kike: fix daemonization

First of all, we used to write the wrong PID in the file.

Second of all, systemd needs some extra BS to not kill us immediately.

1 files changed, 32 insertions, 8 deletions

diff --git a/kike.c b/kike.c
index 768126b..b4f4434 100644
--- a/kike.c
+++ b/kike.c
@@ -25,6 +25,8 @@
 #include "kike-replies.c"
 #include <nl_types.h>
 
+enum { PIPE_READ, PIPE_WRITE };
+
 // FIXME: don't use time_t to compute time deltas
 
 // --- Configuration (application-specific) ------------------------------------
@@ -3838,18 +3840,34 @@ on_signal_pipe_readable (const struct pollfd *fd, struct server_context *ctx)
 }
 
 static void
-daemonize (void)
+daemonize (struct server_context *ctx)
 {
 	print_status ("daemonizing...");
 
 	if (chdir ("/"))
 		exit_fatal ("%s: %s", "chdir", strerror (errno));
 
+	// Because of systemd, we need to exit the parent process _after_ writing
+	// a PID file, otherwise our grandchild would receive a SIGTERM
+	int sync_pipe[2];
+	if (pipe (sync_pipe))
+		exit_fatal ("%s: %s", "pipe", strerror (errno));
+
 	pid_t pid;
 	if ((pid = fork ()) < 0)
 		exit_fatal ("%s: %s", "fork", strerror (errno));
 	else if (pid)
+	{
+		// Wait until all write ends of the pipe are closed, which can mean
+		// either success or failure, we don't need to care
+		xclose (sync_pipe[PIPE_WRITE]);
+
+		char dummy;
+		if (read (sync_pipe[PIPE_READ], &dummy, 1) < 0)
+			exit_fatal ("%s: %s", "read", strerror (errno));
+
 		exit (EXIT_SUCCESS);
+	}
 
 	setsid ();
 	signal (SIGHUP, SIG_IGN);
@@ -3862,6 +3880,15 @@ daemonize (void)
 	openlog (PROGRAM_NAME, LOG_NDELAY | LOG_NOWAIT | LOG_PID, 0);
 	g_log_message_real = log_message_syslog;
 
+	// Write the PID file (if so configured) and get rid of the pipe, so that
+	// the read() in our grandparent finally returns zero (no write ends)
+	struct error *e = NULL;
+	if (!irc_lock_pid_file (ctx, &e))
+		exit_fatal ("%s", e->message);
+
+	xclose (sync_pipe[PIPE_READ]);
+	xclose (sync_pipe[PIPE_WRITE]);
+
 	// XXX: we may close our own descriptors this way, crippling ourselves;
 	//   there is no real guarantee that we will start with all three
 	//   descriptors open.  In theory we could try to enumerate the descriptors
@@ -3948,16 +3975,13 @@ main (int argc, char *argv[])
 	 || !irc_initialize_motd (&ctx, &e)
 	 || !irc_initialize_catalog (&ctx, &e)
 	 || !irc_parse_config (&ctx, &e)
-	 || !irc_lock_pid_file (&ctx, &e)
 	 || !irc_setup_listen_fds (&ctx, &e))
-	{
-		print_error ("%s", e->message);
-		error_free (e);
-		exit (EXIT_FAILURE);
-	}
+		exit_fatal ("%s", e->message);
 
 	if (!g_debug_mode)
-		daemonize ();
+		daemonize (&ctx);
+	else if (!irc_lock_pid_file (&ctx, &e))
+		exit_fatal ("%s", e->message);
 
 	ctx.polling = true;
 	while (ctx.polling)