[linux-block.git] / drivers / net / ppp / ppp_synctty.c

// SPDX-License-Identifier: GPL-2.0-or-later
/*
 * PPP synchronous tty channel driver for Linux.
 *
 * This is a ppp channel driver that can be used with tty device drivers
 * that are frame oriented, such as synchronous HDLC devices.
 *
 * Complete PPP frames without encoding/decoding are exchanged between
 * the channel driver and the device driver.
 *
 * The async map IOCTL codes are implemented to keep the user mode
 * applications happy if they call them. Synchronous PPP does not use
 * the async maps.
 *
 * Copyright 1999 Paul Mackerras.
 *
 * Also touched by the grubby hands of Paul Fulghum paulkf@microgate.com
 *
 * This driver provides the encapsulation and framing for sending
 * and receiving PPP frames over sync serial lines.  It relies on
 * the generic PPP layer to give it frames to send and to process
 * received frames.  It implements the PPP line discipline.
 *
 * Part of the code in this driver was inspired by the old async-only
 * PPP driver, written by Michael Callahan and Al Longyear, and
 * subsequently hacked by Paul Mackerras.
 *
 * ==FILEVERSION 20040616==
 */

#include <linux/module.h>
#include <linux/kernel.h>
#include <linux/skbuff.h>
#include <linux/tty.h>
#include <linux/netdevice.h>
#include <linux/poll.h>
#include <linux/ppp_defs.h>
#include <linux/ppp-ioctl.h>
#include <linux/ppp_channel.h>
#include <linux/spinlock.h>
#include <linux/completion.h>
#include <linux/init.h>
#include <linux/interrupt.h>
#include <linux/slab.h>
#include <linux/refcount.h>
#include <asm/unaligned.h>
#include <linux/uaccess.h>

#define PPP_VERSION	"2.4.2"

/* Structure for storing local state. */
struct syncppp {
	struct tty_struct *tty;
	unsigned int	flags;
	unsigned int	rbits;
	int		mru;
	spinlock_t	xmit_lock;
	spinlock_t	recv_lock;
	unsigned long	xmit_flags;
	u32		xaccm[8];
	u32		raccm;
	unsigned int	bytes_sent;
	unsigned int	bytes_rcvd;

	struct sk_buff	*tpkt;
	unsigned long	last_xmit;

	struct sk_buff_head rqueue;

	struct tasklet_struct tsk;

	refcount_t	refcnt;
	struct completion dead_cmp;
	struct ppp_channel chan;	/* interface to generic ppp layer */
};

/* Bit numbers in xmit_flags */
#define XMIT_WAKEUP	0
#define XMIT_FULL	1

/* Bits in rbits */
#define SC_RCV_BITS	(SC_RCV_B7_1|SC_RCV_B7_0|SC_RCV_ODDP|SC_RCV_EVNP)

#define PPPSYNC_MAX_RQLEN	32	/* arbitrary */

/*
 * Prototypes.
 */
static struct sk_buff* ppp_sync_txmunge(struct syncppp *ap, struct sk_buff *);
static int ppp_sync_send(struct ppp_channel *chan, struct sk_buff *skb);
static int ppp_sync_ioctl(struct ppp_channel *chan, unsigned int cmd,
			  unsigned long arg);
static void ppp_sync_process(struct tasklet_struct *t);
static int ppp_sync_push(struct syncppp *ap);
static void ppp_sync_flush_output(struct syncppp *ap);
static void ppp_sync_input(struct syncppp *ap, const unsigned char *buf,
			   const char *flags, int count);

static const struct ppp_channel_ops sync_ops = {
	.start_xmit = ppp_sync_send,
	.ioctl      = ppp_sync_ioctl,
};

/*
 * Utility procedure to print a buffer in hex/ascii
 */
static void
ppp_print_buffer (const char *name, const __u8 *buf, int count)
{
	if (name != NULL)
		printk(KERN_DEBUG "ppp_synctty: %s, count = %d\n", name, count);

	print_hex_dump_bytes("", DUMP_PREFIX_NONE, buf, count);
}


/*
 * Routines implementing the synchronous PPP line discipline.
 */

/*
 * We have a potential race on dereferencing tty->disc_data,
 * because the tty layer provides no locking at all - thus one
 * cpu could be running ppp_synctty_receive while another
 * calls ppp_synctty_close, which zeroes tty->disc_data and
 * frees the memory that ppp_synctty_receive is using.  The best
 * way to fix this is to use a rwlock in the tty struct, but for now
 * we use a single global rwlock for all ttys in ppp line discipline.
 *
 * FIXME: Fixed in tty_io nowadays.
 */
static DEFINE_RWLOCK(disc_data_lock);

static struct syncppp *sp_get(struct tty_struct *tty)
{
	struct syncppp *ap;

	read_lock(&disc_data_lock);
	ap = tty->disc_data;
	if (ap != NULL)
		refcount_inc(&ap->refcnt);
	read_unlock(&disc_data_lock);
	return ap;
}

static void sp_put(struct syncppp *ap)
{
	if (refcount_dec_and_test(&ap->refcnt))
		complete(&ap->dead_cmp);
}

/*
 * Called when a tty is put into sync-PPP line discipline.
 */
static int
ppp_sync_open(struct tty_struct *tty)
{
	struct syncppp *ap;
	int err;
	int speed;

	if (tty->ops->write == NULL)
		return -EOPNOTSUPP;

	ap = kzalloc(sizeof(*ap), GFP_KERNEL);
	err = -ENOMEM;
	if (!ap)
		goto out;

