dmake: do not set MAKEFLAGS=k

[unleashed/tickless.git] / kernel / fs / nfs / nfs4_idmap.c

/*
 * CDDL HEADER START
 *
 * The contents of this file are subject to the terms of the
 * Common Development and Distribution License (the "License").
 * You may not use this file except in compliance with the License.
 *
 * You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE
 * or http://www.opensolaris.org/os/licensing.
 * See the License for the specific language governing permissions
 * and limitations under the License.
 *
 * When distributing Covered Code, include this CDDL HEADER in each
 * file and include the License file at usr/src/OPENSOLARIS.LICENSE.
 * If applicable, add the following below this CDDL HEADER, with the
 * fields enclosed by brackets "[]" replaced with your own identifying
 * information: Portions Copyright [yyyy] [name of copyright owner]
 *
 * CDDL HEADER END
 */
/*
 * Copyright (c) 2003, 2010, Oracle and/or its affiliates. All rights reserved.
 */


/*
 * There are well defined policies for mapping uid and gid values to and
 * from utf8 strings, as specified in RFC 7530. The protocol ops that are
 * most significantly affected by any changes in policy are GETATTR and
 * SETATTR, as these have different behavior depending on whether the id
 * mapping code is executing on the client or server. Thus, the following
 * rules represents the latest incantation of the id mapping policies.
 *
 * 1) For the case in which the nfsmapid(1m) daemon has _never_ been
 *    started, the policy is to _always_ work with stringified uid's
 *    and gid's
 *
 * 2) For the case in which the nfsmapid(1m) daemon _was_ started but
 *    has either died or become unresponsive, the mapping policies are
 *    as follows:
 *
 *                      Server                             Client
 *         .-------------------------------.---------------------------------.
 *         |                               |                                 |
 *         | . Respond to req by replying  | . If attr string does not have  |
 *         |   success and map the [u/g]id |   '@' sign, attempt to decode   |
 *         |   into its literal id string  |   a stringified id; map to      |
 *         |                               |   *ID_NOBODY if not an encoded  |
 *         |                               |   id.                           |
 *         |                               |                                 |
 * GETATTR |                               | . If attr string _does_ have    |
 *         |                               |   '@' sign                      |
 *         |                               |   Map to *ID_NOBODY on failure. |
 *         |                               |                                 |
 *         | nfs_idmap_*id_str             | nfs_idmap_str_*id               |
 *         +-------------------------------+---------------------------------+
 *         |                               |                                 |
 *         | . Respond to req by returning | . _Must_ map the user's passed  |
 *         |  ECOMM, which will be mapped  |  in [u/g]id into it's network   |
 *         |  to NFS4ERR_DELAY to clnt     |  attr string, so contact the    |
 *         |                               |  daemon, retrying forever if    |
 *         |   Server must not allow the   |  necessary, unless interrupted  |
 * SETATTR |   mapping to *ID_NOBODY upon  |                                 |
 *         |   lack of communication with  |   Client _should_ specify the   |
 *         |   the daemon, which could     |   correct attr string for a     |
 *         |   result in the file being    |   SETATTR operation, otherwise  |
 *         |   inadvertently given away !  |   it can also result in the     |
 *         |                               |   file being inadvertently      |
 *         |                               |   given away !                  |
 *         |                               |                                 |
 *         | nfs_idmap_str_*id             |   nfs_idmap_*id_str             |
 *         `-------------------------------'---------------------------------'
 *
 * 3) Lastly, in order to leverage better cache utilization whenever
 *    communication with nfsmapid(1m) is currently hindered, cache
 *    entry eviction is throttled whenever nfsidmap_daemon_dh == NULL.
 *
 *
 *  Server-side behavior for upcall communication errors
 *  ====================================================
 *
 *   GETATTR - Server-side GETATTR *id to attr string conversion policies
 *             for unresponsive/dead nfsmapid(1m) daemon
 *
 *      a) If the *id is *ID_NOBODY, the string "nobody" is returned
 *
 *      b) If the *id is not *ID_NOBODY _and_ the nfsmapid(1m) daemon
 *         _is_ operational, the daemon is contacted to convert the
 *         [u/g]id into a string of type "[user/group]@domain"
 *
 *      c) If the nfsmapid(1m) daemon has died or has become unresponsive,
 *         the server returns status == NFS4_OK for the GETATTR operation,
 *         and returns a strigified [u/g]id to let the client map it into
 *         the appropriate value.
 *
 *   SETATTR - Server-side SETATTR attr string to *id conversion policies
 *             for unresponsive/dead nfsmapid(1m) daemon
 *
 *      a) If the otw string is a stringified uid (ie. does _not_ contain
 *         an '@' sign and is of the form "12345") then the literal uid is
 *         decoded and it is used to perform the mapping.
 *
 *      b) If, on the other hand, the otw string _is_ of the form
 *         "[user/group]@domain" and problems arise contacting nfsmapid(1m),
 *         the SETATTR operation _must_ fail w/NFS4ERR_DELAY, as the server
 *         cannot default to *ID_NOBODY, which would allow a file to be
 *         given away by setting it's owner or owner_group to "nobody".
 */
#include <sys/param.h>
#include <sys/errno.h>
#include <sys/disp.h>
#include <sys/vfs.h>
#include <sys/vnode.h>
#include <sys/cred.h>
#include <sys/cmn_err.h>
#include <sys/systm.h>
#include <sys/kmem.h>
#include <sys/pathname.h>
#include <sys/utsname.h>
#include <sys/debug.h>
#include <sys/sysmacros.h>
#include <sys/list.h>
#include <sys/sunddi.h>
#include <sys/dnlc.h>
#include <sys/sdt.h>
#include <sys/pkp_hash.h>
#include <nfs/nfs4.h>
#include <nfs/rnode4.h>
#include <nfs/nfsid_map.h>
#include <nfs/nfs4_idmap_impl.h>
#include <nfs/nfssys.h>

/*
 * Truly global modular globals
 */
zone_key_t                      nfsidmap_zone_key;
static list_t                   nfsidmap_globals_list;
static kmutex_t                 nfsidmap_globals_lock;
static kmem_cache_t             *nfsidmap_cache;
static int                      nfs4_idcache_tout;

/*
 * Some useful macros
 */
#define         MOD2(a, pow_of_2)       ((a) & ((pow_of_2) - 1))
#define         _CACHE_TOUT             (60*60)         /* secs in 1 hour */
#define         TIMEOUT(x)              (gethrestime_sec() > \
                                        ((x) + nfs4_idcache_tout))
/*
 * Max length of valid id string including the trailing null
 */
#define         _MAXIDSTRLEN            11

#define         ID_HASH(id, hash)                                       \
{                                                                       \
        (hash) = MOD2(((id) ^ NFSID_CACHE_ANCHORS), NFSID_CACHE_ANCHORS); \
}

