bin/named/client.c

	client.c revision 918148ce9bf3ec69d9745393869df4067fe62594
/*
 * Copyright (C) 1999, 2000  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.
 */

/* $Id: client.c,v 1.113 2000/09/13 03:15:01 marka Exp $ */

#include <config.h>

#include <isc/print.h>
#include <isc/mutex.h>
#include <isc/task.h>
#include <isc/string.h>
#include <isc/timer.h>
#include <isc/util.h>

#include <dns/dispatch.h>
#include <dns/events.h>
#include <dns/message.h>
#include <dns/rdata.h>
#include <dns/rdatalist.h>
#include <dns/rdataset.h>
#include <dns/tsig.h>
#include <dns/view.h>
#include <dns/zone.h>

#include <named/interfacemgr.h>
#include <named/log.h>
#include <named/notify.h>
#include <named/server.h>
#include <named/update.h>

/***
 *** Client
 ***/

/*
 * Important note!
 *
 * All client state changes, other than that from idle to listening, occur
 * as a result of events.  This guarantees serialization and avoids the
 * need for locking.
 *
 * If a routine is ever created that allows someone other than the client's
 * task to change the client, then the client will have to be locked.
 */

#define NS_CLIENT_TRACE
#ifdef NS_CLIENT_TRACE
#define CTRACE(m)   ns_client_log(client, \
                      NS_LOGCATEGORY_CLIENT, \
                      NS_LOGMODULE_CLIENT, \
                      ISC_LOG_DEBUG(3), \
                      "%s", (m))
#define MTRACE(m)   isc_log_write(ns_g_lctx, \
                      NS_LOGCATEGORY_GENERAL, \
                      NS_LOGMODULE_CLIENT, \
                      ISC_LOG_DEBUG(3), \
                      "clientmgr @%p: %s", manager, (m))
#else
#define CTRACE(m)   ((void)(m))
#define MTRACE(m)   ((void)(m))
#endif

#define TCP_CLIENT(c)   (((c)->attributes & NS_CLIENTATTR_TCP) != 0)

#define TCP_BUFFER_SIZE         (65535 + 2)
#define SEND_BUFFER_SIZE        2048
#define RECV_BUFFER_SIZE        2048

struct ns_clientmgr {
    /* Unlocked. */
    unsigned int            magic;
    isc_mem_t *         mctx;
    isc_taskmgr_t *         taskmgr;
    isc_timermgr_t *        timermgr;
    isc_mutex_t         lock;
    /* Locked by lock. */
    isc_boolean_t           exiting;
    client_list_t           active;     /* Active clients */
    client_list_t           inactive;   /* To be recycled */
};

#define MANAGER_MAGIC           0x4E53436DU /* NSCm */
#define VALID_MANAGER(m)        ((m) != NULL && \
                     (m)->magic == MANAGER_MAGIC)

/*
 * Client object states.  Ordering is significant: higher-numbered
 * states are generally "more active", meaning that the client can
 * have more dynamically allocated data, outstanding events, etc.
 * In the list below, any such properties listed for state N
 * also apply to any state > N.
 *
 * To force the client into a less active state, set client->newstate
 * to that state and call exit_check().  This will cause any
 * activities defined for higher-numbered states to be aborted.
 */

#define NS_CLIENTSTATE_FREED    0
/*
 * The client object no longer exists.
 */

#define NS_CLIENTSTATE_INACTIVE 1
/*
 * The client object exists and has a task and timer.
 * Its "query" struct and sendbuf are initialized.
 * It is on the client manager's list of inactive clients.
 * It has a message and OPT, both in the reset state.
 */

#define NS_CLIENTSTATE_READY    2
/*
 * The client object is either a TCP or a UDP one, and
 * it is associated with a network interface.  It is on the
 * client manager's list of active clients.
 *
 * If it is a TCP client object, it has a TCP listener socket
 * and an outstading TCP listen request.
 *
 * If it is a UDP client object, it is associated with a
 * dispatch and has an outstanding dispatch request.
 */

#define NS_CLIENTSTATE_READING  3
/*
 * The client object is a TCP client object that has received
 * a connection.  It has a tcpsocket, tcpmsg, TCP quota, and an
 * outstanding TCP read request.  This state is not used for
 * UDP client objects.
 */

#define NS_CLIENTSTATE_WORKING  4
/*
 * The client object has received a request and is working
 * on it.  It has a view, and it may  have any of a non-reset OPT,
 * recursion quota, and an outstanding write request.  If it
 * is a UDP client object, it has a dispatch event.
 */

#define NS_CLIENTSTATE_MAX      9
/*
 * Sentinel value used to indicate "no state".  When client->newstate
 * has this value, we are not attempting to exit the current state.
 * Must be greater than any valid state.
 */


static void client_read(ns_client_t *client);
static void client_accept(ns_client_t *client);
static void clientmgr_destroy(ns_clientmgr_t *manager);
static isc_boolean_t exit_check(ns_client_t *client);
static void ns_client_endrequest(ns_client_t *client);
static void ns_client_checkactive(ns_client_t *client);
static void client_start(isc_task_t *task, isc_event_t *event);
static void client_request(isc_task_t *task, isc_event_t *event);

/*
 * Enter the inactive state.
 *
 * Requires:
 *  No requests are outstanding.
 */
static void
client_deactivate(ns_client_t *client) {
    REQUIRE(NS_CLIENT_VALID(client));

    if (client->interface)
        ns_interface_detach(&client->interface);

    INSIST(client->naccepts == 0);
    if (client->tcplistener != NULL)
        isc_socket_detach(&client->tcplistener);

    if (client->dispentry != NULL) {
        dns_dispatchevent_t **deventp;
        if (client->dispevent != NULL)
            deventp = &client->dispevent;
        else
            deventp = NULL;
        dns_dispatch_removerequest(&client->dispentry, deventp);
    }
    if (client->dispatch != NULL)
        dns_dispatch_detach(&client->dispatch);

    client->attributes = 0;
    client->mortal = ISC_FALSE;

    LOCK(&client->manager->lock);
    ISC_LIST_UNLINK(client->manager->active, client, link);
    ISC_LIST_APPEND(client->manager->inactive, client, link);
    client->list = &client->manager->inactive;
    UNLOCK(&client->manager->lock);
}

/*
 * Clean up a client object and free its memory.
 * Requires:
 *   The client is in the inactive state.
 */

static void
client_free(ns_client_t *client) {
    isc_boolean_t need_clientmgr_destroy = ISC_FALSE;
    ns_clientmgr_t *manager = NULL;

    REQUIRE(NS_CLIENT_VALID(client));

