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v4.6
 
  1/* net/atm/pppoatm.c - RFC2364 PPP over ATM/AAL5 */
  2
  3/* Copyright 1999-2000 by Mitchell Blank Jr */
  4/* Based on clip.c; 1995-1999 by Werner Almesberger, EPFL LRC/ICA */
  5/* And on ppp_async.c; Copyright 1999 Paul Mackerras */
  6/* And help from Jens Axboe */
  7
  8/*
  9 *  This program is free software; you can redistribute it and/or
 10 *  modify it under the terms of the GNU General Public License
 11 *  as published by the Free Software Foundation; either version
 12 *  2 of the License, or (at your option) any later version.
 13 *
 14 * This driver provides the encapsulation and framing for sending
 15 * and receiving PPP frames in ATM AAL5 PDUs.
 16 */
 17
 18/*
 19 * One shortcoming of this driver is that it does not comply with
 20 * section 8 of RFC2364 - we are supposed to detect a change
 21 * in encapsulation and immediately abort the connection (in order
 22 * to avoid a black-hole being created if our peer loses state
 23 * and changes encapsulation unilaterally.  However, since the
 24 * ppp_generic layer actually does the decapsulation, we need
 25 * a way of notifying it when we _think_ there might be a problem)
 26 * There's two cases:
 27 *   1.	LLC-encapsulation was missing when it was enabled.  In
 28 *	this case, we should tell the upper layer "tear down
 29 *	this session if this skb looks ok to you"
 30 *   2.	LLC-encapsulation was present when it was disabled.  Then
 31 *	we need to tell the upper layer "this packet may be
 32 *	ok, but if its in error tear down the session"
 33 * These hooks are not yet available in ppp_generic
 34 */
 35
 36#define pr_fmt(fmt) KBUILD_MODNAME ":%s: " fmt, __func__
 37
 38#include <linux/module.h>
 39#include <linux/init.h>
 40#include <linux/interrupt.h>
 41#include <linux/skbuff.h>
 42#include <linux/slab.h>
 43#include <linux/atm.h>
 44#include <linux/atmdev.h>
 45#include <linux/capability.h>
 46#include <linux/ppp_defs.h>
 47#include <linux/ppp-ioctl.h>
 48#include <linux/ppp_channel.h>
 49#include <linux/atmppp.h>
 50
 51#include "common.h"
 52
 53enum pppoatm_encaps {
 54	e_autodetect = PPPOATM_ENCAPS_AUTODETECT,
 55	e_vc = PPPOATM_ENCAPS_VC,
 56	e_llc = PPPOATM_ENCAPS_LLC,
 57};
 58
 59struct pppoatm_vcc {
 60	struct atm_vcc	*atmvcc;	/* VCC descriptor */
 61	void (*old_push)(struct atm_vcc *, struct sk_buff *);
 62	void (*old_pop)(struct atm_vcc *, struct sk_buff *);
 63	void (*old_release_cb)(struct atm_vcc *);
 64	struct module *old_owner;
 65					/* keep old push/pop for detaching */
 66	enum pppoatm_encaps encaps;
 67	atomic_t inflight;
 68	unsigned long blocked;
 69	int flags;			/* SC_COMP_PROT - compress protocol */
 70	struct ppp_channel chan;	/* interface to generic ppp layer */
 71	struct tasklet_struct wakeup_tasklet;
 72};
 73
 74/*
 75 * We want to allow two packets in the queue. The one that's currently in
 76 * flight, and *one* queued up ready for the ATM device to send immediately
 77 * from its TX done IRQ. We want to be able to use atomic_inc_not_zero(), so
 78 * inflight == -2 represents an empty queue, -1 one packet, and zero means
 79 * there are two packets in the queue.
 80 */
 81#define NONE_INFLIGHT -2
 82
 83#define BLOCKED 0
 84
 85/*
 86 * Header used for LLC Encapsulated PPP (4 bytes) followed by the LCP protocol
 87 * ID (0xC021) used in autodetection
 88 */
 89static const unsigned char pppllc[6] = { 0xFE, 0xFE, 0x03, 0xCF, 0xC0, 0x21 };
 90#define LLC_LEN		(4)
 91
 92static inline struct pppoatm_vcc *atmvcc_to_pvcc(const struct atm_vcc *atmvcc)
 93{
 94	return (struct pppoatm_vcc *) (atmvcc->user_back);
 95}
 96
 97static inline struct pppoatm_vcc *chan_to_pvcc(const struct ppp_channel *chan)
 98{
 99	return (struct pppoatm_vcc *) (chan->private);
100}
101
102/*
103 * We can't do this directly from our _pop handler, since the ppp code
104 * doesn't want to be called in interrupt context, so we do it from
105 * a tasklet
106 */
107static void pppoatm_wakeup_sender(unsigned long arg)
108{
109	ppp_output_wakeup((struct ppp_channel *) arg);
 
 
110}
111
112static void pppoatm_release_cb(struct atm_vcc *atmvcc)
113{
114	struct pppoatm_vcc *pvcc = atmvcc_to_pvcc(atmvcc);
115
116	/*
117	 * As in pppoatm_pop(), it's safe to clear the BLOCKED bit here because
118	 * the wakeup *can't* race with pppoatm_send(). They both hold the PPP
119	 * channel's ->downl lock. And the potential race with *setting* it,
120	 * which leads to the double-check dance in pppoatm_may_send(), doesn't
121	 * exist here. In the sock_owned_by_user() case in pppoatm_send(), we
122	 * set the BLOCKED bit while the socket is still locked. We know that
123	 * ->release_cb() can't be called until that's done.
