2 * PPP synchronous tty channel driver for Linux.
4 * This is a ppp channel driver that can be used with tty device drivers
5 * that are frame oriented, such as synchronous HDLC devices.
7 * Complete PPP frames without encoding/decoding are exchanged between
8 * the channel driver and the device driver.
10 * The async map IOCTL codes are implemented to keep the user mode
11 * applications happy if they call them. Synchronous PPP does not use
14 * Copyright 1999 Paul Mackerras.
16 * Also touched by the grubby hands of Paul Fulghum paulkf@microgate.com
18 * This program is free software; you can redistribute it and/or
19 * modify it under the terms of the GNU General Public License
20 * as published by the Free Software Foundation; either version
21 * 2 of the License, or (at your option) any later version.
23 * This driver provides the encapsulation and framing for sending
24 * and receiving PPP frames over sync serial lines. It relies on
25 * the generic PPP layer to give it frames to send and to process
26 * received frames. It implements the PPP line discipline.
28 * Part of the code in this driver was inspired by the old async-only
29 * PPP driver, written by Michael Callahan and Al Longyear, and
30 * subsequently hacked by Paul Mackerras.
32 * ==FILEVERSION 20040616==
35 #include <linux/module.h>
36 #include <linux/kernel.h>
37 #include <linux/skbuff.h>
38 #include <linux/tty.h>
39 #include <linux/netdevice.h>
40 #include <linux/poll.h>
41 #include <linux/ppp_defs.h>
42 #include <linux/ppp-ioctl.h>
43 #include <linux/ppp_channel.h>
44 #include <linux/spinlock.h>
45 #include <linux/completion.h>
46 #include <linux/init.h>
47 #include <linux/interrupt.h>
48 #include <linux/slab.h>
49 #include <linux/refcount.h>
50 #include <asm/unaligned.h>
51 #include <linux/uaccess.h>
53 #define PPP_VERSION "2.4.2"
55 /* Structure for storing local state. */
57 struct tty_struct *tty;
63 unsigned long xmit_flags;
66 unsigned int bytes_sent;
67 unsigned int bytes_rcvd;
70 unsigned long last_xmit;
72 struct sk_buff_head rqueue;
74 struct tasklet_struct tsk;
77 struct completion dead_cmp;
78 struct ppp_channel chan; /* interface to generic ppp layer */
81 /* Bit numbers in xmit_flags */
86 #define SC_RCV_BITS (SC_RCV_B7_1|SC_RCV_B7_0|SC_RCV_ODDP|SC_RCV_EVNP)
88 #define PPPSYNC_MAX_RQLEN 32 /* arbitrary */
93 static struct sk_buff* ppp_sync_txmunge(struct syncppp *ap, struct sk_buff *);
94 static int ppp_sync_send(struct ppp_channel *chan, struct sk_buff *skb);
95 static int ppp_sync_ioctl(struct ppp_channel *chan, unsigned int cmd,
97 static void ppp_sync_process(unsigned long arg);
98 static int ppp_sync_push(struct syncppp *ap);
99 static void ppp_sync_flush_output(struct syncppp *ap);
100 static void ppp_sync_input(struct syncppp *ap, const unsigned char *buf,
101 char *flags, int count);
103 static const struct ppp_channel_ops sync_ops = {
104 .start_xmit = ppp_sync_send,
105 .ioctl = ppp_sync_ioctl,
109 * Utility procedure to print a buffer in hex/ascii
112 ppp_print_buffer (const char *name, const __u8 *buf, int count)
115 printk(KERN_DEBUG "ppp_synctty: %s, count = %d\n", name, count);
117 print_hex_dump_bytes("", DUMP_PREFIX_NONE, buf, count);
122 * Routines implementing the synchronous PPP line discipline.
126 * We have a potential race on dereferencing tty->disc_data,
127 * because the tty layer provides no locking at all - thus one
128 * cpu could be running ppp_synctty_receive while another
129 * calls ppp_synctty_close, which zeroes tty->disc_data and
130 * frees the memory that ppp_synctty_receive is using. The best
131 * way to fix this is to use a rwlock in the tty struct, but for now
132 * we use a single global rwlock for all ttys in ppp line discipline.
134 * FIXME: Fixed in tty_io nowadays.
136 static DEFINE_RWLOCK(disc_data_lock);
138 static struct syncppp *sp_get(struct tty_struct *tty)
142 read_lock(&disc_data_lock);
145 refcount_inc(&ap->refcnt);
146 read_unlock(&disc_data_lock);
150 static void sp_put(struct syncppp *ap)
152 if (refcount_dec_and_test(&ap->refcnt))
153 complete(&ap->dead_cmp);
157 * Called when a tty is put into sync-PPP line discipline.
