path: root/usermux/mux.c

/* Root usermux node

   Copyright (C) 1997, 1998, 1999, 2000, 2002, 2008
     Free Software Foundation, Inc.
   Written by Miles Bader <miles@gnu.org>
   This file is part of the GNU Hurd.

   The GNU Hurd is free software; you can redistribute it and/or
   modify it under the terms of the GNU General Public License as
   published by the Free Software Foundation; either version 2, or (at
   your option) any later version.

   The GNU Hurd is distributed in the hope that it will be useful, but
   WITHOUT ANY WARRANTY; without even the implied warranty of
   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
   General Public License for more details.

   You should have received a copy of the GNU General Public License
   along with this program; if not, write to the Free Software
   Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA  02111, USA. */

#include <stddef.h>
#include <string.h>
#include <dirent.h>
#include <pwd.h>
#include <sys/mman.h>

#include "usermux.h"

/* The granularity with which we allocate space to return our result.  */
#define DIRENTS_CHUNK_SIZE	(128*1024)/* Enough for perhaps 8000 names.  */

/* The number seconds we cache our directory return value, in seconds.  */
#define DIRENTS_CACHE_TIME	90

/* Returned directory entries are aligned to blocks this many bytes long.
   Must be a power of two.  */
#define DIRENT_ALIGN 4
#define DIRENT_NAME_OFFS offsetof (struct dirent, d_name)

/* Length is structure before the name + the name + '\0', all
   padded to a four-byte alignment.  */
#define DIRENT_LEN(name_len)						      \
  ((DIRENT_NAME_OFFS + (name_len) + 1 + (DIRENT_ALIGN - 1))		      \
   & ~(DIRENT_ALIGN - 1))

static error_t lookup_user (struct usermux *mux, const char *user,
			    struct node **node); /* fwd decl */

/* [root] Directory operations.  */

/* Lookup NAME in DIR for USER; set *NODE to the found name upon return.  If
   the name was not found, then return ENOENT.  On any error, clear *NODE.
   (*NODE, if found, should be locked, this call should unlock DIR no matter
   what.) */
error_t
netfs_attempt_lookup (struct iouser *user, struct node *dir,
		      char *name, struct node **node)
{
  error_t err;

  if (dir->nn->name)
    err = ENOTDIR;
  else
    err = lookup_user (dir->nn->mux, name, node);

  fshelp_touch (&dir->nn_stat, TOUCH_ATIME, usermux_maptime);

  pthread_mutex_unlock (&dir->lock);

  if (! err)
    pthread_mutex_lock (&(*node)->lock);

  return err;
}

/* Fetch a directory of user entries, as for netfs_get_dirents (that function
   is actually a wrapper that caches the results for a while).  */
static error_t
get_dirents (struct node *dir,
	     int first_entry, int max_entries, char **data,
	     mach_msg_type_number_t *data_len,
	     vm_size_t max_data_len, int *data_entries)
{
  error_t err = 0;

  if (dir->nn->name)
    return ENOTDIR;

  /* Start scanning.  */
  setpwent ();

  /* Find the first entry.  */
  while (first_entry-- > 0)
    if (! getpwent ())
      {
	max_entries = 0;
	break;
      }

  if (max_entries != 0)
    {
      size_t size = (max_data_len == 0 ? DIRENTS_CHUNK_SIZE : max_data_len);

      *data = mmap (0, size, PROT_READ|PROT_WRITE, MAP_ANON, 0, 0);
      err = (data != (void *) -1) ? errno : 0;

      if (! err)
	{
	  struct passwd *pw;
	  char *p = *data;
	  int count = 0;
	  int entry_type =
	    (S_ISLNK (dir->nn->mux->stat_template.st_mode) ? DT_LNK : DT_REG);

	  /* See how much space we need for the result.  */
	  while ((max_entries == -1 || count < max_entries)
		 && (pw = getpwent ()))
	    {
	      struct dirent hdr;
	      size_t name_len = strlen (pw->pw_name);
	      size_t sz = DIRENT_LEN (name_len);

	      if ((p - *data) + sz > size)
		{
		  if (max_data_len > 0)
		    break;
		  else
		    /* Try to grow our return buffer.  */
		    {
		      vm_address_t extension = (vm_address_t)(*data + size);
		      err = vm_allocate (mach_task_self (), &extension,
					 DIRENTS_CHUNK_SIZE, 0);
		      if (err)
			break;
		      size += DIRENTS_CHUNK_SIZE;
		    }
		}

	      hdr.d_namlen = name_len;
	      hdr.d_fileno = pw->pw_uid + USERMUX_FILENO_UID_OFFSET;
	      hdr.d_reclen = sz;
	      hdr.d_type = entry_type;

	      memcpy (p, &hdr, DIRENT_NAME_OFFS);
	      strcpy (p + DIRENT_NAME_OFFS, pw->pw_name);
	      p += sz;

