if_tun.c revision 126845 
1/*	$NetBSD: if_tun.c,v 1.14 1994/06/29 06:36:25 cgd Exp $	*/
2
3/*
4 * Copyright (c) 1988, Julian Onions <jpo@cs.nott.ac.uk>
5 * Nottingham University 1987.
6 *
7 * This source may be freely distributed, however I would be interested
8 * in any changes that are made.
9 *
10 * This driver takes packets off the IP i/f and hands them up to a
11 * user process to have its wicked way with. This driver has it's
12 * roots in a similar driver written by Phil Cockcroft (formerly) at
13 * UCL. This driver is based much more on read/write/poll mode of
14 * operation though.
15 *
16 * $FreeBSD: head/sys/net/if_tun.c 126845 2004-03-11 12:58:55Z phk $
17 */
18
19#include "opt_atalk.h"
20#include "opt_inet.h"
21#include "opt_inet6.h"
22#include "opt_ipx.h"
23#include "opt_mac.h"
24
25#include <sys/param.h>
26#include <sys/proc.h>
27#include <sys/systm.h>
28#include <sys/mac.h>
29#include <sys/mbuf.h>
30#include <sys/module.h>
31#include <sys/socket.h>
32#include <sys/filio.h>
33#include <sys/sockio.h>
34#include <sys/ttycom.h>
35#include <sys/poll.h>
36#include <sys/signalvar.h>
37#include <sys/filedesc.h>
38#include <sys/kernel.h>
39#include <sys/sysctl.h>
40#include <sys/conf.h>
41#include <sys/uio.h>
42#include <sys/vnode.h>
43#include <sys/malloc.h>
44#include <sys/random.h>
45
46#include <net/if.h>
47#include <net/if_types.h>
48#include <net/netisr.h>
49#include <net/route.h>
50#ifdef INET
51#include <netinet/in.h>
52#endif
53#include <net/bpf.h>
54#include <net/if_tun.h>
55
56#include <sys/queue.h>
57
58struct tun_softc {
59	TAILQ_ENTRY(tun_softc)	tun_list;
60	int			tun_unit;
61	dev_t			tun_dev;
62	u_short	tun_flags;		/* misc flags */
63#define	TUN_OPEN	0x0001
64#define	TUN_INITED	0x0002
65#define	TUN_RCOLL	0x0004
66#define	TUN_IASET	0x0008
67#define	TUN_DSTADDR	0x0010
68#define	TUN_LMODE	0x0020
69#define	TUN_RWAIT	0x0040
70#define	TUN_ASYNC	0x0080
71#define	TUN_IFHEAD	0x0100
72
73#define TUN_READY       (TUN_OPEN | TUN_INITED)
74
75	struct proc		*tun_proc;	/* Owning process */
76	struct	ifnet tun_if;		/* the interface */
77	struct  sigio *tun_sigio;	/* information for async I/O */
78	struct	selinfo	tun_rsel;	/* read select */
79};
80
81#define TUNDEBUG	if (tundebug) if_printf
82#define	TUNNAME		"tun"
83
84static MALLOC_DEFINE(M_TUN, TUNNAME, "Tunnel Interface");
85static int tundebug = 0;
86static struct clonedevs *tunclones;
87static TAILQ_HEAD(,tun_softc)	tunhead = TAILQ_HEAD_INITIALIZER(tunhead);
88SYSCTL_INT(_debug, OID_AUTO, if_tun_debug, CTLFLAG_RW, &tundebug, 0, "");
89
90static void	tunclone(void *arg, char *name, int namelen, dev_t *dev);
91static void	tuncreate(dev_t dev);
92static int	tunifioctl(struct ifnet *, u_long, caddr_t);
93static int	tuninit(struct ifnet *);
94static int	tunmodevent(module_t, int, void *);
95static int	tunoutput(struct ifnet *, struct mbuf *, struct sockaddr *,
96		    struct rtentry *rt);
97static void	tunstart(struct ifnet *);
98
99static d_open_t		tunopen;
100static d_close_t	tunclose;
101static d_read_t		tunread;
102static d_write_t	tunwrite;
103static d_ioctl_t	tunioctl;
104static d_poll_t		tunpoll;
105
106static struct cdevsw tun_cdevsw = {
107	.d_version =	D_VERSION,
108	.d_flags =	D_PSEUDO | D_NEEDGIANT,
