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/init.h> 38 #include <linux/skbuff.h> 39 #include <linux/atm.h> 40 #include <linux/atmdev.h> 41 #include <linux/capability.h> 42 #include <linux/ppp_defs.h> 43 #include <linux/if_ppp.h> 44 #include <linux/ppp_channel.h> 45 #include <linux/atmppp.h> 46 47 #include "common.h" 48 49 enum pppoatm_encaps { 50 e_autodetect = PPPOATM_ENCAPS_AUTODETECT, 51 e_vc = PPPOATM_ENCAPS_VC, 52 e_llc = PPPOATM_ENCAPS_LLC, 53 }; 54 55 struct pppoatm_vcc { 56 struct atm_vcc *atmvcc; /* VCC descriptor */ 57 void (*old_push)(struct atm_vcc *, struct sk_buff *); 58 void (*old_pop)(struct atm_vcc *, struct sk_buff *); 59 /* keep old push/pop for detaching */ 60 enum pppoatm_encaps encaps; 61 int flags; /* SC_COMP_PROT - compress protocol */ 62 struct ppp_channel chan; /* interface to generic ppp layer */ 63 struct tasklet_struct wakeup_tasklet; 64 }; 65 66 /* 67 * Header used for LLC Encapsulated PPP (4 bytes) followed by the LCP protocol 68 * ID (0xC021) used in autodetection 69 */ 70 static const unsigned char pppllc[6] = { 0xFE, 0xFE, 0x03, 0xCF, 0xC0, 0x21 }; 71 #define LLC_LEN (4) 72 73 static inline struct pppoatm_vcc *atmvcc_to_pvcc(const struct atm_vcc *atmvcc) 74 { 75 return (struct pppoatm_vcc *) (atmvcc->user_back); 76 } 77 78 static inline struct pppoatm_vcc *chan_to_pvcc(const struct ppp_channel *chan) 79 { 80 return (struct pppoatm_vcc *) (chan->private); 81 } 82 83 /* 84 * We can't do this directly from our _pop handler, since the ppp code 85 * doesn't want to be called in interrupt context, so we do it from 86 * a tasklet 87 */ 88 static void pppoatm_wakeup_sender(unsigned long arg) 89 { 90 ppp_output_wakeup((struct ppp_channel *) arg); 91 } 92 93 /* 94 * This gets called every time the ATM card has finished sending our 95 * skb. The ->old_pop will take care up normal atm flow control, 96 * but we also need to wake up the device if we blocked it 97 */ 98 static void pppoatm_pop(struct atm_vcc *atmvcc, struct sk_buff *skb) 99 { 100 struct pppoatm_vcc *pvcc = atmvcc_to_pvcc(atmvcc); 101 pvcc->old_pop(atmvcc, skb); 102 /* 103 * We don't really always want to do this since it's 104 * really inefficient - it would be much better if we could 105 * test if we had actually throttled the generic layer. 106 * Unfortunately then there would be a nasty SMP race where 107 * we could clear that flag just as we refuse another packet. 108 * For now we do the safe thing. 109 */ 110 tasklet_schedule(&pvcc->wakeup_tasklet); 111 } 112 113 /* 114 * Unbind from PPP - currently we only do this when closing the socket, 115 * but we could put this into an ioctl if need be 116 */ 117 static void pppoatm_unassign_vcc(struct atm_vcc *atmvcc) 118 { 119 struct pppoatm_vcc *pvcc; 120 pvcc = atmvcc_to_pvcc(atmvcc); 121 atmvcc->push = pvcc->old_push; 122 atmvcc->pop = pvcc->old_pop; 123 tasklet_kill(&pvcc->wakeup_tasklet); 124 ppp_unregister_channel(&pvcc->chan); 125 atmvcc->user_back = NULL; 126 kfree(pvcc); 127 /* Gee, I hope we have the big kernel lock here... */ 128 module_put(THIS_MODULE); 129 } 130 131 /* Called when an AAL5 PDU comes in */ 132 static void pppoatm_push(struct atm_vcc *atmvcc, struct sk_buff *skb) 133 { 134 struct pppoatm_vcc *pvcc = atmvcc_to_pvcc(atmvcc); 135 pr_debug("pppoatm push\n"); 136 if (skb == NULL) { /* VCC was closed */ 137 pr_debug("removing ATMPPP VCC %p\n", pvcc); 138 