xnu-6153.11.26.tar.gz

[apple/xnu.git] / bsd / nfs / nfs_lock.c

/*
 * Copyright (c) 2002-2016 Apple Inc. All rights reserved.
 *
 * @APPLE_OSREFERENCE_LICENSE_HEADER_START@
 *
 * This file contains Original Code and/or Modifications of Original Code
 * as defined in and that are subject to the Apple Public Source License
 * Version 2.0 (the 'License'). You may not use this file except in
 * compliance with the License. The rights granted to you under the License
 * may not be used to create, or enable the creation or redistribution of,
 * unlawful or unlicensed copies of an Apple operating system, or to
 * circumvent, violate, or enable the circumvention or violation of, any
 * terms of an Apple operating system software license agreement.
 *
 * Please obtain a copy of the License at
 * http://www.opensource.apple.com/apsl/ and read it before using this file.
 *
 * The Original Code and all software distributed under the License are
 * distributed on an 'AS IS' basis, WITHOUT WARRANTY OF ANY KIND, EITHER
 * EXPRESS OR IMPLIED, AND APPLE HEREBY DISCLAIMS ALL SUCH WARRANTIES,
 * INCLUDING WITHOUT LIMITATION, ANY WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE, QUIET ENJOYMENT OR NON-INFRINGEMENT.
 * Please see the License for the specific language governing rights and
 * limitations under the License.
 *
 * @APPLE_OSREFERENCE_LICENSE_HEADER_END@
 */
/*-
 * Copyright (c) 1997 Berkeley Software Design, Inc. All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 * 3. Berkeley Software Design Inc's name may not be used to endorse or
 *    promote products derived from this software without specific prior
 *    written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY BERKELEY SOFTWARE DESIGN INC ``AS IS'' AND
 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED.  IN NO EVENT SHALL BERKELEY SOFTWARE DESIGN INC BE LIABLE
 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 *
 *      from BSDI nfs_lock.c,v 2.4 1998/12/14 23:49:56 jch Exp
 */

#include <sys/cdefs.h>
#include <sys/param.h>
#include <sys/systm.h>
#include <sys/fcntl.h>
#include <sys/kernel.h>         /* for hz */
#include <sys/file_internal.h>
#include <sys/malloc.h>
#include <sys/lockf.h>          /* for hz */ /* Must come after sys/malloc.h */
#include <sys/kpi_mbuf.h>
#include <sys/mount_internal.h>
#include <sys/proc_internal.h>  /* for p_start */
#include <sys/kauth.h>
#include <sys/resourcevar.h>
#include <sys/socket.h>
#include <sys/unistd.h>
#include <sys/user.h>
#include <sys/vnode_internal.h>

#include <kern/thread.h>
#include <kern/host.h>

#include <machine/limits.h>

#include <net/if.h>

#include <nfs/rpcv2.h>
#include <nfs/nfsproto.h>
#include <nfs/nfs.h>
#include <nfs/nfs_gss.h>
#include <nfs/nfsmount.h>
#include <nfs/nfsnode.h>
#include <nfs/nfs_lock.h>

#include <mach/host_priv.h>
#include <mach/mig_errors.h>
#include <mach/host_special_ports.h>
#include <lockd/lockd_mach.h>

extern void ipc_port_release_send(ipc_port_t);

/*
 * pending lock request messages are kept in this queue which is
 * kept sorted by transaction ID (xid).
 */
static uint64_t nfs_lockxid = 0;
static LOCKD_MSG_QUEUE nfs_pendlockq;

/* list of mounts that are (potentially) making lockd requests */
TAILQ_HEAD(nfs_lockd_mount_list, nfsmount) nfs_lockd_mount_list;

static lck_grp_t *nfs_lock_lck_grp;
static lck_mtx_t *nfs_lock_mutex;

void nfs_lockdmsg_enqueue(LOCKD_MSG_REQUEST *);
void nfs_lockdmsg_dequeue(LOCKD_MSG_REQUEST *);
int nfs_lockdmsg_compare_to_answer(LOCKD_MSG_REQUEST *, struct lockd_ans *);
LOCKD_MSG_REQUEST *nfs_lockdmsg_find_by_answer(struct lockd_ans *);
LOCKD_MSG_REQUEST *nfs_lockdmsg_find_by_xid(uint64_t);
uint64_t nfs_lockxid_get(void);
int nfs_lockd_send_request(LOCKD_MSG *, int);

/*
 * initialize global nfs lock state
 */
void
nfs_lockinit(void)
{
        TAILQ_INIT(&nfs_pendlockq);
        TAILQ_INIT(&nfs_lockd_mount_list);

        nfs_lock_lck_grp = lck_grp_alloc_init("nfs_lock", LCK_GRP_ATTR_NULL);
        nfs_lock_mutex = lck_mtx_alloc_init(nfs_lock_lck_grp, LCK_ATTR_NULL);
}