	/* initialize the syncppp structure */
	ap->tty = tty;
	ap->mru = PPP_MRU;
	spin_lock_init(&ap->xmit_lock);
	spin_lock_init(&ap->recv_lock);
	ap->xaccm[0] = ~0U;
	ap->xaccm[3] = 0x60000000U;
	ap->raccm = ~0U;

	skb_queue_head_init(&ap->rqueue);
	tasklet_setup(&ap->tsk, ppp_sync_process);

	refcount_set(&ap->refcnt, 1);
	init_completion(&ap->dead_cmp);

	ap->chan.private = ap;
	ap->chan.ops = &sync_ops;
	ap->chan.mtu = PPP_MRU;
	ap->chan.hdrlen = 2;	/* for A/C bytes */
	speed = tty_get_baud_rate(tty);
	ap->chan.speed = speed;
	err = ppp_register_channel(&ap->chan);
	if (err)
		goto out_free;

	tty->disc_data = ap;
	tty->receive_room = 65536;
	return 0;

 out_free:
	kfree(ap);
 out:
	return err;
}

/*
 * Called when the tty is put into another line discipline
 * or it hangs up.  We have to wait for any cpu currently
 * executing in any of the other ppp_synctty_* routines to
 * finish before we can call ppp_unregister_channel and free
 * the syncppp struct.  This routine must be called from
 * process context, not interrupt or softirq context.
 */
static void
ppp_sync_close(struct tty_struct *tty)
{
	struct syncppp *ap;

	write_lock_irq(&disc_data_lock);
	ap = tty->disc_data;
	tty->disc_data = NULL;
	write_unlock_irq(&disc_data_lock);
	if (!ap)
		return;

	/*
	 * We have now ensured that nobody can start using ap from now
	 * on, but we have to wait for all existing users to finish.
	 * Note that ppp_unregister_channel ensures that no calls to
	 * our channel ops (i.e. ppp_sync_send/ioctl) are in progress
	 * by the time it returns.
	 */
	if (!refcount_dec_and_test(&ap->refcnt))
		wait_for_completion(&ap->dead_cmp);
	tasklet_kill(&ap->tsk);

	ppp_unregister_channel(&ap->chan);
	skb_queue_purge(&ap->rqueue);
	kfree_skb(ap->tpkt);
	kfree(ap);
}

/*
 * Called on tty hangup in process context.
 *
 * Wait for I/O to driver to complete and unregister PPP channel.
 * This is already done by the close routine, so just call that.
 */
static int ppp_sync_hangup(struct tty_struct *tty)
{
	ppp_sync_close(tty);
	return 0;
}

/*
 * Read does nothing - no data is ever available this way.
 * Pppd reads and writes packets via /dev/ppp instead.
 */
static ssize_t
ppp_sync_read(struct tty_struct *tty, struct file *file,
	      unsigned char *buf, size_t count,
	      void **cookie, unsigned long offset)
{
	return -EAGAIN;
}

/*
 * Write on the tty does nothing, the packets all come in
 * from the ppp generic stuff.
 */
static ssize_t
ppp_sync_write(struct tty_struct *tty, struct file *file,
		const unsigned char *buf, size_t count)
{
	return -EAGAIN;
}

static int
ppp_synctty_ioctl(struct tty_struct *tty, struct file *file,
		  unsigned int cmd, unsigned long arg)
{
	struct syncppp *ap = sp_get(tty);
	int __user *p = (int __user *)arg;
	int err, val;

	if (!ap)
		return -ENXIO;
	err = -EFAULT;
	switch (cmd) {
	case PPPIOCGCHAN:
		err = -EFAULT;
		if (put_user(ppp_channel_index(&ap->chan), p))
			break;
		err = 0;
		break;

	case PPPIOCGUNIT:
		err = -EFAULT;
		if (put_user(ppp_unit_number(&ap->chan), p))
			break;
		err = 0;
		break;

	case TCFLSH:
		/* flush our buffers and the serial port's buffer */
		if (arg == TCIOFLUSH || arg == TCOFLUSH)
			ppp_sync_flush_output(ap);
		err = n_tty_ioctl_helper(tty, file, cmd, arg);
		break;

	case FIONREAD:
		val = 0;
		if (put_user(val, p))
			break;
		err = 0;
		break;

	default:
		err = tty_mode_ioctl(tty, file, cmd, arg);
		break;
	}

	sp_put(ap);
	return err;
}

/* No kernel lock - fine */
static __poll_t
ppp_sync_poll(struct tty_struct *tty, struct file *file, poll_table *wait)
{
	return 0;
}

/* May sleep, don't call from interrupt level or with interrupts disabled */
static void
ppp_sync_receive(struct tty_struct *tty, const unsigned char *buf,
		  const char *cflags, int count)
{
	struct syncppp *ap = sp_get(tty);
	unsigned long flags;

	if (!ap)
		return;
	spin_lock_irqsave(&ap->recv_lock, flags);
	ppp_sync_input(ap, buf, cflags, count);
	spin_unlock_irqrestore(&ap->recv_lock, flags);
	if (!skb_queue_empty(&ap->rqueue))
		tasklet_schedule(&ap->tsk);
	sp_put(ap);
	tty_unthrottle(tty);
}

static void
ppp_sync_wakeup(struct tty_struct *tty)
{
	struct syncppp *ap = sp_get(tty);

	clear_bit(TTY_DO_WRITE_WAKEUP, &tty->flags);
	if (!ap)
		return;
	set_bit(XMIT_WAKEUP, &ap->xmit_flags);
	tasklet_schedule(&ap->tsk);
	sp_put(ap);
}


static struct tty_ldisc_ops ppp_sync_ldisc = {
	.owner	= THIS_MODULE,
	.name	= "pppsync",
	.open	= ppp_sync_open,
	.close	= ppp_sync_close,
	.hangup	= ppp_sync_hangup,
	.read	= ppp_sync_read,
	.write	= ppp_sync_write,
	.ioctl	= ppp_synctty_ioctl,
	.poll	= ppp_sync_poll,
	.receive_buf = ppp_sync_receive,
	.write_wakeup = ppp_sync_wakeup,
};

static int __init
ppp_sync_init(void)
{
	int err;

	err = tty_register_ldisc(N_SYNC_PPP, &ppp_sync_ldisc);
	if (err != 0)
		printk(KERN_ERR "PPP_sync: error %d registering line disc.\n",
		       err);
	return err;
}

