glibc/sysdeps/generic/utmp_file.c
Ulrich Drepper efea715879 Update.
1998-04-25  Mark Kettenis  <kettenis@phys.uva.nl>

	* sysdeps/generic/utmp_file.c (TIMEOUT): New macro.
	(timeout_handler): New function.
	(LOCK_FILE, UNLOCK_FILE): New macros.
	Implement file locking with timeout.
	(getutent_r_file, internal_getut_r, getutline_r_file,
	pututline_file, updwtmp_file): Use LOCK_FILE and UNLOCK_FILE for
	locking.
1998-05-18 15:26:40 +00:00

472 lines
12 KiB
C

/* Copyright (C) 1996, 1997, 1998 Free Software Foundation, Inc.
This file is part of the GNU C Library.
Contributed by Ulrich Drepper <drepper@cygnus.com>
and Paul Janzen <pcj@primenet.com>, 1996.
The GNU C Library is free software; you can redistribute it and/or
modify it under the terms of the GNU Library General Public License as
published by the Free Software Foundation; either version 2 of the
License, or (at your option) any later version.
The GNU C Library 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
Library General Public License for more details.
You should have received a copy of the GNU Library General Public
License along with the GNU C Library; see the file COPYING.LIB. If not,
write to the Free Software Foundation, Inc., 59 Temple Place - Suite 330,
Boston, MA 02111-1307, USA. */
#include <assert.h>
#include <errno.h>
#include <fcntl.h>
#include <signal.h>
#include <stdio.h>
#include <string.h>
#include <unistd.h>
#include <utmp.h>
#include "utmp-private.h"
/* Descriptor for the file and position. */
static int file_fd = -1;
static off_t file_offset;
/* Cache for the last read entry. */
static struct utmp last_entry;
/* Locking timeout. */
#ifndef TIMEOUT
# define TIMEOUT 1
#endif
/* Do-nothing handler for locking timeout. */
static void timeout_handler (int signum) {};
#define LOCK_FILE(fd, type) \
{ \
struct flock fl; \
struct sigaction action, old_action; \
unsigned int old_timeout; \
\
/* Cancel any existing alarm. */ \
old_timeout = alarm (0); \
\
/* Establish signal handler. */ \
action.sa_handler = timeout_handler; \
sigemptyset (&action.sa_mask); \
action.sa_flags = 0; \
sigaction (SIGALRM, &action, &old_action); \
\
alarm (TIMEOUT); \
\
/* Try to get the lock. */ \
memset (&fl, '\0', sizeof (struct flock)); \
fl.l_type = (type); \
fl.l_whence = SEEK_SET; \
fcntl ((fd), F_SETLKW, &fl)
#define UNLOCK_FILE(fd) \
/* Unlock the file. */ \
fl.l_type = F_UNLCK; \
fcntl ((fd), F_SETLKW, &fl); \
\
/* Reset the signal handler and alarm. */ \
sigaction (SIGALRM, &old_action, NULL); \
alarm (old_timeout); \
} while (0)
/* Functions defined here. */
static int setutent_file (void);
static int getutent_r_file (struct utmp *buffer, struct utmp **result);
static int getutid_r_file (const struct utmp *key, struct utmp *buffer,
struct utmp **result);
static int getutline_r_file (const struct utmp *key, struct utmp *buffer,
struct utmp **result);
static struct utmp *pututline_file (const struct utmp *data);
static void endutent_file (void);
static int updwtmp_file (const char *file, const struct utmp *utmp);
/* Jump table for file functions. */
struct utfuncs __libc_utmp_file_functions =
{
setutent_file,
getutent_r_file,
getutid_r_file,
getutline_r_file,
pututline_file,
endutent_file,
updwtmp_file
};
#ifndef TRANSFORM_UTMP_FILE_NAME