/*
 * Register a mount as (potentially) making lockd requests.
 */
void
nfs_lockd_mount_register(struct nfsmount *nmp)
{
        lck_mtx_lock(nfs_lock_mutex);
        TAILQ_INSERT_HEAD(&nfs_lockd_mount_list, nmp, nm_ldlink);
        nfs_lockd_mounts++;
        lck_mtx_unlock(nfs_lock_mutex);
}

/*
 * Unregister a mount as (potentially) making lockd requests.
 *
 * When the lockd mount count drops to zero, then send a shutdown request to
 * lockd if we've sent any requests to it.
 */
void
nfs_lockd_mount_unregister(struct nfsmount *nmp)
{
        int send_shutdown;
        mach_port_t lockd_port = IPC_PORT_NULL;
        kern_return_t kr;

        lck_mtx_lock(nfs_lock_mutex);
        if (nmp->nm_ldlink.tqe_next == NFSNOLIST) {
                lck_mtx_unlock(nfs_lock_mutex);
                return;
        }

        TAILQ_REMOVE(&nfs_lockd_mount_list, nmp, nm_ldlink);
        nmp->nm_ldlink.tqe_next = NFSNOLIST;

        nfs_lockd_mounts--;

        /* send a shutdown request if there are no more lockd mounts */
        send_shutdown = ((nfs_lockd_mounts == 0) && nfs_lockd_request_sent);
        if (send_shutdown) {
                nfs_lockd_request_sent = 0;
        }

        lck_mtx_unlock(nfs_lock_mutex);

        if (!send_shutdown) {
                return;
        }

        /*
         * Let lockd know that it is no longer needed for any NFS mounts
         */
        kr = host_get_lockd_port(host_priv_self(), &lockd_port);
        if ((kr != KERN_SUCCESS) || !IPC_PORT_VALID(lockd_port)) {
                printf("nfs_lockd_mount_change: shutdown couldn't get port, kr %d, port %s\n",
                    kr, (lockd_port == IPC_PORT_NULL) ? "NULL" :
                    (lockd_port == IPC_PORT_DEAD) ? "DEAD" : "VALID");
                return;
        }

        kr = lockd_shutdown(lockd_port);
        if (kr != KERN_SUCCESS) {
                printf("nfs_lockd_mount_change: shutdown %d\n", kr);
        }

        ipc_port_release_send(lockd_port);
}

/*
 * insert a lock request message into the pending queue
 * (nfs_lock_mutex must be held)
 */
void
nfs_lockdmsg_enqueue(LOCKD_MSG_REQUEST *msgreq)
{
        LOCKD_MSG_REQUEST *mr;

        mr = TAILQ_LAST(&nfs_pendlockq, nfs_lock_msg_queue);
        if (!mr || (msgreq->lmr_msg.lm_xid > mr->lmr_msg.lm_xid)) {
                /* fast path: empty queue or new largest xid */
                TAILQ_INSERT_TAIL(&nfs_pendlockq, msgreq, lmr_next);
                return;
        }
        /* slow path: need to walk list to find insertion point */
        while (mr && (msgreq->lmr_msg.lm_xid > mr->lmr_msg.lm_xid)) {
                mr = TAILQ_PREV(mr, nfs_lock_msg_queue, lmr_next);
        }
        if (mr) {
                TAILQ_INSERT_AFTER(&nfs_pendlockq, mr, msgreq, lmr_next);
        } else {
                TAILQ_INSERT_HEAD(&nfs_pendlockq, msgreq, lmr_next);
        }
}

/*
 * remove a lock request message from the pending queue
 * (nfs_lock_mutex must be held)
 */
void
nfs_lockdmsg_dequeue(LOCKD_MSG_REQUEST *msgreq)
{
        TAILQ_REMOVE(&nfs_pendlockq, msgreq, lmr_next);
}

/*
 * find a pending lock request message by xid
 *
 * We search from the head of the list assuming that the message we're
 * looking for is for an older request (because we have an answer to it).
 * This assumes that lock request will be answered primarily in FIFO order.
 * However, this may not be the case if there are blocked requests.  We may
 * want to move blocked requests to a separate queue (but that'll complicate
 * duplicate xid checking).
 *
 * (nfs_lock_mutex must be held)
 */
LOCKD_MSG_REQUEST *
nfs_lockdmsg_find_by_xid(uint64_t lockxid)
{
        LOCKD_MSG_REQUEST *mr;

        TAILQ_FOREACH(mr, &nfs_pendlockq, lmr_next) {
                if (mr->lmr_msg.lm_xid == lockxid) {
                        return mr;
                }
                if (mr->lmr_msg.lm_xid > lockxid) {
                        return NULL;
                }
        }
        return mr;
}

/*
 * Because we can't depend on nlm_granted messages containing the same
 * cookie we sent with the original lock request, we need code to test
 * if an nlm_granted answer matches the lock request.  We also need code
 * that can find a lockd message based solely on the nlm_granted answer.
 */

