mergerfs/libfuse/lib/cuse_lowlevel.c

/*
  CUSE: Character device in Userspace
  Copyright (C) 2008       SUSE Linux Products GmbH
  Copyright (C) 2008       Tejun Heo <teheo@suse.de>

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

#include "cuse_lowlevel.h"
#include "fuse_kernel.h"
#include "fuse_i.h"
#include "fuse_opt.h"
#include "fuse_misc.h"

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

struct cuse_data {
  struct cuse_lowlevel_ops	clop;
  unsigned			max_read;
  unsigned			dev_major;
  unsigned			dev_minor;
  unsigned			flags;
  unsigned			dev_info_len;
  char				dev_info[];
};

static struct cuse_lowlevel_ops *req_clop(fuse_req_t req)
{
  return &req->f->cuse_data->clop;
}

static void cuse_fll_open(fuse_req_t req, fuse_ino_t ino,
			  struct fuse_file_info *fi)
{
  (void)ino;
  req_clop(req)->open(req, fi);
}

static void cuse_fll_read(fuse_req_t req, fuse_ino_t ino, size_t size,
			  off_t off, struct fuse_file_info *fi)
{
  (void)ino;
  req_clop(req)->read(req, size, off, fi);
}

static void cuse_fll_write(fuse_req_t req, fuse_ino_t ino, const char *buf,
			   size_t size, off_t off, struct fuse_file_info *fi)
{
  (void)ino;
  req_clop(req)->write(req, buf, size, off, fi);
}

static void cuse_fll_flush(fuse_req_t req, fuse_ino_t ino,
			   struct fuse_file_info *fi)
{
  (void)ino;
  req_clop(req)->flush(req, fi);
}

static void cuse_fll_release(fuse_req_t req, fuse_ino_t ino,
			     struct fuse_file_info *fi)
{
  (void)ino;
  req_clop(req)->release(req, fi);
}

static void cuse_fll_fsync(fuse_req_t req, fuse_ino_t ino, int datasync,
			   struct fuse_file_info *fi)
{
  (void)ino;
  req_clop(req)->fsync(req, datasync, fi);
}

static void cuse_fll_ioctl(fuse_req_t req, fuse_ino_t ino, int cmd, void *arg,
                           struct fuse_file_info *fi, unsigned int flags,
                           const void *in_buf, size_t in_bufsz, size_t out_bufsz)
{
  (void)ino;
  req_clop(req)->ioctl(req, cmd, arg, fi, flags, in_buf, in_bufsz,
                       out_bufsz);
}

static void cuse_fll_poll(fuse_req_t req, fuse_ino_t ino,
			  struct fuse_file_info *fi, struct fuse_pollhandle *ph)
{
  (void)ino;
  req_clop(req)->poll(req, fi, ph);
}

static size_t cuse_pack_info(int argc, const char **argv, char *buf)
{
  size_t size = 0;
  int i;

  for (i = 0; i < argc; i++) {
    size_t len;

    len = strlen(argv[i]) + 1;
    size += len;
    if (buf) {
      memcpy(buf, argv[i], len);
      buf += len;
    }
  }

  return size;
}

static struct cuse_data *cuse_prep_data(const struct cuse_info *ci,
					const struct cuse_lowlevel_ops *clop)
{
  struct cuse_data *cd;
  size_t dev_info_len;

  dev_info_len = cuse_pack_info(ci->dev_info_argc, ci->dev_info_argv,
                                NULL);

  if (dev_info_len > CUSE_INIT_INFO_MAX) {
    fprintf(stderr, "cuse: dev_info (%zu) too large, limit=%u\n",
            dev_info_len, CUSE_INIT_INFO_MAX);
    return NULL;
  }

  cd = calloc(1, sizeof(*cd) + dev_info_len);
  if (!cd) {
    fprintf(stderr, "cuse: failed to allocate cuse_data\n");
    return NULL;
  }