124	 */
125	if (test_and_clear_bit(BLOCKED, &pvcc->blocked))
126		tasklet_schedule(&pvcc->wakeup_tasklet);
127	if (pvcc->old_release_cb)
128		pvcc->old_release_cb(atmvcc);
129}
130/*
131 * This gets called every time the ATM card has finished sending our
132 * skb.  The ->old_pop will take care up normal atm flow control,
133 * but we also need to wake up the device if we blocked it
134 */
135static void pppoatm_pop(struct atm_vcc *atmvcc, struct sk_buff *skb)
136{
137	struct pppoatm_vcc *pvcc = atmvcc_to_pvcc(atmvcc);
138
139	pvcc->old_pop(atmvcc, skb);
140	atomic_dec(&pvcc->inflight);
141
142	/*
143	 * We always used to run the wakeup tasklet unconditionally here, for
144	 * fear of race conditions where we clear the BLOCKED flag just as we
145	 * refuse another packet in pppoatm_send(). This was quite inefficient.
146	 *
147	 * In fact it's OK. The PPP core will only ever call pppoatm_send()
148	 * while holding the channel->downl lock. And ppp_output_wakeup() as
149	 * called by the tasklet will *also* grab that lock. So even if another
150	 * CPU is in pppoatm_send() right now, the tasklet isn't going to race
151	 * with it. The wakeup *will* happen after the other CPU is safely out
152	 * of pppoatm_send() again.
153	 *
154	 * So if the CPU in pppoatm_send() has already set the BLOCKED bit and
155	 * it about to return, that's fine. We trigger a wakeup which will
156	 * happen later. And if the CPU in pppoatm_send() *hasn't* set the
157	 * BLOCKED bit yet, that's fine too because of the double check in
158	 * pppoatm_may_send() which is commented there.
159	 */
160	if (test_and_clear_bit(BLOCKED, &pvcc->blocked))
161		tasklet_schedule(&pvcc->wakeup_tasklet);
162}
163
164/*
165 * Unbind from PPP - currently we only do this when closing the socket,
166 * but we could put this into an ioctl if need be
167 */
168static void pppoatm_unassign_vcc(struct atm_vcc *atmvcc)
169{
170	struct pppoatm_vcc *pvcc;
171	pvcc = atmvcc_to_pvcc(atmvcc);
172	atmvcc->push = pvcc->old_push;
173	atmvcc->pop = pvcc->old_pop;
174	atmvcc->release_cb = pvcc->old_release_cb;
175	tasklet_kill(&pvcc->wakeup_tasklet);
176	ppp_unregister_channel(&pvcc->chan);
177	atmvcc->user_back = NULL;
178	kfree(pvcc);
179}
180
181/* Called when an AAL5 PDU comes in */
182static void pppoatm_push(struct atm_vcc *atmvcc, struct sk_buff *skb)
183{
184	struct pppoatm_vcc *pvcc = atmvcc_to_pvcc(atmvcc);
185	pr_debug("\n");
186	if (skb == NULL) {			/* VCC was closed */
187		struct module *module;
188
189		pr_debug("removing ATMPPP VCC %p\n", pvcc);
190		module = pvcc->old_owner;
191		pppoatm_unassign_vcc(atmvcc);
192		atmvcc->push(atmvcc, NULL);	/* Pass along bad news */
193		module_put(module);
194		return;
195	}
196	atm_return(atmvcc, skb->truesize);
197	switch (pvcc->encaps) {
198	case e_llc:
199		if (skb->len < LLC_LEN ||
200		    memcmp(skb->data, pppllc, LLC_LEN))
201			goto error;
202		skb_pull(skb, LLC_LEN);
203		break;
204	case e_autodetect:
205		if (pvcc->chan.ppp == NULL) {	/* Not bound yet! */
206			kfree_skb(skb);
207			return;
208		}
209		if (skb->len >= sizeof(pppllc) &&
210		    !memcmp(skb->data, pppllc, sizeof(pppllc))) {
211			pvcc->encaps = e_llc;
212			skb_pull(skb, LLC_LEN);
213			break;
214		}
215		if (skb->len >= (sizeof(pppllc) - LLC_LEN) &&
216		    !memcmp(skb->data, &pppllc[LLC_LEN],
217		    sizeof(pppllc) - LLC_LEN)) {
218			pvcc->encaps = e_vc;
219			pvcc->chan.mtu += LLC_LEN;
220			break;
221		}
222		pr_debug("Couldn't autodetect yet (skb: %02X %02X %02X %02X %02X %02X)\n",
223			 skb->data[0], skb->data[1], skb->data[2],
224			 skb->data[3], skb->data[4], skb->data[5]);
225		goto error;
226	case e_vc:
227		break;
228	}
229	ppp_input(&pvcc->chan, skb);
230	return;
231
232error:
233	kfree_skb(skb);
234	ppp_input_error(&pvcc->chan, 0);
235}
236
237static int pppoatm_may_send(struct pppoatm_vcc *pvcc, int size)
238{
239	/*
240	 * It's not clear that we need to bother with using atm_may_send()
241	 * to check we don't exceed sk->sk_sndbuf. If userspace sets a
242	 * value of sk_sndbuf which is lower than the MTU, we're going to
243	 * block for ever. But the code always did that before we introduced
244	 * the packet count limit, so...
