+/**
+ * \file lock.c cross-platform concurrency locking for fetchmail
+ *
+ * For license terms, see the file COPYING in this directory.
+ */
+#include "config.h"
+
+#include <stdio.h>
+#ifdef HAVE_STRING_H
+#include <string.h> /* strcat() */
+#endif
+#if defined(STDC_HEADERS)
+#include <stdlib.h>
+#endif
+#if defined(HAVE_UNISTD_H)
+#include <unistd.h>
+#endif
+#include <errno.h>
+#include <fcntl.h>
+#include <signal.h>
+
+#include "fetchmail.h"
+#include "i18n.h"
+#include "lock.h"
+
+static char *lockfile; /** name of lockfile */
+static int lock_acquired; /** flag if have we acquired a lock */
+
+void fm_lock_setup(struct runctl *ctl)
+/* set up the global lockfile name */
+{
+ /* set up to do lock protocol */
+ const char *const FETCHMAIL_PIDFILE="fetchmail.pid";
+
+ /* command-line option override */
+ if (ctl->pidfile) {
+ lockfile = xstrdup(ctl->pidfile);
+ return;
+ }
+
+ /* defaults */
+ if (getuid() == ROOT_UID) {
+ lockfile = (char *)xmalloc(strlen(PID_DIR)
+ + strlen(FETCHMAIL_PIDFILE) + 2); /* 2: "/" and NUL */
+ strcpy(lockfile, PID_DIR);
+ strcat(lockfile, "/");
+ strcat(lockfile, FETCHMAIL_PIDFILE);
+ } else {
+ lockfile = (char *)xmalloc(strlen(fmhome)
+ + strlen(FETCHMAIL_PIDFILE) + 3); /* 3: "/", "." and NUL */
+ strcpy(lockfile, fmhome);
+ strcat(lockfile, "/");
+ if (fmhome == home)
+ strcat(lockfile, ".");
+ strcat(lockfile, FETCHMAIL_PIDFILE);
+ }
+}
+
+static void unlockit(void)
+/* must-do actions for exit (but we can't count on being able to do malloc) */
+{
+ if (lockfile && lock_acquired)
+ unlink(lockfile);
+}
+
+void fm_lock_dispose(void)
+/* arrange for a lock to be removed on process exit */
+{
+#ifdef HAVE_ATEXIT
+ atexit(unlockit);
+#endif
+}
+
+int fm_lock_state(void)
+{
+ long pid;
+ int st;
+ FILE *lockfp;
+ int bkgd = FALSE;
+
+ if ((lockfp = fopen(lockfile, "r")) != NULL)
+ {
+ int args = fscanf(lockfp, "%ld %d", &pid, &st);
+ bkgd = (args == 2);
+
+ if (ferror(lockfp)) {
+ fprintf(stderr, GT_("fetchmail: error reading lockfile \"%s\": %s\n"),
+ lockfile, strerror(errno));
+ fclose(lockfp); /* not checking should be safe, file mode was "r" */
+ exit(PS_EXCLUDE);
+ }
+ fclose(lockfp); /* not checking should be safe, file mode was "r" */
+
+ if (args == EOF || args == 0 || kill(pid, 0) == -1) {
+ /* ^ could not read PID || process does not exist */
+ /* => lockfile is stale, unlink it */
+ pid = 0;
+ fprintf(stderr,GT_("fetchmail: removing stale lockfile\n"));
+ if (unlink(lockfile)) {
+ if (errno != ENOENT) {
+ perror(lockfile);
+ /* we complain but we don't exit; it might be
+ * writable for us, but in a directory we cannot
+ * write to. This means we can write the new PID to
+ * the file. Truncate to be safe in case the PID is
+ * recycled by another process later.
+ * \bug we should use fcntl() style locks or
+ * something else instead in a future release. */
+ if (truncate(lockfile, (off_t)0)) {
+ /* but if we cannot truncate the file either,
+ * assume that we cannot write to it later,
+ * complain and quit. */
+ perror(lockfile);
+ exit(PS_EXCLUDE);
+ }
+ }
+ }
+ }
+ } else {
+ pid = 0;
+ if (errno != ENOENT) {
+ fprintf(stderr, GT_("fetchmail: error opening lockfile \"%s\": %s\n"),
+ lockfile, strerror(errno));
+ exit(PS_EXCLUDE);
+ }
+ }
+
+ return(bkgd ? -pid : pid);
+}
+
+void fm_lock_assert(void)
+/* assert that we already possess a lock */
+{
+ lock_acquired = TRUE;
+}
+
+void fm_lock_or_die(void)
+/* get a lock on a given host or exit */
+{
+ int fd;
+ char tmpbuf[50];
+
+ if (!lock_acquired) {
+ int e = 0;
+
+ if ((fd = open(lockfile, O_WRONLY|O_CREAT|O_EXCL, 0666)) != -1) {
+ ssize_t wr;
+
+ snprintf(tmpbuf, sizeof(tmpbuf), "%ld\n", (long)getpid());
+ wr = write(fd, tmpbuf, strlen(tmpbuf));
+ if (wr == -1 || (size_t)wr != strlen(tmpbuf))
+ e = 1;
+ if (run.poll_interval)
+ {
+ snprintf(tmpbuf, sizeof(tmpbuf), "%d\n", run.poll_interval);
+ wr = write(fd, tmpbuf, strlen(tmpbuf));
+ if (wr == -1 || (size_t)wr != strlen(tmpbuf))
+ e = 1;
+ }
+ if (fsync(fd)) e = 1;
+ if (close(fd)) e = 1;
+ } else {
+ e = 1;
+ }
+ if (e == 0) {
+ lock_acquired = TRUE;
+ } else {
+ perror(lockfile);
+ fprintf(stderr, GT_("fetchmail: lock creation failed.\n"));
+ exit(PS_EXCLUDE);
+ }
+ }
+}
+
+void fm_lock_release(void)
+/* release a lock on a given host */
+{
+ unlink(lockfile);
+}
+/* lock.c ends here */