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/* 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

 */

#include <linux/module.h>

#include <linux/config.h>

#include <linux/init.h>

#include <linux/skbuff.h>

#include <linux/atm.h>

#include <linux/atmdev.h>

#include <linux/ppp_defs.h>

#include <linux/if_ppp.h>

#include <linux/ppp_channel.h>

#include <linux/atmppp.h>

#include "common.h"

#if 0

#define DPRINTK(format, args...) \

        printk(KERN_DEBUG "pppoatm: " format, ##args)

#else

#define DPRINTK(format, args...)

#endif

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;

        int flags;                      /* SC_COMP_PROT - compress protocol */

        struct ppp_channel chan;        /* interface to generic ppp layer */

        struct tasklet_struct wakeup_tasklet;

};

/*

 * 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);

        /*

         * We don't really always want to do this since it's

         * really inefficient - it would be much better if we could

         * test if we had actually throttled the generic layer.

         * Unfortunately then there would be a nasty SMP race where

         * we could clear that flag just as we refuse another packet.

         * For now we do the safe thing.

         */

        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... */

        MOD_DEC_USE_COUNT;

}

/* 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);

        DPRINTK("pppoatm push\n");

        if (skb == NULL) {                      /* VCC was closed */

                DPRINTK("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;

                }

                DPRINTK("(unit %d): Couldn't autodetect yet "

                    "(skb: %02X %02X %02X %02X %02X %02X)\n",

                    pvcc->chan.unit,

                    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);

}

/*

 * 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;

        DPRINTK("(unit %d): pppoatm_send (skb=0x%p, vcc=0x%p)\n",

            pvcc->chan.unit, 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 &&

                            !atm_may_send(pvcc->atmvcc, n->truesize)) {

                                kfree_skb(n);

                                goto nospace;

                        }

                        kfree_skb(skb);

                        if ((skb = n) == NULL)

                                return DROP_PACKET;

                } else if (!atm_may_send(pvcc->atmvcc, skb->truesize))

                        goto nospace;

                memcpy(skb_push(skb, LLC_LEN), pppllc, LLC_LEN);

                break;

        case e_vc:

                if (!atm_may_send(pvcc->atmvcc, skb->truesize))

                        goto nospace;

                break;

        case e_autodetect:

                DPRINTK("(unit %d): Trying to send without setting encaps!\n",

                    pvcc->chan.unit);

                kfree_skb(skb);

                return 1;

        }

        atomic_add(skb->truesize, &ATM_SKB(skb)->vcc->sk->wmem_alloc);

        ATM_SKB(skb)->atm_options = ATM_SKB(skb)->vcc->atm_options;

        DPRINTK("(unit %d): atm_skb(%p)->vcc(%p)->dev(%p)\n",

            pvcc->chan.unit, 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 *) arg)

                    ? -EFAULT : 0;

        case PPPIOCSFLAGS:

                return get_user(chan_to_pvcc(chan)->flags, (int *) 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, unsigned long 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, (void *) arg, sizeof be))

                return -EFAULT;

        if (be.encaps != PPPOATM_ENCAPS_AUTODETECT &&

            be.encaps != PPPOATM_ENCAPS_VC && be.encaps != PPPOATM_ENCAPS_LLC)

                return -EINVAL;

        MOD_INC_USE_COUNT;

        pvcc = kmalloc(sizeof(*pvcc), GFP_KERNEL);

        if (pvcc == NULL) {

                MOD_DEC_USE_COUNT;

                return -ENOMEM;

        }

        memset(pvcc, 0, sizeof(*pvcc));

        pvcc->atmvcc = atmvcc;

        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;

        if ((err = ppp_register_channel(&pvcc->chan)) != 0) {

                kfree(pvcc);

                return err;

        }

        atmvcc->user_back = pvcc;

        atmvcc->push = pppoatm_push;

        atmvcc->pop = pppoatm_pop;

        return 0;

}

/*

 * This handles ioctls actually performed on our vcc - we must return

 * -ENOIOCTLCMD for any unrecognized ioctl

 */

static int pppoatm_ioctl(struct atm_vcc *atmvcc, unsigned int cmd,

        unsigned long 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 *) arg))

                        return -EFAULT;

                if (b != ATM_BACKEND_PPP)

                        return -ENOIOCTLCMD;

                if (!capable(CAP_NET_ADMIN))

                        return -EPERM;

                return pppoatm_assign_vcc(atmvcc, arg);

                }

        case PPPIOCGCHAN:

                return put_user(ppp_channel_index(&atmvcc_to_pvcc(atmvcc)->

                    chan), (int *) arg) ? -EFAULT : 0;

        case PPPIOCGUNIT:

                return put_user(ppp_unit_number(&atmvcc_to_pvcc(atmvcc)->

                    chan), (int *) arg) ? -EFAULT : 0;

        }

        return -ENOIOCTLCMD;

}

/* the following avoids some spurious warnings from the compiler */

#define UNUSED __attribute__((unused))

static int __init UNUSED pppoatm_init(void)

{

        pppoatm_ioctl_set(pppoatm_ioctl);

        return 0;

}

static void __exit UNUSED pppoatm_exit(void)

{

        pppoatm_ioctl_set(NULL);

}

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");