  memcpy(&cd->clop, clop, sizeof(cd->clop));
  cd->max_read = 131072;
  cd->dev_major = ci->dev_major;
  cd->dev_minor = ci->dev_minor;
  cd->dev_info_len = dev_info_len;
  cd->flags = ci->flags;
  cuse_pack_info(ci->dev_info_argc, ci->dev_info_argv, cd->dev_info);

  return cd;
}

struct fuse_session *cuse_lowlevel_new(struct fuse_args *args,
				       const struct cuse_info *ci,
				       const struct cuse_lowlevel_ops *clop,
				       void *userdata)
{
  struct fuse_lowlevel_ops lop;
  struct cuse_data *cd;
  struct fuse_session *se;
  struct fuse_ll *ll;

  cd = cuse_prep_data(ci, clop);
  if (!cd)
    return NULL;

  memset(&lop, 0, sizeof(lop));
  lop.init	= clop->init;
  lop.destroy	= clop->destroy;
  lop.open	= clop->open		? cuse_fll_open		: NULL;
  lop.read	= clop->read		? cuse_fll_read		: NULL;
  lop.write	= clop->write		? cuse_fll_write	: NULL;
  lop.flush	= clop->flush		? cuse_fll_flush	: NULL;
  lop.release	= clop->release		? cuse_fll_release	: NULL;
  lop.fsync	= clop->fsync		? cuse_fll_fsync	: NULL;
  lop.ioctl	= clop->ioctl		? cuse_fll_ioctl	: NULL;
  lop.poll	= clop->poll		? cuse_fll_poll		: NULL;

  se = fuse_lowlevel_new_common(args, &lop, sizeof(lop), userdata);
  if (!se) {
    free(cd);
    return NULL;
  }
  ll = se->data;
  ll->cuse_data = cd;

  return se;
}

static int cuse_reply_init(fuse_req_t req, struct cuse_init_out *arg,
			   char *dev_info, unsigned dev_info_len)
{
  struct iovec iov[3];

  iov[1].iov_base = arg;
  iov[1].iov_len = sizeof(struct cuse_init_out);
  iov[2].iov_base = dev_info;
  iov[2].iov_len = dev_info_len;

  return fuse_send_reply_iov_nofree(req, 0, iov, 3);
}

void cuse_lowlevel_init(fuse_req_t req, fuse_ino_t nodeid, const void *inarg)
{
  struct fuse_init_in *arg = (struct fuse_init_in *) inarg;
  struct cuse_init_out outarg;
  struct fuse_ll *f = req->f;
  struct cuse_data *cd = f->cuse_data;
  size_t bufsize = fuse_chan_bufsize(req->ch);
  struct cuse_lowlevel_ops *clop = req_clop(req);

  (void) nodeid;
  if (f->debug) {
    fprintf(stderr, "CUSE_INIT: %u.%u\n", arg->major, arg->minor);
    fprintf(stderr, "flags=0x%08x\n", arg->flags);
  }
  f->conn.proto_major = arg->major;
  f->conn.proto_minor = arg->minor;
  f->conn.capable = 0;
  f->conn.want = 0;

  if (arg->major < 7) {
    fprintf(stderr, "cuse: unsupported protocol version: %u.%u\n",
            arg->major, arg->minor);
    fuse_reply_err(req, EPROTO);
    return;
  }

  if (bufsize < FUSE_MIN_READ_BUFFER) {
    fprintf(stderr, "cuse: warning: buffer size too small: %zu\n",
            bufsize);
    bufsize = FUSE_MIN_READ_BUFFER;
  }

  bufsize -= 4096;
  if (bufsize < f->conn.max_write)
    f->conn.max_write = bufsize;

  f->got_init = 1;
  if (f->op.init)
    f->op.init(f->userdata, &f->conn);

  memset(&outarg, 0, sizeof(outarg));
  outarg.major = FUSE_KERNEL_VERSION;
  outarg.minor = FUSE_KERNEL_MINOR_VERSION;
  outarg.flags = cd->flags;
  outarg.max_read = cd->max_read;
  outarg.max_write = f->conn.max_write;
  outarg.dev_major = cd->dev_major;
  outarg.dev_minor = cd->dev_minor;

