/* net/atm/pppoatm.c - RFC2364 PPP over ATM/AAL5 */ /* Copyright 1999-2000 by Mitchell Blank Jr */ /* Based on clip.c; 1995-1999 by Werner Almesberger, EPFL LRC/ICA */ /* And on ppp_async.c; Copyright 1999 Paul Mackerras */ /* And help from Jens Axboe */ /* * This program is free software; you can redistribute it and/or * modify it under the terms of the GNU General Public License * as published by the Free Software Foundation; either version * 2 of the License, or (at your option) any later version. * * This driver provides the encapsulation and framing for sending * and receiving PPP frames in ATM AAL5 PDUs. */ /* * One shortcoming of this driver is that it does not comply with * section 8 of RFC2364 - we are supposed to detect a change * in encapsulation and immediately abort the connection (in order * to avoid a black-hole being created if our peer loses state * and changes encapsulation unilaterally. However, since the * ppp_generic layer actually does the decapsulation, we need * a way of notifying it when we _think_ there might be a problem) * There's two cases: * 1. LLC-encapsulation was missing when it was enabled. In * this case, we should tell the upper layer "tear down * this session if this skb looks ok to you" * 2. LLC-encapsulation was present when it was disabled. Then * we need to tell the upper layer "this packet may be * ok, but if its in error tear down the session" * These hooks are not yet available in ppp_generic */ #define pr_fmt(fmt) KBUILD_MODNAME ":%s: " fmt, __func__ #include <linux/module.h> #include <linux/init.h> #include <linux/interrupt.h> #include <linux/skbuff.h> #include <linux/slab.h> #include <linux/atm.h> #include <linux/atmdev.h> #include <linux/capability.h> #include <linux/ppp_defs.h> #include <linux/ppp-ioctl.h> #include <linux/ppp_channel.h> #include <linux/atmppp.h> #include "common.h" enum pppoatm_encaps { e_autodetect = PPPOATM_ENCAPS_AUTODETECT, e_vc = PPPOATM_ENCAPS_VC, e_llc = PPPOATM_ENCAPS_LLC, }; struct pppoatm_vcc { struct atm_vcc *atmvcc; /* VCC descriptor */ void (*old_push)(struct atm_vcc *, struct sk_buff *); void (*old_pop)(struct atm_vcc *, struct sk_buff *); /* keep old push/pop for detaching */ enum pppoatm_encaps encaps; atomic_t inflight; unsigned long blocked; int flags; /* SC_COMP_PROT - compress protocol */ struct ppp_channel chan; /* interface to generic ppp layer */ struct tasklet_struct wakeup_tasklet; }; /* * We want to allow two packets in the queue. The one that's currently in * flight, and *one* queued up ready for the ATM device to send immediately * from its TX done IRQ. We want to be able to use atomic_inc_not_zero(), so * inflight == -2 represents an empty queue, -1 one packet, and zero means * there are two packets in the queue. */ #define NONE_INFLIGHT -2 #define BLOCKED 0 /* * Header used for LLC Encapsulated PPP (4 bytes) followed by the LCP protocol * ID (0xC021) used in autodetection */ static const unsigned char pppllc[6] = { 0xFE, 0xFE, 0x03, 0xCF, 0xC0, 0x21 }; #define LLC_LEN (4) static inline struct pppoatm_vcc *atmvcc_to_pvcc(const struct atm_vcc *atmvcc) { return (struct pppoatm_vcc *) (atmvcc->user_back); } static inline struct pppoatm_vcc *chan_to_pvcc(const struct ppp_channel *chan) { return (struct pppoatm_vcc *) (chan->private); } /* * We can't do this directly from our _pop handler, since the ppp code * doesn't want to be called in interrupt