lib: vty_stdio signal handling

- SIGTSTP appropriately suspends the foreground terminal
- SIGINT causes the daemon to exit, regardless of -d
- SIGQUIT causes the daemon to daemonize, regardless of -d

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

configure.ac

@@ -1015,6 +1015,13 @@ fi
 LIBS="$TMPLIBS"
 AC_SUBST(LIBM)
 
+AC_CHECK_FUNCS([ppoll], [
+  AC_DEFINE([HAVE_PPOLL], 1, [have Linux/BSD ppoll()])
+])
+AC_CHECK_FUNCS([pollts], [
+  AC_DEFINE([HAVE_POLLTS], 1, [have NetBSD pollts()])
+])
+
 dnl ---------------
 dnl other functions
 dnl ---------------

lib/grammar_sandbox_main.c

@@ -26,10 +26,11 @@
 #include "command.h"
 #include "memory_vty.h"
 
-static void vty_do_exit(void)
+static void vty_do_exit(int isexit)
 {
 	printf("\nend.\n");
-	exit(0);
+	if (!isexit)
+		exit(0);
 }
 
 struct thread_master *master;

lib/libfrr.c

@@ -379,22 +379,79 @@ struct thread_master *frr_init(void)
 	return master;
 }
 
+static int rcvd_signal = 0;
+
+static void rcv_signal(int signum)
+{
+	rcvd_signal = signum;
+	/* poll() is interrupted by the signal; handled below */
+}
+
 static void frr_daemon_wait(int fd)
 {
 	struct pollfd pfd[1];
 	int ret;
 	pid_t exitpid;
 	int exitstat;
+	sigset_t sigs, prevsigs;
+
+	sigemptyset(&sigs);
+	sigaddset(&sigs, SIGTSTP);
+	sigaddset(&sigs, SIGQUIT);
+	sigaddset(&sigs, SIGINT);
+	sigprocmask(SIG_BLOCK, &sigs, &prevsigs);
+
+	struct sigaction sa = {
+		.sa_handler = rcv_signal, .sa_flags = SA_RESETHAND,
+	};
+	sigemptyset(&sa.sa_mask);
+	sigaction(SIGTSTP, &sa, NULL);
+	sigaction(SIGQUIT, &sa, NULL);
+	sigaction(SIGINT, &sa, NULL);
 
 	do {
+		char buf[1];
+		ssize_t nrecv;
+
 		pfd[0].fd = fd;
 		pfd[0].events = POLLIN;
 
+		rcvd_signal = 0;
+
+#if   defined(HAVE_PPOLL)
+		ret = ppoll(pfd, 1, NULL, &prevsigs);
+#elif defined(HAVE_POLLTS)
+		ret = pollts(pfd, 1, NULL, &prevsigs);
+#else
+		/* racy -- only used on FreeBSD 9 */
+		sigset_t tmpsigs;
+		sigprocmask(SIG_SETMASK, &prevsigs, &tmpsigs);
 		ret = poll(pfd, 1, -1);
+		sigprocmask(SIG_SETMASK, &tmpsigs, NULL);
+#endif
 		if (ret < 0 && errno != EINTR && errno != EAGAIN) {
 			perror("poll()");
 			exit(1);
 		}
+		switch (rcvd_signal) {
+		case SIGTSTP:
+			send(fd, "S", 1, 0);
+			do {
+				nrecv = recv(fd, buf, sizeof(buf), 0);
+			} while (nrecv == -1
+				 && (errno == EINTR || errno == EAGAIN));
+
+			raise(SIGTSTP);
+			sigaction(SIGTSTP, &sa, NULL);
+			send(fd, "R", 1, 0);
+			break;
+		case SIGINT:
+			send(fd, "I", 1, 0);
+			break;
+		case SIGQUIT:
+			send(fd, "Q", 1, 0);
+			break;
+		}
 	} while (ret <= 0);
 
 	exitpid = waitpid(-1, &exitstat, WNOHANG);
@@ -468,7 +525,7 @@ void frr_config_fork(void)
 	if (di->dryrun)
 		exit(0);
 
-	if (di->daemon_mode)
+	if (di->daemon_mode || di->terminal)
 		frr_daemonize();
 
 	if (!di->pid_file)
@@ -497,11 +554,18 @@ void frr_vty_serv(void)
 	vty_serv_sock(di->vty_addr, di->vty_port, di->vty_path);
 }
 
