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Linus Torvalds1da177e2005-04-16 15:20:36 -07001/* 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#include <linux/module.h>
37#include <linux/config.h>
38#include <linux/init.h>
39#include <linux/skbuff.h>
40#include <linux/atm.h>
41#include <linux/atmdev.h>
42#include <linux/ppp_defs.h>
43#include <linux/if_ppp.h>
44#include <linux/ppp_channel.h>
45#include <linux/atmppp.h>
46
47#include "common.h"
48
49#if 0
50#define DPRINTK(format, args...) \
51 printk(KERN_DEBUG "pppoatm: " format, ##args)
52#else
53#define DPRINTK(format, args...)
54#endif
55
56enum pppoatm_encaps {
57 e_autodetect = PPPOATM_ENCAPS_AUTODETECT,
58 e_vc = PPPOATM_ENCAPS_VC,
59 e_llc = PPPOATM_ENCAPS_LLC,
60};
61
62struct pppoatm_vcc {
63 struct atm_vcc *atmvcc; /* VCC descriptor */
64 void (*old_push)(struct atm_vcc *, struct sk_buff *);
65 void (*old_pop)(struct atm_vcc *, struct sk_buff *);
66 /* keep old push/pop for detaching */
67 enum pppoatm_encaps encaps;
68 int flags; /* SC_COMP_PROT - compress protocol */
69 struct ppp_channel chan; /* interface to generic ppp layer */
70 struct tasklet_struct wakeup_tasklet;
71};
72
73/*
74 * Header used for LLC Encapsulated PPP (4 bytes) followed by the LCP protocol
75 * ID (0xC021) used in autodetection
76 */
77static const unsigned char pppllc[6] = { 0xFE, 0xFE, 0x03, 0xCF, 0xC0, 0x21 };
78#define LLC_LEN (4)
79
80static inline struct pppoatm_vcc *atmvcc_to_pvcc(const struct atm_vcc *atmvcc)
81{
82 return (struct pppoatm_vcc *) (atmvcc->user_back);
83}
84
85static inline struct pppoatm_vcc *chan_to_pvcc(const struct ppp_channel *chan)
86{
87 return (struct pppoatm_vcc *) (chan->private);
88}
89
90/*
91 * We can't do this directly from our _pop handler, since the ppp code
92 * doesn't want to be called in interrupt context, so we do it from
93 * a tasklet
94 */
95static void pppoatm_wakeup_sender(unsigned long arg)
96{
97 ppp_output_wakeup((struct ppp_channel *) arg);
98}
99
100/*
101 * This gets called every time the ATM card has finished sending our
102 * skb. The ->old_pop will take care up normal atm flow control,
103 * but we also need to wake up the device if we blocked it
104 */
105static void pppoatm_pop(struct atm_vcc *atmvcc, struct sk_buff *skb)
106{
107 struct pppoatm_vcc *pvcc = atmvcc_to_pvcc(atmvcc);
108 pvcc->old_pop(atmvcc, skb);
109 /*
110 * We don't really always want to do this since it's
111 * really inefficient - it would be much better if we could
112 * test if we had actually throttled the generic layer.
113 * Unfortunately then there would be a nasty SMP race where
114 * we could clear that flag just as we refuse another packet.
115 * For now we do the safe thing.
116 */
117 tasklet_schedule(&pvcc->wakeup_tasklet);
118}
119
120/*
121 * Unbind from PPP - currently we only do this when closing the socket,
122 * but we could put this into an ioctl if need be
123 */
124static void pppoatm_unassign_vcc(struct atm_vcc *atmvcc)
125{
126 struct pppoatm_vcc *pvcc;
127 pvcc = atmvcc_to_pvcc(atmvcc);
128 atmvcc->push = pvcc->old_push;
129 atmvcc->pop = pvcc->old_pop;
130 tasklet_kill(&pvcc->wakeup_tasklet);
131 ppp_unregister_channel(&pvcc->chan);
132 atmvcc->user_back = NULL;
133 kfree(pvcc);
134 /* Gee, I hope we have the big kernel lock here... */
135 module_put(THIS_MODULE);
136}
137
138/* Called when an AAL5 PDU comes in */
139static void pppoatm_push(struct atm_vcc *atmvcc, struct sk_buff *skb)
140{
141 struct pppoatm_vcc *pvcc = atmvcc_to_pvcc(atmvcc);
