subdir.c

/*
  fuse subdir module: offset paths with a base directory
  Copyright (C) 2007  Miklos Szeredi <miklos@szeredi.hu>

  This program can be distributed under the terms of the GNU LGPLv2.
  See the file COPYING.LIB
*/

#include <config.h>

#include <fuse.h>
#include <stdio.h>
#include <stdlib.h>
#include <stddef.h>
#include <string.h>
#include <errno.h>

struct subdir {
        char *base;
        size_t baselen;
        int rellinks;
        struct fuse_fs *next;
};

static struct subdir *subdir_get(void)
{
        return fuse_get_context()->private_data;
}

static int subdir_addpath(struct subdir *d, const char *path, char **newpathp)
{
        char *newpath = NULL;

        if (path != NULL) {
                unsigned newlen = d->baselen + strlen(path);

                newpath = malloc(newlen + 2);
                if (!newpath)
                        return -ENOMEM;

                if (path[0] == '/')
                        path++;
                strcpy(newpath, d->base);
                strcpy(newpath + d->baselen, path);
                if (!newpath[0])
                        strcpy(newpath, ".");
        }
        *newpathp = newpath;

        return 0;
}

static int subdir_getattr(const char *path, struct stat *stbuf,
                          struct fuse_file_info *fi)
{
        struct subdir *d = subdir_get();
        char *newpath;
        int err = subdir_addpath(d, path, &newpath);
        if (!err) {
                err = fuse_fs_getattr(d->next, newpath, stbuf, fi);
                free(newpath);
        }
        return err;
}

static int subdir_access(const char *path, int mask)
{
        struct subdir *d = subdir_get();
        char *newpath;
        int err = subdir_addpath(d, path, &newpath);
        if (!err) {
                err = fuse_fs_access(d->next, newpath, mask);
                free(newpath);
        }
        return err;
}


static int count_components(const char *p)
{
        int ctr;

        for (; *p == '/'; p++);
        for (ctr = 0; *p; ctr++) {
                for (; *p && *p != '/'; p++);
                for (; *p == '/'; p++);
        }
        return ctr;
}

static void strip_common(const char **sp, const char **tp)
{
        const char *s = *sp;
        const char *t = *tp;
        do {
                for (; *s == '/'; s++);
                for (; *t == '/'; t++);
                *tp = t;
                *sp = s;
                for (; *s == *t && *s && *s != '/'; s++, t++);
        } while ((*s == *t && *s) || (!*s && *t == '/') || (*s == '/' && !*t));
}

static void transform_symlink(struct subdir *d, const char *path,
                              char *buf, size_t size)
{
        const char *l = buf;
        size_t llen;
        char *s;
        int dotdots;
        int i;

        if (l[0] != '/' || d->base[0] != '/')
                return;

        strip_common(&l, &path);
        if (l - buf < (long) d->baselen)
                return;

        dotdots = count_components(path);
        if (!dotdots)
                return;
        dotdots--;

        llen = strlen(l);
        if (dotdots * 3 + llen + 2 > size)
                return;

        s = buf + dotdots * 3;
        if (llen)
                memmove(s, l, llen + 1);
        else if (!dotdots)
                strcpy(s, ".");
        else
                *s = '\0';

        for (s = buf, i = 0; i < dotdots; i++, s += 3)
                memcpy(s, "../", 3);
}


static int subdir_readlink(const char *path, char *buf, size_t size)
{
        struct subdir *d = subdir_get();
        char *newpath;
        int err = subdir_addpath(d, path, &newpath);
        if (!err) {
                err = fuse_fs_readlink(d->next, newpath, buf, size);
                if (!err && d->rellinks)
                        transform_symlink(d, newpath, buf, size);
                free(newpath);
        }
        return err;
}

static int subdir_opendir(const char *path, struct fuse_file_info *fi)
{
        struct subdir *d = subdir_get();
        char *newpath;
        int err = subdir_addpath(d, path, &newpath);
        if (!err) {
                err = fuse_fs_opendir(d->next, newpath, fi);
                free(newpath);
        }
        return err;
}

static int subdir_readdir(const char *path, void *buf,
                          fuse_fill_dir_t filler, off_t offset,
                          struct fuse_file_info *fi,
                          enum fuse_readdir_flags flags)
{
        struct subdir *d = subdir_get();
        char *newpath;
        int err = subdir_addpath(d, path, &newpath);
        if (!err) {
                err = fuse_fs_readdir(d->next, newpath, buf, filler, offset,
                                      fi, flags);
                free(newpath);
        }
        return err;
}

