/*-
 * SPDX-License-Identifier: BSD-2-Clause-FreeBSD
 *
 * Copyright (c) 2016 Tomohiro Kusumi <tkusumi@netbsd.org>
 * Copyright (c) 2016 The DragonFly Project
 * Copyright (c) 2014 The FreeBSD Foundation
 * All rights reserved.
 *
 * This software was developed by Edward Tomasz Napierala under sponsorship
 * from the FreeBSD Foundation.
 *
 * 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 AUTHOR 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 AUTHOR 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.
 *
 */

#include <sys/kernel.h>
#include <sys/module.h>
#include <sys/stat.h>
#include <sys/dirent.h>
#include <sys/nlookup.h>
#include <sys/mountctl.h>

#include "autofs.h"

static bool
test_fs_root(struct vnode *vp)
{
        int error;

        if ((error = vget(vp, LK_SHARED)) != 0) {
                AUTOFS_WARN("vget failed with error %d", error);
                return (false);
        }

        if (((vp->v_flag & VROOT) == 0) || (vp->v_tag == VT_AUTOFS)) {
                vput(vp);
                return (false);
        }

        return (true);
}

static bool
nlookup_fs_root(struct autofs_node *anp, struct vnode **vpp)
{
        struct nlookupdata nd;
        char *path;
        int error;

        path = autofs_path(anp);

        error = nlookup_init(&nd, path, UIO_SYSSPACE, NLC_FOLLOW);
        if (error == 0) {
                error = nlookup(&nd);
                if (error == 0) {
                        struct vnode *vp = nd.nl_nch.ncp->nc_vp;
                        if (test_fs_root(vp) == true)
                                *vpp = vp;
                        else
                                error = 1;
                }
        }
        nlookup_done(&nd);
        kfree(path, M_AUTOFS);

        return (error ? false : true);
}

static int
autofs_access(struct vop_access_args *ap)
{
        /*
         * Nothing to do here; the only kind of access control
         * needed is in autofs_mkdir().
         */
        return (0);
}

static int
autofs_getattr(struct vop_getattr_args *ap)
{
        struct vnode *vp = ap->a_vp;
        struct vattr *vap = ap->a_vap;
        struct autofs_node *anp = VTOI(vp);

        KASSERT(vp->v_type == VDIR, ("!VDIR"));

        /*
         * The reason we must do this is that some tree-walking software,
         * namely fts(3), assumes that stat(".") results will not change
         * between chdir("subdir") and chdir(".."), and fails with ENOENT
         * otherwise.
         *
         * XXX: Not supported on DragonFly.
         * With the current trigger mechanism on DragonFly, the process
         * will hang while in nlookup() in nlookup_fs_root().
         */
#if 0
        if (autofs_mount_on_stat && ...) {
        }
#endif
        vap->va_type = VDIR;
        vap->va_nlink = 3; /* XXX: FreeBSD had it like this */
        vap->va_mode = 0755;
        vap->va_uid = 0;
        vap->va_gid = 0;
        vap->va_fsid = vp->v_mount->mnt_stat.f_fsid.val[0];
        vap->va_fileid = anp->an_ino;
        vap->va_size = S_BLKSIZE;
        vap->va_blocksize = S_BLKSIZE;
        vap->va_atime = anp->an_ctime;
        vap->va_mtime = anp->an_ctime;
        vap->va_ctime = anp->an_ctime;
        vap->va_gen = 0;
        vap->va_flags = 0;
        vap->va_rmajor = 0;
        vap->va_rminor = 0;
        vap->va_bytes = S_BLKSIZE;
        vap->va_filerev = 0;
        vap->va_vaflags = 0;
        vap->va_spare = 0;

        return (0);
}

static int
autofs_trigger_vn(struct vnode *vp, const char *path, int pathlen,
    struct vnode **newvp)
{
        struct autofs_node *anp = VTOI(vp);
        struct vnode *nvp = NULL;
        int error;

        KKASSERT(!vn_islocked(vp));

        if (test_fs_root(vp) == true)
                goto mounted;

        /*
         * Don't remove this lookup.  Without this, the process
         * may trigger automountd(8) to mount the filesystem for the
         * second time after successful mount, and the second attempt
         * will fail.
         */
        if (nlookup_fs_root(anp, &nvp) == true)
                goto mounted;

        mtx_lock_ex_quick(&autofs_softc->sc_lock);
        error = autofs_trigger(anp, path, pathlen);
        mtx_unlock_ex(&autofs_softc->sc_lock);

        if (error)
                return (error);

        if (nlookup_fs_root(anp, &nvp) == false)
                return (0);

