kernel: Fix two NULL dereference issues.
[dragonfly.git] / sys / netgraph / tty / ng_tty.c
CommitLineData
984263bc 1/*
22ff886e
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2 * (MPSAFE)
3 *
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4 * ng_tty.c
5 *
6 * Copyright (c) 1996-1999 Whistle Communications, Inc.
7 * All rights reserved.
8 *
9 * Subject to the following obligations and disclaimer of warranty, use and
10 * redistribution of this software, in source or object code forms, with or
11 * without modifications are expressly permitted by Whistle Communications;
12 * provided, however, that:
13 * 1. Any and all reproductions of the source or object code must include the
14 * copyright notice above and the following disclaimer of warranties; and
15 * 2. No rights are granted, in any manner or form, to use Whistle
16 * Communications, Inc. trademarks, including the mark "WHISTLE
17 * COMMUNICATIONS" on advertising, endorsements, or otherwise except as
18 * such appears in the above copyright notice or in the software.
19 *
20 * THIS SOFTWARE IS BEING PROVIDED BY WHISTLE COMMUNICATIONS "AS IS", AND
21 * TO THE MAXIMUM EXTENT PERMITTED BY LAW, WHISTLE COMMUNICATIONS MAKES NO
22 * REPRESENTATIONS OR WARRANTIES, EXPRESS OR IMPLIED, REGARDING THIS SOFTWARE,
23 * INCLUDING WITHOUT LIMITATION, ANY AND ALL IMPLIED WARRANTIES OF
24 * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE, OR NON-INFRINGEMENT.
25 * WHISTLE COMMUNICATIONS DOES NOT WARRANT, GUARANTEE, OR MAKE ANY
26 * REPRESENTATIONS REGARDING THE USE OF, OR THE RESULTS OF THE USE OF THIS
27 * SOFTWARE IN TERMS OF ITS CORRECTNESS, ACCURACY, RELIABILITY OR OTHERWISE.
28 * IN NO EVENT SHALL WHISTLE COMMUNICATIONS BE LIABLE FOR ANY DAMAGES
29 * RESULTING FROM OR ARISING OUT OF ANY USE OF THIS SOFTWARE, INCLUDING
30 * WITHOUT LIMITATION, ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY,
31 * PUNITIVE, OR CONSEQUENTIAL DAMAGES, PROCUREMENT OF SUBSTITUTE GOODS OR
32 * SERVICES, LOSS OF USE, DATA OR PROFITS, HOWEVER CAUSED AND UNDER ANY
33 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
34 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
35 * THIS SOFTWARE, EVEN IF WHISTLE COMMUNICATIONS IS ADVISED OF THE POSSIBILITY
36 * OF SUCH DAMAGE.
37 *
38 * Author: Archie Cobbs <archie@freebsd.org>
39 *
40 * $FreeBSD: src/sys/netgraph/ng_tty.c,v 1.7.2.3 2002/02/13 00:43:12 dillon Exp $
41 * $Whistle: ng_tty.c,v 1.21 1999/11/01 09:24:52 julian Exp $
42 */
43
44/*
45 * This file implements a terminal line discipline that is also a
46 * netgraph node. Installing this line discipline on a terminal device
47 * instantiates a new netgraph node of this type, which allows access
48 * to the device via the "hook" hook of the node.
49 *
50 * Once the line discipline is installed, you can find out the name
51 * of the corresponding netgraph node via a NGIOCGINFO ioctl().
52 *
53 * Incoming characters are delievered to the hook one at a time, each
54 * in its own mbuf. You may optionally define a ``hotchar,'' which causes
55 * incoming characters to be buffered up until either the hotchar is
56 * seen or the mbuf is full (MHLEN bytes). Then all buffered characters
57 * are immediately delivered.
58 *
59 * NOTE: This node operates at spltty().