/*
 * Prototypes
 */

static void     *nfs_idmap_init_zone(zoneid_t);
static void      nfs_idmap_fini_zone(zoneid_t, void *);

static int       is_stringified_id(utf8string *);
static void      nfs_idmap_i2s_literal(uid_t, utf8string *);
static int       nfs_idmap_s2i_literal(utf8string *, uid_t *, int);
static void      nfs_idmap_reclaim(void *);
static void      nfs_idmap_cache_reclaim(idmap_cache_info_t *);
static void      nfs_idmap_cache_create(idmap_cache_info_t *, const char *);
static void      nfs_idmap_cache_destroy(idmap_cache_info_t *);
static void      nfs_idmap_cache_flush(idmap_cache_info_t *);

static uint_t    nfs_idmap_cache_s2i_lkup(idmap_cache_info_t *, utf8string *,
                        uint_t *, uid_t *);

static uint_t    nfs_idmap_cache_i2s_lkup(idmap_cache_info_t *, uid_t,
                        uint_t *, utf8string *);

static void      nfs_idmap_cache_s2i_insert(idmap_cache_info_t *, uid_t,
                        utf8string *, hash_stat, uint_t);

static void      nfs_idmap_cache_i2s_insert(idmap_cache_info_t *, uid_t,
                        utf8string *, hash_stat, uint_t);

static void      nfs_idmap_cache_rment(nfsidmap_t *);

/*
 * Initialization routine for NFSv4 id mapping
 */
void
nfs_idmap_init(void)
{
        /*
         * Initialize the kmem cache
         */
        nfsidmap_cache = kmem_cache_create("NFS_idmap_cache",
            sizeof (nfsidmap_t), 0, NULL, NULL, nfs_idmap_reclaim, NULL,
            NULL, 0);
        /*
         * If not set in "/etc/system", set to default value
         */
        if (!nfs4_idcache_tout)
                nfs4_idcache_tout = _CACHE_TOUT;
        /*
         * Initialize the list of nfsidmap_globals
         */
        mutex_init(&nfsidmap_globals_lock, NULL, MUTEX_DEFAULT, NULL);
        list_create(&nfsidmap_globals_list, sizeof (struct nfsidmap_globals),
            offsetof(struct nfsidmap_globals, nig_link));
        /*
         * Initialize the zone_key_t for per-zone idmaps
         */
        zone_key_create(&nfsidmap_zone_key, nfs_idmap_init_zone, NULL,
            nfs_idmap_fini_zone);
}

/*
 * Called only when module was not loaded properly
 */
void
nfs_idmap_fini(void)
{
        (void) zone_key_delete(nfsidmap_zone_key);
        list_destroy(&nfsidmap_globals_list);
        mutex_destroy(&nfsidmap_globals_lock);
        kmem_cache_destroy(nfsidmap_cache);
}

/*ARGSUSED*/
static void *
nfs_idmap_init_zone(zoneid_t zoneid)
{
        struct nfsidmap_globals *nig;

        nig = kmem_alloc(sizeof (*nig), KM_SLEEP);
        nig->nig_msg_done = 0;
        mutex_init(&nig->nfsidmap_daemon_lock, NULL, MUTEX_DEFAULT, NULL);

        /*
         * nfsidmap certainly isn't running.
         */
        nig->nfsidmap_pid = NOPID;
        nig->nfsidmap_daemon_dh = NULL;

        /*
         * Create the idmap caches
         */
        nfs_idmap_cache_create(&nig->u2s_ci, "u2s_cache");
        nig->u2s_ci.nfsidmap_daemon_dh = &nig->nfsidmap_daemon_dh;
        nfs_idmap_cache_create(&nig->s2u_ci, "s2u_cache");
        nig->s2u_ci.nfsidmap_daemon_dh = &nig->nfsidmap_daemon_dh;
        nfs_idmap_cache_create(&nig->g2s_ci, "g2s_cache");
        nig->g2s_ci.nfsidmap_daemon_dh = &nig->nfsidmap_daemon_dh;
        nfs_idmap_cache_create(&nig->s2g_ci, "s2g_cache");
        nig->s2g_ci.nfsidmap_daemon_dh = &nig->nfsidmap_daemon_dh;

        /*
         * Add to global list.
         */
        mutex_enter(&nfsidmap_globals_lock);
        list_insert_head(&nfsidmap_globals_list, nig);
        mutex_exit(&nfsidmap_globals_lock);

        return (nig);
}

/*ARGSUSED*/
static void
nfs_idmap_fini_zone(zoneid_t zoneid, void *arg)
{
        struct nfsidmap_globals *nig = arg;

        /*
         * Remove from list.
         */
        mutex_enter(&nfsidmap_globals_lock);
        list_remove(&nfsidmap_globals_list, nig);
        /*
         * Destroy the idmap caches
         */
        nfs_idmap_cache_destroy(&nig->u2s_ci);
        nfs_idmap_cache_destroy(&nig->s2u_ci);
        nfs_idmap_cache_destroy(&nig->g2s_ci);
        nfs_idmap_cache_destroy(&nig->s2g_ci);
        mutex_exit(&nfsidmap_globals_lock);
        /*
         * Cleanup
         */
        if (nig->nfsidmap_daemon_dh)
                door_ki_rele(nig->nfsidmap_daemon_dh);
        mutex_destroy(&nig->nfsidmap_daemon_lock);
        kmem_free(nig, sizeof (*nig));
}

/*
 * Convert a user utf-8 string identifier into its local uid.
 */
int
nfs_idmap_str_uid(utf8string *u8s, uid_t *uid, bool_t isserver)
{
        int                     error;
        uint_t                  hashno = 0;
        const char              *whoami = "nfs_idmap_str_uid";
        struct nfsidmap_globals *nig;
        struct mapid_arg        *mapargp;
        struct mapid_res        mapres;
        struct mapid_res        *mapresp = &mapres;
        struct mapid_res        *resp = mapresp;
        door_arg_t              door_args;
        door_handle_t           dh;

        nig = zone_getspecific(nfsidmap_zone_key, nfs_zone());
        ASSERT(nig != NULL);

        if (!u8s || !u8s->utf8string_val || u8s->utf8string_len == 0 ||
            (u8s->utf8string_val[0] == '\0')) {
                *uid = UID_NOBODY;
                return (isserver ? EINVAL : 0);
        }

        /*
         * If "nobody", just short circuit and bail
         */
        if (bcmp(u8s->utf8string_val, "nobody", 6) == 0) {
                *uid = UID_NOBODY;
                return (0);
        }

        /*
         * Start-off with upcalls disabled, and once nfsmapid(1m) is up and
         * running, we'll leverage it's first flush to let the kernel know
         * when it's up and available to perform mappings. Also, on client
         * only, be smarter about when to issue upcalls by checking the
         * string for existence of an '@' sign. If no '@' sign, then we just
         * make our best effort to decode the string ourselves.
         */
retry:
        mutex_enter(&nig->nfsidmap_daemon_lock);
        dh = nig->nfsidmap_daemon_dh;
        if (dh)
                door_ki_hold(dh);
        mutex_exit(&nig->nfsidmap_daemon_lock);

        if (dh == NULL || nig->nfsidmap_pid == curproc->p_pid ||
            (!utf8_strchr(u8s, '@') && !isserver)) {
                if (dh)
                        door_ki_rele(dh);
                error = nfs_idmap_s2i_literal(u8s, uid, isserver);
                /*
                 * If we get a numeric value, but we only do so because
                 * we are nfsmapid, return ENOTSUP to indicate a valid
                 * response, but not to cache it.
                 */
                if (!error && nig->nfsidmap_pid == curproc->p_pid)
                        return (ENOTSUP);
                return (error);
        }