        /*
         * If the operation that succeeded was mount, then mark
         * the node as non-cached.  Otherwise, if someone unmounts
         * the filesystem before the cache times out, we will fail
         * to trigger.
         */
        autofs_node_uncache(anp);
mounted:
        *newvp = nvp;
        KKASSERT(vn_islocked(*newvp));

        return (0);
}

static int
autofs_nresolve(struct vop_nresolve_args *ap)
{
        struct vnode *vp = NULL;
        struct vnode *dvp = ap->a_dvp;
        struct nchandle *nch = ap->a_nch;
        struct namecache *ncp = nch->ncp;
        struct autofs_mount *amp = VFSTOAUTOFS(dvp->v_mount);
        struct autofs_node *anp = VTOI(dvp);
        struct autofs_node *child = NULL;
        int error;

        if (autofs_cached(anp, ncp->nc_name, ncp->nc_nlen) == false &&
            autofs_ignore_thread() == false) {
                struct vnode *newvp = NULL;

                cache_hold(nch);
                cache_unlock(nch);
                error = autofs_trigger_vn(dvp, ncp->nc_name, ncp->nc_nlen,
                    &newvp);
                cache_lock(nch);
                cache_drop(nch);
                if (error)
                        return (error);
                if (newvp != NULL) {
                        KKASSERT(newvp->v_tag != VT_AUTOFS);
                        vput(newvp);
                        return (ESTALE);
                }
                return (0);
        }

        mtx_lock_sh_quick(&amp->am_lock);
        error = autofs_node_find(anp, ncp->nc_name, ncp->nc_nlen, &child);
        mtx_unlock_sh(&amp->am_lock);

        if (error) {
                cache_setvp(nch, NULL);
                return (0);
        }

        error = autofs_node_vn(child, dvp->v_mount, LK_EXCLUSIVE, &vp);
        if (error == 0) {
                KKASSERT(vn_islocked(vp));
                vn_unlock(vp);
                cache_setvp(nch, vp);
                vrele(vp);
                return (0);
        }

        return (error);
}

static int
autofs_nmkdir(struct vop_nmkdir_args *ap)
{
        struct vnode *vp = NULL;
        struct vnode *dvp = ap->a_dvp;
        struct nchandle *nch = ap->a_nch;
        struct namecache *ncp = nch->ncp;
        struct autofs_mount *amp = VFSTOAUTOFS(dvp->v_mount);
        struct autofs_node *anp = VTOI(dvp);
        struct autofs_node *child = NULL;
        int error;

        /*
         * Do not allow mkdir() if the calling thread is not
         * automountd(8) descendant.
         */
        if (autofs_ignore_thread() == false)
                return (EPERM);

        mtx_lock_ex_quick(&amp->am_lock);
        error = autofs_node_new(anp, amp, ncp->nc_name, ncp->nc_nlen, &child);
        mtx_unlock_ex(&amp->am_lock);
        KKASSERT(error == 0);

        error = autofs_node_vn(child, dvp->v_mount, LK_EXCLUSIVE, &vp);
        if (error == 0) {
                KKASSERT(vn_islocked(vp));
                cache_setunresolved(nch);
                cache_setvp(nch, vp);
                *(ap->a_vpp) = vp;
                return (0);
        }

        return (error);
}

static __inline size_t
autofs_dirent_reclen(const char *name)
{
        return (_DIRENT_RECLEN(strlen(name)));
}

static int
autofs_write_dirent(struct uio *uio, const char *name, ino_t ino)
{
        int error = 0;

        if (vop_write_dirent(&error, uio, ino, DT_DIR, strlen(name), name))
                return (-1);

        return (error);
}

static int
autofs_readdir(struct vop_readdir_args *ap)
{
        struct vnode *vp = ap->a_vp;
        struct autofs_mount *amp = VFSTOAUTOFS(vp->v_mount);
        struct autofs_node *anp = VTOI(vp);
        struct autofs_node *child;
        struct uio *uio = ap->a_uio;
        ssize_t initial_resid = ap->a_uio->uio_resid;
        size_t reclens;
        int error;