60 */
61
62#include <sys/param.h>
63#include <sys/systm.h>
64#include <sys/kernel.h>
65#include <sys/conf.h>
66#include <sys/proc.h>
895c1f85 67#include <sys/priv.h>
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68#include <sys/mbuf.h>
69#include <sys/malloc.h>
70#include <sys/fcntl.h>
71#include <sys/tty.h>
72#include <sys/ttycom.h>
73#include <sys/syslog.h>
74#include <sys/errno.h>
41e90fed 75#include <sys/thread2.h>
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76
77#include <netgraph/ng_message.h>
78#include <netgraph/netgraph.h>
1f2de5d4 79#include "ng_tty.h"
984263bc 80
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81/* Misc defs */
82#define MAX_MBUFQ 3 /* Max number of queued mbufs */
83#define NGT_HIWATER 400 /* High water mark on output */
84
85/* Per-node private info */
86struct ngt_sc {
87 struct tty *tp; /* Terminal device */
88 node_p node; /* Netgraph node */
89 hook_p hook; /* Netgraph hook */
90 struct mbuf *m; /* Incoming data buffer */
91 struct mbuf *qhead, **qtail; /* Queue of outgoing mbuf's */
92 short qlen; /* Length of queue */
93 short hotchar; /* Hotchar, or -1 if none */
94 u_int flags; /* Flags */
5aed2989 95 struct callout ctimeout; /* See man timeout(9) */
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96};
97typedef struct ngt_sc *sc_p;
98
99/* Flags */
100#define FLG_TIMEOUT 0x0001 /* A timeout is pending */
101#define FLG_DEBUG 0x0002
102
103/* Debugging */
104#ifdef INVARIANTS
105#define QUEUECHECK(sc) \
106 do { \
107 struct mbuf **mp; \
108 int k; \
109 \
110 for (k = 0, mp = &sc->qhead; \
111 k <= MAX_MBUFQ && *mp; \
112 k++, mp = &(*mp)->m_nextpkt); \
113 if (k != sc->qlen || k > MAX_MBUFQ || *mp || mp != sc->qtail) \
5e2195bf 114 panic("%s: queue", __func__); \
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115 } while (0)
116#else
117#define QUEUECHECK(sc) do {} while (0)
118#endif
119
120/* Line discipline methods */
b13267a5 121static int ngt_open(cdev_t dev, struct tty *tp);
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122static int ngt_close(struct tty *tp, int flag);
123static int ngt_read(struct tty *tp, struct uio *uio, int flag);
124static int ngt_write(struct tty *tp, struct uio *uio, int flag);
125static int ngt_tioctl(struct tty *tp,
fef8985e 126 u_long cmd, caddr_t data, int flag, struct ucred *cred);
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127static int ngt_input(int c, struct tty *tp);
128static int ngt_start(struct tty *tp);
129
130/* Netgraph methods */
131static ng_constructor_t ngt_constructor;
132static ng_rcvmsg_t ngt_rcvmsg;
133static ng_shutdown_t ngt_shutdown;
134static ng_newhook_t ngt_newhook;
135static ng_rcvdata_t ngt_rcvdata;
136static ng_disconnect_t ngt_disconnect;
137static int ngt_mod_event(module_t mod, int event, void *data);
138
139/* Other stuff */
140static void ngt_timeout(void *arg);
141
142#define ERROUT(x) do { error = (x); goto done; } while (0)
143
144/* Line discipline descriptor */
145static struct linesw ngt_disc = {
146 ngt_open,
147 ngt_close,
148 ngt_read,
149 ngt_write,
150 ngt_tioctl,
151 ngt_input,
152 ngt_start,
153 ttymodem,
154 NG_TTY_DFL_HOTCHAR /* XXX can't change this in serial driver */
155};
156
157/* Netgraph node type descriptor */
158static struct ng_type typestruct = {
159 NG_VERSION,
160 NG_TTY_NODE_TYPE,
161 ngt_mod_event,
162 ngt_constructor,
163 ngt_rcvmsg,
164 ngt_shutdown,
165 ngt_newhook,
166 NULL,
167 NULL,
168 ngt_rcvdata,
169 ngt_rcvdata,
170 ngt_disconnect,
171 NULL
172};
173NETGRAPH_INIT(tty, &typestruct);
174
175static int ngt_unit;
176static int ngt_nodeop_ok; /* OK to create/remove node */
177static int ngt_ldisc;
178
179/******************************************************************
180 LINE DISCIPLINE METHODS
181******************************************************************/
182
183/*
184 * Set our line discipline on the tty.