    /*
     * When "shuttingdown" is true, either the task has received
     * its shutdown event or no shutdown event has ever been
     * set up.  Thus, we have no outstanding shutdown
     * event at this point.
     */
    REQUIRE(client->state == NS_CLIENTSTATE_INACTIVE);

    ns_query_free(client);
    isc_mem_put(client->mctx, client->sendbuf, SEND_BUFFER_SIZE);
    isc_timer_detach(&client->timer);

    if (client->tcpbuf != NULL)
        isc_mem_put(client->mctx, client->tcpbuf, TCP_BUFFER_SIZE);
    if (client->opt != NULL) {
        INSIST(dns_rdataset_isassociated(client->opt));
        dns_rdataset_disassociate(client->opt);
        dns_message_puttemprdataset(client->message, &client->opt);
    }
    dns_message_destroy(&client->message);
    if (client->task != NULL)
        isc_task_detach(&client->task);
    if (client->manager != NULL) {
        manager = client->manager;
        LOCK(&manager->lock);
        ISC_LIST_UNLINK(*client->list, client, link);
        client->list = NULL;
        if (manager->exiting &&
            ISC_LIST_EMPTY(manager->active) &&
            ISC_LIST_EMPTY(manager->inactive))
            need_clientmgr_destroy = ISC_TRUE;
        UNLOCK(&manager->lock);
    }

    CTRACE("free");
    client->magic = 0;
    isc_mem_put(client->mctx, client, sizeof *client);

    if (need_clientmgr_destroy)
        clientmgr_destroy(manager);
}

static void
set_timeout(ns_client_t *client, unsigned int seconds) {
    isc_result_t result;
    isc_interval_t interval;

    isc_interval_set(&interval, seconds, 0);
    result = isc_timer_reset(client->timer, isc_timertype_once, NULL,
                 &interval, ISC_FALSE);
    if (result != ISC_R_SUCCESS) {
        ns_client_log(client, NS_LOGCATEGORY_CLIENT,
                  NS_LOGMODULE_CLIENT, ISC_LOG_ERROR,
                  "setting timeout: %s",
                  isc_result_totext(result));
        /* Continue anyway. */
    }
}

/*
 * Check for a deactivation or shutdown request and take appropriate
 * action.  Returns ISC_TRUE if either is in progress; in this case
 * the caller must no longer use the client object as it may have been
 * freed.
 */
static isc_boolean_t
exit_check(ns_client_t *client) {
    REQUIRE(NS_CLIENT_VALID(client));

    if (client->state <= client->newstate)
        return (ISC_FALSE); /* Business as usual. */

    INSIST(client->newstate < NS_CLIENTSTATE_WORKING);

    /*
     * We need to detach from the view early when shutting down
     * the server to break the following vicious circle:
     *
     *  - The resolver will not shut down until the view refcount is zero
     *  - The view refcount does not go to zero until all clients detach
     *  - The client does not detach from the view until references is zero
     *  - references does not go to zero until the resolver has shut down
     *
     */
    if (client->newstate == NS_CLIENTSTATE_FREED && client->view != NULL)
        dns_view_detach(&client->view);

    if (client->state == NS_CLIENTSTATE_WORKING) {
        INSIST(client->newstate <= NS_CLIENTSTATE_READING);
        /*
         * We are trying to abort request processing.
         */
        if (client->nsends > 0) {
            isc_socket_t *socket;
            if (TCP_CLIENT(client))
                socket = client->tcpsocket;
            else
                socket =
                dns_dispatch_getsocket(client->dispatch);
            isc_socket_cancel(socket, client->task,
                      ISC_SOCKCANCEL_SEND);
        }

        if (! (client->nsends == 0 && client->references == 0)) {
            /*
             * Still waiting for I/O cancel completion.
             * or lingering references.
             */
            return (ISC_TRUE);
        }
        /*
         * I/O cancel is complete.  Burn down all state
         * related to the current request.
         */
        ns_client_endrequest(client);

        client->state = NS_CLIENTSTATE_READING;
        if (NS_CLIENTSTATE_READING == client->newstate) {
            client_read(client);
            client->newstate = NS_CLIENTSTATE_MAX;
            return (ISC_TRUE); /* We're done. */
        }
    }

    if (client->state == NS_CLIENTSTATE_READING) {
        /*
         * We are trying to abort the current TCP connection,
         * if any.
         */
        INSIST(client->newstate <= NS_CLIENTSTATE_READY);
        if (client->nreads > 0)
            dns_tcpmsg_cancelread(&client->tcpmsg);
        if (! client->nreads == 0) {
            /* Still waiting for read cancel completion. */
            return (ISC_TRUE);
        }

        if (client->tcpmsg_valid) {
            dns_tcpmsg_invalidate(&client->tcpmsg);
            client->tcpmsg_valid = ISC_FALSE;
        }
        if (client->tcpsocket != NULL) {
            CTRACE("closetcp");
            isc_socket_detach(&client->tcpsocket);
        }

        if (client->tcpquota != NULL)
            isc_quota_detach(&client->tcpquota);

        (void) isc_timer_reset(client->timer, isc_timertype_inactive,
                       NULL, NULL, ISC_TRUE);

        client->peeraddr_valid = ISC_FALSE;

        client->state = NS_CLIENTSTATE_READY;

        /*
         * Now the client is ready to accept a new TCP connection
         * or UDP request, but we may have enough clients doing
         * that already.  Check whether this client needs to remain
         * active and force it to go inactive if not.
         */
        ns_client_checkactive(client);

        if (NS_CLIENTSTATE_READY == client->newstate) {
            if (TCP_CLIENT(client)) {
                client_accept(client);
            } else {
                /*
                 * Give the processed dispatch event back to
                 * the dispatch. This tells the dispatch
                 * that we are ready to receive the next event.
                 */
                dns_dispatch_freeevent(client->dispatch,
                               client->dispentry,
                               &client->dispevent);
            }
            client->newstate = NS_CLIENTSTATE_MAX;
            return (ISC_TRUE);
        }
    }

    if (client->state == NS_CLIENTSTATE_READY) {
        INSIST(client->newstate <= NS_CLIENTSTATE_INACTIVE);
        /*
         * We are trying to enter the inactive state.
         */
        if (client->naccepts > 0)
            isc_socket_cancel(client->tcplistener, client->task,
                      ISC_SOCKCANCEL_ACCEPT);

        if (! (client->naccepts == 0)) {
            /* Still waiting for accept cancel completion. */
            return (ISC_TRUE);
        }
        /* Accept cancel is complete. */
        client_deactivate(client);
        client->state = NS_CLIENTSTATE_INACTIVE;
        if (client->state == client->newstate) {
            client->newstate = NS_CLIENTSTATE_MAX;
            return (ISC_TRUE); /* We're done. */
        }
    }

    if (client->state == NS_CLIENTSTATE_INACTIVE) {
        INSIST(client->newstate == NS_CLIENTSTATE_FREED);
        /*
         * We are trying to free the client.
         */
        client_free(client);
        return (ISC_TRUE);
    }

    return (ISC_TRUE);
}

/*
 * The client's task has received the client's control event
 * as part of the startup process.
 */
static void
client_start(isc_task_t *task, isc_event_t *event) {
    ns_client_t *client = (ns_client_t *) event->ev_arg;
    isc_result_t result;

    INSIST(task == client->task);

    UNUSED(task);

    if (TCP_CLIENT(client)) {
        client_accept(client);
    } else {
        result = dns_dispatch_addrequest(client->dispatch,
                         client->task,
                         client_request,
                         client,
                         &client->dispentry);

        if (result != ISC_R_SUCCESS) {
            ns_client_log(client,
                      DNS_LOGCATEGORY_SECURITY,
                      NS_LOGMODULE_CLIENT,
                      ISC_LOG_DEBUG(3),
                      "dns_dispatch_addrequest() "
                      "failed: %s",
                      isc_result_totext(result));
            /*
             * Not much we can do here but log the failure;
             * the client will effectively go idle.
             */
        }
    }
}


