/*      $NetBSD: nfs_export.c,v 1.63 2021/06/04 10:44:58 hannken Exp $  */

/*-
 * Copyright (c) 1997, 1998, 2004, 2005, 2008, 2019 The NetBSD Foundation, Inc.
 * All rights reserved.
 *
 * This code is derived from software contributed to The NetBSD Foundation
 * by Jason R. Thorpe of the Numerical Aerospace Simulation Facility,
 * NASA Ames Research Center.
 * This code is derived from software contributed to The NetBSD Foundation
 * by Charles M. Hannum.
 * This code is derived from software contributed to The NetBSD Foundation
 * by Julio M. Merino Vidal.
 *
 * 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.
 *
 * THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS
 * ``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 THE FOUNDATION OR CONTRIBUTORS
 * 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.
 */

/*
 * Copyright (c) 1989, 1993
 *      The Regents of the University of California.  All rights reserved.
 * (c) UNIX System Laboratories, Inc.
 * All or some portions of this file are derived from material licensed
 * to the University of California by American Telephone and Telegraph
 * Co. or Unix System Laboratories, Inc. and are reproduced herein with
 * the permission of UNIX System Laboratories, Inc.
 *
 * 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. Neither the name of the University nor the names of its contributors
 *    may be used to endorse or promote products derived from this software
 *    without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``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 THE REGENTS OR CONTRIBUTORS 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.
 *
 *      @(#)vfs_subr.c  8.13 (Berkeley) 4/18/94
 */

/*
 * VFS exports list management.
 *
 * Lock order: vfs_busy -> mnt_updating -> netexport_lock.
 */

#include <sys/cdefs.h>
__KERNEL_RCSID(0, "$NetBSD: nfs_export.c,v 1.63 2021/06/04 10:44:58 hannken Exp $");

#include <sys/param.h>
#include <sys/systm.h>
#include <sys/kernel.h>
#include <sys/queue.h>
#include <sys/proc.h>
#include <sys/mount.h>
#include <sys/vnode.h>
#include <sys/namei.h>
#include <sys/errno.h>
#include <sys/malloc.h>
#include <sys/domain.h>
#include <sys/mbuf.h>
#include <sys/dirent.h>
#include <sys/socket.h>         /* XXX for AF_MAX */
#include <sys/kauth.h>

#include <net/radix.h>

#include <netinet/in.h>

#include <nfs/rpcv2.h>
#include <nfs/nfsproto.h>
#include <nfs/nfs.h>
#include <nfs/nfs_var.h>

/*
 * Network address lookup element.
 */
struct netcred {
        struct  radix_node netc_rnodes[2];
        int     netc_refcnt;
        int     netc_exflags;
        kauth_cred_t netc_anon;
};

/*
 * Network export information.
 */
struct netexport {
        TAILQ_ENTRY(netexport) ne_list;
        struct mount *ne_mount;
        struct netcred ne_defexported;                /* Default export */
        struct radix_node_head *ne_rtable[AF_MAX+1]; /* Individual exports */
};
TAILQ_HEAD(, netexport) netexport_list =
    TAILQ_HEAD_INITIALIZER(netexport_list);

/* Publicly exported file system. */
struct nfs_public nfs_pub;

/*
 * Local prototypes.
 */
static int init_exports(struct mount *, struct netexport **);
static int hang_addrlist(struct mount *, struct netexport *,
    const struct export_args *);
static int sacheck(struct sockaddr *);
static int free_netcred(struct radix_node *, void *);
static int export(struct netexport *, const struct export_args *);
static int setpublicfs(struct mount *, struct netexport *,
    const struct export_args *);
static struct netcred *netcred_lookup(struct netexport *, struct mbuf *);
static struct netexport *netexport_lookup(const struct mount *);
static struct netexport *netexport_lookup_byfsid(const fsid_t *);
static void netexport_clear(struct netexport *);
static void netexport_insert(struct netexport *);
static void netexport_remove(struct netexport *);
static void netexport_wrlock(void);
static void netexport_wrunlock(void);
static int nfs_export_update_30(struct mount *mp, const char *path, void *);

static krwlock_t netexport_lock;