142 DPRINTK("pppoatm push\n");
143 if (skb == NULL) { /* VCC was closed */
144 DPRINTK("removing ATMPPP VCC %p\n", pvcc);
145 pppoatm_unassign_vcc(atmvcc);
146 atmvcc->push(atmvcc, NULL); /* Pass along bad news */
147 return;
148 }
149 atm_return(atmvcc, skb->truesize);
150 switch (pvcc->encaps) {
151 case e_llc:
152 if (skb->len < LLC_LEN ||
153 memcmp(skb->data, pppllc, LLC_LEN))
154 goto error;
155 skb_pull(skb, LLC_LEN);
156 break;
157 case e_autodetect:
158 if (pvcc->chan.ppp == NULL) { /* Not bound yet! */
159 kfree_skb(skb);
160 return;
161 }
162 if (skb->len >= sizeof(pppllc) &&
163 !memcmp(skb->data, pppllc, sizeof(pppllc))) {
164 pvcc->encaps = e_llc;
165 skb_pull(skb, LLC_LEN);
166 break;
167 }
168 if (skb->len >= (sizeof(pppllc) - LLC_LEN) &&
169 !memcmp(skb->data, &pppllc[LLC_LEN],
170 sizeof(pppllc) - LLC_LEN)) {
171 pvcc->encaps = e_vc;
172 pvcc->chan.mtu += LLC_LEN;
173 break;
174 }
175 DPRINTK("(unit %d): Couldn't autodetect yet "
176 "(skb: %02X %02X %02X %02X %02X %02X)\n",
177 pvcc->chan.unit,
178 skb->data[0], skb->data[1], skb->data[2],
179 skb->data[3], skb->data[4], skb->data[5]);
180 goto error;
181 case e_vc:
182 break;
183 }
184 ppp_input(&pvcc->chan, skb);
185 return;
186 error:
187 kfree_skb(skb);
188 ppp_input_error(&pvcc->chan, 0);
189}
190
191/*
192 * Called by the ppp_generic.c to send a packet - returns true if packet
193 * was accepted. If we return false, then it's our job to call
194 * ppp_output_wakeup(chan) when we're feeling more up to it.
195 * Note that in the ENOMEM case (as opposed to the !atm_may_send case)
196 * we should really drop the packet, but the generic layer doesn't
197 * support this yet. We just return 'DROP_PACKET' which we actually define
198 * as success, just to be clear what we're really doing.
199 */
200#define DROP_PACKET 1
201static int pppoatm_send(struct ppp_channel *chan, struct sk_buff *skb)
202{
203 struct pppoatm_vcc *pvcc = chan_to_pvcc(chan);
204 ATM_SKB(skb)->vcc = pvcc->atmvcc;
205 DPRINTK("(unit %d): pppoatm_send (skb=0x%p, vcc=0x%p)\n",
206 pvcc->chan.unit, skb, pvcc->atmvcc);
207 if (skb->data[0] == '\0' && (pvcc->flags & SC_COMP_PROT))
208 (void) skb_pull(skb, 1);
209 switch (pvcc->encaps) { /* LLC encapsulation needed */
210 case e_llc:
211 if (skb_headroom(skb) < LLC_LEN) {
212 struct sk_buff *n;
213 n = skb_realloc_headroom(skb, LLC_LEN);
214 if (n != NULL &&
215 !atm_may_send(pvcc->atmvcc, n->truesize)) {
216 kfree_skb(n);
217 goto nospace;
218 }
219 kfree_skb(skb);
220 if ((skb = n) == NULL)
221 return DROP_PACKET;
222 } else if (!atm_may_send(pvcc->atmvcc, skb->truesize))
223 goto nospace;
224 memcpy(skb_push(skb, LLC_LEN), pppllc, LLC_LEN);
225 break;
226 case e_vc:
227 if (!atm_may_send(pvcc->atmvcc, skb->truesize))
228 goto nospace;
229 break;
230 case e_autodetect:
231 DPRINTK("(unit %d): Trying to send without setting encaps!\n",
232 pvcc->chan.unit);
233 kfree_skb(skb);
234 return 1;
235 }
236
237 atomic_add(skb->truesize, &sk_atm(ATM_SKB(skb)->vcc)->sk_wmem_alloc);
238 ATM_SKB(skb)->atm_options = ATM_SKB(skb)->vcc->atm_options;
239 DPRINTK("(unit %d): atm_skb(%p)->vcc(%p)->dev(%p)\n",
240 pvcc->chan.unit, skb, ATM_SKB(skb)->vcc,
241 ATM_SKB(skb)->vcc->dev);
242 return ATM_SKB(skb)->vcc->send(ATM_SKB(skb)->vcc, skb)
243 ? DROP_PACKET : 1;
244 nospace:
245 /*
246 * We don't have space to send this SKB now, but we might have
247 * already applied SC_COMP_PROT compression, so may need to undo
248 */
249 if ((pvcc->flags & SC_COMP_PROT) && skb_headroom(skb) > 0 &&
250 skb->data[-1] == '\0')