/*
 * The following routines provide the PPP channel interface.
 */
static int
ppp_sync_ioctl(struct ppp_channel *chan, unsigned int cmd, unsigned long arg)
{
	struct syncppp *ap = chan->private;
	int err, val;
	u32 accm[8];
	void __user *argp = (void __user *)arg;
	u32 __user *p = argp;

	err = -EFAULT;
	switch (cmd) {
	case PPPIOCGFLAGS:
		val = ap->flags | ap->rbits;
		if (put_user(val, (int __user *) argp))
			break;
		err = 0;
		break;
	case PPPIOCSFLAGS:
		if (get_user(val, (int __user *) argp))
			break;
		ap->flags = val & ~SC_RCV_BITS;
		spin_lock_irq(&ap->recv_lock);
		ap->rbits = val & SC_RCV_BITS;
		spin_unlock_irq(&ap->recv_lock);
		err = 0;
		break;

	case PPPIOCGASYNCMAP:
		if (put_user(ap->xaccm[0], p))
			break;
		err = 0;
		break;
	case PPPIOCSASYNCMAP:
		if (get_user(ap->xaccm[0], p))
			break;
		err = 0;
		break;

	case PPPIOCGRASYNCMAP:
		if (put_user(ap->raccm, p))
			break;
		err = 0;
		break;
	case PPPIOCSRASYNCMAP:
		if (get_user(ap->raccm, p))
			break;
		err = 0;
		break;

	case PPPIOCGXASYNCMAP:
		if (copy_to_user(argp, ap->xaccm, sizeof(ap->xaccm)))
			break;
		err = 0;
		break;
	case PPPIOCSXASYNCMAP:
		if (copy_from_user(accm, argp, sizeof(accm)))
			break;
		accm[2] &= ~0x40000000U;	/* can't escape 0x5e */
		accm[3] |= 0x60000000U;		/* must escape 0x7d, 0x7e */
		memcpy(ap->xaccm, accm, sizeof(ap->xaccm));
		err = 0;
		break;

	case PPPIOCGMRU:
		if (put_user(ap->mru, (int __user *) argp))
			break;
		err = 0;
		break;
	case PPPIOCSMRU:
		if (get_user(val, (int __user *) argp))
			break;
		if (val < PPP_MRU)
			val = PPP_MRU;
		ap->mru = val;
		err = 0;
		break;

	default:
		err = -ENOTTY;
	}
	return err;
}

/*
 * This is called at softirq level to deliver received packets
 * to the ppp_generic code, and to tell the ppp_generic code
 * if we can accept more output now.
 */
static void ppp_sync_process(struct tasklet_struct *t)
{
	struct syncppp *ap = from_tasklet(ap, t, tsk);
	struct sk_buff *skb;

	/* process received packets */
	while ((skb = skb_dequeue(&ap->rqueue)) != NULL) {
		if (skb->len == 0) {
			/* zero length buffers indicate error */
			ppp_input_error(&ap->chan, 0);
			kfree_skb(skb);
		}
		else
			ppp_input(&ap->chan, skb);
	}

	/* try to push more stuff out */
	if (test_bit(XMIT_WAKEUP, &ap->xmit_flags) && ppp_sync_push(ap))
		ppp_output_wakeup(&ap->chan);
}

/*
 * Procedures for encapsulation and framing.
 */

static struct sk_buff*
ppp_sync_txmunge(struct syncppp *ap, struct sk_buff *skb)
{
	int proto;
	unsigned char *data;
	int islcp;

	data  = skb->data;
	proto = get_unaligned_be16(data);

	/* LCP packets with codes between 1 (configure-request)
	 * and 7 (code-reject) must be sent as though no options
	 * have been negotiated.
	 */
	islcp = proto == PPP_LCP && 1 <= data[2] && data[2] <= 7;

	/* compress protocol field if option enabled */
	if (data[0] == 0 && (ap->flags & SC_COMP_PROT) && !islcp)
		skb_pull(skb,1);

	/* prepend address/control fields if necessary */
	if ((ap->flags & SC_COMP_AC) == 0 || islcp) {
		if (skb_headroom(skb) < 2) {
			struct sk_buff *npkt = dev_alloc_skb(skb->len + 2);
			if (npkt == NULL) {
				kfree_skb(skb);
				return NULL;
			}
			skb_reserve(npkt,2);
			skb_copy_from_linear_data(skb,
				      skb_put(npkt, skb->len), skb->len);
			consume_skb(skb);
			skb = npkt;
		}
		skb_push(skb,2);
		skb->data[0] = PPP_ALLSTATIONS;
		skb->data[1] = PPP_UI;
	}

	ap->last_xmit = jiffies;

	if (skb && ap->flags & SC_LOG_OUTPKT)
		ppp_print_buffer ("send buffer", skb->data, skb->len);

	return skb;
}

/*
 * Transmit-side routines.
 */

/*
 * Send a packet to the peer over an sync tty line.
 * Returns 1 iff the packet was accepted.
 * If the packet was not accepted, we will call ppp_output_wakeup
 * at some later time.
 */
static int
ppp_sync_send(struct ppp_channel *chan, struct sk_buff *skb)
{
	struct syncppp *ap = chan->private;

	ppp_sync_push(ap);

	if (test_and_set_bit(XMIT_FULL, &ap->xmit_flags))
		return 0;	/* already full */
	skb = ppp_sync_txmunge(ap, skb);
	if (skb != NULL)
		ap->tpkt = skb;
	else
		clear_bit(XMIT_FULL, &ap->xmit_flags);

	ppp_sync_push(ap);
	return 1;
}

/*
 * Push as much data as possible out to the tty.
 */
static int
ppp_sync_push(struct syncppp *ap)
{
	int sent, done = 0;
	struct tty_struct *tty = ap->tty;
	int tty_stuffed = 0;

	if (!spin_trylock_bh(&ap->xmit_lock))
		return 0;
	for (;;) {
		if (test_and_clear_bit(XMIT_WAKEUP, &ap->xmit_flags))
			tty_stuffed = 0;
		if (!tty_stuffed && ap->tpkt) {
			set_bit(TTY_DO_WRITE_WAKEUP, &tty->flags);
			sent = tty->ops->write(tty, ap->tpkt->data, ap->tpkt->len);
			if (sent < 0)
				goto flush;	/* error, e.g. loss of CD */
			if (sent < ap->tpkt->len) {
				tty_stuffed = 1;
			} else {
				consume_skb(ap->tpkt);
				ap->tpkt = NULL;
				clear_bit(XMIT_FULL, &ap->xmit_flags);
				done = 1;
			}
			continue;
		}
		/* haven't made any progress */
		spin_unlock_bh(&ap->xmit_lock);
		if (!(test_bit(XMIT_WAKEUP, &ap->xmit_flags) ||
		      (!tty_stuffed && ap->tpkt)))
			break;
		if (!spin_trylock_bh(&ap->xmit_lock))
			break;
	}
	return done;

flush:
	if (ap->tpkt) {
		kfree_skb(ap->tpkt);
		ap->tpkt = NULL;
		clear_bit(XMIT_FULL, &ap->xmit_flags);
		done = 1;
	}
	spin_unlock_bh(&ap->xmit_lock);
	return done;
}

