timedated: add back support for ntp-units.d/

We removed support for foreign services (and ntp-units.d/) in b72ddf0f4.
Support for foreign services was added back in 5d280742, but through an
environment variable.

The problem with the env var approach is that it only works as a mechanism
to select one item, and doesn't work nicely as a mechinism to create a list
of items through drop-ins (because the env var can be easily overridden, but not
extended). Having a list of "ntp providers" is important to be able to reliably disable
all of them when that is requested.

Another problem is that nobody ever bothered to care about our new "standard".
ntp-units.d/ is a nice simple format that works and is already supported by
chrony and ntpd and timedatex. If we were to introduce and ask people to follow
a new standard, there should be some good reason for this. The idea with env
vars has lower functionality, requires systemd-specific syntax. We should just
re-adopt the format that we originally introduced and that seems to work for
everyone, and more on to more interesting problems.

1 files changed, 64 insertions, 8 deletions

diff --git a/src/timedate/timedated.c b/src/timedate/timedated.c
index 57bbefc0c1..074ba3c079 100644
--- a/src/timedate/timedated.c
+++ b/src/timedate/timedated.c
@@ -15,7 +15,9 @@
 #include "bus-error.h"
 #include "bus-util.h"
 #include "clock-util.h"
+#include "conf-files.h"
 #include "def.h"
+#include "fd-util.h"
 #include "fileio-label.h"
 #include "fileio.h"
 #include "fs-util.h"
@@ -36,6 +38,8 @@
 #define NULL_ADJTIME_UTC "0.0 0 0\n0\nUTC\n"
 #define NULL_ADJTIME_LOCAL "0.0 0 0\n0\nLOCAL\n"
 
+#define UNIT_LIST_DIRS (const char* const*) CONF_PATHS_STRV("systemd/ntp-units.d")
+
 typedef struct UnitStatusInfo {
         char *name;
         char *load_state;
@@ -117,20 +121,17 @@ static int context_add_ntp_service(Context *c, const char *s) {
         return 0;
 }
 
-static int context_parse_ntp_services(Context *c) {
+static int context_parse_ntp_services_from_environment(Context *c) {
         const char *env, *p;
         int r;
 
         assert(c);
 
         env = getenv("SYSTEMD_TIMEDATED_NTP_SERVICES");
-        if (!env) {
-                r = context_add_ntp_service(c, "systemd-timesyncd.service");
-                if (r < 0)
-                        log_warning_errno(r, "Failed to add NTP service \"systemd-timesyncd.service\", ignoring: %m");
-
+        if (!env)
                 return 0;
-        }
+
+        log_debug("Using list of ntp services from environment variable $SYSTEMD_TIMEDATED_NTP_SERVICES.");
 
         for (p = env;;) {
                 _cleanup_free_ char *word = NULL;
@@ -150,7 +151,62 @@ static int context_parse_ntp_services(Context *c) {
                         log_warning_errno(r, "Failed to add NTP service \"%s\", ignoring: %m", word);
         }
 
-        return 0;
+        return 1;
+}
+
+static int context_parse_ntp_services_from_disk(Context *c) {
+        _cleanup_strv_free_ char **files = NULL;
+        char **f;
+        int r;
+
+        r = conf_files_list_strv(&files, ".list", NULL, CONF_FILES_FILTER_MASKED, UNIT_LIST_DIRS);
+        if (r < 0)
+                return log_error_errno(r, "Failed to enumerate .list files: %m");
+
+        STRV_FOREACH(f, files) {
+                _cleanup_fclose_ FILE *file = NULL;
+
+                log_debug("Reading file '%s'", *f);
+
+                r = fopen_unlocked(*f, "re", &file);
+                if (r < 0) {
+                        log_error_errno(r, "Failed to open %s, ignoring: %m", *f);
+                        continue;
+                }
+
+                for (;;) {
+                        _cleanup_free_ char *line = NULL;
+                        const char *word;
+
+                        r = read_line(file, LINE_MAX, &line);
+                        if (r < 0) {
+                                log_error_errno(r, "Failed to read %s, ignoring: %m", *f);
+                                continue;
+                        }
+                        if (r == 0)
+                                break;
+
+                        word = strstrip(line);
+                        if (isempty(word) || startswith("#", word))
+                                continue;
+
+                        r = context_add_ntp_service(c, word);
+                        if (r < 0)
+                                log_warning_errno(r, "Failed to add NTP service \"%s\", ignoring: %m", word);
+                }
+        }
+
+        return 1;
+}
+
+static int context_parse_ntp_services(Context *c) {
+        int r;
+
+        r = context_parse_ntp_services_from_environment(c);
+        if (r != 0)
+                return r;
+
+        return context_parse_ntp_services_from_disk(c);
 }
 
 static int context_ntp_service_is_active(Context *c) {