Support /dev/tun cloning. Ansify if_tun.c while I'm there.

Only tun0 -> tun32767 may now be opened as struct ifnet's if_unit
is a short.

It's now possible to open /dev/tun and get a handle back for an available
tun device (use devname to find out what you got).

The implementation uses rman by popular demand (and against my judgement)
to track opened devices and uses the new dev_depends() to ensure that
all make_dev()d devices go away before the module is unloaded.

Reviewed by:	phk

sys/fs/devfs/devfs_vnops.c

@@ -572,7 +572,8 @@ devfs_reclaim(ap)
 	vp->v_data = NULL;
 	if (vp->v_rdev != NODEV && vp->v_rdev != NULL) {
 		i = vcount(vp);
-		if ((vp->v_rdev->si_flags & SI_CHEAPCLONE) && i == 0)
+		if ((vp->v_rdev->si_flags & SI_CHEAPCLONE) && i == 0 &&
+		    (vp->v_rdev->si_flags & SI_NAMED))
 			destroy_dev(vp->v_rdev);
 	}
 	return (0);

sys/net/if_tun.c

@@ -36,42 +36,46 @@
 #include <sys/uio.h>
 #include <sys/vnode.h>
 #include <sys/malloc.h>
+#include <machine/bus.h>	/* XXX Shouldn't really be required ! */
+#include <sys/rman.h>
 
 #include <net/if.h>
 #include <net/if_types.h>
 #include <net/route.h>
 #include <net/intrq.h>
-
 #ifdef INET
 #include <netinet/in.h>
 #endif
-
 #include <net/bpf.h>
-
 #include <net/if_tunvar.h>
 #include <net/if_tun.h>
 
-static MALLOC_DEFINE(M_TUN, "tun", "Tunnel Interface");
-
-static void tuncreate __P((dev_t dev));
-
 #define TUNDEBUG	if (tundebug) printf
+#define	TUNNAME		"tun"
+#define	TUN_MAXUNIT	0x7fff	/* ifp->if_unit is only 15 bits */
+
+static MALLOC_DEFINE(M_TUN, TUNNAME, "Tunnel Interface");
 static int tundebug = 0;
 static struct tun_softc *tunhead = NULL;
+static struct rman tununits[1];
+static udev_t tunbasedev = NOUDEV;
 SYSCTL_INT(_debug, OID_AUTO, if_tun_debug, CTLFLAG_RW, &tundebug, 0, "");
 
-static int tunoutput __P((struct ifnet *, struct mbuf *, struct sockaddr *,
-	    struct rtentry *rt));
-static int tunifioctl __P((struct ifnet *, u_long, caddr_t));
-static int tuninit __P((struct ifnet *));
-static void tunstart __P((struct ifnet *));
+static void	tunclone(void *arg, char *name, int namelen, dev_t *dev);
+static void	tuncreate(dev_t dev);
+static int	tunifioctl(struct ifnet *, u_long, caddr_t);
+static int	tuninit(struct ifnet *);
+static int	tunmodevent(module_t, int, void *);
+static int	tunoutput(struct ifnet *, struct mbuf *, struct sockaddr *,
+		    struct rtentry *rt);
+static void	tunstart(struct ifnet *);
 
-static	d_open_t	tunopen;
-static	d_close_t	tunclose;
-static	d_read_t	tunread;
-static	d_write_t	tunwrite;
-static	d_ioctl_t	tunioctl;
-static	d_poll_t	tunpoll;
+static d_open_t		tunopen;
+static d_close_t	tunclose;
+static d_read_t		tunread;
+static d_write_t	tunwrite;
+static d_ioctl_t	tunioctl;
+static d_poll_t		tunpoll;
 
 #define CDEV_MAJOR 52
 static struct cdevsw tun_cdevsw = {
@@ -83,35 +87,53 @@ static struct cdevsw tun_cdevsw = {
 	/* poll */	tunpoll,
 	/* mmap */	nommap,
 	/* strategy */	nostrategy,
-	/* name */	"tun",
+	/* name */	TUNNAME,
 	/* maj */	CDEV_MAJOR,
 	/* dump */	nodump,
 	/* psize */	nopsize,
 	/* flags */	0,
 };
 