context, so we do it from * a tasklet */ static void pppoatm_wakeup_sender(unsigned long arg) { ppp_output_wakeup((struct ppp_channel *) arg); } /* * This gets called every time the ATM card has finished sending our * skb. The ->old_pop will take care up normal atm flow control, * but we also need to wake up the device if we blocked it */ static void pppoatm_pop(struct atm_vcc *atmvcc, struct sk_buff *skb) { struct pppoatm_vcc *pvcc = atmvcc_to_pvcc(atmvcc); pvcc->old_pop(atmvcc, skb); atomic_dec(&pvcc->inflight); /* * We always used to run the wakeup tasklet unconditionally here, for * fear of race conditions where we clear the BLOCKED flag just as we * refuse another packet in pppoatm_send(). This was quite inefficient. * * In fact it's OK. The PPP core will only ever call pppoatm_send() * while holding the channel->downl lock. And ppp_output_wakeup() as * called by the tasklet will *also* grab that lock. So even if another * CPU is in pppoatm_send() right now, the tasklet isn't going to race * with it. The wakeup *will* happen after the other CPU is safely out * of pppoatm_send() again. * * So if the CPU in pppoatm_send() has already set the BLOCKED bit and * it about to return, that's fine. We trigger a wakeup which will * happen later. And if the CPU in pppoatm_send() *hasn't* set the * BLOCKED bit yet, that's fine too because of the double check in * pppoatm_may_send() which is commented there. */ if (test_and_clear_bit(BLOCKED, &pvcc->blocked)) tasklet_schedule(&pvcc->wakeup_tasklet); } /* * Unbind from PPP - currently we only do this when closing the socket, * but we could put this into an ioctl if need be */ static void pppoatm_unassign_vcc(struct atm_vcc *atmvcc) { struct pppoatm_vcc *pvcc; pvcc = atmvcc_to_pvcc(atmvcc); atmvcc->push = pvcc->old_push; atmvcc->pop = pvcc->old_pop; tasklet_kill(&pvcc->wakeup_tasklet); ppp_unregister_channel(&pvcc->chan); atmvcc->user_back = NULL; kfree(pvcc); /* Gee, I hope we have the big kernel lock here... */ module_put(THIS_MODULE); } /* Called when an AAL5 PDU comes in */ static void pppoatm_push(struct atm_vcc *atmvcc, struct sk_buff *skb) { struct pppoatm_vcc *pvcc = atmvcc_to_pvcc(atmvcc); pr_debug("\n"); if (skb == NULL) { /* VCC was closed */ pr_debug("removing ATMPPP VCC %p\n", pvcc); pppoatm_unassign_vcc(atmvcc); atmvcc->push(atmvcc, NULL); /* Pass along bad news */ return; } atm_return(atmvcc, skb->truesize); switch (pvcc->encaps) { case e_llc: if (skb->len < LLC_LEN || memcmp(skb->data, pppllc, LLC_LEN)) goto error; skb_pull(skb, LLC_LEN); break; case e_autodetect: if (pvcc->chan.ppp == NULL) { /* Not bound yet! */ kfree_skb(skb); return; } if (skb->len >= sizeof(pppllc) && !memcmp(skb->data, pppllc, sizeof(pppllc))) { pvcc->encaps = e_llc; skb_pull(skb, LLC_LEN); break; } if (skb->len >= (sizeof(pppllc) - LLC_LEN) && !memcmp(skb->data, &pppllc[LLC_LEN], sizeof(pppllc) - LLC_LEN)) { pvcc->encaps = e_vc; pvcc->chan.mtu += LLC_LEN; break; } pr_debug("Couldn't autodetect yet (skb: %02X %02X %02X %02X %02X %02X)\n", skb->data[0], skb->data[1], skb->data[2], skb->data[3], skb->data[4], skb->data[5]); goto error; case e_vc: break; } ppp_input(&pvcc->chan, skb); return; error: kfree_skb(skb); ppp_input_error(&pvcc->chan, 0); } static inline int pppoatm_may_send(struct pppoatm_vcc *pvcc, int size) { /* * It's not clear that we need to bother with using atm_may_send() * to check we