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/interrupt.h> 41 #include <linux/skbuff.h> 42 #include <linux/slab.h> 43 #include <linux/atm.h> 44 #include <linux/atmdev.h> 45 #include <linux/capability.h> 46 #include <linux/ppp_defs.h> 47 #include <linux/if_ppp.h> 48 #include <linux/ppp_channel.h> 49 #include <linux/atmppp.h> 50 51 #include "common.h" 52 53 enum pppoatm_encaps { 54 e_autodetect = PPPOATM_ENCAPS_AUTODETECT, 55 e_vc = PPPOATM_ENCAPS_VC, 56 e_llc = PPPOATM_ENCAPS_LLC, 57 }; 58 59 struct pppoatm_vcc { 60 struct atm_vcc *atmvcc; /* VCC descriptor */ 61 void (*old_push)(struct atm_vcc *, struct sk_buff *); 62 void (*old_pop)(struct atm_vcc *, struct sk_buff *); 63 /* keep old push/pop for detaching */ 64 enum pppoatm_encaps encaps; 65 int flags; /* SC_COMP_PROT - compress protocol */ 66 struct ppp_channel chan; /* interface to generic ppp layer */ 67 struct tasklet_struct wakeup_tasklet; 68 }; 69 70 /* 71 * Header used for LLC Encapsulated PPP (4 bytes) followed by the LCP protocol 72 * ID (0xC021) used in autodetection 73 */ 74 static const unsigned char pppllc[6] = { 0xFE, 0xFE, 0x03, 0xCF, 0xC0, 0x21 }; 75 #define LLC_LEN (4) 76 77 static inline struct pppoatm_vcc *atmvcc_to_pvcc(const struct atm_vcc *atmvcc) 78 { 79 return (struct pppoatm_vcc *) (atmvcc->user_back); 80 } 81 82 static inline struct pppoatm_vcc *chan_to_pvcc(const struct ppp_channel *chan) 83 { 84 return (struct pppoatm_vcc *) (chan->private); 85 } 86 87 /* 88 * We can't do this directly from our _pop handler, since the ppp code 89 * doesn't want to be called in interrupt context, so we do it from 90 * a tasklet 91 */ 92 static void pppoatm_wakeup_sender(unsigned long arg) 93 { 94 ppp_output_wakeup((struct ppp_channel *) arg); 95 } 96 97 /* 98 * This gets called every time the ATM card has finished sending our 99 * skb. The ->old_pop will take care up normal atm flow control, 100 * but we also need to wake up the device if we blocked it 101 */ 102 static void pppoatm_pop(struct atm_vcc *atmvcc, struct sk_buff *skb) 103 { 104 struct pppoatm_vcc *pvcc = atmvcc_to_pvcc(atmvcc); 105 pvcc->old_pop(atmvcc, skb); 106 /* 107 * We don't really always want to do this since it's 108 * really inefficient - it would be much better if we could 109 * test if we had actually throttled the generic layer. 110 * Unfortunately then there would be a nasty SMP race where 111 * we could clear that flag just as we refuse another packet. 112 * For now we do the safe thing. 113 */ 114 tasklet_schedule(&pvcc->wakeup_tasklet); 115 } 116 117 /* 118 * Unbind from PPP - currently we only do this when closing the socket, 119 * but we could put this into an ioctl if need be 120 */ 121 static void pppoatm_unassign_vcc(struct atm_vcc *atmvcc) 122 { 123 struct pppoatm_vcc *pvcc; 124 pvcc = atmvcc_to_pvcc(atmvcc); 125 atmvcc->push = pvcc->old_push; 126 atmvcc->pop = pvcc->old_pop; 127 tasklet_kill(&pvcc->wakeup_tasklet); 128 ppp_unregister_channel(&pvcc->chan); 129 atmvcc->user_back = NULL; 130 kfree(pvcc); 131 /* Gee, I hope we have the big kernel lock here... */ 132 module_put(THIS_MODULE); 133 } 134 135 /* Called when an AAL5 PDU comes in */ 136 static void pppoatm_push(struct atm_vcc *atmvcc, struct sk_buff *skb) 137 { 138 struct pppoatm_vcc *pvcc = atmvcc_to_pvcc(atmvcc); 139 pr_debug("\n"); 140 if (skb == NULL) { /* VCC was closed */ 141 pr_debug("removing ATMPPP VCC %p\n", pvcc); 