+#ifdef EXIM_HAVE_INOTIFY
+/* Add the directory for a filename to the inotify handle, creating that if
+needed. This is enough to see changes to files in that dir.
+Return boolean success.
+
+The word "system" fails, which is on the safe side as we don't know what
+directory it implies nor if the TLS library handles a watch for us.
+
+The string "system,cache" is recognised and explicitly accepted without
+setting a watch. This permits the system CA bundle to be cached even though
+we have no way to tell when it gets modified by an update.
+
+We *might* try to run "openssl version -d" and set watches on the dir
+indicated in its output, plus the "certs" subdir of it (following
+synlimks for both). But this is undocumented even for OpenSSL, and
+who knows what GnuTLS might be doing.
+
+A full set of caching including the CAs takes 35ms output off of the
+server tls_init() (GnuTLS, Fedora 32, 2018-class x86_64 laptop hardware).
+*/
+static BOOL
+tls_set_one_watch(const uschar * filename)
+{
+uschar * s;
+
+if (Ustrcmp(filename, "system,cache") == 0) return TRUE;
+
+if (!(s = Ustrrchr(filename, '/'))) return FALSE;
+s = string_copyn(filename, s - filename);
+DEBUG(D_tls) debug_printf("watch dir '%s'\n", s);
+
+if (inotify_add_watch(tls_watch_fd, CCS s,
+ IN_ONESHOT | IN_CLOSE_WRITE | IN_DELETE | IN_DELETE_SELF
+ | IN_MOVED_FROM | IN_MOVED_TO | IN_MOVE_SELF) >= 0)
+ return TRUE;
+DEBUG(D_tls) debug_printf("add_watch: %s\n", strerror(errno));
+return FALSE;
+}
+
+
+/* Create an inotify facility if needed.
+Then set watches on the dir containing the given file or (optionally)
+list of files. Return boolean success. */
+
+static BOOL
+tls_set_watch(const uschar * filename, BOOL list)
+{
+rmark r;
+BOOL rc = FALSE;
+
+if (tls_watch_fd < 0 && (tls_watch_fd = inotify_init1(O_CLOEXEC)) < 0)
+ {
+ DEBUG(D_tls) debug_printf("inotify_init: %s\n", strerror(errno));
+ return FALSE;
+ }
+
+if (!filename || !*filename) return TRUE;
+
+r = store_mark();
+
+if (list)
+ {
+ int sep = 0;
+ for (uschar * s; s = string_nextinlist(&filename, &sep, NULL, 0); )
+ if (!(rc = tls_set_one_watch(s))) break;
+ }
+else
+ rc = tls_set_one_watch(filename);
+
+store_reset(r);
+return rc;
+}
+
+
+/* Called, after a delay for multiple file ops to get done, from
+the daemon when any of the watches added (above) fire.
+
+Dump the set of watches and arrange to reload cached creds (which
+will set up new watches). */
+
+static void
+tls_watch_triggered(void)
+{
+DEBUG(D_tls) debug_printf("watch triggered\n");
+close(tls_watch_fd);
+tls_watch_fd = -1;
+
+tls_daemon_creds_reload();
+}
+#endif /* EXIM_HAVE_INOTIFY */
+
+
+void
+tls_client_creds_reload(BOOL watch)
+{
+for(transport_instance * t = transports; t; t = t->next)
+ if (Ustrcmp(t->driver_name, "smtp") == 0)
+ {
+ tls_client_creds_invalidate(t);
+ tls_client_creds_init(t, watch);
+ }
+}
+
+static void
+tls_daemon_creds_reload(void)
+{
+tls_server_creds_invalidate();
+tls_server_creds_init();
+
+tls_client_creds_reload(TRUE);
+}
+
+
+/* Utility predicates for use by the per-library code */
+static BOOL
+opt_set_and_noexpand(const uschar * opt)
+{ return opt && *opt && Ustrchr(opt, '$') == NULL; }
+
+static BOOL
+opt_unset_or_noexpand(const uschar * opt)
+{ return !opt || Ustrchr(opt, '$') == NULL; }
+
+
+
+/* Called every time round the daemon loop */
+
+void
+tls_daemon_tick(void)
+{
+tls_per_lib_daemon_tick();
+#ifdef EXIM_HAVE_INOTIFY
+if (tls_watch_trigger_time && time(NULL) >= tls_watch_trigger_time + 5)
+ {
+ tls_watch_trigger_time = 0;
+ tls_watch_triggered();
+ }
+#endif
+}
+
+/* Called once at daemon startup */
+
+void
+tls_daemon_init(void)
+{
+tls_per_lib_daemon_init();
+}
+
+