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