245	 */
246	if (atm_may_send(pvcc->atmvcc, size) &&
247	    atomic_inc_not_zero_hint(&pvcc->inflight, NONE_INFLIGHT))
248		return 1;
249
250	/*
251	 * We use test_and_set_bit() rather than set_bit() here because
252	 * we need to ensure there's a memory barrier after it. The bit
253	 * *must* be set before we do the atomic_inc() on pvcc->inflight.
254	 * There's no smp_mb__after_set_bit(), so it's this or abuse
255	 * smp_mb__after_atomic().
256	 */
257	test_and_set_bit(BLOCKED, &pvcc->blocked);
258
259	/*
260	 * We may have raced with pppoatm_pop(). If it ran for the
261	 * last packet in the queue, *just* before we set the BLOCKED
262	 * bit, then it might never run again and the channel could
263	 * remain permanently blocked. Cope with that race by checking
264	 * *again*. If it did run in that window, we'll have space on
265	 * the queue now and can return success. It's harmless to leave
266	 * the BLOCKED flag set, since it's only used as a trigger to
267	 * run the wakeup tasklet. Another wakeup will never hurt.
268	 * If pppoatm_pop() is running but hasn't got as far as making
269	 * space on the queue yet, then it hasn't checked the BLOCKED
270	 * flag yet either, so we're safe in that case too. It'll issue
271	 * an "immediate" wakeup... where "immediate" actually involves
272	 * taking the PPP channel's ->downl lock, which is held by the
273	 * code path that calls pppoatm_send(), and is thus going to
274	 * wait for us to finish.
275	 */
276	if (atm_may_send(pvcc->atmvcc, size) &&
277	    atomic_inc_not_zero(&pvcc->inflight))
278		return 1;
279
280	return 0;
281}
282/*
283 * Called by the ppp_generic.c to send a packet - returns true if packet
284 * was accepted.  If we return false, then it's our job to call
285 * ppp_output_wakeup(chan) when we're feeling more up to it.
286 * Note that in the ENOMEM case (as opposed to the !atm_may_send case)
287 * we should really drop the packet, but the generic layer doesn't
288 * support this yet.  We just return 'DROP_PACKET' which we actually define
289 * as success, just to be clear what we're really doing.
290 */
291#define DROP_PACKET 1
292static int pppoatm_send(struct ppp_channel *chan, struct sk_buff *skb)
293{
294	struct pppoatm_vcc *pvcc = chan_to_pvcc(chan);
295	struct atm_vcc *vcc;
296	int ret;
297
298	ATM_SKB(skb)->vcc = pvcc->atmvcc;
299	pr_debug("(skb=0x%p, vcc=0x%p)\n", skb, pvcc->atmvcc);
300	if (skb->data[0] == '\0' && (pvcc->flags & SC_COMP_PROT))
301		(void) skb_pull(skb, 1);
302
303	vcc = ATM_SKB(skb)->vcc;
304	bh_lock_sock(sk_atm(vcc));
305	if (sock_owned_by_user(sk_atm(vcc))) {
306		/*
307		 * Needs to happen (and be flushed, hence test_and_) before we unlock
308		 * the socket. It needs to be seen by the time our ->release_cb gets
309		 * called.
310		 */
311		test_and_set_bit(BLOCKED, &pvcc->blocked);
312		goto nospace;
313	}
314	if (test_bit(ATM_VF_RELEASED, &vcc->flags) ||
315	    test_bit(ATM_VF_CLOSE, &vcc->flags) ||
316	    !test_bit(ATM_VF_READY, &vcc->flags)) {
317		bh_unlock_sock(sk_atm(vcc));
318		kfree_skb(skb);
319		return DROP_PACKET;
320	}
321
322	switch (pvcc->encaps) {		/* LLC encapsulation needed */
323	case e_llc:
324		if (skb_headroom(skb) < LLC_LEN) {
325			struct sk_buff *n;
326			n = skb_realloc_headroom(skb, LLC_LEN);
327			if (n != NULL &&
328			    !pppoatm_may_send(pvcc, n->truesize)) {
329				kfree_skb(n);
330				goto nospace;
331			}
332			consume_skb(skb);
333			skb = n;
334			if (skb == NULL) {
335				bh_unlock_sock(sk_atm(vcc));
336				return DROP_PACKET;
337			}
338		} else if (!pppoatm_may_send(pvcc, skb->truesize))
339			goto nospace;
340		memcpy(skb_push(skb, LLC_LEN), pppllc, LLC_LEN);
341		break;
342	case e_vc:
343		if (!pppoatm_may_send(pvcc, skb->truesize))
344			goto nospace;
345		break;
346	case e_autodetect:
347		bh_unlock_sock(sk_atm(vcc));
348		pr_debug("Trying to send without setting encaps!\n");
349		kfree_skb(skb);
350		return 1;
351	}
352
353	atomic_add(skb->truesize, &sk_atm(ATM_SKB(skb)->vcc)->sk_wmem_alloc);
354	ATM_SKB(skb)->atm_options = ATM_SKB(skb)->vcc->atm_options;
355	pr_debug("atm_skb(%p)->vcc(%p)->dev(%p)\n",
356		 skb, ATM_SKB(skb)->vcc, ATM_SKB(skb)->vcc->dev);
357	ret = ATM_SKB(skb)->vcc->send(ATM_SKB(skb)->vcc, skb)
358	    ? DROP_PACKET : 1;
359	bh_unlock_sock(sk_atm(vcc));
360	return ret;
361nospace:
362	bh_unlock_sock(sk_atm(vcc));
363	/*
364	 * We don't have space to send this SKB now, but we might have
365	 * already applied SC_COMP_PROT compression, so may need to undo
366	 */