/*
 * PUBLIC INTERFACE
 */

/*
 * Declare and initialize the file system export hooks.
 */
static void netexport_unmount(struct mount *);

struct vfs_hooks nfs_export_hooks = {
        { NULL, NULL },
        .vh_unmount = netexport_unmount,
        .vh_reexport = nfs_export_update_30,
};

/*
 * VFS unmount hook for NFS exports.
 *
 * Releases NFS exports list resources if the given mount point has some.
 * As allocation happens lazily, it may be that it doesn't have this
 * information, although it theoretically should.
 */
static void
netexport_unmount(struct mount *mp)
{
        struct netexport *ne;

        KASSERT(mp != NULL);

        netexport_wrlock();
        ne = netexport_lookup(mp);
        if (ne == NULL) {
                netexport_wrunlock();
                return;
        }
        netexport_clear(ne);
        netexport_remove(ne);
        netexport_wrunlock();
        kmem_free(ne, sizeof(*ne));
}

void
netexport_init(void)
{

        rw_init(&netexport_lock);
}

void
netexport_fini(void)
{
        struct netexport *ne;
        struct mount *mp;
        int error;

        while (!TAILQ_EMPTY(&netexport_list)) {
                netexport_wrlock();
                ne = TAILQ_FIRST(&netexport_list);
                mp = ne->ne_mount;
                error = vfs_busy(mp);
                netexport_wrunlock();
                if (error != 0) {
                        kpause("nfsfini", false, hz, NULL);
                        continue;
                }
                mutex_enter(mp->mnt_updating);  /* mnt_flag */
                netexport_unmount(mp);
                mutex_exit(mp->mnt_updating);   /* mnt_flag */
                vfs_unbusy(mp);
        }
        rw_destroy(&netexport_lock);
}


/*
 * Atomically set the NFS exports list of the given file system, replacing
 * it with a new list of entries.
 *
 * Returns zero on success or an appropriate error code otherwise.
 *
 * Helper function for the nfssvc(2) system call (NFSSVC_SETEXPORTSLIST
 * and NFSSVC_REPLACEEXPORTSLIST command).
 */
int
mountd_set_exports_list(const struct mountd_exports_list *mel, struct lwp *l,
    struct mount *nmp, int cmd)
{
        int error;
        size_t i;
        struct mount *mp;
        struct netexport *ne;
        struct pathbuf *pb;
        struct nameidata nd;
        struct vnode *vp;
        size_t fid_size;

        if (kauth_authorize_network(l->l_cred, KAUTH_NETWORK_NFS,
            KAUTH_REQ_NETWORK_NFS_EXPORT, NULL, NULL, NULL) != 0)
                return EPERM;

        /* Look up the file system path. */
        error = pathbuf_copyin(mel->mel_path, &pb);
        if (error) {
                return error;
        }
        NDINIT(&nd, LOOKUP, FOLLOW | LOCKLEAF, pb);
        error = namei(&nd);
        if (error != 0) {
                pathbuf_destroy(pb);
                return error;
        }
        vp = nd.ni_vp;
        mp = vp->v_mount;
        KASSERT(nmp == NULL || nmp == mp);
        pathbuf_destroy(pb);

        /*
         * Make sure the file system can do vptofh.  If the file system
         * knows the handle's size, just trust it's able to do the
         * actual translation also (otherwise we should check fhtovp
         * also, and that's getting a wee bit ridiculous).
         */
        fid_size = 0;
        if ((error = VFS_VPTOFH(vp, NULL, &fid_size)) != E2BIG) {
                vput(vp);
                return EOPNOTSUPP;
        }

        /* Mark the file system busy. */
        error = vfs_busy(mp);
        vput(vp);
        if (error != 0)
                return error;
        if (nmp == NULL)
                mutex_enter(mp->mnt_updating);  /* mnt_flag */
        netexport_wrlock();
        ne = netexport_lookup(mp);
        if (ne == NULL) {
                error = init_exports(mp, &ne);
                if (error != 0) {
                        goto out;
                }
        }

