lib: hard-fail creating threads before fork()

Creating any threads before we fork() into the background (if `-d` is
given) is an extremely dangerous footgun;  the threads are created in
the parent and terminated when that exits.

This is extra dangerous because while testing, you'd often run the
daemon in foreground without `-d`, and everything works as expected.

Signed-off-by: David Lamparter <equinox@opensourcerouting.org>

1 files changed, 5 insertions, 0 deletions

diff --git a/lib/libfrr.c b/lib/libfrr.c
index 38f994bdfc..970e82c064 100644
--- a/lib/libfrr.c
+++ b/lib/libfrr.c
@@ -70,6 +70,8 @@ static char dbfile_default[512];
 #endif
 static char vtypath_default[512];
 
+/* cleared in frr_preinit(), then re-set after daemonizing */
+bool frr_is_after_fork = true;
 bool debug_memstats_at_exit = false;
 static bool nodetach_term, nodetach_daemon;
 static uint64_t startup_fds;
@@ -308,6 +310,7 @@ void frr_init_vtydir(void)
 void frr_preinit(struct frr_daemon_info *daemon, int argc, char **argv)
 {
 	di = daemon;
+	frr_is_after_fork = false;
 
 	/* basename(), opencoded. */
 	char *p = strrchr(argv[0], '/');
@@ -990,6 +993,8 @@ void frr_config_fork(void)
 	if (di->daemon_mode || di->terminal)
 		frr_daemonize();
 
+	frr_is_after_fork = true;
+
 	if (!di->pid_file)
 		di->pid_file = pidfile_default;
 	pid_output(di->pid_file);