/*
 * The client's task has received a shutdown event.
 */
static void
client_shutdown(isc_task_t *task, isc_event_t *event) {
    ns_client_t *client;

    REQUIRE(event != NULL);
    REQUIRE(event->ev_type == ISC_TASKEVENT_SHUTDOWN);
    client = event->ev_arg;
    REQUIRE(NS_CLIENT_VALID(client));
    REQUIRE(task == client->task);

    UNUSED(task);

    CTRACE("shutdown");

    isc_event_free(&event);

    if (client->shutdown != NULL) {
        (client->shutdown)(client->shutdown_arg, ISC_R_SHUTTINGDOWN);
        client->shutdown = NULL;
        client->shutdown_arg = NULL;
    }

    client->newstate = NS_CLIENTSTATE_FREED;
    (void)exit_check(client);
}


static void
ns_client_endrequest(ns_client_t *client) {
    INSIST(client->naccepts == 0);
    INSIST(client->nreads == 0);
    INSIST(client->nsends == 0);
    INSIST(client->state == NS_CLIENTSTATE_WORKING);

    CTRACE("endrequest");

    if (client->next != NULL) {
        (client->next)(client);
        client->next = NULL;
    }

    if (client->view != NULL)
        dns_view_detach(&client->view);
    if (client->opt != NULL) {
        INSIST(dns_rdataset_isassociated(client->opt));
        dns_rdataset_disassociate(client->opt);
        dns_message_puttemprdataset(client->message, &client->opt);
    }

    client->udpsize = 512;
    dns_message_reset(client->message, DNS_MESSAGE_INTENTPARSE);

    if (client->recursionquota != NULL)
        isc_quota_detach(&client->recursionquota);

    /*
     * Clear all client attributes that are specific to
     * the request; that's all except the TCP flag.
     */
    client->attributes &= NS_CLIENTATTR_TCP;
}

static void
ns_client_checkactive(ns_client_t *client) {
    if (client->mortal) {
        /*
         * This client object should normally go inactive
         * at this point, but if we have fewer active client
         * objects than  desired due to earlier quota exhaustion,
         * keep it active to make up for the shortage.
         */
        isc_boolean_t need_another_client = ISC_FALSE;
        if (TCP_CLIENT(client)) {
            LOCK(&client->interface->lock);
            if (client->interface->ntcpcurrent <
                client->interface->ntcptarget)
                need_another_client = ISC_TRUE;
            UNLOCK(&client->interface->lock);
        } else {
            /*
             * The UDP client quota is enforced by making
             * requests fail rather than by not listening
             * for new ones.  Therefore, there is always a
             * full set of UDP clients listening.
             */
        }
        if (! need_another_client) {
            /*
             * We don't need this client object.  Recycle it.
             */
            if (client->newstate >= NS_CLIENTSTATE_INACTIVE)
                client->newstate = NS_CLIENTSTATE_INACTIVE;
        }
    }
}

void
ns_client_next(ns_client_t *client, isc_result_t result) {
    int newstate;

    REQUIRE(NS_CLIENT_VALID(client));
    REQUIRE(client->state == NS_CLIENTSTATE_WORKING);

    CTRACE("next");

    if (result != ISC_R_SUCCESS)
        ns_client_log(client, DNS_LOGCATEGORY_SECURITY,
                  NS_LOGMODULE_CLIENT, ISC_LOG_DEBUG(3),
                  "request failed: %s", isc_result_totext(result));

    /*
     * An error processing a TCP request may have left
     * the connection out of sync.  To be safe, we always
     * sever the connection when result != ISC_R_SUCCESS.
     */
    if (result == ISC_R_SUCCESS && TCP_CLIENT(client))
        newstate = NS_CLIENTSTATE_READING;
    else
        newstate = NS_CLIENTSTATE_READY;

    if (client->newstate > newstate)
        client->newstate = newstate;
    (void) exit_check(client);
}


static void
client_senddone(isc_task_t *task, isc_event_t *event) {
    ns_client_t *client;
    isc_socketevent_t *sevent = (isc_socketevent_t *) event;

    REQUIRE(sevent != NULL);
    REQUIRE(sevent->ev_type == ISC_SOCKEVENT_SENDDONE);
    client = sevent->ev_arg;
    REQUIRE(NS_CLIENT_VALID(client));
    REQUIRE(task == client->task);

    UNUSED(task);

    CTRACE("senddone");

    if (sevent->result != ISC_R_SUCCESS)
        ns_client_log(client, NS_LOGCATEGORY_CLIENT,
                  NS_LOGMODULE_CLIENT, ISC_LOG_WARNING,
                  "error sending response: %s",
                  isc_result_totext(sevent->result));

    INSIST(client->nsends > 0);
    client->nsends--;

    if (client->tcpbuf != NULL) {
        INSIST(TCP_CLIENT(client));
        isc_mem_put(client->mctx, client->tcpbuf, TCP_BUFFER_SIZE);
        client->tcpbuf = NULL;
    }

    isc_event_free(&event);

    if (exit_check(client))
        return;

    ns_client_next(client, ISC_R_SUCCESS);
}

static isc_result_t
client_allocsendbuf(ns_client_t *client, isc_buffer_t *buffer,
            isc_buffer_t *tcpbuffer, isc_uint32_t length,
            unsigned char **datap)
{
    unsigned char *data;
    isc_uint32_t bufsize;
    isc_result_t result;

    INSIST(datap != NULL);

    if (TCP_CLIENT(client)) {
        INSIST(client->tcpbuf == NULL);
        if (tcpbuffer == NULL && length + 2 > TCP_BUFFER_SIZE) {
            result = ISC_R_NOSPACE;
            goto done;
        }
        client->tcpbuf = isc_mem_get(client->mctx, TCP_BUFFER_SIZE);
        if (client->tcpbuf == NULL) {
            result = ISC_R_NOMEMORY;
            goto done;
        }
        data = client->tcpbuf;
        if (tcpbuffer != NULL) {
            isc_buffer_init(tcpbuffer, data, TCP_BUFFER_SIZE);
            isc_buffer_init(buffer, data + 2, TCP_BUFFER_SIZE - 2);
        } else {
            isc_buffer_init(buffer, data, TCP_BUFFER_SIZE);
            isc_buffer_putuint16(buffer, length);
        }
    } else {
        data = client->sendbuf;
        if (client->udpsize < SEND_BUFFER_SIZE)
            bufsize = client->udpsize;
        else
            bufsize = SEND_BUFFER_SIZE;
        if (tcpbuffer == NULL && length > bufsize) {
            result = ISC_R_NOSPACE;
            goto done;
        }
        isc_buffer_init(buffer, data, bufsize);
    }
    *datap = data;
    result = ISC_R_SUCCESS;

 done:
    return (result);
}

static isc_result_t
client_sendpkg(ns_client_t *client, isc_buffer_t *buffer) {
    struct in6_pktinfo *pktinfo;
    isc_result_t result;
    isc_region_t r;
    isc_sockaddr_t *address;
    isc_socket_t *socket;

    if (TCP_CLIENT(client)) {
        socket = client->tcpsocket;
        address = NULL;
    } else {
        socket = dns_dispatch_getsocket(client->dispatch);
        address = &client->dispevent->addr;
    }

    if ((client->attributes & NS_CLIENTATTR_PKTINFO) != 0)
        pktinfo = &client->pktinfo;
    else
        pktinfo = NULL;

    isc_buffer_usedregion(buffer, &r);