109	.d_open =	tunopen,
110	.d_close =	tunclose,
111	.d_read =	tunread,
112	.d_write =	tunwrite,
113	.d_ioctl =	tunioctl,
114	.d_poll =	tunpoll,
115	.d_name =	TUNNAME,
116};
117
118static void
119tunclone(void *arg, char *name, int namelen, dev_t *dev)
120{
121	int u, i;
122
123	if (*dev != NODEV)
124		return;
125
126	if (strcmp(name, TUNNAME) == 0) {
127		u = -1;
128	} else if (dev_stdclone(name, NULL, TUNNAME, &u) != 1)
129		return;	/* Don't recognise the name */
130	if (u != -1 && u > IF_MAXUNIT)
131		return;	/* Unit number too high */
132
133	/* find any existing device, or allocate new unit number */
134	i = clone_create(&tunclones, &tun_cdevsw, &u, dev, 0);
135	if (i) {
136		/* No preexisting dev_t, create one */
137		*dev = make_dev(&tun_cdevsw, unit2minor(u),
138		    UID_UUCP, GID_DIALER, 0600, "tun%d", u);
139		if (*dev != NULL)
140			(*dev)->si_flags |= SI_CHEAPCLONE;
141	}
142}
143
144static int
145tunmodevent(module_t mod, int type, void *data)
146{
147	static eventhandler_tag tag;
148	struct tun_softc *tp;
149	dev_t dev;
150
151	switch (type) {
152	case MOD_LOAD:
153		clone_setup(&tunclones);
154		tag = EVENTHANDLER_REGISTER(dev_clone, tunclone, 0, 1000);
155		if (tag == NULL)
156			return (ENOMEM);
157		break;
158	case MOD_UNLOAD:
159		EVENTHANDLER_DEREGISTER(dev_clone, tag);
160
161		while (!TAILQ_EMPTY(&tunhead)) {
162			tp = TAILQ_FIRST(&tunhead);
163			KASSERT((tp->tun_flags & TUN_OPEN) == 0,
164			    ("tununits is out of sync - unit %d",
165			    tp->tun_if.if_dunit));
166			TAILQ_REMOVE(&tunhead, tp, tun_list);
167			dev = tp->tun_dev;
168			bpfdetach(&tp->tun_if);
169			if_detach(&tp->tun_if);
170			destroy_dev(dev);
171			free(tp, M_TUN);
172		}
173		clone_cleanup(&tunclones);
174		break;
175	}
176	return 0;
177}
178
179static moduledata_t tun_mod = {
180	"if_tun",
181	tunmodevent,
182	0
183};
184
185DECLARE_MODULE(if_tun, tun_mod, SI_SUB_PSEUDO, SI_ORDER_ANY);
186
187static void
188tunstart(struct ifnet *ifp)
189{
190	struct tun_softc *tp = ifp->if_softc;
191
192	if (tp->tun_flags & TUN_RWAIT) {
193		tp->tun_flags &= ~TUN_RWAIT;
194		wakeup(tp);
195	}
196	if (tp->tun_flags & TUN_ASYNC && tp->tun_sigio)
197		pgsigio(&tp->tun_sigio, SIGIO, 0);
198	selwakeuppri(&tp->tun_rsel, PZERO + 1);
199}
200
201static void
202tuncreate(dev_t dev)
203{
204	struct tun_softc *sc;
205	struct ifnet *ifp;
206
207	dev->si_flags &= ~SI_CHEAPCLONE;
208
209	MALLOC(sc, struct tun_softc *, sizeof(*sc), M_TUN, M_WAITOK | M_ZERO);
210	sc->tun_flags = TUN_INITED;
211	sc->tun_dev = dev;
212	TAILQ_INSERT_TAIL(&tunhead, sc, tun_list);
213
214	ifp = &sc->tun_if;
215	if_initname(ifp, TUNNAME, dev2unit(dev));
216	ifp->if_mtu = TUNMTU;
217	ifp->if_ioctl = tunifioctl;
218	ifp->if_output = tunoutput;
219	ifp->if_start = tunstart;
220	ifp->if_flags = IFF_POINTOPOINT | IFF_MULTICAST;
221	ifp->if_type = IFT_PPP;
222	ifp->if_snd.ifq_maxlen = ifqmaxlen;
223	ifp->if_softc = sc;
224	if_attach(ifp);
225	bpfattach(ifp, DLT_NULL, sizeof(u_int));
226	dev->si_drv1 = sc;
227}
228
229static int
230tunopen(dev_t dev, int flag, int mode, struct thread *td)
231{
232	struct ifnet	*ifp;
233	struct tun_softc *tp;
234
235	tp = dev->si_drv1;
236	if (!tp) {
237		tuncreate(dev);
238		tp = dev->si_drv1;
239	}
240