160 ppp_sync_open(struct tty_struct *tty)
166 if (tty->ops->write == NULL)
169 ap = kzalloc(sizeof(*ap), GFP_KERNEL);
174 /* initialize the syncppp structure */
177 spin_lock_init(&ap->xmit_lock);
178 spin_lock_init(&ap->recv_lock);
180 ap->xaccm[3] = 0x60000000U;
183 skb_queue_head_init(&ap->rqueue);
184 tasklet_init(&ap->tsk, ppp_sync_process, (unsigned long) ap);
186 refcount_set(&ap->refcnt, 1);
187 init_completion(&ap->dead_cmp);
189 ap->chan.private = ap;
190 ap->chan.ops = &sync_ops;
191 ap->chan.mtu = PPP_MRU;
192 ap->chan.hdrlen = 2; /* for A/C bytes */
193 speed = tty_get_baud_rate(tty);
194 ap->chan.speed = speed;
195 err = ppp_register_channel(&ap->chan);
200 tty->receive_room = 65536;
210 * Called when the tty is put into another line discipline
211 * or it hangs up. We have to wait for any cpu currently
212 * executing in any of the other ppp_synctty_* routines to
213 * finish before we can call ppp_unregister_channel and free
214 * the syncppp struct. This routine must be called from
215 * process context, not interrupt or softirq context.
218 ppp_sync_close(struct tty_struct *tty)
222 write_lock_irq(&disc_data_lock);
224 tty->disc_data = NULL;
225 write_unlock_irq(&disc_data_lock);
230 * We have now ensured that nobody can start using ap from now
231 * on, but we have to wait for all existing users to finish.
232 * Note that ppp_unregister_channel ensures that no calls to
233 * our channel ops (i.e. ppp_sync_send/ioctl) are in progress
234 * by the time it returns.
236 if (!refcount_dec_and_test(&ap->refcnt))
237 wait_for_completion(&ap->dead_cmp);
238 tasklet_kill(&ap->tsk);
240 ppp_unregister_channel(&ap->chan);
241 skb_queue_purge(&ap->rqueue);
247 * Called on tty hangup in process context.
249 * Wait for I/O to driver to complete and unregister PPP channel.
250 * This is already done by the close routine, so just call that.
252 static int ppp_sync_hangup(struct tty_struct *tty)
259 * Read does nothing - no data is ever available this way.
260 * Pppd reads and writes packets via /dev/ppp instead.
263 ppp_sync_read(struct tty_struct *tty, struct file *file,
264 unsigned char __user *buf, size_t count)
270 * Write on the tty does nothing, the packets all come in
271 * from the ppp generic stuff.
274 ppp_sync_write(struct tty_struct *tty, struct file *file,
275 const unsigned char *buf, size_t count)
281 ppp_synctty_ioctl(struct tty_struct *tty, struct file *file,
282 unsigned int cmd, unsigned long arg)
284 struct syncppp *ap = sp_get(tty);
285 int __user *p = (int __user *)arg;
294 if (put_user(ppp_channel_index(&ap->chan), p))
301 if (put_user(ppp_unit_number(&ap->chan), p))
307 /* flush our buffers and the serial port's buffer */
308 if (arg == TCIOFLUSH || arg == TCOFLUSH)
309 ppp_sync_flush_output(ap);
310 err = n_tty_ioctl_helper(tty, file, cmd, arg);
315 if (put_user(val, p))
321 err = tty_mode_ioctl(tty, file, cmd, arg);
329 /* No kernel lock - fine */
331 ppp_sync_poll(struct tty_struct *tty, struct file *file, poll_table *wait)
336 /* May sleep, don't call from interrupt level or with interrupts disabled */
338 ppp_sync_receive(struct tty_struct *tty, const unsigned char *buf,
339 char *cflags, int count)
341 struct syncppp *ap = sp_get(tty);
346 spin_lock_irqsave(&ap->recv_lock, flags);
347 ppp_sync_input(ap, buf, cflags, count);
348 spin_unlock_irqrestore(&ap->recv_lock, flags);
349 if (!skb_queue_empty(&ap->rqueue))
350 tasklet_schedule(&ap->tsk);
356 ppp_sync_wakeup(struct tty_struct *tty)
358 struct syncppp *ap = sp_get(tty);
360 clear_bit(TTY_DO_WRITE_WAKEUP, &tty->flags);
363 set_bit(XMIT_WAKEUP, &ap->xmit_flags);
364 tasklet_schedule(&ap->tsk);
369 static struct tty_ldisc_ops ppp_sync_ldisc = {
370 .owner = THIS_MODULE,
371 .magic = TTY_LDISC_MAGIC,
373 .open = ppp_sync_open,
374 .close = ppp_sync_close,
375 .hangup = ppp_sync_hangup,
376 .read = ppp_sync_read,
377 .write = ppp_sync_write,
378 .ioctl = ppp_synctty_ioctl,
379 .poll = ppp_sync_poll,
380 .receive_buf = ppp_sync_receive,
381 .write_wakeup = ppp_sync_wakeup,
389 err = tty_register_ldisc(N_SYNC_PPP, &ppp_sync_ldisc);
391 printk(KERN_ERR "PPP_sync: error %d registering line disc.\n",
397 * The following routines provide the PPP channel interface.
