--- /dev/null
+/* 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_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_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;
+ }
+
+ 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);
+ 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");
Code Review / kvmfornfv.git / blobdiff