket;
    isc_boolean_t killit;
    isc_boolean_t queue_response;
    dns_dispatchmgr_t *mgr;
    dns_qid_t *qid;
    isc_netaddr_t netaddr;
    int match;

    UNUSED(task);

    LOCK(&disp->lock);

    mgr = disp->mgr;
    qid = mgr->qid;

    dispatch_log(disp, LVL(90),
             "got packet: requests %d, buffers %d, recvs %d",
             disp->requests, disp->mgr->buffers, disp->recv_pending);

    if (ev->ev_type == ISC_SOCKEVENT_RECVDONE) {
        /*
         * Unless the receive event was imported from a listening
         * interface, in which case the event type is
         * DNS_EVENT_IMPORTRECVDONE, receive operation must be pending.
         */
        INSIST(disp->recv_pending != 0);
        disp->recv_pending = 0;
    }

    if (disp->shutting_down) {
        /*
         * This dispatcher is shutting down.
         */
        free_buffer(disp, ev->region.base, ev->region.length);

        isc_event_free(&ev_in);
        ev = NULL;

        killit = destroy_disp_ok(disp);
        UNLOCK(&disp->lock);
        if (killit)
            isc_task_send(disp->task, &disp->ctlevent);

        return;
    }

    if (ev->result != ISC_R_SUCCESS) {
        free_buffer(disp, ev->region.base, ev->region.length);

        if (ev->result != ISC_R_CANCELED)
            dispatch_log(disp, ISC_LOG_ERROR,
                     "odd socket result in udp_recv(): %s",
                     isc_result_totext(ev->result));

        UNLOCK(&disp->lock);
        isc_event_free(&ev_in);
        return;
    }

    /*
     * If this is from a blackholed address, drop it.
     */
    isc_netaddr_fromsockaddr(&netaddr, &ev->address);
    if (disp->mgr->blackhole != NULL &&
        dns_acl_match(&netaddr, NULL, disp->mgr->blackhole,
                  NULL, &match, NULL) == ISC_R_SUCCESS &&
        match > 0)
    {
        if (isc_log_wouldlog(dns_lctx, LVL(10))) {
            char netaddrstr[ISC_NETADDR_FORMATSIZE];
            isc_netaddr_format(&netaddr, netaddrstr,
                       sizeof(netaddrstr));
            dispatch_log(disp, LVL(10),
                     "blackholed packet from %s",
                     netaddrstr);
        }
        free_buffer(disp, ev->region.base, ev->region.length);
        goto restart;
    }

    /*
     * Peek into the buffer to see what we can see.
     */
    isc_buffer_init(&source, ev->region.base, ev->region.length);
    isc_buffer_add(&source, ev->n);
    dres = dns_message_peekheader(&source, &id, &flags);
    if (dres != ISC_R_SUCCESS) {
        free_buffer(disp, ev->region.base, ev->region.length);
        dispatch_log(disp, LVL(10), "got garbage packet");
        goto restart;
    }

    dispatch_log(disp, LVL(92),
             "got valid DNS message header, /QR %c, id %u",
             ((flags & DNS_MESSAGEFLAG_QR) ? '1' : '0'), id);

    /*
     * Look at flags.  If query, drop it. If response,
     * look to see where it goes.
     */
    queue_response = ISC_FALSE;
    if ((flags & DNS_MESSAGEFLAG_QR) == 0) {
        /* query */
        free_buffer(disp, ev->region.base, ev->region.length);
        goto restart;
    } else {
        /* response */
        bucket = dns_hash(qid, &ev->address, id);
        LOCK(&qid->lock);
        resp = bucket_search(qid, &ev->address, id, bucket);
        UNLOCK(&qid->lock);
        dispatch_log(disp, LVL(90),
                 "search for response in bucket %d: %s",
                 bucket, (resp == NULL ? "not found" : "found"));

        if (resp == NULL) {
            free_buffer(disp, ev->region.base, ev->region.length);
            goto restart;
        }
        queue_response = resp->item_out;
        rev = allocate_event(resp->disp);
        if (rev == NULL) {
            free_buffer(disp, ev->region.base, ev->region.length);
            goto restart;
        }
    }

    /*
     * At this point, rev contains the event we want to fill in, and
     * resp contains the information on the place to send it to.
     * Send the event off.
     */
    isc_buffer_init(&rev->buffer, ev->region.base, ev->region.length);
    isc_buffer_add(&rev->buffer, ev->n);
    rev->result = ISC_R_SUCCESS;
    rev->id = id;
    rev->addr = ev->address;
    rev->pktinfo = ev->pktinfo;
    rev->attributes = ev->attributes;
    if (queue_response) {
        ISC_LIST_APPEND(resp->items, rev, ev_link);
    } else {
        ISC_EVENT_INIT(rev, sizeof(*rev), 0, NULL,
                   DNS_EVENT_DISPATCH,
                   resp->action, resp->arg, resp, NULL, NULL);
        request_log(disp, resp, LVL(90),
                "[a] Sent event %p buffer %p len %d to task %p",
                rev, rev->buffer.base, rev->buffer.length,
                resp->task);
        resp->item_out = ISC_TRUE;
        isc_task_send(resp->task, ISC_EVENT_PTR(&rev));
    }

    /*
     * Restart recv() to get the next packet.
     */
 restart:
    startrecv(disp);

    UNLOCK(&disp->lock);

    isc_event_free(&ev_in);
}

/*
 * General flow:
 *
 * If I/O result == CANCELED, EOF, or error, notify everyone as the
 * various queues drain.
 *
 * If query, restart.
 *
 * If response:
 *  Allocate event, fill in details.
 *      If cannot allocate, restart.
 *  find target.  If not found, restart.
 *  if event queue is not empty, queue.  else, send.
 *  restart.
 */
static void
tcp_recv(isc_task_t *task, isc_event_t *ev_in) {
    dns_dispatch_t *disp = ev_in->ev_arg;
    dns_tcpmsg_t *tcpmsg = &disp->tcpmsg;
    dns_messageid_t id;
    isc_result_t dres;
    unsigned int flags;
    dns_dispentry_t *resp;
    dns_dispatchevent_t *rev;
    unsigned int bucket;
    isc_boolean_t killit;
    isc_boolean_t queue_response;
    dns_qid_t *qid;
    int level;
    char buf[ISC_SOCKADDR_FORMATSIZE];

    UNUSED(task);

    REQUIRE(VALID_DISPATCH(disp));

    qid = disp->qid;

    dispatch_log(disp, LVL(90),
             "got TCP packet: requests %d, buffers %d, recvs %d",
             disp->requests, disp->tcpbuffers, disp->recv_pending);

    LOCK(&disp->lock);