        /* cache hit */
        if (nfs_idmap_cache_s2i_lkup(&nig->s2u_ci, u8s, &hashno, uid)) {
                door_ki_rele(dh);
                return (0);
        }

        /* cache miss */
        mapargp = kmem_alloc(MAPID_ARG_LEN(u8s->utf8string_len), KM_SLEEP);
        mapargp->cmd = NFSMAPID_STR_UID;
        mapargp->u_arg.len = u8s->utf8string_len;
        (void) bcopy(u8s->utf8string_val, mapargp->str, mapargp->u_arg.len);
        mapargp->str[mapargp->u_arg.len] = '\0';

        door_args.data_ptr = (char *)mapargp;
        door_args.data_size = MAPID_ARG_LEN(mapargp->u_arg.len);
        door_args.desc_ptr = NULL;
        door_args.desc_num = 0;
        door_args.rbuf = (char *)mapresp;
        door_args.rsize = sizeof (struct mapid_res);

        error = door_ki_upcall_limited(dh, &door_args, NULL, SIZE_MAX, 0);
        if (!error) {
                resp = (struct mapid_res *)door_args.rbuf;

                /* Should never provide daemon with bad args */
                ASSERT(resp->status != NFSMAPID_INVALID);

                switch (resp->status) {
                case NFSMAPID_OK:
                        /*
                         * Valid mapping. Cache it.
                         */
                        *uid = resp->u_res.uid;
                        nfs_idmap_cache_s2i_insert(&nig->s2u_ci, *uid,
                            u8s, HQ_HASH_HINT, hashno);
                        break;

                case NFSMAPID_NUMSTR:
                        /*
                         * string came in as stringified id. Don't cache !
                         *
                         * nfsmapid(1m) semantics have changed in order to
                         * support diskless clients. Thus, for stringified
                         * id's that have passwd/group entries, we'll go
                         * ahead and map them, returning no error.
                         */
                        *uid = resp->u_res.uid;
                        break;

                case NFSMAPID_BADDOMAIN:
                        /*
                         * Make the offending "user@domain" string readily
                         * available to D scripts that enable the probe.
                         */
                        DTRACE_PROBE1(nfs4__str__uid, char *, mapargp->str);
                        /* FALLTHROUGH */

                case NFSMAPID_INVALID:
                case NFSMAPID_UNMAPPABLE:
                case NFSMAPID_INTERNAL:
                case NFSMAPID_BADID:
                case NFSMAPID_NOTFOUND:
                default:
                        /*
                         * For now, treat all of these errors as equal.
                         *
                         * Return error on the server side, then the
                         * server returns NFS4_BADOWNER to the client.
                         * On client side, just map to UID_NOBODY.
                         */
                        if (isserver)
                                error = EPERM;
                        else
                                *uid = UID_NOBODY;
                        break;
                }
                kmem_free(mapargp, MAPID_ARG_LEN(u8s->utf8string_len));
                if (resp != mapresp)
                        kmem_free(door_args.rbuf, door_args.rsize);
                door_ki_rele(dh);
                return (error);
        }

        kmem_free(mapargp, MAPID_ARG_LEN(u8s->utf8string_len));
        /*
         * We got some door error
         */
        switch (error) {
        case EINTR:
                /*
                 * If we took an interrupt we have to bail out.
                 */
                if (ttolwp(curthread) && ISSIG(curthread, JUSTLOOKING)) {
                        door_ki_rele(dh);
                        return (EINTR);
                }

                /*
                 * We may have gotten EINTR for other reasons like the
                 * door being revoked on us, instead of trying to
                 * extract this out of the door handle, sleep
                 * and try again, if still revoked we will get EBADF
                 * next time through.
                 */
                /* FALLTHROUGH */
        case EAGAIN:    /* process may be forking */
                door_ki_rele(dh);
                /*
                 * Back off for a bit
                 */
                ddi_sleep(1);
                goto retry;
        default:        /* Unknown must be fatal */
        case EBADF:     /* Invalid door */
        case EINVAL:    /* Not a door, wrong target */
                /*
                 * A fatal door error, if our failing door handle is the
                 * current door handle, clean up our state and
                 * mark the server dead.
                 */
                mutex_enter(&nig->nfsidmap_daemon_lock);
                if (dh == nig->nfsidmap_daemon_dh) {
                        door_ki_rele(nig->nfsidmap_daemon_dh);
                        nig->nfsidmap_daemon_dh = NULL;
                }
                mutex_exit(&nig->nfsidmap_daemon_lock);
                door_ki_rele(dh);

                if (isserver)
                        return (ECOMM);

                /*
                 * Note: We've already done optimizations above to check
                 *       for '@' sign, so if we can't comm w/nfsmapid, we
                 *       _know_ this _can't_ be a stringified uid.
                 */
                if (!nig->nig_msg_done) {
                        zcmn_err(getzoneid(), CE_WARN,
                            "!%s: Can't communicate with mapping daemon "
                            "nfsmapid", whoami);

                        nig->nig_msg_done = 1;
                }
                *uid = UID_NOBODY;
                return (0);
        }
        /* NOTREACHED */
}

/*
 * Convert a uid into its utf-8 string representation.
 */
int
nfs_idmap_uid_str(uid_t uid, utf8string *u8s, bool_t isserver)
{
        int                     error;
        uint_t                  hashno = 0;
        const char              *whoami = "nfs_idmap_uid_str";
        struct nfsidmap_globals *nig;
        struct mapid_arg        maparg;
        struct mapid_res        mapres;
        struct mapid_res        *mapresp = &mapres;
        struct mapid_res        *resp = mapresp;
        door_arg_t              door_args;
        door_handle_t           dh;

        nig = zone_getspecific(nfsidmap_zone_key, nfs_zone());
        ASSERT(nig != NULL);

        /*
         * If the supplied uid is "nobody", then we don't look at the
         * cache, since we DON'T cache it in the u2s_cache. We cannot
         * tell two strings apart from caching the same uid.
         */
        if (uid == UID_NOBODY) {
                (void) str_to_utf8("nobody", u8s);
                return (0);
        }

        /*
         * Start-off with upcalls disabled, and once nfsmapid(1m) is
         * up and running, we'll leverage it's first flush to let the
         * kernel know when it's up and available to perform mappings.
         * We fall back to answering with stringified uid's.
         */
retry:
        mutex_enter(&nig->nfsidmap_daemon_lock);
        dh = nig->nfsidmap_daemon_dh;
        if (dh)
                door_ki_hold(dh);
        mutex_exit(&nig->nfsidmap_daemon_lock);

        if (dh == NULL || nig->nfsidmap_pid == curproc->p_pid) {
                if (dh)
                        door_ki_rele(dh);
                nfs_idmap_i2s_literal(uid, u8s);
                return (0);
        }

        /* cache hit */
        if (nfs_idmap_cache_i2s_lkup(&nig->u2s_ci, uid, &hashno, u8s)) {
                door_ki_rele(dh);
                return (0);
        }