    CTRACE("sendto");
    result = isc_socket_sendto(socket, &r, client->task, client_senddone,
                   client, address, pktinfo);
    if (result == ISC_R_SUCCESS) {
        client->nsends++;
    }
    return (result);
}

void
ns_client_sendraw(ns_client_t *client, dns_message_t *message) {
    isc_result_t result;
    unsigned char *data;
    isc_buffer_t buffer;
    isc_region_t r;
    isc_region_t *mr;

    REQUIRE(NS_CLIENT_VALID(client));

    CTRACE("sendraw");

    mr = dns_message_getrawmessage(message);
    if (mr == NULL) {
        result = ISC_R_UNEXPECTEDEND;
        goto done;
    }

    result = client_allocsendbuf(client, &buffer, NULL, mr->length, &data);
    if (result != ISC_R_SUCCESS)
        goto done;

    /*
     * Copy message to buffer and fixup id.
     */
    isc_buffer_availableregion(&buffer, &r);
    result = isc_buffer_copyregion(&buffer, mr);
    if (result != ISC_R_SUCCESS)
        goto done;
    r.base[0] = (client->message->id >> 8) & 0xff;
    r.base[1] = client->message->id & 0xff;

    result = client_sendpkg(client, &buffer);
    if (result == ISC_R_SUCCESS)
        return;

 done:
    if (client->tcpbuf != NULL) {
        isc_mem_put(client->mctx, client->tcpbuf, TCP_BUFFER_SIZE);
        client->tcpbuf = NULL;
    }
    ns_client_next(client, result);
}

void
ns_client_send(ns_client_t *client) {
    isc_result_t result;
    unsigned char *data;
    isc_buffer_t buffer;
    isc_buffer_t tcpbuffer;
    isc_region_t r;

    REQUIRE(NS_CLIENT_VALID(client));

    CTRACE("send");

    if ((client->attributes & NS_CLIENTATTR_RA) != 0)
        client->message->flags |= DNS_MESSAGEFLAG_RA;

    /*
     * XXXRTH  The following doesn't deal with TSIGs, TCP buffer resizing,
     *         or ENDS1 more data packets.
     */
    result = client_allocsendbuf(client, &buffer, &tcpbuffer, 0, &data);
    if (result != ISC_R_SUCCESS)
        goto done;

    result = dns_message_renderbegin(client->message, &buffer);
    if (result != ISC_R_SUCCESS)
        goto done;
    if (client->opt != NULL) {
        result = dns_message_setopt(client->message, client->opt);
        if (result != ISC_R_SUCCESS)
            goto done;
        /*
         * XXXRTH dns_message_setopt() should probably do this...
         */
        client->opt = NULL;
    }
    result = dns_message_rendersection(client->message,
                       DNS_SECTION_QUESTION, 0);
    if (result != ISC_R_SUCCESS)
        goto done;
    result = dns_message_rendersection(client->message,
                       DNS_SECTION_ANSWER, 0);
    if (result == ISC_R_NOSPACE) {
        client->message->flags |= DNS_MESSAGEFLAG_TC;
        goto renderend;
    }
    if (result != ISC_R_SUCCESS)
        goto done;
    result = dns_message_rendersection(client->message,
                       DNS_SECTION_AUTHORITY, 0);
    if (result == ISC_R_NOSPACE) {
        client->message->flags |= DNS_MESSAGEFLAG_TC;
        goto renderend;
    }
    if (result != ISC_R_SUCCESS)
        goto done;
    result = dns_message_rendersection(client->message,
                       DNS_SECTION_ADDITIONAL, 0);
    if (result != ISC_R_SUCCESS && result != ISC_R_NOSPACE)
        goto done;
 renderend:
    result = dns_message_renderend(client->message);

    if (result != ISC_R_SUCCESS)
        goto done;

    if (TCP_CLIENT(client)) {
        isc_buffer_usedregion(&buffer, &r);
        isc_buffer_putuint16(&tcpbuffer, (isc_uint16_t) r.length);
        isc_buffer_add(&tcpbuffer, r.length);
        result = client_sendpkg(client, &tcpbuffer);
    } else
        result = client_sendpkg(client, &buffer);
    if (result == ISC_R_SUCCESS)
        return;

 done:
    if (client->tcpbuf != NULL) {
        isc_mem_put(client->mctx, client->tcpbuf, TCP_BUFFER_SIZE);
        client->tcpbuf = NULL;
    }
    ns_client_next(client, result);
}

void
ns_client_error(ns_client_t *client, isc_result_t result) {
    dns_rcode_t rcode;
    dns_message_t *message;

    REQUIRE(NS_CLIENT_VALID(client));

    CTRACE("error");

    message = client->message;
    rcode = dns_result_torcode(result);

    /*
     * Message may be an in-progress reply that we had trouble
     * with, in which case QR will be set.  We need to clear QR before
     * calling dns_message_reply() to avoid triggering an assertion.
     */
    message->flags &= ~DNS_MESSAGEFLAG_QR;
    /*
     * AA and AD shouldn't be set.
     */
    message->flags &= ~(DNS_MESSAGEFLAG_AA | DNS_MESSAGEFLAG_AD);
    result = dns_message_reply(message, ISC_TRUE);
    if (result != ISC_R_SUCCESS) {
        /*
         * It could be that we've got a query with a good header,
         * but a bad question section, so we try again with
         * want_question_section set to ISC_FALSE.
         */
        result = dns_message_reply(message, ISC_FALSE);
        if (result != ISC_R_SUCCESS) {
            ns_client_next(client, result);
            return;
        }
    }
    message->rcode = rcode;
    ns_client_send(client);
}

static inline isc_result_t
client_addopt(ns_client_t *client) {
    dns_rdataset_t *rdataset;
    dns_rdatalist_t *rdatalist;
    dns_rdata_t *rdata;
    isc_result_t result;

    REQUIRE(client->opt == NULL);   /* XXXRTH free old. */

    rdatalist = NULL;
    result = dns_message_gettemprdatalist(client->message, &rdatalist);
    if (result != ISC_R_SUCCESS)
        return (result);
    rdata = NULL;
    result = dns_message_gettemprdata(client->message, &rdata);
    if (result != ISC_R_SUCCESS)
        return (result);
    rdataset = NULL;
    result = dns_message_gettemprdataset(client->message, &rdataset);
    if (result != ISC_R_SUCCESS)
        return (result);
    dns_rdataset_init(rdataset);

    rdatalist->type = dns_rdatatype_opt;
    rdatalist->covers = 0;

    /*
     * Set Maximum UDP buffer size.
     */
    rdatalist->rdclass = RECV_BUFFER_SIZE;

