A major overhaul of the nmdm(4) driver:

It was based on the pty(4) driver which as a tty side an a non-tty side.

Nmdm(4) seems to have inherited two symmetric sides from pty but
unfortunately they are not quite ttys.  Running a getty one one
side and tip on the other failed to produce NL->CRNL mapping for
instance.

Rip out the basically bogus cdevsw->{read,write} functions and rely
on ttyread() and ttywrite() which does the same thing.

Use taskqueue_swi_giant to run a task for either side to do what
needs to be done.  (Direct calling is not an option as it leads to
recursion.)  Trigger the task from the t_oproc and t_stop methods.

Default the ports to not ECHO.  Since we neither rate limiting nor
emulation, two ports echoing each other is a really bad idea, which
can only be properly mitigated by rate limiting, rate emulation or
intelligent detection.  Rate emulation would be a neat feature.

Ditch the modem-line emulation, if needed for some app, it needs
to be thought much more about how it interacts with the open/close
logic.

1 files changed, 81 insertions, 375 deletions

diff --git a/sys/dev/nmdm/nmdm.c b/sys/dev/nmdm/nmdm.c
index 79a547687ef8..8855a27ff006 100644
--- a/sys/dev/nmdm/nmdm.c
+++ b/sys/dev/nmdm/nmdm.c
@@ -41,9 +41,6 @@ __FBSDID("$FreeBSD$");
 
 #include <sys/param.h>
 #include <sys/systm.h>
-#if defined(COMPAT_43) || defined(COMPAT_SUNOS)
-#include <sys/ioctl_compat.h>
-#endif
 #include <sys/proc.h>
 #include <sys/tty.h>
 #include <sys/conf.h>
@@ -54,27 +51,21 @@ __FBSDID("$FreeBSD$");
 #include <sys/vnode.h>
 #include <sys/signalvar.h>
 #include <sys/malloc.h>
+#include <sys/taskqueue.h>
 
 MALLOC_DEFINE(M_NLMDM, "nullmodem", "nullmodem data structures");
 
 static void 	nmdmstart(struct tty *tp);
 static void 	nmdmstop(struct tty *tp, int rw);
-static void 	wakeup_other(struct tty *tp, int flag);
 static void 	nmdminit(dev_t dev);
 
 static d_open_t		nmdmopen;
 static d_close_t	nmdmclose;
-static d_read_t		nmdmread;
-static d_write_t	nmdmwrite;
-static d_ioctl_t	nmdmioctl;
 
 static struct cdevsw nmdm_cdevsw = {
 	.d_version =	D_VERSION,
 	.d_open =	nmdmopen,
 	.d_close =	nmdmclose,
-	.d_read =	nmdmread,
-	.d_write =	nmdmwrite,
-	.d_ioctl =	nmdmioctl,
 	.d_name =	"nmdn",
 	.d_flags =	D_TTY | D_PSEUDO | D_NEEDGIANT,
 };
@@ -85,10 +76,11 @@ static struct cdevsw nmdm_cdevsw = {
 #define BFLAG		CLONE_FLAG0
 
 struct softpart {
-	struct tty	nm_tty;
+	struct tty	*nm_tty;
 	dev_t	dev;
-	int	modemsignals;	/* bits defined in sys/ttycom.h */
-	int	gotbreak;
+	int	dcd;
+	struct task		pt_task;
+	struct softpart		*other;
 };
 
 struct	nm_softc {
@@ -148,21 +140,40 @@ nmdm_clone(void *arg, char *name, int nameen, dev_t *dev)
 }
 