400 ppp_sync_ioctl(struct ppp_channel *chan, unsigned int cmd, unsigned long arg)
402 struct syncppp *ap = chan->private;
405 void __user *argp = (void __user *)arg;
406 u32 __user *p = argp;
411 val = ap->flags | ap->rbits;
412 if (put_user(val, (int __user *) argp))
417 if (get_user(val, (int __user *) argp))
419 ap->flags = val & ~SC_RCV_BITS;
420 spin_lock_irq(&ap->recv_lock);
421 ap->rbits = val & SC_RCV_BITS;
422 spin_unlock_irq(&ap->recv_lock);
426 case PPPIOCGASYNCMAP:
427 if (put_user(ap->xaccm[0], p))
431 case PPPIOCSASYNCMAP:
432 if (get_user(ap->xaccm[0], p))
437 case PPPIOCGRASYNCMAP:
438 if (put_user(ap->raccm, p))
442 case PPPIOCSRASYNCMAP:
443 if (get_user(ap->raccm, p))
448 case PPPIOCGXASYNCMAP:
449 if (copy_to_user(argp, ap->xaccm, sizeof(ap->xaccm)))
453 case PPPIOCSXASYNCMAP:
454 if (copy_from_user(accm, argp, sizeof(accm)))
456 accm[2] &= ~0x40000000U; /* can't escape 0x5e */
457 accm[3] |= 0x60000000U; /* must escape 0x7d, 0x7e */
458 memcpy(ap->xaccm, accm, sizeof(ap->xaccm));
463 if (put_user(ap->mru, (int __user *) argp))
468 if (get_user(val, (int __user *) argp))
483 * This is called at softirq level to deliver received packets
484 * to the ppp_generic code, and to tell the ppp_generic code
485 * if we can accept more output now.
487 static void ppp_sync_process(unsigned long arg)
489 struct syncppp *ap = (struct syncppp *) arg;
492 /* process received packets */
493 while ((skb = skb_dequeue(&ap->rqueue)) != NULL) {
495 /* zero length buffers indicate error */
496 ppp_input_error(&ap->chan, 0);
500 ppp_input(&ap->chan, skb);
503 /* try to push more stuff out */
504 if (test_bit(XMIT_WAKEUP, &ap->xmit_flags) && ppp_sync_push(ap))
505 ppp_output_wakeup(&ap->chan);
509 * Procedures for encapsulation and framing.
512 static struct sk_buff*
513 ppp_sync_txmunge(struct syncppp *ap, struct sk_buff *skb)
520 proto = get_unaligned_be16(data);
522 /* LCP packets with codes between 1 (configure-request)
523 * and 7 (code-reject) must be sent as though no options
524 * have been negotiated.
526 islcp = proto == PPP_LCP && 1 <= data[2] && data[2] <= 7;
528 /* compress protocol field if option enabled */
529 if (data[0] == 0 && (ap->flags & SC_COMP_PROT) && !islcp)
532 /* prepend address/control fields if necessary */
533 if ((ap->flags & SC_COMP_AC) == 0 || islcp) {
534 if (skb_headroom(skb) < 2) {
535 struct sk_buff *npkt = dev_alloc_skb(skb->len + 2);
541 skb_copy_from_linear_data(skb,
542 skb_put(npkt, skb->len), skb->len);
547 skb->data[0] = PPP_ALLSTATIONS;
548 skb->data[1] = PPP_UI;
551 ap->last_xmit = jiffies;
553 if (skb && ap->flags & SC_LOG_OUTPKT)
554 ppp_print_buffer ("send buffer", skb->data, skb->len);
560 * Transmit-side routines.