241	if (tp->tun_proc != NULL && tp->tun_proc != td->td_proc)
242		return (EBUSY);
243	tp->tun_proc = td->td_proc;
244
245	tp->tun_flags |= TUN_OPEN;
246	ifp = &tp->tun_if;
247	TUNDEBUG(ifp, "open\n");
248
249	return (0);
250}
251
252/*
253 * tunclose - close the device - mark i/f down & delete
254 * routing info
255 */
256static	int
257tunclose(dev_t dev, int foo, int bar, struct thread *td)
258{
259	struct tun_softc *tp;
260	struct ifnet *ifp;
261	int s;
262
263	tp = dev->si_drv1;
264	ifp = &tp->tun_if;
265
266	tp->tun_flags &= ~TUN_OPEN;
267	tp->tun_proc = NULL;
268
269	/*
270	 * junk all pending output
271	 */
272	IF_DRAIN(&ifp->if_snd);
273
274	if (ifp->if_flags & IFF_UP) {
275		s = splimp();
276		if_down(ifp);
277		splx(s);
278	}
279
280	if (ifp->if_flags & IFF_RUNNING) {
281		struct ifaddr *ifa;
282
283		s = splimp();
284		/* find internet addresses and delete routes */
285		TAILQ_FOREACH(ifa, &ifp->if_addrhead, ifa_link)
286			if (ifa->ifa_addr->sa_family == AF_INET)
287				rtinit(ifa, (int)RTM_DELETE,
288				    tp->tun_flags & TUN_DSTADDR ? RTF_HOST : 0);
289		ifp->if_flags &= ~IFF_RUNNING;
290		splx(s);
291	}
292
293	funsetown(&tp->tun_sigio);
294	selwakeuppri(&tp->tun_rsel, PZERO + 1);
295	TUNDEBUG (ifp, "closed\n");
296	return (0);
297}
298
299static int
300tuninit(struct ifnet *ifp)
301{
302	struct tun_softc *tp = ifp->if_softc;
303	struct ifaddr *ifa;
304	int error = 0;
305
306	TUNDEBUG(ifp, "tuninit\n");
307
308	ifp->if_flags |= IFF_UP | IFF_RUNNING;
309	getmicrotime(&ifp->if_lastchange);
310
311	for (ifa = TAILQ_FIRST(&ifp->if_addrhead); ifa;
312	     ifa = TAILQ_NEXT(ifa, ifa_link)) {
313		if (ifa->ifa_addr == NULL)
314			error = EFAULT;
315			/* XXX: Should maybe return straight off? */
316		else {
317#ifdef INET
318			if (ifa->ifa_addr->sa_family == AF_INET) {
319			    struct sockaddr_in *si;
320
321			    si = (struct sockaddr_in *)ifa->ifa_addr;
322			    if (si->sin_addr.s_addr)
323				    tp->tun_flags |= TUN_IASET;
324
325			    si = (struct sockaddr_in *)ifa->ifa_dstaddr;
326			    if (si && si->sin_addr.s_addr)
327				    tp->tun_flags |= TUN_DSTADDR;
328			}
329#endif
330		}
331	}
332	return (error);
333}
334
335/*
336 * Process an ioctl request.
337 */
338static int
339tunifioctl(struct ifnet *ifp, u_long cmd, caddr_t data)
340{
341	struct ifreq *ifr = (struct ifreq *)data;
342	struct tun_softc *tp = ifp->if_softc;
343	struct ifstat *ifs;
344	int		error = 0, s;
345
346	s = splimp();
347	switch(cmd) {
348	case SIOCGIFSTATUS:
349		ifs = (struct ifstat *)data;
350		if (tp->tun_proc)
351			sprintf(ifs->ascii + strlen(ifs->ascii),
352			    "\tOpened by PID %d\n", tp->tun_proc->p_pid);
353		break;
354	case SIOCSIFADDR:
355		error = tuninit(ifp);
356		TUNDEBUG(ifp, "address set, error=%d\n", error);
357		break;
358	case SIOCSIFDSTADDR:
359		error = tuninit(ifp);
360		TUNDEBUG(ifp, "destination address set, error=%d\n", error);
361		break;
362	case SIOCSIFMTU:
363		ifp->if_mtu = ifr->ifr_mtu;
364		TUNDEBUG(ifp, "mtu set\n");
365		break;
366	case SIOCSIFFLAGS:
367	case SIOCADDMULTI:
368	case SIOCDELMULTI:
369		break;
370	default:
371		error = EINVAL;
372	}
373	splx(s);
374	return (error);
375}
376
377/*
378 * tunoutput - queue packets from higher level ready to put out.
