bin/named/client.c

	client.c revision f4a9c9226ac7b46d4078cb08645e6354e8f58397
/*
 * Copyright (C) 2004-2014  Internet Systems Consortium, Inc. ("ISC")
 * Copyright (C) 1999-2003  Internet Software Consortium.
 *
 * Permission to use, copy, modify, and/or 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.
 */

#include <config.h>

#include <isc/formatcheck.h>
#include <isc/mutex.h>
#include <isc/once.h>
#include <isc/platform.h>
#include <isc/print.h>
#include <isc/queue.h>
#include <isc/random.h>
#include <isc/serial.h>
#include <isc/stats.h>
#include <isc/stdio.h>
#include <isc/string.h>
#include <isc/task.h>
#include <isc/timer.h>
#include <isc/util.h>

#ifdef AES_SIT
#include <isc/aes.h>
#else
#include <isc/hmacsha.h>
#endif

#include <dns/badcache.h>
#include <dns/db.h>
#include <dns/dispatch.h>
#include <dns/edns.h>
#include <dns/events.h>
#include <dns/message.h>
#include <dns/peer.h>
#include <dns/rcode.h>
#include <dns/rdata.h>
#include <dns/rdataclass.h>
#include <dns/rdatalist.h>
#include <dns/rdataset.h>
#include <dns/resolver.h>
#include <dns/stats.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/os.h>
#include <named/server.h>
#include <named/update.h>

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

/*! \file
 * Client Routines
 *
 * 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

#ifdef ISC_PLATFORM_USETHREADS
#define NMCTXS              100
/*%<
 * Number of 'mctx pools' for clients. (Should this be configurable?)
 * When enabling threads, we use a pool of memory contexts shared by
 * client objects, since concurrent access to a shared context would cause
 * heavy contentions.  The above constant is expected to be enough for
 * completely avoiding contentions among threads for an authoritative-only
 * server.
 */
#else
#define NMCTXS              0
/*%<
 * If named with built without thread, simply share manager's context.  Using
 * a separate context in this case would simply waste memory.
 */
#endif

#define SIT_SIZE 24U /* 8 + 4 + 4 + 8 */
#define ECS_SIZE 20U /* 2 + 1 + 1 + [0..16] */

/*% nameserver client manager structure */
struct ns_clientmgr {
    /* Unlocked. */
    unsigned int            magic;

    /* The queue object has its own locks */
    client_queue_t          inactive;     /*%< To be recycled */

    isc_mem_t *         mctx;
    isc_taskmgr_t *         taskmgr;
    isc_timermgr_t *        timermgr;

    /* Lock covers manager state. */
    isc_mutex_t         lock;
    isc_boolean_t           exiting;

    /* Lock covers the clients list */
    isc_mutex_t         listlock;
    client_list_t           clients;      /*%< All active clients */

    /* Lock covers the recursing list */
    isc_mutex_t         reclock;
    client_list_t           recursing;    /*%< Recursing clients */

#if NMCTXS > 0
    /*%< mctx pool for clients. */
    unsigned int            nextmctx;
    isc_mem_t *         mctxpool[NMCTXS];
#endif
};

#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_RECURSING  5
/*%<
 * The client object is recursing.  It will be on the 'recursing'
 * list.
 */

#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.
 */

/*
 * Enable ns_client_dropport() by default.
 */
#ifndef NS_CLIENT_DROPPORT
#define NS_CLIENT_DROPPORT 1
#endif

unsigned int ns_client_requests;

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 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);
static isc_result_t get_client(ns_clientmgr_t *manager, ns_interface_t *ifp,
                   dns_dispatch_t *disp, isc_boolean_t tcp);
static inline isc_boolean_t
allowed(isc_netaddr_t *addr, dns_name_t *signer, isc_netaddr_t *ecs_addr,
    isc_uint8_t ecs_addrlen, isc_uint8_t *ecs_scope, dns_acl_t *acl);
#ifdef ISC_PLATFORM_USESIT
static void compute_sit(ns_client_t *client, isc_uint32_t when,
            isc_uint32_t nonce, isc_buffer_t *buf);
#endif

void
ns_client_recursing(ns_client_t *client) {
    REQUIRE(NS_CLIENT_VALID(client));
    REQUIRE(client->state == NS_CLIENTSTATE_WORKING);

    LOCK(&client->manager->reclock);
    client->newstate = client->state = NS_CLIENTSTATE_RECURSING;
    ISC_LIST_APPEND(client->manager->recursing, client, rlink);
    UNLOCK(&client->manager->reclock);
}

void
ns_client_killoldestquery(ns_client_t *client) {
    ns_client_t *oldest;
    REQUIRE(NS_CLIENT_VALID(client));

    LOCK(&client->manager->reclock);
    oldest = ISC_LIST_HEAD(client->manager->recursing);
    if (oldest != NULL) {
        ISC_LIST_UNLINK(client->manager->recursing, oldest, rlink);
        UNLOCK(&client->manager->reclock);
        ns_query_cancel(oldest);
    } else
        UNLOCK(&client->manager->reclock);
}

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) {
    isc_boolean_t destroy_manager = ISC_FALSE;
    ns_clientmgr_t *manager = NULL;

    REQUIRE(NS_CLIENT_VALID(client));
    manager = client->manager;

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

    INSIST(client->newstate < NS_CLIENTSTATE_RECURSING);

    /*
     * 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 ||
        client->state == NS_CLIENTSTATE_RECURSING)
    {
        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.  Ensure that
         * the client is no longer on the recursing list.
         *
         * We need to check whether the client is still linked,
         * because it may already have been removed from the
         * recursing list by ns_client_killoldestquery()
         */
        if (client->state == NS_CLIENTSTATE_RECURSING) {
            LOCK(&manager->reclock);
            if (ISC_LINK_LINKED(client, rlink))
                ISC_LIST_UNLINK(manager->recursing,
                        client, rlink);
            UNLOCK(&manager->reclock);
        }
        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.
         *
         * UDP clients go inactive at this point, but TCP clients
         * may remain active if we have fewer active TCP client
         * objects than desired due to an earlier quota exhaustion.
         */
        if (client->mortal && TCP_CLIENT(client) && !ns_g_clienttest) {
            LOCK(&client->interface->lock);
            if (client->interface->ntcpcurrent <
                    client->interface->ntcptarget)
                client->mortal = ISC_FALSE;
            UNLOCK(&client->interface->lock);
        }

        /*
         * We don't need the client; send it to the inactive
         * queue for recycling.
         */
        if (client->mortal) {
            if (client->newstate > NS_CLIENTSTATE_INACTIVE)
                client->newstate = NS_CLIENTSTATE_INACTIVE;
        }

        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);

        /* Still waiting for accept cancel completion. */
        if (! (client->naccepts == 0))
            return (ISC_TRUE);

        /* Accept cancel is complete. */
        if (client->nrecvs > 0)
            isc_socket_cancel(client->udpsocket, client->task,
                      ISC_SOCKCANCEL_RECV);

        /* Still waiting for recv cancel completion. */
        if (! (client->nrecvs == 0))
            return (ISC_TRUE);

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

        /*
         * 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.
         */
        client->state = NS_CLIENTSTATE_INACTIVE;
        INSIST(client->recursionquota == NULL);

        if (client->state == client->newstate) {
            client->newstate = NS_CLIENTSTATE_MAX;
            if (!ns_g_clienttest && manager != NULL &&
                !manager->exiting)
                ISC_QUEUE_PUSH(manager->inactive, client,
                           ilink);
            if (client->needshutdown)
                isc_task_shutdown(client->task);
            return (ISC_TRUE);
        }
    }

    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);
        INSIST(!ISC_QLINK_LINKED(client, ilink));

        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->delaytimer != NULL)
            isc_timer_detach(&client->delaytimer);

        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 (manager != NULL) {
            LOCK(&manager->listlock);
            ISC_LIST_UNLINK(manager->clients, client, link);
            LOCK(&manager->lock);
            if (manager->exiting &&
                ISC_LIST_EMPTY(manager->clients))
                destroy_manager = ISC_TRUE;
            UNLOCK(&manager->lock);
            UNLOCK(&manager->listlock);
        }

        /*
         * 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;

