diff options
Diffstat (limited to 'net/atm/pppoatm.c')
| -rw-r--r-- | net/atm/pppoatm.c | 499 |
1 files changed, 499 insertions, 0 deletions
diff --git a/net/atm/pppoatm.c b/net/atm/pppoatm.c new file mode 100644 index 000000000..d84227d75 --- /dev/null +++ b/net/atm/pppoatm.c @@ -0,0 +1,499 @@ +/* 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 *); + void (*old_release_cb)(struct atm_vcc *); + struct module *old_owner; + /* 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); +} + +static void pppoatm_release_cb(struct atm_vcc *atmvcc) +{ + struct pppoatm_vcc *pvcc = atmvcc_to_pvcc(atmvcc); + + /* + * As in pppoatm_pop(), it's safe to clear the BLOCKED bit here because + * the wakeup *can't* race with pppoatm_send(). They both hold the PPP + * channel's ->downl lock. And the potential race with *setting* it, + * which leads to the double-check dance in pppoatm_may_send(), doesn't + * exist here. In the sock_owned_by_user() case in pppoatm_send(), we + * set the BLOCKED bit while the socket is still locked. We know that + * ->release_cb() can't be called until that's done. + */ + if (test_and_clear_bit(BLOCKED, &pvcc->blocked)) + tasklet_schedule(&pvcc->wakeup_tasklet); + if (pvcc->old_release_cb) + pvcc->old_release_cb(atmvcc); +} +/* + * 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; + atmvcc->release_cb = pvcc->old_release_cb; + tasklet_kill(&pvcc->wakeup_tasklet); + ppp_unregister_channel(&pvcc->chan); + atmvcc->user_back = NULL; + kfree(pvcc); +} + +/* 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 */ + struct module *module; + + pr_debug("removing ATMPPP VCC %p\n", pvcc); + module = pvcc->old_owner; + pppoatm_unassign_vcc(atmvcc); + atmvcc->push(atmvcc, NULL); /* Pass along bad news */ + module_put(module); + 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 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(&pvcc->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_atomic(). + */ + 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); + struct atm_vcc *vcc; + int ret; + + 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); + + vcc = ATM_SKB(skb)->vcc; + bh_lock_sock(sk_atm(vcc)); + if (sock_owned_by_user(sk_atm(vcc))) { + /* + * Needs to happen (and be flushed, hence test_and_) before we unlock + * the socket. It needs to be seen by the time our ->release_cb gets + * called. + */ + test_and_set_bit(BLOCKED, &pvcc->blocked); + goto nospace; + } + if (test_bit(ATM_VF_RELEASED, &vcc->flags) || + test_bit(ATM_VF_CLOSE, &vcc->flags) || + !test_bit(ATM_VF_READY, &vcc->flags)) { + bh_unlock_sock(sk_atm(vcc)); + kfree_skb(skb); + return DROP_PACKET; + } + + 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) { + bh_unlock_sock(sk_atm(vcc)); + 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: + bh_unlock_sock(sk_atm(vcc)); + pr_debug("Trying to send without setting encaps!\n"); + kfree_skb(skb); + return 1; + } + + atm_account_tx(vcc, skb); + pr_debug("atm_skb(%p)->vcc(%p)->dev(%p)\n", + skb, ATM_SKB(skb)->vcc, ATM_SKB(skb)->vcc->dev); + ret = ATM_SKB(skb)->vcc->send(ATM_SKB(skb)->vcc, skb) + ? DROP_PACKET : 1; + bh_unlock_sock(sk_atm(vcc)); + return ret; +nospace: + bh_unlock_sock(sk_atm(vcc)); + /* + * 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->old_owner = atmvcc->owner; + pvcc->old_release_cb = atmvcc->release_cb; + 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; + atmvcc->release_cb = pppoatm_release_cb; + __module_get(THIS_MODULE); + atmvcc->owner = 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; + if (sock->state != SS_CONNECTED) + return -EINVAL; + 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"); |