don't exceed sk->sk_sndbuf. If userspace sets a * value of sk_sndbuf which is lower than the MTU, we're going to * block for ever. But the code always did that before we introduced * the packet count limit, so... */ if (atm_may_send(pvcc->atmvcc, size) && atomic_inc_not_zero_hint(&pvcc->inflight, NONE_INFLIGHT)) return 1; /* * We use test_and_set_bit() rather than set_bit() here because * we need to ensure there's a memory barrier after it. The bit * *must* be set before we do the atomic_inc() on pvcc->inflight. * There's no smp_mb__after_set_bit(), so it's this or abuse * smp_mb__after_clear_bit(). */ test_and_set_bit(BLOCKED, &pvcc->blocked); /* * We may have raced with pppoatm_pop(). If it ran for the * last packet in the queue, *just* before we set the BLOCKED * bit, then it might never run again and the channel could * remain permanently blocked. Cope with that race by checking * *again*. If it did run in that window, we'll have space on * the queue now and can return success. It's harmless to leave * the BLOCKED flag set, since it's only used as a trigger to * run the wakeup tasklet. Another wakeup will never hurt. * If pppoatm_pop() is running but hasn't got as far as making * space on the queue yet, then it hasn't checked the BLOCKED * flag yet either, so we're safe in that case too. It'll issue * an "immediate" wakeup... where "immediate" actually involves * taking the PPP channel's ->downl lock, which is held by the * code path that calls pppoatm_send(), and is thus going to * wait for us to finish. */ if (atm_may_send(pvcc->atmvcc, size) && atomic_inc_not_zero(&pvcc->inflight)) return 1; return 0; } /* * Called by the ppp_generic.c to send a packet - returns true if packet * was accepted. If we return false, then it's our job to call * ppp_output_wakeup(chan) when we're feeling more up to it. * Note that in the ENOMEM case (as opposed to the !atm_may_send case) * we should really drop the packet, but the generic layer doesn't * support this yet. We just return 'DROP_PACKET' which we actually define * as success, just to be clear what we're really doing. */ #define DROP_PACKET 1 static int pppoatm_send(struct ppp_channel *chan, struct sk_buff *skb) { struct pppoatm_vcc *pvcc = chan_to_pvcc(chan); ATM_SKB(skb)->vcc = pvcc->atmvcc; pr_debug("(skb=0x%p, vcc=0x%p)\n", skb, pvcc->atmvcc); if (skb->data[0] == '\0' && (pvcc->flags & SC_COMP_PROT)) (void) skb_pull(skb, 1); switch (pvcc->encaps) { /* LLC encapsulation needed */ case e_llc: if (skb_headroom(skb) < LLC_LEN) { struct sk_buff *n; n = skb_realloc_headroom(skb, LLC_LEN); if (n != NULL && !pppoatm_may_send(pvcc, n->truesize)) { kfree_skb(n); goto nospace; } consume_skb(skb); skb = n; if (skb == NULL) return DROP_PACKET; } else if (!pppoatm_may_send(pvcc, skb->truesize)) goto nospace; memcpy(skb_push(skb, LLC_LEN), pppllc, LLC_LEN); break; case e_vc: if (!pppoatm_may_send(pvcc, skb->truesize)) goto nospace; break; case e_autodetect: pr_debug("Trying to send without setting encaps!