Add BIND 9.2.4rc7.

[dragonfly.git] / contrib / bind-9.2.4rc7 / bin / named / client.c

/*
 * 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: client.c,v 1.176.2.16 2004/07/23 02:56:59 marka Exp $ */

#include <config.h>

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

#include <dns/db.h>
#include <dns/dispatch.h>
#include <dns/events.h>
#include <dns/message.h>
#include <dns/rdata.h>
#include <dns/rdataclass.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                4096
#define RECV_BUFFER_SIZE                4096

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                   ISC_MAGIC('N', 'S', 'C', 'm')
#define VALID_MANAGER(m)                ISC_MAGIC_VALID(m, 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 outstanding TCP listen request.
 *
 * If it is a UDP client object, it has a UDP listener socket
 * and an outstanding UDP receive 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.
 */

#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 client_udprecv(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);
static void ns_client_dumpmessage(ns_client_t *client, const char *reason);

void
ns_client_settimeout(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);
        client->timerset = ISC_TRUE;
        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) {
        ns_clientmgr_t *locked_manager = NULL;
        ns_clientmgr_t *destroy_manager = NULL;

        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
         *
         * Keep the view attached until any outstanding updates complete.
         */
        if (client->nupdates == 0 && 
            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);
                /*
                 * Let the update processing complete.
                 */
                if (client->nupdates > 0)
                        return (ISC_TRUE);
                /*
                 * We are trying to abort request processing.
                 */
                if (client->nsends > 0) {
                        isc_socket_t *socket;
                        if (TCP_CLIENT(client))
                                socket = client->tcpsocket;
                        else
                                socket = client->udpsocket;
                        isc_socket_cancel(socket, client->task,
                                          ISC_SOCKCANCEL_SEND);
                }

                if (! (client->nsends == 0 && client->nrecvs == 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;
                INSIST(client->recursionquota == NULL);
                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->recursionquota == NULL);
                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);

                if (client->timerset) {
                        (void) isc_timer_reset(client->timer,
                                               isc_timertype_inactive,
                                               NULL, NULL, ISC_TRUE);
                        client->timerset = ISC_FALSE;
                }

                client->peeraddr_valid = ISC_FALSE;

                client->state = NS_CLIENTSTATE_READY;
                INSIST(client->recursionquota == NULL);

                /*
                 * 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
                                client_udprecv(client);
                        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. */

                if (client->nrecvs > 0)
                        isc_socket_cancel(client->udpsocket, client->task,
                                          ISC_SOCKCANCEL_RECV);
                if (! (client->nrecvs == 0)) {
                        /* Still waiting for recv cancel completion. */
                        return (ISC_TRUE);
                }
                /* Recv cancel is complete. */

                if (client->nctls > 0) {
                        /* Still waiting for control event to be delivered */
                        return (ISC_TRUE);
                }

                /* Deactivate the client. */
                if (client->interface)
                        ns_interface_detach(&client->interface);

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

                if (client->udpsocket != NULL)
                        isc_socket_detach(&client->udpsocket);

                if (client->dispatch != NULL)
                        dns_dispatch_detach(&client->dispatch);

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

                LOCK(&client->manager->lock);
                /*
                 * Put the client on the inactive list.  If we are aiming for
                 * the "freed" state, it will be removed from the inactive
                 * list shortly, and we need to keep the manager locked until
                 * that has been done, lest the manager decide to reactivate
                 * the dying client inbetween.
                 */
                locked_manager = client->manager;
                ISC_LIST_UNLINK(*client->list, client, link);
                ISC_LIST_APPEND(client->manager->inactive, client, link);
                client->list = &client->manager->inactive;
                client->state = NS_CLIENTSTATE_INACTIVE;
                INSIST(client->recursionquota == NULL);

                if (client->state == client->newstate) {
                        client->newstate = NS_CLIENTSTATE_MAX;
                        goto unlock;
                }
        }