# define TRANSFORM_UTMP_FILE_NAME(file_name) (file_name)
#endif
static int
setutent_file (void)
{
if (file_fd < 0)
{
const char *file_name;
file_name = TRANSFORM_UTMP_FILE_NAME (__libc_utmp_file_name);
file_fd = open (file_name, O_RDWR);
if (file_fd == -1)
{
/* Hhm, read-write access did not work. Try read-only. */
file_fd = open (file_name, O_RDONLY);
if (file_fd == -1)
return 0;
}
}
lseek (file_fd, 0, SEEK_SET);
file_offset = 0;
#if _HAVE_UT_TYPE - 0
/* Make sure the entry won't match. */
last_entry.ut_type = -1;
#endif
return 1;
}
static int
getutent_r_file (struct utmp *buffer, struct utmp **result)
{
ssize_t nbytes;
assert (file_fd >= 0);
if (file_offset == -1l)
{
/* Not available. */
*result = NULL;
return -1;
}
LOCK_FILE (file_fd, F_RDLCK);
/* Read the next entry. */
nbytes = read (file_fd, &last_entry, sizeof (struct utmp));
UNLOCK_FILE (file_fd);
if (nbytes != sizeof (struct utmp))
{
file_offset = -1l;
*result = NULL;
return -1;
}
/* Update position pointer. */
file_offset += sizeof (struct utmp);
memcpy (buffer, &last_entry, sizeof (struct utmp));
*result = buffer;
return 0;
}
static int
proc_utmp_eq (const struct utmp *entry, const struct utmp *match)
{
return
(
#if _HAVE_UT_TYPE - 0
(entry->ut_type == INIT_PROCESS
|| entry->ut_type == LOGIN_PROCESS
|| entry->ut_type == USER_PROCESS
|| entry->ut_type == DEAD_PROCESS)
&&
(match->ut_type == INIT_PROCESS
|| match->ut_type == LOGIN_PROCESS
|| match->ut_type == USER_PROCESS
|| match->ut_type == DEAD_PROCESS)
&&
#endif
#if _HAVE_UT_ID - 0
(entry->ut_id[0] && match->ut_id[0]
? strncmp (entry->ut_id, match->ut_id, sizeof match->ut_id) == 0
: strncmp (entry->ut_line, match->ut_line, sizeof match->ut_line) == 0)
#else
strncmp (entry->ut_line, match->ut_line, sizeof match->ut_line) == 0
#endif
);
}
static int
internal_getut_r (const struct utmp *id, struct utmp *buffer)
{
int result = -1;
LOCK_FILE (file_fd, F_RDLCK);
#if _HAVE_UT_TYPE - 0
if (id->ut_type == RUN_LVL || id->ut_type == BOOT_TIME
|| id->ut_type == OLD_TIME || id->ut_type == NEW_TIME)
{
/* Search for next entry with type RUN_LVL, BOOT_TIME,
OLD_TIME, or NEW_TIME. */
while (1)
{
/* Read the next entry. */
if (read (file_fd, buffer, sizeof (struct utmp))
!= sizeof (struct utmp))
{
__set_errno (ESRCH);
file_offset = -1l;
goto unlock_return;
}
file_offset += sizeof (struct utmp);
if (id->ut_type == buffer->ut_type)
break;
}
}
else
#endif /* _HAVE_UT_TYPE */
{
/* Search for the next entry with the specified ID and with type
INIT_PROCESS, LOGIN_PROCESS, USER_PROCESS, or DEAD_PROCESS. */
while (1)
{
/* Read the next entry. */
if (read (file_fd, buffer, sizeof (struct utmp))
!= sizeof (struct utmp))
{
__set_errno (ESRCH);
file_offset = -1l;
goto unlock_return;
}
file_offset += sizeof (struct utmp);
if (proc_utmp_eq (buffer, id))
break;
}
}
result = 0;
unlock_return:
UNLOCK_FILE (file_fd);
return result;
}
/* For implementing this function we don't use the getutent_r function
because we can avoid the reposition on every new entry this way. */
static int
getutid_r_file (const struct utmp *id, struct utmp *buffer,
struct utmp **result)
{
assert (file_fd >= 0);
if (file_offset == -1l)
{
*result = NULL;
return -1;
}
if (internal_getut_r (id, &last_entry) < 0)
{
*result = NULL;
return -1;
}
memcpy (buffer, &last_entry, sizeof (struct utmp));