/*
 * compare lockd message to answer
 *
 * returns 0 on equality and 1 if different
 */
int
nfs_lockdmsg_compare_to_answer(LOCKD_MSG_REQUEST *msgreq, struct lockd_ans *ansp)
{
        if (!(ansp->la_flags & LOCKD_ANS_LOCK_INFO)) {
                return 1;
        }
        if (msgreq->lmr_msg.lm_fl.l_pid != ansp->la_pid) {
                return 1;
        }
        if (msgreq->lmr_msg.lm_fl.l_start != ansp->la_start) {
                return 1;
        }
        if (msgreq->lmr_msg.lm_fl.l_len != ansp->la_len) {
                return 1;
        }
        if (msgreq->lmr_msg.lm_fh_len != ansp->la_fh_len) {
                return 1;
        }
        if (bcmp(msgreq->lmr_msg.lm_fh, ansp->la_fh, ansp->la_fh_len)) {
                return 1;
        }
        return 0;
}

/*
 * find a pending lock request message based on the lock info provided
 * in the lockd_ans/nlm_granted data.  We need this because we can't
 * depend on nlm_granted messages containing the same cookie we sent
 * with the original lock request.
 *
 * We search from the head of the list assuming that the message we're
 * looking for is for an older request (because we have an answer to it).
 * This assumes that lock request will be answered primarily in FIFO order.
 * However, this may not be the case if there are blocked requests.  We may
 * want to move blocked requests to a separate queue (but that'll complicate
 * duplicate xid checking).
 *
 * (nfs_lock_mutex must be held)
 */
LOCKD_MSG_REQUEST *
nfs_lockdmsg_find_by_answer(struct lockd_ans *ansp)
{
        LOCKD_MSG_REQUEST *mr;

        if (!(ansp->la_flags & LOCKD_ANS_LOCK_INFO)) {
                return NULL;
        }
        TAILQ_FOREACH(mr, &nfs_pendlockq, lmr_next) {
                if (!nfs_lockdmsg_compare_to_answer(mr, ansp)) {
                        break;
                }
        }
        return mr;
}

/*
 * return the next unique lock request transaction ID
 * (nfs_lock_mutex must be held)
 */
uint64_t
nfs_lockxid_get(void)
{
        LOCKD_MSG_REQUEST *mr;

        /* derive initial lock xid from system time */
        if (!nfs_lockxid) {
                /*
                 * Note: it's OK if this code inits nfs_lockxid to 0 (for example,
                 * due to a broken clock) because we immediately increment it
                 * and we guarantee to never use xid 0.  So, nfs_lockxid should only
                 * ever be 0 the first time this function is called.
                 */
                struct timeval tv;
                microtime(&tv);
                nfs_lockxid = (uint64_t)tv.tv_sec << 12;
        }

        /* make sure we get a unique xid */
        do {
                /* Skip zero xid if it should ever happen.  */
                if (++nfs_lockxid == 0) {
                        nfs_lockxid++;
                }
                if (!(mr = TAILQ_LAST(&nfs_pendlockq, nfs_lock_msg_queue)) ||
                    (mr->lmr_msg.lm_xid < nfs_lockxid)) {
                        /* fast path: empty queue or new largest xid */
                        break;
                }
                /* check if xid is already in use */
        } while (nfs_lockdmsg_find_by_xid(nfs_lockxid));

        return nfs_lockxid;
}

#define MACH_MAX_TRIES 3

int
nfs_lockd_send_request(LOCKD_MSG *msg, int interruptable)
{
        kern_return_t kr;
        int retries = 0;
        mach_port_t lockd_port = IPC_PORT_NULL;

        kr = host_get_lockd_port(host_priv_self(), &lockd_port);
        if (kr != KERN_SUCCESS || !IPC_PORT_VALID(lockd_port)) {
                return ENOTSUP;
        }

        do {
                /* In the kernel all mach messaging is interruptable */
                do {
                        kr = lockd_request(
                                lockd_port,
                                msg->lm_version,
                                msg->lm_flags,
                                msg->lm_xid,
                                msg->lm_fl.l_start,
                                msg->lm_fl.l_len,
                                msg->lm_fl.l_pid,
                                msg->lm_fl.l_type,
                                msg->lm_fl.l_whence,
                                (uint32_t *)&msg->lm_addr,
                                (uint32_t *)&msg->lm_cred,
                                msg->lm_fh_len,
                                msg->lm_fh);
                        if (kr != KERN_SUCCESS) {
                                printf("lockd_request received %d!\n", kr);
                        }
                } while (!interruptable && kr == MACH_SEND_INTERRUPTED);
        } while (kr == MIG_SERVER_DIED && retries++ < MACH_MAX_TRIES);

        ipc_port_release_send(lockd_port);
        switch (kr) {
        case MACH_SEND_INTERRUPTED:
                return EINTR;
        default:
                /*
                 * Other MACH or MIG errors we will retry. Eventually
                 * we will call nfs_down and allow the user to disable
                 * locking.
                 */
                return EAGAIN;
        }
}