367	if ((pvcc->flags & SC_COMP_PROT) && skb_headroom(skb) > 0 &&
368	    skb->data[-1] == '\0')
369		(void) skb_push(skb, 1);
370	return 0;
371}
372
373/* This handles ioctls sent to the /dev/ppp interface */
374static int pppoatm_devppp_ioctl(struct ppp_channel *chan, unsigned int cmd,
375	unsigned long arg)
376{
377	switch (cmd) {
378	case PPPIOCGFLAGS:
379		return put_user(chan_to_pvcc(chan)->flags, (int __user *) arg)
380		    ? -EFAULT : 0;
381	case PPPIOCSFLAGS:
382		return get_user(chan_to_pvcc(chan)->flags, (int __user *) arg)
383		    ? -EFAULT : 0;
384	}
385	return -ENOTTY;
386}
387
388static const struct ppp_channel_ops pppoatm_ops = {
389	.start_xmit = pppoatm_send,
390	.ioctl = pppoatm_devppp_ioctl,
391};
392
393static int pppoatm_assign_vcc(struct atm_vcc *atmvcc, void __user *arg)
394{
395	struct atm_backend_ppp be;
396	struct pppoatm_vcc *pvcc;
397	int err;
398	/*
399	 * Each PPPoATM instance has its own tasklet - this is just a
400	 * prototypical one used to initialize them
401	 */
402	static const DECLARE_TASKLET(tasklet_proto, pppoatm_wakeup_sender, 0);
403	if (copy_from_user(&be, arg, sizeof be))
404		return -EFAULT;
405	if (be.encaps != PPPOATM_ENCAPS_AUTODETECT &&
406	    be.encaps != PPPOATM_ENCAPS_VC && be.encaps != PPPOATM_ENCAPS_LLC)
407		return -EINVAL;
408	pvcc = kzalloc(sizeof(*pvcc), GFP_KERNEL);
409	if (pvcc == NULL)
410		return -ENOMEM;
411	pvcc->atmvcc = atmvcc;
412
413	/* Maximum is zero, so that we can use atomic_inc_not_zero() */
414	atomic_set(&pvcc->inflight, NONE_INFLIGHT);
415	pvcc->old_push = atmvcc->push;
416	pvcc->old_pop = atmvcc->pop;
417	pvcc->old_owner = atmvcc->owner;
418	pvcc->old_release_cb = atmvcc->release_cb;
419	pvcc->encaps = (enum pppoatm_encaps) be.encaps;
420	pvcc->chan.private = pvcc;
421	pvcc->chan.ops = &pppoatm_ops;
422	pvcc->chan.mtu = atmvcc->qos.txtp.max_sdu - PPP_HDRLEN -
423	    (be.encaps == e_vc ? 0 : LLC_LEN);
424	pvcc->wakeup_tasklet = tasklet_proto;
425	pvcc->wakeup_tasklet.data = (unsigned long) &pvcc->chan;
426	err = ppp_register_channel(&pvcc->chan);
427	if (err != 0) {
428		kfree(pvcc);
429		return err;
430	}
431	atmvcc->user_back = pvcc;
432	atmvcc->push = pppoatm_push;
433	atmvcc->pop = pppoatm_pop;
434	atmvcc->release_cb = pppoatm_release_cb;
435	__module_get(THIS_MODULE);
436	atmvcc->owner = THIS_MODULE;
437
438	/* re-process everything received between connection setup and
439	   backend setup */
440	vcc_process_recv_queue(atmvcc);
441	return 0;
442}
443
444/*
445 * This handles ioctls actually performed on our vcc - we must return
446 * -ENOIOCTLCMD for any unrecognized ioctl
447 */
448static int pppoatm_ioctl(struct socket *sock, unsigned int cmd,
449	unsigned long arg)
450{
451	struct atm_vcc *atmvcc = ATM_SD(sock);
452	void __user *argp = (void __user *)arg;
453
454	if (cmd != ATM_SETBACKEND && atmvcc->push != pppoatm_push)
455		return -ENOIOCTLCMD;
456	switch (cmd) {
457	case ATM_SETBACKEND: {
458		atm_backend_t b;
459		if (get_user(b, (atm_backend_t __user *) argp))
460			return -EFAULT;
461		if (b != ATM_BACKEND_PPP)
462			return -ENOIOCTLCMD;
463		if (!capable(CAP_NET_ADMIN))
464			return -EPERM;
465		if (sock->state != SS_CONNECTED)
466			return -EINVAL;
467		return pppoatm_assign_vcc(atmvcc, argp);
468		}
469	case PPPIOCGCHAN:
470		return put_user(ppp_channel_index(&atmvcc_to_pvcc(atmvcc)->
471		    chan), (int __user *) argp) ? -EFAULT : 0;
472	case PPPIOCGUNIT:
473		return put_user(ppp_unit_number(&atmvcc_to_pvcc(atmvcc)->
474		    chan), (int __user *) argp) ? -EFAULT : 0;
475	}
476	return -ENOIOCTLCMD;
477}
478
479static struct atm_ioctl pppoatm_ioctl_ops = {
480	.owner	= THIS_MODULE,
481	.ioctl	= pppoatm_ioctl,
482};
483
484static int __init pppoatm_init(void)
485{
486	register_atm_ioctl(&pppoatm_ioctl_ops);
487	return 0;
488}
489
490static void __exit pppoatm_exit(void)
491{
492	deregister_atm_ioctl(&pppoatm_ioctl_ops);
493}
494
495module_init(pppoatm_init);
496module_exit(pppoatm_exit);
497
498MODULE_AUTHOR("Mitchell Blank Jr <mitch@sfgoth.com>");
499MODULE_DESCRIPTION("RFC2364 PPP over ATM/AAL5");
500MODULE_LICENSE("GPL");
v6.13.7
  1// SPDX-License-Identifier: GPL-2.0-or-later
  2/* net/atm/pppoatm.c - RFC2364 PPP over ATM/AAL5 */
  3
  4/* Copyright 1999-2000 by Mitchell Blank Jr */
  5/* Based on clip.c; 1995-1999 by Werner Almesberger, EPFL LRC/ICA */
  6/* And on ppp_async.c; Copyright 1999 Paul Mackerras */
  7/* And help from Jens Axboe */
  8
  9/*
 
 
 
 
 10 *
 11 * This driver provides the encapsulation and framing for sending
 12 * and receiving PPP frames in ATM AAL5 PDUs.