 static void
-nmdm_crossover(struct nm_softc *pti,
-		struct softpart *ourpart,
-		struct softpart *otherpart);
-
-#define GETPARTS(tp, ourpart, otherpart) \
-do {	\
-	struct nm_softc *pti = tp->t_dev->si_drv1; \
-	if (tp == &pti->part1.nm_tty) { \
-		ourpart = &pti->part1; \
-		otherpart = &pti->part2; \
-	} else { \
-		ourpart = &pti->part2; \
-		otherpart = &pti->part1; \
-	}  \
-} while (0)
+nmdm_task_tty(void *arg, int pending __unused)
+{
+	struct tty *tp, *otp;
+	struct softpart *sp;
+	int c;
+
+	tp = arg;
+	sp = tp->t_sc;
+	otp = sp->other->nm_tty;
+	KASSERT(otp != NULL, ("NULL otp in nmdmstart"));
+	KASSERT(otp != tp, ("NULL otp == tp nmdmstart"));
+	if (sp->other->dcd) {
+		if (!(tp->t_state & TS_ISOPEN)) {
+			sp->other->dcd = 0;
+			(void)(*linesw[otp->t_line].l_modem)(otp, 0);
+		}
+	} else {
+		if (tp->t_state & TS_ISOPEN) {
+			sp->other->dcd = 1;
+			(void)(*linesw[otp->t_line].l_modem)(otp, 1);
+		}
+	}
+	if (tp->t_state & TS_TTSTOP)
+		return;
+	while (tp->t_outq.c_cc != 0) {
+		if (otp->t_state & TS_TBLOCK)
+			return;
+		c = getc(&tp->t_outq);
+		if (otp->t_state & TS_ISOPEN)
+			(*linesw[otp->t_line].l_rint)(c, otp);
+	}
+	if (tp->t_outq.c_cc == 0)
+		ttwwakeup(tp);
+}
 
 /*
  * This function creates and initializes a pair of ttys.
@@ -180,20 +191,34 @@ nmdminit(dev_t dev1)
 
 	pt = malloc(sizeof(*pt), M_NLMDM, M_WAITOK | M_ZERO);
 	TAILQ_INSERT_TAIL(&nmdmhead, pt, pt_list);
+
 	dev1->si_drv1 = dev2->si_drv1 = pt;
 
 	pt->part1.dev = dev1;
 	pt->part2.dev = dev2;
-	dev1->si_tty = &pt->part1.nm_tty;
-	dev2->si_tty = &pt->part2.nm_tty;
-	ttyregister(&pt->part1.nm_tty);
-	ttyregister(&pt->part2.nm_tty);
-	pt->part1.nm_tty.t_oproc = nmdmstart;
-	pt->part2.nm_tty.t_oproc = nmdmstart;
-	pt->part1.nm_tty.t_stop = nmdmstop;
-	pt->part2.nm_tty.t_stop = nmdmstop;
-	pt->part2.nm_tty.t_dev = dev1;
-	pt->part1.nm_tty.t_dev = dev2;
+
+	pt->part1.nm_tty = ttymalloc(pt->part1.nm_tty);
+	pt->part1.nm_tty->t_oproc = nmdmstart;
+	pt->part1.nm_tty->t_stop = nmdmstop;
+	pt->part1.nm_tty->t_dev = dev1;
+	pt->part1.nm_tty->t_sc = &pt->part1;
+	TASK_INIT(&pt->part1.pt_task, 0, nmdm_task_tty, pt->part1.nm_tty);
+
+	pt->part2.nm_tty = ttymalloc(pt->part2.nm_tty);
+	pt->part2.nm_tty->t_oproc = nmdmstart;
+	pt->part2.nm_tty->t_stop = nmdmstop;
+	pt->part2.nm_tty->t_dev = dev2;
+	pt->part2.nm_tty->t_sc = &pt->part2;
+	TASK_INIT(&pt->part2.pt_task, 0, nmdm_task_tty, pt->part2.nm_tty);
+
+	pt->part1.other = &pt->part2;
+	pt->part2.other = &pt->part1;
+
+	dev1->si_tty = pt->part1.nm_tty;
+	dev1->si_drv1 = pt;
+
+	dev2->si_tty = pt->part2.nm_tty;
+	dev2->si_drv1 = pt;
 }
 
 /*
@@ -202,380 +227,61 @@ nmdminit(dev_t dev1)
 static	int
 nmdmopen(dev_t dev, int flag, int devtype, struct thread *td)
 {
-	register struct tty *tp, *tp2;
+	struct tty *tp, *tp2;
 	int error;
 	struct nm_softc *pti;
-	struct	softpart *ourpart, *otherpart;
+	struct softpart *sp;
 
 	if (dev->si_drv1 == NULL)
 		nmdminit(dev);
 	pti = dev->si_drv1;
+	if (pti->pt_prison != td->td_ucred->cr_prison)
+		return (EBUSY);
 