142 pppoatm_unassign_vcc(atmvcc); 143 atmvcc->push(atmvcc, NULL); /* Pass along bad news */ 144 return; 145 } 146 atm_return(atmvcc, skb->truesize); 147 switch (pvcc->encaps) { 148 case e_llc: 149 if (skb->len < LLC_LEN || 150 memcmp(skb->data, pppllc, LLC_LEN)) 151 goto error; 152 skb_pull(skb, LLC_LEN); 153 break; 154 case e_autodetect: 155 if (pvcc->chan.ppp == NULL) { /* Not bound yet! */ 156 kfree_skb(skb); 157 return; 158 } 159 if (skb->len >= sizeof(pppllc) && 160 !memcmp(skb->data, pppllc, sizeof(pppllc))) { 161 pvcc->encaps = e_llc; 162 skb_pull(skb, LLC_LEN); 163 break; 164 } 165 if (skb->len >= (sizeof(pppllc) - LLC_LEN) && 166 !memcmp(skb->data, &pppllc[LLC_LEN], 167 sizeof(pppllc) - LLC_LEN)) { 168 pvcc->encaps = e_vc; 169 pvcc->chan.mtu += LLC_LEN; 170 break; 171 } 172 pr_debug("Couldn't autodetect yet (skb: %02X %02X %02X %02X %02X %02X)\n", 173 skb->data[0], skb->data[1], skb->data[2], 174 skb->data[3], skb->data[4], skb->data[5]); 175 goto error; 176 case e_vc: 177 break; 178 } 179 ppp_input(&pvcc->chan, skb); 180 return; 181 182 error: 183 kfree_skb(skb); 184 ppp_input_error(&pvcc->chan, 0); 185 } 186 187 /* 188 * Called by the ppp_generic.c to send a packet - returns true if packet 189 * was accepted. If we return false, then it's our job to call 190 * ppp_output_wakeup(chan) when we're feeling more up to it. 191 * Note that in the ENOMEM case (as opposed to the !atm_may_send case) 192 * we should really drop the packet, but the generic layer doesn't 193 * support this yet. We just return 'DROP_PACKET' which we actually define 194 * as success, just to be clear what we're really doing. 195 */ 196 #define DROP_PACKET 1 197 static int pppoatm_send(struct ppp_channel *chan, struct sk_buff *skb) 198 { 199 struct pppoatm_vcc *pvcc = chan_to_pvcc(chan); 200 ATM_SKB(skb)->vcc = pvcc->atmvcc; 201 pr_debug("(skb=0x%p, vcc=0x%p)\n", skb, pvcc->atmvcc); 202 if (skb->data[0] == '\0' && (pvcc->flags & SC_COMP_PROT)) 203 (void) skb_pull(skb, 1); 204 switch (pvcc->encaps) { /* LLC encapsulation needed */ 205 case e_llc: 206 if (skb_headroom(skb) < LLC_LEN) { 207 struct sk_buff *n; 208 n = skb_realloc_headroom(skb, LLC_LEN); 209 if (n != NULL && 210 !atm_may_send(pvcc->atmvcc, n->truesize)) { 211 kfree_skb(n); 212 goto nospace; 213 } 214 kfree_skb(skb); 215 skb = n; 216 if (skb == NULL) 217 return DROP_PACKET; 218 } else if (!atm_may_send(pvcc->atmvcc, skb->truesize)) 219 goto nospace; 220 memcpy(skb_push(skb, LLC_LEN), pppllc, LLC_LEN); 221 break; 222 case e_vc: 223 if (!atm_may_send(pvcc->atmvcc, skb->truesize)) 224 goto nospace; 225 break; 226 case e_autodetect: 227 pr_debug("Trying to send without setting encaps!\n"); 228 kfree_skb(skb); 229 return 1; 230 } 231 232 atomic_add(skb->truesize, &sk_atm(ATM_SKB(skb)->vcc)->sk_wmem_alloc); 233 ATM_SKB(skb)->atm_options = ATM_SKB(skb)->vcc->atm_options; 234 pr_debug("atm_skb(%p)->vcc(%p)->dev(%p)\n", 235 skb, ATM_SKB(skb)->vcc, ATM_SKB(skb)->vcc->dev); 236 return ATM_SKB(skb)->vcc->send(ATM_SKB(skb)->vcc, skb) 237 ? DROP_PACKET : 1; 238 nospace: 239 /* 240 * We don't have space to send this SKB now, but we might have 241 * already applied SC_COMP_PROT compression, so may need to undo 242 */ 243 if ((pvcc->flags & SC_COMP_PROT) && skb_headroom(skb) > 0 && 244 skb->data[-1] == '\0') 245 (void) skb_push(skb, 1); 246 return 0; 247 } 248 249 /* This handles ioctls sent to the /dev/ppp interface */ 250 static int pppoatm_devppp_ioctl(struct ppp_channel *chan, unsigned int cmd, 251 unsigned long arg) 252 { 253 switch (cmd) { 254 case PPPIOCGFLAGS: 255 return put_user(chan_to_pvcc(chan)->flags, (int __user *) arg) 256 ? -EFAULT : 0; 257 case PPPIOCSFLAGS: 258 return get_user(chan_to_pvcc(chan)->flags, (int __user *) arg) 259 ? -EFAULT : 0; 260 } 261 return -ENOTTY; 262 } 263 264 static const struct ppp_channel_ops pppoatm_ops = { 265 .start_xmit = pppoatm_send, 266 .ioctl = pppoatm_devppp_ioctl, 267 }; 268 269 static int pppoatm_assign_vcc(struct atm_vcc *atmvcc, void __user *arg) 270 { 271 struct atm_backend_ppp be; 272 struct pppoatm_vcc *pvcc; 273 int err; 274 /* 275 * Each PPPoATM instance has its own tasklet - this is just a 276 * prototypical one used to initialize them 277 */ 278 static const DECLARE_TASKLET(tasklet_proto, pppoatm_wakeup_sender, 0); 279 if (copy_from_user(&be, arg, sizeof be)) 280 return -EFAULT; 281 if (be.encaps != PPPOATM_ENCAPS_AUTODETECT && 282 be.encaps != PPPOATM_ENCAPS_VC && be.encaps != PPPOATM_ENCAPS_LLC) 283 return -EINVAL; 284 pvcc = kzalloc(sizeof(*pvcc), GFP_KERNEL); 285 if (pvcc == NULL) 286 return -ENOMEM; 287 pvcc->atmvcc = atmvcc; 288 pvcc->old_push = atmvcc->push; 289 pvcc->old_pop = atmvcc->pop; 290 pvcc->encaps = (enum pppoatm_encaps) be.encaps; 291 pvcc->chan.private = pvcc; 292 pvcc->chan.ops = &pppoatm_ops; 293 pvcc->chan.mtu = atmvcc->qos.txtp.max_sdu - PPP_HDRLEN - 294 (be.encaps == e_vc ? 0 : LLC_LEN); 295 pvcc->wakeup_tasklet = tasklet_proto; 296 pvcc->wakeup_tasklet.data = (unsigned long) &pvcc->chan; 297 err = ppp_register_channel(&pvcc->chan); 298 if (err != 0) { 299 kfree(pvcc); 300 return err; 301 } 302 atmvcc->user_back = pvcc; 303 atmvcc->push = pppoatm_push; 304 atmvcc->pop = pppoatm_pop; 305 __module_get(THIS_MODULE); 306 return 0; 307 } 308 309 /* 310 * This handles ioctls actually performed on our vcc - we must return 311 * -ENOIOCTLCMD for any unrecognized ioctl 312 */ 313 static int pppoatm_ioctl(struct socket *sock, unsigned int cmd, 314 unsigned long arg) 315 { 316 struct atm_vcc *atmvcc = ATM_SD(sock); 317 void __user *argp = (void __user *)arg; 318 319 if (cmd != ATM_SETBACKEND && atmvcc->push != pppoatm_push) 320 return -ENOIOCTLCMD; 321 switch (cmd) { 322 case ATM_SETBACKEND: { 323 atm_backend_t b; 324 if (get_user(b, (atm_backend_t __user *) argp)) 325 return -EFAULT; 326 if (b != ATM_BACKEND_PPP) 327 return -ENOIOCTLCMD; 328 if (!capable(CAP_NET_ADMIN)) 329 return -EPERM; 330 return pppoatm_assign_vcc(atmvcc, argp); 331 } 332 case PPPIOCGCHAN: 333 return put_user(ppp_channel_index(&atmvcc_to_pvcc(atmvcc)-> 334 chan), (int __user *) argp) ? -EFAULT : 0; 335 case PPPIOCGUNIT: 336 return put_user(ppp_unit_number(&atmvcc_to_pvcc(atmvcc)-> 337 chan), (int __user *) argp) ? -EFAULT : 0; 338 } 339 return -ENOIOCTLCMD; 340 } 341 342 static struct atm_ioctl pppoatm_ioctl_ops = { 343 .owner = THIS_MODULE, 344 .ioctl = pppoatm_ioctl, 345 }; 346 347 static int __init pppoatm_init(void) 348 { 349 register_atm_ioctl(&pppoatm_ioctl_ops); 350 return 0; 351 } 352 353 static void __exit pppoatm_exit(void) 354 { 355 deregister_atm_ioctl(&pppoatm_ioctl_ops); 356 } 357 358 module_init(pppoatm_init); 359 module_exit(pppoatm_exit); 360 361 MODULE_AUTHOR("Mitchell Blank Jr <mitch@sfgoth.com>"); 362 MODULE_DESCRIPTION("RFC2364 PPP over ATM/AAL5"); 363 MODULE_LICENSE("GPL"); 364