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