    /*
     * Set EXTENDED-RCODE, VERSION, and Z to 0.
     */
    rdatalist->ttl = 0;

    /*
     * No ENDS options.
     */
    rdata->data = NULL;
    rdata->length = 0;
    rdata->rdclass = rdatalist->rdclass;
    rdata->type = rdatalist->type;

    ISC_LIST_INIT(rdatalist->rdata);
    ISC_LIST_APPEND(rdatalist->rdata, rdata, link);
    dns_rdatalist_tordataset(rdatalist, rdataset);

    client->opt = rdataset;

    return (ISC_R_SUCCESS);
}

/*
 * Handle an incoming request event from the dispatch (UDP case)
 * or tcpmsg (TCP case).
 */
static void
client_request(isc_task_t *task, isc_event_t *event) {
    ns_client_t *client;
    dns_dispatchevent_t *devent;
    isc_result_t result;
    isc_result_t sigresult;
    isc_buffer_t *buffer;
    dns_view_t *view;
    dns_rdataset_t *opt;
    isc_boolean_t ra;   /* Recursion available. */

    REQUIRE(event != NULL);
    client = event->ev_arg;
    REQUIRE(NS_CLIENT_VALID(client));
    REQUIRE(task == client->task);

    UNUSED(task);

    INSIST(client->recursionquota == NULL);

    INSIST(client->state ==
           TCP_CLIENT(client) ?
           NS_CLIENTSTATE_READING :
           NS_CLIENTSTATE_READY);

    RWLOCK(&ns_g_server->conflock, isc_rwlocktype_read);
    dns_zonemgr_lockconf(ns_g_server->zonemgr, isc_rwlocktype_read);

    if (event->ev_type == DNS_EVENT_DISPATCH) {
        INSIST(!TCP_CLIENT(client));
        devent = (dns_dispatchevent_t *)event;
        REQUIRE(client->dispentry != NULL);
        client->dispevent = devent;
        buffer = &devent->buffer;
        result = devent->result;
        client->peeraddr = devent->addr;
        client->peeraddr_valid = ISC_TRUE;
        if ((devent->attributes & ISC_SOCKEVENTATTR_PKTINFO) != 0) {
            client->attributes |= NS_CLIENTATTR_PKTINFO;
            client->pktinfo = devent->pktinfo;
        }
        if ((devent->attributes & ISC_SOCKEVENTATTR_MULTICAST) != 0)
            client->attributes |= NS_CLIENTATTR_MULTICAST;
    } else {
        INSIST(TCP_CLIENT(client));
        REQUIRE(event->ev_type == DNS_EVENT_TCPMSG);
        REQUIRE(event->ev_sender == &client->tcpmsg);
        buffer = &client->tcpmsg.buffer;
        result = client->tcpmsg.result;
        INSIST(client->nreads == 1);
        /*
         * client->peeraddr was set when the connection was accepted.
         */
        client->nreads--;
    }

    ns_client_log(client, NS_LOGCATEGORY_CLIENT,
              NS_LOGMODULE_CLIENT, ISC_LOG_DEBUG(3),
              "%s request",
              TCP_CLIENT(client) ? "TCP" : "UDP");

    if (exit_check(client))
        goto cleanup_serverlock;
    client->state = client->newstate = NS_CLIENTSTATE_WORKING;

    isc_stdtime_get(&client->requesttime);
    client->now = client->requesttime;

    set_timeout(client, 60);

    if (result != ISC_R_SUCCESS) {
        if (TCP_CLIENT(client))
            ns_client_next(client, result);
        else
            isc_task_shutdown(client->task);
        goto cleanup_serverlock;
    }

    if ((client->attributes & NS_CLIENTATTR_MULTICAST) != 0) {
        ns_client_log(client, NS_LOGCATEGORY_CLIENT,
                  NS_LOGMODULE_CLIENT, ISC_LOG_DEBUG(2),
                  "multicast request");
#if 0
        ns_client_error(client, DNS_R_REFUSED);
#endif
    }

    result = dns_message_parse(client->message, buffer, ISC_FALSE);
    if (result != ISC_R_SUCCESS) {
        ns_client_error(client, result);
        goto cleanup_serverlock;
    }

    /*
     * We expect a query, not a response.  Unexpected UDP responses
     * are discarded early by the dispatcher, but TCP responses
     * bypass the dispatcher and must be discarded here.
     */
    if ((client->message->flags & DNS_MESSAGEFLAG_QR) != 0) {
        CTRACE("unexpected response");
        ns_client_next(client, DNS_R_FORMERR);
        goto cleanup_serverlock;
    }

    /*
     * Deal with EDNS.
     */
    opt = dns_message_getopt(client->message);
    if (opt != NULL) {
        unsigned int version;

        /*
         * Set the client's UDP buffer size.
         */
        client->udpsize = opt->rdclass;

        /*
         * Create an OPT for our reply.
         */
        result = client_addopt(client);
        if (result != ISC_R_SUCCESS) {
            ns_client_error(client, result);
            goto cleanup_serverlock;
        }

        /*
         * Do we understand this version of ENDS?
         *
         * XXXRTH need library support for this!
         */
        version = (opt->ttl & 0x00FF0000) >> 16;
        if (version != 0) {
            ns_client_error(client, DNS_R_BADVERS);
            goto cleanup_serverlock;
        }
    }

    if (client->message->rdclass == 0) {
        ns_client_log(client, NS_LOGCATEGORY_CLIENT,
                  NS_LOGMODULE_CLIENT, ISC_LOG_ERROR,
                  "message class could not be determined");
        ns_client_error(client, DNS_R_FORMERR);
        goto cleanup_serverlock;
    }

    /*
     * Find a view that matches the client's source address.
     *
     * XXXRTH  View list management code will be moving to its own module
     *         soon.
     */
    for (view = ISC_LIST_HEAD(ns_g_server->viewlist);
         view != NULL;
         view = ISC_LIST_NEXT(view, link)) {
        if (client->message->rdclass == view->rdclass ||
            client->message->rdclass == dns_rdataclass_any)
        {
            isc_netaddr_t netaddr;
            int match;
            isc_netaddr_fromsockaddr(&netaddr, &client->peeraddr);
            if (view->matchclients == NULL ||
                (dns_acl_match(&netaddr, NULL, view->matchclients,
                       &ns_g_server->aclenv,
                       &match, NULL) == ISC_R_SUCCESS &&
                 match > 0))
            {
                dns_view_attach(view, &client->view);
                break;
            }
        }
    }

    if (view == NULL) {
        isc_buffer_t b;
        isc_region_t *r;
        r = dns_message_getrawmessage(client->message);
        isc_buffer_init(&b, r->base, r->length);
        isc_buffer_add(&b, r->length);
        (void)dns_tsig_verify(&b, client->message, NULL, NULL);

        ns_client_log(client, NS_LOGCATEGORY_CLIENT,
                  NS_LOGMODULE_CLIENT, ISC_LOG_ERROR,
                  "no matching view");
        ns_client_error(client, DNS_R_REFUSED);
        goto cleanup_serverlock;
    }

    ns_client_log(client, NS_LOGCATEGORY_CLIENT,
              NS_LOGMODULE_CLIENT, ISC_LOG_DEBUG(5),
              "using view '%s'", view->name);

