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1da177e4 LT |
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 | ||
99824461 JP |
36 | #define pr_fmt(fmt) KBUILD_MODNAME ":%s: " fmt, __func__ |
37 | ||
1da177e4 | 38 | #include <linux/module.h> |
1da177e4 | 39 | #include <linux/init.h> |
a6b7a407 | 40 | #include <linux/interrupt.h> |
1da177e4 | 41 | #include <linux/skbuff.h> |
5a0e3ad6 | 42 | #include <linux/slab.h> |
1da177e4 LT |
43 | #include <linux/atm.h> |
44 | #include <linux/atmdev.h> | |
4fc268d2 | 45 | #include <linux/capability.h> |
1da177e4 | 46 | #include <linux/ppp_defs.h> |
4b32da2b | 47 | #include <linux/ppp-ioctl.h> |
1da177e4 LT |
48 | #include <linux/ppp_channel.h> |
49 | #include <linux/atmppp.h> | |
50 | ||
51 | #include "common.h" | |
52 | ||
1da177e4 LT |
53 | enum pppoatm_encaps { |
54 | e_autodetect = PPPOATM_ENCAPS_AUTODETECT, | |
55 | e_vc = PPPOATM_ENCAPS_VC, | |
56 | e_llc = PPPOATM_ENCAPS_LLC, | |
57 | }; | |
58 | ||
59 | struct 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 | /* keep old push/pop for detaching */ | |
64 | enum pppoatm_encaps encaps; | |
9d02daf7 DW |
65 | atomic_t inflight; |
66 | unsigned long blocked; | |
1da177e4 LT |
67 | int flags; /* SC_COMP_PROT - compress protocol */ |
68 | struct ppp_channel chan; /* interface to generic ppp layer */ | |
69 | struct tasklet_struct wakeup_tasklet; | |
70 | }; | |
71 | ||
9d02daf7 DW |
72 | /* |
73 | * We want to allow two packets in the queue. The one that's currently in | |
74 | * flight, and *one* queued up ready for the ATM device to send immediately | |
75 | * from its TX done IRQ. We want to be able to use atomic_inc_not_zero(), so | |
76 | * inflight == -2 represents an empty queue, -1 one packet, and zero means | |
77 | * there are two packets in the queue. | |
78 | */ | |
79 | #define NONE_INFLIGHT -2 | |
80 | ||
81 | #define BLOCKED 0 | |
82 | ||
1da177e4 LT |
83 | /* |
84 | * Header used for LLC Encapsulated PPP (4 bytes) followed by the LCP protocol | |
85 | * ID (0xC021) used in autodetection | |
86 | */ | |
87 | static const unsigned char pppllc[6] = { 0xFE, 0xFE, 0x03, 0xCF, 0xC0, 0x21 }; | |
88 | #define LLC_LEN (4) | |
89 | ||
90 | static inline struct pppoatm_vcc *atmvcc_to_pvcc(const struct atm_vcc *atmvcc) | |
91 | { | |
92 | return (struct pppoatm_vcc *) (atmvcc->user_back); | |
93 | } | |
94 | ||
95 | static inline struct pppoatm_vcc *chan_to_pvcc(const struct ppp_channel *chan) | |
96 | { | |
97 | return (struct pppoatm_vcc *) (chan->private); | |
98 | } | |
99 | ||
100 | /* | |
101 | * We can't do this directly from our _pop handler, since the ppp code | |
102 | * doesn't want to be called in interrupt context, so we do it from | |
103 | * a tasklet | |
104 | */ | |
105 | static void pppoatm_wakeup_sender(unsigned long arg) | |
106 | { | |
107 | ppp_output_wakeup((struct ppp_channel *) arg); | |
108 | } | |
109 | ||
110 | /* | |
111 | * This gets called every time the ATM card has finished sending our | |
112 | * skb. The ->old_pop will take care up normal atm flow control, | |
113 | * but we also need to wake up the device if we blocked it | |
114 | */ | |
115 | static void pppoatm_pop(struct atm_vcc *atmvcc, struct sk_buff *skb) | |
116 | { | |
117 | struct pppoatm_vcc *pvcc = atmvcc_to_pvcc(atmvcc); | |
9d02daf7 | 118 | |
1da177e4 | 119 | pvcc->old_pop(atmvcc, skb); |