 13 */
 14
 15/*
 16 * One shortcoming of this driver is that it does not comply with
 17 * section 8 of RFC2364 - we are supposed to detect a change
 18 * in encapsulation and immediately abort the connection (in order
 19 * to avoid a black-hole being created if our peer loses state
 20 * and changes encapsulation unilaterally.  However, since the
 21 * ppp_generic layer actually does the decapsulation, we need
 22 * a way of notifying it when we _think_ there might be a problem)
 23 * There's two cases:
 24 *   1.	LLC-encapsulation was missing when it was enabled.  In
 25 *	this case, we should tell the upper layer "tear down
 26 *	this session if this skb looks ok to you"
 27 *   2.	LLC-encapsulation was present when it was disabled.  Then
 28 *	we need to tell the upper layer "this packet may be
 29 *	ok, but if its in error tear down the session"
 30 * These hooks are not yet available in ppp_generic
 31 */
 32
 33#define pr_fmt(fmt) KBUILD_MODNAME ":%s: " fmt, __func__
 34
 35#include <linux/module.h>
 36#include <linux/init.h>
 37#include <linux/interrupt.h>
 38#include <linux/skbuff.h>
 39#include <linux/slab.h>
 40#include <linux/atm.h>
 41#include <linux/atmdev.h>
 42#include <linux/capability.h>
 43#include <linux/ppp_defs.h>
 44#include <linux/ppp-ioctl.h>
 45#include <linux/ppp_channel.h>
 46#include <linux/atmppp.h>
 47
 48#include "common.h"
 49
 50enum pppoatm_encaps {
 51	e_autodetect = PPPOATM_ENCAPS_AUTODETECT,
 52	e_vc = PPPOATM_ENCAPS_VC,
 53	e_llc = PPPOATM_ENCAPS_LLC,
 54};
 55
 56struct pppoatm_vcc {
 57	struct atm_vcc	*atmvcc;	/* VCC descriptor */
 58	void (*old_push)(struct atm_vcc *, struct sk_buff *);
 59	void (*old_pop)(struct atm_vcc *, struct sk_buff *);
 60	void (*old_release_cb)(struct atm_vcc *);
 61	struct module *old_owner;
 62					/* keep old push/pop for detaching */
 63	enum pppoatm_encaps encaps;
 64	atomic_t inflight;
 65	unsigned long blocked;
 66	int flags;			/* SC_COMP_PROT - compress protocol */
 67	struct ppp_channel chan;	/* interface to generic ppp layer */
 68	struct tasklet_struct wakeup_tasklet;
 69};
 70
 71/*
 72 * We want to allow two packets in the queue. The one that's currently in
 73 * flight, and *one* queued up ready for the ATM device to send immediately
 74 * from its TX done IRQ. We want to be able to use atomic_inc_not_zero(), so
 75 * inflight == -2 represents an empty queue, -1 one packet, and zero means
 76 * there are two packets in the queue.
 77 */
 78#define NONE_INFLIGHT -2
 79
 80#define BLOCKED 0
 81
 82/*
 83 * Header used for LLC Encapsulated PPP (4 bytes) followed by the LCP protocol
 84 * ID (0xC021) used in autodetection
 85 */
 86static const unsigned char pppllc[6] = { 0xFE, 0xFE, 0x03, 0xCF, 0xC0, 0x21 };
 87#define LLC_LEN		(4)
 88
 89static inline struct pppoatm_vcc *atmvcc_to_pvcc(const struct atm_vcc *atmvcc)
 90{
 91	return (struct pppoatm_vcc *) (atmvcc->user_back);
 92}
 93
 94static inline struct pppoatm_vcc *chan_to_pvcc(const struct ppp_channel *chan)
 95{
 96	return (struct pppoatm_vcc *) (chan->private);
 97}
 98
 99/*
100 * We can't do this directly from our _pop handler, since the ppp code
101 * doesn't want to be called in interrupt context, so we do it from
102 * a tasklet
103 */
104static void pppoatm_wakeup_sender(struct tasklet_struct *t)
105{
106	struct pppoatm_vcc *pvcc = from_tasklet(pvcc, t, wakeup_tasklet);
107
108	ppp_output_wakeup(&pvcc->chan);
109}
110
111static void pppoatm_release_cb(struct atm_vcc *atmvcc)
112{
113	struct pppoatm_vcc *pvcc = atmvcc_to_pvcc(atmvcc);
114
115	/*
116	 * As in pppoatm_pop(), it's safe to clear the BLOCKED bit here because
117	 * the wakeup *can't* race with pppoatm_send(). They both hold the PPP
118	 * channel's ->downl lock. And the potential race with *setting* it,
119	 * which leads to the double-check dance in pppoatm_may_send(), doesn't
120	 * exist here. In the sock_owned_by_user() case in pppoatm_send(), we
121	 * set the BLOCKED bit while the socket is still locked. We know that
122	 * ->release_cb() can't be called until that's done.
