This is xnu-6153.11.26. See this file in:
/*
 * 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;
}