/*
 * Flush output from our internal buffers.
 * Called for the TCFLSH ioctl.
 */
static void
ppp_sync_flush_output(struct syncppp *ap)
{
	int done = 0;

	spin_lock_bh(&ap->xmit_lock);
	if (ap->tpkt != NULL) {
		kfree_skb(ap->tpkt);
		ap->tpkt = NULL;
		clear_bit(XMIT_FULL, &ap->xmit_flags);
		done = 1;
	}
	spin_unlock_bh(&ap->xmit_lock);
	if (done)
		ppp_output_wakeup(&ap->chan);
}

/*
 * Receive-side routines.
 */

/* called when the tty driver has data for us.
 *
 * Data is frame oriented: each call to ppp_sync_input is considered
 * a whole frame. If the 1st flag byte is non-zero then the whole
 * frame is considered to be in error and is tossed.
 */
static void
ppp_sync_input(struct syncppp *ap, const unsigned char *buf,
		const char *flags, int count)
{
	struct sk_buff *skb;
	unsigned char *p;

	if (count == 0)
		return;

	if (ap->flags & SC_LOG_INPKT)
		ppp_print_buffer ("receive buffer", buf, count);

	/* stuff the chars in the skb */
	skb = dev_alloc_skb(ap->mru + PPP_HDRLEN + 2);
	if (!skb) {
		printk(KERN_ERR "PPPsync: no memory (input pkt)\n");
		goto err;
	}
	/* Try to get the payload 4-byte aligned */
	if (buf[0] != PPP_ALLSTATIONS)
		skb_reserve(skb, 2 + (buf[0] & 1));

	if (flags && *flags) {
		/* error flag set, ignore frame */
		goto err;
	} else if (count > skb_tailroom(skb)) {
		/* packet overflowed MRU */
		goto err;
	}

	skb_put_data(skb, buf, count);

	/* strip address/control field if present */
	p = skb->data;
	if (p[0] == PPP_ALLSTATIONS && p[1] == PPP_UI) {
		/* chop off address/control */
		if (skb->len < 3)
			goto err;
		p = skb_pull(skb, 2);
	}

	/* PPP packet length should be >= 2 bytes when protocol field is not
	 * compressed.
	 */
	if (!(p[0] & 0x01) && skb->len < 2)
		goto err;

	/* queue the frame to be processed */
	skb_queue_tail(&ap->rqueue, skb);
	return;

err:
	/* queue zero length packet as error indication */
	if (skb || (skb = dev_alloc_skb(0))) {
		skb_trim(skb, 0);
		skb_queue_tail(&ap->rqueue, skb);
	}
}

static void __exit
ppp_sync_cleanup(void)
{
	if (tty_unregister_ldisc(N_SYNC_PPP) != 0)
		printk(KERN_ERR "failed to unregister Sync PPP line discipline\n");
}