379 */
380static int
381tunoutput(
382	struct ifnet *ifp,
383	struct mbuf *m0,
384	struct sockaddr *dst,
385	struct rtentry *rt)
386{
387	struct tun_softc *tp = ifp->if_softc;
388#ifdef MAC
389	int error;
390#endif
391
392	TUNDEBUG (ifp, "tunoutput\n");
393
394#ifdef MAC
395	error = mac_check_ifnet_transmit(ifp, m0);
396	if (error) {
397		m_freem(m0);
398		return (error);
399	}
400#endif
401
402	if ((tp->tun_flags & TUN_READY) != TUN_READY) {
403		TUNDEBUG (ifp, "not ready 0%o\n", tp->tun_flags);
404		m_freem (m0);
405		return (EHOSTDOWN);
406	}
407
408	if ((ifp->if_flags & IFF_UP) != IFF_UP) {
409		m_freem (m0);
410		return (EHOSTDOWN);
411	}
412
413	/* BPF write needs to be handled specially */
414	if (dst->sa_family == AF_UNSPEC) {
415		dst->sa_family = *(mtod(m0, int *));
416		m0->m_len -= sizeof(int);
417		m0->m_pkthdr.len -= sizeof(int);
418		m0->m_data += sizeof(int);
419	}
420
421	if (ifp->if_bpf) {
422		uint32_t af = dst->sa_family;
423		bpf_mtap2(ifp->if_bpf, &af, sizeof(af), m0);
424	}
425
426	/* prepend sockaddr? this may abort if the mbuf allocation fails */
427	if (tp->tun_flags & TUN_LMODE) {
428		/* allocate space for sockaddr */
429		M_PREPEND(m0, dst->sa_len, M_DONTWAIT);
430
431		/* if allocation failed drop packet */
432		if (m0 == NULL) {
433			ifp->if_iqdrops++;
434			ifp->if_oerrors++;
435			return (ENOBUFS);
436		} else {
437			bcopy(dst, m0->m_data, dst->sa_len);
438		}
439	}
440
441	if (tp->tun_flags & TUN_IFHEAD) {
442		/* Prepend the address family */
443		M_PREPEND(m0, 4, M_DONTWAIT);
444
445		/* if allocation failed drop packet */
446		if (m0 == NULL) {
447			ifp->if_iqdrops++;
448			ifp->if_oerrors++;
449			return (ENOBUFS);
450		} else
451			*(u_int32_t *)m0->m_data = htonl(dst->sa_family);
452	} else {
453#ifdef INET
454		if (dst->sa_family != AF_INET)
455#endif
456		{
457			m_freem(m0);
458			return (EAFNOSUPPORT);
459		}
460	}
461
462	if (! IF_HANDOFF(&ifp->if_snd, m0, ifp)) {
463		ifp->if_collisions++;
464		return (ENOBUFS);
465	}
466	ifp->if_opackets++;
467	return (0);
468}
469
470/*
471 * the cdevsw interface is now pretty minimal.
