/*      $NetBSD: null.c,v 1.37 2026/04/19 19:57:01 rillig Exp $ */

/*
 * Copyright (c) 2007  Antti Kantee.  All Rights Reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 *
 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``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/cdefs.h>
#if !defined(lint)
__RCSID("$NetBSD: null.c,v 1.37 2026/04/19 19:57:01 rillig Exp $");
#endif /* !lint */

/*
 * A "nullfs" using puffs, i.e. maps one location in the hierarchy
 * to another using standard system calls.
 */

#include <sys/types.h>
#include <sys/stat.h>
#include <sys/time.h>

#include <assert.h>
#include <dirent.h>
#include <errno.h>
#include <fcntl.h>
#include <puffs.h>
#include <stdio.h>
#include <stdlib.h>
#include <time.h>
#include <unistd.h>

PUFFSOP_PROTOS(puffs_null)

/*
 * set attributes to what is specified.  XXX: no rollback in case of failure
 */
static int
processvattr(const char *path, const struct vattr *va, int regular)
{
        struct timeval tv[2];

        /* XXX: -1 == PUFFS_VNOVAL, but shouldn't trust that */
        if (va->va_uid != (unsigned)-1 || va->va_gid != (unsigned)-1)
                if (lchown(path, va->va_uid, va->va_gid) == -1)
                        return errno;

        if (va->va_mode != (unsigned)PUFFS_VNOVAL)
                if (lchmod(path, va->va_mode) == -1)
                        return errno;

        /* sloppy */
        if (va->va_atime.tv_sec != (time_t)PUFFS_VNOVAL
            || va->va_mtime.tv_sec != (time_t)PUFFS_VNOVAL) {
                TIMESPEC_TO_TIMEVAL(&tv[0], &va->va_atime);
                TIMESPEC_TO_TIMEVAL(&tv[1], &va->va_mtime);

                if (lutimes(path, tv) == -1)
                        return errno;
        }

        if (regular && va->va_size != (u_quad_t)PUFFS_VNOVAL)
                if (truncate(path, (off_t)va->va_size) == -1)
                        return errno;

        return 0;
}

/*
 * Kludge to open files which aren't writable *any longer*.  This kinda
 * works because the vfs layer does validation checks based on the file's
 * permissions to allow writable opening before opening them.  However,
 * the problem arises if we want to create a file, write to it (cache),
 * adjust permissions and then flush the file.
 */
static int
writeableopen(const char *path)
{
        struct stat sb;
        mode_t origmode;
        int sverr = 0;
        int fd;

        fd = open(path, O_WRONLY);
        if (fd == -1) {
                if (errno == EACCES) {
                        if (stat(path, &sb) == -1)
                                return -1;
                        origmode = sb.st_mode & ALLPERMS;

                        if (chmod(path, 0200) == -1)
                                return -1;

                        fd = open(path, O_WRONLY);
                        if (fd == -1)
                                sverr = errno;

                        chmod(path, origmode);
                        if (sverr)
                                errno = sverr;
                } else
                        return -1;
        }

        return fd;
}

/*ARGSUSED*/
static void *
inodecmp(struct puffs_usermount *pu, struct puffs_node *pn, void *arg)
{
        ino_t *cmpino = arg;

        if (pn->pn_va.va_fileid == *cmpino)
                return pn;
        return NULL;
}

static int
makenode(struct puffs_usermount *pu, struct puffs_newinfo *pni,
        const struct puffs_cn *pcn, const struct vattr *va, int regular)
{
        struct puffs_node *pn;
        struct stat sb;
        int rv;

        if ((rv = processvattr(PCNPATH(pcn), va, regular)) != 0)
                return rv;

        pn = puffs_pn_new(pu, NULL);
        if (!pn)
                return ENOMEM;
        puffs_setvattr(&pn->pn_va, va);

        if (lstat(PCNPATH(pcn), &sb) == -1)
                return errno;
        puffs_stat2vattr(&pn->pn_va, &sb);

        puffs_newinfo_setcookie(pni, pn);
        return 0;
}

/* This should be called first and overridden from the file system */
void
puffs_null_setops(struct puffs_ops *pops)
{