/*
 * NFS advisory byte-level locks (client)
 */
int
nfs3_lockd_request(
        nfsnode_t np,
        int type,
        LOCKD_MSG_REQUEST *msgreq,
        int flags,
        thread_t thd)
{
        LOCKD_MSG *msg = &msgreq->lmr_msg;
        int error, error2;
        int interruptable, slpflag;
        struct nfsmount *nmp;
        struct timeval now;
        int timeo, starttime, endtime, lastmsg, wentdown = 0;
        struct timespec ts;
        struct sockaddr *saddr;

        nmp = NFSTONMP(np);
        if (!nmp || !nmp->nm_saddr) {
                return ENXIO;
        }

        lck_mtx_lock(&nmp->nm_lock);
        saddr = nmp->nm_saddr;
        bcopy(saddr, &msg->lm_addr, min(sizeof msg->lm_addr, saddr->sa_len));
        if (nmp->nm_vers == NFS_VER3) {
                msg->lm_flags |= LOCKD_MSG_NFSV3;
        }

        if (nmp->nm_sotype != SOCK_DGRAM) {
                msg->lm_flags |= LOCKD_MSG_TCP;
        }

        microuptime(&now);
        starttime = now.tv_sec;
        lastmsg = now.tv_sec - ((nmp->nm_tprintf_delay) - (nmp->nm_tprintf_initial_delay));
        interruptable = NMFLAG(nmp, INTR);
        lck_mtx_unlock(&nmp->nm_lock);

        lck_mtx_lock(nfs_lock_mutex);

        /* allocate unique xid */
        msg->lm_xid = nfs_lockxid_get();
        nfs_lockdmsg_enqueue(msgreq);

        timeo = 4;

        for (;;) {
                nfs_lockd_request_sent = 1;

                /* need to drop nfs_lock_mutex while calling nfs_lockd_send_request() */
                lck_mtx_unlock(nfs_lock_mutex);
                error = nfs_lockd_send_request(msg, interruptable);
                lck_mtx_lock(nfs_lock_mutex);
                if (error && error != EAGAIN) {
                        break;
                }

                /*
                 * Always wait for an answer.  Not waiting for unlocks could
                 * cause a lock to be left if the unlock request gets dropped.
                 */