        KASSERT(vp->v_type == VDIR, ("!VDIR"));

        if (autofs_cached(anp, NULL, 0) == false &&
            autofs_ignore_thread() == false) {
                struct vnode *newvp = NULL;
                error = autofs_trigger_vn(vp, "", 0, &newvp);
                if (error)
                        return (error);
                if (newvp != NULL) {
                        KKASSERT(newvp->v_tag != VT_AUTOFS);
                        vn_unlock(newvp);
                        error = VOP_READDIR(newvp, ap->a_uio, ap->a_cred,
                            ap->a_eofflag, ap->a_ncookies, ap->a_cookies);
                        vrele(newvp);
                        return (error);
                }
        }

        if (uio->uio_offset < 0)
                return (EINVAL);

        if (ap->a_eofflag != NULL)
                *ap->a_eofflag = FALSE;

        /*
         * Write out the directory entry for ".".
         */
        if (uio->uio_offset == 0) {
                error = autofs_write_dirent(uio, ".", anp->an_ino);
                if (error) {
                        if (error == -1)
                                error = 0;
                        goto out;
                }
        }
        reclens = autofs_dirent_reclen(".");

        /*
         * Write out the directory entry for "..".
         */
        if (uio->uio_offset <= reclens) {
                if (uio->uio_offset != reclens)
                        return (EINVAL);
                error = autofs_write_dirent(uio, "..",
                    anp->an_parent ? anp->an_parent->an_ino : anp->an_ino);
                if (error) {
                        if (error == -1)
                                error = 0;
                        goto out;
                }
        }
        reclens += autofs_dirent_reclen("..");

        /*
         * Write out the directory entries for subdirectories.
         */
        mtx_lock_sh_quick(&amp->am_lock);
        RB_FOREACH(child, autofs_node_tree, &anp->an_children) {
                /*
                 * Check the offset to skip entries returned by previous
                 * calls to getdents().
                 */
                if (uio->uio_offset > reclens) {
                        reclens += autofs_dirent_reclen(child->an_name);
                        continue;
                }

                /*
                 * Prevent seeking into the middle of dirent.
                 */
                if (uio->uio_offset != reclens) {
                        mtx_unlock_sh(&amp->am_lock);
                        return (EINVAL);
                }

                error = autofs_write_dirent(uio, child->an_name, child->an_ino);
                reclens += autofs_dirent_reclen(child->an_name);
                if (error) {
                        if (error == -1)
                                error = 0;
                        mtx_unlock_sh(&amp->am_lock);
                        goto out;
                }
        }
        mtx_unlock_sh(&amp->am_lock);

        if (ap->a_eofflag != NULL)
                *ap->a_eofflag = TRUE;

        return (0);
out:
        /*
         * Return error if the initial buffer was too small to do anything.
         */
        if (uio->uio_resid == initial_resid)
                return (error);

        /*
         * Don't return an error if we managed to copy out some entries.
         */
        if (uio->uio_resid < initial_resid)
                return (0);

        return (error);
}

static int
autofs_reclaim(struct vop_reclaim_args *ap)
{
        struct vnode *vp = ap->a_vp;
        struct autofs_node *anp = VTOI(vp);

        /*
         * We do not free autofs_node here; instead we are
         * destroying them in autofs_node_delete().
         */
        mtx_lock_ex_quick(&anp->an_vnode_lock);
        anp->an_vnode = NULL;
        vp->v_data = NULL;
        mtx_unlock_ex(&anp->an_vnode_lock);

        return (0);
}

static int
autofs_mountctl(struct vop_mountctl_args *ap)
{
        struct mount *mp;
        int res = 0;

        mp = ap->a_head.a_ops->head.vv_mount;
        lwkt_gettoken(&mp->mnt_token);

        switch (ap->a_op) {
        //case ...:
        //      break;
        default:
                res = vop_stdmountctl(ap);
                break;
        }

        lwkt_reltoken(&mp->mnt_token);
        return (res);
}

static int
autofs_print(struct vop_print_args *ap)
{
        struct autofs_node *anp = VTOI(ap->a_vp);

        kprintf("tag VT_AUTOFS, node %p, ino %jd, name %s, cached %d, retries %d, wildcards %d\n",
            anp, (intmax_t)anp->an_ino, anp->an_name, anp->an_cached,
            anp->an_retries, anp->an_wildcards);

        return (0);
}

struct vop_ops autofs_vnode_vops = {
        .vop_default =          vop_defaultop,
        .vop_access =           autofs_access,
        .vop_getattr =          autofs_getattr,
        .vop_nresolve =         autofs_nresolve,
        .vop_nmkdir =           autofs_nmkdir,
        .vop_readdir =          autofs_readdir,
        .vop_reclaim =          autofs_reclaim,
        .vop_mountctl =         autofs_mountctl,
        .vop_print =            autofs_print,
};

int
autofs_node_new(struct autofs_node *parent, struct autofs_mount *amp,
    const char *name, int namelen, struct autofs_node **anpp)
{
        struct autofs_node *anp;