-static void frr_terminal_close(void)
+static void frr_terminal_close(int isexit)
 {
-	if (!di->daemon_mode) {
+	if (daemon_ctl_sock != -1) {
+		close(daemon_ctl_sock);
+		daemon_ctl_sock = -1;
+	}
+
+	if (!di->daemon_mode || isexit) {
 		printf("\n%s exiting\n", di->name);
-		raise(SIGINT);
+		if (!isexit)
+			raise(SIGINT);
+		return;
 	} else {
 		printf("\n%s daemonizing\n", di->name);
 		fflush(stdout);
@@ -512,11 +576,43 @@ static void frr_terminal_close(void)
 	dup2(nullfd, 1);
 	dup2(nullfd, 2);
 	close(nullfd);
+}
 
-	if (daemon_ctl_sock != -1) {
-		close(daemon_ctl_sock);
-		daemon_ctl_sock = -1;
+static struct thread *daemon_ctl_thread = NULL;
+
+static int frr_daemon_ctl(struct thread *t)
+{
+	char buf[1];
+	ssize_t nr;
+
+	nr = recv(daemon_ctl_sock, buf, sizeof(buf), 0);
+	if (nr < 0 && (errno == EINTR || errno == EAGAIN))
+		goto out;
+	if (nr <= 0)
+		return 0;
+
+	switch (buf[0]) {
+	case 'S':	/* SIGTSTP */
+		vty_stdio_suspend();
+		send(daemon_ctl_sock, "s", 1, 0);
+		break;
+	case 'R':	/* SIGTCNT [implicit] */
+		vty_stdio_resume();
+		break;
+	case 'I':	/* SIGINT */
+		di->daemon_mode = false;
+		raise(SIGINT);
+		break;
+	case 'Q':	/* SIGQUIT */
+		di->daemon_mode = true;
+		vty_stdio_close();
+		break;
 	}
+
+out:
+	thread_add_read(master, frr_daemon_ctl, NULL, daemon_ctl_sock,
+			&daemon_ctl_thread);
+	return 0;
 }
 
 void frr_run(struct thread_master *master)
@@ -534,6 +630,11 @@ void frr_run(struct thread_master *master)
 
 	if (di->terminal) {
 		vty_stdio(frr_terminal_close);
+		if (daemon_ctl_sock != -1) {
+			set_nonblocking(daemon_ctl_sock);
+			thread_add_read(master, frr_daemon_ctl, NULL,
+					daemon_ctl_sock, &daemon_ctl_thread);
+		}
 	} else if (daemon_ctl_sock != -1) {
 		close(daemon_ctl_sock);
 		daemon_ctl_sock = -1;

lib/vty.c

@@ -1660,24 +1660,82 @@ static struct vty *vty_create(int vty_sock, union sockunion *su)
 /* create vty for stdio */
 static struct termios stdio_orig_termios;
 static struct vty *stdio_vty = NULL;
-static void (*stdio_vty_atclose)(void);
+static bool stdio_termios = false;
+static void (*stdio_vty_atclose)(int isexit);
 
-static void vty_stdio_reset(void)
+static void vty_stdio_reset(int isexit)
 {
 	if (stdio_vty) {
-		tcsetattr(0, TCSANOW, &stdio_orig_termios);
+		if (stdio_termios)
+			tcsetattr(0, TCSANOW, &stdio_orig_termios);
+		stdio_termios = false;
+
 		stdio_vty = NULL;
 
 		if (stdio_vty_atclose)
-			stdio_vty_atclose();
+			stdio_vty_atclose(isexit);
 		stdio_vty_atclose = NULL;
 	}
 }
 