-static void tun_clone __P((void *arg, char *name, int namelen, dev_t *dev));
-
 static void
-tun_clone(arg, name, namelen, dev)
-	void *arg;
-	char *name;
-	int namelen;
-	dev_t *dev;
+tunclone(void *arg, char *name, int namelen, dev_t *dev)
 {
+	struct resource *r;
+	int err;
 	int u;
 
 	if (*dev != NODEV)
 		return;
-	if (dev_stdclone(name, NULL, "tun", &u) != 1)
-		return;
+
+	if (strcmp(name, TUNNAME) == 0) {
+		r = rman_reserve_resource(tununits, 0, TUN_MAXUNIT, 1,
+		    RF_ALLOCATED | RF_ACTIVE, NULL);
+		u = rman_get_start(r);
+		err = rman_release_resource(r);
+		KASSERT(err == 0, ("Unexpected failure releasing resource"));
+		*dev = makedev(CDEV_MAJOR, unit2minor(u));
+		if ((*dev)->si_flags & SI_NAMED)
+			return;	/* Already make_dev()d */
+	} else if (dev_stdclone(name, NULL, TUNNAME, &u) != 1)
+		return;	/* Don't recognise the name */
+
 	*dev = make_dev(&tun_cdevsw, unit2minor(u),
 	    UID_ROOT, GID_WHEEL, 0600, "tun%d", u);
-	(*dev)->si_flags |= SI_CHEAPCLONE;
+
+	/*
+	 * All devices depend on tunbasedev so that we can simply
+	 * destroy_dev() this device at module unload time to get
+	 * rid of all our make_dev()d resources.
+	 */
+	if (tunbasedev == NOUDEV)
+		tunbasedev = (*dev)->si_udev;
+	else {
+		(*dev)->si_flags |= SI_CHEAPCLONE;
+		dev_depends(udev2dev(tunbasedev, 0), *dev);
+	}
 }
 
 static int
-tun_modevent(module_t mod, int type, void *data) 
+tunmodevent(module_t mod, int type, void *data) 
 {
 	static eventhandler_tag tag;
 	struct tun_softc *tp;
@@ -120,19 +142,44 @@ tun_modevent(module_t mod, int type, void *data)
 
 	switch (type) { 
 	case MOD_LOAD: 
-		tag = EVENTHANDLER_REGISTER(dev_clone, tun_clone, 0, 1000);
+		tag = EVENTHANDLER_REGISTER(dev_clone, tunclone, 0, 1000);
 		if (tag == NULL)
 			return (ENOMEM);
-		err = cdevsw_add(&tun_cdevsw);
+		if (!devfs_present) {
+			err = cdevsw_add(&tun_cdevsw);
+			if (err != 0) {
+				EVENTHANDLER_DEREGISTER(dev_clone, tag);
+				return (err);
+			}
+		}
+		tununits->rm_type = RMAN_ARRAY;
+		tununits->rm_descr = "open if_tun units";
+		err = rman_init(tununits);
 		if (err != 0) {
+			cdevsw_remove(&tun_cdevsw);
+			EVENTHANDLER_DEREGISTER(dev_clone, tag);
+			return (err);
+		}
+		err = rman_manage_region(tununits, 0, TUN_MAXUNIT);
+		if (err != 0) {
+			printf("%s: tununits: rman_manage_region: Failed %d\n",
+			    TUNNAME, err);
+			rman_fini(tununits);
+			cdevsw_remove(&tun_cdevsw);
 			EVENTHANDLER_DEREGISTER(dev_clone, tag);
 			return (err);
 		}
 		break; 
 	case MOD_UNLOAD: 
+		err = rman_fini(tununits);
+		if (err != 0)
+			return (err);
+		EVENTHANDLER_DEREGISTER(dev_clone, tag);
+
 		while (tunhead != NULL) {
-			if (tunhead->tun_flags & TUN_OPEN)
-				return (EBUSY);
+			KASSERT((tunhead->tun_flags & TUN_OPEN) == 0,
+			    ("tununits is out of sync - unit %d",
+			    tunhead->tun_if.if_unit));
 			tp = tunhead;
 			dev = makedev(tun_cdevsw.d_maj,
 			    unit2minor(tp->tun_if.if_unit));
@@ -141,11 +188,18 @@ tun_modevent(module_t mod, int type, void *data)
 			bpfdetach(&tp->tun_if);
 			if_detach(&tp->tun_if);
 			KASSERT(dev->si_flags & SI_NAMED, ("Missing make_dev"));
-			destroy_dev(dev);
 			FREE(tp, M_TUN);
 		}
-		cdevsw_remove(&tun_cdevsw);
-		EVENTHANDLER_DEREGISTER(dev_clone, tag);
+
+		/*
+		 * Destroying tunbasedev results in all of our make_dev()s
+		 * conveniently going away.
+		 */
+		if (tunbasedev != NOUDEV)
+			destroy_dev(udev2dev(tunbasedev, 0));
+
+		if (!devfs_present)
+			cdevsw_remove(&tun_cdevsw);
 		break;
 	} 
 	return 0; 
@@ -153,15 +207,14 @@ tun_modevent(module_t mod, int type, void *data)
 