static int subdir_releasedir(const char *path, struct fuse_file_info *fi)
{
        struct subdir *d = subdir_get();
        char *newpath;
        int err = subdir_addpath(d, path, &newpath);
        if (!err) {
                err = fuse_fs_releasedir(d->next, newpath, fi);
                free(newpath);
        }
        return err;
}

static int subdir_mknod(const char *path, mode_t mode, dev_t rdev)
{
        struct subdir *d = subdir_get();
        char *newpath;
        int err = subdir_addpath(d, path, &newpath);
        if (!err) {
                err = fuse_fs_mknod(d->next, newpath, mode, rdev);
                free(newpath);
        }
        return err;
}

static int subdir_mkdir(const char *path, mode_t mode)
{
        struct subdir *d = subdir_get();
        char *newpath;
        int err = subdir_addpath(d, path, &newpath);
        if (!err) {
                err = fuse_fs_mkdir(d->next, newpath, mode);
                free(newpath);
        }
        return err;
}

static int subdir_unlink(const char *path)
{
        struct subdir *d = subdir_get();
        char *newpath;
        int err = subdir_addpath(d, path, &newpath);
        if (!err) {
                err = fuse_fs_unlink(d->next, newpath);
                free(newpath);
        }
        return err;
}

static int subdir_rmdir(const char *path)
{
        struct subdir *d = subdir_get();
        char *newpath;
        int err = subdir_addpath(d, path, &newpath);
        if (!err) {
                err = fuse_fs_rmdir(d->next, newpath);
                free(newpath);
        }
        return err;
}

static int subdir_symlink(const char *from, const char *path)
{
        struct subdir *d = subdir_get();
        char *newpath;
        int err = subdir_addpath(d, path, &newpath);
        if (!err) {
                err = fuse_fs_symlink(d->next, from, newpath);
                free(newpath);
        }
        return err;
}

static int subdir_rename(const char *from, const char *to, unsigned int flags)
{
        struct subdir *d = subdir_get();
        char *newfrom;
        char *newto;
        int err = subdir_addpath(d, from, &newfrom);
        if (!err) {
                err = subdir_addpath(d, to, &newto);
                if (!err) {
                        err = fuse_fs_rename(d->next, newfrom, newto, flags);
                        free(newto);
                }
                free(newfrom);
        }
        return err;
}

static int subdir_link(const char *from, const char *to)
{
        struct subdir *d = subdir_get();
        char *newfrom;
        char *newto;
        int err = subdir_addpath(d, from, &newfrom);
        if (!err) {
                err = subdir_addpath(d, to, &newto);
                if (!err) {
                        err = fuse_fs_link(d->next, newfrom, newto);
                        free(newto);
                }
                free(newfrom);
        }
        return err;
}

static int subdir_chmod(const char *path, mode_t mode,
                        struct fuse_file_info *fi)
{
        struct subdir *d = subdir_get();
        char *newpath;
        int err = subdir_addpath(d, path, &newpath);
        if (!err) {
                err = fuse_fs_chmod(d->next, newpath, mode, fi);
                free(newpath);
        }
        return err;
}

static int subdir_chown(const char *path, uid_t uid, gid_t gid,
                        struct fuse_file_info *fi)
{
        struct subdir *d = subdir_get();
        char *newpath;
        int err = subdir_addpath(d, path, &newpath);
        if (!err) {
                err = fuse_fs_chown(d->next, newpath, uid, gid, fi);
                free(newpath);
        }
        return err;
}

static int subdir_truncate(const char *path, off_t size,
                           struct fuse_file_info *fi)
{
        struct subdir *d = subdir_get();
        char *newpath;
        int err = subdir_addpath(d, path, &newpath);
        if (!err) {
                err = fuse_fs_truncate(d->next, newpath, size, fi);
                free(newpath);
        }
        return err;
}

static int subdir_utimens(const char *path, const struct timespec ts[2],
                          struct fuse_file_info *fi)
{
        struct subdir *d = subdir_get();
        char *newpath;
        int err = subdir_addpath(d, path, &newpath);
        if (!err) {
                err = fuse_fs_utimens(d->next, newpath, ts, fi);
                free(newpath);
        }
        return err;
}

static int subdir_create(const char *path, mode_t mode,
                         struct fuse_file_info *fi)
{
        struct subdir *d = subdir_get();
        char *newpath;
        int err = subdir_addpath(d, path, &newpath);
        if (!err) {
                err = fuse_fs_create(d->next, newpath, mode, fi);
                free(newpath);
        }
        return err;
}

static int subdir_open(const char *path, struct fuse_file_info *fi)
{
        struct subdir *d = subdir_get();
        char *newpath;
        int err = subdir_addpath(d, path, &newpath);
        if (!err) {
                err = fuse_fs_open(d->next, newpath, fi);
                free(newpath);
        }
        return err;
}