module_init(ppp_sync_init);
module_exit(ppp_sync_cleanup);
MODULE_LICENSE("GPL");
MODULE_ALIAS_LDISC(N_SYNC_PPP);
Commit	Line	Data
2874c5fd	1	// SPDX-License-Identifier: GPL-2.0-or-later
1da177e4 LT	2	/*
	3	* PPP synchronous tty channel driver for Linux.
	4	*
	5	* This is a ppp channel driver that can be used with tty device drivers
	6	* that are frame oriented, such as synchronous HDLC devices.
	7	*
	8	* Complete PPP frames without encoding/decoding are exchanged between
	9	* the channel driver and the device driver.
6aa20a22	10	*
1da177e4 LT	11	* The async map IOCTL codes are implemented to keep the user mode
	12	* applications happy if they call them. Synchronous PPP does not use
	13	* the async maps.
	14	*
	15	* Copyright 1999 Paul Mackerras.
	16	*
	17	* Also touched by the grubby hands of Paul Fulghum paulkf@microgate.com
	18	*
1da177e4 LT	19	* This driver provides the encapsulation and framing for sending
	20	* and receiving PPP frames over sync serial lines. It relies on
	21	* the generic PPP layer to give it frames to send and to process
	22	* received frames. It implements the PPP line discipline.
	23	*
	24	* Part of the code in this driver was inspired by the old async-only
	25	* PPP driver, written by Michael Callahan and Al Longyear, and
	26	* subsequently hacked by Paul Mackerras.
	27	*
	28	* ==FILEVERSION 20040616==
	29	*/
	30
	31	#include <linux/module.h>
	32	#include <linux/kernel.h>
	33	#include <linux/skbuff.h>
	34	#include <linux/tty.h>
	35	#include <linux/netdevice.h>
	36	#include <linux/poll.h>
	37	#include <linux/ppp_defs.h>
4b32da2b	38	#include <linux/ppp-ioctl.h>
1da177e4 LT	39	#include <linux/ppp_channel.h>
1da177e4 LT	40	#include <linux/spinlock.h>
5e41fb83	41	#include <linux/completion.h>
1da177e4	42	#include <linux/init.h>
a6b7a407	43	#include <linux/interrupt.h>
5a0e3ad6	44	#include <linux/slab.h>
709c89b4	45	#include <linux/refcount.h>
96545aeb	46	#include <asm/unaligned.h>
7c0f6ba6	47	#include <linux/uaccess.h>
1da177e4 LT	48
	49	#define PPP_VERSION "2.4.2"
	50
	51	/* Structure for storing local state. */
	52	struct syncppp {
	53	struct tty_struct *tty;
	54	unsigned int flags;
	55	unsigned int rbits;
	56	int mru;
	57	spinlock_t xmit_lock;
	58	spinlock_t recv_lock;
	59	unsigned long xmit_flags;
	60	u32 xaccm[8];
	61	u32 raccm;
	62	unsigned int bytes_sent;
	63	unsigned int bytes_rcvd;
	64
	65	struct sk_buff *tpkt;
	66	unsigned long last_xmit;
	67
	68	struct sk_buff_head rqueue;
	69
	70	struct tasklet_struct tsk;
	71
709c89b4	72	refcount_t refcnt;
5e41fb83	73	struct completion dead_cmp;
1da177e4 LT	74	struct ppp_channel chan; /* interface to generic ppp layer */
	75	};
	76
	77	/* Bit numbers in xmit_flags */
	78	#define XMIT_WAKEUP 0
	79	#define XMIT_FULL 1
	80
	81	/* Bits in rbits */
	82	#define SC_RCV_BITS (SC_RCV_B7_1\|SC_RCV_B7_0\|SC_RCV_ODDP\|SC_RCV_EVNP)
	83
	84	#define PPPSYNC_MAX_RQLEN 32 /* arbitrary */
	85
	86	/*
	87	* Prototypes.
	88	*/
	89	static struct sk_buff* ppp_sync_txmunge(struct syncppp ap, struct sk_buff );
	90	static int ppp_sync_send(struct ppp_channel chan, struct sk_buff skb);
	91	static int ppp_sync_ioctl(struct ppp_channel *chan, unsigned int cmd,
	92	unsigned long arg);
64ca5aba	93	static void ppp_sync_process(struct tasklet_struct *t);
1da177e4 LT	94	static int ppp_sync_push(struct syncppp *ap);
	95	static void ppp_sync_flush_output(struct syncppp *ap);
	96	static void ppp_sync_input(struct syncppp ap, const unsigned char buf,
0f3dcf3b	97	const char *flags, int count);
1da177e4	98
d7100da0	99	static const struct ppp_channel_ops sync_ops = {
	100	.start_xmit = ppp_sync_send,
	101	.ioctl = ppp_sync_ioctl,
1da177e4 LT	102	};
	103
	104	/*
167bfa71	105	* Utility procedure to print a buffer in hex/ascii
1da177e4	106	*/
1da177e4 LT	107	static void
	108	ppp_print_buffer (const char name, const __u8 buf, int count)
	109	{
1da177e4 LT	110	if (name != NULL)
	111	printk(KERN_DEBUG "ppp_synctty: %s, count = %d\n", name, count);
	112
167bfa71	113	print_hex_dump_bytes("", DUMP_PREFIX_NONE, buf, count);
1da177e4 LT	114	}
	115
	116
	117	/*
	118	* Routines implementing the synchronous PPP line discipline.
	119	*/
	120
	121	/*
	122	* We have a potential race on dereferencing tty->disc_data,
	123	* because the tty layer provides no locking at all - thus one
	124	* cpu could be running ppp_synctty_receive while another
	125	* calls ppp_synctty_close, which zeroes tty->disc_data and
	126	* frees the memory that ppp_synctty_receive is using. The best
	127	* way to fix this is to use a rwlock in the tty struct, but for now
	128	* we use a single global rwlock for all ttys in ppp line discipline.
	129	*
25985edc	130	* FIXME: Fixed in tty_io nowadays.
1da177e4 LT	131	*/
	132	static DEFINE_RWLOCK(disc_data_lock);
	133
	134	static struct syncppp sp_get(struct tty_struct tty)
	135	{
	136	struct syncppp *ap;
	137
	138	read_lock(&disc_data_lock);
	139	ap = tty->disc_data;
	140	if (ap != NULL)
709c89b4	141	refcount_inc(&ap->refcnt);
1da177e4 LT	142	read_unlock(&disc_data_lock);
	143	return ap;
	144	}
	145
	146	static void sp_put(struct syncppp *ap)
	147	{
709c89b4	148	if (refcount_dec_and_test(&ap->refcnt))
5e41fb83	149	complete(&ap->dead_cmp);
1da177e4 LT	150	}
	151
	152	/*
	153	* Called when a tty is put into sync-PPP line discipline.