251 (void) skb_push(skb, 1);
252 return 0;
253}
254
255/* This handles ioctls sent to the /dev/ppp interface */
256static int pppoatm_devppp_ioctl(struct ppp_channel *chan, unsigned int cmd,
257 unsigned long arg)
258{
259 switch (cmd) {
260 case PPPIOCGFLAGS:
261 return put_user(chan_to_pvcc(chan)->flags, (int __user *) arg)
262 ? -EFAULT : 0;
263 case PPPIOCSFLAGS:
264 return get_user(chan_to_pvcc(chan)->flags, (int __user *) arg)
265 ? -EFAULT : 0;
266 }
267 return -ENOTTY;
268}
269
270static /*const*/ struct ppp_channel_ops pppoatm_ops = {
271 .start_xmit = pppoatm_send,
272 .ioctl = pppoatm_devppp_ioctl,
273};
274
275static int pppoatm_assign_vcc(struct atm_vcc *atmvcc, void __user *arg)
276{
277 struct atm_backend_ppp be;
278 struct pppoatm_vcc *pvcc;
279 int err;
280 /*
281 * Each PPPoATM instance has its own tasklet - this is just a
282 * prototypical one used to initialize them
283 */
284 static const DECLARE_TASKLET(tasklet_proto, pppoatm_wakeup_sender, 0);
285 if (copy_from_user(&be, arg, sizeof be))
286 return -EFAULT;
287 if (be.encaps != PPPOATM_ENCAPS_AUTODETECT &&
288 be.encaps != PPPOATM_ENCAPS_VC && be.encaps != PPPOATM_ENCAPS_LLC)
289 return -EINVAL;
290 pvcc = kmalloc(sizeof(*pvcc), GFP_KERNEL);
291 if (pvcc == NULL)
292 return -ENOMEM;
293 memset(pvcc, 0, sizeof(*pvcc));
294 pvcc->atmvcc = atmvcc;
295 pvcc->old_push = atmvcc->push;
296 pvcc->old_pop = atmvcc->pop;
297 pvcc->encaps = (enum pppoatm_encaps) be.encaps;
298 pvcc->chan.private = pvcc;
299 pvcc->chan.ops = &pppoatm_ops;
300 pvcc->chan.mtu = atmvcc->qos.txtp.max_sdu - PPP_HDRLEN -
301 (be.encaps == e_vc ? 0 : LLC_LEN);
302 pvcc->wakeup_tasklet = tasklet_proto;
303 pvcc->wakeup_tasklet.data = (unsigned long) &pvcc->chan;
304 if ((err = ppp_register_channel(&pvcc->chan)) != 0) {
305 kfree(pvcc);
306 return err;
307 }
308 atmvcc->user_back = pvcc;
309 atmvcc->push = pppoatm_push;
310 atmvcc->pop = pppoatm_pop;
311 __module_get(THIS_MODULE);
312 return 0;
313}
314
315/*
316 * This handles ioctls actually performed on our vcc - we must return
317 * -ENOIOCTLCMD for any unrecognized ioctl
318 */
319static int pppoatm_ioctl(struct socket *sock, unsigned int cmd,
320 unsigned long arg)
321{
322 struct atm_vcc *atmvcc = ATM_SD(sock);
323 void __user *argp = (void __user *)arg;
324
325 if (cmd != ATM_SETBACKEND && atmvcc->push != pppoatm_push)
326 return -ENOIOCTLCMD;
327 switch (cmd) {
328 case ATM_SETBACKEND: {
329 atm_backend_t b;
330 if (get_user(b, (atm_backend_t __user *) argp))
331 return -EFAULT;
332 if (b != ATM_BACKEND_PPP)
333 return -ENOIOCTLCMD;
334 if (!capable(CAP_NET_ADMIN))
335 return -EPERM;
336 return pppoatm_assign_vcc(atmvcc, argp);
337 }
338 case PPPIOCGCHAN:
339 return put_user(ppp_channel_index(&atmvcc_to_pvcc(atmvcc)->
340 chan), (int __user *) argp) ? -EFAULT : 0;
341 case PPPIOCGUNIT:
342 return put_user(ppp_unit_number(&atmvcc_to_pvcc(atmvcc)->
343 chan), (int __user *) argp) ? -EFAULT : 0;
344 }
345 return -ENOIOCTLCMD;
346}
347
348static struct atm_ioctl pppoatm_ioctl_ops = {
349 .owner = THIS_MODULE,
350 .ioctl = pppoatm_ioctl,
351};
352
353static int __init pppoatm_init(void)
354{
355 register_atm_ioctl(&pppoatm_ioctl_ops);
356 return 0;
357}
358
359static void __exit pppoatm_exit(void)
360{
361 deregister_atm_ioctl(&pppoatm_ioctl_ops);
362}
363
364module_init(pppoatm_init);
365module_exit(pppoatm_exit);
366
367MODULE_AUTHOR("Mitchell Blank Jr <mitch@sfgoth.com>");
368MODULE_DESCRIPTION("RFC2364 PPP over ATM/AAL5");
369MODULE_LICENSE("GPL");