9d02daf7 DW |
120 | atomic_dec(&pvcc->inflight); |
121 | ||
1da177e4 | 122 | /* |
9d02daf7 DW |
123 | * We always used to run the wakeup tasklet unconditionally here, for |
124 | * fear of race conditions where we clear the BLOCKED flag just as we | |
125 | * refuse another packet in pppoatm_send(). This was quite inefficient. | |
126 | * | |
127 | * In fact it's OK. The PPP core will only ever call pppoatm_send() | |
128 | * while holding the channel->downl lock. And ppp_output_wakeup() as | |
129 | * called by the tasklet will *also* grab that lock. So even if another | |
130 | * CPU is in pppoatm_send() right now, the tasklet isn't going to race | |
131 | * with it. The wakeup *will* happen after the other CPU is safely out | |
132 | * of pppoatm_send() again. | |
133 | * | |
134 | * So if the CPU in pppoatm_send() has already set the BLOCKED bit and | |
135 | * it about to return, that's fine. We trigger a wakeup which will | |
136 | * happen later. And if the CPU in pppoatm_send() *hasn't* set the | |
137 | * BLOCKED bit yet, that's fine too because of the double check in | |
138 | * pppoatm_may_send() which is commented there. | |
1da177e4 | 139 | */ |
9d02daf7 DW |
140 | if (test_and_clear_bit(BLOCKED, &pvcc->blocked)) |
141 | tasklet_schedule(&pvcc->wakeup_tasklet); | |
1da177e4 LT |
142 | } |
143 | ||
144 | /* | |
145 | * Unbind from PPP - currently we only do this when closing the socket, | |
146 | * but we could put this into an ioctl if need be | |
147 | */ | |
148 | static void pppoatm_unassign_vcc(struct atm_vcc *atmvcc) | |
149 | { | |
150 | struct pppoatm_vcc *pvcc; | |
151 | pvcc = atmvcc_to_pvcc(atmvcc); | |
152 | atmvcc->push = pvcc->old_push; | |
153 | atmvcc->pop = pvcc->old_pop; | |
154 | tasklet_kill(&pvcc->wakeup_tasklet); | |
155 | ppp_unregister_channel(&pvcc->chan); | |
156 | atmvcc->user_back = NULL; | |
157 | kfree(pvcc); | |
158 | /* Gee, I hope we have the big kernel lock here... */ | |
159 | module_put(THIS_MODULE); | |
160 | } | |
161 | ||
162 | /* Called when an AAL5 PDU comes in */ | |
163 | static void pppoatm_push(struct atm_vcc *atmvcc, struct sk_buff *skb) | |
164 | { | |
165 | struct pppoatm_vcc *pvcc = atmvcc_to_pvcc(atmvcc); | |
99824461 | 166 | pr_debug("\n"); |
1da177e4 | 167 | if (skb == NULL) { /* VCC was closed */ |
52240062 | 168 | pr_debug("removing ATMPPP VCC %p\n", pvcc); |
1da177e4 LT |
169 | pppoatm_unassign_vcc(atmvcc); |
170 | atmvcc->push(atmvcc, NULL); /* Pass along bad news */ | |
171 | return; | |
172 | } | |
173 | atm_return(atmvcc, skb->truesize); | |
174 | switch (pvcc->encaps) { | |
175 | case e_llc: | |
176 | if (skb->len < LLC_LEN || | |
177 | memcmp(skb->data, pppllc, LLC_LEN)) | |
178 | goto error; | |
179 | skb_pull(skb, LLC_LEN); | |
180 | break; | |
181 | case e_autodetect: | |
182 | if (pvcc->chan.ppp == NULL) { /* Not bound yet! */ | |
183 | kfree_skb(skb); | |
184 | return; | |
185 | } | |
186 | if (skb->len >= sizeof(pppllc) && | |
187 | !memcmp(skb->data, pppllc, sizeof(pppllc))) { | |
188 | pvcc->encaps = e_llc; | |
189 | skb_pull(skb, LLC_LEN); | |
190 | break; | |
191 | } | |
192 | if (skb->len >= (sizeof(pppllc) - LLC_LEN) && | |
193 | !memcmp(skb->data, &pppllc[LLC_LEN], | |
194 | sizeof(pppllc) - LLC_LEN)) { | |
195 | pvcc->encaps = e_vc; | |
196 | pvcc->chan.mtu += LLC_LEN; | |
197 | break; | |