        PUFFSOP_SET(pops, puffs_null, fs, statvfs);
        PUFFSOP_SETFSNOP(pops, unmount);
        PUFFSOP_SETFSNOP(pops, sync);
        PUFFSOP_SET(pops, puffs_null, fs, fhtonode);
        PUFFSOP_SET(pops, puffs_null, fs, nodetofh);

        PUFFSOP_SET(pops, puffs_null, node, lookup);
        PUFFSOP_SET(pops, puffs_null, node, create);
        PUFFSOP_SET(pops, puffs_null, node, mknod);
        PUFFSOP_SET(pops, puffs_null, node, getattr);
        PUFFSOP_SET(pops, puffs_null, node, setattr);
        PUFFSOP_SET(pops, puffs_null, node, fsync);
        PUFFSOP_SET(pops, puffs_null, node, remove);
        PUFFSOP_SET(pops, puffs_null, node, link);
        PUFFSOP_SET(pops, puffs_null, node, rename);
        PUFFSOP_SET(pops, puffs_null, node, mkdir);
        PUFFSOP_SET(pops, puffs_null, node, rmdir);
        PUFFSOP_SET(pops, puffs_null, node, symlink);
        PUFFSOP_SET(pops, puffs_null, node, readlink);
        PUFFSOP_SET(pops, puffs_null, node, readdir);
        PUFFSOP_SET(pops, puffs_null, node, read);
        PUFFSOP_SET(pops, puffs_null, node, write);
        PUFFSOP_SET(pops, puffs_genfs, node, reclaim);
}

/*ARGSUSED*/
int
puffs_null_fs_statvfs(struct puffs_usermount *pu, struct puffs_statvfs *svfsb)
{
        struct statvfs sb;
        if (statvfs(PNPATH(puffs_getroot(pu)), &sb) == -1)
                return errno;
        statvfs_to_puffs_statvfs(&sb, svfsb);

        return 0;
}

/*
 * XXX: this is the stupidest crap ever, but:
 * getfh() returns the fhandle type, when we are expected to deliver
 * the fid type.  Just adjust it a bit and stop whining.
 *
 * Yes, this really really needs fixing.  Yes, *REALLY*.
 */
#define FHANDLE_HEADERLEN 8
struct kernfid {
        unsigned short  fid_len;                /* length of data in bytes */
        unsigned short  fid_reserved;           /* compat: historic align */
        char            fid_data[0];            /* data (variable length) */
};

/*ARGSUSED*/
static void *
fhcmp(struct puffs_usermount *pu, struct puffs_node *pn, void *arg)
{
        struct kernfid *kf1, *kf2;

        if ((kf1 = pn->pn_data) == NULL)
                return NULL;
        kf2 = arg;

        if (kf1->fid_len != kf2->fid_len)
                return NULL;

        if (memcmp(kf1, kf2, kf1->fid_len) == 0)
                return pn;
        return NULL;
}

/*
 * This routine only supports file handles which have been issued while
 * the server was alive.  Not really stable ones, that is.
 */
/*ARGSUSED*/
int
puffs_null_fs_fhtonode(struct puffs_usermount *pu, void *fid, size_t fidsize,
        struct puffs_newinfo *pni)
{
        struct puffs_node *pn_res;

        pn_res = puffs_pn_nodewalk(pu, fhcmp, fid);
        if (pn_res == NULL)
                return ENOENT;

        puffs_newinfo_setcookie(pni, pn_res);
        puffs_newinfo_setvtype(pni, pn_res->pn_va.va_type);
        puffs_newinfo_setsize(pni, (voff_t)pn_res->pn_va.va_size);
        puffs_newinfo_setrdev(pni, pn_res->pn_va.va_rdev);
        return 0;
}