-	if (minor(dev) & BFLAG)
-		tp = &pti->part2.nm_tty;
-	else 
-		tp = &pti->part1.nm_tty;
-	GETPARTS(tp, ourpart, otherpart);
-
-	tp2 = &otherpart->nm_tty;
-	ourpart->modemsignals |= TIOCM_LE;
+	tp = dev->si_tty;
+	sp = tp->t_sc;
+	tp2 = sp->other->nm_tty;
 
 	if ((tp->t_state & TS_ISOPEN) == 0) {
 		ttychars(tp);		/* Set up default chars */
 		tp->t_iflag = TTYDEF_IFLAG;
 		tp->t_oflag = TTYDEF_OFLAG;
 		tp->t_lflag = TTYDEF_LFLAG;
+		tp->t_lflag = 0;
 		tp->t_cflag = TTYDEF_CFLAG;
 		tp->t_ispeed = tp->t_ospeed = TTYDEF_SPEED;
+		ttsetwater(tp); /* XXX ? */
 	} else if (tp->t_state & TS_XCLUDE && suser(td)) {
 		return (EBUSY);
-	} else if (pti->pt_prison != td->td_ucred->cr_prison) {
-		return (EBUSY);
 	}
 
-	/*
-	 * If the other side is open we have carrier
-	 */
-	if (tp2->t_state & TS_ISOPEN) {
-		(void)(*linesw[tp->t_line].l_modem)(tp, 1);
-	}
-
-	/*
-	 * And the other side gets carrier as we are now open.
-	 */
-	(void)(*linesw[tp2->t_line].l_modem)(tp2, 1);
-
-	/* External processing makes no sense here */
-	tp->t_lflag &= ~EXTPROC;
-
-	/* 
-	 * Wait here if we don't have carrier.
-	 */
-#if 0
-	while ((tp->t_state & TS_CARR_ON) == 0) {
-		if (flag & FNONBLOCK)
-			break;
-		error = ttysleep(tp, TSA_CARR_ON(tp), TTIPRI | PCATCH,
-				 "nmdopn", 0);
-		if (error)
-			return (error);
-	}
-#endif
-
-	/*
-	 * Give the line disciplin a chance to set this end up.
-	 */
 	error = (*linesw[tp->t_line].l_open)(dev, tp);
-
-	/*
-	 * Wake up the other side.
-	 * Theoretically not needed.
-	 */
-	ourpart->modemsignals |= TIOCM_DTR;
-	nmdm_crossover(pti, ourpart, otherpart);
-	if (error == 0)
-		wakeup_other(tp, FREAD|FWRITE); /* XXX */
 	return (error);
 }
 
-/*
- * Device closed again
- */
-static	int
+static int
 nmdmclose(dev_t dev, int flag, int mode, struct thread *td)
 {
-	register struct tty *tp, *tp2;
-	int err;
-	struct softpart *ourpart, *otherpart;
-
-	/*
-	 * let the other end know that the game is up
-	 */
-	tp = dev->si_tty;
-	GETPARTS(tp, ourpart, otherpart);
-	tp2 = &otherpart->nm_tty;
-	(void)(*linesw[tp2->t_line].l_modem)(tp2, 0);
-
-	/*
-	 * XXX MDMBUF makes no sense for nmdms but would inhibit the above
-	 * l_modem().  CLOCAL makes sense but isn't supported.   Special
-	 * l_modem()s that ignore carrier drop make no sense for nmdms but
-	 * may be in use because other parts of the line discipline make
-	 * sense for nmdms.  Recover by doing everything that a normal
-	 * ttymodem() would have done except for sending a SIGHUP.
-	 */
-	if (tp2->t_state & TS_ISOPEN) {
-		tp2->t_state &= ~(TS_CARR_ON | TS_CONNECTED);
-		tp2->t_state |= TS_ZOMBIE;
-		ttyflush(tp2, FREAD | FWRITE);
-	}
 
-	err = (*linesw[tp->t_line].l_close)(tp, flag);
-	ourpart->modemsignals &= ~TIOCM_DTR;
-	nmdm_crossover(dev->si_drv1, ourpart, otherpart);
-	(void) ttyclose(tp);
-	return (err);
+	return (ttyclose(dev->si_tty));
 }
 