    /*
     * Lock the view's configuration data for reading.
     * We must attach a separate view reference for this
     * purpose instad of using client->view, because
     * client->view may or may not be detached at the point
     * when we return from this event handler depending
     * on whether the request handler causes ns_client_next()
     * to be called or not.
     */
    dns_view_attach(client->view, &client->lockview);
    RWLOCK(&client->lockview->conflock, isc_rwlocktype_read);

    /*
     * Check for a signature.  We log bad signatures regardless of
     * whether they ultimately cause the request to be rejected or
     * not.  We do not log the lack of a signature unless we are
     * debugging.
     */
    sigresult = dns_message_checksig(client->message, client->view);
    client->signer = NULL;
    dns_name_init(&client->signername, NULL);
    result = dns_message_signer(client->message, &client->signername);
    if (result == ISC_R_SUCCESS) {
        ns_client_log(client, DNS_LOGCATEGORY_SECURITY,
                  NS_LOGMODULE_CLIENT, ISC_LOG_DEBUG(3),
                  "request has valid signature");
        client->signer = &client->signername;
    } else if (result == ISC_R_NOTFOUND) {
        ns_client_log(client, DNS_LOGCATEGORY_SECURITY,
                  NS_LOGMODULE_CLIENT, ISC_LOG_DEBUG(3),
                  "request is not signed");
    } else if (result == DNS_R_NOIDENTITY) {
        ns_client_log(client, DNS_LOGCATEGORY_SECURITY,
                  NS_LOGMODULE_CLIENT, ISC_LOG_DEBUG(3),
                  "request is signed by a nonauthoritative key");
        if (client->message->tsigstatus != dns_tsigerror_badkey &&
            client->message->opcode != dns_opcode_update) {
            ns_client_error(client, sigresult);
            goto cleanup_viewlock;
        }
    } else {
        /* There is a signature, but it is bad. */
        ns_client_log(client, DNS_LOGCATEGORY_SECURITY,
                  NS_LOGMODULE_CLIENT, ISC_LOG_ERROR,
                  "request has invalid signature: %s",
                  isc_result_totext(result));
        if (client->message->tsigstatus != dns_tsigerror_badkey &&
            client->message->opcode != dns_opcode_update) {
            ns_client_error(client, sigresult);
            goto cleanup_viewlock;
        }
    }

    /*
     * Decide whether recursive service is available to this client.
     * We do this here rather than in the query code so that we can
     * set the RA bit correctly on all kinds of responses, not just
     * responses to ordinary queries.
     */
    ra = ISC_FALSE;
    if (client->view->resolver != NULL &&
        client->view->recursion == ISC_TRUE &&
        /* XXX this will log too much too early */
        ns_client_checkacl(client, "recursion",
                   client->view->recursionacl,
                   ISC_TRUE, ISC_LOG_DEBUG(1)) == ISC_R_SUCCESS)
        ra = ISC_TRUE;

    if (ra == ISC_TRUE)
        client->attributes |= NS_CLIENTATTR_RA;

    /*
     * Dispatch the request.
     */
    switch (client->message->opcode) {
    case dns_opcode_query:
        CTRACE("query");
        ns_query_start(client);
        break;
    case dns_opcode_update:
        CTRACE("update");
        ns_update_start(client, sigresult);
        break;
    case dns_opcode_notify:
        CTRACE("notify");
        ns_notify_start(client);
        break;
    case dns_opcode_iquery:
        CTRACE("iquery");
        ns_client_error(client, DNS_R_NOTIMP);
        break;
    default:
        CTRACE("unknown opcode");
        ns_client_error(client, DNS_R_NOTIMP);
    }

 cleanup_viewlock:
    RWUNLOCK(&client->lockview->conflock, isc_rwlocktype_read);
    dns_view_detach(&client->lockview);
 cleanup_serverlock:
    dns_zonemgr_unlockconf(ns_g_server->zonemgr, isc_rwlocktype_read);
    RWUNLOCK(&ns_g_server->conflock, isc_rwlocktype_read);
}

static void
client_timeout(isc_task_t *task, isc_event_t *event) {
    ns_client_t *client;

    REQUIRE(event != NULL);
    REQUIRE(event->ev_type == ISC_TIMEREVENT_LIFE ||
        event->ev_type == ISC_TIMEREVENT_IDLE);
    client = event->ev_arg;
    REQUIRE(NS_CLIENT_VALID(client));
    REQUIRE(task == client->task);
    REQUIRE(client->timer != NULL);

    UNUSED(task);

    CTRACE("timeout");

    isc_event_free(&event);

    if (client->shutdown != NULL) {
        (client->shutdown)(client->shutdown_arg, ISC_R_TIMEDOUT);
        client->shutdown = NULL;
        client->shutdown_arg = NULL;
    }

    if (client->newstate > NS_CLIENTSTATE_READY)
        client->newstate = NS_CLIENTSTATE_READY;
    (void) exit_check(client);
}

static isc_result_t
client_create(ns_clientmgr_t *manager, ns_client_t **clientp)
{
    ns_client_t *client;
    isc_result_t result;

    /*
     * Caller must be holding the manager lock.
     *
     * Note: creating a client does not add the client to the
     * manager's client list or set the client's manager pointer.
     * The caller is responsible for that.
     */

    REQUIRE(clientp != NULL && *clientp == NULL);

    client = isc_mem_get(manager->mctx, sizeof *client);
    if (client == NULL)
        return (ISC_R_NOMEMORY);

    client->task = NULL;
    result = isc_task_create(manager->taskmgr, 0, &client->task);
    if (result != ISC_R_SUCCESS)
        goto cleanup_client;
    isc_task_setname(client->task, "client", client);
    result = isc_task_onshutdown(client->task, client_shutdown, client);
    if (result != ISC_R_SUCCESS)
        goto cleanup_task;

    client->timer = NULL;
    result = isc_timer_create(manager->timermgr, isc_timertype_inactive,
                  NULL, NULL, client->task, client_timeout,
                  client, &client->timer);
    if (result != ISC_R_SUCCESS)
        goto cleanup_task;

    client->message = NULL;
    result = dns_message_create(manager->mctx, DNS_MESSAGE_INTENTPARSE,
                    &client->message);
    if (result != ISC_R_SUCCESS)
        goto cleanup_timer;

    /* XXXRTH  Hardwired constants */
    client->sendbuf = isc_mem_get(manager->mctx, SEND_BUFFER_SIZE);
    if  (client->sendbuf == NULL)
        goto cleanup_message;

    client->magic = NS_CLIENT_MAGIC;
    client->mctx = manager->mctx;
    client->manager = NULL;
    client->state = NS_CLIENTSTATE_INACTIVE;
    client->newstate = NS_CLIENTSTATE_MAX;
    client->naccepts = 0;
    client->nreads = 0;
    client->nsends = 0;
    client->references = 0;
    client->attributes = 0;
    client->view = NULL;
    client->lockview = NULL;
    client->dispatch = NULL;
    client->dispentry = NULL;
    client->dispevent = NULL;
    client->tcplistener = NULL;
    client->tcpsocket = NULL;
    client->tcpmsg_valid = ISC_FALSE;
    client->tcpbuf = NULL;
    client->opt = NULL;
    client->udpsize = 512;
    client->next = NULL;
    client->shutdown = NULL;
    client->shutdown_arg = NULL;
    dns_name_init(&client->signername, NULL);
    client->mortal = ISC_FALSE;
    client->tcpquota = NULL;
    client->recursionquota = NULL;
    client->interface = NULL;
    client->peeraddr_valid = ISC_FALSE;
    ISC_EVENT_INIT(&client->ctlevent, sizeof(client->ctlevent), 0, NULL,
               NS_EVENT_CLIENTCONTROL, client_start, client, client,
               NULL, NULL);
    ISC_LINK_INIT(client, link);
    client->list = NULL;

