slattach: code shrink, better --help text

function                                             old     new   delta
tcsetattr_serial_or_warn                               -      34     +34
static.int_N_SLIP                                      -       4      +4
restore_state_and_exit                               123     117      -6
packed_usage                                       31774   31747     -27
set_termios_state_or_warn                             42       -     -42
slattach_main                                        673     624     -49
------------------------------------------------------------------------------
(add/remove: 2/1 grow/shrink: 0/3 up/down: 38/-124)           Total: -86 bytes

Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>

3 files changed, 68 insertions, 107 deletions

diff --git a/NOFORK_NOEXEC.lst b/NOFORK_NOEXEC.lst
index 9b33afc32..3bd82aa60 100644
--- a/NOFORK_NOEXEC.lst
+++ b/NOFORK_NOEXEC.lst
@@ -78,7 +78,7 @@ conspy - interactive, longterm
 cp - noexec. runner
 cpio - runner
 crond - daemon
-crontab 0 leaks: open+xasprintf
+crontab - longterm (runs $EDITOR), leaks: open+xasprintf
 cryptpw - noexec. changes state: with --password-fd=N, moves N to stdin
 cttyhack - noexec. spawner
 cut - noexec. runner
@@ -311,7 +311,7 @@ setkeycodes
 setlogcons
 setpriv - spawner, changes state, let's play safe and not be noexec
 setserial
-setsid - spawner, uses fork_or_rexec() [not audted to work in noexec], let's play safe and not be noexec
+setsid - spawner, uses fork_or_rexec() [not audited to work in noexec], let's play safe and not be noexec
 setuidgid - noexec. spawner
 sha1sum - noexec. runner
 sha256sum - noexec. runner
@@ -320,7 +320,7 @@ sha512sum - noexec. runner
 showkey - interactive, longterm
 shred - runner
 shuf - noexec. runner
-slattach
+slattach - longterm (may sleep forever), uses bb_common_bufsiz1
 sleep - runner, longterm
 smemcap - runner
 softlimit - noexec. spawner
diff --git a/libbb/xfuncs.c b/libbb/xfuncs.c
index 98d3531d6..1b3a1667b 100644
--- a/libbb/xfuncs.c
+++ b/libbb/xfuncs.c
@@ -313,7 +313,7 @@ int FAST_FUNC tcsetattr_stdin_TCSANOW(const struct termios *tp)
 
 int FAST_FUNC set_termios_to_raw(int fd, struct termios *oldterm, int flags)
 {
-//TODO: lineedit, microcom and less might be adapted to use this too:
+//TODO: lineedit, microcom, slattach, less might be adapted to use this too:
 // grep for "tcsetattr"
 
 	struct termios newterm;
diff --git a/networking/slattach.c b/networking/slattach.c
index 71b5bf427..d4659a314 100644
--- a/networking/slattach.c
+++ b/networking/slattach.c
@@ -17,23 +17,23 @@
 //config:	default y
 //config:	select PLATFORM_LINUX
 //config:	help
-//config:	slattach is a small utility to attach network interfaces to serial
-//config:	lines.
+//config:	slattach configures serial line as SLIP network interface.
 
 //applet:IF_SLATTACH(APPLET(slattach, BB_DIR_SBIN, BB_SUID_DROP))
+/* shouldn't be NOEXEC: may sleep indefinitely */
 
 //kbuild:lib-$(CONFIG_SLATTACH) += slattach.o
 
 //usage:#define slattach_trivial_usage
-//usage:       "[-cehmLF] [-s SPEED] [-p PROTOCOL] DEVICE"
+//usage:       "[-ehmLF] [-c SCRIPT] [-s BAUD] [-p PROTOCOL] SERIAL_DEVICE"
 //usage:#define slattach_full_usage "\n\n"
-//usage:       "Attach network interface(s) to serial line(s)\n"
-//usage:     "\n	-p PROT	Set protocol (slip, cslip, slip6, clisp6 or adaptive)"
-//usage:     "\n	-s SPD	Set line speed"
-//usage:     "\n	-e	Exit after initializing device"
-//usage:     "\n	-h	Exit when the carrier is lost"
-//usage:     "\n	-c PROG	Run PROG when the line is hung up"
-//usage:     "\n	-m	Do NOT initialize the line in raw 8 bits mode"
+//usage:       "Configure serial line as SLIP network interface\n"
+//usage:     "\n	-p PROT	Protocol: slip, cslip (default), slip6, clisp6, adaptive"
+//usage:     "\n	-s BAUD	Line speed"
+//usage:     "\n	-e	Exit after initialization"
+//usage:     "\n	-h	Exit if carrier is lost (else never exits)"
+//usage:     "\n	-c PROG	Run PROG on carrier loss"
+//usage:     "\n	-m	Do NOT set raw 8bit mode"
 //usage:     "\n	-L	Enable 3-wire operation"
 //usage:     "\n	-F	Disable RTS/CTS flow control"
 