-/*
- * handle read(2) request from userland
- */
-static	int
-nmdmread(dev_t dev, struct uio *uio, int flag)
-{
-	int error = 0;
-	struct tty *tp, *tp2;
-	struct softpart *ourpart, *otherpart;
-
-	tp = dev->si_tty;
-	GETPARTS(tp, ourpart, otherpart);
-	tp2 = &otherpart->nm_tty;
-
-#if 0
-	if (tp2->t_state & TS_ISOPEN) {
-		error = (*linesw[tp->t_line].l_read)(tp, uio, flag);
-		wakeup_other(tp, FWRITE);
-	} else {
-		if (flag & IO_NDELAY) {
-			return (EWOULDBLOCK);
-		}
-		error = tsleep(TSA_PTC_READ(tp),
-				TTIPRI | PCATCH, "nmdout", 0);
-		}
-	}
-#else
-	if ((error = (*linesw[tp->t_line].l_read)(tp, uio, flag)) == 0)
-		wakeup_other(tp, FWRITE);
-#endif
-	return (error);
-}
-
-/*
- * Write to pseudo-tty.
- * Wakeups of controlling tty will happen
- * indirectly, when tty driver calls nmdmstart.
- */
-static	int
-nmdmwrite(dev_t dev, struct uio *uio, int flag)
-{
-	register u_char *cp = 0;
-	register int cc = 0;
-	u_char locbuf[BUFSIZ];
-	int cnt = 0;
-	int error = 0;
-	struct tty *tp1, *tp;
-	struct softpart *ourpart, *otherpart;
-
-	tp1 = dev->si_tty;
-	/*
-	 * Get the other tty struct.
-	 * basically we are writing into the INPUT side of the other device.
-	 */
-	GETPARTS(tp1, ourpart, otherpart);
-	tp = &otherpart->nm_tty;
-
-again:
-	if ((tp->t_state & TS_ISOPEN) == 0) 
-		return (EIO);
-	while (uio->uio_resid > 0 || cc > 0) {
-		/*
-		 * Fill up the buffer if it's empty
-		 */
-		if (cc == 0) {
-			cc = min(uio->uio_resid, BUFSIZ);
-			cp = locbuf;
-			error = uiomove((caddr_t)cp, cc, uio);
-			if (error)
-				return (error);
-			/* check again for safety */
-			if ((tp->t_state & TS_ISOPEN) == 0) {
-				/* adjust for data copied in but not written */
-				uio->uio_resid += cc;
-				return (EIO);
-			}
-		}
-		while (cc > 0) {
-			if (((tp->t_rawq.c_cc + tp->t_canq.c_cc) >= (TTYHOG-2))
-			&& ((tp->t_canq.c_cc > 0) || !(tp->t_iflag&ICANON))) {
-				/*
-	 			 * Come here to wait for space in outq,
-				 * or space in rawq, or an empty canq.
-	 			 */
-				wakeup(TSA_HUP_OR_INPUT(tp));
-				if ((tp->t_state & TS_CONNECTED) == 0) {
-					/*
-					 * Data piled up because not connected.
-					 * Adjust for data copied in but
-					 * not written.
-					 */
-					uio->uio_resid += cc;
-					return (EIO);
-				}
-				if (flag & IO_NDELAY) {
-					/*
-				         * Don't wait if asked not to.
-					 * Adjust for data copied in but
-					 * not written.
-					 */
-					uio->uio_resid += cc;
-					if (cnt == 0)
-						return (EWOULDBLOCK);
-					return (0);
-				}
-				error = tsleep(TSA_PTC_WRITE(tp),
-						TTOPRI | PCATCH, "nmdout", 0);
-				if (error) {
-					/*
-					 * Tsleep returned (signal?).
-					 * Go find out what the user wants.
-					 * adjust for data copied in but
-					 * not written
-					 */
-					uio->uio_resid += cc;
-					return (error);
-				}
-				goto again;
-			}
-			(*linesw[tp->t_line].l_rint)(*cp++, tp);
-			cnt++;
-			cc--;
-		}
-		cc = 0;
-	}
-	return (0);
-}
-
-/*
- * Start output on pseudo-tty.
- * Wake up process selecting or sleeping for input from controlling tty.
- */
 static void
 nmdmstart(struct tty *tp)
 {
-	register struct nm_softc *pti = tp->t_dev->si_drv1;
+	struct softpart *pt;
 
-	if (tp->t_state & TS_TTSTOP)
-		return;
-	pti->pt_flags &= ~PF_STOPPED;
-	wakeup_other(tp, FREAD);
+	pt = tp->t_sc;
+	taskqueue_enqueue(taskqueue_swi_giant, &pt->pt_task);
 }
 