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

                INSIST(client->recursionquota == NULL);

                ns_query_free(client);
                isc_mem_put(client->mctx, client->recvbuf, RECV_BUFFER_SIZE);
                isc_event_free((isc_event_t **)&client->sendevent);
                isc_event_free((isc_event_t **)&client->recvevent);
                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->manager != NULL) {
                        ns_clientmgr_t *manager = client->manager;
                        if (locked_manager == NULL) {
                                LOCK(&manager->lock);
                                locked_manager = manager;
                        }
                        ISC_LIST_UNLINK(*client->list, client, link);
                        client->list = NULL;
                        if (manager->exiting &&
                            ISC_LIST_EMPTY(manager->active) &&
                            ISC_LIST_EMPTY(manager->inactive))
                                destroy_manager = manager;
                }
                /*
                 * Detaching the task must be done after unlinking from
                 * the manager's lists because the manager accesses
                 * client->task.
                 */
                if (client->task != NULL)
                        isc_task_detach(&client->task);

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

                goto unlock;
        }

 unlock:
        if (locked_manager != NULL) {
                UNLOCK(&locked_manager->lock);
                locked_manager = NULL;
        }

        /*
         * Only now is it safe to destroy the client manager (if needed),
         * because we have accessed its lock for the last time.
         */
        if (destroy_manager != NULL)
                clientmgr_destroy(destroy_manager);

        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;

        INSIST(task == client->task);

        UNUSED(task);

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

        if (exit_check(client))
                return;

        if (TCP_CLIENT(client)) {
                client_accept(client);
        } else {
                client_udprecv(client);
        }
}


/*
 * 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->nrecvs == 0);
        INSIST(client->nupdates == 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;
        client->extflags = 0;
        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 ||
                client->state == NS_CLIENTSTATE_READING);

        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);
        REQUIRE(sevent == client->sendevent);

        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;
        }

        if (exit_check(client))
                return;

        ns_client_next(client, ISC_R_SUCCESS);
}

/*
 * We only want to fail with ISC_R_NOSPACE when called from
 * ns_client_sendraw() and not when called from ns_client_send(),
 * tcpbuffer is NULL when called from ns_client_sendraw() and
 * length != 0.  tcpbuffer != NULL when called from ns_client_send()
 * and length == 0.
 */

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

        INSIST(datap != NULL);
        INSIST((tcpbuffer == NULL && length != 0) ||
               (tcpbuffer != NULL && length == 0));

        if (TCP_CLIENT(client)) {
                INSIST(client->tcpbuf == NULL);
                if (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);
                        INSIST(length <= 0xffff);
                        isc_buffer_putuint16(buffer, (isc_uint16_t)length);
                }
        } else {
                data = sendbuf;
                if (client->udpsize < SEND_BUFFER_SIZE)
                        bufsize = client->udpsize;
                else
                        bufsize = SEND_BUFFER_SIZE;
                if (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;
        isc_netaddr_t netaddr;
        int match;
        unsigned int sockflags = ISC_SOCKFLAG_IMMEDIATE;

        if (TCP_CLIENT(client)) {
                socket = client->tcpsocket;
                address = NULL;
        } else {
                socket = client->udpsocket;
                address = &client->peeraddr;

                isc_netaddr_fromsockaddr(&netaddr, &client->peeraddr);
                if (ns_g_server->blackholeacl != NULL &&
                    dns_acl_match(&netaddr, NULL,
                                  ns_g_server->blackholeacl,
                                  &ns_g_server->aclenv,
                                  &match, NULL) == ISC_R_SUCCESS &&
                    match > 0)
                        return (DNS_R_BLACKHOLED);
                sockflags |= ISC_SOCKFLAG_NORETRY;
        }

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

        isc_buffer_usedregion(buffer, &r);

        CTRACE("sendto");
        
        result = isc_socket_sendto2(socket, &r, client->task,
                                    address, pktinfo,
                                    client->sendevent, sockflags);
        if (result == ISC_R_SUCCESS || result == ISC_R_INPROGRESS) {
                client->nsends++;
                if (result == ISC_R_SUCCESS)
                        client_senddone(client->task,
                                        (isc_event_t *)client->sendevent);
                result = ISC_R_SUCCESS;
        }
        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;
        unsigned char sendbuf[SEND_BUFFER_SIZE];

