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"); 371