@@ -42,103 +42,53 @@
 #include "libiproute/utils.h" /* invarg_1_to_2() */
 
 struct globals {
-	int handle;
 	int saved_disc;
 	struct termios saved_state;
 } FIX_ALIASING;
 #define G (*(struct globals*)bb_common_bufsiz1)
-#define handle       (G.handle      )
-#define saved_disc   (G.saved_disc  )
-#define saved_state  (G.saved_state )
 #define INIT_G() do { setup_common_bufsiz(); } while (0)
 
+#define serial_fd 3
 
-/*
- * Save tty state and line discipline
- *
- * It is fine here to bail out on errors, since we haven modified anything yet
- */
-static void save_state(void)
-{
-	/* Save line status */
-	if (tcgetattr(handle, &saved_state) < 0)
-		bb_perror_msg_and_die("get state");
-
-	/* Save line discipline */
-	xioctl(handle, TIOCGETD, &saved_disc);
-}
-
-static int set_termios_state_or_warn(struct termios *state)
+static int tcsetattr_serial_or_warn(struct termios *state)
 {
 	int ret;
 
-	ret = tcsetattr(handle, TCSANOW, state);
-	if (ret < 0) {
-		bb_perror_msg("set state");
+	ret = tcsetattr(serial_fd, TCSANOW, state);
+	if (ret != 0) {
+		bb_perror_msg("tcsetattr");
 		return 1; /* used as exitcode */
 	}
-	return 0;
+	return ret; /* 0 */
 }
 
-/*
- * Restore state and line discipline for ALL managed ttys
- *
- * Restoring ALL managed ttys is the only way to have a single
- * hangup delay.
- *
- * Go on after errors: we want to restore as many controlled ttys
- * as possible.
- */
 static void restore_state_and_exit(int exitcode) NORETURN;
 static void restore_state_and_exit(int exitcode)
 {
 	struct termios state;
 
 	/* Restore line discipline */
-	if (ioctl_or_warn(handle, TIOCSETD, &saved_disc) < 0) {
+	if (ioctl_or_warn(serial_fd, TIOCSETD, &G.saved_disc)) {
 		exitcode = 1;
 	}
 
 	/* Hangup */
-	memcpy(&state, &saved_state, sizeof(state));
+	memcpy(&state, &G.saved_state, sizeof(state));
 	cfsetispeed(&state, B0);
 	cfsetospeed(&state, B0);
-	if (set_termios_state_or_warn(&state))
-		exitcode = 1;
+	exitcode |= tcsetattr_serial_or_warn(&state);
 	sleep(1);
 
 	/* Restore line status */
-	if (set_termios_state_or_warn(&saved_state))
+	if (tcsetattr_serial_or_warn(&G.saved_state))
 		exit(EXIT_FAILURE);
+
 	if (ENABLE_FEATURE_CLEAN_UP)
-		close(handle);
+		close(serial_fd);
 
 	exit(exitcode);
 }
 
-/*
- * Set tty state, line discipline and encapsulation
- */
-static void set_state(struct termios *state, int encap)
-{
-	int disc;
-
-	/* Set line status */
-	if (set_termios_state_or_warn(state))
-		goto bad;
-	/* Set line discliple (N_SLIP always) */
-	disc = N_SLIP;
-	if (ioctl_or_warn(handle, TIOCSETD, &disc) < 0) {
-		goto bad;
-	}
-
-	/* Set encapsulation (SLIP, CSLIP, etc) */
-	if (ioctl_or_warn(handle, SIOCSIFENCAP, &encap) < 0) {
- bad:
-		restore_state_and_exit(EXIT_FAILURE);
-	}
-}
-
 static void sig_handler(int signo UNUSED_PARAM)
 {
 	restore_state_and_exit(EXIT_SUCCESS);
@@ -155,13 +105,14 @@ int slattach_main(int argc UNUSED_PARAM, char **argv)
 		"cslip6\0"      /* 3 */
 		"adaptive\0"    /* 8 */
 		;
+	static const int int_N_SLIP = N_SLIP;
 
-	int i, encap, opt;
+	int encap, opt, fd;
 	struct termios state;
 	const char *proto = "cslip";
 	const char *extcmd;   /* Command to execute after hangup */
 	const char *baud_str;
-	int baud_code = -1;   /* Line baud rate (system code) */
+	int baud_code = baud_code; /* for compiler */
 
 	enum {
 		OPT_p_proto  = 1 << 0,
@@ -177,15 +128,12 @@ int slattach_main(int argc UNUSED_PARAM, char **argv)
 	INIT_G();
 