        /*
         * Check that there are no other external references to
         * the memory context.
         */
        if (ns_g_clienttest && isc_mem_references(client->mctx) != 1) {
            isc_mem_stats(client->mctx, stderr);
            INSIST(0);
        }
        isc_mem_putanddetach(&client->mctx, client, sizeof(*client));
    }

    if (destroy_manager && manager != NULL)
        clientmgr_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;
    }

    if (ISC_QLINK_LINKED(client, ilink))
        ISC_QUEUE_UNLINK(client->manager->inactive, client, ilink);

    client->newstate = NS_CLIENTSTATE_FREED;
    client->needshutdown = ISC_FALSE;
    (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 ||
           client->state == NS_CLIENTSTATE_RECURSING);

    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->signer = NULL;
    client->udpsize = 512;
    client->extflags = 0;
    client->ednsversion = -1;
    dns_message_reset(client->message, DNS_MESSAGE_INTENTPARSE);

    if (client->recursionquota != NULL) {
        isc_quota_detach(&client->recursionquota);
        isc_stats_decrement(ns_g_server->nsstats,
                    dns_nsstatscounter_recursclients);
    }

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

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_RECURSING ||
        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;
    }

    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;
#ifdef ISC_PLATFORM_USESIT
        if ((client->attributes & NS_CLIENTATTR_HAVESIT) == 0) {
            if (client->view != NULL)
                bufsize = client->view->situdp;
            else
                bufsize = 512;
        } else
            bufsize = client->udpsize;
        if (bufsize > client->udpsize)
            bufsize = client->udpsize;
        if (bufsize > SEND_BUFFER_SIZE)
            bufsize = SEND_BUFFER_SIZE;
#else
        if (client->udpsize < SEND_BUFFER_SIZE)
            bufsize = client->udpsize;
        else
            bufsize = SEND_BUFFER_SIZE;
#endif
        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;
    isc_dscp_t dispdscp = -1;

    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 &&
        (client->attributes & NS_CLIENTATTR_MULTICAST) == 0)
        pktinfo = &client->pktinfo;
    else
        pktinfo = NULL;

    if (client->dispatch != NULL) {
        dispdscp = dns_dispatch_getdscp(client->dispatch);
        if (dispdscp != -1)
            client->dscp = dispdscp;
    }

    if (client->dscp == -1) {
        client->sendevent->attributes &= ~ISC_SOCKEVENTATTR_DSCP;
        client->sendevent->dscp = 0;
    } else {
        client->sendevent->attributes |= ISC_SOCKEVENTATTR_DSCP;
        client->sendevent->dscp = client->dscp;
    }

    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);
}

static void
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];
    unsigned int render_opts;
    unsigned int preferred_glue;
    isc_boolean_t opt_included = ISC_FALSE;

    REQUIRE(NS_CLIENT_VALID(client));

    CTRACE("send");

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

    if ((client->attributes & NS_CLIENTATTR_WANTDNSSEC) != 0)
        render_opts = 0;
    else
        render_opts = DNS_MESSAGERENDER_OMITDNSSEC;

    preferred_glue = 0;
    if (client->view != NULL) {
        if (client->view->preferred_glue == dns_rdatatype_a)
            preferred_glue = DNS_MESSAGERENDER_PREFER_A;
        else if (client->view->preferred_glue == dns_rdatatype_aaaa)
            preferred_glue = DNS_MESSAGERENDER_PREFER_AAAA;
    }

#ifdef ALLOW_FILTER_AAAA
    /*
     * filter-aaaa-on-v4 yes or break-dnssec option to suppress
     * AAAA records.
     *
     * We already know that request came via IPv4,
     * that we have both AAAA and A records,
     * and that we either have no signatures that the client wants
     * or we are supposed to break DNSSEC.
     *
     * Override preferred glue if necessary.
     */
    if ((client->attributes & NS_CLIENTATTR_FILTER_AAAA) != 0) {
        render_opts |= DNS_MESSAGERENDER_FILTER_AAAA;
        if (preferred_glue == DNS_MESSAGERENDER_PREFER_AAAA)
            preferred_glue = DNS_MESSAGERENDER_PREFER_A;
    }
#endif

    /*
     * Create an OPT for our reply.
     */
    if ((client->attributes & NS_CLIENTATTR_WANTOPT) != 0) {
        result = ns_client_addopt(client, client->message,
                      &client->opt);
        if (result != ISC_R_SUCCESS)
            goto done;
    }

    /*
     * 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;
    if (client->peeraddr_valid && client->view != NULL) {
        isc_netaddr_t netaddr;
        dns_name_t *name = NULL;

        isc_netaddr_fromsockaddr(&netaddr, &client->peeraddr);
        if (client->message->tsigkey != NULL)
            name = &client->message->tsigkey->name;
        if (client->view->nocasecompress == NULL ||
            !allowed(&netaddr, name, NULL, 0, NULL,
                 client->view->nocasecompress))
        {
            dns_compress_setsensitive(&cctx, ISC_TRUE);
        }
    }
    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);
        opt_included = ISC_TRUE;
        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;
    /*
     * Stop after the question if TC was set for rate limiting.
     */
    if ((client->message->flags & DNS_MESSAGEFLAG_TC) != 0)
        goto renderend;
    result = dns_message_rendersection(client->message,
                       DNS_SECTION_ANSWER,
                       DNS_MESSAGERENDER_PARTIAL |
                       render_opts);
    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 |
                       render_opts);
    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,
                       preferred_glue | render_opts);
    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);

    /* update statistics (XXXJT: is it okay to access message->xxxkey?) */
    isc_stats_increment(ns_g_server->nsstats, dns_nsstatscounter_response);
    if (opt_included) {
        isc_stats_increment(ns_g_server->nsstats,
                    dns_nsstatscounter_edns0out);
    }
    if (client->message->tsigkey != NULL) {
        isc_stats_increment(ns_g_server->nsstats,
                    dns_nsstatscounter_tsigout);
    }
    if (client->message->sig0key != NULL) {
        isc_stats_increment(ns_g_server->nsstats,
                    dns_nsstatscounter_sig0out);
    }
    if ((client->message->flags & DNS_MESSAGEFLAG_TC) != 0)
        isc_stats_increment(ns_g_server->nsstats,
                    dns_nsstatscounter_truncatedresp);

    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);
}

/*
 * Completes the sending of a delayed client response.
 */
static void
client_delay(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->delaytimer != NULL);

    UNUSED(task);

    CTRACE("client_delay");

    isc_event_free(&event);
    isc_timer_detach(&client->delaytimer);

    client_send(client);
    ns_client_detach(&client);
}

void
ns_client_send(ns_client_t *client) {

    /*
     * Delay the response by ns_g_delay ms.
     */
    if (ns_g_delay != 0) {
        ns_client_t *dummy = NULL;
        isc_result_t result;
        isc_interval_t interval;

        /*
         * Replace ourselves if we have not already been replaced.
         */
        if (!client->mortal) {
            result = ns_client_replace(client);
            if (result != ISC_R_SUCCESS)
                goto nodelay;
        }

        ns_client_attach(client, &dummy);
        if (ns_g_delay >= 1000)
            isc_interval_set(&interval, ns_g_delay / 1000,
                     (ns_g_delay % 1000) * 1000000);
        else
            isc_interval_set(&interval, 0, ns_g_delay * 1000000);
        result = isc_timer_create(client->manager->timermgr,
                      isc_timertype_once, NULL, &interval,
                      client->task, client_delay,
                      client, &client->delaytimer);
        if (result == ISC_R_SUCCESS)
            return;

        ns_client_detach(&dummy);
    }

 nodelay:
    client_send(client);
}

#if NS_CLIENT_DROPPORT
#define DROPPORT_NO     0
#define DROPPORT_REQUEST    1
#define DROPPORT_RESPONSE   2
/*%
 * ns_client_dropport determines if certain requests / responses
 * should be dropped based on the port number.
 *
 * Returns:
 * \li  0:  Don't drop.
 * \li  1:  Drop request.
 * \li  2:  Drop (error) response.
 */
static int
ns_client_dropport(in_port_t port) {
    switch (port) {
    case 7: /* echo */
    case 13: /* daytime */
    case 19: /* chargen */
    case 37: /* time */
        return (DROPPORT_REQUEST);
    case 464: /* kpasswd */
        return (DROPPORT_RESPONSE);
    }
    return (DROPPORT_NO);
}
#endif