564 * Send a packet to the peer over an sync tty line.
565 * Returns 1 iff the packet was accepted.
566 * If the packet was not accepted, we will call ppp_output_wakeup
567 * at some later time.
570 ppp_sync_send(struct ppp_channel *chan, struct sk_buff *skb)
572 struct syncppp *ap = chan->private;
576 if (test_and_set_bit(XMIT_FULL, &ap->xmit_flags))
577 return 0; /* already full */
578 skb = ppp_sync_txmunge(ap, skb);
582 clear_bit(XMIT_FULL, &ap->xmit_flags);
589 * Push as much data as possible out to the tty.
592 ppp_sync_push(struct syncppp *ap)
595 struct tty_struct *tty = ap->tty;
598 if (!spin_trylock_bh(&ap->xmit_lock))
601 if (test_and_clear_bit(XMIT_WAKEUP, &ap->xmit_flags))
603 if (!tty_stuffed && ap->tpkt) {
604 set_bit(TTY_DO_WRITE_WAKEUP, &tty->flags);
605 sent = tty->ops->write(tty, ap->tpkt->data, ap->tpkt->len);
607 goto flush; /* error, e.g. loss of CD */
608 if (sent < ap->tpkt->len) {
611 consume_skb(ap->tpkt);
613 clear_bit(XMIT_FULL, &ap->xmit_flags);
618 /* haven't made any progress */
619 spin_unlock_bh(&ap->xmit_lock);
620 if (!(test_bit(XMIT_WAKEUP, &ap->xmit_flags) ||
621 (!tty_stuffed && ap->tpkt)))
623 if (!spin_trylock_bh(&ap->xmit_lock))
632 clear_bit(XMIT_FULL, &ap->xmit_flags);
635 spin_unlock_bh(&ap->xmit_lock);
640 * Flush output from our internal buffers.
641 * Called for the TCFLSH ioctl.
644 ppp_sync_flush_output(struct syncppp *ap)
648 spin_lock_bh(&ap->xmit_lock);
649 if (ap->tpkt != NULL) {
652 clear_bit(XMIT_FULL, &ap->xmit_flags);
655 spin_unlock_bh(&ap->xmit_lock);
657 ppp_output_wakeup(&ap->chan);
661 * Receive-side routines.
664 /* called when the tty driver has data for us.
666 * Data is frame oriented: each call to ppp_sync_input is considered
667 * a whole frame. If the 1st flag byte is non-zero then the whole
668 * frame is considered to be in error and is tossed.
671 ppp_sync_input(struct syncppp *ap, const unsigned char *buf,
672 char *flags, int count)
680 if (ap->flags & SC_LOG_INPKT)
681 ppp_print_buffer ("receive buffer", buf, count);
683 /* stuff the chars in the skb */
684 skb = dev_alloc_skb(ap->mru + PPP_HDRLEN + 2);
686 printk(KERN_ERR "PPPsync: no memory (input pkt)\n");
689 /* Try to get the payload 4-byte aligned */
690 if (buf[0] != PPP_ALLSTATIONS)
691 skb_reserve(skb, 2 + (buf[0] & 1));
693 if (flags && *flags) {
694 /* error flag set, ignore frame */
696 } else if (count > skb_tailroom(skb)) {
697 /* packet overflowed MRU */
701 skb_put_data(skb, buf, count);
703 /* strip address/control field if present */
705 if (p[0] == PPP_ALLSTATIONS && p[1] == PPP_UI) {
706 /* chop off address/control */
709 p = skb_pull(skb, 2);
712 /* PPP packet length should be >= 2 bytes when protocol field is not
715 if (!(p[0] & 0x01) && skb->len < 2)
718 /* queue the frame to be processed */
719 skb_queue_tail(&ap->rqueue, skb);
723 /* queue zero length packet as error indication */
724 if (skb || (skb = dev_alloc_skb(0))) {
726 skb_queue_tail(&ap->rqueue, skb);
731 ppp_sync_cleanup(void)
733 if (tty_unregister_ldisc(N_SYNC_PPP) != 0)
734 printk(KERN_ERR "failed to unregister Sync PPP line discipline\n");
737 module_init(ppp_sync_init);
738 module_exit(ppp_sync_cleanup);
739 MODULE_LICENSE("GPL");
740 MODULE_ALIAS_LDISC(N_SYNC_PPP);