-struct vty *vty_stdio(void (*atclose)())
+static void vty_stdio_atexit(void)
+{
+	vty_stdio_reset(1);
+}
+
+void vty_stdio_suspend(void)
+{
+	if (!stdio_vty)
+		return;
+
+	if (stdio_vty->t_write)
+		thread_cancel(stdio_vty->t_write);
+	if (stdio_vty->t_read)
+		thread_cancel(stdio_vty->t_read);
+	if (stdio_vty->t_timeout)
+		thread_cancel(stdio_vty->t_timeout);
+
+	if (stdio_termios)
+		tcsetattr(0, TCSANOW, &stdio_orig_termios);
+	stdio_termios = false;
+}
+
+void vty_stdio_resume(void)
+{
+	if (!stdio_vty)
+		return;
+
+	if (!tcgetattr(0, &stdio_orig_termios)) {
+		struct termios termios;
+
+		termios = stdio_orig_termios;
+		termios.c_iflag &= ~(IGNBRK | BRKINT | PARMRK | ISTRIP | INLCR
+				     | IGNCR | ICRNL | IXON);
+		termios.c_oflag &= ~OPOST;
+		termios.c_lflag &= ~(ECHO | ECHONL | ICANON | IEXTEN);
+		termios.c_cflag &= ~(CSIZE | PARENB);
+		termios.c_cflag |= CS8;
+		tcsetattr(0, TCSANOW, &termios);
+		stdio_termios = true;
+	}
+
+	vty_prompt(stdio_vty);
+
+	/* Add read/write thread. */
+	vty_event(VTY_WRITE, 1, stdio_vty);
+	vty_event(VTY_READ, 0, stdio_vty);
+}
+
+void vty_stdio_close(void)
+{
+	if (!stdio_vty)
+		return;
+	vty_close(stdio_vty);
+}
+
+struct vty *vty_stdio(void (*atclose)(int isexit))
 {
 	struct vty *vty;
-	struct termios termios;
 
 	/* refuse creating two vtys on stdio */
 	if (stdio_vty)
@@ -1695,23 +1753,7 @@ struct vty *vty_stdio(void (*atclose)())
 	vty->v_timeout = 0;
 	strcpy(vty->address, "console");
 
-	if (!tcgetattr(0, &stdio_orig_termios)) {
-		termios = stdio_orig_termios;
-		termios.c_iflag &= ~(IGNBRK | BRKINT | PARMRK | ISTRIP | INLCR
-				     | IGNCR | ICRNL | IXON);
-		termios.c_oflag &= ~OPOST;
-		termios.c_lflag &= ~(ECHO | ECHONL | ICANON | ISIG | IEXTEN);
-		termios.c_cflag &= ~(CSIZE | PARENB);
-		termios.c_cflag |= CS8;
-		tcsetattr(0, TCSANOW, &termios);
-	}
-
-	vty_prompt(vty);
-
-	/* Add read/write thread. */
-	vty_event(VTY_WRITE, 1, vty);
-	vty_event(VTY_READ, 0, vty);
-
+	vty_stdio_resume();
 	return vty;
 }
 
@@ -2155,7 +2197,7 @@ void vty_close(struct vty *vty)
 	XFREE(MTYPE_VTY, vty);
 
 	if (was_stdio)
-		vty_stdio_reset();
+		vty_stdio_reset(0);
 }
 
 /* When time out occur output message then close connection. */
@@ -2919,7 +2961,7 @@ void vty_init(struct thread_master *master_thread)
 
 	vty_master = master_thread;
 
-	atexit(vty_stdio_reset);
+	atexit(vty_stdio_atexit);
 
 	/* Initilize server thread vector. */
 	Vvty_serv_thread = vector_init(VECTOR_MIN_SIZE);

lib/vty.h

@@ -252,7 +252,7 @@ extern void vty_init_vtysh(void);
 extern void vty_terminate(void);
 extern void vty_reset(void);
 extern struct vty *vty_new(void);
-extern struct vty *vty_stdio(void (*atclose)(void));
+extern struct vty *vty_stdio(void (*atclose)(int isexit));
 extern int vty_out(struct vty *, const char *, ...) PRINTF_ATTRIBUTE(2, 3);
 extern void vty_read_config(const char *, char *);
 extern void vty_time_print(struct vty *, int);
@@ -268,6 +268,11 @@ extern int vty_shell(struct vty *);
 extern int vty_shell_serv(struct vty *);
 extern void vty_hello(struct vty *);
 
+/* ^Z / SIGTSTP handling */
+extern void vty_stdio_suspend(void);
+extern void vty_stdio_resume(void);
+extern void vty_stdio_close(void);
+
 /* Send a fixed-size message to all vty terminal monitors; this should be
    an async-signal-safe function. */
 extern void vty_log_fixed(char *buf, size_t len);

tests/lib/cli/common_cli.c

@@ -45,7 +45,7 @@ int dump_args(struct vty *vty, const char *descr, int argc,
 	return CMD_SUCCESS;
 }
 
-static void vty_do_exit(void)
+static void vty_do_exit(int isexit)
 {
 	printf("\nend.\n");
 	cmd_terminate();
@@ -54,7 +54,8 @@ static void vty_do_exit(void)
 	closezlog();
 
 	log_memstats_stderr("testcli");
-	exit(0);
+	if (!isexit)
+		exit(0);
 }
 
 /* main routine. */