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);

#if NS_CLIENT_DROPPORT
    /*
     * Don't send FORMERR to ports on the drop port list.
     */
    if (rcode == dns_rcode_formerr &&
        ns_client_dropport(isc_sockaddr_getport(&client->peeraddr)) !=
        DROPPORT_NO) {
        char buf[64];
        isc_buffer_t b;

        isc_buffer_init(&b, buf, sizeof(buf) - 1);
        if (dns_rcode_totext(rcode, &b) != ISC_R_SUCCESS)
            isc_buffer_putstr(&b, "UNKNOWN RCODE");
        ns_client_log(client, DNS_LOGCATEGORY_SECURITY,
                  NS_LOGMODULE_CLIENT, ISC_LOG_DEBUG(10),
                  "dropped error (%.*s) response: suspicious port",
                  (int)isc_buffer_usedlength(&b), buf);
        ns_client_next(client, ISC_R_SUCCESS);
        return;
    }
#endif

    /*
     * Try to rate limit error responses.
     */
    if (client->view != NULL && client->view->rrl != NULL) {
        isc_boolean_t wouldlog;
        char log_buf[DNS_RRL_LOG_BUF_LEN];
        dns_rrl_result_t rrl_result;

        INSIST(rcode != dns_rcode_noerror &&
               rcode != dns_rcode_nxdomain);
        wouldlog = isc_log_wouldlog(ns_g_lctx, DNS_RRL_LOG_DROP);
        rrl_result = dns_rrl(client->view, &client->peeraddr,
                     TCP_CLIENT(client),
                     dns_rdataclass_in, dns_rdatatype_none,
                     NULL, result, client->now,
                     wouldlog, log_buf, sizeof(log_buf));
        if (rrl_result != DNS_RRL_RESULT_OK) {
            /*
             * Log dropped errors in the query category
             * so that they are not lost in silence.
             * Starts of rate-limited bursts are logged in
             * NS_LOGCATEGORY_RRL.
             */
            if (wouldlog) {
                ns_client_log(client,
                          NS_LOGCATEGORY_QUERY_EERRORS,
                          NS_LOGMODULE_CLIENT,
                          DNS_RRL_LOG_DROP,
                          "%s", log_buf);
            }
            /*
             * Some error responses cannot be 'slipped',
             * so don't try to slip any error responses.
             */
            if (!client->view->rrl->log_only) {
                isc_stats_increment(ns_g_server->nsstats,
                        dns_nsstatscounter_ratedropped);
                isc_stats_increment(ns_g_server->nsstats,
                        dns_nsstatscounter_dropped);
                ns_client_next(client, DNS_R_DROP);
                return;
            }
        }
    }

    /*
     * 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;

    if (rcode == dns_rcode_formerr) {
        /*
         * 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 (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;
    } else if (rcode == dns_rcode_servfail &&
           client->view != NULL && client->view->fail_ttl != 0 &&
           ((client->attributes & NS_CLIENTATTR_NOSETFC) == 0))
    {
        /*
         * SERVFAIL caching: store qname/qtype of failed queries
         */
        isc_time_t expire;
        isc_interval_t i;
        isc_uint32_t flags = 0;

        if ((message->flags & DNS_MESSAGEFLAG_CD) != 0)
            flags = NS_FAILCACHE_CD;

        isc_interval_set(&i, client->view->fail_ttl, 0);
        result = isc_time_nowplusinterval(&expire, &i);
        if (result == ISC_R_SUCCESS)
            dns_badcache_add(client->view->failcache,
                     client->query.qname,
                     client->query.qtype,
                     ISC_TRUE, flags, &expire);
    }
    ns_client_send(client);
}

isc_result_t
ns_client_addopt(ns_client_t *client, dns_message_t *message,
         dns_rdataset_t **opt)
{
    unsigned char ecs[ECS_SIZE];
    char nsid[BUFSIZ], *nsidp;
#ifdef ISC_PLATFORM_USESIT
    unsigned char sit[SIT_SIZE];
#endif
    isc_result_t result;
    dns_view_t *view;
    dns_resolver_t *resolver;
    isc_uint16_t udpsize;
    dns_ednsopt_t ednsopts[DNS_EDNSOPTIONS];
    int count = 0;
    unsigned int flags;
    unsigned char expire[4];

    REQUIRE(NS_CLIENT_VALID(client));
    REQUIRE(opt != NULL && *opt == NULL);
    REQUIRE(message != NULL);

    view = client->view;
    resolver = (view != NULL) ? view->resolver : NULL;
    if (resolver != NULL)
        udpsize = dns_resolver_getudpsize(resolver);
    else
        udpsize = ns_g_udpsize;

    flags = client->extflags & DNS_MESSAGEEXTFLAG_REPLYPRESERVE;

    /* Set EDNS options if applicable */
    if ((client->attributes & NS_CLIENTATTR_WANTNSID) != 0 &&
        (ns_g_server->server_id != NULL ||
         ns_g_server->server_usehostname)) {
        if (ns_g_server->server_usehostname) {
            isc_result_t result;
            result = ns_os_gethostname(nsid, sizeof(nsid));
            if (result != ISC_R_SUCCESS) {
                goto no_nsid;
            }
            nsidp = nsid;
        } else
            nsidp = ns_g_server->server_id;

        INSIST(count < DNS_EDNSOPTIONS);
        ednsopts[count].code = DNS_OPT_NSID;
        ednsopts[count].length = strlen(nsidp);
        ednsopts[count].value = (unsigned char *)nsidp;
        count++;
    }
 no_nsid:
#ifdef ISC_PLATFORM_USESIT
    if ((client->attributes & NS_CLIENTATTR_WANTSIT) != 0) {
        isc_buffer_t buf;
        isc_stdtime_t now;
        isc_uint32_t nonce;

        isc_buffer_init(&buf, sit, sizeof(sit));
        isc_stdtime_get(&now);
        isc_random_get(&nonce);

        compute_sit(client, now, nonce, &buf);

        INSIST(count < DNS_EDNSOPTIONS);
        ednsopts[count].code = DNS_OPT_SIT;
        ednsopts[count].length = SIT_SIZE;
        ednsopts[count].value = sit;
        count++;
    }
#endif
    if ((client->attributes & NS_CLIENTATTR_HAVEEXPIRE) != 0) {
        isc_buffer_t buf;

        INSIST(count < DNS_EDNSOPTIONS);

        isc_buffer_init(&buf, expire, sizeof(expire));
        isc_buffer_putuint32(&buf, client->expire);
        ednsopts[count].code = DNS_OPT_EXPIRE;
        ednsopts[count].length = 4;
        ednsopts[count].value = expire;
        count++;
    }
    if (((client->attributes & NS_CLIENTATTR_HAVEECS) != 0) &&
        (client->ecs_addr.family == AF_INET ||
         client->ecs_addr.family == AF_INET6))
    {
        int i, addrbytes = (client->ecs_addrlen + 7) / 8;
        isc_uint8_t *paddr;
        isc_buffer_t buf;

        /* Add client subnet option. */
        isc_buffer_init(&buf, ecs, sizeof(ecs));
        if (client->ecs_addr.family == AF_INET)
            isc_buffer_putuint16(&buf, 1);
        else
            isc_buffer_putuint16(&buf, 2);
        isc_buffer_putuint8(&buf, client->ecs_addrlen);
        isc_buffer_putuint8(&buf, client->ecs_scope);

        paddr = (isc_uint8_t *) &client->ecs_addr.type;
        for (i = 0; i < addrbytes; i++) {
            unsigned char uc;
            uc = paddr[i];
            if (i == addrbytes - 1 &&
                ((client->ecs_addrlen % 8) != 0))
                uc &= (1U << (8 - (client->ecs_addrlen % 8)));
            isc_buffer_putuint8(&buf, uc);
        }

        ednsopts[count].code = DNS_OPT_CLIENT_SUBNET;
        ednsopts[count].length = addrbytes + 4;
        ednsopts[count].value = ecs;
        count++;
    }

    result = dns_message_buildopt(message, opt, 0, udpsize, flags,
                      ednsopts, count);
    return (result);
}

static inline isc_boolean_t
allowed(isc_netaddr_t *addr, dns_name_t *signer,
    isc_netaddr_t *ecs_addr, isc_uint8_t ecs_addrlen,
    isc_uint8_t *ecs_scope, dns_acl_t *acl)
{
    int match;
    isc_result_t result;

    if (acl == NULL)
        return (ISC_TRUE);
    result = dns_acl_match2(addr, signer, ecs_addr, ecs_addrlen, ecs_scope,
                acl, &ns_g_server->aclenv, &match, NULL);
    if (result == ISC_R_SUCCESS && match > 0)
        return (ISC_TRUE);
    return (ISC_FALSE);
}