        KASSERT(ne != NULL);
        KASSERT(ne->ne_mount == mp);

        if (cmd == NFSSVC_SETEXPORTSLIST) {
                if (mel->mel_nexports == 0)
                        netexport_clear(ne);
                else if (mel->mel_nexports == 1)
                        error = export(ne, &mel->mel_exports[0]);
                else {
                        printf("%s: Cannot set more than one "
                            "entry at once (unimplemented)\n", __func__);
                        error = EOPNOTSUPP;
                }
        } else if (cmd == NFSSVC_REPLACEEXPORTSLIST) {
                netexport_clear(ne);
                for (i = 0; error == 0 && i < mel->mel_nexports; i++)
                        error = export(ne, &mel->mel_exports[i]);
        } else {
                printf("%s: Command %#x not implemented\n", __func__, cmd);
                error = EOPNOTSUPP;
        }

out:
        netexport_wrunlock();
        if (nmp == NULL)
                mutex_exit(mp->mnt_updating);   /* mnt_flag */
        vfs_unbusy(mp);
        return error;
}

static void
netexport_insert(struct netexport *ne)
{

        TAILQ_INSERT_HEAD(&netexport_list, ne, ne_list);
}

static void
netexport_remove(struct netexport *ne)
{

        TAILQ_REMOVE(&netexport_list, ne, ne_list);
}

static struct netexport *
netexport_lookup(const struct mount *mp)
{
        struct netexport *ne;

        TAILQ_FOREACH(ne, &netexport_list, ne_list) {
                if (ne->ne_mount == mp) {
                        goto done;
                }
        }
        ne = NULL;
done:
        return ne;
}

static struct netexport *
netexport_lookup_byfsid(const fsid_t *fsid)
{
        struct netexport *ne;

        TAILQ_FOREACH(ne, &netexport_list, ne_list) {
                const struct mount *mp = ne->ne_mount;

                if (mp->mnt_stat.f_fsidx.__fsid_val[0] == fsid->__fsid_val[0] &&
                    mp->mnt_stat.f_fsidx.__fsid_val[1] == fsid->__fsid_val[1]) {
                        goto done;
                }
        }
        ne = NULL;
done:

        return ne;
}

/*
 * Check if the file system specified by the 'mp' mount structure is
 * exported to a client with 'anon' anonymous credentials.  The 'mb'
 * argument is an mbuf containing the network address of the client.
 * The return parameters for the export flags for the client are returned
 * in the address specified by 'wh'.
 *
 * This function is used exclusively by the NFS server.  It is generally
 * invoked before VFS_FHTOVP to validate that a client has access to the
 * file system.
 */

int
netexport_check(const fsid_t *fsid, struct mbuf *mb, struct mount **mpp,
    int *wh, kauth_cred_t *anon)
{
        struct netexport *ne;
        struct netcred *np;

        ne = netexport_lookup_byfsid(fsid);
        if (ne == NULL) {
                return EACCES;
        }
        np = netcred_lookup(ne, mb);
        if (np == NULL) {
                return EACCES;
        }

        *mpp = ne->ne_mount;
        *wh = np->netc_exflags;
        *anon = np->netc_anon;

        return 0;
}

/*
 * Handles legacy export requests.  In this case, the export information
 * is hardcoded in a specific place of the mount arguments structure (given
 * in data); the request for an update is given through the fspec field
 * (also in a known location), which must be a null pointer.
 *
 * Returns EJUSTRETURN if the given command was not a export request.
 * Otherwise, returns 0 on success or an appropriate error code otherwise.
 */
static int
nfs_export_update_30(struct mount *mp, const char *path, void *data)
{
        struct mountd_exports_list mel;
        struct mnt_export_args30 *args;

        args = data;
        mel.mel_path = path;

        if (args->fspec != NULL)
                return EJUSTRETURN;

        if (args->eargs.ex_flags & 0x00020000) {
                /* Request to delete exports.  The mask above holds the
                 * value that used to be in MNT_DELEXPORT. */
                mel.mel_nexports = 0;
        } else {
                /*
                 * The following code assumes export_args has not
                 * changed since export_args30, so check that.
                 */
                __CTASSERT(sizeof(args->eargs) == sizeof(*mel.mel_exports));

                mel.mel_nexports = 1;
                mel.mel_exports = (void *)&args->eargs;
        }

        return mountd_set_exports_list(&mel, curlwp, mp, NFSSVC_SETEXPORTSLIST);
}

/*
 * INTERNAL FUNCTIONS
 */

/*
 * Initializes NFS exports for the mountpoint given in 'mp'.
 * If successful, returns 0 and sets *nep to the address of the new
 * netexport item; otherwise returns an appropriate error code
 * and *nep remains unmodified.
 */
static int
init_exports(struct mount *mp, struct netexport **nep)
{
        int error;
        struct export_args ea;
        struct netexport *ne;

