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