        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,
                                     sendbuf, &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;
        dns_compress_t cctx;
        isc_boolean_t cleanup_cctx = ISC_FALSE;
        unsigned char sendbuf[SEND_BUFFER_SIZE];

        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 TCP buffer resizing.
         */
        result = client_allocsendbuf(client, &buffer, &tcpbuffer, 0,
                                     sendbuf, &data);
        if (result != ISC_R_SUCCESS)
                goto done;

        result = dns_compress_init(&cctx, -1, client->mctx);
        if (result != ISC_R_SUCCESS)
                goto done;
        cleanup_cctx = ISC_TRUE;

        result = dns_message_renderbegin(client->message, &cctx, &buffer);
        if (result != ISC_R_SUCCESS)
                goto done;
        if (client->opt != NULL) {
                result = dns_message_setopt(client->message, client->opt);
                /*
                 * XXXRTH dns_message_setopt() should probably do this...
                 */
                client->opt = NULL;
                if (result != ISC_R_SUCCESS)
                        goto done;
        }
        result = dns_message_rendersection(client->message,
                                           DNS_SECTION_QUESTION, 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_ANSWER,
                                           DNS_MESSAGERENDER_PARTIAL);
        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,
                                           DNS_MESSAGERENDER_PARTIAL);
        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 (cleanup_cctx) {
                dns_compress_invalidate(&cctx);
                cleanup_cctx = ISC_FALSE;
        }

        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;
        }

        if (cleanup_cctx)
                dns_compress_invalidate(&cctx);

        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;

        /*
         * FORMERR loop avoidance:  If we sent a FORMERR message
         * with the same ID to the same client less than two
         * seconds ago, assume that we are in an infinite error 
         * packet dialog with a server for some protocol whose 
         * error responses look enough like DNS queries to
         * elicit a FORMERR response.  Drop a packet to break
         * the loop.
         */
        if (rcode == dns_rcode_formerr) {
                if (isc_sockaddr_equal(&client->peeraddr,
                                       &client->formerrcache.addr) &&
                    message->id == client->formerrcache.id &&
                    client->requesttime - client->formerrcache.time < 2) {
                        /* Drop packet. */
                        ns_client_log(client, NS_LOGCATEGORY_CLIENT,
                                      NS_LOGMODULE_CLIENT, ISC_LOG_DEBUG(1),
                                      "possible error packet loop, "
                                      "FORMERR dropped");
                        ns_client_next(client, result);
                        return;
                }
                client->formerrcache.addr = client->peeraddr;
                client->formerrcache.time = client->requesttime;
                client->formerrcache.id = message->id;
        }
        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 the maximum UDP buffer size.
         */
        rdatalist->rdclass = RECV_BUFFER_SIZE;

        /*
         * Set EXTENDED-RCODE, VERSION, and Z to 0.
         */
#ifdef ISC_RFC2535
        rdatalist->ttl = (client->extflags & DNS_MESSAGEEXTFLAG_REPLYPRESERVE);
#else
        rdatalist->ttl = 0;
#endif

        /*
         * No ENDS options in the default case.
         */
        rdata->data = NULL;
        rdata->length = 0;
        rdata->rdclass = rdatalist->rdclass;
        rdata->type = rdatalist->type;
        rdata->flags = 0;

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

        client->opt = rdataset;

        return (ISC_R_SUCCESS);
}

static inline isc_boolean_t
allowed(isc_netaddr_t *addr, dns_acl_t *acl) {
        int match;
        isc_result_t result;

        if (acl == NULL)
                return (ISC_TRUE);
        result = dns_acl_match(addr, NULL, acl, &ns_g_server->aclenv,
                               &match, NULL);
        if (result == ISC_R_SUCCESS && match > 0)
                return (ISC_TRUE);
        return (ISC_FALSE);
}