123	 */
124	if (test_and_clear_bit(BLOCKED, &pvcc->blocked))
125		tasklet_schedule(&pvcc->wakeup_tasklet);
126	if (pvcc->old_release_cb)
127		pvcc->old_release_cb(atmvcc);
128}
129/*
130 * This gets called every time the ATM card has finished sending our
131 * skb.  The ->old_pop will take care up normal atm flow control,
132 * but we also need to wake up the device if we blocked it
133 */
134static void pppoatm_pop(struct atm_vcc *atmvcc, struct sk_buff *skb)
135{
136	struct pppoatm_vcc *pvcc = atmvcc_to_pvcc(atmvcc);
137
138	pvcc->old_pop(atmvcc, skb);
139	atomic_dec(&pvcc->inflight);
140
141	/*
142	 * We always used to run the wakeup tasklet unconditionally here, for
143	 * fear of race conditions where we clear the BLOCKED flag just as we
144	 * refuse another packet in pppoatm_send(). This was quite inefficient.
145	 *
146	 * In fact it's OK. The PPP core will only ever call pppoatm_send()
147	 * while holding the channel->downl lock. And ppp_output_wakeup() as
148	 * called by the tasklet will *also* grab that lock. So even if another
149	 * CPU is in pppoatm_send() right now, the tasklet isn't going to race
150	 * with it. The wakeup *will* happen after the other CPU is safely out
151	 * of pppoatm_send() again.
152	 *
153	 * So if the CPU in pppoatm_send() has already set the BLOCKED bit and
154	 * it about to return, that's fine. We trigger a wakeup which will
155	 * happen later. And if the CPU in pppoatm_send() *hasn't* set the
156	 * BLOCKED bit yet, that's fine too because of the double check in
157	 * pppoatm_may_send() which is commented there.
158	 */
159	if (test_and_clear_bit(BLOCKED, &pvcc->blocked))
160		tasklet_schedule(&pvcc->wakeup_tasklet);
161}
162
163/*
164 * Unbind from PPP - currently we only do this when closing the socket,
165 * but we could put this into an ioctl if need be
166 */
167static void pppoatm_unassign_vcc(struct atm_vcc *atmvcc)
168{
169	struct pppoatm_vcc *pvcc;
170	pvcc = atmvcc_to_pvcc(atmvcc);
171	atmvcc->push = pvcc->old_push;
172	atmvcc->pop = pvcc->old_pop;
173	atmvcc->release_cb = pvcc->old_release_cb;
174	tasklet_kill(&pvcc->wakeup_tasklet);
175	ppp_unregister_channel(&pvcc->chan);
176	atmvcc->user_back = NULL;
177	kfree(pvcc);
178}
179
180/* Called when an AAL5 PDU comes in */
181static void pppoatm_push(struct atm_vcc *atmvcc, struct sk_buff *skb)
182{
183	struct pppoatm_vcc *pvcc = atmvcc_to_pvcc(atmvcc);
184	pr_debug("\n");
185	if (skb == NULL) {			/* VCC was closed */
186		struct module *module;
187
188		pr_debug("removing ATMPPP VCC %p\n", pvcc);
189		module = pvcc->old_owner;
190		pppoatm_unassign_vcc(atmvcc);
191		atmvcc->push(atmvcc, NULL);	/* Pass along bad news */
192		module_put(module);
193		return;
194	}
195	atm_return(atmvcc, skb->truesize);
196	switch (pvcc->encaps) {
197	case e_llc:
198		if (skb->len < LLC_LEN ||
199		    memcmp(skb->data, pppllc, LLC_LEN))
200			goto error;
201		skb_pull(skb, LLC_LEN);
202		break;
203	case e_autodetect:
204		if (pvcc->chan.ppp == NULL) {	/* Not bound yet! */
205			kfree_skb(skb);
206			return;
207		}
208		if (skb->len >= sizeof(pppllc) &&
209		    !memcmp(skb->data, pppllc, sizeof(pppllc))) {
210			pvcc->encaps = e_llc;
211			skb_pull(skb, LLC_LEN);
212			break;
213		}
214		if (skb->len >= (sizeof(pppllc) - LLC_LEN) &&
215		    !memcmp(skb->data, &pppllc[LLC_LEN],
216		    sizeof(pppllc) - LLC_LEN)) {
217			pvcc->encaps = e_vc;
218			pvcc->chan.mtu += LLC_LEN;
219			break;
220		}
221		pr_debug("Couldn't autodetect yet (skb: %6ph)\n", skb->data);
 
 
222		goto error;
223	case e_vc:
224		break;
225	}
226	ppp_input(&pvcc->chan, skb);
227	return;
228
229error:
230	kfree_skb(skb);
231	ppp_input_error(&pvcc->chan, 0);
232}
233
234static int pppoatm_may_send(struct pppoatm_vcc *pvcc, int size)
235{
236	/*
237	 * It's not clear that we need to bother with using atm_may_send()
238	 * to check we don't exceed sk->sk_sndbuf. If userspace sets a
239	 * value of sk_sndbuf which is lower than the MTU, we're going to
240	 * block for ever. But the code always did that before we introduced
241	 * the packet count limit, so...