 static moduledata_t tun_mod = { 
 	"if_tun", 
-	tun_modevent, 
+	tunmodevent, 
 	0
 }; 
 
 DECLARE_MODULE(if_tun, tun_mod, SI_SUB_PSEUDO, SI_ORDER_ANY);
 
 static void
-tunstart(ifp)
-	struct ifnet *ifp;
+tunstart(struct ifnet *ifp)
 {
 	struct tun_softc *tp = ifp->if_softc;
 
@@ -175,8 +228,7 @@ tunstart(ifp)
 }
 
 static void
-tuncreate(dev)
-	dev_t dev;
+tuncreate(dev_t dev)
 {
 	struct tun_softc *sc;
 	struct ifnet *ifp;
@@ -192,7 +244,7 @@ tuncreate(dev)
 
 	ifp = &sc->tun_if;
 	ifp->if_unit = dev2unit(dev);
-	ifp->if_name = "tun";
+	ifp->if_name = TUNNAME;
 	ifp->if_mtu = TUNMTU;
 	ifp->if_ioctl = tunifioctl;
 	ifp->if_output = tunoutput;
@@ -206,31 +258,35 @@ tuncreate(dev)
 	dev->si_drv1 = sc;
 }
 
-/*
- * tunnel open.  We assume that any tun_clone() call is immediately
- * followed by a call to tunopen() - otherwise nothing will ever
- * destroy_dev() the specinfo.
- */
-static	int
-tunopen(dev, flag, mode, p)
-	dev_t	dev;
-	int	flag, mode;
-	struct proc *p;
+static int
+tunopen(dev_t dev, int flag, int mode, struct proc *p)
 {
+	struct resource *r;
 	struct ifnet	*ifp;
 	struct tun_softc *tp;
+	int unit;
+
+	unit = dev2unit(dev);
+	if (unit > TUN_MAXUNIT)
+		return (ENXIO);
+
+	r = rman_reserve_resource(tununits, unit, unit, 1,
+	    RF_ALLOCATED | RF_ACTIVE, NULL);
+	if (r == NULL)
+		return (EBUSY);
 
 	tp = dev->si_drv1;
 	if (!tp) {
 		tuncreate(dev);
 		tp = dev->si_drv1;
 	}
-	if (tp->tun_flags & TUN_OPEN)
-		return EBUSY;
+	KASSERT(!(tp->tun_flags & TUN_OPEN), ("Resource & flags out-of-sync"));
+	tp->r_unit = r;
 	tp->tun_pid = p->p_pid;
 	ifp = &tp->tun_if;
 	tp->tun_flags |= TUN_OPEN;
 	TUNDEBUG("%s%d: open\n", ifp->if_name, ifp->if_unit);
+
 	return (0);
 }
 