        /* cache miss */
        maparg.cmd = NFSMAPID_UID_STR;
        maparg.u_arg.uid = uid;

        door_args.data_ptr = (char *)&maparg;
        door_args.data_size = sizeof (struct mapid_arg);
        door_args.desc_ptr = NULL;
        door_args.desc_num = 0;
        door_args.rbuf = (char *)mapresp;
        door_args.rsize = sizeof (struct mapid_res);

        error = door_ki_upcall_limited(dh, &door_args, NULL, SIZE_MAX, 0);
        if (!error) {
                resp = (struct mapid_res *)door_args.rbuf;

                /* Should never provide daemon with bad args */
                ASSERT(resp->status != NFSMAPID_INVALID);

                switch (resp->status) {
                case NFSMAPID_OK:
                        /*
                         * We now have a valid result from the
                         * user-land daemon, so cache the result (if need be).
                         * Load return value first then do the caches.
                         */
                        (void) str_to_utf8(resp->str, u8s);
                        nfs_idmap_cache_i2s_insert(&nig->u2s_ci, uid,
                            u8s, HQ_HASH_HINT, hashno);
                        break;

                case NFSMAPID_INVALID:
                case NFSMAPID_UNMAPPABLE:
                case NFSMAPID_INTERNAL:
                case NFSMAPID_BADDOMAIN:
                case NFSMAPID_BADID:
                case NFSMAPID_NOTFOUND:
                default:
                        /*
                         * For now, treat all of these errors as equal.
                         */
                        error = EPERM;
                        break;
                }

                if (resp != mapresp)
                        kmem_free(door_args.rbuf, door_args.rsize);
                door_ki_rele(dh);
                return (error);
        }

        /*
         * We got some door error
         */
        switch (error) {
        case EINTR:
                /*
                 * If we took an interrupt we have to bail out.
                 */
                if (ttolwp(curthread) && ISSIG(curthread, JUSTLOOKING)) {
                        door_ki_rele(dh);
                        return (EINTR);
                }

                /*
                 * We may have gotten EINTR for other reasons like the
                 * door being revoked on us, instead of trying to
                 * extract this out of the door handle, sleep
                 * and try again, if still revoked we will get EBADF
                 * next time through.
                 */
                /* FALLTHROUGH */
        case EAGAIN:    /* process may be forking */
                door_ki_rele(dh);
                /*
                 * Back off for a bit
                 */
                ddi_sleep(1);
                goto retry;
        default:        /* Unknown must be fatal */
        case EBADF:     /* Invalid door */
        case EINVAL:    /* Not a door, wrong target */
                /*
                 * A fatal door error, if our failing door handle is the
                 * current door handle, clean up our state and
                 * mark the server dead.
                 */
                mutex_enter(&nig->nfsidmap_daemon_lock);
                if (dh == nig->nfsidmap_daemon_dh) {
                        door_ki_rele(nig->nfsidmap_daemon_dh);
                        nig->nfsidmap_daemon_dh = NULL;
                }
                mutex_exit(&nig->nfsidmap_daemon_lock);
                door_ki_rele(dh);

                /*
                 * Log error on client-side only
                 */
                if (!nig->nig_msg_done && !isserver) {
                        zcmn_err(getzoneid(), CE_WARN,
                            "!%s: Can't communicate with mapping daemon "
                            "nfsmapid", whoami);

                        nig->nig_msg_done = 1;
                }
                nfs_idmap_i2s_literal(uid, u8s);
                return (0);
        }
        /* NOTREACHED */
}

/*
 * Convert a group utf-8 string identifier into its local gid.
 */
int
nfs_idmap_str_gid(utf8string *u8s, gid_t *gid, bool_t isserver)
{
        int                     error;
        uint_t                  hashno = 0;
        const char              *whoami = "nfs_idmap_str_gid";
        struct nfsidmap_globals *nig;
        struct mapid_arg        *mapargp;
        struct mapid_res        mapres;
        struct mapid_res        *mapresp = &mapres;
        struct mapid_res        *resp = mapresp;
        door_arg_t              door_args;
        door_handle_t           dh;

        nig = zone_getspecific(nfsidmap_zone_key, nfs_zone());
        ASSERT(nig != NULL);

        if (!u8s || !u8s->utf8string_val || u8s->utf8string_len == 0 ||
            (u8s->utf8string_val[0] == '\0')) {
                *gid = GID_NOBODY;
                return (isserver ? EINVAL : 0);
        }

        /*
         * If "nobody", just short circuit and bail
         */
        if (bcmp(u8s->utf8string_val, "nobody", 6) == 0) {
                *gid = GID_NOBODY;
                return (0);
        }

        /*
         * Start-off with upcalls disabled, and once nfsmapid(1m) is up and
         * running, we'll leverage it's first flush to let the kernel know
         * when it's up and available to perform mappings. Also, on client
         * only, be smarter about when to issue upcalls by checking the
         * string for existence of an '@' sign. If no '@' sign, then we just
         * make our best effort to decode the string ourselves.
         */
retry:
        mutex_enter(&nig->nfsidmap_daemon_lock);
        dh = nig->nfsidmap_daemon_dh;
        if (dh)
                door_ki_hold(dh);
        mutex_exit(&nig->nfsidmap_daemon_lock);

        if (dh == NULL || nig->nfsidmap_pid == curproc->p_pid ||
            (!utf8_strchr(u8s, '@') && !isserver)) {
                if (dh)
                        door_ki_rele(dh);
                error = nfs_idmap_s2i_literal(u8s, gid, isserver);
                /*
                 * If we get a numeric value, but we only do so because
                 * we are nfsmapid, return ENOTSUP to indicate a valid
                 * response, but not to cache it.
                 */
                if (!error && nig->nfsidmap_pid == curproc->p_pid)
                        return (ENOTSUP);
                return (error);
        }

        /* cache hit */
        if (nfs_idmap_cache_s2i_lkup(&nig->s2g_ci, u8s, &hashno, gid)) {
                door_ki_rele(dh);
                return (0);
        }

        /* cache miss */
        mapargp = kmem_alloc(MAPID_ARG_LEN(u8s->utf8string_len), KM_SLEEP);
        mapargp->cmd = NFSMAPID_STR_GID;
        mapargp->u_arg.len = u8s->utf8string_len;
        (void) bcopy(u8s->utf8string_val, mapargp->str, mapargp->u_arg.len);
        mapargp->str[mapargp->u_arg.len] = '\0';

        door_args.data_ptr = (char *)mapargp;
        door_args.data_size = MAPID_ARG_LEN(mapargp->u_arg.len);
        door_args.desc_ptr = NULL;
        door_args.desc_num = 0;
        door_args.rbuf = (char *)mapresp;
        door_args.rsize = sizeof (struct mapid_res);

        error = door_ki_upcall_limited(dh, &door_args, NULL, SIZE_MAX, 0);
        if (!error) {
                resp = (struct mapid_res *)door_args.rbuf;

