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"); 363