/*
 * Handle an incoming request event from the socket (UDP case)
 * or tcpmsg (TCP case).
 */
static void
client_request(isc_task_t *task, isc_event_t *event) {
        ns_client_t *client;
        isc_socketevent_t *sevent;
        isc_result_t result;
        isc_result_t sigresult;
        isc_buffer_t *buffer;
        isc_buffer_t tbuffer;
        dns_view_t *view;
        dns_rdataset_t *opt;
        isc_boolean_t ra;       /* Recursion available. */
        isc_netaddr_t netaddr;
        isc_netaddr_t destaddr;
        int match;
        dns_messageid_t id;
        unsigned int flags;
        isc_boolean_t notimp;

        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);

        if (event->ev_type == ISC_SOCKEVENT_RECVDONE) {
                INSIST(!TCP_CLIENT(client));
                sevent = (isc_socketevent_t *)event;
                REQUIRE(sevent == client->recvevent);
                isc_buffer_init(&tbuffer, sevent->region.base, sevent->n);
                isc_buffer_add(&tbuffer, sevent->n);
                buffer = &tbuffer;
                result = sevent->result;
                if (result == ISC_R_SUCCESS) {
                        client->peeraddr = sevent->address;
                        client->peeraddr_valid = ISC_TRUE;
                }
                if ((sevent->attributes & ISC_SOCKEVENTATTR_PKTINFO) != 0) {
                        client->attributes |= NS_CLIENTATTR_PKTINFO;
                        client->pktinfo = sevent->pktinfo;
                }
                if ((sevent->attributes & ISC_SOCKEVENTATTR_MULTICAST) != 0)
                        client->attributes |= NS_CLIENTATTR_MULTICAST;
                client->nrecvs--;
        } 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--;
        }

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

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

        if (result != ISC_R_SUCCESS) {
                if (TCP_CLIENT(client)) {
                        ns_client_next(client, result);
                } else {
                        if  (result != ISC_R_CANCELED)
                                isc_log_write(ns_g_lctx, NS_LOGCATEGORY_CLIENT,
                                              NS_LOGMODULE_CLIENT,
                                              ISC_LOG_ERROR,
                                              "UDP client handler shutting "
                                              "down due to fatal receive "
                                              "error: %s",
                                              isc_result_totext(result));
                        isc_task_shutdown(client->task);
                }
                goto cleanup;
        }

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

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

        /*
         * Check the blackhole ACL for UDP only, since TCP is done in
         * client_newconn.
         */
        if (!TCP_CLIENT(client)) {

                if (ns_g_server->blackholeacl != NULL &&
                    dns_acl_match(&netaddr, NULL, ns_g_server->blackholeacl,
                                  &ns_g_server->aclenv,
                                  &match, NULL) == ISC_R_SUCCESS &&
                    match > 0)
                {
                        ns_client_log(client, DNS_LOGCATEGORY_SECURITY,
                                      NS_LOGMODULE_CLIENT, ISC_LOG_DEBUG(10),
                                      "blackholed UDP datagram");
                        ns_client_next(client, ISC_R_SUCCESS);
                        goto cleanup;
                }
        }

        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_peekheader(buffer, &id, &flags);
        if (result != ISC_R_SUCCESS) {
                /*
                 * There isn't enough header to determine whether
                 * this was a request or a response.  Drop it.
                 */
                ns_client_next(client, result);
                goto cleanup;
        }

        /*
         * The client object handles requests, not responses.
         * If this is a UDP response, forward it to the dispatcher.
         * If it's a TCP response, discard it here.
         */
        if ((flags & DNS_MESSAGEFLAG_QR) != 0) {
                if (TCP_CLIENT(client)) {
                        CTRACE("unexpected response");
                        ns_client_next(client, DNS_R_FORMERR);
                        goto cleanup;
                } else {
                        dns_dispatch_importrecv(client->dispatch, event);
                        ns_client_next(client, ISC_R_SUCCESS);
                        goto cleanup;
                }
        }

        /*
         * It's a request.  Parse it.
         */
        result = dns_message_parse(client->message, buffer, 0);
        if (result != ISC_R_SUCCESS) {
                /*
                 * Parsing the request failed.  Send a response
                 * (typically FORMERR or SERVFAIL).
                 */
                ns_client_error(client, result);
                goto cleanup;
        }

        switch (client->message->opcode) {
        case dns_opcode_query:
        case dns_opcode_update:
        case dns_opcode_notify:
                notimp = ISC_FALSE;
                break;
        case dns_opcode_iquery:
        default:
                notimp = ISC_TRUE;
                break;
        }

        client->message->rcode = dns_rcode_noerror;