242	 */
243	if (atm_may_send(pvcc->atmvcc, size) &&
244	    atomic_inc_not_zero(&pvcc->inflight))
245		return 1;
246
247	/*
248	 * We use test_and_set_bit() rather than set_bit() here because
249	 * we need to ensure there's a memory barrier after it. The bit
250	 * *must* be set before we do the atomic_inc() on pvcc->inflight.
251	 * There's no smp_mb__after_set_bit(), so it's this or abuse
252	 * smp_mb__after_atomic().
253	 */
254	test_and_set_bit(BLOCKED, &pvcc->blocked);
255
256	/*
257	 * We may have raced with pppoatm_pop(). If it ran for the
258	 * last packet in the queue, *just* before we set the BLOCKED
259	 * bit, then it might never run again and the channel could
260	 * remain permanently blocked. Cope with that race by checking
261	 * *again*. If it did run in that window, we'll have space on
262	 * the queue now and can return success. It's harmless to leave
263	 * the BLOCKED flag set, since it's only used as a trigger to
264	 * run the wakeup tasklet. Another wakeup will never hurt.
265	 * If pppoatm_pop() is running but hasn't got as far as making
266	 * space on the queue yet, then it hasn't checked the BLOCKED
267	 * flag yet either, so we're safe in that case too. It'll issue
268	 * an "immediate" wakeup... where "immediate" actually involves
269	 * taking the PPP channel's ->downl lock, which is held by the
270	 * code path that calls pppoatm_send(), and is thus going to
271	 * wait for us to finish.
272	 */
273	if (atm_may_send(pvcc->atmvcc, size) &&
274	    atomic_inc_not_zero(&pvcc->inflight))
275		return 1;
276
277	return 0;
278}
279/*
280 * Called by the ppp_generic.c to send a packet - returns true if packet
281 * was accepted.  If we return false, then it's our job to call
282 * ppp_output_wakeup(chan) when we're feeling more up to it.
283 * Note that in the ENOMEM case (as opposed to the !atm_may_send case)
284 * we should really drop the packet, but the generic layer doesn't
285 * support this yet.  We just return 'DROP_PACKET' which we actually define
286 * as success, just to be clear what we're really doing.
287 */
288#define DROP_PACKET 1
289static int pppoatm_send(struct ppp_channel *chan, struct sk_buff *skb)
290{
291	struct pppoatm_vcc *pvcc = chan_to_pvcc(chan);
292	struct atm_vcc *vcc;
293	int ret;
294
295	ATM_SKB(skb)->vcc = pvcc->atmvcc;
296	pr_debug("(skb=0x%p, vcc=0x%p)\n", skb, pvcc->atmvcc);
297	if (skb->data[0] == '\0' && (pvcc->flags & SC_COMP_PROT))
298		(void) skb_pull(skb, 1);
299
300	vcc = ATM_SKB(skb)->vcc;
301	bh_lock_sock(sk_atm(vcc));
302	if (sock_owned_by_user(sk_atm(vcc))) {
303		/*
304		 * Needs to happen (and be flushed, hence test_and_) before we unlock
305		 * the socket. It needs to be seen by the time our ->release_cb gets
306		 * called.
307		 */
308		test_and_set_bit(BLOCKED, &pvcc->blocked);
309		goto nospace;
310	}
311	if (test_bit(ATM_VF_RELEASED, &vcc->flags) ||
312	    test_bit(ATM_VF_CLOSE, &vcc->flags) ||
313	    !test_bit(ATM_VF_READY, &vcc->flags)) {
314		bh_unlock_sock(sk_atm(vcc));
315		kfree_skb(skb);
316		return DROP_PACKET;
317	}
318
319	switch (pvcc->encaps) {		/* LLC encapsulation needed */
320	case e_llc:
321		if (skb_headroom(skb) < LLC_LEN) {
322			struct sk_buff *n;
323			n = skb_realloc_headroom(skb, LLC_LEN);
324			if (n != NULL &&
325			    !pppoatm_may_send(pvcc, n->truesize)) {
326				kfree_skb(n);
327				goto nospace;
328			}
329			consume_skb(skb);
330			skb = n;
331			if (skb == NULL) {
332				bh_unlock_sock(sk_atm(vcc));
333				return DROP_PACKET;
334			}
335		} else if (!pppoatm_may_send(pvcc, skb->truesize))
336			goto nospace;
337		memcpy(skb_push(skb, LLC_LEN), pppllc, LLC_LEN);
338		break;
339	case e_vc:
340		if (!pppoatm_may_send(pvcc, skb->truesize))
341			goto nospace;
342		break;
343	case e_autodetect:
344		bh_unlock_sock(sk_atm(vcc));
345		pr_debug("Trying to send without setting encaps!\n");
346		kfree_skb(skb);
347		return 1;
348	}
349
350	atm_account_tx(vcc, skb);
 
351	pr_debug("atm_skb(%p)->vcc(%p)->dev(%p)\n",
352		 skb, ATM_SKB(skb)->vcc, ATM_SKB(skb)->vcc->dev);
353	ret = ATM_SKB(skb)->vcc->send(ATM_SKB(skb)->vcc, skb)
354	    ? DROP_PACKET : 1;