    INSIST(disp->recv_pending != 0);
    disp->recv_pending = 0;

    if (disp->refcount == 0) {
        /*
         * This dispatcher is shutting down.  Force cancelation.
         */
        tcpmsg->result = ISC_R_CANCELED;
    }

    if (tcpmsg->result != ISC_R_SUCCESS) {
        switch (tcpmsg->result) {
        case ISC_R_CANCELED:
            break;

        case ISC_R_EOF:
            dispatch_log(disp, LVL(90), "shutting down on EOF");
            do_cancel(disp, NULL);
            break;

        case ISC_R_CONNECTIONRESET:
            level = ISC_LOG_INFO;
            goto logit;

        default:
            level = ISC_LOG_ERROR;
        logit:
            isc_sockaddr_format(&tcpmsg->address, buf, sizeof(buf));
            dispatch_log(disp, level, "shutting down due to TCP "
                     "receive error: %s: %s", buf,
                     isc_result_totext(tcpmsg->result));
            do_cancel(disp, NULL);
            break;
        }

        /*
         * The event is statically allocated in the tcpmsg
         * structure, and destroy_disp() frees the tcpmsg, so we must
         * free the event *before* calling destroy_disp().
         */
        isc_event_free(&ev_in);

        disp->shutting_down = 1;
        disp->shutdown_why = tcpmsg->result;

        /*
         * If the recv() was canceled pass the word on.
         */
        killit = destroy_disp_ok(disp);
        UNLOCK(&disp->lock);
        if (killit)
            isc_task_send(disp->task, &disp->ctlevent);
        return;
    }

    dispatch_log(disp, LVL(90), "result %d, length == %d, addr = %p",
             tcpmsg->result,
             tcpmsg->buffer.length, tcpmsg->buffer.base);

    /*
     * Peek into the buffer to see what we can see.
     */
    dres = dns_message_peekheader(&tcpmsg->buffer, &id, &flags);
    if (dres != ISC_R_SUCCESS) {
        dispatch_log(disp, LVL(10), "got garbage packet");
        goto restart;
    }

    dispatch_log(disp, LVL(92),
             "got valid DNS message header, /QR %c, id %u",
             ((flags & DNS_MESSAGEFLAG_QR) ? '1' : '0'), id);

    /*
     * Allocate an event to send to the query or response client, and
     * allocate a new buffer for our use.
     */

    /*
     * Look at flags.  If query, drop it. If response,
     * look to see where it goes.
     */
    queue_response = ISC_FALSE;
    if ((flags & DNS_MESSAGEFLAG_QR) == 0) {
        /*
         * Query.
         */
        goto restart;
    } else {
        /*
         * Response.
         */
        bucket = dns_hash(qid, &tcpmsg->address, id);
        LOCK(&qid->lock);
        resp = bucket_search(qid, &tcpmsg->address, id, bucket);
        UNLOCK(&qid->lock);
        dispatch_log(disp, LVL(90),
                 "search for response in bucket %d: %s",
                 bucket, (resp == NULL ? "not found" : "found"));

        if (resp == NULL)
            goto restart;
        queue_response = resp->item_out;
        rev = allocate_event(disp);
        if (rev == NULL)
            goto restart;
    }

    /*
     * At this point, rev contains the event we want to fill in, and
     * resp contains the information on the place to send it to.
     * Send the event off.
     */
    dns_tcpmsg_keepbuffer(tcpmsg, &rev->buffer);
    disp->tcpbuffers++;
    rev->result = ISC_R_SUCCESS;
    rev->id = id;
    rev->addr = tcpmsg->address;
    if (queue_response) {
        ISC_LIST_APPEND(resp->items, rev, ev_link);
    } else {
        ISC_EVENT_INIT(rev, sizeof(*rev), 0, NULL, DNS_EVENT_DISPATCH,
                   resp->action, resp->arg, resp, NULL, NULL);
        request_log(disp, resp, LVL(90),
                "[b] Sent event %p buffer %p len %d to task %p",
                rev, rev->buffer.base, rev->buffer.length,
                resp->task);
        resp->item_out = ISC_TRUE;
        isc_task_send(resp->task, ISC_EVENT_PTR(&rev));
    }

    /*
     * Restart recv() to get the next packet.
     */
 restart:
    startrecv(disp);

    UNLOCK(&disp->lock);

    isc_event_free(&ev_in);
}

/*
 * disp must be locked.
 */
static void
startrecv(dns_dispatch_t *disp) {
    isc_result_t res;
    isc_region_t region;

    if (disp->shutting_down == 1)
        return;

    if ((disp->attributes & DNS_DISPATCHATTR_NOLISTEN) != 0)
        return;

    if (disp->recv_pending != 0)
        return;

    if (disp->mgr->buffers >= disp->mgr->maxbuffers)
        return;

    switch (disp->socktype) {
        /*
         * UDP reads are always maximal.
         */
    case isc_sockettype_udp:
        region.length = disp->mgr->buffersize;
        region.base = allocate_udp_buffer(disp);
        if (region.base == NULL)
            return;
        res = isc_socket_recv(disp->socket, &region, 1,
                      disp->task, udp_recv, disp);
        if (res != ISC_R_SUCCESS) {
            free_buffer(disp, region.base, region.length);
            disp->shutdown_why = res;
            disp->shutting_down = 1;
            do_cancel(disp, NULL);
            return;
        }
        INSIST(disp->recv_pending == 0);
        disp->recv_pending = 1;
        break;

    case isc_sockettype_tcp:
        res = dns_tcpmsg_readmessage(&disp->tcpmsg, disp->task,
                         tcp_recv, disp);
        if (res != ISC_R_SUCCESS) {
            disp->shutdown_why = res;
            disp->shutting_down = 1;
            do_cancel(disp, NULL);
            return;
        }
        INSIST(disp->recv_pending == 0);
        disp->recv_pending = 1;
        break;
    }
}

/*
 * Mgr must be locked when calling this function.
 */
static isc_boolean_t
destroy_mgr_ok(dns_dispatchmgr_t *mgr) {
    mgr_log(mgr, LVL(90),
        "destroy_mgr_ok: shuttingdown=%d, listnonempty=%d, "
        "epool=%d, rpool=%d, dpool=%d",
        MGR_IS_SHUTTINGDOWN(mgr), !ISC_LIST_EMPTY(mgr->list),
        isc_mempool_getallocated(mgr->epool),
        isc_mempool_getallocated(mgr->rpool),
        isc_mempool_getallocated(mgr->dpool));
    if (!MGR_IS_SHUTTINGDOWN(mgr))
        return (ISC_FALSE);
    if (!ISC_LIST_EMPTY(mgr->list))
        return (ISC_FALSE);
    if (isc_mempool_getallocated(mgr->epool) != 0)
        return (ISC_FALSE);
    if (isc_mempool_getallocated(mgr->rpool) != 0)
        return (ISC_FALSE);
    if (isc_mempool_getallocated(mgr->dpool) != 0)
        return (ISC_FALSE);

    return (ISC_TRUE);
}

/*
 * Mgr must be unlocked when calling this function.
 */
static void
destroy_mgr(dns_dispatchmgr_t **mgrp) {
    isc_mem_t *mctx;
    dns_dispatchmgr_t *mgr;

    mgr = *mgrp;
    *mgrp = NULL;

    mctx = mgr->mctx;

    mgr->magic = 0;
    mgr->mctx = NULL;
    DESTROYLOCK(&mgr->lock);
    mgr->state = 0;

    isc_mempool_destroy(&mgr->epool);
    isc_mempool_destroy(&mgr->rpool);
    isc_mempool_destroy(&mgr->dpool);
    isc_mempool_destroy(&mgr->bpool);