                /* Should never provide daemon with bad args */
                ASSERT(resp->status != NFSMAPID_INVALID);

                switch (resp->status) {
                case NFSMAPID_OK:
                        /*
                         * Valid mapping. Cache it.
                         */
                        *gid = resp->u_res.gid;
                        error = 0;
                        nfs_idmap_cache_s2i_insert(&nig->s2g_ci, *gid,
                            u8s, HQ_HASH_HINT, hashno);
                        break;

                case NFSMAPID_NUMSTR:
                        /*
                         * string came in as stringified id. Don't cache !
                         *
                         * nfsmapid(1m) semantics have changed in order to
                         * support diskless clients. Thus, for stringified
                         * id's that have passwd/group entries, we'll go
                         * ahead and map them, returning no error.
                         */
                        *gid = resp->u_res.gid;
                        break;

                case NFSMAPID_BADDOMAIN:
                        /*
                         * Make the offending "group@domain" string readily
                         * available to D scripts that enable the probe.
                         */
                        DTRACE_PROBE1(nfs4__str__gid, char *, mapargp->str);
                        /* FALLTHROUGH */

                case NFSMAPID_INVALID:
                case NFSMAPID_UNMAPPABLE:
                case NFSMAPID_INTERNAL:
                case NFSMAPID_BADID:
                case NFSMAPID_NOTFOUND:
                default:
                        /*
                         * For now, treat all of these errors as equal.
                         *
                         * Return error on the server side, then the
                         * server returns NFS4_BADOWNER to the client.
                         * On client side, just map to GID_NOBODY.
                         */
                        if (isserver)
                                error = EPERM;
                        else
                                *gid = GID_NOBODY;
                        break;
                }
                kmem_free(mapargp, MAPID_ARG_LEN(u8s->utf8string_len));
                if (resp != mapresp)
                        kmem_free(door_args.rbuf, door_args.rsize);
                door_ki_rele(dh);
                return (error);
        }

        kmem_free(mapargp, MAPID_ARG_LEN(u8s->utf8string_len));
        /*
         * We got some door error
         */
        switch (error) {
        case EINTR:
                /*
                 * If we took an interrupt we have to bail out.
                 */
                if (ttolwp(curthread) && ISSIG(curthread, JUSTLOOKING)) {
                        door_ki_rele(dh);
                        return (EINTR);
                }

                /*
                 * We may have gotten EINTR for other reasons like the
                 * door being revoked on us, instead of trying to
                 * extract this out of the door handle, sleep
                 * and try again, if still revoked we will get EBADF
                 * next time through.
                 */
                /* FALLTHROUGH */
        case EAGAIN:    /* process may be forking */
                door_ki_rele(dh);
                /*
                 * Back off for a bit
                 */
                ddi_sleep(1);
                goto retry;
        default:        /* Unknown must be fatal */
        case EBADF:     /* Invalid door */
        case EINVAL:    /* Not a door, wrong target */
                /*
                 * A fatal door error, clean up our state and
                 * mark the server dead.
                 */

                mutex_enter(&nig->nfsidmap_daemon_lock);
                if (dh == nig->nfsidmap_daemon_dh) {
                        door_ki_rele(nig->nfsidmap_daemon_dh);
                        nig->nfsidmap_daemon_dh = NULL;
                }
                mutex_exit(&nig->nfsidmap_daemon_lock);
                door_ki_rele(dh);

                if (isserver)
                        return (ECOMM);

                /*
                 * Note: We've already done optimizations above to check
                 *       for '@' sign, so if we can't comm w/nfsmapid, we
                 *       _know_ this _can't_ be a stringified gid.
                 */
                if (!nig->nig_msg_done) {
                        zcmn_err(getzoneid(), CE_WARN,
                            "!%s: Can't communicate with mapping daemon "
                            "nfsmapid", whoami);

                        nig->nig_msg_done = 1;
                }
                *gid = GID_NOBODY;
                return (0);
        }
        /* NOTREACHED */
}

/*
 * Convert a gid into its utf-8 string representation.
 */
int
nfs_idmap_gid_str(gid_t gid, utf8string *u8s, bool_t isserver)
{
        int                     error;
        uint_t                  hashno = 0;
        const char              *whoami = "nfs_idmap_gid_str";
        struct nfsidmap_globals *nig;
        struct mapid_arg        maparg;
        struct mapid_res        mapres;
        struct mapid_res        *mapresp = &mapres;
        struct mapid_res        *resp = mapresp;
        door_arg_t              door_args;
        door_handle_t           dh;

        nig = zone_getspecific(nfsidmap_zone_key, nfs_zone());
        ASSERT(nig != NULL);

        /*
         * If the supplied gid is "nobody", then we don't look at the
         * cache, since we DON'T cache it in the u2s_cache. We cannot
         * tell two strings apart from caching the same gid.
         */
        if (gid == GID_NOBODY) {
                (void) str_to_utf8("nobody", u8s);
                return (0);
        }

        /*
         * Start-off with upcalls disabled, and once nfsmapid(1m) is
         * up and running, we'll leverage it's first flush to let the
         * kernel know when it's up and available to perform mappings.
         * We fall back to answering with stringified gid's.
         */
retry:
        mutex_enter(&nig->nfsidmap_daemon_lock);
        dh = nig->nfsidmap_daemon_dh;
        if (dh)
                door_ki_hold(dh);
        mutex_exit(&nig->nfsidmap_daemon_lock);

        if (dh == NULL || nig->nfsidmap_pid == curproc->p_pid) {
                if (dh)
                        door_ki_rele(dh);
                nfs_idmap_i2s_literal(gid, u8s);
                return (0);
        }

        /* cache hit */
        if (nfs_idmap_cache_i2s_lkup(&nig->g2s_ci, gid, &hashno, u8s)) {
                door_ki_rele(dh);
                return (0);
        }

        /* cache miss */
        maparg.cmd = NFSMAPID_GID_STR;
        maparg.u_arg.gid = gid;

        door_args.data_ptr = (char *)&maparg;
        door_args.data_size = sizeof (struct mapid_arg);
        door_args.desc_ptr = NULL;
        door_args.desc_num = 0;
        door_args.rbuf = (char *)mapresp;
        door_args.rsize = sizeof (struct mapid_res);

        error = door_ki_upcall_limited(dh, &door_args, NULL, SIZE_MAX, 0);
        if (!error) {
                resp = (struct mapid_res *)door_args.rbuf;

                /* Should never provide daemon with bad args */
                ASSERT(resp->status != NFSMAPID_INVALID);

                switch (resp->status) {
                case NFSMAPID_OK:
                        /*
                         * We now have a valid result from the
                         * user-land daemon, so cache the result (if need be).
                         * Load return value first then do the caches.
                         */
                        (void) str_to_utf8(resp->str, u8s);
                        nfs_idmap_cache_i2s_insert(&nig->g2s_ci, gid,
                            u8s, HQ_HASH_HINT, hashno);
                        break;

                case NFSMAPID_INVALID:
                case NFSMAPID_UNMAPPABLE:
                case NFSMAPID_INTERNAL:
                case NFSMAPID_BADDOMAIN:
                case NFSMAPID_BADID:
                case NFSMAPID_NOTFOUND:
                default:
                        /*
                         * For now, treat all of these errors as equal.
                         */
                        error = EPERM;
                        break;
                }

                if (resp != mapresp)
                        kmem_free(door_args.rbuf, door_args.rsize);
                door_ki_rele(dh);
                return (error);
        }