/*
 * Callback to see if a non-recursive query coming from 'srcaddr' to
 * 'destaddr', with optional key 'mykey' for class 'rdclass' would be
 * delivered to 'myview'.
 *
 * We run this unlocked as both the view list and the interface list
 * are updated when the appropriate task has exclusivity.
 */
isc_boolean_t
ns_client_isself(dns_view_t *myview, dns_tsigkey_t *mykey,
         isc_sockaddr_t *srcaddr, isc_sockaddr_t *dstaddr,
         dns_rdataclass_t rdclass, void *arg)
{
    dns_view_t *view;
    dns_tsigkey_t *key = NULL;
    dns_name_t *tsig = NULL;
    isc_netaddr_t netsrc;
    isc_netaddr_t netdst;

    UNUSED(arg);

    /*
     * ns_g_server->interfacemgr is task exclusive locked.
     */
    if (ns_g_server->interfacemgr == NULL)
        return (ISC_TRUE);

    if (!ns_interfacemgr_listeningon(ns_g_server->interfacemgr, dstaddr))
        return (ISC_FALSE);

    isc_netaddr_fromsockaddr(&netsrc, srcaddr);
    isc_netaddr_fromsockaddr(&netdst, dstaddr);

    for (view = ISC_LIST_HEAD(ns_g_server->viewlist);
         view != NULL;
         view = ISC_LIST_NEXT(view, link)) {

        if (view->matchrecursiveonly)
            continue;

        if (rdclass != view->rdclass)
            continue;

        if (mykey != NULL) {
            isc_boolean_t match;
            isc_result_t result;

            result = dns_view_gettsig(view, &mykey->name, &key);
            if (result != ISC_R_SUCCESS)
                continue;
            match = dst_key_compare(mykey->key, key->key);
            dns_tsigkey_detach(&key);
            if (!match)
                continue;
            tsig = dns_tsigkey_identity(mykey);
        }

        if (allowed(&netsrc, tsig, NULL, 0, NULL,
                view->matchclients) &&
            allowed(&netdst, tsig, NULL, 0, NULL,
                view->matchdestinations))
            break;
    }
    return (ISC_TF(view == myview));
}

#ifdef ISC_PLATFORM_USESIT
static void
compute_sit(ns_client_t *client, isc_uint32_t when, isc_uint32_t nonce,
        isc_buffer_t *buf)
{
#ifdef AES_SIT
    unsigned char digest[ISC_AES_BLOCK_LENGTH];
    unsigned char input[4 + 4 + 16];
    isc_netaddr_t netaddr;
    unsigned char *cp;
    unsigned int i;

    memset(input, 0, sizeof(input));
    cp = isc_buffer_used(buf);
    isc_buffer_putmem(buf, client->cookie, 8);
    isc_buffer_putuint32(buf, nonce);
    isc_buffer_putuint32(buf, when);
    memmove(input, cp, 16);
    isc_aes128_crypt(ns_g_server->secret, input, digest);
    for (i = 0; i < 8; i++)
        input[i] = digest[i] ^ digest[i + 8];
    isc_netaddr_fromsockaddr(&netaddr, &client->peeraddr);
    switch (netaddr.family) {
    case AF_INET:
        memmove(input + 8, (unsigned char *)&netaddr.type.in, 4);
        memset(input + 12, 0, 4);
        isc_aes128_crypt(ns_g_server->secret, input, digest);
        break;
    case AF_INET6:
        memmove(input + 8, (unsigned char *)&netaddr.type.in6, 16);
        isc_aes128_crypt(ns_g_server->secret, input, digest);
        for (i = 0; i < 8; i++)
            input[i + 8] = digest[i] ^ digest[i + 8];
        isc_aes128_crypt(ns_g_server->secret, input + 8, digest);
        break;
    }
    for (i = 0; i < 8; i++)
        digest[i] ^= digest[i + 8];
    isc_buffer_putmem(buf, digest, 8);
#endif
#ifdef HMAC_SHA1_SIT
    unsigned char digest[ISC_SHA1_DIGESTLENGTH];
    isc_netaddr_t netaddr;
    unsigned char *cp;
    isc_hmacsha1_t hmacsha1;

    cp = isc_buffer_used(buf);
    isc_buffer_putmem(buf, client->cookie, 8);
    isc_buffer_putuint32(buf, nonce);
    isc_buffer_putuint32(buf, when);

    isc_hmacsha1_init(&hmacsha1,
              ns_g_server->secret,
              ISC_SHA1_DIGESTLENGTH);
    isc_hmacsha1_update(&hmacsha1, cp, 16);
    isc_netaddr_fromsockaddr(&netaddr, &client->peeraddr);
    switch (netaddr.family) {
    case AF_INET:
        isc_hmacsha1_update(&hmacsha1,
                    (unsigned char *)&netaddr.type.in, 4);
        break;
    case AF_INET6:
        isc_hmacsha1_update(&hmacsha1,
                    (unsigned char *)&netaddr.type.in6, 16);
        break;
    }
    isc_hmacsha1_update(&hmacsha1, client->cookie, sizeof(client->cookie));
    isc_hmacsha1_sign(&hmacsha1, digest, sizeof(digest));
    isc_buffer_putmem(buf, digest, 8);
    isc_hmacsha1_invalidate(&hmacsha1);
#endif
#ifdef HMAC_SHA256_SIT
    unsigned char digest[ISC_SHA256_DIGESTLENGTH];
    isc_netaddr_t netaddr;
    unsigned char *cp;
    isc_hmacsha256_t hmacsha256;

    cp = isc_buffer_used(buf);
    isc_buffer_putmem(buf, client->cookie, 8);
    isc_buffer_putuint32(buf, nonce);
    isc_buffer_putuint32(buf, when);

    isc_hmacsha256_init(&hmacsha256,
                ns_g_server->secret,
                ISC_SHA256_DIGESTLENGTH);
    isc_hmacsha256_update(&hmacsha256, cp, 16);
    isc_netaddr_fromsockaddr(&netaddr, &client->peeraddr);
    switch (netaddr.family) {
    case AF_INET:
        isc_hmacsha256_update(&hmacsha256,
                      (unsigned char *)&netaddr.type.in, 4);
        break;
    case AF_INET6:
        isc_hmacsha256_update(&hmacsha256,
                      (unsigned char *)&netaddr.type.in6, 16);
        break;
    }
    isc_hmacsha256_update(&hmacsha256, client->cookie,
                  sizeof(client->cookie));
    isc_hmacsha256_sign(&hmacsha256, digest, sizeof(digest));
    isc_buffer_putmem(buf, digest, 8);
    isc_hmacsha256_invalidate(&hmacsha256);
#endif
}

static void
process_sit(ns_client_t *client, isc_buffer_t *buf, size_t optlen) {
    unsigned char dbuf[SIT_SIZE];
    unsigned char *old;
    isc_stdtime_t now;
    isc_uint32_t when;
    isc_uint32_t nonce;
    isc_buffer_t db;

    client->attributes |= NS_CLIENTATTR_WANTSIT;

    isc_stats_increment(ns_g_server->nsstats,
                dns_nsstatscounter_sitopt);

    if (optlen != SIT_SIZE) {
        /*
         * Not our token.
         */
        if (optlen >= 8U)
            memmove(client->cookie, isc_buffer_current(buf), 8);
        else
            memset(client->cookie, 0, 8);
        isc_buffer_forward(buf, (unsigned int)optlen);

        if (optlen == 8U)
            isc_stats_increment(ns_g_server->nsstats,
                        dns_nsstatscounter_sitnew);
        else
            isc_stats_increment(ns_g_server->nsstats,
                        dns_nsstatscounter_sitbadsize);
        return;
    }