/*ARGSUSED*/
int
puffs_null_fs_nodetofh(struct puffs_usermount *pu, puffs_cookie_t opc,
        void *fid, size_t *fidsize)
{
        struct puffs_node *pn = opc;
        struct kernfid *kfid;
        void *bounce;
        int rv;

        rv = 0;
        bounce = NULL;
        if (*fidsize) {
                bounce = malloc(*fidsize + FHANDLE_HEADERLEN);
                if (!bounce)
                        return ENOMEM;
                *fidsize += FHANDLE_HEADERLEN;
        }
        if (getfh(PNPATH(pn), bounce, fidsize) == -1)
                rv = errno;
        else
                memcpy(fid, (uint8_t *)bounce + FHANDLE_HEADERLEN,
                    *fidsize - FHANDLE_HEADERLEN);
        kfid = fid;
        if (rv == 0) {
                *fidsize = kfid->fid_len;
                pn->pn_data = malloc(*fidsize);
                if (pn->pn_data == NULL)
                        abort(); /* lazy */
                memcpy(pn->pn_data, fid, *fidsize);
        } else {
                *fidsize -= FHANDLE_HEADERLEN;
        }
        free(bounce);

        return rv;
}

int
puffs_null_node_lookup(struct puffs_usermount *pu, puffs_cookie_t opc,
        struct puffs_newinfo *pni, const struct puffs_cn *pcn)
{
        struct puffs_node *pn = opc, *pn_res;
        struct stat sb;
        int rv;

        assert(pn->pn_va.va_type == VDIR);

        /*
         * Note to whoever is copypasting this: you must first check
         * if the node is there and only then do nodewalk.  Alternatively
         * you could make sure that you don't return unlinked/rmdir'd
         * nodes in some other fashion
         */
        rv = lstat(PCNPATH(pcn), &sb);
        if (rv)
                return errno;

        /* XXX2: nodewalk is a bit too slow here */
        pn_res = puffs_pn_nodewalk(pu, inodecmp, &sb.st_ino);

        if (pn_res == NULL) {
                pn_res = puffs_pn_new(pu, NULL);
                if (pn_res == NULL)
                        return ENOMEM;
                puffs_stat2vattr(&pn_res->pn_va, &sb);
        }

        puffs_newinfo_setcookie(pni, pn_res);
        puffs_newinfo_setvtype(pni, pn_res->pn_va.va_type);
        puffs_newinfo_setsize(pni, (voff_t)pn_res->pn_va.va_size);
        puffs_newinfo_setrdev(pni, pn_res->pn_va.va_rdev);

        return 0;
}

/*ARGSUSED*/
int
puffs_null_node_create(struct puffs_usermount *pu, puffs_cookie_t opc,
        struct puffs_newinfo *pni, const struct puffs_cn *pcn,
        const struct vattr *va)
{
        int fd, rv;

        fd = open(PCNPATH(pcn), O_RDWR | O_CREAT | O_TRUNC);
        if (fd == -1)
                return errno;
        close(fd);

        rv = makenode(pu, pni, pcn, va, 1);
        if (rv)
                unlink(PCNPATH(pcn));
        return rv;
}

/*ARGSUSED*/
int
puffs_null_node_mknod(struct puffs_usermount *pu, puffs_cookie_t opc,
        struct puffs_newinfo *pni, const struct puffs_cn *pcn,
        const struct vattr *va)
{
        mode_t mode;
        int rv;

        mode = puffs_addvtype2mode(va->va_mode, va->va_type);
        if (mknod(PCNPATH(pcn), mode, va->va_rdev) == -1)
                return errno;

        rv = makenode(pu, pni, pcn, va, 0);
        if (rv)
                unlink(PCNPATH(pcn));
        return rv;
}