        /*
         * 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;

                /*
                 * If the requested UDP buffer size is less than 512,
                 * ignore it and use 512.
                 */
                if (client->udpsize < 512)
                        client->udpsize = 512;

                /*
                 * Get the flags out of the OPT record.
                 */
                client->extflags = (isc_uint16_t)(opt->ttl & 0xFFFF);

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

                /*
                 * 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;
                }
        }

        if (client->message->rdclass == 0) {
                ns_client_log(client, NS_LOGCATEGORY_CLIENT,
                              NS_LOGMODULE_CLIENT, ISC_LOG_DEBUG(1),
                              "message class could not be determined");
                ns_client_dumpmessage(client,
                                      "message class could not be determined");
                ns_client_error(client, notimp ? DNS_R_NOTIMP : DNS_R_FORMERR);
                goto cleanup;
        }

        /*
         * Determine the destination address.  For TCP/IPv6, we get this from
         * the receiving socket.  For UDP/IPv6, we get it from the pktinfo
         * structure (if supported).  For IPv4, we have to do with
         * the address of the interface where the request was received.
         */
        if (client->interface->addr.type.sa.sa_family == AF_INET6) {
                result = ISC_R_FAILURE;

                if (TCP_CLIENT(client)) {
                        isc_sockaddr_t destsockaddr;

                        result = isc_socket_getsockname(client->tcpsocket,
                                                        &destsockaddr);
                        if (result == ISC_R_SUCCESS)
                                isc_netaddr_fromsockaddr(&destaddr,
                                                         &destsockaddr);
                }
                if (result != ISC_R_SUCCESS &&
                    (client->attributes & NS_CLIENTATTR_PKTINFO) != 0) {
                        isc_netaddr_fromin6(&destaddr, &client->pktinfo.ipi6_addr);
                        result = ISC_R_SUCCESS;
                }
                if (result != ISC_R_SUCCESS) {
                        UNEXPECTED_ERROR(__FILE__, __LINE__,
                                         "failed to get request's "
                                         "destination: %s",
                                         isc_result_totext(result));
                        goto cleanup;
                }
        } else {
                isc_netaddr_fromsockaddr(&destaddr, &client->interface->addr);
        }

        /*
         * Find a view that matches the client's source address.
         */
        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)
                {
                        if (allowed(&netaddr, view->matchclients) &&
                            allowed(&destaddr, view->matchdestinations) &&
                            !((flags & DNS_MESSAGEFLAG_RD) == 0 &&
                              view->matchrecursiveonly))
                        {
                                dns_view_attach(view, &client->view);
                                break;
                        }
                }
        }

        if (view == NULL) {
                char classname[DNS_RDATACLASS_FORMATSIZE];

                /*
                 * Do a dummy TSIG verification attempt so that the
                 * response will have a TSIG if the query did, as
                 * required by RFC2845.
                 */
                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);

                dns_rdataclass_format(client->message->rdclass, classname,
                                      sizeof(classname));
                ns_client_log(client, NS_LOGCATEGORY_CLIENT,
                              NS_LOGMODULE_CLIENT, ISC_LOG_DEBUG(1),
                              "no matching view in class '%s'", classname);
                ns_client_dumpmessage(client, "no matching view in class");
                ns_client_error(client, notimp ? DNS_R_NOTIMP : DNS_R_REFUSED);
                goto cleanup;
        }

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

        /*
         * 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");
        } 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));
                /*
                 * Accept update messages signed by unknown keys so that
                 * update forwarding works transparently through slaves
                 * that don't have all the same keys as the master.
                 */
                if (!(client->message->tsigstatus == dns_tsigerror_badkey &&
                      client->message->opcode == dns_opcode_update)) {
                        ns_client_error(client, sigresult);
                        goto cleanup;
                }
        }