    /*
     * Process all of the incoming buffer.
     */
    old = isc_buffer_current(buf);
    memmove(client->cookie, old, 8);
    isc_buffer_forward(buf, 8);
    nonce = isc_buffer_getuint32(buf);
    when = isc_buffer_getuint32(buf);
    isc_buffer_forward(buf, 8);

    /*
     * Allow for a 5 minute clock skew between servers sharing a secret.
     * Only accept SIT if we have talked to the client in the last hour.
     */
    isc_stdtime_get(&now);
    if (isc_serial_gt(when, (now + 300)) ||     /* In the future. */
        isc_serial_lt(when, (now - 3600))) {    /* In the past. */
        isc_stats_increment(ns_g_server->nsstats,
                    dns_nsstatscounter_sitbadtime);
        return;
    }

    isc_buffer_init(&db, dbuf, sizeof(dbuf));
    compute_sit(client, when, nonce, &db);

    if (memcmp(old, dbuf, SIT_SIZE) != 0) {
        isc_stats_increment(ns_g_server->nsstats,
                    dns_nsstatscounter_sitnomatch);
        return;
    }
    isc_stats_increment(ns_g_server->nsstats,
                dns_nsstatscounter_sitmatch);

    client->attributes |= NS_CLIENTATTR_HAVESIT;
}
#endif

static isc_result_t
process_ecs(ns_client_t *client, isc_buffer_t *buf, size_t optlen) {
    isc_uint16_t family;
    isc_uint8_t addrlen, addrbytes, scope, *paddr;
    isc_netaddr_t caddr;
    int i;

    if (optlen < 4U) {
        ns_client_log(client, NS_LOGCATEGORY_CLIENT,
                  NS_LOGMODULE_CLIENT, ISC_LOG_DEBUG(2),
                  "EDNS client subnet option too short");
        return (DNS_R_FORMERR);
    }

    family = isc_buffer_getuint16(buf);
    addrlen = isc_buffer_getuint8(buf);
    scope = isc_buffer_getuint8(buf);
    optlen -= 4;

    if (scope != 0U) {
        ns_client_log(client, NS_LOGCATEGORY_CLIENT,
                  NS_LOGMODULE_CLIENT, ISC_LOG_DEBUG(2),
                  "EDNS client subnet option: invalid scope");
        return (DNS_R_FORMERR);
    }

    memset(&caddr, 0, sizeof(caddr));
    switch (family) {
    case 1:
        if (addrlen > 32U)
            goto invalid_length;
        caddr.family = AF_INET;
        break;
    case 2:
        if (addrlen > 128U) {
    invalid_length:
            ns_client_log(client, NS_LOGCATEGORY_CLIENT,
                      NS_LOGMODULE_CLIENT, ISC_LOG_DEBUG(2),
                      "EDNS client subnet option: invalid "
                      "address length (%u) for %s",
                      addrlen, family == 1 ? "IPv4" : "IPv6");
            return (DNS_R_FORMERR);
        }
        caddr.family = AF_INET6;
        break;
    default:
        ns_client_log(client, NS_LOGCATEGORY_CLIENT,
                  NS_LOGMODULE_CLIENT, ISC_LOG_DEBUG(2),
                  "EDNS client subnet option: invalid family");
        return (DNS_R_FORMERR);
    }

    addrbytes = (addrlen + 7) / 8;
    if (isc_buffer_remaininglength(buf) < addrbytes) {
        ns_client_log(client, NS_LOGCATEGORY_CLIENT,
                  NS_LOGMODULE_CLIENT, ISC_LOG_DEBUG(2),
                  "EDNS client subnet option: address too short");
        return (DNS_R_FORMERR);
    }

    paddr = (isc_uint8_t *) &caddr.type;
    for (i = 0; i < addrbytes; i++) {
        paddr[i] = isc_buffer_getuint8(buf);
        optlen--;
    }

    memmove(&client->ecs_addr, &caddr, sizeof(caddr));
    client->ecs_addrlen = addrlen;
    client->ecs_scope = 0;
    client->attributes |= NS_CLIENTATTR_HAVEECS;

    isc_buffer_forward(buf, optlen);
    return (ISC_R_SUCCESS);
}

static isc_result_t
process_opt(ns_client_t *client, dns_rdataset_t *opt) {
    dns_rdata_t rdata;
    isc_buffer_t optbuf;
    isc_result_t result;
    isc_uint16_t optcode;
    isc_uint16_t optlen;

    /*
     * 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);

    /*
     * Do we understand this version of EDNS?
     *
     * XXXRTH need library support for this!
     */
    client->ednsversion = (opt->ttl & 0x00FF0000) >> 16;
    if (client->ednsversion > DNS_EDNS_VERSION) {
        isc_stats_increment(ns_g_server->nsstats,
                    dns_nsstatscounter_badednsver);
        result = ns_client_addopt(client, client->message,
                      &client->opt);
        if (result == ISC_R_SUCCESS)
            result = DNS_R_BADVERS;
        ns_client_error(client, result);
        goto cleanup;
    }

    /* Check for NSID request */
    result = dns_rdataset_first(opt);
    if (result == ISC_R_SUCCESS) {
        dns_rdata_init(&rdata);
        dns_rdataset_current(opt, &rdata);
        isc_buffer_init(&optbuf, rdata.data, rdata.length);
        isc_buffer_add(&optbuf, rdata.length);
        while (isc_buffer_remaininglength(&optbuf) >= 4) {
            optcode = isc_buffer_getuint16(&optbuf);
            optlen = isc_buffer_getuint16(&optbuf);
            switch (optcode) {
            case DNS_OPT_NSID:
                isc_stats_increment(ns_g_server->nsstats,
                            dns_nsstatscounter_nsidopt);
                client->attributes |= NS_CLIENTATTR_WANTNSID;
                isc_buffer_forward(&optbuf, optlen);
                break;
#ifdef ISC_PLATFORM_USESIT
            case DNS_OPT_SIT:
                process_sit(client, &optbuf, optlen);
                break;
#endif
            case DNS_OPT_EXPIRE:
                isc_stats_increment(ns_g_server->nsstats,
                          dns_nsstatscounter_expireopt);
                client->attributes |= NS_CLIENTATTR_WANTEXPIRE;
                isc_buffer_forward(&optbuf, optlen);
                break;
            case DNS_OPT_CLIENT_SUBNET:
                result = process_ecs(client, &optbuf, optlen);
                if (result != ISC_R_SUCCESS) {
                    ns_client_error(client, result);
                    goto cleanup;
                }
                isc_stats_increment(ns_g_server->nsstats,
                          dns_nsstatscounter_ecsopt);
                break;
            default:
                isc_stats_increment(ns_g_server->nsstats,
                          dns_nsstatscounter_otheropt);
                isc_buffer_forward(&optbuf, optlen);
                break;
            }
        }
    }

    isc_stats_increment(ns_g_server->nsstats, dns_nsstatscounter_edns0in);
    client->attributes |= NS_CLIENTATTR_WANTOPT;

 cleanup:
    return (result);
}

/*
 * 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_R_SUCCESS;
    isc_buffer_t *buffer;
    isc_buffer_t tbuffer;
    dns_view_t *view;
    dns_rdataset_t *opt;
    dns_name_t *signame;
    isc_boolean_t ra;   /* Recursion available. */
    isc_netaddr_t netaddr;
    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);

    INSIST(client->recursionquota == NULL);

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

    ns_client_requests++;

    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_DSCP) != 0) {
            ns_client_log(client, NS_LOGCATEGORY_CLIENT,
                  NS_LOGMODULE_CLIENT, ISC_LOG_DEBUG(90),
                  "received DSCP %d", sevent->dscp);
            if (client->dscp == -1)
                client->dscp = sevent->dscp;
        }
        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_task_getcurrenttime(task, &client->requesttime);
    client->now = client->requesttime;
    isc_time_set(&client->tnow, client->now, 0);

