Fix repeated dependency cache rebuild if clock skewed

rc_deptree_update_needed would return early as soon as it found
any file newer than the existing dependency cache.  Unfortunately,
the first file found may not be the newest one there; so the
clock skew workaround in rc-misc:_rc_deptree_load would be given
a timestamp that was still too old.

This fix forces a full scan of all relevant files, so as to
ensure that we return a timestamp that will allow the clock skew
fix to operate.   The runtime cost is no worse than the case where
the cache is up to date (ie. we must check every possible file).

This fixes #161.

src/librc/librc-depend.c

@@ -542,54 +542,43 @@ rc_deptree_order(const RC_DEPTREE *deptree, const char *runlevel, int options)
 }
 librc_hidden_def(rc_deptree_order)
 
+
+/* Given a time, recurse the target path to find out if there are
+   any older (or newer) files.   If false, sets the time to the
+   oldest (or newest) found.
+*/
 static bool
-mtime_check(const char *source, const char *target, bool newer,
+deep_mtime_check(const char *target, bool newer,
 	    time_t *rel, char *file)
 {
 	struct stat buf;
-	time_t mtime;
 	bool retval = true;
 	DIR *dp;
 	struct dirent *d;
 	char path[PATH_MAX];
 	int serrno = errno;
 
-	/* We have to exist */
-	if (stat(source, &buf) != 0)
-		return false;
-	mtime = buf.st_mtime;
-
 	/* If target does not exist, return true to mimic shell test */
 	if (stat(target, &buf) != 0)
 		return true;
 
 	if (newer) {
-		if (mtime < buf.st_mtime) {
-			if (rel == NULL)
-				return false;
-			retval = false;
-		}
-		if (rel != NULL) {
 		if (*rel < buf.st_mtime) {
+			retval = false;
+
 			if (file)
 				strlcpy(file, target, PATH_MAX);
 			*rel = buf.st_mtime;
 		}
-		}
 	} else {
-		if (mtime > buf.st_mtime) {
-			if (rel == NULL)
-				return false;
-			retval = false;
-		}
-		if (rel != NULL) {
 		if (*rel > buf.st_mtime) {
+			retval = false;
+
 			if (file)
 				strlcpy(file, target, PATH_MAX);
 			*rel = buf.st_mtime;
 		}
 	}
-	}
 
 	/* If not a dir then reset errno */
 	if (!(dp = opendir(target))) {
@@ -602,16 +591,38 @@ mtime_check(const char *source, const char *target, bool newer,
 		if (d->d_name[0] == '.')
 			continue;
 		snprintf(path, sizeof(path), "%s/%s", target, d->d_name);
-		if (!mtime_check(source, path, newer, rel, file)) {
+		if (!deep_mtime_check(path, newer, rel, file)) {
 			retval = false;
-			if (rel == NULL)
-				break;
 		}
 	}
 	closedir(dp);
 	return retval;
 }
 
+/* Recursively check if target is older/newer than source.
+ * If false, return the filename and most different time (if
+ * the return value arguments are non-null).
+ */
+static bool
+mtime_check(const char *source, const char *target, bool newer,
+	    time_t *rel, char *file)
+{
+	struct stat buf;
+	time_t mtime;
+	bool retval = true;
+
+	/* We have to exist */
+	if (stat(source, &buf) != 0)
+		return false;
+	mtime = buf.st_mtime;
+
+    retval = deep_mtime_check(target,newer,&mtime,file);
+    if (rel) {
+        *rel = mtime;
+    }
+    return retval;
+}
+
 bool
 rc_newer_than(const char *source, const char *target,
 	      time_t *newest, char *file)
@@ -670,6 +681,8 @@ rc_deptree_update_needed(time_t *newest, char *file)
 	RC_STRINGLIST *config;
 	RC_STRING *s;
 	int i;
+	struct stat buf;
+	time_t mtime;
 
 	/* Create base directories if needed */
 	for (i = 0; depdirs[i]; i++)
@@ -677,42 +690,48 @@ rc_deptree_update_needed(time_t *newest, char *file)
 			fprintf(stderr, "mkdir `%s': %s\n", depdirs[i], strerror(errno));
 
 	/* Quick test to see if anything we use has changed and we have
-	 * data in our deptree */
+	 * data in our deptree. */
-	if (!existss(RC_DEPTREE_CACHE))
+
-		return true;
+	if (stat(RC_DEPTREE_CACHE, &buf) == 0) {
-	if (!rc_newer_than(RC_DEPTREE_CACHE, RC_INITDIR, newest, file))
+		mtime = buf.st_mtime;
-		return true;
+	} else {
-	if (!rc_newer_than(RC_DEPTREE_CACHE, RC_CONFDIR, newest, file))
+		/* No previous cache found.
-		return true;
+		 * We still run the scan, in case of clock skew; we still need to return
+		 * the newest time.
+		 */
+		newer = true;
+		mtime = time(NULL);
+	}
+
+	newer |= !deep_mtime_check(RC_INITDIR,true,&mtime,file);
+	newer |= !deep_mtime_check(RC_CONFDIR,true,&mtime,file);
 #ifdef RC_PKG_INITDIR
-	if (!rc_newer_than(RC_DEPTREE_CACHE, RC_PKG_INITDIR, newest, file))
+    newer |= !deep_mtime_check(RC_PKG_INITDIR,true,&mtime,file);
-		return true;
 #endif
 #ifdef RC_PKG_CONFDIR
-	if (!rc_newer_than(RC_DEPTREE_CACHE, RC_PKG_CONFDIR, newest, file))
+    newer |= !deep_mtime_check(RC_PKG_CONFDIR,true,&mtime,file);
-		return true;
 #endif
-#ifdef RC_LOCAL_INITDIR
+#ifdef RC_LOCAL_INITDIRs
-	if (!rc_newer_than(RC_DEPTREE_CACHE, RC_LOCAL_INITDIR, newest, file))
+    newer |= !deep_mtime_check(RC_LOCAL_INITDIR,true,&mtime,file);
-		return true;
 #endif
 #ifdef RC_LOCAL_CONFDIR
-	if (!rc_newer_than(RC_DEPTREE_CACHE, RC_LOCAL_CONFDIR, newest, file))
+    newer |= !deep_mtime_check(RC_LOCAL_CONFDIR,true,&mtime,file);
-		return true;
 #endif
-	if (!rc_newer_than(RC_DEPTREE_CACHE, RC_CONF, newest, file))
+    newer |= !deep_mtime_check(RC_CONF,true,&mtime,file);
-		return true;
 
 	/* Some init scripts dependencies change depending on config files
 	 * outside of baselayout, like syslog-ng, so we check those too. */
 	config = rc_config_list(RC_DEPCONFIG);
 	TAILQ_FOREACH(s, config, entries) {
-		if (!rc_newer_than(RC_DEPTREE_CACHE, s->value, newest, file)) {
+		newer |= !deep_mtime_check(s->value, true, &mtime, file);
-			newer = true;
-			break;
-		}
 	}
 	rc_stringlist_free(config);
+
+	/* Return newest file time, if requested */
+	if ((newer) && (newest != NULL)) {
+	    *newest = mtime;
+	}
+
 	return newer;
 }
 librc_hidden_def(rc_deptree_update_needed)