    DESTROYLOCK(&mgr->pool_lock);

    if (mgr->entropy != NULL)
        isc_entropy_detach(&mgr->entropy);
    if (mgr->qid != NULL)
        qid_destroy(mctx, &mgr->qid);

    DESTROYLOCK(&mgr->buffer_lock);

    if (mgr->blackhole != NULL)
        dns_acl_detach(&mgr->blackhole);

    if (mgr->portlist != NULL)
        dns_portlist_detach(&mgr->portlist);

    isc_mem_put(mctx, mgr, sizeof(dns_dispatchmgr_t));
    isc_mem_detach(&mctx);
}

static isc_result_t
create_socket(isc_socketmgr_t *mgr, isc_sockaddr_t *local,
          isc_socket_t **sockp)
{
    isc_socket_t *sock;
    isc_result_t result;

    sock = NULL;
    result = isc_socket_create(mgr, isc_sockaddr_pf(local),
                   isc_sockettype_udp, &sock);
    if (result != ISC_R_SUCCESS)
        return (result);

#ifndef ISC_ALLOW_MAPPED
    isc_socket_ipv6only(sock, ISC_TRUE);
#endif
    result = isc_socket_bind(sock, local);
    if (result != ISC_R_SUCCESS) {
        isc_socket_detach(&sock);
        return (result);
    }

    *sockp = sock;
    return (ISC_R_SUCCESS);
}

/*
 * Publics.
 */

isc_result_t
dns_dispatchmgr_create(isc_mem_t *mctx, isc_entropy_t *entropy,
               dns_dispatchmgr_t **mgrp)
{
    dns_dispatchmgr_t *mgr;
    isc_result_t result;

    REQUIRE(mctx != NULL);
    REQUIRE(mgrp != NULL && *mgrp == NULL);

    mgr = isc_mem_get(mctx, sizeof(dns_dispatchmgr_t));
    if (mgr == NULL)
        return (ISC_R_NOMEMORY);

    mgr->mctx = NULL;
    isc_mem_attach(mctx, &mgr->mctx);

    mgr->blackhole = NULL;
    mgr->portlist = NULL;

    result = isc_mutex_init(&mgr->lock);
    if (result != ISC_R_SUCCESS)
        goto deallocate;

    result = isc_mutex_init(&mgr->buffer_lock);
    if (result != ISC_R_SUCCESS)
        goto kill_lock;

    result = isc_mutex_init(&mgr->pool_lock);
    if (result != ISC_R_SUCCESS)
        goto kill_buffer_lock;

    mgr->epool = NULL;
    if (isc_mempool_create(mgr->mctx, sizeof(dns_dispatchevent_t),
                   &mgr->epool) != ISC_R_SUCCESS) {
        result = ISC_R_NOMEMORY;
        goto kill_pool_lock;
    }

    mgr->rpool = NULL;
    if (isc_mempool_create(mgr->mctx, sizeof(dns_dispentry_t),
                   &mgr->rpool) != ISC_R_SUCCESS) {
        result = ISC_R_NOMEMORY;
        goto kill_epool;
    }

    mgr->dpool = NULL;
    if (isc_mempool_create(mgr->mctx, sizeof(dns_dispatch_t),
                   &mgr->dpool) != ISC_R_SUCCESS) {
        result = ISC_R_NOMEMORY;
        goto kill_rpool;
    }

    isc_mempool_setname(mgr->epool, "dispmgr_epool");
    isc_mempool_setfreemax(mgr->epool, 1024);
    isc_mempool_associatelock(mgr->epool, &mgr->pool_lock);

    isc_mempool_setname(mgr->rpool, "dispmgr_rpool");
    isc_mempool_setfreemax(mgr->rpool, 1024);
    isc_mempool_associatelock(mgr->rpool, &mgr->pool_lock);

    isc_mempool_setname(mgr->dpool, "dispmgr_dpool");
    isc_mempool_setfreemax(mgr->dpool, 1024);
    isc_mempool_associatelock(mgr->dpool, &mgr->pool_lock);

    mgr->buffers = 0;
    mgr->buffersize = 0;
    mgr->maxbuffers = 0;
    mgr->bpool = NULL;
    mgr->entropy = NULL;
    mgr->qid = NULL;
    mgr->state = 0;
    ISC_LIST_INIT(mgr->list);
    mgr->magic = DNS_DISPATCHMGR_MAGIC;

    if (entropy != NULL)
        isc_entropy_attach(entropy, &mgr->entropy);

    *mgrp = mgr;
    return (ISC_R_SUCCESS);

 kill_rpool:
    isc_mempool_destroy(&mgr->rpool);
 kill_epool:
    isc_mempool_destroy(&mgr->epool);
 kill_pool_lock:
    DESTROYLOCK(&mgr->pool_lock);
 kill_buffer_lock:
    DESTROYLOCK(&mgr->buffer_lock);
 kill_lock:
    DESTROYLOCK(&mgr->lock);
 deallocate:
    isc_mem_put(mctx, mgr, sizeof(dns_dispatchmgr_t));
    isc_mem_detach(&mctx);

    return (result);
}

void
dns_dispatchmgr_setblackhole(dns_dispatchmgr_t *mgr, dns_acl_t *blackhole) {
    REQUIRE(VALID_DISPATCHMGR(mgr));
    if (mgr->blackhole != NULL)
        dns_acl_detach(&mgr->blackhole);
    dns_acl_attach(blackhole, &mgr->blackhole);
}

dns_acl_t *
dns_dispatchmgr_getblackhole(dns_dispatchmgr_t *mgr) {
    REQUIRE(VALID_DISPATCHMGR(mgr));
    return (mgr->blackhole);
}

void
dns_dispatchmgr_setblackportlist(dns_dispatchmgr_t *mgr,
                 dns_portlist_t *portlist)
{
    REQUIRE(VALID_DISPATCHMGR(mgr));
    if (mgr->portlist != NULL)
        dns_portlist_detach(&mgr->portlist);
    if (portlist != NULL)
        dns_portlist_attach(portlist, &mgr->portlist);
}

dns_portlist_t *
dns_dispatchmgr_getblackportlist(dns_dispatchmgr_t *mgr) {
    REQUIRE(VALID_DISPATCHMGR(mgr));
    return (mgr->portlist);
}

static isc_result_t
dns_dispatchmgr_setudp(dns_dispatchmgr_t *mgr,
            unsigned int buffersize, unsigned int maxbuffers,
            unsigned int buckets, unsigned int increment)
{
    isc_result_t result;

