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"); 362