                /*
                 * Retry if it takes too long to get a response.
                 *
                 * The timeout numbers were picked out of thin air... they start
                 * at 4 and double each timeout with a max of 30 seconds.
                 *
                 * In order to maintain responsiveness, we pass a small timeout
                 * to msleep and calculate the timeouts ourselves.  This allows
                 * us to pick up on mount changes quicker.
                 */
wait_for_granted:
                error = EWOULDBLOCK;
                slpflag = (interruptable && (type != F_UNLCK)) ? PCATCH : 0;
                ts.tv_sec = 2;
                ts.tv_nsec = 0;
                microuptime(&now);
                endtime = now.tv_sec + timeo;
                while (now.tv_sec < endtime) {
                        error = error2 = 0;
                        if (!msgreq->lmr_answered) {
                                error = msleep(msgreq, nfs_lock_mutex, slpflag | PUSER, "lockd", &ts);
                                slpflag = 0;
                        }
                        if (msgreq->lmr_answered) {
                                /*
                                 * Note: it's possible to have a lock granted at
                                 * essentially the same time that we get interrupted.
                                 * Since the lock may be granted, we can't return an
                                 * error from this request or we might not unlock the
                                 * lock that's been granted.
                                 */
                                nmp = NFSTONMP(np);
                                if ((msgreq->lmr_errno == ENOTSUP) && nmp &&
                                    (nmp->nm_state & NFSSTA_LOCKSWORK)) {
                                        /*
                                         * We have evidence that locks work, yet lockd
                                         * returned ENOTSUP.  This is probably because
                                         * it was unable to contact the server's lockd
                                         * to send it the request.
                                         *
                                         * Because we know locks work, we'll consider
                                         * this failure to be a timeout.
                                         */
                                        error = EWOULDBLOCK;
                                } else {
                                        error = 0;
                                }
                                break;
                        }
                        if (error != EWOULDBLOCK) {
                                break;
                        }
                        /* check that we still have our mount... */
                        /* ...and that we still support locks */
                        /* ...and that there isn't a recovery pending */
                        nmp = NFSTONMP(np);
                        if ((error2 = nfs_sigintr(nmp, NULL, NULL, 0))) {
                                error = error2;
                                if (type == F_UNLCK) {
                                        printf("nfs3_lockd_request: aborting unlock request, error %d\n", error);
                                }
                                break;
                        }
                        lck_mtx_lock(&nmp->nm_lock);
                        if (nmp->nm_lockmode == NFS_LOCK_MODE_DISABLED) {
                                lck_mtx_unlock(&nmp->nm_lock);
                                break;
                        }
                        if ((nmp->nm_state & NFSSTA_RECOVER) && !(flags & R_RECOVER)) {
                                /* recovery pending... return an error that'll get this operation restarted */
                                error = NFSERR_GRACE;
                                lck_mtx_unlock(&nmp->nm_lock);
                                break;
                        }
                        interruptable = NMFLAG(nmp, INTR);
                        lck_mtx_unlock(&nmp->nm_lock);
                        microuptime(&now);
                }
                if (error) {
                        /* check that we still have our mount... */
                        nmp = NFSTONMP(np);
                        if ((error2 = nfs_sigintr(nmp, NULL, NULL, 0))) {
                                error = error2;
                                if (error2 != EINTR) {
                                        if (type == F_UNLCK) {
                                                printf("nfs3_lockd_request: aborting unlock request, error %d\n", error);
                                        }
                                        break;
                                }
                        }
                        /* ...and that we still support locks */
                        lck_mtx_lock(&nmp->nm_lock);
                        if (nmp->nm_lockmode == NFS_LOCK_MODE_DISABLED) {
                                if (error == EWOULDBLOCK) {
                                        error = ENOTSUP;
                                }
                                lck_mtx_unlock(&nmp->nm_lock);
                                break;
                        }
                        /* ...and that there isn't a recovery pending */
                        if ((error == EWOULDBLOCK) && (nmp->nm_state & NFSSTA_RECOVER) && !(flags & R_RECOVER)) {
                                /* recovery pending... return to allow recovery to occur */
                                error = NFSERR_DENIED;
                                lck_mtx_unlock(&nmp->nm_lock);
                                break;
                        }
                        interruptable = NMFLAG(nmp, INTR);
                        if ((error != EWOULDBLOCK) ||
                            ((nmp->nm_state & NFSSTA_RECOVER) && !(flags & R_RECOVER)) ||
                            ((flags & R_RECOVER) && ((now.tv_sec - starttime) > 30))) {
                                if ((error == EWOULDBLOCK) && (flags & R_RECOVER)) {
                                        /* give up if this is for recovery and taking too long */
                                        error = ETIMEDOUT;
                                } else if ((nmp->nm_state & NFSSTA_RECOVER) && !(flags & R_RECOVER)) {
                                        /* recovery pending... return an error that'll get this operation restarted */
                                        error = NFSERR_GRACE;
                                }
                                lck_mtx_unlock(&nmp->nm_lock);
                                /*
                                 * We're going to bail on this request.
                                 * If we were a blocked lock request, send a cancel.
                                 */
                                if ((msgreq->lmr_errno == EINPROGRESS) &&
                                    !(msg->lm_flags & LOCKD_MSG_CANCEL)) {
                                        /* set this request up as a cancel */
                                        msg->lm_flags |= LOCKD_MSG_CANCEL;
                                        nfs_lockdmsg_dequeue(msgreq);
                                        msg->lm_xid = nfs_lockxid_get();
                                        nfs_lockdmsg_enqueue(msgreq);
                                        msgreq->lmr_saved_errno = error;
                                        msgreq->lmr_errno = 0;
                                        msgreq->lmr_answered = 0;
                                        /* reset timeout */
                                        timeo = 2;
                                        /* send cancel request */
                                        continue;
                                }
                                break;
                        }

                        /* warn if we're not getting any response */
                        microuptime(&now);
                        if ((msgreq->lmr_errno != EINPROGRESS) &&
                            !(msg->lm_flags & LOCKD_MSG_DENIED_GRACE) &&
                            (nmp->nm_tprintf_initial_delay != 0) &&
                            ((lastmsg + nmp->nm_tprintf_delay) < now.tv_sec)) {
                                lck_mtx_unlock(&nmp->nm_lock);
                                lastmsg = now.tv_sec;
                                nfs_down(nmp, thd, 0, NFSSTA_LOCKTIMEO, "lockd not responding", 1);
                                wentdown = 1;
                        } else {
                                lck_mtx_unlock(&nmp->nm_lock);
                        }

                        if (msgreq->lmr_errno == EINPROGRESS) {
                                /*
                                 * We've got a blocked lock request that we are
                                 * going to retry.  First, we'll want to try to
                                 * send a cancel for the previous request.
                                 *
                                 * Clear errno so if we don't get a response
                                 * to the resend we'll call nfs_down().
                                 * Also reset timeout because we'll expect a
                                 * quick response to the cancel/resend (even if
                                 * it is NLM_BLOCKED).
                                 */
                                msg->lm_flags |= LOCKD_MSG_CANCEL;
                                nfs_lockdmsg_dequeue(msgreq);
                                msg->lm_xid = nfs_lockxid_get();
                                nfs_lockdmsg_enqueue(msgreq);
                                msgreq->lmr_saved_errno = msgreq->lmr_errno;
                                msgreq->lmr_errno = 0;
                                msgreq->lmr_answered = 0;
                                timeo = 2;
                                /* send cancel then resend request */
                                continue;
                        }