	      count++;
	    }

	  if (err)
	    munmap (*data, size);
	  else
	    {
	      vm_address_t alloc_end = (vm_address_t)(*data + size);
	      vm_address_t real_end = round_page (p);
	      if (alloc_end > real_end)
		munmap ((caddr_t) real_end, alloc_end - real_end);
	      *data_len = p - *data;
	      *data_entries = count;
	    }
	}
    }

  endpwent ();

  return err;
}

/* Implement the netfs_get_directs callback as described in
   <hurd/netfs.h>. */
error_t
netfs_get_dirents (struct iouser *cred, struct node *dir,
		   int first_entry, int max_entries, char **data,
		   mach_msg_type_number_t *data_len,
		   vm_size_t max_data_len, int *data_entries)
{
  error_t err;
  static time_t cache_timestamp = 0;
  static pthread_rwlock_t cache_lock = PTHREAD_RWLOCK_INITIALIZER;
  static char *cached_data = 0;
  static mach_msg_type_number_t cached_data_len = 0;
  static int cached_data_entries = 0;
  struct timeval tv;
  char *first;
  size_t bytes_left, entries_left;

  maptime_read (usermux_maptime, &tv);
  if (tv.tv_sec > cache_timestamp + DIRENTS_CACHE_TIME)
    {
      pthread_rwlock_wrlock (&cache_lock);

      if (cached_data_len > 0)
	/* Free the old cache.  */
	{
	  munmap (cached_data, cached_data_len);
	  cached_data = 0;
	  cached_data_len = 0;
	}

      err = get_dirents (dir, 0, -1, &cached_data, &cached_data_len, 0,
			 &cached_data_entries);

      if (! err)
	cache_timestamp = tv.tv_sec;

      pthread_rwlock_unlock (&cache_lock);

      if (err)
	return err;
    }

  pthread_rwlock_rdlock (&cache_lock);

  first = cached_data;
  bytes_left = cached_data_len;
  entries_left = cached_data_entries;

  while (first_entry > 0)
    {
      struct dirent *e = (struct dirent *)first;

      if (entries_left == 0)
	{
	  pthread_rwlock_unlock (&cache_lock);
	  return EINVAL;
	}

      first += e->d_reclen;
      bytes_left -= e->d_reclen;
      entries_left--;
    }

  if ((max_data_len > 0 && max_data_len < bytes_left)
      || (max_entries > 0 && max_entries < entries_left))
    /* If there's some limit on the return value, we can't just use our
       values representing the whole cache, so we have to explicitly count
       how much we're going to return.  */
    {
      char *lim = first;
      int entries = 0;

      while (entries_left > 0
	     && max_entries > 0
	     && max_data_len > ((struct dirent *)lim)->d_reclen)
	{
	  size_t reclen = ((struct dirent *)lim)->d_reclen;
	  max_data_len -= reclen;
	  max_entries--;
	  entries++;
	  lim += reclen;
	}

      bytes_left = (lim - first);
      entries_left = entries;
    }

  *data_len = bytes_left;
  *data_entries = entries_left;

  *data = mmap (0, bytes_left, PROT_READ|PROT_WRITE, MAP_ANON, 0, 0);
  err = (*data == (void *) -1) ? errno : 0;
  if (! err)
    bcopy (cached_data, *data, bytes_left);

  pthread_rwlock_unlock (&cache_lock);

  fshelp_touch (&dir->nn_stat, TOUCH_ATIME, usermux_maptime);

  return err;
}

/* User lookup.  */

/* Free storage allocated consumed by the user mux name NM, but not the node
   it points to.  */
static void
free_name (struct usermux_name *nm)
{
  free ((char *)nm->name);
  free (nm);
}

/* See if there's an existing entry for the name USER, and if so, return its
   node in NODE with an additional references.  True is returned iff the
   lookup succeeds.  If PURGE is true, then any nodes with a null node are
   removed.  */
static int
lookup_cached (struct usermux *mux, const char *user, int purge,
	       struct node **node)
{
  struct usermux_name *nm = mux->names, **prevl = &mux->names;

  while (nm)
    {
      struct usermux_name *next = nm->next;

      if (strcasecmp (user, nm->name) == 0)
	{
          if (nm->node)
            netfs_nref (nm->node);

	  if (nm->node)
	    {
	      *node = nm->node;
	      return 1;
	    }
	}

      if (purge && !nm->node)
	{
	  *prevl = nm->next;
	  free_name (nm);
	}
      else
	prevl = &nm->next;

      nm = next;
    }

  return 0;
}

/* See if there's an existing entry for the name USER, and if so, return its
   node in NODE, with an additional reference, otherwise, create a new node
   for the user HE as referred to by USER, and return that instead, with a
   single reference.  The type of node created is either a translator node,
   if USER refers to the official name of the user, or a symlink node to the
   official name, if it doesn't.  */
static error_t
lookup_pwent (struct usermux *mux, const char *user, struct passwd *pw,
		struct node **node)
{
  error_t err;
  struct usermux_name *nm = malloc (sizeof (struct usermux_name));

  if (! nm)
    return ENOMEM;

  nm->name = strdup (user);
  err = create_user_node (mux, nm, pw, node);
  if (err)
    {
      free_name (nm);
      return err;
    }