        KASSERT(mp != NULL);

        /* Ensure that we do not already have this mount point. */
        KASSERT(netexport_lookup(mp) == NULL);

        ne = kmem_zalloc(sizeof(*ne), KM_SLEEP);
        ne->ne_mount = mp;

        /* Set the default export entry.  Handled internally by export upon
         * first call. */
        memset(&ea, 0, sizeof(ea));
        ea.ex_root = -2;
        if (mp->mnt_flag & MNT_RDONLY)
                ea.ex_flags |= MNT_EXRDONLY;
        error = export(ne, &ea);
        if (error != 0) {
                kmem_free(ne, sizeof(*ne));
        } else {
                netexport_insert(ne);
                *nep = ne;
        }

        return error;
}

/*
 * Build hash lists of net addresses and hang them off the mount point.
 * Called by export() to set up a new entry in the lists of export
 * addresses.
 */
static int
hang_addrlist(struct mount *mp, struct netexport *nep,
    const struct export_args *argp)
{
        int error, i;
        struct netcred *np, *enp;
        struct radix_node_head *rnh;
        struct sockaddr *saddr, *smask;
        struct domain *dom;

        smask = NULL;

        if (argp->ex_addrlen == 0) {
                if (mp->mnt_flag & MNT_DEFEXPORTED)
                        return EPERM;
                np = &nep->ne_defexported;
                KASSERT(np->netc_anon == NULL);
                np->netc_anon = kauth_cred_alloc();
                np->netc_exflags = argp->ex_flags;
                kauth_uucred_to_cred(np->netc_anon, &argp->ex_anon);
                mp->mnt_flag |= MNT_DEFEXPORTED;
                return 0;
        }

        if (argp->ex_addrlen > MLEN || argp->ex_masklen > MLEN)
                return EINVAL;

        i = sizeof(struct netcred) + argp->ex_addrlen + argp->ex_masklen;
        np = malloc(i, M_NETADDR, M_WAITOK | M_ZERO);
        np->netc_anon = kauth_cred_alloc();
        saddr = (struct sockaddr *)(np + 1);
        error = copyin(argp->ex_addr, saddr, argp->ex_addrlen);
        if (error)
                goto out;
        if (saddr->sa_len > argp->ex_addrlen)
                saddr->sa_len = argp->ex_addrlen;
        if (sacheck(saddr) == -1) {
                error = EINVAL;
                goto out;
        }
        if (argp->ex_masklen) {
                smask = (struct sockaddr *)((char *)saddr + argp->ex_addrlen);
                error = copyin(argp->ex_mask, smask, argp->ex_masklen);
                if (error)
                        goto out;
                if (smask->sa_len > argp->ex_masklen)
                        smask->sa_len = argp->ex_masklen;
                if (smask->sa_family != saddr->sa_family) {
                        error = EINVAL;
                        goto out;
                }
                if (sacheck(smask) == -1) {
                        error = EINVAL;
                        goto out;
                }
        }
        i = saddr->sa_family;
        if ((rnh = nep->ne_rtable[i]) == 0) {
                /*
                 * Seems silly to initialize every AF when most are not
                 * used, do so on demand here.
                 */
                DOMAIN_FOREACH(dom) {
                        if (dom->dom_family == i && dom->dom_rtattach) {
                                rn_inithead((void **)&nep->ne_rtable[i],
                                        dom->dom_rtoffset);
                                break;
                        }
                }
                if ((rnh = nep->ne_rtable[i]) == 0) {
                        error = ENOBUFS;
                        goto out;
                }
        }

        enp = (struct netcred *)(*rnh->rnh_addaddr)(saddr, smask, rnh,
            np->netc_rnodes);
        if (enp != np) {
                if (enp == NULL) {
                        enp = (struct netcred *)(*rnh->rnh_lookup)(saddr,
                            smask, rnh);
                        if (enp == NULL) {
                                error = EPERM;
                                goto out;
                        }
                } else
                        enp->netc_refcnt++;