185 * Called from device open routine or ttioctl() at >= splsofttty()
186 */
187static int
b13267a5 188ngt_open(cdev_t dev, struct tty *tp)
984263bc 189{
dadab5e9 190 struct thread *td = curthread; /* XXX */
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191 char name[sizeof(NG_TTY_NODE_TYPE) + 8];
192 sc_p sc;
41e90fed 193 int error;
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194
195 /* Super-user only */
895c1f85 196 if ((error = priv_check(td, PRIV_ROOT)))
984263bc 197 return (error);
41e90fed 198 crit_enter();
22ff886e 199 lwkt_gettoken(&tty_token);
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200
201 /* Already installed? */
202 if (tp->t_line == NETGRAPHDISC) {
203 sc = (sc_p) tp->t_sc;
204 if (sc != NULL && sc->tp == tp)
205 goto done;
206 }
207
208 /* Initialize private struct */
884717e1 209 sc = kmalloc(sizeof(*sc), M_NETGRAPH, M_WAITOK | M_ZERO);
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210 sc->tp = tp;
211 sc->hotchar = NG_TTY_DFL_HOTCHAR;
212 sc->qtail = &sc->qhead;
213 QUEUECHECK(sc);
22ff886e 214 callout_init_mp(&sc->ctimeout);
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215
216 /* Setup netgraph node */
217 ngt_nodeop_ok = 1;
218 error = ng_make_node_common(&typestruct, &sc->node);
219 ngt_nodeop_ok = 0;
220 if (error) {
884717e1 221 kfree(sc, M_NETGRAPH);
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222 goto done;
223 }
f8c7a42d 224 ksnprintf(name, sizeof(name), "%s%d", typestruct.name, ngt_unit++);
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225
226 /* Set back pointers */
227 sc->node->private = sc;
228 tp->t_sc = (caddr_t) sc;
229
230 /* Assign node its name */
231 if ((error = ng_name_node(sc->node, name))) {
232 log(LOG_ERR, "%s: node name exists?\n", name);
233 ngt_nodeop_ok = 1;
234 ng_rmnode(sc->node);
235 ngt_nodeop_ok = 0;
236 goto done;
237 }
238
239 /*
240 * Pre-allocate cblocks to the an appropriate amount.
241 * I'm not sure what is appropriate.
242 */
243 ttyflush(tp, FREAD | FWRITE);
244 clist_alloc_cblocks(&tp->t_canq, 0, 0);
245 clist_alloc_cblocks(&tp->t_rawq, 0, 0);
246 clist_alloc_cblocks(&tp->t_outq,
247 MLEN + NGT_HIWATER, MLEN + NGT_HIWATER);
248
249done:
250 /* Done */
22ff886e 251 lwkt_reltoken(&tty_token);
41e90fed 252 crit_exit();
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253 return (error);
254}
255
256/*
257 * Line specific close routine, called from device close routine
258 * and from ttioctl at >= splsofttty(). This causes the node to
259 * be destroyed as well.
260 */
261static int
262ngt_close(struct tty *tp, int flag)
263{
264 const sc_p sc = (sc_p) tp->t_sc;
984263bc 265
41e90fed 266 crit_enter();
22ff886e 267 lwkt_gettoken(&tty_token);
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268 ttyflush(tp, FREAD | FWRITE);
269 clist_free_cblocks(&tp->t_outq);
270 tp->t_line = 0;
271 if (sc != NULL) {
272 if (sc->flags & FLG_TIMEOUT) {
5aed2989 273 callout_stop(&sc->ctimeout);
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274 sc->flags &= ~FLG_TIMEOUT;
275 }
276 ngt_nodeop_ok = 1;
277 ng_rmnode(sc->node);
278 ngt_nodeop_ok = 0;
279 tp->t_sc = NULL;
280 }
22ff886e 281 lwkt_reltoken(&tty_token);
41e90fed 282 crit_exit();
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283 return (0);
284}
285
286/*
287 * Once the device has been turned into a node, we don't allow reading.
288 */
289static int
290ngt_read(struct tty *tp, struct uio *uio, int flag)
291{
292 return (EIO);
293}
294
295/*
296 * Once the device has been turned into a node, we don't allow writing.
297 */
298static int
299ngt_write(struct tty *tp, struct uio *uio, int flag)
300{
301 return (EIO);
302}
303
304/*
305 * We implement the NGIOCGINFO ioctl() defined in ng_message.h.
