net/atm/pppoatm.c

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