    /*
     * We call the init routines for the various kinds of client here,
     * after we have created an otherwise valid client, because some
     * of them call routines that REQUIRE(NS_CLIENT_VALID(client)).
     */
    result = ns_query_init(client);
    if (result != ISC_R_SUCCESS)
        goto cleanup_sendbuf;

    CTRACE("create");

    *clientp = client;

    return (ISC_R_SUCCESS);

 cleanup_sendbuf:
    isc_mem_put(manager->mctx, client->sendbuf, SEND_BUFFER_SIZE);

    client->magic = 0;

 cleanup_message:
    dns_message_destroy(&client->message);

 cleanup_timer:
    isc_timer_detach(&client->timer);

 cleanup_task:
    isc_task_detach(&client->task);

 cleanup_client:
    isc_mem_put(manager->mctx, client, sizeof *client);

    return (result);
}

static void
client_read(ns_client_t *client) {
    isc_result_t result;

    CTRACE("read");

    result = dns_tcpmsg_readmessage(&client->tcpmsg, client->task,
                    client_request, client);
    if (result != ISC_R_SUCCESS)
        goto fail;

    /*
     * Set a timeout to limit the amount of time we will wait
     * for a request on this TCP connection.
     */
    set_timeout(client, 30);

    client->state = client->newstate = NS_CLIENTSTATE_READING;
    INSIST(client->nreads == 0);
    client->nreads++;

    return;
 fail:
    ns_client_next(client, result);
}

static void
client_newconn(isc_task_t *task, isc_event_t *event) {
    ns_client_t *client = event->ev_arg;
    isc_socket_newconnev_t *nevent = (isc_socket_newconnev_t *)event;
    isc_result_t result;

    REQUIRE(event->ev_type == ISC_SOCKEVENT_NEWCONN);
    REQUIRE(NS_CLIENT_VALID(client));
    REQUIRE(client->task == task);

    UNUSED(task);

    INSIST(client->state == NS_CLIENTSTATE_READY);

    INSIST(client->naccepts == 1);
    client->naccepts--;

    LOCK(&client->interface->lock);
    INSIST(client->interface->ntcpcurrent > 0);
    client->interface->ntcpcurrent--;
    UNLOCK(&client->interface->lock);

    /*
     * We must take ownership of the new socket before the exit
     * check to make sure it gets destroyed if we decide to exit.
     */
    if (nevent->result == ISC_R_SUCCESS) {
        client->tcpsocket = nevent->newsocket;
        client->state = NS_CLIENTSTATE_READING;

        (void) isc_socket_getpeername(client->tcpsocket,
                          &client->peeraddr);
        client->peeraddr_valid = ISC_TRUE;
        ns_client_log(client, NS_LOGCATEGORY_CLIENT,
               NS_LOGMODULE_CLIENT, ISC_LOG_DEBUG(3),
               "new TCP connection");
    } else {
        /*
         * XXXRTH  What should we do?  We're trying to accept but
         *         it didn't work.  If we just give up, then TCP
         *     service may eventually stop.
         *
         *     For now, we just go idle.
         *
         *     Going idle is probably the right thing if the
         *     I/O was canceled.
         */
        ns_client_log(client, NS_LOGCATEGORY_CLIENT,
                  NS_LOGMODULE_CLIENT, ISC_LOG_DEBUG(3),
                  "accept failed: %s",
                  isc_result_totext(nevent->result));
    }

    if (exit_check(client))
        goto freeevent;

    if (nevent->result == ISC_R_SUCCESS) {
        INSIST(client->tcpmsg_valid == ISC_FALSE);
        dns_tcpmsg_init(client->mctx, client->tcpsocket,
                &client->tcpmsg);
        client->tcpmsg_valid = ISC_TRUE;

        /*
         * Let a new client take our place immediately, before
         * we wait for a request packet.  If we don't,
         * telnetting to port 35 (once per CPU) will
         * deny service to legititmate TCP clients.
         */
        result = isc_quota_attach(&ns_g_server->tcpquota,
                      &client->tcpquota);
        if (result == ISC_R_SUCCESS)
            result = ns_client_replace(client);
        if (result != ISC_R_SUCCESS) {
            ns_client_log(client, NS_LOGCATEGORY_CLIENT,
                      NS_LOGMODULE_CLIENT, ISC_LOG_WARNING,
                      "no more TCP clients: %s",
                      isc_result_totext(result));
        }
        client_read(client);
    }

 freeevent:
    isc_event_free(&event);
}

static void
client_accept(ns_client_t *client) {
    isc_result_t result;

    CTRACE("accept");

    result = isc_socket_accept(client->tcplistener, client->task,
                   client_newconn, client);
    if (result != ISC_R_SUCCESS) {
        UNEXPECTED_ERROR(__FILE__, __LINE__,
                 "isc_socket_accept() failed: %s",
                 isc_result_totext(result));
        /*
         * XXXRTH  What should we do?  We're trying to accept but
         *         it didn't work.  If we just give up, then TCP
         *     service may eventually stop.
         *
         *     For now, we just go idle.
         */
        return;
    }
    INSIST(client->naccepts == 0);
    client->naccepts++;
    LOCK(&client->interface->lock);
    client->interface->ntcpcurrent++;
    UNLOCK(&client->interface->lock);
}

void
ns_client_attach(ns_client_t *source, ns_client_t **targetp) {
    REQUIRE(NS_CLIENT_VALID(source));
    REQUIRE(targetp != NULL && *targetp == NULL);

    source->references++;
    ns_client_log(source, NS_LOGCATEGORY_CLIENT,
              NS_LOGMODULE_CLIENT, ISC_LOG_DEBUG(10),
              "ns_client_attach: ref = %d", source->references);
    *targetp = source;
}

void
ns_client_detach(ns_client_t **clientp) {
    ns_client_t *client = *clientp;

    client->references--;
    INSIST(client->references >= 0);
    *clientp = NULL;
    ns_client_log(client, NS_LOGCATEGORY_CLIENT,
              NS_LOGMODULE_CLIENT, ISC_LOG_DEBUG(10),
              "ns_client_detach: ref = %d", client->references);
    (void) exit_check(client);
}

isc_boolean_t
ns_client_shuttingdown(ns_client_t *client) {
    return (ISC_TF(client->newstate == NS_CLIENTSTATE_FREED));
}

isc_result_t
ns_client_replace(ns_client_t *client) {
    isc_result_t result;