pppoatm_unassign_vcc(atmvcc); 139 atmvcc->push(atmvcc, NULL); /* Pass along bad news */ 140 return; 141 } 142 atm_return(atmvcc, skb->truesize); 143 switch (pvcc->encaps) { 144 case e_llc: 145 if (skb->len < LLC_LEN || 146 memcmp(skb->data, pppllc, LLC_LEN)) 147 goto error; 148 skb_pull(skb, LLC_LEN); 149 break; 150 case e_autodetect: 151 if (pvcc->chan.ppp == NULL) { /* Not bound yet! */ 152 kfree_skb(skb); 153 return; 154 } 155 if (skb->len >= sizeof(pppllc) && 156 !memcmp(skb->data, pppllc, sizeof(pppllc))) { 157 pvcc->encaps = e_llc; 158 skb_pull(skb, LLC_LEN); 159 break; 160 } 161 if (skb->len >= (sizeof(pppllc) - LLC_LEN) && 162 !memcmp(skb->data, &pppllc[LLC_LEN], 163 sizeof(pppllc) - LLC_LEN)) { 164 pvcc->encaps = e_vc; 165 pvcc->chan.mtu += LLC_LEN; 166 break; 167 } 168 pr_debug("Couldn't autodetect yet " 169 "(skb: %02X %02X %02X %02X %02X %02X)\n", 170 skb->data[0], skb->data[1], skb->data[2], 171 skb->data[3], skb->data[4], skb->data[5]); 172 goto error; 173 case e_vc: 174 break; 175 } 176 ppp_input(&pvcc->chan, skb); 177 return; 178 error: 179 kfree_skb(skb); 180 ppp_input_error(&pvcc->chan, 0); 181 } 182 183 /* 184 * Called by the ppp_generic.c to send a packet - returns true if packet 185 * was accepted. If we return false, then it's our job to call 186 * ppp_output_wakeup(chan) when we're feeling more up to it. 187 * Note that in the ENOMEM case (as opposed to the !atm_may_send case) 188 * we should really drop the packet, but the generic layer doesn't 189 * support this yet. We just return 'DROP_PACKET' which we actually define 190 * as success, just to be clear what we're really doing. 191 */ 192 #define DROP_PACKET 1 193 static int pppoatm_send(struct ppp_channel *chan, struct sk_buff *skb) 194 { 195 struct pppoatm_vcc *pvcc = chan_to_pvcc(chan); 196 ATM_SKB(skb)->vcc = pvcc->atmvcc; 197 pr_debug("pppoatm_send (skb=0x%p, vcc=0x%p)\n", skb, pvcc->atmvcc); 198 if (skb->data[0] == '\0' && (pvcc->flags & SC_COMP_PROT)) 199 (void) skb_pull(skb, 1); 200 switch (pvcc->encaps) { /* LLC encapsulation needed */ 201 case e_llc: 202 if (skb_headroom(skb) < LLC_LEN) { 203 struct sk_buff *n; 204 n = skb_realloc_headroom(skb, LLC_LEN); 205 if (n != NULL && 206 !atm_may_send(pvcc->atmvcc, n->truesize)) { 207 kfree_skb(n); 208 goto nospace; 209 } 210 kfree_skb(skb); 211 if ((skb = n) == NULL) 212 return DROP_PACKET; 213 } else if (!atm_may_send(pvcc->atmvcc, skb->truesize)) 214 goto nospace; 215 memcpy(skb_push(skb, LLC_LEN), pppllc, LLC_LEN); 216 break; 217 case e_vc: 218 if (!atm_may_send(pvcc->atmvcc, skb->truesize)) 219 goto nospace; 220 break; 221 case e_autodetect: 222 pr_debug("Trying to send without setting encaps!\n"); 223 kfree_skb(skb); 224 return 1; 225 } 226 227 atomic_add(skb->truesize, &sk_atm(ATM_SKB(skb)->vcc)->sk_wmem_alloc); 228 ATM_SKB(skb)->atm_options = ATM_SKB(skb)->vcc->atm_options; 229 pr_debug("atm_skb(%p)->vcc(%p)->dev(%p)\n", skb, ATM_SKB(skb)->vcc, 230 ATM_SKB(skb)->vcc->dev); 231 return ATM_SKB(skb)->vcc->send(ATM_SKB(skb)->vcc, skb) 232 ? DROP_PACKET : 1; 233 nospace: 234 /* 235 * We don't have space to send this SKB now, but we might have 236 * already applied SC_COMP_PROT compression, so may need to undo 237 */ 238 if ((pvcc->flags & SC_COMP_PROT) && skb_headroom(skb) > 0 && 239 skb->data[-1] == '\0') 240 (void) skb_push(skb, 1); 241 return 0; 242 } 243 244 /* This handles ioctls sent to the /dev/ppp interface */ 245 static int pppoatm_devppp_ioctl(struct ppp_channel *chan, unsigned int cmd, 246 unsigned long arg) 247 { 248 switch (cmd) { 249 case PPPIOCGFLAGS: 250 return put_user(chan_to_pvcc(chan)->flags, (int __user *) arg) 251 ? -EFAULT : 0; 252 case PPPIOCSFLAGS: 253 return get_user(chan_to_pvcc(chan)->flags, (int __user *) arg) 254 ? -EFAULT : 0; 255 } 256 return -ENOTTY; 257 } 258 259 static /*const*/ struct ppp_channel_ops pppoatm_ops = { 260 .start_xmit = pppoatm_send, 261 .ioctl = pppoatm_devppp_ioctl, 262 }; 263 264 static int pppoatm_assign_vcc(struct atm_vcc *atmvcc, void __user *arg) 265 { 266 struct atm_backend_ppp be; 267 struct pppoatm_vcc *pvcc; 268 int err; 269 /* 270 * Each PPPoATM instance has its own tasklet - this is just a 271 * prototypical one used to initialize them 272 */ 273 static const DECLARE_TASKLET(tasklet_proto, pppoatm_wakeup_sender, 0); 274 if (copy_from_user(&be, arg, sizeof be)) 275 return -EFAULT; 276 if (be.encaps != PPPOATM_ENCAPS_AUTODETECT && 277 be.encaps != PPPOATM_ENCAPS_VC && be.encaps != PPPOATM_ENCAPS_LLC) 278 return -EINVAL; 279 pvcc = kzalloc(sizeof(*pvcc), GFP_KERNEL); 280 if (pvcc == NULL) 281 return -ENOMEM; 282 pvcc->atmvcc = atmvcc; 283 pvcc->old_push = atmvcc->push; 284 pvcc->old_pop = atmvcc->pop; 285 pvcc->encaps = (enum pppoatm_encaps) be.encaps; 286 pvcc->chan.private = pvcc; 287 pvcc->chan.ops = &pppoatm_ops; 288 pvcc->chan.mtu = atmvcc->qos.txtp.max_sdu - PPP_HDRLEN - 289 (be.encaps == e_vc ? 0 : LLC_LEN); 290 pvcc->wakeup_tasklet = tasklet_proto; 291 pvcc->wakeup_tasklet.data = (unsigned long) &pvcc->chan; 292 if ((err = ppp_register_channel(&pvcc->chan)) != 0) { 293 kfree(pvcc); 294 return err; 295 } 296 atmvcc->user_back = pvcc; 297 atmvcc->push = pppoatm_push; 298 atmvcc->pop = pppoatm_pop; 299 __module_get(THIS_MODULE); 300 return 0; 301 } 302 303 /* 304 * This handles ioctls actually performed on our vcc - we must return 305 * -ENOIOCTLCMD for any unrecognized ioctl 306 */ 307 static int pppoatm_ioctl(struct socket *sock, unsigned int cmd, 308 unsigned long arg) 309 { 310 struct atm_vcc *atmvcc = ATM_SD(sock); 311 void __user *argp = (void __user *)arg; 312 313 if (cmd != ATM_SETBACKEND && atmvcc->push != pppoatm_push) 314 return -ENOIOCTLCMD; 315 switch (cmd) { 316 case ATM_SETBACKEND: { 317 atm_backend_t b; 318 if (get_user(b, (atm_backend_t __user *) argp)) 319 return -EFAULT; 320 if (b != ATM_BACKEND_PPP) 321 return -ENOIOCTLCMD; 322 if (!capable(CAP_NET_ADMIN)) 323 return -EPERM; 324 return pppoatm_assign_vcc(atmvcc, argp); 325 } 326 case PPPIOCGCHAN: 327 return put_user(ppp_channel_index(&atmvcc_to_pvcc(atmvcc)-> 328 chan), (int __user *) argp) ? -EFAULT : 0; 329 case PPPIOCGUNIT: 330 return put_user(ppp_unit_number(&atmvcc_to_pvcc(atmvcc)-> 331 chan), (int __user *) argp) ? -EFAULT : 0; 332 } 333 return -ENOIOCTLCMD; 334 } 335 336 static struct atm_ioctl pppoatm_ioctl_ops = { 337 .owner = THIS_MODULE, 338 .ioctl = pppoatm_ioctl, 339 }; 340 341 static int __init pppoatm_init(void) 342 { 343 register_atm_ioctl(&pppoatm_ioctl_ops); 344 return 0; 345 } 346 347 static void __exit pppoatm_exit(void) 348 { 349 deregister_atm_ioctl(&pppoatm_ioctl_ops); 350 } 351 352 module_init(pppoatm_init); 353 module_exit(pppoatm_exit); 354 355 MODULE_AUTHOR("Mitchell Blank Jr <mitch@sfgoth.com>"); 356 MODULE_DESCRIPTION("RFC2364 PPP over ATM/AAL5"); 357 MODULE_LICENSE("GPL"); 358