        /*
         * We got some door error
         */
        switch (error) {
        case EINTR:
                /*
                 * If we took an interrupt we have to bail out.
                 */
                if (ttolwp(curthread) && ISSIG(curthread, JUSTLOOKING)) {
                        door_ki_rele(dh);
                        return (EINTR);
                }

                /*
                 * We may have gotten EINTR for other reasons like the
                 * door being revoked on us, instead of trying to
                 * extract this out of the door handle, sleep
                 * and try again, if still revoked we will get EBADF
                 * next time through.
                 */
                /* FALLTHROUGH */
        case EAGAIN:    /* process may be forking */
                door_ki_rele(dh);
                /*
                 * Back off for a bit
                 */
                ddi_sleep(1);
                goto retry;
        default:        /* Unknown must be fatal */
        case EBADF:     /* Invalid door */
        case EINVAL:    /* Not a door, wrong target */
                /*
                 * A fatal door error, if our failing door handle is the
                 * current door handle, clean up our state and
                 * mark the server dead.
                 */
                mutex_enter(&nig->nfsidmap_daemon_lock);
                if (dh == nig->nfsidmap_daemon_dh) {
                        door_ki_rele(nig->nfsidmap_daemon_dh);
                        nig->nfsidmap_daemon_dh = NULL;
                }
                door_ki_rele(dh);
                mutex_exit(&nig->nfsidmap_daemon_lock);

                /*
                 * Log error on client-side only
                 */
                if (!nig->nig_msg_done && !isserver) {
                        zcmn_err(getzoneid(), CE_WARN,
                            "!%s: Can't communicate with mapping daemon "
                            "nfsmapid", whoami);

                        nig->nig_msg_done = 1;
                }
                nfs_idmap_i2s_literal(gid, u8s);
                return (0);
        }
        /* NOTREACHED */
}

/* -- idmap cache management -- */

/*
 * Cache creation and initialization routine
 */
static void
nfs_idmap_cache_create(idmap_cache_info_t *cip, const char *name)
{
        int              i;
        nfsidhq_t       *hq = NULL;

        cip->table = kmem_alloc((NFSID_CACHE_ANCHORS * sizeof (nfsidhq_t)),
            KM_SLEEP);

        for (i = 0, hq = cip->table; i < NFSID_CACHE_ANCHORS; i++, hq++) {
                hq->hq_que_forw = hq;
                hq->hq_que_back = hq;
                mutex_init(&(hq->hq_lock), NULL, MUTEX_DEFAULT, NULL);
        }
        cip->name = name;
}

/*
 * Cache destruction routine
 *
 * Ops per hash queue
 *
 * - dequeue cache entries
 * - release string storage per entry
 * - release cache entry storage
 * - destroy HQ lock when HQ is empty
 * - once all HQ's empty, release HQ storage
 */
static void
nfs_idmap_cache_destroy(idmap_cache_info_t *cip)
{
        int              i;
        nfsidhq_t       *hq;

        ASSERT(MUTEX_HELD(&nfsidmap_globals_lock));
        nfs_idmap_cache_flush(cip);
        /*
         * We can safely destroy per-queue locks since the only
         * other entity that could be mucking with this table is the
         * kmem reaper thread which does everything under
         * nfsidmap_globals_lock (which we're holding).
         */
        for (i = 0, hq = cip->table; i < NFSID_CACHE_ANCHORS; i++, hq++)
                mutex_destroy(&(hq->hq_lock));
        kmem_free(cip->table, NFSID_CACHE_ANCHORS * sizeof (nfsidhq_t));
}

void
nfs_idmap_args(struct nfsidmap_args *idmp)
{
        struct nfsidmap_globals *nig;

        nig = zone_getspecific(nfsidmap_zone_key, nfs_zone());
        ASSERT(nig != NULL);

        nfs_idmap_cache_flush(&nig->u2s_ci);
        nfs_idmap_cache_flush(&nig->s2u_ci);
        nfs_idmap_cache_flush(&nig->g2s_ci);
        nfs_idmap_cache_flush(&nig->s2g_ci);

        /*
         * nfsmapid(1m) up and running; enable upcalls
         * State:
         *      0       Just flush caches
         *      1       Re-establish door knob
         */
        if (idmp->state) {
                /*
                 * When reestablishing the nfsmapid we need to
                 * not only purge the idmap cache but also
                 * the dnlc as it will have cached uid/gid's.
                 * While heavyweight, this should almost never happen
                 */
                dnlc_purge();

                /*
                 * Invalidate the attrs of all rnodes to force new uid and gids
                 */
                nfs4_rnode_invalidate(NULL);

                mutex_enter(&nig->nfsidmap_daemon_lock);
                if (nig->nfsidmap_daemon_dh)
                        door_ki_rele(nig->nfsidmap_daemon_dh);
                nig->nfsidmap_daemon_dh = door_ki_lookup(idmp->did);
                nig->nfsidmap_pid = curproc->p_pid;
                nig->nig_msg_done = 0;
                mutex_exit(&nig->nfsidmap_daemon_lock);
        }
}

/*
 * Cache flush routine
 *
 *      The only serialization required it to hold the hash chain lock
 *      when destroying cache entries.  There is no need to prevent access
 *      to all hash chains while flushing.  It is possible that (valid)
 *      entries could be cached in later hash chains after we start flushing.
 *      It is unfortunate that the entry will be instantly destroyed, but
 *      it isn't a major concern.  This is only a cache.  It'll be repopulated.
 *
 * Ops per hash queue
 *
 * - dequeue cache entries
 * - release string storage per entry
 * - release cache entry storage
 */
static void
nfs_idmap_cache_flush(idmap_cache_info_t *cip)
{
        int              i;
        nfsidmap_t      *p, *next;
        nfsidhq_t       *hq;

        for (i = 0, hq = cip->table; i < NFSID_CACHE_ANCHORS; i++, hq++) {

                mutex_enter(&(hq->hq_lock));

                /*
                 * remove list from hash header so we can release
                 * the lock early.
                 */
                p = hq->hq_lru_forw;
                hq->hq_que_forw = hq;
                hq->hq_que_back = hq;

                mutex_exit(&(hq->hq_lock));

                /*
                 * Iterate over the orphan'd list and free all elements.
                 * There's no need to bother with remque since we're
                 * freeing the entire list.
                 */
                while (p != (nfsidmap_t *)hq) {
                        next = p->id_forw;
                        if (p->id_val != 0)
                                kmem_free(p->id_val, p->id_len);
                        kmem_cache_free(nfsidmap_cache, p);
                        p = next;
                }

        }
}

static void
nfs_idmap_cache_reclaim(idmap_cache_info_t *cip)
{
        nfsidhq_t               *hq;
        nfsidmap_t              *pprev = NULL;
        int                      i;
        nfsidmap_t              *p;

        ASSERT(cip != NULL && cip->table != NULL);

        /*
         * If the daemon is down, do not flush anything
         */
        if ((*cip->nfsidmap_daemon_dh) == NULL)
                return;

        for (i = 0, hq = cip->table; i < NFSID_CACHE_ANCHORS; i++, hq++) {
                if (!mutex_tryenter(&(hq->hq_lock)))
                        continue;