    CTRACE("replace");

    result = ns_clientmgr_createclients(client->manager,
                        1, client->interface,
                        (TCP_CLIENT(client) ?
                         ISC_TRUE : ISC_FALSE));
    if (result != ISC_R_SUCCESS)
        return (result);

    /*
     * The responsibility for listening for new requests is hereby
     * transferred to the new client.  Therefore, the old client
     * should refrain from listening for any more requests.
     */
    client->mortal = ISC_TRUE;

    return (ISC_R_SUCCESS);
}

/***
 *** Client Manager
 ***/

static void
clientmgr_destroy(ns_clientmgr_t *manager) {
    REQUIRE(ISC_LIST_EMPTY(manager->active));
    REQUIRE(ISC_LIST_EMPTY(manager->inactive));

    MTRACE("clientmgr_destroy");

    manager->magic = 0;
    isc_mem_put(manager->mctx, manager, sizeof *manager);
}

isc_result_t
ns_clientmgr_create(isc_mem_t *mctx, isc_taskmgr_t *taskmgr,
            isc_timermgr_t *timermgr, ns_clientmgr_t **managerp)
{
    ns_clientmgr_t *manager;
    isc_result_t result;

    manager = isc_mem_get(mctx, sizeof *manager);
    if (manager == NULL)
        return (ISC_R_NOMEMORY);

    result = isc_mutex_init(&manager->lock);
    if (result != ISC_R_SUCCESS)
        goto cleanup_manager;

    manager->mctx = mctx;
    manager->taskmgr = taskmgr;
    manager->timermgr = timermgr;
    manager->exiting = ISC_FALSE;
    ISC_LIST_INIT(manager->active);
    ISC_LIST_INIT(manager->inactive);
    manager->magic = MANAGER_MAGIC;

    MTRACE("create");

    *managerp = manager;

    return (ISC_R_SUCCESS);

 cleanup_manager:
    isc_mem_put(manager->mctx, manager, sizeof *manager);

    return (result);
}

void
ns_clientmgr_destroy(ns_clientmgr_t **managerp) {
    ns_clientmgr_t *manager;
    ns_client_t *client;
    isc_boolean_t need_destroy = ISC_FALSE;

    REQUIRE(managerp != NULL);
    manager = *managerp;
    REQUIRE(VALID_MANAGER(manager));

    MTRACE("destroy");

    LOCK(&manager->lock);

    manager->exiting = ISC_TRUE;

    for (client = ISC_LIST_HEAD(manager->active);
         client != NULL;
         client = ISC_LIST_NEXT(client, link))
        isc_task_shutdown(client->task);

    for (client = ISC_LIST_HEAD(manager->inactive);
         client != NULL;
         client = ISC_LIST_NEXT(client, link))
        isc_task_shutdown(client->task);

    if (ISC_LIST_EMPTY(manager->active) &&
        ISC_LIST_EMPTY(manager->inactive))
        need_destroy = ISC_TRUE;

    UNLOCK(&manager->lock);

    if (need_destroy)
        clientmgr_destroy(manager);

    *managerp = NULL;
}

isc_result_t
ns_clientmgr_createclients(ns_clientmgr_t *manager, unsigned int n,
               ns_interface_t *ifp, isc_boolean_t tcp)
{
    isc_result_t result = ISC_R_SUCCESS;
    unsigned int i;
    ns_client_t *client;

    REQUIRE(VALID_MANAGER(manager));
    REQUIRE(n > 0);

    MTRACE("createclients");

    /*
     * We MUST lock the manager lock for the entire client creation
     * process.  If we didn't do this, then a client could get a
     * shutdown event and disappear out from under us.
     */

    LOCK(&manager->lock);

    for (i = 0; i < n; i++) {
        isc_event_t *ev;
        /*
         * Allocate a client.  First try to get a recycled one;
         * if that fails, make a new one.
         */
        client = ISC_LIST_HEAD(manager->inactive);
        if (client != NULL) {
            MTRACE("recycle");
            ISC_LIST_UNLINK(manager->inactive, client, link);
            client->list = NULL;
        } else {
            MTRACE("create new");
            result = client_create(manager, &client);
            if (result != ISC_R_SUCCESS)
                break;
        }

        client->state = NS_CLIENTSTATE_READY;

        ns_interface_attach(ifp, &client->interface);

        if (tcp) {
            client->attributes |= NS_CLIENTATTR_TCP;
            isc_socket_attach(ifp->tcpsocket,
                      &client->tcplistener);
        } else {
            dns_dispatch_attach(ifp->udpdispatch,
                        &client->dispatch);
        }
        client->manager = manager;
        ISC_LIST_APPEND(manager->active, client, link);
        client->list = &manager->active;

        ev = &client->ctlevent;
        isc_task_send(client->task, &ev);
    }
    if (i != 0) {
        /*
         * We managed to create at least one client, so we
         * declare victory.
         */
        result = ISC_R_SUCCESS;
    }

    UNLOCK(&manager->lock);

    return (result);
}

isc_sockaddr_t *
ns_client_getsockaddr(ns_client_t *client) {
    return (&client->peeraddr);
}

isc_result_t
ns_client_checkacl(ns_client_t  *client,
           const char *opname, dns_acl_t *acl,
           isc_boolean_t default_allow, int log_level)
{
    isc_result_t result;
    int match;
    isc_netaddr_t netaddr;

    if (acl == NULL) {
        if (default_allow)
            goto allow;
        else
            goto deny;
    }

    isc_netaddr_fromsockaddr(&netaddr, &client->peeraddr);

    result = dns_acl_match(&netaddr, client->signer, acl,
                   &ns_g_server->aclenv,
                   &match, NULL);
    if (result != ISC_R_SUCCESS)
        goto deny; /* Internal error, already logged. */
    if (match > 0)
        goto allow;
    goto deny; /* Negative match or no match. */

 allow:
    ns_client_log(client, DNS_LOGCATEGORY_SECURITY,
              NS_LOGMODULE_CLIENT, ISC_LOG_DEBUG(3),
              "%s approved", opname);
    return (ISC_R_SUCCESS);

 deny:
    ns_client_log(client, DNS_LOGCATEGORY_SECURITY,
              NS_LOGMODULE_CLIENT,
              log_level, "%s denied", opname);
    return (DNS_R_REFUSED);
}

static void
ns_client_logv(ns_client_t *client, isc_logcategory_t *category,
       isc_logmodule_t *module, int level, const char *fmt, va_list ap)
{
    char msgbuf[2048];
    char peerbuf[256];

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

    if (client->peeraddr_valid) {
        isc_sockaddr_format(&client->peeraddr,
                    peerbuf, sizeof peerbuf);
        isc_log_write(ns_g_lctx, category, module, level,
                  "client %s: %s", peerbuf, msgbuf);
    } else {
        isc_log_write(ns_g_lctx, category, module, level,
                  "client @%p: %s", client, msgbuf);
    }
}

void
ns_client_log(ns_client_t *client, isc_logcategory_t *category,
       isc_logmodule_t *module, int level, const char *fmt, ...)
{
    va_list ap;

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

    va_start(ap, fmt);
    ns_client_logv(client, category, module, level, fmt, ap);
    va_end(ap);
}