    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);

#if NS_CLIENT_DROPPORT
    if (ns_client_dropport(isc_sockaddr_getport(&client->peeraddr)) ==
        DROPPORT_REQUEST) {
        ns_client_log(client, DNS_LOGCATEGORY_SECURITY,
                  NS_LOGMODULE_CLIENT, ISC_LOG_DEBUG(10),
                  "dropped request: suspicious port");
        ns_client_next(client, ISC_R_SUCCESS);
        goto cleanup;
    }
#endif

    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;
        }
    }

    /*
     * Silently drop multicast requests for the present.
     * XXXMPA revisit this as mDNS spec was published.
     */
    if ((client->attributes & NS_CLIENTATTR_MULTICAST) != 0) {
        ns_client_log(client, NS_LOGCATEGORY_CLIENT,
                  NS_LOGMODULE_CLIENT, ISC_LOG_DEBUG(2),
                  "dropping multicast request");
        ns_client_next(client, DNS_R_REFUSED);
        goto cleanup;
    }

    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;
        }
    }

    /*
     * Update some statistics counters.  Don't count responses.
     */
    if (isc_sockaddr_pf(&client->peeraddr) == PF_INET) {
        isc_stats_increment(ns_g_server->nsstats,
                    dns_nsstatscounter_requestv4);
    } else {
        isc_stats_increment(ns_g_server->nsstats,
                    dns_nsstatscounter_requestv6);
    }
    if (TCP_CLIENT(client))
        isc_stats_increment(ns_g_server->nsstats,
                    dns_nsstatscounter_requesttcp);

    /*
     * 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;
    }

    dns_opcodestats_increment(ns_g_server->opcodestats,
                  client->message->opcode);
    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;

    /* RFC1123 section 6.1.3.2 */
    if ((client->attributes & NS_CLIENTATTR_MULTICAST) != 0)
        client->message->flags &= ~DNS_MESSAGEFLAG_RD;

    /*
     * Deal with EDNS.
     */
    if (ns_g_noedns)
        opt = NULL;
    else
        opt = dns_message_getopt(client->message);

    client->ecs_addrlen = 0;
    client->ecs_scope = 0;

    if (opt != NULL) {
        /*
         * Are we dropping all EDNS queries?
         */
        if (ns_g_dropedns) {
            ns_client_next(client, ISC_R_SUCCESS);
            goto cleanup;
        }
        result = process_opt(client, opt);
        if (result != ISC_R_SUCCESS)
            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.  If the receiving interface is
     * bound to a specific address, we simply use it regardless of the
     * address family.  All IPv4 queries should fall into this case.
     * Otherwise, if this is a TCP query, get the address from the
     * receiving socket (this needs a system call and can be heavy).
     * For IPv6 UDP queries, we get this from the pktinfo structure (if
     * supported).
     * If all the attempts fail (this can happen due to memory shortage,
     * etc), we regard this as an error for safety.
     */
    if ((client->interface->flags & NS_INTERFACEFLAG_ANYADDR) == 0)
        isc_netaddr_fromsockaddr(&client->destaddr,
                     &client->interface->addr);
    else {
        isc_sockaddr_t sockaddr;
        result = ISC_R_FAILURE;

        if (TCP_CLIENT(client))
            result = isc_socket_getsockname(client->tcpsocket,
                            &sockaddr);
        if (result == ISC_R_SUCCESS)
            isc_netaddr_fromsockaddr(&client->destaddr, &sockaddr);
        if (result != ISC_R_SUCCESS &&
            client->interface->addr.type.sa.sa_family == AF_INET6 &&
            (client->attributes & NS_CLIENTATTR_PKTINFO) != 0) {
            /*
             * XXXJT technically, we should convert the receiving
             * interface ID to a proper scope zone ID.  However,
             * due to the fact there is no standard API for this,
             * we only handle link-local addresses and use the
             * interface index as link ID.  Despite the assumption,
             * it should cover most typical cases.
             */
            isc_netaddr_fromin6(&client->destaddr,
                        &client->pktinfo.ipi6_addr);
            if (IN6_IS_ADDR_LINKLOCAL(&client->pktinfo.ipi6_addr))
                isc_netaddr_setzone(&client->destaddr,
                        client->pktinfo.ipi6_ifindex);
            result = ISC_R_SUCCESS;
        }
        if (result != ISC_R_SUCCESS) {
            UNEXPECTED_ERROR(__FILE__, __LINE__,
                     "failed to get request's "
                     "destination: %s",
                     isc_result_totext(result));
            ns_client_next(client, ISC_R_SUCCESS);
            goto cleanup;
        }
    }

    /*
     * 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)
        {
            dns_name_t *tsig = NULL;
            isc_netaddr_t *addr = NULL;
            isc_uint8_t *scope = NULL;

            sigresult = dns_message_rechecksig(client->message,
                               view);
            if (sigresult == ISC_R_SUCCESS) {
                dns_tsigkey_t *tsigkey;

                tsigkey = client->message->tsigkey;
                tsig = dns_tsigkey_identity(tsigkey);
            }

            if ((client->attributes & NS_CLIENTATTR_HAVEECS) != 0) {
                addr = &client->ecs_addr;
                scope = &client->ecs_scope;
            }

            if (allowed(&netaddr, tsig, addr, client->ecs_addrlen,
                    scope, view->matchclients) &&
                allowed(&client->destaddr, tsig, NULL,
                    0, NULL, view->matchdestinations) &&
                !(view->matchrecursiveonly &&
                (client->message->flags & DNS_MESSAGEFLAG_RD) == 0))
            {
                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;

        dns_message_resetsig(client->message);

        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.
     */
    client->signer = NULL;
    dns_name_init(&client->signername, NULL);
    result = dns_message_signer(client->message, &client->signername);
    if (result != ISC_R_NOTFOUND) {
        signame = NULL;
        if (dns_message_gettsig(client->message, &signame) != NULL) {
            isc_stats_increment(ns_g_server->nsstats,
                        dns_nsstatscounter_tsigin);
        } else {
            isc_stats_increment(ns_g_server->nsstats,
                        dns_nsstatscounter_sig0in);
        }

    }
    if (result == ISC_R_SUCCESS) {
        char namebuf[DNS_NAME_FORMATSIZE];
        dns_name_format(&client->signername, namebuf, sizeof(namebuf));
        ns_client_log(client, DNS_LOGCATEGORY_SECURITY,
                  NS_LOGMODULE_CLIENT, ISC_LOG_DEBUG(3),
                  "request has valid signature: %s", namebuf);
        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 {
        char tsigrcode[64];
        isc_buffer_t b;
        dns_rcode_t status;
        isc_result_t tresult;

        /* There is a signature, but it is bad. */
        isc_stats_increment(ns_g_server->nsstats,
                    dns_nsstatscounter_invalidsig);
        signame = NULL;
        if (dns_message_gettsig(client->message, &signame) != NULL) {
            char namebuf[DNS_NAME_FORMATSIZE];
            char cnamebuf[DNS_NAME_FORMATSIZE];
            dns_name_format(signame, namebuf, sizeof(namebuf));
            status = client->message->tsigstatus;
            isc_buffer_init(&b, tsigrcode, sizeof(tsigrcode) - 1);
            tresult = dns_tsigrcode_totext(status, &b);
            INSIST(tresult == ISC_R_SUCCESS);
            tsigrcode[isc_buffer_usedlength(&b)] = '\0';
            if (client->message->tsigkey->generated) {
                dns_name_format(client->message->tsigkey->creator,
                        cnamebuf, sizeof(cnamebuf));
                ns_client_log(client, DNS_LOGCATEGORY_SECURITY,
                          NS_LOGMODULE_CLIENT,
                          ISC_LOG_ERROR,
                          "request has invalid signature: "
                          "TSIG %s (%s): %s (%s)", namebuf,
                          cnamebuf,
                          isc_result_totext(result),
                          tsigrcode);
            } else {
                ns_client_log(client, DNS_LOGCATEGORY_SECURITY,
                          NS_LOGMODULE_CLIENT,
                          ISC_LOG_ERROR,
                          "request has invalid signature: "
                          "TSIG %s: %s (%s)", namebuf,
                          isc_result_totext(result),
                          tsigrcode);
            }
        } else {
            status = client->message->sig0status;
            isc_buffer_init(&b, tsigrcode, sizeof(tsigrcode) - 1);
            tresult = dns_tsigrcode_totext(status, &b);
            INSIST(tresult == ISC_R_SUCCESS);
            tsigrcode[isc_buffer_usedlength(&b)] = '\0';
            ns_client_log(client, DNS_LOGCATEGORY_SECURITY,
                      NS_LOGMODULE_CLIENT, ISC_LOG_ERROR,
                      "request has invalid signature: %s (%s)",
                      isc_result_totext(result), tsigrcode);
        }
        /*
         * 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.  Note if you can't query the
     * cache there is no point in setting RA.
     */
    ra = ISC_FALSE;
    if (client->view->resolver != NULL &&
        client->view->recursion == ISC_TRUE &&
        ns_client_checkaclsilent(client, NULL,
                     client->view->recursionacl,
                     ISC_TRUE) == ISC_R_SUCCESS &&
        ns_client_checkaclsilent(client, NULL,
                     client->view->cacheacl,
                     ISC_TRUE) == ISC_R_SUCCESS &&
        ns_client_checkaclsilent(client, &client->destaddr,
                     client->view->recursiononacl,
                     ISC_TRUE) == ISC_R_SUCCESS &&
        ns_client_checkaclsilent(client, &client->destaddr,
                     client->view->cacheonacl,
                     ISC_TRUE) == ISC_R_SUCCESS)
        ra = ISC_TRUE;