198 | } | |
99824461 JP |
199 | pr_debug("Couldn't autodetect yet (skb: %02X %02X %02X %02X %02X %02X)\n", |
200 | skb->data[0], skb->data[1], skb->data[2], | |
201 | skb->data[3], skb->data[4], skb->data[5]); | |
1da177e4 LT |
202 | goto error; |
203 | case e_vc: | |
204 | break; | |
205 | } | |
206 | ppp_input(&pvcc->chan, skb); | |
207 | return; | |
d81219db JP |
208 | |
209 | error: | |
1da177e4 LT |
210 | kfree_skb(skb); |
211 | ppp_input_error(&pvcc->chan, 0); | |
212 | } | |
213 | ||
9d02daf7 DW |
214 | static inline int pppoatm_may_send(struct pppoatm_vcc *pvcc, int size) |
215 | { | |
216 | /* | |
217 | * It's not clear that we need to bother with using atm_may_send() | |
218 | * to check we don't exceed sk->sk_sndbuf. If userspace sets a | |
219 | * value of sk_sndbuf which is lower than the MTU, we're going to | |
220 | * block for ever. But the code always did that before we introduced | |
221 | * the packet count limit, so... | |
222 | */ | |
223 | if (atm_may_send(pvcc->atmvcc, size) && | |
224 | atomic_inc_not_zero_hint(&pvcc->inflight, NONE_INFLIGHT)) | |
225 | return 1; | |
226 | ||
227 | /* | |
228 | * We use test_and_set_bit() rather than set_bit() here because | |
229 | * we need to ensure there's a memory barrier after it. The bit | |
230 | * *must* be set before we do the atomic_inc() on pvcc->inflight. | |
231 | * There's no smp_mb__after_set_bit(), so it's this or abuse | |
232 | * smp_mb__after_clear_bit(). | |
233 | */ | |
234 | test_and_set_bit(BLOCKED, &pvcc->blocked); | |
235 | ||
236 | /* | |
237 | * We may have raced with pppoatm_pop(). If it ran for the | |
238 | * last packet in the queue, *just* before we set the BLOCKED | |
239 | * bit, then it might never run again and the channel could | |
240 | * remain permanently blocked. Cope with that race by checking | |
241 | * *again*. If it did run in that window, we'll have space on | |
242 | * the queue now and can return success. It's harmless to leave | |
243 | * the BLOCKED flag set, since it's only used as a trigger to | |
244 | * run the wakeup tasklet. Another wakeup will never hurt. | |
245 | * If pppoatm_pop() is running but hasn't got as far as making | |
246 | * space on the queue yet, then it hasn't checked the BLOCKED | |
247 | * flag yet either, so we're safe in that case too. It'll issue | |
248 | * an "immediate" wakeup... where "immediate" actually involves | |
249 | * taking the PPP channel's ->downl lock, which is held by the | |
250 | * code path that calls pppoatm_send(), and is thus going to | |
251 | * wait for us to finish. | |
252 | */ | |
253 | if (atm_may_send(pvcc->atmvcc, size) && | |
254 | atomic_inc_not_zero(&pvcc->inflight)) | |
255 | return 1; | |
256 | ||
257 | return 0; | |
258 | } | |
1da177e4 LT |
259 | /* |
260 | * Called by the ppp_generic.c to send a packet - returns true if packet | |
261 | * was accepted. If we return false, then it's our job to call | |
262 | * ppp_output_wakeup(chan) when we're feeling more up to it. | |
263 | * Note that in the ENOMEM case (as opposed to the !atm_may_send case) | |
264 | * we should really drop the packet, but the generic layer doesn't | |
265 | * support this yet. We just return 'DROP_PACKET' which we actually define | |
266 | * as success, just to be clear what we're really doing. | |
267 | */ | |
268 | #define DROP_PACKET 1 | |