        /*
         * 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 available:",
                               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_client_settimeout(client, 60);
                ns_update_start(client, sigresult);
                break;
        case dns_opcode_notify:
                CTRACE("notify");
                ns_client_settimeout(client, 60);
                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:
        return;
}

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);

        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->timerset = ISC_FALSE;

        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->sendevent = (isc_socketevent_t *)
                            isc_event_allocate(manager->mctx, client,
                                               ISC_SOCKEVENT_SENDDONE,
                                               client_senddone, client,
                                               sizeof(isc_socketevent_t));
        if (client->sendevent == NULL) {
                result = ISC_R_NOMEMORY;
                goto cleanup_message;
        }

        client->recvbuf = isc_mem_get(manager->mctx, RECV_BUFFER_SIZE);
        if  (client->recvbuf == NULL) {
                result = ISC_R_NOMEMORY;
                goto cleanup_sendevent;
        }

        client->recvevent = (isc_socketevent_t *)
                            isc_event_allocate(manager->mctx, client,
                                               ISC_SOCKEVENT_RECVDONE,
                                               client_request, client,
                                               sizeof(isc_socketevent_t));
        if (client->recvevent == NULL) {
                result = ISC_R_NOMEMORY;
                goto cleanup_recvbuf;
        }

        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->nrecvs = 0;
        client->nupdates = 0;
        client->nctls = 0;
        client->references = 0;
        client->attributes = 0;
        client->view = NULL;
        client->dispatch = NULL;
        client->udpsocket = NULL;
        client->tcplistener = NULL;
        client->tcpsocket = NULL;
        client->tcpmsg_valid = ISC_FALSE;
        client->tcpbuf = NULL;
        client->opt = NULL;
        client->udpsize = 512;
        client->extflags = 0;
        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);
        /*
         * Initialize FORMERR cache to sentinel value that will not match
         * any actual FORMERR response.
         */
        isc_sockaddr_any(&client->formerrcache.addr);
        client->formerrcache.time = 0;
        client->formerrcache.id = 0;
        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_recvevent;

        result = isc_task_onshutdown(client->task, client_shutdown, client);
        if (result != ISC_R_SUCCESS)
                goto cleanup_query;

        CTRACE("create");

        *clientp = client;

        return (ISC_R_SUCCESS);

 cleanup_query:
        ns_query_free(client);

 cleanup_recvevent:
        isc_event_free((isc_event_t **)&client->recvevent);

 cleanup_recvbuf:
        isc_mem_put(manager->mctx, client->recvbuf, RECV_BUFFER_SIZE);

 cleanup_sendevent:
        isc_event_free((isc_event_t **)&client->sendevent);

        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.
         */
        ns_client_settimeout(client, 30);

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

                (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) {
                int match;
                isc_netaddr_t netaddr;

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

                if (ns_g_server->blackholeacl != NULL &&
                    dns_acl_match(&netaddr, NULL,
                                  ns_g_server->blackholeacl,
                                  &ns_g_server->aclenv,
                                  &match, NULL) == ISC_R_SUCCESS &&
                    match > 0)
                {
                        ns_client_log(client, DNS_LOGCATEGORY_SECURITY,
                                      NS_LOGMODULE_CLIENT, ISC_LOG_DEBUG(10),
                                      "blackholed connection attempt");
                        client->newstate = NS_CLIENTSTATE_READY;
                        (void)exit_check(client);
                        goto freeevent;
                }

                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 53 (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);
}

static void
client_udprecv(ns_client_t *client) {
        isc_result_t result;
        isc_region_t r;

        CTRACE("udprecv");

        r.base = client->recvbuf;
        r.length = RECV_BUFFER_SIZE;
        result = isc_socket_recv2(client->udpsocket, &r, 1,
                                  client->task, client->recvevent, 0);
        if (result != ISC_R_SUCCESS) {
                UNEXPECTED_ERROR(__FILE__, __LINE__,
                                 "isc_socket_recv() failed: %s",
                                 isc_result_totext(result));
                /*
                 * This cannot happen in the current implementation, since
                 * isc_socket_recv2() cannot fail if flags == 0A
                 *
                 * If this does fail, we just go idle.
                 */
                return;
        }
        INSIST(client->nrecvs == 0);
        client->nrecvs++;
}