                        /*
                         * We timed out, so we will resend the request.
                         */
                        if (!(flags & R_RECOVER)) {
                                timeo *= 2;
                        }
                        if (timeo > 30) {
                                timeo = 30;
                        }
                        /* resend request */
                        continue;
                }

                /* we got a reponse, so the server's lockd is OK */
                nfs_up(NFSTONMP(np), thd, NFSSTA_LOCKTIMEO,
                    wentdown ? "lockd alive again" : NULL);
                wentdown = 0;

                if (msgreq->lmr_answered && (msg->lm_flags & LOCKD_MSG_DENIED_GRACE)) {
                        /*
                         * The lock request was denied because the server lockd is
                         * still in its grace period.  So, we need to try the
                         * request again in a little bit.  Return the GRACE error so
                         * the higher levels can perform the retry.
                         */
                        msgreq->lmr_saved_errno = msgreq->lmr_errno = error = NFSERR_GRACE;
                }

                if (msgreq->lmr_errno == EINPROGRESS) {
                        /* got NLM_BLOCKED response */
                        /* need to wait for NLM_GRANTED */
                        timeo = 30;
                        msgreq->lmr_answered = 0;
                        goto wait_for_granted;
                }

                if ((msg->lm_flags & LOCKD_MSG_CANCEL) &&
                    (msgreq->lmr_saved_errno == EINPROGRESS)) {
                        /*
                         * We just got a successful reply to the
                         * cancel of the previous blocked lock request.
                         * Now, go ahead and return a DENIED error so the
                         * higher levels can resend the request.
                         */
                        msg->lm_flags &= ~LOCKD_MSG_CANCEL;
                        error = NFSERR_DENIED;
                        /* Will dequeue msgreq after the following break at the end of this routine */
                        break;
                }

                /*
                 * If the blocked lock request was cancelled.
                 * Restore the error condition from when we
                 * originally bailed on the request.
                 */
                if (msg->lm_flags & LOCKD_MSG_CANCEL) {
                        msg->lm_flags &= ~LOCKD_MSG_CANCEL;
                        error = msgreq->lmr_saved_errno;
                } else {
                        error = msgreq->lmr_errno;
                }

                nmp = NFSTONMP(np);
                if ((error == ENOTSUP) && nmp && !(nmp->nm_state & NFSSTA_LOCKSWORK)) {
                        /*
                         * We have NO evidence that locks work and lockd
                         * returned ENOTSUP.  Let's take this as a hint
                         * that locks aren't supported and disable them
                         * for this mount.
                         */
                        nfs_lockdmsg_dequeue(msgreq);
                        lck_mtx_unlock(nfs_lock_mutex);
                        lck_mtx_lock(&nmp->nm_lock);
                        if (nmp->nm_lockmode == NFS_LOCK_MODE_ENABLED) {
                                nmp->nm_lockmode = NFS_LOCK_MODE_DISABLED;
                                nfs_lockd_mount_unregister(nmp);
                        }
                        nmp->nm_state &= ~NFSSTA_LOCKTIMEO;
                        lck_mtx_unlock(&nmp->nm_lock);
                        printf("lockd returned ENOTSUP, disabling locks for nfs server: %s\n",
                            vfs_statfs(nmp->nm_mountp)->f_mntfromname);
                        return error;
                }
                if (!error) {
                        /* record that NFS file locking has worked on this mount */
                        if (nmp) {
                                lck_mtx_lock(&nmp->nm_lock);
                                if (!(nmp->nm_state & NFSSTA_LOCKSWORK)) {
                                        nmp->nm_state |= NFSSTA_LOCKSWORK;
                                }
                                lck_mtx_unlock(&nmp->nm_lock);
                        }
                }
                break;
        }

        nfs_lockdmsg_dequeue(msgreq);

        lck_mtx_unlock(nfs_lock_mutex);

        return error;
}

/*
 * Send an NLM LOCK message to the server
 */
int
nfs3_setlock_rpc(
        nfsnode_t np,
        struct nfs_open_file *nofp,
        struct nfs_file_lock *nflp,
        int reclaim,
        int flags,
        thread_t thd,
        kauth_cred_t cred)
{
        struct nfs_lock_owner *nlop = nflp->nfl_owner;
        struct nfsmount *nmp;
        int error;
        LOCKD_MSG_REQUEST msgreq;
        LOCKD_MSG *msg;

        nmp = NFSTONMP(np);
        if (nfs_mount_gone(nmp)) {
                return ENXIO;
        }

        if (!nlop->nlo_open_owner) {
                nfs_open_owner_ref(nofp->nof_owner);
                nlop->nlo_open_owner = nofp->nof_owner;
        }
        if ((error = nfs_lock_owner_set_busy(nlop, thd))) {
                return error;
        }

