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 #include <linux/module.h>
  37 #include <linux/init.h>
  38 #include <linux/skbuff.h>
  39 #include <linux/atm.h>
  40 #include <linux/atmdev.h>
  41 #include <linux/capability.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
  56 enum pppoatm_encaps {
  57         e_autodetect = PPPOATM_ENCAPS_AUTODETECT,
  58         e_vc = PPPOATM_ENCAPS_VC,
  59         e_llc = PPPOATM_ENCAPS_LLC,
  60 };
  61
  62 struct 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  */
  77 static const unsigned char pppllc[6] = { 0xFE, 0xFE, 0x03, 0xCF, 0xC0, 0x21 };
  78 #define LLC_LEN         (4)
  79
  80 static inline struct pppoatm_vcc *atmvcc_to_pvcc(const struct atm_vcc *atmvcc)
  81 {
  82         return (struct pppoatm_vcc *) (atmvcc->user_back);
  83 }
  84
  85 static 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  */
  95 static 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  */
 105 static 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  */
 124 static 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 */
 139 static 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
 201 static 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 */
 256 static 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
 270 static /*const*/ struct ppp_channel_ops pppoatm_ops = {
 271         .start_xmit = pppoatm_send,
 272         .ioctl = pppoatm_devppp_ioctl,
 273 };
 274
 275 static 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 = kzalloc(sizeof(*pvcc), GFP_KERNEL);
 291         if (pvcc == NULL)
 292                 return -ENOMEM;
 293         pvcc->atmvcc = atmvcc;
 294         pvcc->old_push = atmvcc->push;
 295         pvcc->old_pop = atmvcc->pop;
 296         pvcc->encaps = (enum pppoatm_encaps) be.encaps;
 297         pvcc->chan.private = pvcc;
 298         pvcc->chan.ops = &pppoatm_ops;
 299         pvcc->chan.mtu = atmvcc->qos.txtp.max_sdu - PPP_HDRLEN -
 300             (be.encaps == e_vc ? 0 : LLC_LEN);
 301         pvcc->wakeup_tasklet = tasklet_proto;
 302         pvcc->wakeup_tasklet.data = (unsigned long) &pvcc->chan;
 303         if ((err = ppp_register_channel(&pvcc->chan)) != 0) {
 304                 kfree(pvcc);
 305                 return err;
 306         }
 307         atmvcc->user_back = pvcc;
 308         atmvcc->push = pppoatm_push;
 309         atmvcc->pop = pppoatm_pop;
 310         __module_get(THIS_MODULE);
 311         return 0;
 312 }
 313
 314 /*
 315  * This handles ioctls actually performed on our vcc - we must return
 316  * -ENOIOCTLCMD for any unrecognized ioctl
 317  */
 318 static int pppoatm_ioctl(struct socket *sock, unsigned int cmd,
 319         unsigned long arg)
 320 {
 321         struct atm_vcc *atmvcc = ATM_SD(sock);
 322         void __user *argp = (void __user *)arg;
 323
 324         if (cmd != ATM_SETBACKEND && atmvcc->push != pppoatm_push)
 325                 return -ENOIOCTLCMD;
 326         switch (cmd) {
 327         case ATM_SETBACKEND: {
 328                 atm_backend_t b;
 329                 if (get_user(b, (atm_backend_t __user *) argp))
 330                         return -EFAULT;
 331                 if (b != ATM_BACKEND_PPP)
 332                         return -ENOIOCTLCMD;
 333                 if (!capable(CAP_NET_ADMIN))
 334                         return -EPERM;
 335                 return pppoatm_assign_vcc(atmvcc, argp);
 336                 }
 337         case PPPIOCGCHAN:
 338                 return put_user(ppp_channel_index(&atmvcc_to_pvcc(atmvcc)->
 339                     chan), (int __user *) argp) ? -EFAULT : 0;
 340         case PPPIOCGUNIT:
 341                 return put_user(ppp_unit_number(&atmvcc_to_pvcc(atmvcc)->
 342                     chan), (int __user *) argp) ? -EFAULT : 0;
 343         }
 344         return -ENOIOCTLCMD;
 345 }
 346
 347 static struct atm_ioctl pppoatm_ioctl_ops = {
 348         .owner  = THIS_MODULE,
 349         .ioctl  = pppoatm_ioctl,
 350 };
 351
 352 static int __init pppoatm_init(void)
 353 {
 354         register_atm_ioctl(&pppoatm_ioctl_ops);
 355         return 0;
 356 }
 357
 358 static void __exit pppoatm_exit(void)
 359 {
 360         deregister_atm_ioctl(&pppoatm_ioctl_ops);
 361 }
 362
 363 module_init(pppoatm_init);
 364 module_exit(pppoatm_exit);
 365
 366 MODULE_AUTHOR("Mitchell Blank Jr <mitch@sfgoth.com>");
 367 MODULE_DESCRIPTION("RFC2364 PPP over ATM/AAL5");
 368 MODULE_LICENSE("GPL");