 	/* Parse command line options */
+	opt_complementary = "=1";
 	opt = getopt32(argv, "p:s:c:ehmLF", &proto, &baud_str, &extcmd);
 	/*argc -= optind;*/
 	argv += optind;
 
-	if (!*argv)
-		bb_show_usage();
-
 	encap = index_in_strings(proto_names, proto);
-
 	if (encap < 0)
 		invarg_1_to_2(proto, "protocol");
 	if (encap > 3)
@@ -198,6 +146,22 @@ int slattach_main(int argc UNUSED_PARAM, char **argv)
 			invarg_1_to_2(baud_str, "baud rate");
 	}
 
+	/* Open tty */
+	fd = open(*argv, O_RDWR | O_NDELAY);
+	if (fd < 0) {
+		char *buf = concat_path_file("/dev", *argv);
+		fd = xopen(buf, O_RDWR | O_NDELAY);
+		/* maybe if (ENABLE_FEATURE_CLEAN_UP) ?? */
+		free(buf);
+	}
+	xmove_fd(fd, serial_fd);
+
+	/* Save current tty state */
+	if (tcgetattr(serial_fd, &G.saved_state) != 0)
+		bb_perror_msg_and_die("tcgetattr");
+	/* Save line discipline */
+	xioctl(serial_fd, TIOCGETD, &G.saved_disc);
+
 	/* Trap signals in order to restore tty states upon exit */
 	if (!(opt & OPT_e_quit)) {
 		bb_signals(0
@@ -208,43 +172,37 @@ int slattach_main(int argc UNUSED_PARAM, char **argv)
 			, sig_handler);
 	}
 
-	/* Open tty */
-	handle = open(*argv, O_RDWR | O_NDELAY);
-	if (handle < 0) {
-		char *buf = concat_path_file("/dev", *argv);
-		handle = xopen(buf, O_RDWR | O_NDELAY);
-		/* maybe if (ENABLE_FEATURE_CLEAN_UP) ?? */
-		free(buf);
-	}
-
-	/* Save current tty state */
-	save_state();
-
 	/* Configure tty */
-	memcpy(&state, &saved_state, sizeof(state));
+	memcpy(&state, &G.saved_state, sizeof(state));
 	if (!(opt & OPT_m_nonraw)) { /* raw not suppressed */
 		memset(&state.c_cc, 0, sizeof(state.c_cc));
 		state.c_cc[VMIN] = 1;
 		state.c_iflag = IGNBRK | IGNPAR;
-		state.c_oflag = 0;
-		state.c_lflag = 0;
+		/*state.c_oflag = 0;*/
+		/*state.c_lflag = 0;*/
 		state.c_cflag = CS8 | HUPCL | CREAD
 		              | ((opt & OPT_L_local) ? CLOCAL : 0)
 		              | ((opt & OPT_F_noflow) ? 0 : CRTSCTS);
-		cfsetispeed(&state, cfgetispeed(&saved_state));
-		cfsetospeed(&state, cfgetospeed(&saved_state));
+		cfsetispeed(&state, cfgetispeed(&G.saved_state));
+		cfsetospeed(&state, cfgetospeed(&G.saved_state));
 	}
-
 	if (opt & OPT_s_baud) {
 		cfsetispeed(&state, baud_code);
 		cfsetospeed(&state, baud_code);
 	}
-
-	set_state(&state, encap);
+	/* Set line status */
+	if (tcsetattr_serial_or_warn(&state))
+		goto bad;
+	/* Set line disclipline (N_SLIP always) */
+	if (ioctl_or_warn(serial_fd, TIOCSETD, (void*)&int_N_SLIP))
+		goto bad;
+	/* Set encapsulation (SLIP, CSLIP, etc) */
+	if (ioctl_or_warn(serial_fd, SIOCSIFENCAP, &encap))
+		goto bad;
 
 	/* Exit now if option -e was passed */
 	if (opt & OPT_e_quit)
-		return 0;
+		return EXIT_SUCCESS;
 
 	/* If we're not requested to watch, just keep descriptor open
 	 * until we are killed */
@@ -254,17 +212,20 @@ int slattach_main(int argc UNUSED_PARAM, char **argv)
 
 	/* Watch line for hangup */
 	while (1) {
-		if (ioctl(handle, TIOCMGET, &i) < 0 || !(i & TIOCM_CAR))
-			goto no_carrier;
+		int modem_stat;
+		if (ioctl(serial_fd, TIOCMGET, &modem_stat))
+			break;
+		if (!(modem_stat & TIOCM_CAR))
+			break;
 		sleep(15);
 	}
 
- no_carrier:
-
 	/* Execute command on hangup */
 	if (opt & OPT_c_extcmd)
 		system(extcmd);
 
 	/* Restore states and exit */
 	restore_state_and_exit(EXIT_SUCCESS);
+ bad:
+	restore_state_and_exit(EXIT_FAILURE);
 }