        /* set up lock message request structure */
        bzero(&msgreq, sizeof(msgreq));
        msg = &msgreq.lmr_msg;
        msg->lm_version = LOCKD_MSG_VERSION;
        if ((nflp->nfl_flags & NFS_FILE_LOCK_WAIT) && !reclaim) {
                msg->lm_flags |= LOCKD_MSG_BLOCK;
        }
        if (reclaim) {
                msg->lm_flags |= LOCKD_MSG_RECLAIM;
        }
        msg->lm_fh_len = (nmp->nm_vers == NFS_VER2) ? NFSX_V2FH : np->n_fhsize;
        bcopy(np->n_fhp, msg->lm_fh, msg->lm_fh_len);
        cru2x(cred, &msg->lm_cred);

        msg->lm_fl.l_whence = SEEK_SET;
        msg->lm_fl.l_start = nflp->nfl_start;
        msg->lm_fl.l_len = NFS_FLOCK_LENGTH(nflp->nfl_start, nflp->nfl_end);
        msg->lm_fl.l_type = nflp->nfl_type;
        msg->lm_fl.l_pid = nlop->nlo_pid;

        error = nfs3_lockd_request(np, 0, &msgreq, flags, thd);

        nfs_lock_owner_clear_busy(nlop);
        return error;
}

/*
 * Send an NLM UNLOCK message to the server
 */
int
nfs3_unlock_rpc(
        nfsnode_t np,
        struct nfs_lock_owner *nlop,
        __unused int type,
        uint64_t start,
        uint64_t end,
        int flags,
        thread_t thd,
        kauth_cred_t cred)
{
        struct nfsmount *nmp;
        LOCKD_MSG_REQUEST msgreq;
        LOCKD_MSG *msg;

        nmp = NFSTONMP(np);
        if (!nmp) {
                return ENXIO;
        }

        /* set up lock message request structure */
        bzero(&msgreq, sizeof(msgreq));
        msg = &msgreq.lmr_msg;
        msg->lm_version = LOCKD_MSG_VERSION;
        msg->lm_fh_len = (nmp->nm_vers == NFS_VER2) ? NFSX_V2FH : np->n_fhsize;
        bcopy(np->n_fhp, msg->lm_fh, msg->lm_fh_len);
        cru2x(cred, &msg->lm_cred);

        msg->lm_fl.l_whence = SEEK_SET;
        msg->lm_fl.l_start = start;
        msg->lm_fl.l_len = NFS_FLOCK_LENGTH(start, end);
        msg->lm_fl.l_type = F_UNLCK;
        msg->lm_fl.l_pid = nlop->nlo_pid;

        return nfs3_lockd_request(np, F_UNLCK, &msgreq, flags, thd);
}

/*
 * Send an NLM LOCK TEST message to the server
 */
int
nfs3_getlock_rpc(
        nfsnode_t np,
        struct nfs_lock_owner *nlop,
        struct flock *fl,
        uint64_t start,
        uint64_t end,
        vfs_context_t ctx)
{
        struct nfsmount *nmp;
        int error;
        LOCKD_MSG_REQUEST msgreq;
        LOCKD_MSG *msg;

        nmp = NFSTONMP(np);
        if (nfs_mount_gone(nmp)) {
                return ENXIO;
        }

        /* set up lock message request structure */
        bzero(&msgreq, sizeof(msgreq));
        msg = &msgreq.lmr_msg;
        msg->lm_version = LOCKD_MSG_VERSION;
        msg->lm_flags |= LOCKD_MSG_TEST;
        msg->lm_fh_len = (nmp->nm_vers == NFS_VER2) ? NFSX_V2FH : np->n_fhsize;
        bcopy(np->n_fhp, msg->lm_fh, msg->lm_fh_len);
        cru2x(vfs_context_ucred(ctx), &msg->lm_cred);

        msg->lm_fl.l_whence = SEEK_SET;
        msg->lm_fl.l_start = start;
        msg->lm_fl.l_len = NFS_FLOCK_LENGTH(start, end);
        msg->lm_fl.l_type = fl->l_type;
        msg->lm_fl.l_pid = nlop->nlo_pid;

        error = nfs3_lockd_request(np, 0, &msgreq, 0, vfs_context_thread(ctx));

        if (!error && (msg->lm_flags & LOCKD_MSG_TEST) && !msgreq.lmr_errno) {
                if (msg->lm_fl.l_type != F_UNLCK) {
                        fl->l_type = msg->lm_fl.l_type;
                        fl->l_pid = msg->lm_fl.l_pid;
                        fl->l_start = msg->lm_fl.l_start;
                        fl->l_len = msg->lm_fl.l_len;
                        fl->l_whence = SEEK_SET;
                } else {
                        fl->l_type = F_UNLCK;
                }
        }

        return error;
}

/*
 * nfslockdans --
 *      NFS advisory byte-level locks answer from the lock daemon.
 */
int
nfslockdans(proc_t p, struct lockd_ans *ansp)
{
        LOCKD_MSG_REQUEST *msgreq;
        int error;