    REQUIRE(VALID_DISPATCHMGR(mgr));
    REQUIRE(buffersize >= 512 && buffersize < (64 * 1024));
    REQUIRE(maxbuffers > 0);
    REQUIRE(buckets < 2097169);  /* next prime > 65536 * 32 */
    REQUIRE(increment > buckets);

    /*
     * Keep some number of items around.  This should be a config
     * option.  For now, keep 8, but later keep at least two even
     * if the caller wants less.  This allows us to ensure certain
     * things, like an event can be "freed" and the next allocation
     * will always succeed.
     *
     * Note that if limits are placed on anything here, we use one
     * event internally, so the actual limit should be "wanted + 1."
     *
     * XXXMLG
     */

    if (maxbuffers < 8)
        maxbuffers = 8;

    LOCK(&mgr->buffer_lock);
    if (mgr->bpool != NULL) {
        isc_mempool_setmaxalloc(mgr->bpool, maxbuffers);
        mgr->maxbuffers = maxbuffers;
        UNLOCK(&mgr->buffer_lock);
        return (ISC_R_SUCCESS);
    }

    if (isc_mempool_create(mgr->mctx, buffersize,
                   &mgr->bpool) != ISC_R_SUCCESS) {
        return (ISC_R_NOMEMORY);
    }

    isc_mempool_setname(mgr->bpool, "dispmgr_bpool");
    isc_mempool_setmaxalloc(mgr->bpool, maxbuffers);
    isc_mempool_associatelock(mgr->bpool, &mgr->pool_lock);

    result = qid_allocate(mgr, buckets, increment, &mgr->qid);
    if (result != ISC_R_SUCCESS)
        goto cleanup;

    mgr->buffersize = buffersize;
    mgr->maxbuffers = maxbuffers;
    UNLOCK(&mgr->buffer_lock);
    return (ISC_R_SUCCESS);

 cleanup:
    isc_mempool_destroy(&mgr->bpool);
    UNLOCK(&mgr->buffer_lock);
    return (ISC_R_NOMEMORY);
}

void
dns_dispatchmgr_destroy(dns_dispatchmgr_t **mgrp) {
    dns_dispatchmgr_t *mgr;
    isc_boolean_t killit;

    REQUIRE(mgrp != NULL);
    REQUIRE(VALID_DISPATCHMGR(*mgrp));

    mgr = *mgrp;
    *mgrp = NULL;

    LOCK(&mgr->lock);
    mgr->state |= MGR_SHUTTINGDOWN;

    killit = destroy_mgr_ok(mgr);
    UNLOCK(&mgr->lock);

    mgr_log(mgr, LVL(90), "destroy: killit=%d", killit);

    if (killit)
        destroy_mgr(&mgr);
}

static isc_boolean_t
blacklisted(dns_dispatchmgr_t *mgr, isc_socket_t *sock) {
    isc_sockaddr_t sockaddr;
    isc_result_t result;

    if (mgr->portlist == NULL)
        return (ISC_FALSE);

    result = isc_socket_getsockname(sock, &sockaddr);
    if (result != ISC_R_SUCCESS)
        return (ISC_FALSE);

    if (mgr->portlist != NULL &&
        dns_portlist_match(mgr->portlist, isc_sockaddr_pf(&sockaddr),
                   isc_sockaddr_getport(&sockaddr)))
        return (ISC_TRUE);
    return (ISC_FALSE);
}

#define ATTRMATCH(_a1, _a2, _mask) (((_a1) & (_mask)) == ((_a2) & (_mask)))

static isc_boolean_t
local_addr_match(dns_dispatch_t *disp, isc_sockaddr_t *addr) {
    isc_sockaddr_t sockaddr;
    isc_result_t result;

    if (addr == NULL)
        return (ISC_TRUE);

    /*
     * Don't match wildcard ports against newly blacklisted ports.
     */
    if (disp->mgr->portlist != NULL &&
        isc_sockaddr_getport(addr) == 0 &&
        isc_sockaddr_getport(&disp->local) == 0 &&
        blacklisted(disp->mgr, disp->socket))
        return (ISC_FALSE);

    /*
     * Check if we match the binding <address,port>.
     * Wildcard ports match/fail here.
     */
    if (isc_sockaddr_equal(&disp->local, addr))
        return (ISC_TRUE);
    if (isc_sockaddr_getport(addr) == 0)
        return (ISC_FALSE);

    /*
     * Check if we match a bound wildcard port <address,port>.
     */
    if (!isc_sockaddr_eqaddr(&disp->local, addr))
        return (ISC_FALSE);
    result = isc_socket_getsockname(disp->socket, &sockaddr);
    if (result != ISC_R_SUCCESS)
        return (ISC_FALSE);

    return (isc_sockaddr_equal(&disp->local, &sockaddr));
}

/*
 * Requires mgr be locked.
 *
 * No dispatcher can be locked by this thread when calling this function.
 *
 *
 * NOTE:
 *  If a matching dispatcher is found, it is locked after this function
 *  returns, and must be unlocked by the caller.
 */
static isc_result_t
dispatch_find(dns_dispatchmgr_t *mgr, isc_sockaddr_t *local,
          unsigned int attributes, unsigned int mask,
          dns_dispatch_t **dispp)
{
    dns_dispatch_t *disp;
    isc_result_t result;

    /*
     * Make certain that we will not match a private dispatch.
     */
    attributes &= ~DNS_DISPATCHATTR_PRIVATE;
    mask |= DNS_DISPATCHATTR_PRIVATE;

    disp = ISC_LIST_HEAD(mgr->list);
    while (disp != NULL) {
        LOCK(&disp->lock);
        if ((disp->shutting_down == 0)
            && ATTRMATCH(disp->attributes, attributes, mask)
            && local_addr_match(disp, local))
            break;
        UNLOCK(&disp->lock);
        disp = ISC_LIST_NEXT(disp, link);
    }

    if (disp == NULL) {
        result = ISC_R_NOTFOUND;
        goto out;
    }

    *dispp = disp;
    result = ISC_R_SUCCESS;
 out:

    return (result);
}

static isc_result_t
qid_allocate(dns_dispatchmgr_t *mgr, unsigned int buckets,
         unsigned int increment, dns_qid_t **qidp)
{
    dns_qid_t *qid;
    unsigned int i;