306 */
307static int
fef8985e 308ngt_tioctl(struct tty *tp, u_long cmd, caddr_t data, int flag, struct ucred *cred)
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309{
310 const sc_p sc = (sc_p) tp->t_sc;
41e90fed 311 int error = 0;
984263bc 312
41e90fed 313 crit_enter();
22ff886e 314 lwkt_gettoken(&tty_token);
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315 switch (cmd) {
316 case NGIOCGINFO:
317 {
318 struct nodeinfo *const ni = (struct nodeinfo *) data;
319 const node_p node = sc->node;
320
321 bzero(ni, sizeof(*ni));
322 if (node->name)
323 strncpy(ni->name, node->name, sizeof(ni->name) - 1);
324 strncpy(ni->type, node->type->name, sizeof(ni->type) - 1);
973c11b9 325 ni->id = (u_int32_t)(uintptr_t)node;
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326 ni->hooks = node->numhooks;
327 break;
328 }
329 default:
330 ERROUT(ENOIOCTL);
331 }
332done:
22ff886e 333 lwkt_reltoken(&tty_token);
41e90fed 334 crit_exit();
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335 return (error);
336}
337
338/*
339 * Receive data coming from the device. We get one character at
340 * a time, which is kindof silly.
341 * Only guaranteed to be at splsofttty() or spltty().
342 */
343static int
344ngt_input(int c, struct tty *tp)
345{
346 const sc_p sc = (sc_p) tp->t_sc;
2cd39ed1 347 const node_p node = sc ? sc->node : NULL;
984263bc 348 struct mbuf *m;
41e90fed 349 int error = 0;
984263bc 350
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351 lwkt_gettoken(&tty_token);
352 if (!sc || tp != sc->tp) {
353 lwkt_reltoken(&tty_token);
984263bc 354 return (0);
22ff886e 355 }
41e90fed 356 crit_enter();
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357 if (!sc->hook)
358 ERROUT(0);
359
360 /* Check for error conditions */
361 if ((tp->t_state & TS_CONNECTED) == 0) {
362 if (sc->flags & FLG_DEBUG)
363 log(LOG_DEBUG, "%s: no carrier\n", node->name);
364 ERROUT(0);
365 }
366 if (c & TTY_ERRORMASK) {
367 /* framing error or overrun on this char */
368 if (sc->flags & FLG_DEBUG)
369 log(LOG_DEBUG, "%s: line error %x\n",
370 node->name, c & TTY_ERRORMASK);
371 ERROUT(0);
372 }
373 c &= TTY_CHARMASK;
374
375 /* Get a new header mbuf if we need one */
376 if (!(m = sc->m)) {
74f1caca 377 MGETHDR(m, MB_DONTWAIT, MT_DATA);
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378 if (!m) {
379 if (sc->flags & FLG_DEBUG)
380 log(LOG_ERR,
381 "%s: can't get mbuf\n", node->name);
382 ERROUT(ENOBUFS);
383 }
384 m->m_len = m->m_pkthdr.len = 0;
385 m->m_pkthdr.rcvif = NULL;
386 sc->m = m;
387 }
388
389 /* Add char to mbuf */
390 *mtod(m, u_char *) = c;
391 m->m_data++;
392 m->m_len++;
393 m->m_pkthdr.len++;
394
395 /* Ship off mbuf if it's time */
396 if (sc->hotchar == -1 || c == sc->hotchar || m->m_len >= MHLEN) {
397 m->m_data = m->m_pktdat;
398 error = ng_queue_data(sc->hook, m, NULL);
399 sc->m = NULL;
400 }
401done:
41e90fed 402 crit_exit();
22ff886e 403 lwkt_reltoken(&tty_token);
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404 return (error);
405}
406
407/*
408 * This is called when the device driver is ready for more output.
409 * Called from tty system at splsofttty() or spltty().
410 * Also call from ngt_rcv_data() when a new mbuf is available for output.