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

    ns_client_log(client, DNS_LOGCATEGORY_SECURITY, NS_LOGMODULE_CLIENT,
              ISC_LOG_DEBUG(3), ra ? "recursion available" :
                         "recursion not available");

    /*
     * Adjust maximum UDP response size for this client.
     */
    if (client->udpsize > 512) {
        dns_peer_t *peer = NULL;
        isc_uint16_t udpsize = view->maxudp;
        (void) dns_peerlist_peerbyaddr(view->peers, &netaddr, &peer);
        if (peer != NULL)
            dns_peer_getmaxudp(peer, &udpsize);
        if (client->udpsize > udpsize)
            client->udpsize = udpsize;
    }

    /*
     * 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
get_clientmctx(ns_clientmgr_t *manager, isc_mem_t **mctxp) {
    isc_mem_t *clientmctx;
    isc_result_t result;
#if NMCTXS > 0
    unsigned int nextmctx;
#endif

    MTRACE("clientmctx");

    /*
     * Caller must be holding the manager lock.
     */
    if (ns_g_clienttest) {
        result = isc_mem_create(0, 0, mctxp);
        if (result == ISC_R_SUCCESS)
            isc_mem_setname(*mctxp, "client", NULL);
        return (result);
    }
#if NMCTXS > 0
    nextmctx = manager->nextmctx++;
    if (manager->nextmctx == NMCTXS)
        manager->nextmctx = 0;

    INSIST(nextmctx < NMCTXS);

    clientmctx = manager->mctxpool[nextmctx];
    if (clientmctx == NULL) {
        result = isc_mem_create(0, 0, &clientmctx);
        if (result != ISC_R_SUCCESS)
            return (result);
        isc_mem_setname(clientmctx, "client", NULL);

        manager->mctxpool[nextmctx] = clientmctx;
    }
#else
    clientmctx = manager->mctx;
#endif

    isc_mem_attach(clientmctx, mctxp);

    return (ISC_R_SUCCESS);
}

static isc_result_t
client_create(ns_clientmgr_t *manager, ns_client_t **clientp) {
    ns_client_t *client;
    isc_result_t result;
    isc_mem_t *mctx = NULL;

    /*
     * 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);

    result = get_clientmctx(manager, &mctx);
    if (result != ISC_R_SUCCESS)
        return (result);

    client = isc_mem_get(mctx, sizeof(*client));
    if (client == NULL) {
        isc_mem_detach(&mctx);
        return (ISC_R_NOMEMORY);
    }
    client->mctx = mctx;

    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->delaytimer = NULL;

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

    /* XXXRTH  Hardwired constants */

    client->sendevent = isc_socket_socketevent(client->mctx, client,
                           ISC_SOCKEVENT_SENDDONE,
                           client_senddone, client);
    if (client->sendevent == NULL) {
        result = ISC_R_NOMEMORY;
        goto cleanup_message;
    }

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

    client->recvevent = isc_socket_socketevent(client->mctx, client,
                           ISC_SOCKEVENT_RECVDONE,
                           client_request, client);
    if (client->recvevent == NULL) {
        result = ISC_R_NOMEMORY;
        goto cleanup_recvbuf;
    }

    client->magic = NS_CLIENT_MAGIC;
    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->dscp = -1;
    client->extflags = 0;
    client->ednsversion = -1;
    client->next = NULL;
    client->shutdown = NULL;
    client->shutdown_arg = NULL;
    client->signer = 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;
    client->ecs_addrlen = 0;
    client->ecs_scope = 0;
#ifdef ALLOW_FILTER_AAAA
    client->filter_aaaa = dns_aaaa_ok;
#endif
    client->needshutdown = ns_g_clienttest;

    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);
    ISC_LINK_INIT(client, rlink);
    ISC_QLINK_INIT(client, ilink);

    /*
     * 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(client->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_putanddetach(&client->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;
        isc_socket_setname(client->tcpsocket, "client-tcp", NULL);
        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 legitimate 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_recv2() failed: %s",
                 isc_result_totext(result));
        /*
         * This cannot happen in the current implementation, since
         * isc_socket_recv2() cannot fail if flags == 0.
         *
         * 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");

    REQUIRE(client != NULL);
    REQUIRE(client->manager != NULL);

    result = get_client(client->manager, client->interface,
                client->dispatch, TCP_CLIENT(client));
    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) {
#if NMCTXS > 0
    int i;
#endif

    REQUIRE(ISC_LIST_EMPTY(manager->clients));

    MTRACE("clientmgr_destroy");

#if NMCTXS > 0
    for (i = 0; i < NMCTXS; i++) {
        if (manager->mctxpool[i] != NULL)
            isc_mem_detach(&manager->mctxpool[i]);
    }
#endif

    ISC_QUEUE_DESTROY(manager->inactive);
    DESTROYLOCK(&manager->lock);
    DESTROYLOCK(&manager->listlock);
    DESTROYLOCK(&manager->reclock);
    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;
#if NMCTXS > 0
    int i;
#endif

    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;

    result = isc_mutex_init(&manager->listlock);
    if (result != ISC_R_SUCCESS)
        goto cleanup_lock;

    result = isc_mutex_init(&manager->reclock);
    if (result != ISC_R_SUCCESS)
        goto cleanup_listlock;

    manager->mctx = mctx;
    manager->taskmgr = taskmgr;
    manager->timermgr = timermgr;
    manager->exiting = ISC_FALSE;
    ISC_LIST_INIT(manager->clients);
    ISC_LIST_INIT(manager->recursing);
    ISC_QUEUE_INIT(manager->inactive, ilink);
#if NMCTXS > 0
    manager->nextmctx = 0;
    for (i = 0; i < NMCTXS; i++)
        manager->mctxpool[i] = NULL; /* will be created on-demand */
#endif
    manager->magic = MANAGER_MAGIC;

    MTRACE("create");

    *managerp = manager;

    return (ISC_R_SUCCESS);

 cleanup_listlock:
    (void) isc_mutex_destroy(&manager->listlock);

 cleanup_lock:
    (void) isc_mutex_destroy(&manager->lock);

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

    return (result);
}

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

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

    MTRACE("destroy");

    /*
     * Check for success because we may already be task-exclusive
     * at this point.  Only if we succeed at obtaining an exclusive
     * lock now will we need to relinquish it later.
     */
    result = isc_task_beginexclusive(ns_g_server->task);
    if (result == ISC_R_SUCCESS)
        unlock = ISC_TRUE;

    manager->exiting = ISC_TRUE;

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

    if (ISC_LIST_EMPTY(manager->clients))
        need_destroy = ISC_TRUE;

    if (unlock)
        isc_task_endexclusive(ns_g_server->task);

    if (need_destroy)
        clientmgr_destroy(manager);