@@ -239,19 +295,18 @@ tunopen(dev, flag, mode, p)
  * routing info
  */
 static	int
-tunclose(dev, foo, bar, p)
-	dev_t dev;
-	int foo;
-	int bar;
-	struct proc *p;
+tunclose(dev_t dev, int foo, int bar, struct proc *p)
 {
-	register int	s;
 	struct tun_softc *tp;
-	struct ifnet	*ifp;
+	struct ifnet *ifp;
+	int s;
+	int err;
 
 	tp = dev->si_drv1;
 	ifp = &tp->tun_if;
 
+	err = rman_release_resource(tp->r_unit);
+	KASSERT(err == 0, ("Unit %d not marked open", ifp->if_unit));
 	tp->tun_flags &= ~TUN_OPEN;
 	tp->tun_pid = 0;
 
@@ -287,8 +342,7 @@ tunclose(dev, foo, bar, p)
 }
 
 static int
-tuninit(ifp)
-	struct ifnet *ifp;
+tuninit(struct ifnet *ifp)
 {
 	struct tun_softc *tp = ifp->if_softc;
 	register struct ifaddr *ifa;
@@ -327,10 +381,7 @@ tuninit(ifp)
  * Process an ioctl request.
  */
 int
-tunifioctl(ifp, cmd, data)
-	struct ifnet *ifp;
-	u_long	cmd;
-	caddr_t	data;
+tunifioctl(struct ifnet *ifp, u_long cmd, caddr_t data)
 {
 	struct ifreq *ifr = (struct ifreq *)data;
 	struct tun_softc *tp = ifp->if_softc;
@@ -374,11 +425,11 @@ tunifioctl(ifp, cmd, data)
  * tunoutput - queue packets from higher level ready to put out.
  */
 int
-tunoutput(ifp, m0, dst, rt)
-	struct ifnet   *ifp;
-	struct mbuf    *m0;
-	struct sockaddr *dst;
-	struct rtentry *rt;
+tunoutput(
+	struct ifnet *ifp,
+	struct mbuf *m0,
+	struct sockaddr *dst,
+	struct rtentry *rt)
 {
 	struct tun_softc *tp = ifp->if_softc;
 
@@ -465,12 +516,7 @@ tunoutput(ifp, m0, dst, rt)
  * the cdevsw interface is now pretty minimal.
  */
 static	int
-tunioctl(dev, cmd, data, flag, p)
-	dev_t		dev;
-	u_long		cmd;
-	caddr_t		data;
-	int		flag;
-	struct proc	*p;
+tunioctl(dev_t dev, u_long cmd, caddr_t data, int flag, struct proc *p)
 {
 	int		s;
 	int		error;
@@ -583,10 +629,7 @@ tunioctl(dev, cmd, data, flag, p)
  * least as much of a packet as can be read.
  */
 static	int
-tunread(dev, uio, flag)
-	dev_t dev;
-	struct uio *uio;
-	int flag;
+tunread(dev_t dev, struct uio *uio, int flag)
 {
 	struct tun_softc *tp = dev->si_drv1;
 	struct ifnet	*ifp = &tp->tun_if;
@@ -640,10 +683,7 @@ tunread(dev, uio, flag)
  * the cdevsw write interface - an atomic write is a packet - or else!
  */
 static	int
-tunwrite(dev, uio, flag)
-	dev_t dev;
-	struct uio *uio;
-	int flag;
+tunwrite(dev_t dev, struct uio *uio, int flag)
 {
 	struct tun_softc *tp = dev->si_drv1;
 	struct ifnet	*ifp = &tp->tun_if;
@@ -749,10 +789,7 @@ tunwrite(dev, uio, flag)
  * anyway, it either accepts the packet or drops it.
  */
 static	int
-tunpoll(dev, events, p)
-	dev_t dev;
-	int events;
-	struct proc *p;
+tunpoll(dev_t dev, int events, struct proc *p)
 {
 	int		s;
 	struct tun_softc *tp = dev->si_drv1;

sys/net/if_tunvar.h

@@ -50,6 +50,7 @@ struct tun_softc {
 	struct	selinfo	tun_wsel;	/* write select (not used) */
 
 	struct	tun_softc *next;	/* Next softc in list */
+	struct	resource *r_unit;	/* resource allocated for this unit */
 };
 
 #endif /* !_NET_IF_TUNVAR_H_ */