411 */
412static int
413ngt_start(struct tty *tp)
414{
415 const sc_p sc = (sc_p) tp->t_sc;
984263bc 416
41e90fed 417 crit_enter();
22ff886e 418 lwkt_gettoken(&tty_token);
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419 while (tp->t_outq.c_cc < NGT_HIWATER) { /* XXX 2.2 specific ? */
420 struct mbuf *m = sc->qhead;
421
422 /* Remove first mbuf from queue */
423 if (!m)
424 break;
425 if ((sc->qhead = m->m_nextpkt) == NULL)
426 sc->qtail = &sc->qhead;
427 sc->qlen--;
428 QUEUECHECK(sc);
429
430 /* Send as much of it as possible */
431 while (m) {
432 int sent;
433
434 sent = m->m_len
435 - b_to_q(mtod(m, u_char *), m->m_len, &tp->t_outq);
436 m->m_data += sent;
437 m->m_len -= sent;
438 if (m->m_len > 0)
439 break; /* device can't take no more */
440 m = m_free(m);
441 }
442
443 /* Put remainder of mbuf chain (if any) back on queue */
444 if (m) {
445 m->m_nextpkt = sc->qhead;
446 sc->qhead = m;
447 if (sc->qtail == &sc->qhead)
448 sc->qtail = &m->m_nextpkt;
449 sc->qlen++;
450 QUEUECHECK(sc);
451 break;
452 }
453 }
454
455 /* Call output process whether or not there is any output. We are
456 * being called in lieu of ttstart and must do what it would. */
457 if (tp->t_oproc != NULL)
458 (*tp->t_oproc) (tp);
459
460 /* This timeout is needed for operation on a pseudo-tty, because the
461 * pty code doesn't call pppstart after it has drained the t_outq. */
462 if (sc->qhead && (sc->flags & FLG_TIMEOUT) == 0) {
5aed2989 463 callout_reset(&sc->ctimeout, 1, ngt_timeout, sc);
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464 sc->flags |= FLG_TIMEOUT;
465 }
22ff886e 466 lwkt_reltoken(&tty_token);
41e90fed 467 crit_exit();
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468 return (0);
469}
470
471/*
472 * We still have data to output to the device, so try sending more.
473 */
474static void
475ngt_timeout(void *arg)
476{
477 const sc_p sc = (sc_p) arg;
984263bc 478
41e90fed 479 crit_enter();
22ff886e 480 lwkt_gettoken(&tty_token);
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481 sc->flags &= ~FLG_TIMEOUT;
482 ngt_start(sc->tp);
22ff886e 483 lwkt_reltoken(&tty_token);
41e90fed 484 crit_exit();
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485}
486
487/******************************************************************
488 NETGRAPH NODE METHODS
489******************************************************************/
490
491/*
492 * Initialize a new node of this type.
493 *
494 * We only allow nodes to be created as a result of setting
495 * the line discipline on a tty, so always return an error if not.
496 */
497static int
498ngt_constructor(node_p *nodep)
499{
500 if (!ngt_nodeop_ok)
501 return (EOPNOTSUPP);
502 return (ng_make_node_common(&typestruct, nodep));
503}
504
505/*
506 * Add a new hook. There can only be one.
507 */
508static int
509ngt_newhook(node_p node, hook_p hook, const char *name)
510{
511 const sc_p sc = node->private;
41e90fed 512 int error = 0;
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513
514 if (strcmp(name, NG_TTY_HOOK))
515 return (EINVAL);
41e90fed 516 crit_enter();
22ff886e 517 lwkt_gettoken(&tty_token);
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518 if (sc->hook)
519 ERROUT(EISCONN);
520 sc->hook = hook;
521done:
22ff886e 522 lwkt_reltoken(&tty_token);
41e90fed 523 crit_exit();
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524 return (error);
525}
526
527/*
528 * Disconnect the hook
529 */
530static int
531ngt_disconnect(hook_p hook)
532{
533 const sc_p sc = hook->node->private;
984263bc 534
41e90fed 535 crit_enter();
22ff886e 536 lwkt_gettoken(&tty_token);
984263bc 537 if (hook != sc->hook)
5e2195bf 538 panic(__func__);
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539 sc->hook = NULL;
540 m_freem(sc->m);
541 sc->m = NULL;
22ff886e 542 lwkt_reltoken(&tty_token);
41e90fed 543 crit_exit();
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544 return (0);
545}
546
547/*
548 * Remove this node. The does the netgraph portion of the shutdown.
549 * This should only be called indirectly from ngt_close().
550 */
551static int
552ngt_shutdown(node_p node)
553{
554 const sc_p sc = node->private;
555
556 if (!ngt_nodeop_ok)
557 return (EOPNOTSUPP);
22ff886e 558 lwkt_gettoken(&tty_token);
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559 ng_unname(node);
560 ng_cutlinks(node);
561 node->private = NULL;
562 ng_unref(sc->node);
563 m_freem(sc->qhead);
564 m_freem(sc->m);
565 bzero(sc, sizeof(*sc));
884717e1 566 kfree(sc, M_NETGRAPH);
22ff886e 567 lwkt_reltoken(&tty_token);
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568 return (0);
569}
570
571/*
572 * Receive incoming data from netgraph system. Put it on our
573 * output queue and start output if necessary.