\n"); kfree_skb(skb); return 1; } atomic_add(skb->truesize, &sk_atm(ATM_SKB(skb)->vcc)->sk_wmem_alloc); ATM_SKB(skb)->atm_options = ATM_SKB(skb)->vcc->atm_options; pr_debug("atm_skb(%p)->vcc(%p)->dev(%p)\n", skb, ATM_SKB(skb)->vcc, ATM_SKB(skb)->vcc->dev); return ATM_SKB(skb)->vcc->send(ATM_SKB(skb)->vcc, skb) ? DROP_PACKET : 1; nospace: /* * We don't have space to send this SKB now, but we might have * already applied SC_COMP_PROT compression, so may need to undo */ if ((pvcc->flags & SC_COMP_PROT) && skb_headroom(skb) > 0 && skb->data[-1] == '\0') (void) skb_push(skb, 1); return 0; } /* This handles ioctls sent to the /dev/ppp interface */ static int pppoatm_devppp_ioctl(struct ppp_channel *chan, unsigned int cmd, unsigned long arg) { switch (cmd) { case PPPIOCGFLAGS: return put_user(chan_to_pvcc(chan)->flags, (int __user *) arg) ? -EFAULT : 0; case PPPIOCSFLAGS: return get_user(chan_to_pvcc(chan)->flags, (int __user *) arg) ? -EFAULT : 0; } return -ENOTTY; } static const struct ppp_channel_ops pppoatm_ops = { .start_xmit = pppoatm_send, .ioctl = pppoatm_devppp_ioctl, }; static int pppoatm_assign_vcc(struct atm_vcc *atmvcc, void __user *arg) { struct atm_backend_ppp be; struct pppoatm_vcc *pvcc; int err; /* * Each PPPoATM instance has its own tasklet - this is just a * prototypical one used to initialize them */ static const DECLARE_TASKLET(tasklet_proto, pppoatm_wakeup_sender, 0); if (copy_from_user(&be, arg, sizeof be)) return -EFAULT; if (be.encaps != PPPOATM_ENCAPS_AUTODETECT && be.encaps != PPPOATM_ENCAPS_VC && be.encaps != PPPOATM_ENCAPS_LLC) return -EINVAL; pvcc = kzalloc(sizeof(*pvcc), GFP_KERNEL); if (pvcc == NULL) return -ENOMEM; pvcc->atmvcc = atmvcc; /* Maximum is zero, so that we can use atomic_inc_not_zero() */ atomic_set(&pvcc->inflight, NONE_INFLIGHT); pvcc->old_push = atmvcc->push; pvcc->old_pop = atmvcc->pop; pvcc->encaps = (enum pppoatm_encaps) be.encaps; pvcc->chan.private = pvcc; pvcc->chan.ops = &pppoatm_ops; pvcc->chan.mtu = atmvcc->qos.txtp.max_sdu - PPP_HDRLEN - (be.encaps == e_vc ? 0 : LLC_LEN); pvcc->wakeup_tasklet = tasklet_proto; pvcc->wakeup_tasklet.data = (unsigned long) &pvcc->chan; err = ppp_register_channel(&pvcc->chan); if (err != 0) { kfree(pvcc); return err; } atmvcc->user_back = pvcc; atmvcc->push = pppoatm_push; atmvcc->pop = pppoatm_pop; __module_get(THIS_MODULE); /* re-process everything received between connection setup and backend setup */ vcc_process_recv_queue(atmvcc); return 0; } /* * This handles ioctls actually performed on our vcc - we must return * -ENOIOCTLCMD for any unrecognized ioctl */ static int pppoatm_ioctl(struct socket *sock, unsigned int cmd, unsigned long arg) { struct atm_vcc *atmvcc = ATM_SD(sock); void __user *argp = (void __user *)arg; if (cmd != ATM_SETBACKEND && atmvcc->push != pppoatm_push) return -ENOIOCTLCMD; switch (cmd) { case ATM_SETBACKEND: { atm_backend_t b; if (get_user(b, (atm_backend_t __user *) argp)) return -EFAULT; if (b != ATM_BACKEND_PPP) return -ENOIOCTLCMD; if (!capable(CAP_NET_ADMIN)) return -EPERM; return pppoatm_assign_vcc(atmvcc, argp); } case PPPIOCGCHAN: return put_user(ppp_channel_index(&atmvcc_to_pvcc(atmvcc)-> chan), (int __user *) argp) ? -EFAULT : 0; case PPPIOCGUNIT: return put_user(ppp_unit_number(&atmvcc_to_pvcc(atmvcc)-> chan), (int __user *) argp) ? -EFAULT : 0; } return -ENOIOCTLCMD; } static struct atm_ioctl pppoatm_ioctl_ops = { .owner = THIS_MODULE, .ioctl = pppoatm_ioctl, }; static int __init pppoatm_init(void) { register_atm_ioctl(&pppoatm_ioctl_ops); return 0; } static void __exit pppoatm_exit(void) { deregister_atm_ioctl(&pppoatm_ioctl_ops); } module_init(pppoatm_init); module_exit(pppoatm_exit); MODULE_AUTHOR("Mitchell Blank Jr <mitch@sfgoth.com>"); MODULE_DESCRIPTION("RFC2364 PPP over ATM/AAL5"); MODULE_LICENSE("GPL");