269 | static int pppoatm_send(struct ppp_channel *chan, struct sk_buff *skb) | |
270 | { | |
271 | struct pppoatm_vcc *pvcc = chan_to_pvcc(chan); | |
272 | ATM_SKB(skb)->vcc = pvcc->atmvcc; | |
99824461 | 273 | pr_debug("(skb=0x%p, vcc=0x%p)\n", skb, pvcc->atmvcc); |
1da177e4 LT |
274 | if (skb->data[0] == '\0' && (pvcc->flags & SC_COMP_PROT)) |
275 | (void) skb_pull(skb, 1); | |
276 | switch (pvcc->encaps) { /* LLC encapsulation needed */ | |
277 | case e_llc: | |
278 | if (skb_headroom(skb) < LLC_LEN) { | |
279 | struct sk_buff *n; | |
280 | n = skb_realloc_headroom(skb, LLC_LEN); | |
281 | if (n != NULL && | |
9d02daf7 | 282 | !pppoatm_may_send(pvcc, n->truesize)) { |
1da177e4 LT |
283 | kfree_skb(n); |
284 | goto nospace; | |
285 | } | |
5d0ba55b | 286 | consume_skb(skb); |
d81219db JP |
287 | skb = n; |
288 | if (skb == NULL) | |
1da177e4 | 289 | return DROP_PACKET; |
9d02daf7 | 290 | } else if (!pppoatm_may_send(pvcc, skb->truesize)) |
1da177e4 LT |
291 | goto nospace; |
292 | memcpy(skb_push(skb, LLC_LEN), pppllc, LLC_LEN); | |
293 | break; | |
294 | case e_vc: | |
9d02daf7 | 295 | if (!pppoatm_may_send(pvcc, skb->truesize)) |
1da177e4 LT |
296 | goto nospace; |
297 | break; | |
298 | case e_autodetect: | |
52240062 | 299 | pr_debug("Trying to send without setting encaps!\n"); |
1da177e4 LT |
300 | kfree_skb(skb); |
301 | return 1; | |
302 | } | |
303 | ||
304 | atomic_add(skb->truesize, &sk_atm(ATM_SKB(skb)->vcc)->sk_wmem_alloc); | |
305 | ATM_SKB(skb)->atm_options = ATM_SKB(skb)->vcc->atm_options; | |
99824461 JP |
306 | pr_debug("atm_skb(%p)->vcc(%p)->dev(%p)\n", |
307 | skb, ATM_SKB(skb)->vcc, ATM_SKB(skb)->vcc->dev); | |
1da177e4 LT |
308 | return ATM_SKB(skb)->vcc->send(ATM_SKB(skb)->vcc, skb) |
309 | ? DROP_PACKET : 1; | |
d81219db | 310 | nospace: |
1da177e4 LT |
311 | /* |
312 | * We don't have space to send this SKB now, but we might have | |
313 | * already applied SC_COMP_PROT compression, so may need to undo | |
314 | */ | |
315 | if ((pvcc->flags & SC_COMP_PROT) && skb_headroom(skb) > 0 && | |
316 | skb->data[-1] == '\0') | |
317 | (void) skb_push(skb, 1); | |
318 | return 0; | |
319 | } | |
320 | ||
321 | /* This handles ioctls sent to the /dev/ppp interface */ | |
322 | static int pppoatm_devppp_ioctl(struct ppp_channel *chan, unsigned int cmd, | |
323 | unsigned long arg) | |
324 | { | |
325 | switch (cmd) { | |
326 | case PPPIOCGFLAGS: | |
327 | return put_user(chan_to_pvcc(chan)->flags, (int __user *) arg) | |
328 | ? -EFAULT : 0; | |
329 | case PPPIOCSFLAGS: | |
330 | return get_user(chan_to_pvcc(chan)->flags, (int __user *) arg) | |
331 | ? -EFAULT : 0; | |
332 | } | |
333 | return -ENOTTY; | |
334 | } | |
335 | ||
d7100da0 | 336 | static const struct ppp_channel_ops pppoatm_ops = { |
1da177e4 LT |
337 | .start_xmit = pppoatm_send, |
338 | .ioctl = pppoatm_devppp_ioctl, | |
339 | }; | |
340 | ||
341 | static int pppoatm_assign_vcc(struct atm_vcc *atmvcc, void __user *arg) | |
342 | { | |
343 | struct atm_backend_ppp be; | |
344 | struct pppoatm_vcc *pvcc; | |
345 | int err; | |
346 | /* | |
347 | * Each PPPoATM instance has its own tasklet - this is just a | |
348 | * prototypical one used to initialize them | |
349 | */ | |
350 | static const DECLARE_TASKLET(tasklet_proto, pppoatm_wakeup_sender, 0); | |
351 | if (copy_from_user(&be, arg, sizeof be)) | |
