log: add new "prohibit_ipc" flag to logging system

If set, we'll avoid logging to any IPC log targets, i.e. syslog or the
journal, but allow stderr, kmsg, console logging.

This is useful as PID 1 wants to turn this off explicitly as long as the
journal is not up.

Previously we'd open/close the log stream to these services whenever
needed but this is incompatible with the "open_when_needed" logic
introduced in #6915, which might open the log streams whenever it likes,
including possibly inside of the child process we fork off that'll
become journald later on. Hence, let's make this all explicit, and
instead of managing when we open/close log streams add a boolean that
clearly prohibits the IPC targets when needed, so that opening can be
done at any time, but will honour this.

See: #7985

diff --git a/src/basic/log.c b/src/basic/log.c
index b01ebaacd2d58ae3ec22d025a7b9f5d161521f05..a704e4bede4296bdee55cd825f3b598990d55ca6 100644 (file)
--- a/src/basic/log.c
+++ b/src/basic/log.c
@@ -79,6 +79,7 @@ static bool upgrade_syslog_to_journal = false;
 #endif // 0
 static bool always_reopen_console = false;
 static bool open_when_needed = false;
+static bool prohibit_ipc = false;
 
 /* Akin to glibc's __abort_msg; which is private and we hence cannot
  * use here. */
@@ -261,7 +262,8 @@ int log_open(void) {
             isatty(STDERR_FILENO) <= 0) {
 
 #if 0 /// elogind does not support logging to systemd-journald
-                if (IN_SET(log_target, LOG_TARGET_AUTO,
+                if (!prohibit_ipc &&
+                    IN_SET(log_target, LOG_TARGET_AUTO,
                                        LOG_TARGET_JOURNAL_OR_KMSG,
                                        LOG_TARGET_JOURNAL)) {
                         r = log_open_journal();
@@ -273,7 +275,8 @@ int log_open(void) {
                 }
 #endif // 0
 
-                if (IN_SET(log_target, LOG_TARGET_SYSLOG_OR_KMSG,
+                if (!prohibit_ipc &&
+                    IN_SET(log_target, LOG_TARGET_SYSLOG_OR_KMSG,
                                        LOG_TARGET_SYSLOG)) {
                         r = log_open_syslog();
                         if (r >= 0) {
@@ -1356,6 +1359,10 @@ void log_set_open_when_needed(bool b) {
         open_when_needed = b;
 }
 
+void log_set_prohibit_ipc(bool b) {
+        prohibit_ipc = b;
+}
+
 int log_emergency_level(void) {
         /* Returns the log level to use for log_emergency() logging. We use LOG_EMERG only when we are PID 1, as only
          * then the system of the whole system is obviously affected. */

diff --git a/src/basic/log.h b/src/basic/log.h
index d04768cd4d2a24040b4e553eb84f1f41e58471ae..fa87b9fb59a2c195c5e30db48e7b22eab6e69310 100644 (file)
--- a/src/basic/log.h
+++ b/src/basic/log.h
@@ -316,6 +316,10 @@ void log_set_always_reopen_console(bool b);
 #endif // 0
 void log_set_open_when_needed(bool b);
 
+/* If turned on, then we'll never use IPC-based logging, i.e. never log to syslog or the journal. We'll only log to
+ * stderr, the console or kmsg */
+void log_set_prohibit_ipc(bool b);
+
 int log_syntax_internal(
                 const char *unit,
                 int level,