Follow-up to f4a0b99: track modifications of service env: files

Add support for monitoring environment files for services declared with
the `env:[-]/path/to/file` option.  The default path to such files has
been chosen to follow Debian and Buildroot /etc/default/*

Signed-off-by: Joachim Wiberg <troglobit@gmail.com>

configure.ac

@@ -113,6 +113,10 @@ AC_ARG_WITH(rc-local,
         AS_HELP_STRING([--with-rc-local=FILE], [SysV init /etc/rc.local file, default /etc/rc.local]),
 	[rclocal=$withval], [rclocal=$sysconfdir/rc.local])
 
+AC_ARG_WITH(sysconfig,
+        AS_HELP_STRING([--with-sysconfig=DIR], [Enviroment config directory, default /etc/default]),
+	[sysconfig=$withval], [sysconfig=yes])
+
 AC_ARG_WITH(hostname,
         AS_HELP_STRING([--with-hostname=NAME], [If /etc/hostname is missing, default: noname]),
 	[hostname=$withval], [hostname=noname])
@@ -169,6 +173,13 @@ AS_IF([test "x$with_rc_local" != "xno"], [
 AC_EXPAND_DIR(rclocal_path, "$rclocal")
 AC_DEFINE_UNQUOTED(FINIT_RC_LOCAL, "$rclocal_path", [Compat SysV /etc/rc.local file to run last at boot.])
 
+AS_IF([test "x$with_sysconfig" != "xno"], [
+	AS_IF([test "x$sysconfig" = "xyes"], [
+		sysconfig=$sysconfdir/default
+		AC_EXPAND_DIR(sysconfig_path, "$sysconfig")
+		AC_DEFINE_UNQUOTED(FINIT_SYSCONFIG, "$sysconfig_path",
+				    [System environment, default /etc/default])])])
+
 AS_IF([test "x$with_heading" != "xno"], [
 	AS_IF([test "x$heading" = "xyes"], [
 		heading="$PACKAGE_NAME v$PACKAGE_VERSION"])])
@@ -225,6 +236,7 @@ cat <<EOF
   Finit config.d path...: $rcsd_path
   Finit plugin path.....: $plugin_path
   Compat rc.local path..: $rclocal_path
+  System environment....: $sysconfig_path
   Random seed path......: $random_path
   C Compiler............: $CC $CFLAGS $CPPFLAGS $LDFLAGS $LIBS
   Linker................: $LD $LLDP_LDFLAGS $LLDP_BIN_LDFLAGS $LDFLAGS $LIBS

doc/config.md

@@ -68,6 +68,34 @@ document [Finit Services](service.md).
 > examples in the `contrib/` directory, which can be used as a base.
 
 
+Service Environment
+-------------------
+
+Finit supports sourcing environment variables from `/etc/default/*`, or
+similar `--with-sysconfig=DIR`.  This is a common pattern from SysV init
+scripts, where the start-stop script is a generic script for the given
+service, `foo`, and the options for the service are sourced from the
+file `/etc/default/foo`.  Like this:
+
+* `/etc/default/foo`:
+
+        FOO_OPTIONS=--extra-arg="bar" -s -x
+
+* `/etc/finit.conf`:
+
+        service [2345] env:-/etc/default/foo foo -n $FOO_OPTIONS -- Example foo daemon
+
+Here the service `foo` is started with `-n`, to make sure it runs in the
+foreground, and the with the options found in the environment file.  With
+the `ps` command we can see that the process is started with:
+
+    foo -n --extra-arg=bar -s -x
+
+> **Note:** the leading `-` determines if Finit should treat a missing
+> environment file as blocking the start of the service or not.  When
+> `-` is used, a missing environment file does *not* block the start.
+
+
 Service Wrapper Scripts
 -----------------------
 

src/conf.c

@@ -772,13 +772,13 @@ static void drop_changes(void)
 
 static int do_change(char *dir, char *name, uint32_t mask)
 {
-	char path[strlen(dir) + strlen(name) + 2];
+	char fn[strlen(dir) + strlen(name) + 2];
 	struct conf_change *node;
 
-	snprintf(path, sizeof(path), "%s%s", dir, name);
-	_d("path: %s", path);
+	snprintf(fn, sizeof(fn), "%s%s%s", dir, fisslashdir(dir) ? "" : "/", name);
+	_d("path: %s mask: %08x", fn, mask);
 
-	node = conf_find(path);
+	node = conf_find(fn);
 	if (mask & (IN_DELETE | IN_MOVED_FROM)) {
 		drop_change(node);
 		return 0;
@@ -793,13 +793,13 @@ static int do_change(char *dir, char *name, uint32_t mask)
 	if (!node)
 		return 1;
 
-	node->name = strdup(path);
+	node->name = strdup(fn);
 	if (!node->name) {
 		free(node);
 		return 1;
 	}
 
-	_d("Event registered for %s, mask 0x%x", path, mask);
+	_d("Event registered for %s, mask 0x%x", fn, mask);
 	TAILQ_INSERT_HEAD(&conf_change_list, node, link);
 
 	return 0;
@@ -881,6 +881,14 @@ int conf_monitor(void)
 	rc += iwatch_add(&iw_conf, FINIT_RCSD "/enabled/",   IN_ONLYDIR | IN_DONT_FOLLOW);
 	rc += iwatch_add(&iw_conf, FINIT_CONF, 0);
 
+	/*
+	 * Systems with /etc/default, or similar, can also monitor changes
+	 * in env files sourced by .conf files (above)
+	 */
+#ifdef FINIT_SYSCONFIG
+	rc += iwatch_add(&iw_conf, FINIT_SYSCONFIG, IN_ONLYDIR);
+#endif
+
 	return rc + conf_reload();
 }
 

src/service.c

@@ -1116,7 +1116,7 @@ int service_register(int type, char *cfg, struct rlimit rlimit[], char *file)
 	memcpy(svc->rlimit, rlimit, sizeof(svc->rlimit));
 
 	/* New, recently modified or unchanged ... used on reload. */
-	if (file && conf_changed(file))
+	if ((file && conf_changed(file)) || conf_changed(svc_getenv(svc)))
 		svc_mark_dirty(svc);
 	else
 		svc_mark_clean(svc);