352 | return -EFAULT; | |
353 | if (be.encaps != PPPOATM_ENCAPS_AUTODETECT && | |
354 | be.encaps != PPPOATM_ENCAPS_VC && be.encaps != PPPOATM_ENCAPS_LLC) | |
355 | return -EINVAL; | |
0da974f4 | 356 | pvcc = kzalloc(sizeof(*pvcc), GFP_KERNEL); |
1da177e4 LT |
357 | if (pvcc == NULL) |
358 | return -ENOMEM; | |
1da177e4 | 359 | pvcc->atmvcc = atmvcc; |
9d02daf7 DW |
360 | |
361 | /* Maximum is zero, so that we can use atomic_inc_not_zero() */ | |
362 | atomic_set(&pvcc->inflight, NONE_INFLIGHT); | |
1da177e4 LT |
363 | pvcc->old_push = atmvcc->push; |
364 | pvcc->old_pop = atmvcc->pop; | |
365 | pvcc->encaps = (enum pppoatm_encaps) be.encaps; | |
366 | pvcc->chan.private = pvcc; | |
367 | pvcc->chan.ops = &pppoatm_ops; | |
368 | pvcc->chan.mtu = atmvcc->qos.txtp.max_sdu - PPP_HDRLEN - | |
369 | (be.encaps == e_vc ? 0 : LLC_LEN); | |
370 | pvcc->wakeup_tasklet = tasklet_proto; | |
371 | pvcc->wakeup_tasklet.data = (unsigned long) &pvcc->chan; | |
d81219db JP |
372 | err = ppp_register_channel(&pvcc->chan); |
373 | if (err != 0) { | |
1da177e4 LT |
374 | kfree(pvcc); |
375 | return err; | |
376 | } | |
377 | atmvcc->user_back = pvcc; | |
378 | atmvcc->push = pppoatm_push; | |
379 | atmvcc->pop = pppoatm_pop; | |
380 | __module_get(THIS_MODULE); | |
4e55f578 JBD |
381 | |
382 | /* re-process everything received between connection setup and | |
383 | backend setup */ | |
384 | vcc_process_recv_queue(atmvcc); | |
1da177e4 LT |
385 | return 0; |
386 | } | |
387 | ||
388 | /* | |
389 | * This handles ioctls actually performed on our vcc - we must return | |
390 | * -ENOIOCTLCMD for any unrecognized ioctl | |
391 | */ | |
392 | static int pppoatm_ioctl(struct socket *sock, unsigned int cmd, | |
393 | unsigned long arg) | |
394 | { | |
395 | struct atm_vcc *atmvcc = ATM_SD(sock); | |
396 | void __user *argp = (void __user *)arg; | |
397 | ||
398 | if (cmd != ATM_SETBACKEND && atmvcc->push != pppoatm_push) | |
399 | return -ENOIOCTLCMD; | |
400 | switch (cmd) { | |
401 | case ATM_SETBACKEND: { | |
402 | atm_backend_t b; | |
403 | if (get_user(b, (atm_backend_t __user *) argp)) | |
404 | return -EFAULT; | |
405 | if (b != ATM_BACKEND_PPP) | |
406 | return -ENOIOCTLCMD; | |
407 | if (!capable(CAP_NET_ADMIN)) | |
408 | return -EPERM; | |
409 | return pppoatm_assign_vcc(atmvcc, argp); | |
410 | } | |
411 | case PPPIOCGCHAN: | |
412 | return put_user(ppp_channel_index(&atmvcc_to_pvcc(atmvcc)-> | |
413 | chan), (int __user *) argp) ? -EFAULT : 0; | |
414 | case PPPIOCGUNIT: | |
415 | return put_user(ppp_unit_number(&atmvcc_to_pvcc(atmvcc)-> | |
416 | chan), (int __user *) argp) ? -EFAULT : 0; | |
417 | } | |
418 | return -ENOIOCTLCMD; | |
419 | } | |
420 | ||
421 | static struct atm_ioctl pppoatm_ioctl_ops = { | |
422 | .owner = THIS_MODULE, | |
423 | .ioctl = pppoatm_ioctl, | |
424 | }; | |
425 | ||
426 | static int __init pppoatm_init(void) | |
427 | { | |
428 | register_atm_ioctl(&pppoatm_ioctl_ops); | |
429 | return 0; | |
430 | } | |
431 | ||
432 | static void __exit pppoatm_exit(void) | |
433 | { | |
434 | deregister_atm_ioctl(&pppoatm_ioctl_ops); | |
435 | } | |
436 | ||
437 | module_init(pppoatm_init); | |
438 | module_exit(pppoatm_exit); | |
439 | ||
440 | MODULE_AUTHOR("Mitchell Blank Jr <mitch@sfgoth.com>"); | |
441 | MODULE_DESCRIPTION("RFC2364 PPP over ATM/AAL5"); | |
442 | MODULE_LICENSE("GPL"); |