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/*
* gensio - A library for abstracting stream I/O
* Copyright (C) 2018 Corey Minyard <minyard@acm.org>
*
* SPDX-License-Identifier: LGPL-2.1-only
*/
#include "config.h"
#include "uucplock.h"
bool gensio_uucp_locking_enabled = true;
#ifdef USE_UUCP_LOCKING
#include <string.h>
#include <stdio.h>
#include <stdlib.h>
#include <stdint.h>
#include <unistd.h>
#include <fcntl.h>
#include <errno.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <signal.h>
static char *uucp_lck_dir = "/var/lock/";
static char *dev_prefix = "/dev/";
static size_t
uucp_fname_lock_size(char *devname)
{
size_t dev_prefix_len = strlen(dev_prefix);
if (strncmp(dev_prefix, devname, dev_prefix_len) == 0)
devname += dev_prefix_len;
/*
* Format is "/var/lock/LCK..<devname>". The 6 is for
* the "LCK.." and the final nil char.
*/
return 6 + strlen(uucp_lck_dir) + strlen(devname);
}
static void
uucp_fname_lock(char *buf, char *devname)
{
size_t i, dev_prefix_len = strlen(dev_prefix);
if (strncmp(dev_prefix, devname, dev_prefix_len) == 0)
devname += dev_prefix_len;
sprintf(buf, "%sLCK..%s", uucp_lck_dir, devname);
for (i = strlen(uucp_lck_dir); buf[i]; i++) {
if (buf[i] == '/')
buf[i] = '_';
}
}
void
uucp_rm_lock(char *devname)
{
char *lck_file;
if (!gensio_uucp_locking_enabled) return;
lck_file = malloc(uucp_fname_lock_size(devname));
if (lck_file == NULL) {
return;
}
uucp_fname_lock(lck_file, devname);
unlink(lck_file);
free(lck_file);
}
static int
write_full(int fd, char *data, size_t count)
{
ssize_t written;
restart:
while ((written = write(fd, data, count)) > 0) {
data += written;
count -= written;
}
if (written < 0) {
if (errno == EAGAIN)
goto restart;
return -1;
}
return 0;
}
int
uucp_mk_lock(char *devname)
{
struct stat stt;
int pid = -1;
if (!gensio_uucp_locking_enabled)
return 0;
if (stat(uucp_lck_dir, &stt) == 0) { /* is lock file directory present? */
char *lck_file;
union {
uint32_t ival;
char str[64];
} buf;
int fd;
lck_file = malloc(uucp_fname_lock_size(devname));
if (lck_file == NULL)
return -1;
uucp_fname_lock(lck_file, devname);
pid = 0;
if ((fd = open(lck_file, O_RDONLY)) >= 0) {
int n;
n = read(fd, &buf, sizeof(buf) - 1);
close(fd);
if (n == 4) /* Kermit-style lockfile. */
pid = buf.ival;
else if (n > 0) { /* Ascii lockfile. */
buf.str[n] = '\0';
sscanf(buf.str, "%10d", &pid);
}
if (pid > 0 && kill((pid_t)pid, 0) < 0 && errno == ESRCH) {
/* death lockfile - remove it */
unlink(lck_file);
pid = 0;
} else
pid = 1;
}
if (pid == 0) {
int mask;
mask = umask(022);
fd = open(lck_file, O_WRONLY | O_CREAT | O_EXCL, 0666);
umask(mask);
if (fd >= 0) {
ssize_t rv;
snprintf(buf.str, sizeof(buf), "%10ld\n",
(long)getpid());
rv = write_full(fd, buf.str, strlen(buf.str));
close(fd);
if (rv < 0) {
pid = -1;
unlink(lck_file);
}
} else {
pid = -1;
}
}
free(lck_file);
}
return pid;
}
#else
void
uucp_rm_lock(char *devname)
{
}
int
uucp_mk_lock(char *devname)
{
return 0;
}
#endif /* USE_UUCP_LOCKING */
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