    *managerp = NULL;
}

static isc_result_t
get_client(ns_clientmgr_t *manager, ns_interface_t *ifp,
       dns_dispatch_t *disp, isc_boolean_t tcp)
{
    isc_result_t result = ISC_R_SUCCESS;
    isc_event_t *ev;
    ns_client_t *client;
    MTRACE("get client");

    REQUIRE(manager != NULL);

    if (manager->exiting)
        return (ISC_R_SHUTTINGDOWN);

    /*
     * Allocate a client.  First try to get a recycled one;
     * if that fails, make a new one.
     */
    client = NULL;
    if (!ns_g_clienttest)
        ISC_QUEUE_POP(manager->inactive, ilink, client);

    if (client != NULL)
        MTRACE("recycle");
    else {
        MTRACE("create new");

        LOCK(&manager->lock);
        result = client_create(manager, &client);
        UNLOCK(&manager->lock);
        if (result != ISC_R_SUCCESS)
            return (result);

        LOCK(&manager->listlock);
        ISC_LIST_APPEND(manager->clients, client, link);
        UNLOCK(&manager->listlock);
    }

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

    client->dscp = ifp->dscp;

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

        dns_dispatch_attach(disp, &client->dispatch);
        sock = dns_dispatch_getsocket(client->dispatch);
        isc_socket_attach(sock, &client->udpsocket);
    }

    INSIST(client->nctls == 0);
    client->nctls++;
    ev = &client->ctlevent;
    isc_task_send(client->task, &ev);

    return (ISC_R_SUCCESS);
}

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 disp;

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

    MTRACE("createclients");

    for (disp = 0; disp < n; disp++) {
        result = get_client(manager, ifp, ifp->udpdispatch[disp], tcp);
        if (result != ISC_R_SUCCESS)
            break;
    }

    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, isc_netaddr_t *netaddr,
             dns_acl_t *acl, isc_boolean_t default_allow)
{
    isc_result_t result;
    isc_netaddr_t tmpnetaddr;
    isc_netaddr_t *ecs_addr = NULL;
    isc_uint8_t ecs_addrlen = 0;
    int match;

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

    if (netaddr == NULL) {
        isc_netaddr_fromsockaddr(&tmpnetaddr, &client->peeraddr);
        netaddr = &tmpnetaddr;
    }

    if ((client->attributes & NS_CLIENTATTR_HAVEECS) != 0) {
        ecs_addr = &client->ecs_addr;
        ecs_addrlen = client->ecs_addrlen;
    }

    result = dns_acl_match2(netaddr, client->signer,
                ecs_addr, ecs_addrlen, NULL, 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, isc_sockaddr_t *sockaddr,
           const char *opname, dns_acl_t *acl,
           isc_boolean_t default_allow, int log_level)
{
    isc_result_t result;
    isc_netaddr_t netaddr;

    if (sockaddr != NULL)
        isc_netaddr_fromsockaddr(&netaddr, sockaddr);

    result = ns_client_checkaclsilent(client, sockaddr ? &netaddr : NULL,
                      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,
                    (unsigned int)len);
    else
        snprintf(peerbuf, len, "@%p", client);
}

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[4096];
    char peerbuf[ISC_SOCKADDR_FORMATSIZE];
    char signerbuf[DNS_NAME_FORMATSIZE], qnamebuf[DNS_NAME_FORMATSIZE];
    const char *viewname = "";
    const char *sep1 = "", *sep2 = "", *sep3 = "", *sep4 = "";
    const char *signer = "", *qname = "";
    dns_name_t *q = NULL;

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

    ns_client_name(client, peerbuf, sizeof(peerbuf));

    if (client->signer != NULL) {
        dns_name_format(client->signer, signerbuf, sizeof(signerbuf));
        sep1 = "/key ";
        signer = signerbuf;
    }

    q = client->query.origqname != NULL
        ? client->query.origqname : client->query.qname;
    if (q != NULL) {
        dns_name_format(q, qnamebuf, sizeof(qnamebuf));
        sep2 = " (";
        sep3 = ")";
        qname = qnamebuf;
    }

    if (client->view != NULL && strcmp(client->view->name, "_bind") != 0 &&
        strcmp(client->view->name, "_default") != 0) {
        sep4 = ": view ";
        viewname = client->view->name;
    }

    isc_log_write(ns_g_lctx, category, module, level,
              "client %s%s%s%s%s%s%s%s: %s",
              peerbuf, sep1, signer, sep2, qname, sep3,
              sep4, viewname, 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_rdatatype_t type,
         dns_rdataclass_t rdclass, char *buf, size_t len)
{
    char namebuf[DNS_NAME_FORMATSIZE];
    char typebuf[DNS_RDATATYPE_FORMATSIZE];
    char classbuf[DNS_RDATACLASS_FORMATSIZE];

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

    if (!isc_log_wouldlog(ns_g_lctx, ISC_LOG_DEBUG(1)))
        return;

    /*
     * 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);
}

void
ns_client_dumprecursing(FILE *f, ns_clientmgr_t *manager) {
    ns_client_t *client;
    char namebuf[DNS_NAME_FORMATSIZE];
    char original[DNS_NAME_FORMATSIZE];
    char peerbuf[ISC_SOCKADDR_FORMATSIZE];
    char typebuf[DNS_RDATATYPE_FORMATSIZE];
    char classbuf[DNS_RDATACLASS_FORMATSIZE];
    const char *name;
    const char *sep;
    const char *origfor;
    dns_rdataset_t *rdataset;

    REQUIRE(VALID_MANAGER(manager));

    LOCK(&manager->reclock);
    client = ISC_LIST_HEAD(manager->recursing);
    while (client != NULL) {
        INSIST(client->state == NS_CLIENTSTATE_RECURSING);

        ns_client_name(client, peerbuf, sizeof(peerbuf));
        if (client->view != NULL &&
            strcmp(client->view->name, "_bind") != 0 &&
            strcmp(client->view->name, "_default") != 0) {
            name = client->view->name;
            sep = ": view ";
        } else {
            name = "";
            sep = "";
        }

        LOCK(&client->query.fetchlock);
        INSIST(client->query.qname != NULL);
        dns_name_format(client->query.qname, namebuf, sizeof(namebuf));
        if (client->query.qname != client->query.origqname &&
            client->query.origqname != NULL) {
            origfor = " for ";
            dns_name_format(client->query.origqname, original,
                    sizeof(original));
        } else {
            origfor = "";
            original[0] = '\0';
        }
        rdataset = ISC_LIST_HEAD(client->query.qname->list);
        if (rdataset == NULL && client->query.origqname != NULL)
            rdataset = ISC_LIST_HEAD(client->query.origqname->list);
        if (rdataset != NULL) {
            dns_rdatatype_format(rdataset->type, typebuf,
                         sizeof(typebuf));
            dns_rdataclass_format(rdataset->rdclass, classbuf,
                          sizeof(classbuf));
        } else {
            strcpy(typebuf, "-");
            strcpy(classbuf, "-");
        }
        UNLOCK(&client->query.fetchlock);
        fprintf(f, "; client %s%s%s: id %u '%s/%s/%s'%s%s "
            "requesttime %d\n", peerbuf, sep, name,
            client->message->id, namebuf, typebuf, classbuf,
            origfor, original, client->requesttime);
        client = ISC_LIST_NEXT(client, rlink);
    }
    UNLOCK(&manager->reclock);
}

void
ns_client_qnamereplace(ns_client_t *client, dns_name_t *name) {
    LOCK(&client->query.fetchlock);
    if (client->query.restarts > 0) {
        /*
         * client->query.qname was dynamically allocated.
         */
        dns_message_puttempname(client->message,
                    &client->query.qname);
    }
    client->query.qname = name;
    UNLOCK(&client->query.fetchlock);
}

isc_result_t
ns_client_sourceip(dns_clientinfo_t *ci, isc_sockaddr_t **addrp) {
    ns_client_t *client = (ns_client_t *) ci->data;

    REQUIRE(NS_CLIENT_VALID(client));
    REQUIRE(addrp != NULL);

    *addrp = &client->peeraddr;
    return (ISC_R_SUCCESS);
}