*result = buffer;
return 0;
}
/* For implementing this function we don't use the getutent_r function
because we can avoid the reposition on every new entry this way. */
static int
getutline_r_file (const struct utmp *line, struct utmp *buffer,
struct utmp **result)
{
assert (file_fd >= 0);
if (file_offset == -1l)
{
*result = NULL;
return -1;
}
LOCK_FILE (file_fd, F_RDLCK);
while (1)
{
/* Read the next entry. */
if (read (file_fd, &last_entry, sizeof (struct utmp))
!= sizeof (struct utmp))
{
__set_errno (ESRCH);
file_offset = -1l;
*result = NULL;
goto unlock_return;
}
file_offset += sizeof (struct utmp);
/* Stop if we found a user or login entry. */
if (
#if _HAVE_UT_TYPE - 0
(last_entry.ut_type == USER_PROCESS
|| last_entry.ut_type == LOGIN_PROCESS)
&&
#endif
!strncmp (line->ut_line, last_entry.ut_line, sizeof line->ut_line))
break;
}
memcpy (buffer, &last_entry, sizeof (struct utmp));
*result = buffer;
unlock_return:
UNLOCK_FILE (file_fd);
return ((*result == NULL) ? -1 : 0);
}
static struct utmp *
pututline_file (const struct utmp *data)
{
struct utmp buffer;
struct utmp *pbuf;
int found;
assert (file_fd >= 0);
/* Find the correct place to insert the data. */
if (file_offset > 0
&& (
#if _HAVE_UT_TYPE - 0
(last_entry.ut_type == data->ut_type
&& (last_entry.ut_type == RUN_LVL
|| last_entry.ut_type == BOOT_TIME
|| last_entry.ut_type == OLD_TIME
|| last_entry.ut_type == NEW_TIME))
||
#endif
proc_utmp_eq (&last_entry, data)))
found = 1;
else
found = internal_getut_r (data, &buffer);
LOCK_FILE (file_fd, F_WRLCK);
if (found < 0)
{
/* We append the next entry. */
file_offset = lseek (file_fd, 0, SEEK_END);
if (file_offset % sizeof (struct utmp) != 0)
{
file_offset -= file_offset % sizeof (struct utmp);
__ftruncate (file_fd, file_offset);
if (lseek (file_fd, 0, SEEK_END) < 0)
{
pbuf = NULL;
goto unlock_return;
}
}
}
else
{
/* We replace the just read entry. */
file_offset -= sizeof (struct utmp);
lseek (file_fd, file_offset, SEEK_SET);
}
/* Write the new data. */
if (write (file_fd, data, sizeof (struct utmp)) != sizeof (struct utmp))
{
/* If we appended a new record this is only partially written.
Remove it. */
if (found < 0)
(void) __ftruncate (file_fd, file_offset);
pbuf = NULL;
}
else
{
file_offset += sizeof (struct utmp);
pbuf = (struct utmp *) data;
}
unlock_return:
UNLOCK_FILE (file_fd);
return pbuf;
}
static void
endutent_file (void)
{
assert (file_fd >= 0);
close (file_fd);
file_fd = -1;
}
static int
updwtmp_file (const char *file, const struct utmp *utmp)
{
int result = -1;
off_t offset;
int fd;
/* Open WTMP file. */
fd = open (file, O_WRONLY);
if (fd < 0)
return -1;
LOCK_FILE (fd, F_WRLCK);
/* Remember original size of log file. */
offset = lseek (fd, 0, SEEK_END);
if (offset % sizeof (struct utmp) != 0)
{
offset -= offset % sizeof (struct utmp);
__ftruncate (fd, offset);
if (lseek (fd, 0, SEEK_END) < 0)
goto unlock_return;
}
/* Write the entry. If we can't write all the bytes, reset the file
size back to the original size. That way, no partial entries
will remain. */
if (write (fd, utmp, sizeof (struct utmp)) != sizeof (struct utmp))
{
__ftruncate (fd, offset);
goto unlock_return;
}
result = 0;
unlock_return:
UNLOCK_FILE (fd);
/* Close WTMP file. */
close (fd);
return result;
}