  if (f->debug) {
    fprintf(stderr, "   CUSE_INIT: %u.%u\n",
            outarg.major, outarg.minor);
    fprintf(stderr, "   flags=0x%08x\n", outarg.flags);
    fprintf(stderr, "   max_read=0x%08x\n", outarg.max_read);
    fprintf(stderr, "   max_write=0x%08x\n", outarg.max_write);
    fprintf(stderr, "   dev_major=%u\n", outarg.dev_major);
    fprintf(stderr, "   dev_minor=%u\n", outarg.dev_minor);
    fprintf(stderr, "   dev_info: %.*s\n", cd->dev_info_len,
            cd->dev_info);
  }

  cuse_reply_init(req, &outarg, cd->dev_info, cd->dev_info_len);

  if (clop->init_done)
    clop->init_done(f->userdata);

  fuse_free_req(req);
}

struct fuse_session *cuse_lowlevel_setup(int argc, char *argv[],
					 const struct cuse_info *ci,
					 const struct cuse_lowlevel_ops *clop,
					 int *multithreaded, void *userdata)
{
  const char *devname = "/dev/cuse";
  static const struct fuse_opt kill_subtype_opts[] = {
    FUSE_OPT_KEY("subtype=",  FUSE_OPT_KEY_DISCARD),
    FUSE_OPT_END
  };
  struct fuse_args args = FUSE_ARGS_INIT(argc, argv);
  struct fuse_session *se;
  struct fuse_chan *ch;
  int fd;
  int foreground;
  int res;

  res = fuse_parse_cmdline(&args, NULL, multithreaded, &foreground);
  if (res == -1)
    goto err_args;

  res = fuse_opt_parse(&args, NULL, kill_subtype_opts, NULL);
  if (res == -1)
    goto err_args;

  /*
   * Make sure file descriptors 0, 1 and 2 are open, otherwise chaos
   * would ensue.
   */
  do {
    fd = open("/dev/null", O_RDWR);
    if (fd > 2)
      close(fd);
  } while (fd >= 0 && fd <= 2);

  se = cuse_lowlevel_new(&args, ci, clop, userdata);
  fuse_opt_free_args(&args);
  if (se == NULL)
    goto err_args;

  fd = open(devname, O_RDWR);
  if (fd == -1) {
    if (errno == ENODEV || errno == ENOENT)
      fprintf(stderr, "cuse: device not found, try 'modprobe cuse' first\n");
    else
      fprintf(stderr, "cuse: failed to open %s: %s\n",
              devname, strerror(errno));
    goto err_se;
  }

  ch = fuse_kern_chan_new(fd);
  if (!ch) {
    close(fd);
    goto err_se;
  }

  fuse_session_add_chan(se, ch);

  res = fuse_set_signal_handlers(se);
  if (res == -1)
    goto err_se;

  res = fuse_daemonize(foreground);
  if (res == -1)
    goto err_sig;

  return se;

 err_sig:
  fuse_remove_signal_handlers(se);
 err_se:
  fuse_session_destroy(se);
 err_args:
  fuse_opt_free_args(&args);
  return NULL;
}

void cuse_lowlevel_teardown(struct fuse_session *se)
{
  fuse_remove_signal_handlers(se);
  fuse_session_destroy(se);
}

int cuse_lowlevel_main(int argc, char *argv[], const struct cuse_info *ci,
		       const struct cuse_lowlevel_ops *clop, void *userdata)
{
  struct fuse_session *se;
  int multithreaded;
  int res;

  se = cuse_lowlevel_setup(argc, argv, ci, clop, &multithreaded,
                           userdata);
  if (se == NULL)
    return 1;

  if (multithreaded)
    res = fuse_session_loop_mt(se, 0);
  else
    res = fuse_session_loop(se);

  cuse_lowlevel_teardown(se);
  if (res == -1)
    return 1;

  return 0;
}