/*ARGSUSED*/
int
puffs_null_node_getattr(struct puffs_usermount *pu, puffs_cookie_t opc,
        struct vattr *va, const struct puffs_cred *pcred)
{
        struct puffs_node *pn = opc;
        struct stat sb;

        if (lstat(PNPATH(pn), &sb) == -1)
                return errno;
        puffs_stat2vattr(va, &sb);

        return 0;
}

/*ARGSUSED*/
int
puffs_null_node_setattr(struct puffs_usermount *pu, puffs_cookie_t opc,
        const struct vattr *va, const struct puffs_cred *pcred)
{
        struct puffs_node *pn = opc;
        int rv;

        rv = processvattr(PNPATH(pn), va, pn->pn_va.va_type == VREG);
        if (rv)
                return rv;

        puffs_setvattr(&pn->pn_va, va);

        return 0;
}

/*ARGSUSED*/
int
puffs_null_node_fsync(struct puffs_usermount *pu, puffs_cookie_t opc,
        const struct puffs_cred *pcred, int how,
        off_t offlo, off_t offhi)
{
        struct puffs_node *pn = opc;
        int fd, rv;
        int fflags;
        struct stat sb;
        DIR *dirp;

        rv = 0;
        if (stat(PNPATH(pn), &sb) == -1)
                return errno;
        if (S_ISDIR(sb.st_mode)) {
                if ((dirp = opendir(PNPATH(pn))) == NULL)
                        return errno;
                fd = dirfd(dirp);
                if (fd == -1) {
                        rv = errno;
                        closedir(dirp);
                        return rv;
                }

                if (fsync(fd) == -1)
                        rv = errno;

                closedir(dirp);
        } else {
                fd = writeableopen(PNPATH(pn));
                if (fd == -1)
                        return errno;

                if (how & PUFFS_FSYNC_DATAONLY)
                        fflags = FDATASYNC;
                else
                        fflags = FFILESYNC;
                if (how & PUFFS_FSYNC_CACHE)
                        fflags |= FDISKSYNC;

                if (fsync_range(fd, fflags, offlo, offhi - offlo) == -1)
                        rv = errno;

                close(fd);
        }

        return rv;
}

/*ARGSUSED*/
int
puffs_null_node_remove(struct puffs_usermount *pu, puffs_cookie_t opc,
        puffs_cookie_t targ, const struct puffs_cn *pcn)
{
        struct puffs_node *pn_targ = targ;

        if (unlink(PNPATH(pn_targ)) == -1)
                return errno;
        puffs_pn_remove(pn_targ);

        return 0;
}

/*ARGSUSED*/
int
puffs_null_node_link(struct puffs_usermount *pu, puffs_cookie_t opc,
        puffs_cookie_t targ, const struct puffs_cn *pcn)
{
        struct puffs_node *pn_targ = targ;

        if (link(PNPATH(pn_targ), PCNPATH(pcn)) == -1)
                return errno;

        return 0;
}

/*ARGSUSED*/
int
puffs_null_node_rename(struct puffs_usermount *pu, puffs_cookie_t opc,
        puffs_cookie_t src, const struct puffs_cn *pcn_src,
        puffs_cookie_t targ_dir, puffs_cookie_t targ,
        const struct puffs_cn *pcn_targ)
{
        struct puffs_node *pn_targ = targ;

        if (rename(PCNPATH(pcn_src), PCNPATH(pcn_targ)) == -1)
                return errno;

        if (pn_targ)
                puffs_pn_remove(pn_targ);

        return 0;
}

/*ARGSUSED*/
int
puffs_null_node_mkdir(struct puffs_usermount *pu, puffs_cookie_t opc,
        struct puffs_newinfo *pni, const struct puffs_cn *pcn,
        const struct vattr *va)
{
        int rv;

        if (mkdir(PCNPATH(pcn), va->va_mode) == -1)
                return errno;

        rv = makenode(pu, pni, pcn, va, 0);
        if (rv)
                rmdir(PCNPATH(pcn));
        return rv;
}

