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