Minor bug fixes for socket.c

[~andy/fetchmail] / lock.c

diff --git a/lock.c b/lock.c
index e69de29bb2d1d6434b8b29ae775ad8c2e48c5391..213969f1f012f323c470ceb3a1e6b1c1aec43ffa 100644 (file)
--- a/lock.c
+++ b/lock.c
@@ -0,0 +1,180 @@
+/**
+ * \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 */