574 */
575static int
576ngt_rcvdata(hook_p hook, struct mbuf *m, meta_p meta)
577{
578 const sc_p sc = hook->node->private;
41e90fed 579 int error = 0;
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580
581 if (hook != sc->hook)
5e2195bf 582 panic(__func__);
984263bc 583 NG_FREE_META(meta);
41e90fed 584 crit_enter();
22ff886e 585 lwkt_gettoken(&tty_token);
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586 if (sc->qlen >= MAX_MBUFQ)
587 ERROUT(ENOBUFS);
588 m->m_nextpkt = NULL;
589 *sc->qtail = m;
590 sc->qtail = &m->m_nextpkt;
591 sc->qlen++;
592 QUEUECHECK(sc);
593 m = NULL;
594 if (sc->qlen == 1)
595 ngt_start(sc->tp);
596done:
22ff886e 597 lwkt_reltoken(&tty_token);
41e90fed 598 crit_exit();
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599 if (m)
600 m_freem(m);
601 return (error);
602}
603
604/*
605 * Receive control message
606 */
607static int
608ngt_rcvmsg(node_p node, struct ng_mesg *msg, const char *retaddr,
609 struct ng_mesg **rptr)
610{
611 const sc_p sc = (sc_p) node->private;
612 struct ng_mesg *resp = NULL;
613 int error = 0;
614
22ff886e 615 lwkt_gettoken(&tty_token);
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616 switch (msg->header.typecookie) {
617 case NGM_TTY_COOKIE:
618 switch (msg->header.cmd) {
619 case NGM_TTY_SET_HOTCHAR:
620 {
621 int hotchar;
622
623 if (msg->header.arglen != sizeof(int))
624 ERROUT(EINVAL);
625 hotchar = *((int *) msg->data);
626 if (hotchar != (u_char) hotchar && hotchar != -1)
627 ERROUT(EINVAL);
628 sc->hotchar = hotchar; /* race condition is OK */
629 break;
630 }
631 case NGM_TTY_GET_HOTCHAR:
632 NG_MKRESPONSE(resp, msg, sizeof(int), M_NOWAIT);
633 if (!resp)
634 ERROUT(ENOMEM);
635 /* Race condition here is OK */
636 *((int *) resp->data) = sc->hotchar;
637 break;
638 default:
639 ERROUT(EINVAL);
640 }
641 break;
642 default:
643 ERROUT(EINVAL);
644 }
645 if (rptr)
646 *rptr = resp;
647 else if (resp)
884717e1 648 kfree(resp, M_NETGRAPH);
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649
650done:
884717e1 651 kfree(msg, M_NETGRAPH);
22ff886e 652 lwkt_reltoken(&tty_token);
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653 return (error);
654}
655
656/******************************************************************
657 INITIALIZATION
658******************************************************************/
659
660/*
661 * Handle loading and unloading for this node type
662 */
663static int
664ngt_mod_event(module_t mod, int event, void *data)
665{
666 /* struct ng_type *const type = data;*/
41e90fed 667 int error = 0;
984263bc 668
22ff886e 669 lwkt_gettoken(&tty_token);
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670 switch (event) {
671 case MOD_LOAD:
984263bc 672 /* Register line discipline */
41e90fed 673 crit_enter();
984263bc 674 if ((ngt_ldisc = ldisc_register(NETGRAPHDISC, &ngt_disc)) < 0) {
41e90fed 675 crit_exit();
984263bc 676 log(LOG_ERR, "%s: can't register line discipline",
5e2195bf 677 __func__);
984263bc
MD
678 return (EIO);
679 }
41e90fed 680 crit_exit();
984263bc
MD
681 break;
682
683 case MOD_UNLOAD:
684
685 /* Unregister line discipline */
41e90fed 686 crit_enter();
984263bc 687 ldisc_deregister(ngt_ldisc);
41e90fed 688 crit_exit();
984263bc
MD
689 break;
690
691 default:
692 error = EOPNOTSUPP;
693 break;
694 }
22ff886e 695 lwkt_reltoken(&tty_token);
984263bc
MD
696 return (error);
697}