                /*
                 * Start at end of list and work backwards since LRU
                 */
                for (p = hq->hq_lru_back; p != (nfsidmap_t *)hq; p = pprev) {
                        pprev = p->id_back;

                        /*
                         * List is LRU. If trailing end does not
                         * contain stale entries, then no need to
                         * continue.
                         */
                        if (!TIMEOUT(p->id_time))
                                break;

                        nfs_idmap_cache_rment(p);
                }
                mutex_exit(&(hq->hq_lock));
        }
}

/*
 * Callback reclaim function for VM.  We reap timed-out entries from all hash
 * tables in all zones.
 */
/* ARGSUSED */
void
nfs_idmap_reclaim(void *arg)
{
        struct nfsidmap_globals *nig;

        mutex_enter(&nfsidmap_globals_lock);
        for (nig = list_head(&nfsidmap_globals_list); nig != NULL;
            nig = list_next(&nfsidmap_globals_list, nig)) {
                nfs_idmap_cache_reclaim(&nig->u2s_ci);
                nfs_idmap_cache_reclaim(&nig->s2u_ci);
                nfs_idmap_cache_reclaim(&nig->g2s_ci);
                nfs_idmap_cache_reclaim(&nig->s2g_ci);
        }
        mutex_exit(&nfsidmap_globals_lock);
}

/*
 * Search the specified cache for the existence of the specified utf-8
 * string. If found, the corresponding mapping is returned in id_buf and
 * the cache entry is updated to the head of the LRU list. The computed
 * hash queue number, is returned in hashno.
 *
 * cip    - cache info ptr
 * u8s    - utf8 string to resolve
 * hashno - hash number, retval
 * id_buf - if found, id for u8s
 */
static uint_t
nfs_idmap_cache_s2i_lkup(idmap_cache_info_t *cip, utf8string *u8s,
    uint_t *hashno, uid_t *id_buf)
{
        nfsidmap_t      *p;
        nfsidmap_t      *pnext;
        nfsidhq_t       *hq;
        char            *rqst_c_str;
        uint_t           rqst_len;
        uint_t           found_stat = 0;

        if ((rqst_c_str = utf8_to_str(u8s, &rqst_len, NULL)) == NULL) {
                /*
                 * Illegal string, return not found.
                 */
                return (0);
        }

        /*
         * Compute hash queue
         */
        *hashno = pkp_tab_hash(rqst_c_str, rqst_len - 1);
        hq = &cip->table[*hashno];

        /*
         * Look for the entry in the HQ
         */
        mutex_enter(&(hq->hq_lock));
        for (p = hq->hq_lru_forw; p != (nfsidmap_t *)hq; p = pnext) {

                pnext = p->id_forw;

                /*
                 * Check entry for staleness first, as user's id
                 * may have changed and may need to be remapped.
                 * Note that we don't evict entries from the cache
                 * if we're having trouble contacting nfsmapid(1m)
                 */
                if (TIMEOUT(p->id_time) && (*cip->nfsidmap_daemon_dh) != NULL) {
                        nfs_idmap_cache_rment(p);
                        continue;
                }

                /*
                 * Compare equal length strings
                 */
                if (p->id_len == (rqst_len - 1)) {
                        if (bcmp(p->id_val, rqst_c_str, (rqst_len - 1)) == 0) {
                                /*
                                 * Found it. Update it and load return value.
                                 */
                                *id_buf = p->id_no;
                                remque(p);
                                insque(p, hq);
                                p->id_time = gethrestime_sec();

                                found_stat = 1;
                                break;
                        }
                }
        }
        mutex_exit(&(hq->hq_lock));

        if (rqst_c_str != NULL)
                kmem_free(rqst_c_str, rqst_len);

        return (found_stat);
}

/*
 * Search the specified cache for the existence of the specified utf8
 * string, as it may have been inserted before this instance got a chance
 * to do it. If NOT found, then a new entry is allocated for the specified
 * cache, and inserted. The hash queue number is obtained from hash_number
 * if the behavior is HQ_HASH_HINT, or computed otherwise.
 *
 * cip         - cache info ptr
 * id          - id result from upcall
 * u8s         - utf8 string to resolve
 * behavior    - hash algorithm behavior
 * hash_number - hash number iff hint
 */
static void
nfs_idmap_cache_s2i_insert(idmap_cache_info_t *cip, uid_t id, utf8string *u8s,
    hash_stat behavior, uint_t hash_number)
{
        uint_t                   hashno;
        char                    *c_str;
        nfsidhq_t               *hq;
        nfsidmap_t              *newp;
        nfsidmap_t              *p;
        nfsidmap_t              *pnext;
        uint_t                   c_len;

        /*
         * This shouldn't fail, since already successful at lkup.
         * So, if it does happen, just drop the request-to-insert
         * on the floor.
         */
        if ((c_str = utf8_to_str(u8s, &c_len, NULL)) == NULL)
                return;

        /*
         * Obtain correct hash queue to insert new entry in
         */
        switch (behavior) {
                case HQ_HASH_HINT:
                        hashno = hash_number;
                        break;

                case HQ_HASH_FIND:
                default:
                        hashno = pkp_tab_hash(c_str, c_len - 1);
                        break;
        }
        hq = &cip->table[hashno];


        /*
         * Look for an existing entry in the cache. If one exists
         * update it, and return. Otherwise, allocate a new cache
         * entry, initialize it and insert it.
         */
        mutex_enter(&(hq->hq_lock));
        for (p = hq->hq_lru_forw; p != (nfsidmap_t *)hq; p = pnext) {

                pnext = p->id_forw;

                /*
                 * Check entry for staleness first, as user's id
                 * may have changed and may need to be remapped.
                 * Note that we don't evict entries from the cache
                 * if we're having trouble contacting nfsmapid(1m)
                 */
                if (TIMEOUT(p->id_time) && (*cip->nfsidmap_daemon_dh) != NULL) {
                        nfs_idmap_cache_rment(p);
                        continue;
                }

                /*
                 * Compare equal length strings
                 */
                if (p->id_len == (c_len - 1)) {
                        if (bcmp(p->id_val, c_str, (c_len - 1)) == 0) {
                                /*
                                 * Move to front, and update time.
                                 */
                                remque(p);
                                insque(p, hq);
                                p->id_time = gethrestime_sec();

                                mutex_exit(&(hq->hq_lock));
                                kmem_free(c_str, c_len);
                                return;
                        }
                }
        }

        /*
         * Not found ! Alloc, init and insert new entry
         */
        newp = kmem_cache_alloc(nfsidmap_cache, KM_SLEEP);
        newp->id_len = u8s->utf8string_len;
        newp->id_val = kmem_alloc(u8s->utf8string_len, KM_SLEEP);
        bcopy(u8s->utf8string_val, newp->id_val, u8s->utf8string_len);
        newp->id_no = id;
        newp->id_time = gethrestime_sec();
        insque(newp, hq);

        mutex_exit(&(hq->hq_lock));
        kmem_free(c_str, c_len);
}

/*
 * Search the specified cache for the existence of the specified id.
 * If found, the corresponding mapping is returned in u8s and the
 * cache entry is updated to the head of the LRU list. The computed
 * hash queue number, is returned in hashno.
 *
 * cip    - cache info ptr
 * id     - id to resolve
 * hashno - hash number, retval
 * u8s    - if found, utf8 str for id
 */
static uint_t
nfs_idmap_cache_i2s_lkup(idmap_cache_info_t *cip, uid_t id, uint_t *hashno,
    utf8string *u8s)
{
        uint_t                   found_stat = 0;
        nfsidmap_t              *p;
        nfsidmap_t              *pnext;
        nfsidhq_t               *hq;
        uint_t                   hash;

