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Diffstat (limited to 'src/global/dot_lockfile.c')
| -rw-r--r-- | src/global/dot_lockfile.c | 173 |
1 files changed, 173 insertions, 0 deletions
diff --git a/src/global/dot_lockfile.c b/src/global/dot_lockfile.c new file mode 100644 index 0000000..89a977a --- /dev/null +++ b/src/global/dot_lockfile.c @@ -0,0 +1,173 @@ +/*++ +/* NAME +/* dot_lockfile 3 +/* SUMMARY +/* dotlock file management +/* SYNOPSIS +/* #include <dot_lockfile.h> +/* +/* int dot_lockfile(path, why) +/* const char *path; +/* VSTRING *why; +/* +/* void dot_unlockfile(path) +/* const char *path; +/* DESCRIPTION +/* dot_lockfile() constructs a lock file name by appending ".lock" to +/* \fIpath\fR and creates the named file exclusively. It tries several +/* times and attempts to break stale locks. A negative result value +/* means no lock file could be created. +/* +/* dot_unlockfile() attempts to remove the lock file created by +/* dot_lockfile(). The operation always succeeds, and therefore +/* it preserves the errno value. +/* +/* Arguments: +/* .IP path +/* Name of the file to be locked or unlocked. +/* .IP why +/* A null pointer, or storage for the reason why a lock file could +/* not be created. +/* DIAGNOSTICS +/* dot_lockfile() returns 0 upon success. In case of failure, the +/* result is -1, and the errno variable is set appropriately: +/* EEXIST when a "fresh" lock file already exists; other values as +/* appropriate. +/* CONFIGURATION PARAMETERS +/* deliver_lock_attempts, how many times to try to create a lock +/* deliver_lock_delay, how long to wait between attempts +/* stale_lock_time, when to break a stale lock +/* LICENSE +/* .ad +/* .fi +/* The Secure Mailer license must be distributed with this software. +/* AUTHOR(S) +/* Wietse Venema +/* IBM T.J. Watson Research +/* P.O. Box 704 +/* Yorktown Heights, NY 10598, USA +/*--*/ + +/* System library. */ + +#include "sys_defs.h" +#include <sys/stat.h> +#include <stdlib.h> +#include <unistd.h> +#include <fcntl.h> +#include <errno.h> +#include <time.h> + +/* Utility library. */ + +#include <vstring.h> +#include <stringops.h> +#include <mymalloc.h> +#include <iostuff.h> +#include <warn_stat.h> + +/* Global library. */ + +#include "mail_params.h" +#include "dot_lockfile.h" + +/* Application-specific. */ + +#define MILLION 1000000 + +/* dot_lockfile - create user.lock file */ + +int dot_lockfile(const char *path, VSTRING *why) +{ + char *lock_file; + int count; + struct stat st; + int fd; + int status = -1; + + lock_file = concatenate(path, ".lock", (char *) 0); + + for (count = 1; /* void */ ; count++) { + + /* + * Attempt to create the lock. This code relies on O_EXCL | O_CREAT + * to not follow symlinks. With NFS file systems this operation can + * at the same time succeed and fail with errno of EEXIST. + */ + if ((fd = open(lock_file, O_WRONLY | O_EXCL | O_CREAT, 0)) >= 0) { + close(fd); + status = 0; + break; + } + if (count >= var_flock_tries) + break; + + /* + * We can deal only with "file exists" errors. Any other error means + * we better give up trying. + */ + if (errno != EEXIST) + break; + + /* + * Break the lock when it is too old. Give up when we are unable to + * remove a stale lock. + */ + if (stat(lock_file, &st) == 0) + if (time((time_t *) 0) > st.st_ctime + var_flock_stale) + if (unlink(lock_file) < 0) + if (errno != ENOENT) + break; + + rand_sleep(var_flock_delay * MILLION, var_flock_delay * MILLION / 2); + } + if (status && why) + vstring_sprintf(why, "unable to create lock file %s: %m", lock_file); + + myfree(lock_file); + return (status); +} + +/* dot_unlockfile - remove .lock file */ + +void dot_unlockfile(const char *path) +{ + char *lock_file; + int saved_errno = errno; + + lock_file = concatenate(path, ".lock", (char *) 0); + (void) unlink(lock_file); + myfree(lock_file); + errno = saved_errno; +} + +#ifdef TEST + + /* + * Test program for setting a .lock file. + * + * Usage: dot_lockfile filename + * + * Creates filename.lock and removes it. + */ +#include <msg.h> +#include <vstream.h> +#include <msg_vstream.h> +#include <mail_conf.h> + +int main(int argc, char **argv) +{ + VSTRING *why = vstring_alloc(100); + + msg_vstream_init(argv[0], VSTREAM_ERR); + if (argc != 2) + msg_fatal("usage: %s file-to-be-locked", argv[0]); + mail_conf_read(); + if (dot_lockfile(argv[1], why) < 0) + msg_fatal("%s", vstring_str(why)); + dot_unlockfile(argv[1]); + vstring_free(why); + return (0); +} + +#endif |