472 */
473static	int
474tunioctl(dev_t dev, u_long cmd, caddr_t data, int flag, struct thread *td)
475{
476	int		s;
477	int		error;
478	struct tun_softc *tp = dev->si_drv1;
479	struct tuninfo *tunp;
480
481	switch (cmd) {
482	case TUNSIFINFO:
483		tunp = (struct tuninfo *)data;
484		if (tunp->mtu < IF_MINMTU)
485			return (EINVAL);
486		if (tp->tun_if.if_mtu != tunp->mtu
487		&& (error = suser(td)) != 0)
488			return (error);
489		tp->tun_if.if_mtu = tunp->mtu;
490		tp->tun_if.if_type = tunp->type;
491		tp->tun_if.if_baudrate = tunp->baudrate;
492		break;
493	case TUNGIFINFO:
494		tunp = (struct tuninfo *)data;
495		tunp->mtu = tp->tun_if.if_mtu;
496		tunp->type = tp->tun_if.if_type;
497		tunp->baudrate = tp->tun_if.if_baudrate;
498		break;
499	case TUNSDEBUG:
500		tundebug = *(int *)data;
501		break;
502	case TUNGDEBUG:
503		*(int *)data = tundebug;
504		break;
505	case TUNSLMODE:
506		if (*(int *)data) {
507			tp->tun_flags |= TUN_LMODE;
508			tp->tun_flags &= ~TUN_IFHEAD;
509		} else
510			tp->tun_flags &= ~TUN_LMODE;
511		break;
512	case TUNSIFHEAD:
513		if (*(int *)data) {
514			tp->tun_flags |= TUN_IFHEAD;
515			tp->tun_flags &= ~TUN_LMODE;
516		} else
517			tp->tun_flags &= ~TUN_IFHEAD;
518		break;
519	case TUNGIFHEAD:
520		*(int *)data = (tp->tun_flags & TUN_IFHEAD) ? 1 : 0;
521		break;
522	case TUNSIFMODE:
523		/* deny this if UP */
524		if (tp->tun_if.if_flags & IFF_UP)
525			return(EBUSY);
526
527		switch (*(int *)data & ~IFF_MULTICAST) {
528		case IFF_POINTOPOINT:
529		case IFF_BROADCAST:
530			tp->tun_if.if_flags &=
531			    ~(IFF_BROADCAST|IFF_POINTOPOINT|IFF_MULTICAST);
532			tp->tun_if.if_flags |= *(int *)data;
533			break;
534		default:
535			return(EINVAL);
536		}
537		break;
538	case TUNSIFPID:
539		tp->tun_proc = curthread->td_proc;
540		break;
541	case FIONBIO:
542		break;
543	case FIOASYNC:
544		if (*(int *)data)
545			tp->tun_flags |= TUN_ASYNC;
546		else
547			tp->tun_flags &= ~TUN_ASYNC;
548		break;
549	case FIONREAD:
550		s = splimp();
551		if (tp->tun_if.if_snd.ifq_head) {
552			struct mbuf *mb = tp->tun_if.if_snd.ifq_head;
553			for( *(int *)data = 0; mb != 0; mb = mb->m_next)
554				*(int *)data += mb->m_len;
555		} else
556			*(int *)data = 0;
557		splx(s);
558		break;
559	case FIOSETOWN:
560		return (fsetown(*(int *)data, &tp->tun_sigio));
561
562	case FIOGETOWN:
563		*(int *)data = fgetown(&tp->tun_sigio);
564		return (0);
565
566	/* This is deprecated, FIOSETOWN should be used instead. */
567	case TIOCSPGRP:
568		return (fsetown(-(*(int *)data), &tp->tun_sigio));
569
570	/* This is deprecated, FIOGETOWN should be used instead. */
571	case TIOCGPGRP:
572		*(int *)data = -fgetown(&tp->tun_sigio);
573		return (0);
574
575	default:
576		return (ENOTTY);
577	}
578	return (0);
579}
580
581/*
582 * The cdevsw read interface - reads a packet at a time, or at
583 * least as much of a packet as can be read.
584 */
585static	int
586tunread(dev_t dev, struct uio *uio, int flag)
587{
588	struct tun_softc *tp = dev->si_drv1;
589	struct ifnet	*ifp = &tp->tun_if;
590	struct mbuf	*m;
591	int		error=0, len, s;
592
593	TUNDEBUG (ifp, "read\n");
594	if ((tp->tun_flags & TUN_READY) != TUN_READY) {
595		TUNDEBUG (ifp, "not ready 0%o\n", tp->tun_flags);
596		return (EHOSTDOWN);
597	}
598
599	tp->tun_flags &= ~TUN_RWAIT;
600
601	s = splimp();
602	do {
603		IF_DEQUEUE(&ifp->if_snd, m);
604		if (m == NULL) {
605			if (flag & IO_NDELAY) {
606				splx(s);
607				return (EWOULDBLOCK);
608			}
609			tp->tun_flags |= TUN_RWAIT;
610			if((error = tsleep(tp, PCATCH | (PZERO + 1),
611					"tunread", 0)) != 0) {
612				splx(s);
613				return (error);
614			}
615		}
616	} while (m == NULL);
617	splx(s);
618
619	while (m && uio->uio_resid > 0 && error == 0) {
620		len = min(uio->uio_resid, m->m_len);
621		if (len != 0)
622			error = uiomove(mtod(m, void *), len, uio);
623		m = m_free(m);
624	}
625
626	if (m) {
627		TUNDEBUG(ifp, "Dropping mbuf\n");
628		m_freem(m);
629	}
630	return (error);
631}
632
633/*
634 * the cdevsw write interface - an atomic write is a packet - or else!