static int subdir_read_buf(const char *path, struct fuse_bufvec **bufp,
                           size_t size, off_t offset, struct fuse_file_info *fi)
{
        struct subdir *d = subdir_get();
        char *newpath;
        int err = subdir_addpath(d, path, &newpath);
        if (!err) {
                err = fuse_fs_read_buf(d->next, newpath, bufp, size, offset, fi);
                free(newpath);
        }
        return err;
}

static int subdir_write_buf(const char *path, struct fuse_bufvec *buf,
                        off_t offset, struct fuse_file_info *fi)
{
        struct subdir *d = subdir_get();
        char *newpath;
        int err = subdir_addpath(d, path, &newpath);
        if (!err) {
                err = fuse_fs_write_buf(d->next, newpath, buf, offset, fi);
                free(newpath);
        }
        return err;
}

static int subdir_statfs(const char *path, struct statvfs *stbuf)
{
        struct subdir *d = subdir_get();
        char *newpath;
        int err = subdir_addpath(d, path, &newpath);
        if (!err) {
                err = fuse_fs_statfs(d->next, newpath, stbuf);
                free(newpath);
        }
        return err;
}

static int subdir_flush(const char *path, struct fuse_file_info *fi)
{
        struct subdir *d = subdir_get();
        char *newpath;
        int err = subdir_addpath(d, path, &newpath);
        if (!err) {
                err = fuse_fs_flush(d->next, newpath, fi);
                free(newpath);
        }
        return err;
}

static int subdir_release(const char *path, struct fuse_file_info *fi)
{
        struct subdir *d = subdir_get();
        char *newpath;
        int err = subdir_addpath(d, path, &newpath);
        if (!err) {
                err = fuse_fs_release(d->next, newpath, fi);
                free(newpath);
        }
        return err;
}

static int subdir_fsync(const char *path, int isdatasync,
                        struct fuse_file_info *fi)
{
        struct subdir *d = subdir_get();
        char *newpath;
        int err = subdir_addpath(d, path, &newpath);
        if (!err) {
                err = fuse_fs_fsync(d->next, newpath, isdatasync, fi);
                free(newpath);
        }
        return err;
}

static int subdir_fsyncdir(const char *path, int isdatasync,
                           struct fuse_file_info *fi)
{
        struct subdir *d = subdir_get();
        char *newpath;
        int err = subdir_addpath(d, path, &newpath);
        if (!err) {
                err = fuse_fs_fsyncdir(d->next, newpath, isdatasync, fi);
                free(newpath);
        }
        return err;
}

static int subdir_setxattr(const char *path, const char *name,
                           const char *value, size_t size, int flags)
{
        struct subdir *d = subdir_get();
        char *newpath;
        int err = subdir_addpath(d, path, &newpath);
        if (!err) {
                err = fuse_fs_setxattr(d->next, newpath, name, value, size,
                                       flags);
                free(newpath);
        }
        return err;
}

static int subdir_getxattr(const char *path, const char *name, char *value,
                           size_t size)
{
        struct subdir *d = subdir_get();
        char *newpath;
        int err = subdir_addpath(d, path, &newpath);
        if (!err) {
                err = fuse_fs_getxattr(d->next, newpath, name, value, size);
                free(newpath);
        }
        return err;
}

static int subdir_listxattr(const char *path, char *list, size_t size)
{
        struct subdir *d = subdir_get();
        char *newpath;
        int err = subdir_addpath(d, path, &newpath);
        if (!err) {
                err = fuse_fs_listxattr(d->next, newpath, list, size);
                free(newpath);
        }
        return err;
}

static int subdir_removexattr(const char *path, const char *name)
{
        struct subdir *d = subdir_get();
        char *newpath;
        int err = subdir_addpath(d, path, &newpath);
        if (!err) {
                err = fuse_fs_removexattr(d->next, newpath, name);
                free(newpath);
        }
        return err;
}

static int subdir_lock(const char *path, struct fuse_file_info *fi, int cmd,
                       struct flock *lock)
{
        struct subdir *d = subdir_get();
        char *newpath;
        int err = subdir_addpath(d, path, &newpath);
        if (!err) {
                err = fuse_fs_lock(d->next, newpath, fi, cmd, lock);
                free(newpath);
        }
        return err;
}

static int subdir_flock(const char *path, struct fuse_file_info *fi, int op)
{
        struct subdir *d = subdir_get();
        char *newpath;
        int err = subdir_addpath(d, path, &newpath);
        if (!err) {
                err = fuse_fs_flock(d->next, newpath, fi, op);
                free(newpath);
        }
        return err;
}