    REQUIRE(VALID_DISPATCHMGR(mgr));
    REQUIRE(buckets < 2097169);  /* next prime > 65536 * 32 */
    REQUIRE(increment > buckets);
    REQUIRE(qidp != NULL && *qidp == NULL);

    qid = isc_mem_get(mgr->mctx, sizeof(*qid));
    if (qid == NULL)
        return (ISC_R_NOMEMORY);

    qid->qid_table = isc_mem_get(mgr->mctx,
                     buckets * sizeof(dns_displist_t));
    if (qid->qid_table == NULL) {
        isc_mem_put(mgr->mctx, qid, sizeof(*qid));
        return (ISC_R_NOMEMORY);
    }

    if (isc_mutex_init(&qid->lock) != ISC_R_SUCCESS) {
        UNEXPECTED_ERROR(__FILE__, __LINE__, "isc_mutex_init failed");
        isc_mem_put(mgr->mctx, qid->qid_table,
                buckets * sizeof(dns_displist_t));
        isc_mem_put(mgr->mctx, qid, sizeof(*qid));
        return (ISC_R_UNEXPECTED);
    }

    for (i = 0; i < buckets; i++)
        ISC_LIST_INIT(qid->qid_table[i]);

    qid->qid_nbuckets = buckets;
    qid->qid_increment = increment;
    qid->magic = QID_MAGIC;

    /*
     * Initialize to a 32-bit LFSR.  Both of these are from Applied
     * Cryptography.
     *
     * lfsr1:
     *  x^32 + x^7 + x^5 + x^3 + x^2 + x + 1
     *
     * lfsr2:
     *  x^32 + x^7 + x^6 + x^2 + 1
     */
    isc_lfsr_init(&qid->qid_lfsr1, 0, 32, 0x80000057U,
              0, reseed_lfsr, mgr);
    isc_lfsr_init(&qid->qid_lfsr2, 0, 32, 0x80000062U,
              0, reseed_lfsr, mgr);
    *qidp = qid;
    return (ISC_R_SUCCESS);
}

static void
qid_destroy(isc_mem_t *mctx, dns_qid_t **qidp) {
    dns_qid_t *qid;

    REQUIRE(qidp != NULL);
    qid = *qidp;

    REQUIRE(VALID_QID(qid));

    *qidp = NULL;
    qid->magic = 0;
    isc_mem_put(mctx, qid->qid_table,
            qid->qid_nbuckets * sizeof(dns_displist_t));
    DESTROYLOCK(&qid->lock);
    isc_mem_put(mctx, qid, sizeof(*qid));
}

/*
 * Allocate and set important limits.
 */
static isc_result_t
dispatch_allocate(dns_dispatchmgr_t *mgr, unsigned int maxrequests,
          dns_dispatch_t **dispp)
{
    dns_dispatch_t *disp;
    isc_result_t res;

    REQUIRE(VALID_DISPATCHMGR(mgr));
    REQUIRE(dispp != NULL && *dispp == NULL);

    /*
     * Set up the dispatcher, mostly.  Don't bother setting some of
     * the options that are controlled by tcp vs. udp, etc.
     */

    disp = isc_mempool_get(mgr->dpool);
    if (disp == NULL)
        return (ISC_R_NOMEMORY);

    disp->magic = 0;
    disp->mgr = mgr;
    disp->maxrequests = maxrequests;
    disp->attributes = 0;
    ISC_LINK_INIT(disp, link);
    disp->refcount = 1;
    disp->recv_pending = 0;
    memset(&disp->local, 0, sizeof(disp->local));
    disp->shutting_down = 0;
    disp->shutdown_out = 0;
    disp->connected = 0;
    disp->tcpmsg_valid = 0;
    disp->shutdown_why = ISC_R_UNEXPECTED;
    disp->requests = 0;
    disp->tcpbuffers = 0;
    disp->qid = NULL;

    if (isc_mutex_init(&disp->lock) != ISC_R_SUCCESS) {
        res = ISC_R_UNEXPECTED;
        UNEXPECTED_ERROR(__FILE__, __LINE__, "isc_mutex_init failed");
        goto deallocate;
    }

    disp->failsafe_ev = allocate_event(disp);
    if (disp->failsafe_ev == NULL) {
        res = ISC_R_NOMEMORY;
        goto kill_lock;
    }

    disp->magic = DISPATCH_MAGIC;

    *dispp = disp;
    return (ISC_R_SUCCESS);

    /*
     * error returns
     */
 kill_lock:
    DESTROYLOCK(&disp->lock);
 deallocate:
    isc_mempool_put(mgr->dpool, disp);

    return (res);
}


/*
 * MUST be unlocked, and not used by anthing.
 */
static void
dispatch_free(dns_dispatch_t **dispp)
{
    dns_dispatch_t *disp;
    dns_dispatchmgr_t *mgr;

    REQUIRE(VALID_DISPATCH(*dispp));
    disp = *dispp;
    *dispp = NULL;

    mgr = disp->mgr;
    REQUIRE(VALID_DISPATCHMGR(mgr));

    if (disp->tcpmsg_valid) {
        dns_tcpmsg_invalidate(&disp->tcpmsg);
        disp->tcpmsg_valid = 0;
    }

    INSIST(disp->tcpbuffers == 0);
    INSIST(disp->requests == 0);
    INSIST(disp->recv_pending == 0);

    isc_mempool_put(mgr->epool, disp->failsafe_ev);
    disp->failsafe_ev = NULL;

    if (disp->qid != NULL)
        qid_destroy(mgr->mctx, &disp->qid);
    disp->mgr = NULL;
    DESTROYLOCK(&disp->lock);
    disp->magic = 0;
    isc_mempool_put(mgr->dpool, disp);
}

isc_result_t
dns_dispatch_createtcp(dns_dispatchmgr_t *mgr, isc_socket_t *sock,
               isc_taskmgr_t *taskmgr, unsigned int buffersize,
               unsigned int maxbuffers, unsigned int maxrequests,
               unsigned int buckets, unsigned int increment,
               unsigned int attributes, dns_dispatch_t **dispp)
{
    isc_result_t result;
    dns_dispatch_t *disp;

    UNUSED(maxbuffers);
    UNUSED(buffersize);

    REQUIRE(VALID_DISPATCHMGR(mgr));
    REQUIRE(isc_socket_gettype(sock) == isc_sockettype_tcp);
    REQUIRE((attributes & DNS_DISPATCHATTR_TCP) != 0);
    REQUIRE((attributes & DNS_DISPATCHATTR_UDP) == 0);

    attributes |= DNS_DISPATCHATTR_PRIVATE;  /* XXXMLG */

    LOCK(&mgr->lock);