-/* Wakes up the OTHER tty;*/
 static void
-wakeup_other(struct tty *tp, int flag)
+nmdmstop(struct tty *tp, int flush)
 {
-	struct softpart *ourpart, *otherpart;
+	struct softpart *pt;
 
-	GETPARTS(tp, ourpart, otherpart);
-	if (flag & FREAD) {
-		selwakeuppri(&otherpart->nm_tty.t_rsel, TTIPRI);
-		wakeup(TSA_PTC_READ((&otherpart->nm_tty)));
-	}
-	if (flag & FWRITE) {
-		selwakeuppri(&otherpart->nm_tty.t_wsel, TTOPRI);
-		wakeup(TSA_PTC_WRITE((&otherpart->nm_tty)));
-	}
-}
-
-/*
- * stopped output on tty, called when device is closed
- */
-static	void
-nmdmstop(register struct tty *tp, int flush)
-{
-	struct nm_softc *pti = tp->t_dev->si_drv1;
-	int flag;
-
-	/* note: FLUSHREAD and FLUSHWRITE already ok */
-	if (flush == 0) {
-		flush = TIOCPKT_STOP;
-		pti->pt_flags |= PF_STOPPED;
-	} else
-		pti->pt_flags &= ~PF_STOPPED;
-	/* change of perspective */
-	flag = 0;
-	if (flush & FREAD)
-		flag |= FWRITE;
-	if (flush & FWRITE)
-		flag |= FREAD;
-	wakeup_other(tp, flag);
-}
-
-/*
- * handle ioctl(2) request from userland
- */
-static	int
-nmdmioctl(dev_t dev, u_long cmd, caddr_t data, int flag, struct thread *td)
-{
-	register struct tty *tp = dev->si_tty;
-	struct nm_softc *pti = dev->si_drv1;
-	int error, s;
-	register struct tty *tp2;
-	struct softpart *ourpart, *otherpart;
-
-	s = spltty();
-	GETPARTS(tp, ourpart, otherpart);
-	tp2 = &otherpart->nm_tty;
-
-	error = (*linesw[tp->t_line].l_ioctl)(tp, cmd, data, flag, td);
-	if (error == ENOIOCTL)
-		 error = ttioctl(tp, cmd, data, flag);
-	if (error == ENOIOCTL) {
-		switch (cmd) {
-		case TIOCSBRK:
-			otherpart->gotbreak = 1;
-			break;
-		case TIOCCBRK:
-			break;
-		case TIOCSDTR:
-			ourpart->modemsignals |= TIOCM_DTR;
-			break;
-		case TIOCCDTR:
-			ourpart->modemsignals &= TIOCM_DTR;
-			break;
-		case TIOCMSET:
-			ourpart->modemsignals = *(int *)data;
-			otherpart->modemsignals = *(int *)data;
-			break;
-		case TIOCMBIS:
-			ourpart->modemsignals |= *(int *)data;
-			break;
-		case TIOCMBIC:
-			ourpart->modemsignals &= ~(*(int *)data);
-			otherpart->modemsignals &= ~(*(int *)data);
-			break;
-		case TIOCMGET:
-			*(int *)data = ourpart->modemsignals;
-			break;
-		case TIOCMSDTRWAIT:
-			break;
-		case TIOCMGDTRWAIT:
-			*(int *)data = 0;
-			break;
-		case TIOCTIMESTAMP:
-			/* FALLTHROUGH */
-		case TIOCDCDTIMESTAMP:
-		default:
-			splx(s);
-			error = ENOTTY;
-			return (error);
-		}
-		error = 0;
-		nmdm_crossover(pti, ourpart, otherpart);
-	}
-	splx(s);
-	return (error);
-}
-
-static void
-nmdm_crossover(struct nm_softc *pti, struct softpart *ourpart,
-    struct softpart *otherpart)
-{
-	otherpart->modemsignals &= ~(TIOCM_CTS|TIOCM_CAR);
-	if (ourpart->modemsignals & TIOCM_RTS)
-		otherpart->modemsignals |= TIOCM_CTS;
-	if (ourpart->modemsignals & TIOCM_DTR)
-		otherpart->modemsignals |= TIOCM_CAR;
+	pt = tp->t_sc;
+	taskqueue_enqueue(taskqueue_swi_giant, &pt->pt_task);
 }
 
 /*