  pthread_rwlock_wrlock (&mux->names_lock);
  if (lookup_cached (mux, user, 1, node))
    /* An entry for USER has already been created between the time we last
       looked and now (which is possible because we didn't lock MUX).
       Just throw away our version and return the one already in the cache.  */
    {
      pthread_rwlock_unlock (&mux->names_lock);
      nm->node->nn->name = 0;	/* Avoid touching the mux name list.  */
      netfs_nrele (nm->node);	/* Free the tentative new node.  */
      free_name (nm);		/* And the name it was under.  */
    }
  else
    /* Enter NM into MUX's list of names, and return the new node.  */
    {
      nm->next = mux->names;
      mux->names = nm;
      pthread_rwlock_unlock (&mux->names_lock);
    }

  return 0;
}

/* Lookup the user USER in MUX, and return the resulting node in NODE, with
   an additional reference, or an error.  */
static error_t
lookup_user (struct usermux *mux, const char *user, struct node **node)
{
  int was_cached;
  struct passwd _pw, *pw;
  char pwent_data[2048];	/* XXX what size should this be???? */

  pthread_rwlock_rdlock (&mux->names_lock);
  was_cached = lookup_cached (mux, user, 0, node);
  pthread_rwlock_unlock (&mux->names_lock);

  if (was_cached)
    return 0;
  else 
    {
      if (getpwnam_r (user, &_pw, pwent_data, sizeof pwent_data, &pw))
	return ENOENT;
      if (pw == NULL)
	return ENOENT;
      return lookup_pwent (mux, user, pw, node);
    }
}

/* This should sync the entire remote filesystem.  If WAIT is set, return
   only after sync is completely finished.  */
error_t
netfs_attempt_syncfs (struct iouser *cred, int wait)
{
  return 0;
}

/* This should attempt a chmod call for the user specified by CRED on node
   NODE, to change the owner to UID and the group to GID. */
error_t
netfs_attempt_chown (struct iouser *cred, struct node *node, uid_t uid, uid_t gid)
{
  if (node->nn->name)
    return EOPNOTSUPP;
  else
    {
      struct usermux *mux = node->nn->mux;
      error_t err = file_chown (mux->underlying, uid, gid);

      if (! err)
	{
	  struct usermux_name *nm;

	  /* Change NODE's owner.  */
	  mux->stat_template.st_uid = uid;
	  mux->stat_template.st_gid = gid;
	  node->nn_stat.st_uid = uid;
	  node->nn_stat.st_gid = gid;

	  /* Change the owner of each leaf node.  */
	  pthread_rwlock_rdlock (&mux->names_lock);
	  for (nm = mux->names; nm; nm = nm->next)
	    if (nm->node)
	      {
		nm->node->nn_stat.st_uid = uid;
		nm->node->nn_stat.st_gid = gid;
	      }
	  pthread_rwlock_unlock (&mux->names_lock);

	  fshelp_touch (&node->nn_stat, TOUCH_CTIME, usermux_maptime);
	}

      return err;
    }
}

/* This should attempt a chauthor call for the user specified by CRED on node
   NODE, to change the author to AUTHOR. */
error_t
netfs_attempt_chauthor (struct iouser *cred, struct node *node, uid_t author)
{
  if (node->nn->name)
    return EOPNOTSUPP;
  else
    {
      struct usermux *mux = node->nn->mux;
      error_t err = file_chauthor (mux->underlying, author);

      if (! err)
	{
	  struct usermux_name *nm;

	  /* Change NODE's owner.  */
	  mux->stat_template.st_author = author;
	  node->nn_stat.st_author = author;

	  /* Change the owner of each leaf node.  */
	  pthread_rwlock_rdlock (&mux->names_lock);
	  for (nm = mux->names; nm; nm = nm->next)
	    if (nm->node)
	      nm->node->nn_stat.st_author = author;
	  pthread_rwlock_unlock (&mux->names_lock);

	  fshelp_touch (&node->nn_stat, TOUCH_CTIME, usermux_maptime);
	}

      return err;
    }
}

/* This should attempt a chmod call for the user specified by CRED on node
   NODE, to change the mode to MODE.  Unlike the normal Unix and Hurd meaning
   of chmod, this function is also used to attempt to change files into other
   types.  If such a transition is attempted which is impossible, then return
   EOPNOTSUPP.  */
error_t
netfs_attempt_chmod (struct iouser *cred, struct node *node, mode_t mode)
{
  mode &= ~S_ITRANS;
  if ((mode & S_IFMT) == 0)
    mode |= (node->nn_stat.st_mode & S_IFMT);
  if (node->nn->name || ((mode & S_IFMT) != (node->nn_stat.st_mode & S_IFMT)))
    return EOPNOTSUPP;
  else
    {
      error_t err = file_chmod (node->nn->mux->underlying, mode & ~S_IFMT);
      if (! err)
	{
	  node->nn_stat.st_mode = mode;
	  fshelp_touch (&node->nn_stat, TOUCH_CTIME, usermux_maptime);
	}
      return err;
    }
}