        /* Let root make this call. */
        error = proc_suser(p);
        if (error) {
                return error;
        }

        /* the version should match, or we're out of sync */
        if (ansp->la_version != LOCKD_ANS_VERSION) {
                return EINVAL;
        }

        lck_mtx_lock(nfs_lock_mutex);

        /* try to find the lockd message by transaction id (cookie) */
        msgreq = nfs_lockdmsg_find_by_xid(ansp->la_xid);
        if (ansp->la_flags & LOCKD_ANS_GRANTED) {
                /*
                 * We can't depend on the granted message having our cookie,
                 * so we check the answer against the lockd message found.
                 * If no message was found or it doesn't match the answer,
                 * we look for the lockd message by the answer's lock info.
                 */
                if (!msgreq || nfs_lockdmsg_compare_to_answer(msgreq, ansp)) {
                        msgreq = nfs_lockdmsg_find_by_answer(ansp);
                }
                /*
                 * We need to make sure this request isn't being cancelled
                 * If it is, we don't want to accept the granted message.
                 */
                if (msgreq && (msgreq->lmr_msg.lm_flags & LOCKD_MSG_CANCEL)) {
                        msgreq = NULL;
                }
        }
        if (!msgreq) {
                lck_mtx_unlock(nfs_lock_mutex);
                return EPIPE;
        }

        msgreq->lmr_errno = ansp->la_errno;
        if ((msgreq->lmr_msg.lm_flags & LOCKD_MSG_TEST) && msgreq->lmr_errno == 0) {
                if (ansp->la_flags & LOCKD_ANS_LOCK_INFO) {
                        if (ansp->la_flags & LOCKD_ANS_LOCK_EXCL) {
                                msgreq->lmr_msg.lm_fl.l_type = F_WRLCK;
                        } else {
                                msgreq->lmr_msg.lm_fl.l_type = F_RDLCK;
                        }
                        msgreq->lmr_msg.lm_fl.l_pid = ansp->la_pid;
                        msgreq->lmr_msg.lm_fl.l_start = ansp->la_start;
                        msgreq->lmr_msg.lm_fl.l_len = ansp->la_len;
                } else {
                        msgreq->lmr_msg.lm_fl.l_type = F_UNLCK;
                }
        }
        if (ansp->la_flags & LOCKD_ANS_DENIED_GRACE) {
                msgreq->lmr_msg.lm_flags |= LOCKD_MSG_DENIED_GRACE;
        }

        msgreq->lmr_answered = 1;
        lck_mtx_unlock(nfs_lock_mutex);
        wakeup(msgreq);

        return 0;
}

/*
 * nfslockdnotify --
 *      NFS host restart notification from the lock daemon.
 *
 * Used to initiate reclaiming of held locks when a server we
 * have mounted reboots.
 */
int
nfslockdnotify(proc_t p, user_addr_t argp)
{
        int error, i, headsize;
        struct lockd_notify ln;
        struct nfsmount *nmp;
        struct sockaddr *saddr;

        /* Let root make this call. */
        error = proc_suser(p);
        if (error) {
                return error;
        }

        headsize = (char*)&ln.ln_addr[0] - (char*)&ln.ln_version;
        error = copyin(argp, &ln, headsize);
        if (error) {
                return error;
        }
        if (ln.ln_version != LOCKD_NOTIFY_VERSION) {
                return EINVAL;
        }
        if ((ln.ln_addrcount < 1) || (ln.ln_addrcount > 128)) {
                return EINVAL;
        }
        argp += headsize;
        saddr = (struct sockaddr *)&ln.ln_addr[0];

        lck_mtx_lock(nfs_lock_mutex);

        for (i = 0; i < ln.ln_addrcount; i++) {
                error = copyin(argp, &ln.ln_addr[0], sizeof(ln.ln_addr[0]));
                if (error) {
                        break;
                }
                argp += sizeof(ln.ln_addr[0]);
                /* scan lockd mount list for match to this address */
                TAILQ_FOREACH(nmp, &nfs_lockd_mount_list, nm_ldlink) {
                        /* check if address matches this mount's server address */
                        if (!nmp->nm_saddr || nfs_sockaddr_cmp(saddr, nmp->nm_saddr)) {
                                continue;
                        }
                        /* We have a match!  Mark it as needing recovery. */
                        lck_mtx_lock(&nmp->nm_lock);
                        nfs_need_recover(nmp, 0);
                        lck_mtx_unlock(&nmp->nm_lock);
                }
        }

        lck_mtx_unlock(nfs_lock_mutex);

        return error;
}