	154	*/
	155	static int
	156	ppp_sync_open(struct tty_struct *tty)
	157	{
	158	struct syncppp *ap;
	159	int err;
9c705260	160	int speed;
1da177e4	161
f34d7a5b AC	162	if (tty->ops->write == NULL)
	163	return -EOPNOTSUPP;
	164
dd00cc48	165	ap = kzalloc(sizeof(*ap), GFP_KERNEL);
1da177e4	166	err = -ENOMEM;
cd228d54	167	if (!ap)
1da177e4 LT	168	goto out;
	169
	170	/* initialize the syncppp structure */
1da177e4 LT	171	ap->tty = tty;
	172	ap->mru = PPP_MRU;
	173	spin_lock_init(&ap->xmit_lock);
	174	spin_lock_init(&ap->recv_lock);
	175	ap->xaccm[0] = ~0U;
	176	ap->xaccm[3] = 0x60000000U;
	177	ap->raccm = ~0U;
	178
	179	skb_queue_head_init(&ap->rqueue);
64ca5aba	180	tasklet_setup(&ap->tsk, ppp_sync_process);
1da177e4	181
709c89b4	182	refcount_set(&ap->refcnt, 1);
5e41fb83	183	init_completion(&ap->dead_cmp);
1da177e4 LT	184
	185	ap->chan.private = ap;
	186	ap->chan.ops = &sync_ops;
	187	ap->chan.mtu = PPP_MRU;
	188	ap->chan.hdrlen = 2; /* for A/C bytes */
9c705260 GP	189	speed = tty_get_baud_rate(tty);
9c705260 GP	190	ap->chan.speed = speed;
1da177e4 LT	191	err = ppp_register_channel(&ap->chan);
	192	if (err)
	193	goto out_free;
	194
	195	tty->disc_data = ap;
33f0f88f	196	tty->receive_room = 65536;
1da177e4 LT	197	return 0;
	198
	199	out_free:
	200	kfree(ap);
	201	out:
	202	return err;
	203	}
	204
	205	/*
	206	* Called when the tty is put into another line discipline
	207	* or it hangs up. We have to wait for any cpu currently
	208	* executing in any of the other ppp_synctty_* routines to
	209	* finish before we can call ppp_unregister_channel and free
	210	* the syncppp struct. This routine must be called from
	211	* process context, not interrupt or softirq context.
	212	*/
	213	static void
	214	ppp_sync_close(struct tty_struct *tty)
	215	{
	216	struct syncppp *ap;
	217
	218	write_lock_irq(&disc_data_lock);
	219	ap = tty->disc_data;
	220	tty->disc_data = NULL;
	221	write_unlock_irq(&disc_data_lock);
cd228d54	222	if (!ap)
1da177e4 LT	223	return;
	224
	225	/*
	226	* We have now ensured that nobody can start using ap from now
	227	* on, but we have to wait for all existing users to finish.
	228	* Note that ppp_unregister_channel ensures that no calls to
	229	* our channel ops (i.e. ppp_sync_send/ioctl) are in progress
	230	* by the time it returns.
	231	*/
709c89b4	232	if (!refcount_dec_and_test(&ap->refcnt))
5e41fb83	233	wait_for_completion(&ap->dead_cmp);
1da177e4 LT	234	tasklet_kill(&ap->tsk);
	235
	236	ppp_unregister_channel(&ap->chan);
	237	skb_queue_purge(&ap->rqueue);
1d2f8c95	238	kfree_skb(ap->tpkt);
1da177e4 LT	239	kfree(ap);
	240	}
	241
	242	/*
	243	* Called on tty hangup in process context.
	244	*
	245	* Wait for I/O to driver to complete and unregister PPP channel.
	246	* This is already done by the close routine, so just call that.
	247	*/
	248	static int ppp_sync_hangup(struct tty_struct *tty)
	249	{
	250	ppp_sync_close(tty);
	251	return 0;
	252	}
	253
	254	/*
	255	* Read does nothing - no data is ever available this way.
	256	* Pppd reads and writes packets via /dev/ppp instead.
	257	*/
	258	static ssize_t
	259	ppp_sync_read(struct tty_struct tty, struct file file,
3b830a9c LT	260	unsigned char *buf, size_t count,
3b830a9c LT	261	void **cookie, unsigned long offset)
1da177e4 LT	262	{
	263	return -EAGAIN;
	264	}
	265
	266	/*
	267	* Write on the tty does nothing, the packets all come in
	268	* from the ppp generic stuff.
	269	*/
	270	static ssize_t
	271	ppp_sync_write(struct tty_struct tty, struct file file,
	272	const unsigned char *buf, size_t count)
	273	{
	274	return -EAGAIN;
	275	}
	276
	277	static int
	278	ppp_synctty_ioctl(struct tty_struct tty, struct file file,
	279	unsigned int cmd, unsigned long arg)
	280	{
	281	struct syncppp *ap = sp_get(tty);
	282	int __user p = (int __user )arg;
	283	int err, val;
	284
cd228d54	285	if (!ap)
1da177e4 LT	286	return -ENXIO;
	287	err = -EFAULT;
	288	switch (cmd) {
	289	case PPPIOCGCHAN:
1da177e4 LT	290	err = -EFAULT;
	291	if (put_user(ppp_channel_index(&ap->chan), p))
	292	break;
	293	err = 0;
	294	break;
	295
	296	case PPPIOCGUNIT:
1da177e4 LT	297	err = -EFAULT;
	298	if (put_user(ppp_unit_number(&ap->chan), p))
	299	break;
	300	err = 0;
	301	break;
	302
1da177e4 LT	303	case TCFLSH:
	304	/* flush our buffers and the serial port's buffer */
	305	if (arg == TCIOFLUSH \|\| arg == TCOFLUSH)
	306	ppp_sync_flush_output(ap);
e7f3880c	307	err = n_tty_ioctl_helper(tty, file, cmd, arg);
1da177e4 LT	308	break;
	309
	310	case FIONREAD:
	311	val = 0;
	312	if (put_user(val, p))
	313	break;
	314	err = 0;
	315	break;
	316
	317	default:
d0127539 AC	318	err = tty_mode_ioctl(tty, file, cmd, arg);
d0127539 AC	319	break;
1da177e4 LT	320	}
	321
	322	sp_put(ap);
	323	return err;
	324	}
	325
	326	/* No kernel lock - fine */
afc9a42b	327	static __poll_t
1da177e4 LT	328	ppp_sync_poll(struct tty_struct tty, struct file file, poll_table *wait)
	329	{
	330	return 0;
	331	}
	332
92d326f6	333	/* May sleep, don't call from interrupt level or with interrupts disabled */
55db4c64	334	static void
1da177e4	335	ppp_sync_receive(struct tty_struct tty, const unsigned char buf,
0f3dcf3b	336	const char *cflags, int count)
1da177e4 LT	337	{
	338	struct syncppp *ap = sp_get(tty);
	339	unsigned long flags;
