diff options
author | Ulrich Drepper <drepper@redhat.com> | 1997-08-16 19:45:54 +0000 |
---|---|---|
committer | Ulrich Drepper <drepper@redhat.com> | 1997-08-16 19:45:54 +0000 |
commit | 33e426f9a1219a9b8c369a9b5b3b3f63ab732073 (patch) | |
tree | 191434ed492d705379d50bd00b02e4af1282cda8 | |
parent | 1925e81be540e6855256aac9aad6e261d4431a88 (diff) |
Rewrite lock handling.
-rw-r--r-- | login/utmp_file.c | 287 |
1 files changed, 161 insertions, 126 deletions
diff --git a/login/utmp_file.c b/login/utmp_file.c index 9a5d687291..403b4e5d6a 100644 --- a/login/utmp_file.c +++ b/login/utmp_file.c @@ -18,34 +18,27 @@ 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 <limits.h> #include <stdio.h> -#include <stdlib.h> #include <string.h> #include <unistd.h> #include <utmp.h> -#include <sys/file.h> -#include <sys/stat.h> #include "utmp-private.h" -/* This is the default name. */ -static const char default_file_name[] = _PATH_UTMP; - -/* Current file name. */ -static const char *file_name = (const char *) default_file_name; - /* Descriptor for the file and position. */ -static int file_fd = INT_MIN; +static int file_fd = -1; static off_t file_offset; +/* Cache for the last read entry. */ static struct utmp last_entry; + /* Functions defined here. */ -static int setutent_file (int reset); +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); @@ -53,8 +46,7 @@ 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 utmpname_file (const char *name); - +static int updwtmp_file (const char *file, const struct utmp *utmp); /* Jump table for file functions. */ struct utfuncs __libc_utmp_file_functions = @@ -65,71 +57,49 @@ struct utfuncs __libc_utmp_file_functions = getutline_r_file, pututline_file, endutent_file, - utmpname_file + updwtmp_file }; static int -setutent_file (int reset) +setutent_file (void) { - if (file_fd == INT_MIN) + if (file_fd < 0) { - file_fd = open (file_name, O_RDWR); + file_fd = open (__libc_utmp_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); + file_fd = open (__libc_utmp_file_name, O_RDONLY); if (file_fd == -1) { perror (_("while opening UTMP file")); return 0; } } - file_offset = 0; - -#if _HAVE_UT_TYPE - 0 - /* Make sure the entry won't match. */ - last_entry.ut_type = -1; -#endif } - else if (reset) - { - lseek (file_fd, 0, SEEK_SET); - /* Remember we are at beginning of file. */ - file_offset = 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; + /* Make sure the entry won't match. */ + last_entry.ut_type = -1; #endif - } return 1; } -static void -endutent_file (void) -{ - if (file_fd >= 0) - close (file_fd); - - file_fd = INT_MIN; -} - - static int getutent_r_file (struct utmp *buffer, struct utmp **result) { - int nbytes; + ssize_t nbytes; struct flock fl; /* Information struct for locking. */ - /* Open utmp file if not already done. */ - if (file_fd == INT_MIN) - setutent_file (1); + assert (file_fd >= 0); - if (file_fd == -1 || file_offset == -1l) + if (file_offset == -1l) { /* Not available. */ *result = NULL; @@ -139,12 +109,16 @@ getutent_r_file (struct utmp *buffer, struct utmp **result) /* XXX The following is not perfect. Instead of locking the file itself Marek Michalkiewicz <marekm@i17linuxb.ists.pwr.wroc.pl> suggests to use an extra locking file. */ + /* XXX I think using an extra locking file does not solve the + problems. Instead we should set an alarm, which causes fcntl to + fail, as in ../nis/lckcache.c. + Mark Kettenis <kettenis@phys.uva.nl>. */ /* Try to get the lock. */ memset (&fl, '\0', sizeof (struct flock)); - fl.l_type = F_WRLCK; + fl.l_type = F_RDLCK; fl.l_whence = SEEK_SET; - fcntl (file_fd, F_SETLKW, &fl); + fcntl (file_fd, F_SETLK, &fl); /* Read the next entry. */ nbytes = read (file_fd, &last_entry, sizeof (struct utmp)); @@ -170,49 +144,6 @@ getutent_r_file (struct utmp *buffer, struct utmp **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 -getutline_r_file (const struct utmp *line, struct utmp *buffer, - struct utmp **result) -{ - if (file_fd < 0 || file_offset == -1l) - { - *result = NULL; - return -1; - } - - 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; - return -1; - } - 