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");

        DESTROYLOCK(&manager->lock);
        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;
                }

                ns_interface_attach(ifp, &client->interface);
                client->state = NS_CLIENTSTATE_READY;
                INSIST(client->recursionquota == NULL);

                if (tcp) {
                        client->attributes |= NS_CLIENTATTR_TCP;
                        isc_socket_attach(ifp->tcpsocket,
                                          &client->tcplistener);
                } else {
                        isc_socket_t *sock;

                        dns_dispatch_attach(ifp->udpdispatch,
                                            &client->dispatch);
                        sock = dns_dispatch_getsocket(client->dispatch);
                        isc_socket_attach(sock, &client->udpsocket);
                }
                client->manager = manager;
                ISC_LIST_APPEND(manager->active, client, link);
                client->list = &manager->active;

                INSIST(client->nctls == 0);
                client->nctls++;
                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_checkaclsilent(ns_client_t *client, dns_acl_t *acl,
                         isc_boolean_t default_allow)
{
        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:
        return (ISC_R_SUCCESS);

 deny:
        return (DNS_R_REFUSED);
}

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 =
                ns_client_checkaclsilent(client, acl, default_allow);

        if (result == ISC_R_SUCCESS) 
                ns_client_log(client, DNS_LOGCATEGORY_SECURITY,
                              NS_LOGMODULE_CLIENT, ISC_LOG_DEBUG(3),
                              "%s approved", opname);
        else
                ns_client_log(client, DNS_LOGCATEGORY_SECURITY,
                              NS_LOGMODULE_CLIENT,
                              log_level, "%s denied", opname);
        return (result);
}

static void
ns_client_name(ns_client_t *client, char *peerbuf, size_t len) {
        if (client->peeraddr_valid)
                isc_sockaddr_format(&client->peeraddr, peerbuf, len);
        else
                snprintf(peerbuf, len, "@%p", client);
}

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)
     ISC_FORMAT_PRINTF(5, 0);

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[ISC_SOCKADDR_FORMATSIZE];

        vsnprintf(msgbuf, sizeof(msgbuf), fmt, ap);
        ns_client_name(client, peerbuf, sizeof peerbuf);

        isc_log_write(ns_g_lctx, category, module, level,
                      "client %s: %s", peerbuf, 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);
}

void
ns_client_aclmsg(const char *msg, dns_name_t *name, dns_rdataclass_t rdclass,
                 char *buf, size_t len) 
{
        char namebuf[DNS_NAME_FORMATSIZE];
        char classbuf[DNS_RDATACLASS_FORMATSIZE];

        dns_name_format(name, namebuf, sizeof(namebuf));
        dns_rdataclass_format(rdclass, classbuf, sizeof(classbuf));
        (void)snprintf(buf, len, "%s '%s/%s'", msg, namebuf, classbuf);
}

static void
ns_client_dumpmessage(ns_client_t *client, const char *reason) {
        isc_buffer_t buffer;
        char *buf = NULL;
        int len = 1024;
        isc_result_t result;

        /*
         * Note that these are multiline debug messages.  We want a newline
         * to appear in the log after each message.
         */

        do {
                buf = isc_mem_get(client->mctx, len);
                if (buf == NULL)
                        break;
                isc_buffer_init(&buffer, buf, len);
                result = dns_message_totext(client->message,
                                            &dns_master_style_debug,
                                            0, &buffer);
                if (result == ISC_R_NOSPACE) {
                        isc_mem_put(client->mctx, buf, len);
                        len += 1024;
                } else if (result == ISC_R_SUCCESS)
                        ns_client_log(client, NS_LOGCATEGORY_UNMATCHED,
                                      NS_LOGMODULE_CLIENT, ISC_LOG_DEBUG(1),
                                      "%s\n%.*s", reason,
                                       (int)isc_buffer_usedlength(&buffer),
                                       buf);
        } while (result == ISC_R_NOSPACE);

        if (buf != NULL)
                isc_mem_put(client->mctx, buf, len);
}