static int subdir_bmap(const char *path, size_t blocksize, uint64_t *idx)
{
        struct subdir *d = subdir_get();
        char *newpath;
        int err = subdir_addpath(d, path, &newpath);
        if (!err) {
                err = fuse_fs_bmap(d->next, newpath, blocksize, idx);
                free(newpath);
        }
        return err;
}

static void *subdir_init(struct fuse_conn_info *conn,
                         struct fuse_config *cfg)
{
        struct subdir *d = subdir_get();
        fuse_fs_init(d->next, conn, cfg);
        /* Don't touch cfg->nullpath_ok, we can work with
           either */
        return d;
}

static void subdir_destroy(void *data)
{
        struct subdir *d = data;
        fuse_fs_destroy(d->next);
        free(d->base);
        free(d);
}

static const struct fuse_operations subdir_oper = {
        .destroy        = subdir_destroy,
        .init           = subdir_init,
        .getattr        = subdir_getattr,
        .access         = subdir_access,
        .readlink       = subdir_readlink,
        .opendir        = subdir_opendir,
        .readdir        = subdir_readdir,
        .releasedir     = subdir_releasedir,
        .mknod          = subdir_mknod,
        .mkdir          = subdir_mkdir,
        .symlink        = subdir_symlink,
        .unlink         = subdir_unlink,
        .rmdir          = subdir_rmdir,
        .rename         = subdir_rename,
        .link           = subdir_link,
        .chmod          = subdir_chmod,
        .chown          = subdir_chown,
        .truncate       = subdir_truncate,
        .utimens        = subdir_utimens,
        .create         = subdir_create,
        .open           = subdir_open,
        .read_buf       = subdir_read_buf,
        .write_buf      = subdir_write_buf,
        .statfs         = subdir_statfs,
        .flush          = subdir_flush,
        .release        = subdir_release,
        .fsync          = subdir_fsync,
        .fsyncdir       = subdir_fsyncdir,
        .setxattr       = subdir_setxattr,
        .getxattr       = subdir_getxattr,
        .listxattr      = subdir_listxattr,
        .removexattr    = subdir_removexattr,
        .lock           = subdir_lock,
        .flock          = subdir_flock,
        .bmap           = subdir_bmap,
};

static const struct fuse_opt subdir_opts[] = {
        FUSE_OPT_KEY("-h", 0),
        FUSE_OPT_KEY("--help", 0),
        { "subdir=%s", offsetof(struct subdir, base), 0 },
        { "rellinks", offsetof(struct subdir, rellinks), 1 },
        { "norellinks", offsetof(struct subdir, rellinks), 0 },
        FUSE_OPT_END
};

static void subdir_help(void)
{
        printf(
"    -o subdir=DIR          prepend this directory to all paths (mandatory)\n"
"    -o [no]rellinks        transform absolute symlinks to relative\n");
}

static int subdir_opt_proc(void *data, const char *arg, int key,
                           struct fuse_args *outargs)
{
        (void) data; (void) arg; (void) outargs;

        if (!key) {
                subdir_help();
                return -1;
        }

        return 1;
}

static struct fuse_fs *subdir_new(struct fuse_args *args,
                                  struct fuse_fs *next[])
{
        struct fuse_fs *fs;
        struct subdir *d;

        d = calloc(1, sizeof(struct subdir));
        if (d == NULL) {
                fprintf(stderr, "fuse-subdir: memory allocation failed\n");
                return NULL;
        }

        if (fuse_opt_parse(args, d, subdir_opts, subdir_opt_proc) == -1)
                goto out_free;

        if (!next[0] || next[1]) {
                fprintf(stderr, "fuse-subdir: exactly one next filesystem required\n");
                goto out_free;
        }

        if (!d->base) {
                fprintf(stderr, "fuse-subdir: missing 'subdir' option\n");
                goto out_free;
        }

        if (d->base[0] && d->base[strlen(d->base)-1] != '/') {
                char *tmp = realloc(d->base, strlen(d->base) + 2);
                if (!tmp) {
                        fprintf(stderr, "fuse-subdir: memory allocation failed\n");
                        goto out_free;
                }
                d->base = tmp;
                strcat(d->base, "/");
        }
        d->baselen = strlen(d->base);
        d->next = next[0];
        fs = fuse_fs_new(&subdir_oper, sizeof(subdir_oper), d);
        if (!fs)
                goto out_free;
        return fs;

out_free:
        free(d->base);
        free(d);
        return NULL;
}

FUSE_REGISTER_MODULE(subdir, subdir_new);