/*ARGSUSED*/
int
puffs_null_node_rmdir(struct puffs_usermount *pu, puffs_cookie_t opc,
        puffs_cookie_t targ, const struct puffs_cn *pcn)
{
        struct puffs_node *pn_targ = targ;

        if (rmdir(PNPATH(pn_targ)) == -1)
                return errno;
        puffs_pn_remove(pn_targ);

        return 0;
}

/*ARGSUSED*/
int
puffs_null_node_symlink(struct puffs_usermount *pu, puffs_cookie_t opc,
        struct puffs_newinfo *pni, const struct puffs_cn *pcn,
        const struct vattr *va, const char *linkname)
{
        int rv;

        if (symlink(linkname, PCNPATH(pcn)) == -1)
                return errno;

        rv = makenode(pu, pni, pcn, va, 0);
        if (rv)
                unlink(PCNPATH(pcn));
        return rv;
}

/*ARGSUSED*/
int
puffs_null_node_readlink(struct puffs_usermount *pu, puffs_cookie_t opc,
        const struct puffs_cred *pcred, char *linkname, size_t *linklen)
{
        struct puffs_node *pn = opc;
        ssize_t rv;

        rv = readlink(PNPATH(pn), linkname, *linklen);
        if (rv == -1)
                return errno;

        *linklen = rv;
        return 0;
}

/*ARGSUSED*/
int
puffs_null_node_readdir(struct puffs_usermount *pu, puffs_cookie_t opc,
        struct dirent *de, off_t *off, size_t *reslen,
        const struct puffs_cred *pcred, int *eofflag, off_t *cookies,
        size_t *ncookies)
{
        struct puffs_node *pn = opc;
        struct dirent entry, *result;
        DIR *dp;
        off_t i;
        int rv;

        *ncookies = 0;
        dp = opendir(PNPATH(pn));
        if (dp == NULL)
                return errno;

        rv = 0;
        i = *off;

        /*
         * XXX: need to do trickery here, telldir/seekdir would be nice, but
         * then we'd need to keep state, which I'm too lazy to keep
         */
        while (i--) {
                rv = readdir_r(dp, &entry, &result);
                if (rv != 0)
                        goto out;

                if (!result) {
                        *eofflag = 1;
                        goto out;
                }
        }

        for (;;) {
                rv = readdir_r(dp, &entry, &result);
                if (rv != 0)
                        goto out;

                if (!result) {
                        *eofflag = 1;
                        goto out;
                }

                if (_DIRENT_SIZE(result) > *reslen)
                        goto out;

                *de = *result;
                *reslen -= _DIRENT_SIZE(result);
                de = _DIRENT_NEXT(de);

                (*off)++;
                PUFFS_STORE_DCOOKIE(cookies, ncookies, *off);
        }

 out:
        closedir(dp);
        return 0;
}

/*ARGSUSED*/
int
puffs_null_node_read(struct puffs_usermount *pu, puffs_cookie_t opc,
        uint8_t *buf, off_t offset, size_t *buflen,
        const struct puffs_cred *pcred, int ioflag)
{
        struct puffs_node *pn = opc;
        ssize_t n;
        off_t off;
        int fd, rv;

        rv = 0;
        fd = open(PNPATH(pn), O_RDONLY);
        if (fd == -1)
                return errno;
        off = lseek(fd, offset, SEEK_SET);
        if (off == -1) {
                rv = errno;
                goto out;
        }

        n = read(fd, buf, *buflen);
        if (n == -1)
                rv = errno;
        else
                *buflen -= n;

 out:
        close(fd);
        return rv;
}

/*ARGSUSED*/
int
puffs_null_node_write(struct puffs_usermount *pu, puffs_cookie_t opc,
        uint8_t *buf, off_t offset, size_t *buflen,
        const struct puffs_cred *pcred, int ioflag)
{
        struct puffs_node *pn = opc;
        ssize_t n;
        off_t off;
        int fd, rv;

        rv = 0;
        fd = writeableopen(PNPATH(pn));
        if (fd == -1)
                return errno;

        off = lseek(fd, offset, SEEK_SET);
        if (off == -1) {
                rv = errno;
                goto out;
        }

        n = write(fd, buf, *buflen);
        if (n == -1)
                rv = errno;
        else
                *buflen -= n;

 out:
        close(fd);
        return rv;
}