635 */
636static	int
637tunwrite(dev_t dev, struct uio *uio, int flag)
638{
639	struct tun_softc *tp = dev->si_drv1;
640	struct ifnet	*ifp = &tp->tun_if;
641	struct mbuf	*top, **mp, *m;
642	int		error=0, tlen, mlen;
643	uint32_t	family;
644	int 		isr;
645
646	TUNDEBUG(ifp, "tunwrite\n");
647
648	if ((ifp->if_flags & IFF_UP) != IFF_UP)
649		/* ignore silently */
650		return (0);
651
652	if (uio->uio_resid == 0)
653		return (0);
654
655	if (uio->uio_resid < 0 || uio->uio_resid > TUNMRU) {
656		TUNDEBUG(ifp, "len=%d!\n", uio->uio_resid);
657		return (EIO);
658	}
659	tlen = uio->uio_resid;
660
661	/* get a header mbuf */
662	MGETHDR(m, M_DONTWAIT, MT_DATA);
663	if (m == NULL)
664		return (ENOBUFS);
665	mlen = MHLEN;
666
667	top = 0;
668	mp = &top;
669	while (error == 0 && uio->uio_resid > 0) {
670		m->m_len = min(mlen, uio->uio_resid);
671		error = uiomove(mtod(m, void *), m->m_len, uio);
672		*mp = m;
673		mp = &m->m_next;
674		if (uio->uio_resid > 0) {
675			MGET (m, M_DONTWAIT, MT_DATA);
676			if (m == 0) {
677				error = ENOBUFS;
678				break;
679			}
680			mlen = MLEN;
681		}
682	}
683	if (error) {
684		if (top)
685			m_freem (top);
686		ifp->if_ierrors++;
687		return (error);
688	}
689
690	top->m_pkthdr.len = tlen;
691	top->m_pkthdr.rcvif = ifp;
692#ifdef MAC
693	mac_create_mbuf_from_ifnet(ifp, top);
694#endif
695
696	if (tp->tun_flags & TUN_IFHEAD) {
697		if (top->m_len < sizeof(family) &&
698		    (top = m_pullup(top, sizeof(family))) == NULL)
699			return (ENOBUFS);
700		family = ntohl(*mtod(top, u_int32_t *));
701		m_adj(top, sizeof(family));
702	} else
703		family = AF_INET;
704
705	BPF_MTAP2(ifp, &family, sizeof(family), top);
706
707	switch (family) {
708#ifdef INET
709	case AF_INET:
710		isr = NETISR_IP;
711		break;
712#endif
713#ifdef INET6
714	case AF_INET6:
715		isr = NETISR_IPV6;
716		break;
717#endif
718#ifdef IPX
719	case AF_IPX:
720		isr = NETISR_IPX;
721		break;
722#endif
723#ifdef NETATALK
724	case AF_APPLETALK:
725		isr = NETISR_ATALK2;
726		break;
727#endif
728	default:
729		m_freem(m);
730		return (EAFNOSUPPORT);
731	}
732	/* First chunk of an mbuf contains good junk */
733	if (harvest.point_to_point)
734		random_harvest(m, 16, 3, 0, RANDOM_NET);
735	ifp->if_ibytes += top->m_pkthdr.len;
736	ifp->if_ipackets++;
737	netisr_dispatch(isr, top);
738	return (0);
739}
740
741/*
742 * tunpoll - the poll interface, this is only useful on reads
743 * really. The write detect always returns true, write never blocks
744 * anyway, it either accepts the packet or drops it.
745 */
746static	int
747tunpoll(dev_t dev, int events, struct thread *td)
748{
749	int		s;
750	struct tun_softc *tp = dev->si_drv1;
751	struct ifnet	*ifp = &tp->tun_if;
752	int		revents = 0;
753
754	s = splimp();
755	TUNDEBUG(ifp, "tunpoll\n");
756
757	if (events & (POLLIN | POLLRDNORM)) {
758		if (ifp->if_snd.ifq_len > 0) {
759			TUNDEBUG(ifp, "tunpoll q=%d\n", ifp->if_snd.ifq_len);
760			revents |= events & (POLLIN | POLLRDNORM);
761		} else {
762			TUNDEBUG(ifp, "tunpoll waiting\n");
763			selrecord(td, &tp->tun_rsel);
764		}
765	}
766	if (events & (POLLOUT | POLLWRNORM))
767		revents |= events & (POLLOUT | POLLWRNORM);
768
769	splx(s);
770	return (revents);
771}
772