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; - - return 0; -} - - static int proc_utmp_eq (const struct utmp *entry, const struct utmp *match) { @@ -243,6 +174,15 @@ proc_utmp_eq (const struct utmp *entry, const struct utmp *match) static int internal_getut_r (const struct utmp *id, struct utmp *buffer) { + int result = -1; + struct flock fl; + + /* Try to get the lock. */ + memset (&fl, '\0', sizeof (struct flock)); + fl.l_type = F_RDLCK; + fl.l_whence = SEEK_SET; + fcntl (file_fd, F_SETLKW, &fl); + #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) @@ -258,7 +198,7 @@ internal_getut_r (const struct utmp *id, struct utmp *buffer) { __set_errno (ESRCH); file_offset = -1l; - return -1; + goto unlock_return; } file_offset += sizeof (struct utmp); @@ -280,7 +220,7 @@ internal_getut_r (const struct utmp *id, struct utmp *buffer) { __set_errno (ESRCH); file_offset = -1l; - return -1; + goto unlock_return; } file_offset += sizeof (struct utmp); @@ -289,7 +229,14 @@ internal_getut_r (const struct utmp *id, struct utmp *buffer) } } - return 0; + result = 0; + +unlock_return: + /* And unlock the file. */ + fl.l_type = F_UNLCK; + fcntl (file_fd, F_SETLK, &fl); + + return result; } @@ -299,7 +246,9 @@ static int getutid_r_file (const struct utmp *id, struct utmp *buffer, struct utmp **result) { - if (file_fd < 0 || file_offset == -1l) + assert (file_fd >= 0); + + if (file_offset == -1l) { *result = NULL; return -1; @@ -318,6 +267,64 @@ getutid_r_file (const struct utmp *id, struct utmp *buffer, } +/* 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) +{ + struct flock fl; + + assert (file_fd >= 0); + + if (file_offset == -1l) + { + *result = NULL; + return -1; + } + + /* Try to get the lock. */ + memset (&fl, '\0', sizeof (struct flock)); + fl.l_type = F_RDLCK; + fl.l_whence = SEEK_SET; + fcntl (file_fd, F_SETLKW, &fl); + + 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: + /* And unlock the file. */ + fl.l_type = F_UNLCK; + fcntl (file_fd, F_SETLK, &fl); + + return ((*result == NULL) ? -1 : 0); +} + + static struct utmp * pututline_file (const struct utmp *data) { @@ -326,13 +333,7 @@ pututline_file (const struct utmp *data) struct utmp *pbuf; int found; - if (file_fd < 0) - /* Something went wrong. */ - return NULL; - - if (file_fd == INT_MIN) - /* The file is closed. Open it again. */ - setutent_file (0); + assert (file_fd >= 0); /* Find the correct place to insert the data. */ if (file_offset > 0 @@ -354,7 +355,7 @@ pututline_file (const struct utmp *data) memset (&fl, '\0', sizeof (struct flock)); fl.l_type = F_WRLCK; fl.l_whence = SEEK_SET; - fcntl (file_fd, F_SETLKW, &fl); + fcntl (file_fd, F_SETLK, &fl); if (found < 0) { @@ -397,36 +398,70 @@ pututline_file (const struct utmp *data) unlock_return: /* And unlock the file. */ fl.l_type = F_UNLCK; - fcntl (file_fd, F_SETLKW, &fl); + fcntl (file_fd, F_SETLK, &fl); return pbuf; } +static void +endutent_file (void) +{ + assert (file_fd >= 0); + + close (file_fd); + file_fd = -1; +} + + static int -utmpname_file (const char *name) +updwtmp_file (const char *file, const struct utmp *utmp) { - if (strcmp (name, file_name) != 0) - { - if (strcmp (name, default_file_name) == 0) - { - if (file_name != default_file_name) - free ((char *) file_name); + int result = -1; + struct flock fl; + off_t offset; + int fd; - file_name = default_file_name; - } - else - { - char *new_name = __strdup (name); - if (new_name == NULL) - /* Out of memory. */ - return -1; + /* Open WTMP file. */ + fd = open (file, O_WRONLY); + if (fd < 0) + return -1; + + /* Try to get the lock. */ + memset (&fl, '\0', sizeof (struct flock)); + fl.l_type = F_WRLCK; + fl.l_whence = SEEK_SET; + fcntl (fd, F_SETLK, &fl); - if (file_name != default_file_name) - free ((char *) file_name); + /* 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); - file_name = new_name; - } + if (lseek (fd, 0, SEEK_END) < 0) + goto unlock_return; } - return 0; + + /* 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: + /* And unlock the file. */ + fl.l_type = F_UNLCK; + fcntl (fd, F_SETLKW, &fl); + + /* Close WTMP file. */ + close (fd); + + return result; } |