                goto check;
        } else
                enp->netc_refcnt = 1;

        np->netc_exflags = argp->ex_flags;
        kauth_uucred_to_cred(np->netc_anon, &argp->ex_anon);
        return 0;
check:
        if (enp->netc_exflags != argp->ex_flags ||
            kauth_cred_uucmp(enp->netc_anon, &argp->ex_anon) != 0)
                error = EPERM;
        else
                error = 0;
out:
        KASSERT(np->netc_anon != NULL);
        kauth_cred_free(np->netc_anon);
        free(np, M_NETADDR);
        return error;
}

/*
 * Ensure that the address stored in 'sa' is valid.
 * Returns zero on success, otherwise -1.
 */
static int
sacheck(struct sockaddr *sa)
{

        switch (sa->sa_family) {
        case AF_INET: {
                struct sockaddr_in *sin = (struct sockaddr_in *)sa;
                char *p = (char *)sin->sin_zero;
                size_t i;

                if (sin->sin_len != sizeof(*sin))
                        return -1;
                if (sin->sin_port != 0)
                        return -1;
                for (i = 0; i < sizeof(sin->sin_zero); i++)
                        if (*p++ != '\0')
                                return -1;
                return 0;
        }
        case AF_INET6: {
                struct sockaddr_in6 *sin6 = (struct sockaddr_in6 *)sa;

                if (sin6->sin6_len != sizeof(*sin6))
                        return -1;
                if (sin6->sin6_port != 0)
                        return -1;
                return 0;
        }
        default:
                return -1;
        }
}

/*
 * Free the netcred object pointed to by the 'rn' radix node.
 * 'w' holds a pointer to the radix tree head.
 */
static int
free_netcred(struct radix_node *rn, void *w)
{
        struct radix_node_head *rnh = (struct radix_node_head *)w;
        struct netcred *np = (struct netcred *)(void *)rn;

        (*rnh->rnh_deladdr)(rn->rn_key, rn->rn_mask, rnh);
        if (--(np->netc_refcnt) <= 0) {
                KASSERT(np->netc_anon != NULL);
                kauth_cred_free(np->netc_anon);
                free(np, M_NETADDR);
        }
        return 0;
}

/*
 * Clears the exports list for a given file system.
 */
static void
netexport_clear(struct netexport *ne)
{
        struct radix_node_head *rnh;
        struct mount *mp = ne->ne_mount;
        int i;

        if (mp->mnt_flag & MNT_EXPUBLIC) {
                setpublicfs(NULL, NULL, NULL);
                mp->mnt_flag &= ~MNT_EXPUBLIC;
        }

        for (i = 0; i <= AF_MAX; i++) {
                if ((rnh = ne->ne_rtable[i]) != NULL) {
                        rn_walktree(rnh, free_netcred, rnh);
                        free(rnh, M_RTABLE);
                        ne->ne_rtable[i] = NULL;
                }
        }

        if ((mp->mnt_flag & MNT_DEFEXPORTED) != 0) {
                struct netcred *np = &ne->ne_defexported;

                KASSERT(np->netc_anon != NULL);
                kauth_cred_free(np->netc_anon);
                np->netc_anon = NULL;
        } else {
                KASSERT(ne->ne_defexported.netc_anon == NULL);
        }

        mp->mnt_flag &= ~(MNT_EXPORTED | MNT_DEFEXPORTED);
}

/*
 * Add a new export entry (described by an export_args structure) to the
 * given file system.
 */
static int
export(struct netexport *nep, const struct export_args *argp)
{
        struct mount *mp = nep->ne_mount;
        int error;

        if (argp->ex_flags & MNT_EXPORTED) {
                if (argp->ex_flags & MNT_EXPUBLIC) {
                        if ((error = setpublicfs(mp, nep, argp)) != 0)
                                return error;
                        mp->mnt_flag |= MNT_EXPUBLIC;
                }
                if ((error = hang_addrlist(mp, nep, argp)) != 0)
                        return error;
                mp->mnt_flag |= MNT_EXPORTED;
        }
        return 0;
}