    /*
     * dispatch_allocate() checks mgr for us.
     * qid_allocate() checks buckets and increment for us.
     */
    disp = NULL;
    result = dispatch_allocate(mgr, maxrequests, &disp);
    if (result != ISC_R_SUCCESS) {
        UNLOCK(&mgr->lock);
        return (result);
    }

    result = qid_allocate(mgr, buckets, increment, &disp->qid);
    if (result != ISC_R_SUCCESS)
        goto deallocate_dispatch;

    disp->socktype = isc_sockettype_tcp;
    disp->socket = NULL;
    isc_socket_attach(sock, &disp->socket);

    disp->task = NULL;
    result = isc_task_create(taskmgr, 0, &disp->task);
    if (result != ISC_R_SUCCESS)
        goto kill_socket;

    disp->ctlevent = isc_event_allocate(mgr->mctx, disp,
                        DNS_EVENT_DISPATCHCONTROL,
                        destroy_disp, disp,
                        sizeof(isc_event_t));
    if (disp->ctlevent == NULL)
        goto kill_task;

    isc_task_setname(disp->task, "tcpdispatch", disp);

    dns_tcpmsg_init(mgr->mctx, disp->socket, &disp->tcpmsg);
    disp->tcpmsg_valid = 1;

    disp->attributes = attributes;

    /*
     * Append it to the dispatcher list.
     */
    ISC_LIST_APPEND(mgr->list, disp, link);
    UNLOCK(&mgr->lock);

    mgr_log(mgr, LVL(90), "created TCP dispatcher %p", disp);
    dispatch_log(disp, LVL(90), "created task %p", disp->task);

    *dispp = disp;

    return (ISC_R_SUCCESS);

    /*
     * Error returns.
     */
 kill_task:
    isc_task_detach(&disp->task);
 kill_socket:
    isc_socket_detach(&disp->socket);
 deallocate_dispatch:
    dispatch_free(&disp);

    UNLOCK(&mgr->lock);

    return (result);
}

isc_result_t
dns_dispatch_getudp(dns_dispatchmgr_t *mgr, isc_socketmgr_t *sockmgr,
            isc_taskmgr_t *taskmgr, isc_sockaddr_t *localaddr,
            unsigned int buffersize,
            unsigned int maxbuffers, unsigned int maxrequests,
            unsigned int buckets, unsigned int increment,
            unsigned int attributes, unsigned int mask,
            dns_dispatch_t **dispp)
{
    isc_result_t result;
    dns_dispatch_t *disp;

    REQUIRE(VALID_DISPATCHMGR(mgr));
    REQUIRE(sockmgr != NULL);
    REQUIRE(localaddr != NULL);
    REQUIRE(taskmgr != NULL);
    REQUIRE(buffersize >= 512 && buffersize < (64 * 1024));
    REQUIRE(maxbuffers > 0);
    REQUIRE(buckets < 2097169);  /* next prime > 65536 * 32 */
    REQUIRE(increment > buckets);
    REQUIRE(dispp != NULL && *dispp == NULL);
    REQUIRE((attributes & DNS_DISPATCHATTR_TCP) == 0);

    result = dns_dispatchmgr_setudp(mgr, buffersize, maxbuffers,
                    buckets, increment);
    if (result != ISC_R_SUCCESS)
        return (result);

    LOCK(&mgr->lock);

    /*
     * First, see if we have a dispatcher that matches.
     */
    disp = NULL;
    result = dispatch_find(mgr, localaddr, attributes, mask, &disp);
    if (result == ISC_R_SUCCESS) {
        disp->refcount++;

        if (disp->maxrequests < maxrequests)
            disp->maxrequests = maxrequests;

        if ((disp->attributes & DNS_DISPATCHATTR_NOLISTEN) == 0 &&
            (attributes & DNS_DISPATCHATTR_NOLISTEN) != 0)
        {
            disp->attributes |= DNS_DISPATCHATTR_NOLISTEN;
            if (disp->recv_pending != 0)
                isc_socket_cancel(disp->socket, disp->task,
                          ISC_SOCKCANCEL_RECV);
        }

        UNLOCK(&disp->lock);
        UNLOCK(&mgr->lock);

        *dispp = disp;

        return (ISC_R_SUCCESS);
    }

    /*
     * Nope, create one.
     */
    result = dispatch_createudp(mgr, sockmgr, taskmgr, localaddr,
                    maxrequests, attributes, &disp);
    if (result != ISC_R_SUCCESS) {
        UNLOCK(&mgr->lock);
        return (result);
    }

    UNLOCK(&mgr->lock);
    *dispp = disp;
    return (ISC_R_SUCCESS);
}

/*
 * mgr should be locked.
 */
static isc_result_t
dispatch_createudp(dns_dispatchmgr_t *mgr, isc_socketmgr_t *sockmgr,
           isc_taskmgr_t *taskmgr,
           isc_sockaddr_t *localaddr,
           unsigned int maxrequests,
           unsigned int attributes,
           dns_dispatch_t **dispp)
{
    isc_result_t result;
    dns_dispatch_t *disp;
    isc_socket_t *sock;

    /*
     * dispatch_allocate() checks mgr for us.
     */
    disp = NULL;
    result = dispatch_allocate(mgr, maxrequests, &disp);
    if (result != ISC_R_SUCCESS)
        return (result);

    /*
     * This assumes that the IP stack will *not* quickly reallocate
     * the same port.  If it does continually reallocate the same port
     * then we need a mechanism to hold all the blacklisted sockets
     * until we find a usable socket.
     */
 getsocket:
    result = create_socket(sockmgr, localaddr, &sock);
    if (result != ISC_R_SUCCESS)
        goto deallocate_dispatch;
    if (isc_sockaddr_getport(localaddr) == 0 && blacklisted(mgr, sock)) {
        isc_socket_detach(&sock);
        goto getsocket;
    }

    disp->socktype = isc_sockettype_udp;
    disp->socket = sock;
    disp->local = *localaddr;

    disp->task = NULL;
    result = isc_task_create(taskmgr, 0, &disp->task);
    if (result != ISC_R_SUCCESS)
        goto kill_socket;

    disp->ctlevent = isc_event_allocate(mgr->mctx, disp,
                        DNS_EVENT_DISPATCHCONTROL,
                        destroy_disp, disp,
                        sizeof(isc_event_t));
    if (disp->ctlevent == NULL)
        goto kill_task;

    isc_task_setname(disp->task, "udpdispatch", disp);

    attributes &= ~DNS_DISPATCHATTR_TCP;
    attributes |= DNS_DISPATCHATTR_UDP;
    disp->attributes = attributes;

    /*
     * Append it to the dispatcher list.
     */
    ISC_LIST_APPEND(mgr->list, disp, link);

    mgr_log(mgr, LVL(90), "created UDP dispatcher %p", disp);
    dispatch_log(disp, LVL(90), "created task %p", disp->task);
    dispatch_log(disp, LVL(90), "created socket %p", disp->socket);

    *dispp = disp;

    return (ISC_R_SUCCESS);

    /*
     * Error returns.
     */
 kill_task:
    isc_task_detach(&disp->task);
 kill_socket:
    isc_socket_detach(&disp->socket);
 deallocate_dispatch:
    dispatch_free(&disp);

    return (result);
}

void
dns_dispatch_attach(dns_dispatch_t *disp, dns_dispatch_t **dispp) {
    REQUIRE(VALID_DISPATCH(disp));
    REQUIRE(dispp != NULL && *dispp == NULL);