	340
cd228d54	341	if (!ap)
55db4c64	342	return;
1da177e4 LT	343	spin_lock_irqsave(&ap->recv_lock, flags);
	344	ppp_sync_input(ap, buf, cflags, count);
	345	spin_unlock_irqrestore(&ap->recv_lock, flags);
b03efcfb	346	if (!skb_queue_empty(&ap->rqueue))
1da177e4 LT	347	tasklet_schedule(&ap->tsk);
1da177e4 LT	348	sp_put(ap);
4a21b8cb	349	tty_unthrottle(tty);
1da177e4 LT	350	}
	351
	352	static void
	353	ppp_sync_wakeup(struct tty_struct *tty)
	354	{
	355	struct syncppp *ap = sp_get(tty);
	356
	357	clear_bit(TTY_DO_WRITE_WAKEUP, &tty->flags);
cd228d54	358	if (!ap)
1da177e4 LT	359	return;
	360	set_bit(XMIT_WAKEUP, &ap->xmit_flags);
	361	tasklet_schedule(&ap->tsk);
	362	sp_put(ap);
	363	}
	364
	365
a352def2	366	static struct tty_ldisc_ops ppp_sync_ldisc = {
1da177e4	367	.owner = THIS_MODULE,
1da177e4 LT	368	.name = "pppsync",
	369	.open = ppp_sync_open,
	370	.close = ppp_sync_close,
	371	.hangup = ppp_sync_hangup,
	372	.read = ppp_sync_read,
	373	.write = ppp_sync_write,
	374	.ioctl = ppp_synctty_ioctl,
	375	.poll = ppp_sync_poll,
1da177e4 LT	376	.receive_buf = ppp_sync_receive,
	377	.write_wakeup = ppp_sync_wakeup,
	378	};
	379
	380	static int __init
	381	ppp_sync_init(void)
	382	{
	383	int err;
	384
	385	err = tty_register_ldisc(N_SYNC_PPP, &ppp_sync_ldisc);
	386	if (err != 0)
	387	printk(KERN_ERR "PPP_sync: error %d registering line disc.\n",
	388	err);
	389	return err;
	390	}
	391
	392	/*
	393	* The following routines provide the PPP channel interface.
	394	*/
	395	static int
	396	ppp_sync_ioctl(struct ppp_channel *chan, unsigned int cmd, unsigned long arg)
	397	{
	398	struct syncppp *ap = chan->private;
	399	int err, val;
	400	u32 accm[8];
	401	void __user argp = (void __user )arg;
	402	u32 __user *p = argp;
	403
	404	err = -EFAULT;
	405	switch (cmd) {
	406	case PPPIOCGFLAGS:
	407	val = ap->flags \| ap->rbits;
	408	if (put_user(val, (int __user *) argp))
	409	break;
	410	err = 0;
	411	break;
	412	case PPPIOCSFLAGS:
	413	if (get_user(val, (int __user *) argp))
	414	break;
	415	ap->flags = val & ~SC_RCV_BITS;
	416	spin_lock_irq(&ap->recv_lock);
	417	ap->rbits = val & SC_RCV_BITS;
	418	spin_unlock_irq(&ap->recv_lock);
	419	err = 0;
	420	break;
	421
	422	case PPPIOCGASYNCMAP:
	423	if (put_user(ap->xaccm[0], p))
	424	break;
	425	err = 0;
	426	break;
	427	case PPPIOCSASYNCMAP:
	428	if (get_user(ap->xaccm[0], p))
	429	break;
	430	err = 0;
	431	break;
	432
	433	case PPPIOCGRASYNCMAP:
	434	if (put_user(ap->raccm, p))
	435	break;
	436	err = 0;
	437	break;
	438	case PPPIOCSRASYNCMAP:
	439	if (get_user(ap->raccm, p))
440	break;
441	err = 0;
442	break;
443
444	case PPPIOCGXASYNCMAP:
445	if (copy_to_user(argp, ap->xaccm, sizeof(ap->xaccm)))
446	break;
447	err = 0;
448	break;
449	case PPPIOCSXASYNCMAP:
450	if (copy_from_user(accm, argp, sizeof(accm)))
451	break;
452	accm[2] &= ~0x40000000U; /* can't escape 0x5e */
453	accm[3] \|= 0x60000000U; /* must escape 0x7d, 0x7e */
454	memcpy(ap->xaccm, accm, sizeof(ap->xaccm));
455	err = 0;
456	break;
457
458	case PPPIOCGMRU:
459	if (put_user(ap->mru, (int __user *) argp))
460	break;
461	err = 0;
462	break;
463	case PPPIOCSMRU:
464	if (get_user(val, (int __user *) argp))
465	break;
466	if (val < PPP_MRU)
467	val = PPP_MRU;
468	ap->mru = val;
469	err = 0;
470	break;
471
472	default:
473	err = -ENOTTY;
474	}
475	return err;
476	}
477
478	/*
479	* This is called at softirq level to deliver received packets
480	* to the ppp_generic code, and to tell the ppp_generic code
481	* if we can accept more output now.
482	*/
64ca5aba	483	static void ppp_sync_process(struct tasklet_struct *t)
1da177e4	484	{
64ca5aba	485	struct syncppp *ap = from_tasklet(ap, t, tsk);
1da177e4 LT	486	struct sk_buff *skb;
	487
	488	/* process received packets */
	489	while ((skb = skb_dequeue(&ap->rqueue)) != NULL) {
	490	if (skb->len == 0) {
	491	/* zero length buffers indicate error */
	492	ppp_input_error(&ap->chan, 0);
	493	kfree_skb(skb);
	494	}
	495	else
	496	ppp_input(&ap->chan, skb);
	497	}
	498
	499	/* try to push more stuff out */
	500	if (test_bit(XMIT_WAKEUP, &ap->xmit_flags) && ppp_sync_push(ap))
	501	ppp_output_wakeup(&ap->chan);
	502	}
	503
	504	/*
	505	* Procedures for encapsulation and framing.
	506	*/
	507
3c582b30	508	static struct sk_buff*
1da177e4 LT	509	ppp_sync_txmunge(struct syncppp ap, struct sk_buff skb)
	510	{
	511	int proto;
	512	unsigned char *data;
	513	int islcp;
	514
	515	data = skb->data;
96545aeb	516	proto = get_unaligned_be16(data);
1da177e4 LT	517
	518	/* LCP packets with codes between 1 (configure-request)
	519	* and 7 (code-reject) must be sent as though no options
	520	* have been negotiated.
	521	*/
	522	islcp = proto == PPP_LCP && 1 <= data[2] && data[2] <= 7;
	523
	524	/* compress protocol field if option enabled */
	525	if (data[0] == 0 && (ap->flags & SC_COMP_PROT) && !islcp)
	526	skb_pull(skb,1);
	527
	528	/* prepend address/control fields if necessary */
	529	if ((ap->flags & SC_COMP_AC) == 0 \|\| islcp) {
	530	if (skb_headroom(skb) < 2) {
	531	struct sk_buff *npkt = dev_alloc_skb(skb->len + 2);
	532	if (npkt == NULL) {
	533	kfree_skb(skb);
	534	return NULL;
	535	}
	536	skb_reserve(npkt,2);
d626f62b ACM	537	skb_copy_from_linear_data(skb,
d626f62b ACM	538	skb_put(npkt, skb->len), skb->len);