/*
 * Set the publicly exported filesystem (WebNFS).  Currently, only
 * one public filesystem is possible in the spec (RFC 2054 and 2055)
 */
static int
setpublicfs(struct mount *mp, struct netexport *nep,
    const struct export_args *argp)
{
        char *cp;
        int error;
        struct vnode *rvp;
        size_t fhsize;

        /*
         * mp == NULL --> invalidate the current info; the FS is
         * no longer exported. May be called from either export
         * or unmount, so check if it hasn't already been done.
         */
        if (mp == NULL) {
                if (nfs_pub.np_valid) {
                        nfs_pub.np_valid = 0;
                        if (nfs_pub.np_handle != NULL) {
                                free(nfs_pub.np_handle, M_TEMP);
                                nfs_pub.np_handle = NULL;
                        }
                        if (nfs_pub.np_index != NULL) {
                                free(nfs_pub.np_index, M_TEMP);
                                nfs_pub.np_index = NULL;
                        }
                }
                return 0;
        }

        /*
         * Only one allowed at a time.
         */
        if (nfs_pub.np_valid != 0 && mp != nfs_pub.np_mount)
                return EBUSY;

        /*
         * Get real filehandle for root of exported FS.
         */
        if ((error = VFS_ROOT(mp, LK_EXCLUSIVE, &rvp)))
                return error;

        fhsize = 0;
        error = vfs_composefh(rvp, NULL, &fhsize);
        if (error != E2BIG)
                return error;
        nfs_pub.np_handle = malloc(fhsize, M_TEMP, M_NOWAIT);
        if (nfs_pub.np_handle == NULL)
                error = ENOMEM;
        else
                error = vfs_composefh(rvp, nfs_pub.np_handle, &fhsize);
        if (error)
                return error;

        vput(rvp);

        /*
         * If an indexfile was specified, pull it in.
         */
        if (argp->ex_indexfile != NULL) {
                nfs_pub.np_index = malloc(NFS_MAXNAMLEN + 1, M_TEMP, M_WAITOK);
                error = copyinstr(argp->ex_indexfile, nfs_pub.np_index,
                    NFS_MAXNAMLEN, (size_t *)0);
                if (!error) {
                        /*
                         * Check for illegal filenames.
                         */
                        for (cp = nfs_pub.np_index; *cp; cp++) {
                                if (*cp == '/') {
                                        error = EINVAL;
                                        break;
                                }
                        }
                }
                if (error) {
                        free(nfs_pub.np_index, M_TEMP);
                        return error;
                }
        }

        nfs_pub.np_mount = mp;
        nfs_pub.np_valid = 1;
        return 0;
}

/*
 * Look up an export entry in the exports list that matches the address
 * stored in 'nam'.  If no entry is found, the default one is used instead
 * (if available).
 */
static struct netcred *
netcred_lookup(struct netexport *ne, struct mbuf *nam)
{
        struct netcred *np;
        struct radix_node_head *rnh;
        struct sockaddr *saddr;

        if ((ne->ne_mount->mnt_flag & MNT_EXPORTED) == 0) {
                return NULL;
        }

        /*
         * Look in the export list first.
         */
        np = NULL;
        if (nam != NULL) {
                saddr = mtod(nam, struct sockaddr *);
                rnh = ne->ne_rtable[saddr->sa_family];
                if (rnh != NULL) {
                        np = (struct netcred *)
                                (*rnh->rnh_matchaddr)((void *)saddr,
                                                      rnh);
                        if (np && np->netc_rnodes->rn_flags & RNF_ROOT)
                                np = NULL;
                }
        }
        /*
         * If no address match, use the default if it exists.
         */
        if (np == NULL && ne->ne_mount->mnt_flag & MNT_DEFEXPORTED)
                np = &ne->ne_defexported;

        return np;
}

void
netexport_rdlock(void)
{

        rw_enter(&netexport_lock, RW_READER);
}

void
netexport_rdunlock(void)
{

        rw_exit(&netexport_lock);
}

static void
netexport_wrlock(void)
{

        rw_enter(&netexport_lock, RW_WRITER);
}

static void
netexport_wrunlock(void)
{

        rw_exit(&netexport_lock);
}

bool
netexport_hasexports(void)
{
        
        return nfs_pub.np_valid || !TAILQ_EMPTY(&netexport_list);
}