    LOCK(&disp->lock);
    disp->refcount++;
    UNLOCK(&disp->lock);

    *dispp = disp;
}

/*
 * It is important to lock the manager while we are deleting the dispatch,
 * since dns_dispatch_getudp will call dispatch_find, which returns to
 * the caller a dispatch but does not attach to it until later.  _getudp
 * locks the manager, however, so locking it here will keep us from attaching
 * to a dispatcher that is in the process of going away.
 */
void
dns_dispatch_detach(dns_dispatch_t **dispp) {
    dns_dispatch_t *disp;
    isc_boolean_t killit;

    REQUIRE(dispp != NULL && VALID_DISPATCH(*dispp));

    disp = *dispp;
    *dispp = NULL;

    LOCK(&disp->lock);

    INSIST(disp->refcount > 0);
    disp->refcount--;
    killit = ISC_FALSE;
    if (disp->refcount == 0) {
        if (disp->recv_pending > 0)
            isc_socket_cancel(disp->socket, disp->task,
                      ISC_SOCKCANCEL_RECV);
        disp->shutting_down = 1;
    }

    dispatch_log(disp, LVL(90), "detach: refcount %d", disp->refcount);

    killit = destroy_disp_ok(disp);
    UNLOCK(&disp->lock);
    if (killit)
        isc_task_send(disp->task, &disp->ctlevent);
}

isc_result_t
dns_dispatch_addresponse(dns_dispatch_t *disp, isc_sockaddr_t *dest,
             isc_task_t *task, isc_taskaction_t action, void *arg,
             dns_messageid_t *idp, dns_dispentry_t **resp)
{
    dns_dispentry_t *res;
    unsigned int bucket;
    dns_messageid_t id;
    int i;
    isc_boolean_t ok;
    dns_qid_t *qid;

    REQUIRE(VALID_DISPATCH(disp));
    REQUIRE(task != NULL);
    REQUIRE(dest != NULL);
    REQUIRE(resp != NULL && *resp == NULL);
    REQUIRE(idp != NULL);

    LOCK(&disp->lock);

    if (disp->shutting_down == 1) {
        UNLOCK(&disp->lock);
        return (ISC_R_SHUTTINGDOWN);
    }

    if (disp->requests >= disp->maxrequests) {
        UNLOCK(&disp->lock);
        return (ISC_R_QUOTA);
    }

    /*
     * Try somewhat hard to find an unique ID.
     */
    qid = DNS_QID(disp);
    LOCK(&qid->lock);
    id = dns_randomid(qid);
    bucket = dns_hash(qid, dest, id);
    ok = ISC_FALSE;
    for (i = 0; i < 64; i++) {
        if (bucket_search(qid, dest, id, bucket) == NULL) {
            ok = ISC_TRUE;
            break;
        }
        id += qid->qid_increment;
        id &= 0x0000ffff;
        bucket = dns_hash(qid, dest, id);
    }

    if (!ok) {
        UNLOCK(&qid->lock);
        UNLOCK(&disp->lock);
        return (ISC_R_NOMORE);
    }

    res = isc_mempool_get(disp->mgr->rpool);
    if (res == NULL) {
        UNLOCK(&qid->lock);
        UNLOCK(&disp->lock);
        return (ISC_R_NOMEMORY);
    }

    disp->refcount++;
    disp->requests++;
    res->task = NULL;
    isc_task_attach(task, &res->task);
    res->disp = disp;
    res->id = id;
    res->bucket = bucket;
    res->host = *dest;
    res->action = action;
    res->arg = arg;
    res->item_out = ISC_FALSE;
    ISC_LIST_INIT(res->items);
    ISC_LINK_INIT(res, link);
    res->magic = RESPONSE_MAGIC;
    ISC_LIST_APPEND(qid->qid_table[bucket], res, link);
    UNLOCK(&qid->lock);

    request_log(disp, res, LVL(90),
            "attached to task %p", res->task);

    if (((disp->attributes & DNS_DISPATCHATTR_UDP) != 0) ||
        ((disp->attributes & DNS_DISPATCHATTR_CONNECTED) != 0))
        startrecv(disp);

    UNLOCK(&disp->lock);

    *idp = id;
    *resp = res;

    return (ISC_R_SUCCESS);
}

void
dns_dispatch_starttcp(dns_dispatch_t *disp) {

    REQUIRE(VALID_DISPATCH(disp));

    dispatch_log(disp, LVL(90), "starttcp %p", disp->task);

    LOCK(&disp->lock);
    disp->attributes |= DNS_DISPATCHATTR_CONNECTED;
    startrecv(disp);
    UNLOCK(&disp->lock);
}

void
dns_dispatch_removeresponse(dns_dispentry_t **resp,
                dns_dispatchevent_t **sockevent)
{
    dns_dispatchmgr_t *mgr;
    dns_dispatch_t *disp;
    dns_dispentry_t *res;
    dns_dispatchevent_t *ev;
    unsigned int bucket;
    isc_boolean_t killit;
    unsigned int n;
    isc_eventlist_t events;
    dns_qid_t *qid;

    REQUIRE(resp != NULL);
    REQUIRE(VALID_RESPONSE(*resp));

    res = *resp;
    *resp = NULL;

    disp = res->disp;
    REQUIRE(VALID_DISPATCH(disp));
    mgr = disp->mgr;
    REQUIRE(VALID_DISPATCHMGR(mgr));

    qid = DNS_QID(disp);

    if (sockevent != NULL) {
        REQUIRE(*sockevent != NULL);
        ev = *sockevent;
        *sockevent = NULL;
    } else {
        ev = NULL;
    }

    LOCK(&disp->lock);

    INSIST(disp->requests > 0);
    disp->requests--;
    INSIST(disp->refcount > 0);
    disp->refcount--;
    killit = ISC_FALSE;
    if (disp->refcount == 0) {
        if (disp->recv_pending > 0)
            isc_socket_cancel(disp->socket, disp->task,
                      ISC_SOCKCANCEL_RECV);
        disp->shutting_down = 1;
    }

    bucket = res->bucket;

    LOCK(&qid->lock);
    ISC_LIST_UNLINK(qid->qid_table[bucket], res, link);
    UNLOCK(&qid->lock);

    if (ev == NULL && res->item_out) {
        /*
         * We've posted our event, but the caller hasn't gotten it
         * yet.  Take it back.
         */
        ISC_LIST_INIT(events);
        n = isc_task_unsend(res->task, res, DNS_EVENT_DISPATCH,
                    NULL, &events);
        /*
         * We had better have gotten it back.
         */
        INSIST(n == 1);
        ev = (dns_dispatchevent_t *)ISC_LIST_HEAD(events);
    }

    if (ev != NULL) {
        REQUIRE(res->item_out == ISC_TRUE);
        res->item_out = ISC_FALSE;
        if (ev->buffer.base != NULL)
            free_buffer(disp, ev->buffer.base, ev->buffer.length);
        free_event(disp, ev);
    }

    request_log(disp, res, LVL(90), "detaching from task %p", res->task);
    isc_task_detach(&res->task);