968d7018	539	consume_skb(skb);
1da177e4 LT	540	skb = npkt;
	541	}
	542	skb_push(skb,2);
	543	skb->data[0] = PPP_ALLSTATIONS;
	544	skb->data[1] = PPP_UI;
	545	}
	546
	547	ap->last_xmit = jiffies;
	548
	549	if (skb && ap->flags & SC_LOG_OUTPKT)
	550	ppp_print_buffer ("send buffer", skb->data, skb->len);
	551
	552	return skb;
	553	}
	554
	555	/*
	556	* Transmit-side routines.
	557	*/
	558
	559	/*
	560	* Send a packet to the peer over an sync tty line.
	561	* Returns 1 iff the packet was accepted.
	562	* If the packet was not accepted, we will call ppp_output_wakeup
	563	* at some later time.
	564	*/
	565	static int
	566	ppp_sync_send(struct ppp_channel chan, struct sk_buff skb)
	567	{
	568	struct syncppp *ap = chan->private;
	569
	570	ppp_sync_push(ap);
	571
	572	if (test_and_set_bit(XMIT_FULL, &ap->xmit_flags))
	573	return 0; /* already full */
	574	skb = ppp_sync_txmunge(ap, skb);
	575	if (skb != NULL)
	576	ap->tpkt = skb;
	577	else
	578	clear_bit(XMIT_FULL, &ap->xmit_flags);
	579
	580	ppp_sync_push(ap);
	581	return 1;
	582	}
	583
	584	/*
	585	* Push as much data as possible out to the tty.
	586	*/
	587	static int
	588	ppp_sync_push(struct syncppp *ap)
	589	{
	590	int sent, done = 0;
	591	struct tty_struct *tty = ap->tty;
	592	int tty_stuffed = 0;
	593
	594	if (!spin_trylock_bh(&ap->xmit_lock))
	595	return 0;
	596	for (;;) {
	597	if (test_and_clear_bit(XMIT_WAKEUP, &ap->xmit_flags))
	598	tty_stuffed = 0;
cd228d54	599	if (!tty_stuffed && ap->tpkt) {
1da177e4	600	set_bit(TTY_DO_WRITE_WAKEUP, &tty->flags);
f34d7a5b	601	sent = tty->ops->write(tty, ap->tpkt->data, ap->tpkt->len);
1da177e4 LT	602	if (sent < 0)
	603	goto flush; /* error, e.g. loss of CD */
	604	if (sent < ap->tpkt->len) {
	605	tty_stuffed = 1;
	606	} else {
968d7018	607	consume_skb(ap->tpkt);
1da177e4 LT	608	ap->tpkt = NULL;
	609	clear_bit(XMIT_FULL, &ap->xmit_flags);
	610	done = 1;
	611	}
	612	continue;
	613	}
	614	/* haven't made any progress */
	615	spin_unlock_bh(&ap->xmit_lock);
8e95a202 JP	616	if (!(test_bit(XMIT_WAKEUP, &ap->xmit_flags) \|\|
8e95a202 JP	617	(!tty_stuffed && ap->tpkt)))
1da177e4 LT	618	break;
	619	if (!spin_trylock_bh(&ap->xmit_lock))
	620	break;
	621	}
	622	return done;
	623
	624	flush:
cd228d54	625	if (ap->tpkt) {
1da177e4 LT	626	kfree_skb(ap->tpkt);
	627	ap->tpkt = NULL;
	628	clear_bit(XMIT_FULL, &ap->xmit_flags);
	629	done = 1;
	630	}
	631	spin_unlock_bh(&ap->xmit_lock);
	632	return done;
	633	}
	634
	635	/*
	636	* Flush output from our internal buffers.
	637	* Called for the TCFLSH ioctl.
	638	*/
	639	static void
	640	ppp_sync_flush_output(struct syncppp *ap)
	641	{
	642	int done = 0;
	643
	644	spin_lock_bh(&ap->xmit_lock);
	645	if (ap->tpkt != NULL) {
	646	kfree_skb(ap->tpkt);
	647	ap->tpkt = NULL;
	648	clear_bit(XMIT_FULL, &ap->xmit_flags);
	649	done = 1;
	650	}
	651	spin_unlock_bh(&ap->xmit_lock);
	652	if (done)
	653	ppp_output_wakeup(&ap->chan);
	654	}
	655
	656	/*
	657	* Receive-side routines.
	658	*/
	659
	660	/* called when the tty driver has data for us.
	661	*
	662	* Data is frame oriented: each call to ppp_sync_input is considered
	663	* a whole frame. If the 1st flag byte is non-zero then the whole
	664	* frame is considered to be in error and is tossed.
	665	*/
	666	static void
	667	ppp_sync_input(struct syncppp ap, const unsigned char buf,
0f3dcf3b	668	const char *flags, int count)
1da177e4 LT	669	{
	670	struct sk_buff *skb;
	671	unsigned char *p;
	672
	673	if (count == 0)
	674	return;
	675
	676	if (ap->flags & SC_LOG_INPKT)
	677	ppp_print_buffer ("receive buffer", buf, count);
	678
	679	/* stuff the chars in the skb */
cd228d54 JP	680	skb = dev_alloc_skb(ap->mru + PPP_HDRLEN + 2);
cd228d54 JP	681	if (!skb) {
1da177e4 LT	682	printk(KERN_ERR "PPPsync: no memory (input pkt)\n");
	683	goto err;
	684	}
	685	/* Try to get the payload 4-byte aligned */
	686	if (buf[0] != PPP_ALLSTATIONS)
	687	skb_reserve(skb, 2 + (buf[0] & 1));
	688
cd228d54	689	if (flags && *flags) {
1da177e4 LT	690	/* error flag set, ignore frame */
	691	goto err;
	692	} else if (count > skb_tailroom(skb)) {
	693	/* packet overflowed MRU */
	694	goto err;
	695	}
	696
b952f4df	697	skb_put_data(skb, buf, count);
1da177e4 LT	698
	699	/* strip address/control field if present */
	700	p = skb->data;
	701	if (p[0] == PPP_ALLSTATIONS && p[1] == PPP_UI) {
	702	/* chop off address/control */
	703	if (skb->len < 3)
	704	goto err;
	705	p = skb_pull(skb, 2);
	706	}
	707
7fb1b8ca SP	708	/* PPP packet length should be >= 2 bytes when protocol field is not
	709	* compressed.
	710	*/
	711	if (!(p[0] & 0x01) && skb->len < 2)
1da177e4 LT	712	goto err;
	713
	714	/* queue the frame to be processed */
	715	skb_queue_tail(&ap->rqueue, skb);
	716	return;
	717
	718	err:
	719	/* queue zero length packet as error indication */
	720	if (skb \|\| (skb = dev_alloc_skb(0))) {
	721	skb_trim(skb, 0);
	722	skb_queue_tail(&ap->rqueue, skb);
	723	}
	724	}
	725
	726	static void __exit
	727	ppp_sync_cleanup(void)
	728	{
64ccd715	729	if (tty_unregister_ldisc(N_SYNC_PPP) != 0)
1da177e4 LT	730	printk(KERN_ERR "failed to unregister Sync PPP line discipline\n");
	731	}
	732
	733	module_init(ppp_sync_init);
	734	module_exit(ppp_sync_cleanup);
	735	MODULE_LICENSE("GPL");
	736	MODULE_ALIAS_LDISC(N_SYNC_PPP);