355	bh_unlock_sock(sk_atm(vcc));
356	return ret;
357nospace:
358	bh_unlock_sock(sk_atm(vcc));
359	/*
360	 * We don't have space to send this SKB now, but we might have
361	 * already applied SC_COMP_PROT compression, so may need to undo
362	 */
363	if ((pvcc->flags & SC_COMP_PROT) && skb_headroom(skb) > 0 &&
364	    skb->data[-1] == '\0')
365		(void) skb_push(skb, 1);
366	return 0;
367}
368
369/* This handles ioctls sent to the /dev/ppp interface */
370static int pppoatm_devppp_ioctl(struct ppp_channel *chan, unsigned int cmd,
371	unsigned long arg)
372{
373	switch (cmd) {
374	case PPPIOCGFLAGS:
375		return put_user(chan_to_pvcc(chan)->flags, (int __user *) arg)
376		    ? -EFAULT : 0;
377	case PPPIOCSFLAGS:
378		return get_user(chan_to_pvcc(chan)->flags, (int __user *) arg)
379		    ? -EFAULT : 0;
380	}
381	return -ENOTTY;
382}
383
384static const struct ppp_channel_ops pppoatm_ops = {
385	.start_xmit = pppoatm_send,
386	.ioctl = pppoatm_devppp_ioctl,
387};
388
389static int pppoatm_assign_vcc(struct atm_vcc *atmvcc, void __user *arg)
390{
391	struct atm_backend_ppp be;
392	struct pppoatm_vcc *pvcc;
393	int err;
394
 
 
 
 
395	if (copy_from_user(&be, arg, sizeof be))
396		return -EFAULT;
397	if (be.encaps != PPPOATM_ENCAPS_AUTODETECT &&
398	    be.encaps != PPPOATM_ENCAPS_VC && be.encaps != PPPOATM_ENCAPS_LLC)
399		return -EINVAL;
400	pvcc = kzalloc(sizeof(*pvcc), GFP_KERNEL);
401	if (pvcc == NULL)
402		return -ENOMEM;
403	pvcc->atmvcc = atmvcc;
404
405	/* Maximum is zero, so that we can use atomic_inc_not_zero() */
406	atomic_set(&pvcc->inflight, NONE_INFLIGHT);
407	pvcc->old_push = atmvcc->push;
408	pvcc->old_pop = atmvcc->pop;
409	pvcc->old_owner = atmvcc->owner;
410	pvcc->old_release_cb = atmvcc->release_cb;
411	pvcc->encaps = (enum pppoatm_encaps) be.encaps;
412	pvcc->chan.private = pvcc;
413	pvcc->chan.ops = &pppoatm_ops;
414	pvcc->chan.mtu = atmvcc->qos.txtp.max_sdu - PPP_HDRLEN -
415	    (be.encaps == e_vc ? 0 : LLC_LEN);
416	tasklet_setup(&pvcc->wakeup_tasklet, pppoatm_wakeup_sender);
 
417	err = ppp_register_channel(&pvcc->chan);
418	if (err != 0) {
419		kfree(pvcc);
420		return err;
421	}
422	atmvcc->user_back = pvcc;
423	atmvcc->push = pppoatm_push;
424	atmvcc->pop = pppoatm_pop;
425	atmvcc->release_cb = pppoatm_release_cb;
426	__module_get(THIS_MODULE);
427	atmvcc->owner = THIS_MODULE;
428
429	/* re-process everything received between connection setup and
430	   backend setup */
431	vcc_process_recv_queue(atmvcc);
432	return 0;
433}
434
435/*
436 * This handles ioctls actually performed on our vcc - we must return
437 * -ENOIOCTLCMD for any unrecognized ioctl
438 */
439static int pppoatm_ioctl(struct socket *sock, unsigned int cmd,
440	unsigned long arg)
441{
442	struct atm_vcc *atmvcc = ATM_SD(sock);
443	void __user *argp = (void __user *)arg;
444
445	if (cmd != ATM_SETBACKEND && atmvcc->push != pppoatm_push)
446		return -ENOIOCTLCMD;
447	switch (cmd) {
448	case ATM_SETBACKEND: {
449		atm_backend_t b;
450		if (get_user(b, (atm_backend_t __user *) argp))
451			return -EFAULT;
452		if (b != ATM_BACKEND_PPP)
453			return -ENOIOCTLCMD;
454		if (!capable(CAP_NET_ADMIN))
455			return -EPERM;
456		if (sock->state != SS_CONNECTED)
457			return -EINVAL;
458		return pppoatm_assign_vcc(atmvcc, argp);
459		}
460	case PPPIOCGCHAN:
461		return put_user(ppp_channel_index(&atmvcc_to_pvcc(atmvcc)->
462		    chan), (int __user *) argp) ? -EFAULT : 0;
463	case PPPIOCGUNIT:
464		return put_user(ppp_unit_number(&atmvcc_to_pvcc(atmvcc)->
465		    chan), (int __user *) argp) ? -EFAULT : 0;
466	}
467	return -ENOIOCTLCMD;
468}
469
470static struct atm_ioctl pppoatm_ioctl_ops = {
471	.owner	= THIS_MODULE,
472	.ioctl	= pppoatm_ioctl,
473};
474
475static int __init pppoatm_init(void)
476{
477	register_atm_ioctl(&pppoatm_ioctl_ops);
478	return 0;
479}
480
481static void __exit pppoatm_exit(void)
482{
483	deregister_atm_ioctl(&pppoatm_ioctl_ops);
484}
485
486module_init(pppoatm_init);
487module_exit(pppoatm_exit);
488
489MODULE_AUTHOR("Mitchell Blank Jr <mitch@sfgoth.com>");
490MODULE_DESCRIPTION("RFC2364 PPP over ATM/AAL5");
491MODULE_LICENSE("GPL");