    /*
     * Free any buffered requests as well
     */
    ev = ISC_LIST_HEAD(res->items);
    while (ev != NULL) {
        ISC_LIST_UNLINK(res->items, ev, ev_link);
        if (ev->buffer.base != NULL)
            free_buffer(disp, ev->buffer.base, ev->buffer.length);
        free_event(disp, ev);
        ev = ISC_LIST_HEAD(res->items);
    }
    res->magic = 0;
    isc_mempool_put(disp->mgr->rpool, res);
    if (disp->shutting_down == 1)
        do_cancel(disp, NULL);
    else
        startrecv(disp);

    killit = destroy_disp_ok(disp);
    UNLOCK(&disp->lock);
    if (killit)
        isc_task_send(disp->task, &disp->ctlevent);
}

static void
do_cancel(dns_dispatch_t *disp, dns_dispentry_t *resp) {
    dns_dispatchevent_t *ev;
    dns_qid_t *qid;

    if (disp->shutdown_out == 1)
        return;

    qid = DNS_QID(disp);

    /*
     * Search for the first response handler without packets outstanding.
     */
    if (resp == NULL) {
        LOCK(&qid->lock);
        resp = linear_first(qid);
        if (resp == NULL) {
            /* no first item? */
            UNLOCK(&qid->lock);
            return;
        }
        do {
            if (resp->item_out == ISC_FALSE)
                break;

            resp = linear_next(qid, resp);
        } while (resp != NULL);
        UNLOCK(&qid->lock);
    }

    /*
     * No one to send the cancel event to, so nothing to do.
     */
    if (resp == NULL)
        return;

    /*
     * Send the shutdown failsafe event to this resp.
     */
    ev = disp->failsafe_ev;
    ISC_EVENT_INIT(ev, sizeof(*ev), 0, NULL, DNS_EVENT_DISPATCH,
               resp->action, resp->arg, resp, NULL, NULL);
    ev->result = disp->shutdown_why;
    ev->buffer.base = NULL;
    ev->buffer.length = 0;
    disp->shutdown_out = 1;
    request_log(disp, resp, LVL(10),
            "cancel: failsafe event %p -> task %p",
            ev, resp->task);
    resp->item_out = ISC_TRUE;
    isc_task_send(resp->task, ISC_EVENT_PTR(&ev));
}

isc_socket_t *
dns_dispatch_getsocket(dns_dispatch_t *disp) {
    REQUIRE(VALID_DISPATCH(disp));

    return (disp->socket);
}

isc_result_t
dns_dispatch_getlocaladdress(dns_dispatch_t *disp, isc_sockaddr_t *addrp) {

    REQUIRE(VALID_DISPATCH(disp));
    REQUIRE(addrp != NULL);

    if (disp->socktype == isc_sockettype_udp) {
        *addrp = disp->local;
        return (ISC_R_SUCCESS);
    }
    return (ISC_R_NOTIMPLEMENTED);
}

void
dns_dispatch_cancel(dns_dispatch_t *disp) {
    REQUIRE(VALID_DISPATCH(disp));

    LOCK(&disp->lock);

    if (disp->shutting_down == 1) {
        UNLOCK(&disp->lock);
        return;
    }

    disp->shutdown_why = ISC_R_CANCELED;
    disp->shutting_down = 1;
    do_cancel(disp, NULL);

    UNLOCK(&disp->lock);

    return;
}

void
dns_dispatch_changeattributes(dns_dispatch_t *disp,
                  unsigned int attributes, unsigned int mask)
{
    REQUIRE(VALID_DISPATCH(disp));

    /* XXXMLG
     * Should check for valid attributes here!
     */

    LOCK(&disp->lock);

    if ((mask & DNS_DISPATCHATTR_NOLISTEN) != 0) {
        if ((disp->attributes & DNS_DISPATCHATTR_NOLISTEN) != 0 &&
            (attributes & DNS_DISPATCHATTR_NOLISTEN) == 0) {
            disp->attributes &= ~DNS_DISPATCHATTR_NOLISTEN;
            startrecv(disp);
        } else if ((disp->attributes & DNS_DISPATCHATTR_NOLISTEN)
               == 0 &&
               (attributes & DNS_DISPATCHATTR_NOLISTEN) != 0) {
            disp->attributes |= DNS_DISPATCHATTR_NOLISTEN;
            if (disp->recv_pending != 0)
                isc_socket_cancel(disp->socket, disp->task,
                          ISC_SOCKCANCEL_RECV);
        }
    }

    disp->attributes &= ~mask;
    disp->attributes |= (attributes & mask);
    UNLOCK(&disp->lock);
}

void
dns_dispatch_importrecv(dns_dispatch_t *disp, isc_event_t *event) {
    void *buf;
    isc_socketevent_t *sevent, *newsevent;

    REQUIRE(VALID_DISPATCH(disp));
    REQUIRE((disp->attributes & DNS_DISPATCHATTR_NOLISTEN) != 0);
    REQUIRE(event != NULL);

    sevent = (isc_socketevent_t *)event;

    INSIST(sevent->n <= disp->mgr->buffersize);
    newsevent = (isc_socketevent_t *)
            isc_event_allocate(disp->mgr->mctx, NULL,
                      DNS_EVENT_IMPORTRECVDONE, udp_recv,
                      disp, sizeof(isc_socketevent_t));
    if (newsevent == NULL)
        return;

    buf = allocate_udp_buffer(disp);
    if (buf == NULL) {
        isc_event_free(ISC_EVENT_PTR(&newsevent));
        return;
    }
    memcpy(buf, sevent->region.base, sevent->n);
    newsevent->region.base = buf;
    newsevent->region.length = disp->mgr->buffersize;
    newsevent->n = sevent->n;
    newsevent->result = sevent->result;
    newsevent->address = sevent->address;
    newsevent->timestamp = sevent->timestamp;
    newsevent->pktinfo = sevent->pktinfo;
    newsevent->attributes = sevent->attributes;

    isc_task_send(disp->task, ISC_EVENT_PTR(&newsevent));
}

#if 0
void
dns_dispatchmgr_dump(dns_dispatchmgr_t *mgr) {
    dns_dispatch_t *disp;
    char foo[1024];

    disp = ISC_LIST_HEAD(mgr->list);
    while (disp != NULL) {
        isc_sockaddr_format(&disp->local, foo, sizeof(foo));
        printf("\tdispatch %p, addr %s\n", disp, foo);
        disp = ISC_LIST_NEXT(disp, link);
    }
}
#endif