        KKASSERT(mtx_islocked_ex(&amp->am_lock));

        if (parent != NULL) {
                KKASSERT(mtx_islocked_ex(&parent->an_mount->am_lock));
                KASSERT(autofs_node_find(parent, name, namelen, NULL) == ENOENT,
                    ("node \"%s\" already exists", name));
        }

        /*
         * All struct fields must be initialized.
         */
        anp = objcache_get(autofs_node_objcache, M_WAITOK);
        if (namelen >= 0)
                anp->an_name = kstrndup(name, namelen, M_AUTOFS);
        else
                anp->an_name = kstrdup(name, M_AUTOFS);
        anp->an_ino = amp->am_last_ino++;
        callout_init(&anp->an_callout);
        mtx_init(&anp->an_vnode_lock, "autofsvnlk");
        getnanotime(&anp->an_ctime);
        anp->an_parent = parent;
        anp->an_mount = amp;
        anp->an_vnode = NULL;
        anp->an_cached = false;
        anp->an_wildcards = false;
        anp->an_retries = 0;
        if (parent != NULL)
                RB_INSERT(autofs_node_tree, &parent->an_children, anp);
        RB_INIT(&anp->an_children);

        *anpp = anp;

        return (0);
}

int
autofs_node_find(struct autofs_node *parent, const char *name, int namelen,
    struct autofs_node **anpp)
{
        struct autofs_node *anp, find;
        int error;

        KKASSERT(mtx_islocked(&parent->an_mount->am_lock));

        if (namelen >= 0)
                find.an_name = kstrndup(name, namelen, M_AUTOFS);
        else
                find.an_name = kstrdup(name, M_AUTOFS);

        anp = RB_FIND(autofs_node_tree, &parent->an_children, &find);
        if (anp != NULL) {
                error = 0;
                if (anpp != NULL)
                        *anpp = anp;
        } else {
                error = ENOENT;
        }

        kfree(find.an_name, M_AUTOFS);

        return (error);
}

void
autofs_node_delete(struct autofs_node *anp)
{
        KKASSERT(mtx_islocked_ex(&anp->an_mount->am_lock));
        KASSERT(RB_EMPTY(&anp->an_children), ("have children"));

        callout_drain(&anp->an_callout);

        if (anp->an_parent != NULL)
                RB_REMOVE(autofs_node_tree, &anp->an_parent->an_children, anp);

        mtx_uninit(&anp->an_vnode_lock);
        kfree(anp->an_name, M_AUTOFS);
        objcache_put(autofs_node_objcache, anp);
}

int
autofs_node_vn(struct autofs_node *anp, struct mount *mp, int flags,
    struct vnode **vpp)
{
        struct vnode *vp = NULL;
        int error;
retry:
        KKASSERT(mtx_notlocked(&anp->an_mount->am_lock));
        mtx_lock_ex_quick(&anp->an_vnode_lock);

        vp = anp->an_vnode;
        if (vp != NULL) {
                vhold(vp);
                mtx_unlock_ex(&anp->an_vnode_lock);

                error = vget(vp, flags | LK_RETRY);
                if (error) {
                        AUTOFS_WARN("vget failed with error %d", error);
                        vdrop(vp);
                        goto retry;
                }
                vdrop(vp);
                *vpp = vp;
                return (0);
        }

        mtx_unlock_ex(&anp->an_vnode_lock);

        error = getnewvnode(VT_AUTOFS, mp, &vp, VLKTIMEOUT, LK_CANRECURSE);
        if (error)
                return (error);
        vp->v_type = VDIR;
        vp->v_data = anp;

        KASSERT(anp->an_vnode == NULL, ("lost race"));
        anp->an_vnode = vp;
        vx_downgrade(vp);       /* downgrade VX lock to VN lock */
        *vpp = vp;

        return (0);
}