        /*
         * Compute hash queue
         */
        ID_HASH(id, hash);
        *hashno = hash;
        hq = &cip->table[hash];

        /*
         * Look for the entry in the HQ
         */
        mutex_enter(&(hq->hq_lock));
        for (p = hq->hq_lru_forw; p != (nfsidmap_t *)hq; p = pnext) {

                pnext = p->id_forw;

                /*
                 * Check entry for staleness first, as user's id
                 * may have changed and may need to be remapped.
                 * Note that we don't evict entries from the cache
                 * if we're having trouble contacting nfsmapid(1m)
                 */
                if (TIMEOUT(p->id_time) && (*cip->nfsidmap_daemon_dh) != NULL) {
                        nfs_idmap_cache_rment(p);
                        continue;
                }

                if (p->id_no == id) {

                        /*
                         * Found it. Load return value and move to head
                         */
                        ASSERT(u8s->utf8string_val == NULL);
                        u8s->utf8string_len = p->id_len;
                        u8s->utf8string_val = kmem_alloc(p->id_len, KM_SLEEP);
                        bcopy(p->id_val, u8s->utf8string_val, p->id_len);

                        remque(p);
                        insque(p, hq);
                        p->id_time = gethrestime_sec();

                        found_stat = 1;
                        break;
                }
        }
        mutex_exit(&(hq->hq_lock));

        return (found_stat);
}

/*
 * Search the specified cache for the existence of the specified id,
 * as it may have been inserted before this instance got a chance to
 * do it. If NOT found, then a new entry is allocated for the specified
 * cache, and inserted. The hash queue number is obtained from hash_number
 * if the behavior is HQ_HASH_HINT, or computed otherwise.
 *
 * cip         - cache info ptr
 * id          - id to resolve
 * u8s         - utf8 result from upcall
 * behavior    - has algorithm behavior
 * hash_number - hash number iff hint
 */
static void
nfs_idmap_cache_i2s_insert(idmap_cache_info_t *cip, uid_t id, utf8string *u8s,
    hash_stat behavior, uint_t hash_number)
{
        uint_t           hashno;
        nfsidhq_t       *hq;
        nfsidmap_t      *newp;
        nfsidmap_t      *pnext;
        nfsidmap_t      *p;


        /*
         * Obtain correct hash queue to insert new entry in
         */
        switch (behavior) {
                case HQ_HASH_HINT:
                        hashno = hash_number;
                        break;

                case HQ_HASH_FIND:
                default:
                        ID_HASH(id, hashno);
                        break;
        }
        hq = &cip->table[hashno];


        /*
         * Look for an existing entry in the cache. If one exists
         * update it, and return. Otherwise, allocate a new cache
         * entry, initialize and insert it.
         */
        mutex_enter(&(hq->hq_lock));
        for (p = hq->hq_lru_forw; p != (nfsidmap_t *)hq; p = pnext) {

                pnext = p->id_forw;

                /*
                 * Check entry for staleness first, as user's id
                 * may have changed and may need to be remapped.
                 * Note that we don't evict entries from the cache
                 * if we're having trouble contacting nfsmapid(1m)
                 */
                if (TIMEOUT(p->id_time) && (*cip->nfsidmap_daemon_dh) != NULL) {
                        nfs_idmap_cache_rment(p);
                        continue;
                }


                if ((p->id_no == id) && (p->id_len == u8s->utf8string_len)) {
                        /*
                         * Found It ! Move to front, and update time.
                         */
                        remque(p);
                        insque(p, hq);
                        p->id_time = gethrestime_sec();

                        mutex_exit(&(hq->hq_lock));
                        return;
                }
        }

        /*
         * Not found ! Alloc, init and insert new entry
         */
        newp = kmem_cache_alloc(nfsidmap_cache, KM_SLEEP);
        newp->id_len = u8s->utf8string_len;
        newp->id_val = kmem_alloc(u8s->utf8string_len, KM_SLEEP);
        bcopy(u8s->utf8string_val, newp->id_val, u8s->utf8string_len);
        newp->id_no = id;
        newp->id_time = gethrestime_sec();
        insque(newp, hq);

        mutex_exit(&(hq->hq_lock));
}

/*
 * Remove and free one cache entry
 */
static void
nfs_idmap_cache_rment(nfsidmap_t *p)
{
        remque(p);
        if (p->id_val != 0)
                kmem_free(p->id_val, p->id_len);
        kmem_cache_free(nfsidmap_cache, p);
}

#ifndef         UID_MAX
#define         UID_MAX         2147483647              /* see limits.h */
#endif

#ifndef         isdigit
#define         isdigit(c)      ((c) >= '0' && (c) <= '9')
#endif

static int
is_stringified_id(utf8string *u8s)
{
        int     i;

        for (i = 0; i < u8s->utf8string_len; i++)
                if (!isdigit(u8s->utf8string_val[i]))
                        return (0);
        return (1);
}

int
nfs_idmap_s2i_literal(utf8string *u8s, uid_t *id, int isserver)
{
        long    tmp;
        int     convd;
        char    ids[_MAXIDSTRLEN];

        /*
         * "nobody" unless we can actually decode it.
         */
        *id = UID_NOBODY;

        /*
         * We're here because it has already been determined that the
         * string contains no '@' _or_ the nfsmapid daemon has yet to
         * be started.
         */
        if (!is_stringified_id(u8s))
                return (0);

        /*
         * If utf8string_len is greater than _MAXIDSTRLEN-1, then the id
         * is going to be greater than UID_MAX. Return id of "nobody"
         * right away.
         */
        if (u8s->utf8string_len >= _MAXIDSTRLEN)
                return (isserver ? EPERM : 0);

        /*
         * Make sure we pass a NULL terminated 'C' string to ddi_strtol
         */
        bcopy(u8s->utf8string_val, ids, u8s->utf8string_len);
        ids[u8s->utf8string_len] = '\0';
        convd = ddi_strtol(ids, NULL, 10, &tmp);
        if (convd == 0 && tmp >= 0 && tmp <= UID_MAX) {
                *id = tmp;
                return (0);
        }
        return (isserver ? EPERM : 0);
}

static void
nfs_idmap_i2s_literal(uid_t id, utf8string *u8s)
{
        char    ids[_MAXIDSTRLEN];

        (void) snprintf(ids, _MAXIDSTRLEN, "%d", id);
        (void) str_to_utf8(ids, u8s);
}

/* -- Utility functions -- */

char *
utf8_strchr(utf8string *u8s, const char c)
{
        int     i;
        char    *u8p = u8s->utf8string_val;
        int     len = u8s->utf8string_len;

        for (i = 0; i < len; i++)
                if (u8p[i] == c)
                        return (&u8p[i]);
        return (NULL);
}