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/if_ppp.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/slab.h>
48 #include <asm/unaligned.h>
49 #include <asm/uaccess.h>
51 #define PPP_VERSION "2.4.2"
53 /* Structure for storing local state. */
55 struct tty_struct *tty;
61 unsigned long xmit_flags;
64 unsigned int bytes_sent;
65 unsigned int bytes_rcvd;
68 unsigned long last_xmit;
70 struct sk_buff_head rqueue;
72 struct tasklet_struct tsk;
75 struct completion dead_cmp;
76 struct ppp_channel chan; /* interface to generic ppp layer */
79 /* Bit numbers in xmit_flags */
84 #define SC_RCV_BITS (SC_RCV_B7_1|SC_RCV_B7_0|SC_RCV_ODDP|SC_RCV_EVNP)
86 #define PPPSYNC_MAX_RQLEN 32 /* arbitrary */
91 static struct sk_buff* ppp_sync_txmunge(struct syncppp *ap, struct sk_buff *);
92 static int ppp_sync_send(struct ppp_channel *chan, struct sk_buff *skb);
93 static int ppp_sync_ioctl(struct ppp_channel *chan, unsigned int cmd,
95 static void ppp_sync_process(unsigned long arg);
96 static int ppp_sync_push(struct syncppp *ap);
97 static void ppp_sync_flush_output(struct syncppp *ap);
98 static void ppp_sync_input(struct syncppp *ap, const unsigned char *buf,
99 char *flags, int count);
101 static const struct ppp_channel_ops sync_ops = {
102 .start_xmit = ppp_sync_send,
103 .ioctl = ppp_sync_ioctl,
107 * Utility procedures to print a buffer in hex/ascii
110 ppp_print_hex (register __u8 * out, const __u8 * in, int count)
112 register __u8 next_ch;
113 static const char hex[] = "0123456789ABCDEF";
115 while (count-- > 0) {
117 *out++ = hex[(next_ch >> 4) & 0x0F];
118 *out++ = hex[next_ch & 0x0F];
124 ppp_print_char (register __u8 * out, const __u8 * in, int count)
126 register __u8 next_ch;
128 while (count-- > 0) {
131 if (next_ch < 0x20 || next_ch > 0x7e)
135 if (next_ch == '%') /* printk/syslogd has a bug !! */
143 ppp_print_buffer (const char *name, const __u8 *buf, int count)
148 printk(KERN_DEBUG "ppp_synctty: %s, count = %d\n", name, count);
151 memset (line, 32, 44);
152 ppp_print_hex (line, buf, 8);
153 ppp_print_char (&line[8 * 3], buf, 8);
154 printk(KERN_DEBUG "%s\n", line);
160 memset (line, 32, 44);
161 ppp_print_hex (line, buf, count);
162 ppp_print_char (&line[8 * 3], buf, count);
163 printk(KERN_DEBUG "%s\n", line);
169 * Routines implementing the synchronous PPP line discipline.
173 * We have a potential race on dereferencing tty->disc_data,
174 * because the tty layer provides no locking at all - thus one
175 * cpu could be running ppp_synctty_receive while another
176 * calls ppp_synctty_close, which zeroes tty->disc_data and
177 * frees the memory that ppp_synctty_receive is using. The best
178 * way to fix this is to use a rwlock in the tty struct, but for now
179 * we use a single global rwlock for all ttys in ppp line discipline.
181 * FIXME: Fixed in tty_io nowadays.
183 static DEFINE_RWLOCK(disc_data_lock);
185 static struct syncppp *sp_get(struct tty_struct *tty)
189 read_lock(&disc_data_lock);
192 atomic_inc(&ap->refcnt);
193 read_unlock(&disc_data_lock);
197 static void sp_put(struct syncppp *ap)
199 if (atomic_dec_and_test(&ap->refcnt))
200 complete(&ap->dead_cmp);
204 * Called when a tty is put into sync-PPP line discipline.
207 ppp_sync_open(struct tty_struct *tty)
213 if (tty->ops->write == NULL)
216 ap = kzalloc(sizeof(*ap), GFP_KERNEL);
221 /* initialize the syncppp structure */
224 spin_lock_init(&ap->xmit_lock);
225 spin_lock_init(&ap->recv_lock);
227 ap->xaccm[3] = 0x60000000U;
230 skb_queue_head_init(&ap->rqueue);
231 tasklet_init(&ap->tsk, ppp_sync_process, (unsigned long) ap);
233 atomic_set(&ap->refcnt, 1);
234 init_completion(&ap->dead_cmp);
236 ap->chan.private = ap;
237 ap->chan.ops = &sync_ops;
238 ap->chan.mtu = PPP_MRU;
239 ap->chan.hdrlen = 2; /* for A/C bytes */
240 speed = tty_get_baud_rate(tty);
241 ap->chan.speed = speed;
242 err = ppp_register_channel(&ap->chan);
247 tty->receive_room = 65536;
257 * Called when the tty is put into another line discipline
258 * or it hangs up. We have to wait for any cpu currently
259 * executing in any of the other ppp_synctty_* routines to
260 * finish before we can call ppp_unregister_channel and free
261 * the syncppp struct. This routine must be called from
262 * process context, not interrupt or softirq context.
265 ppp_sync_close(struct tty_struct *tty)
269 write_lock_irq(&disc_data_lock);
271 tty->disc_data = NULL;
272 write_unlock_irq(&disc_data_lock);
277 * We have now ensured that nobody can start using ap from now
278 * on, but we have to wait for all existing users to finish.
279 * Note that ppp_unregister_channel ensures that no calls to
280 * our channel ops (i.e. ppp_sync_send/ioctl) are in progress
281 * by the time it returns.
283 if (!atomic_dec_and_test(&ap->refcnt))
284 wait_for_completion(&ap->dead_cmp);
285 tasklet_kill(&ap->tsk);
287 ppp_unregister_channel(&ap->chan);
288 skb_queue_purge(&ap->rqueue);
294 * Called on tty hangup in process context.
296 * Wait for I/O to driver to complete and unregister PPP channel.
297 * This is already done by the close routine, so just call that.
299 static int ppp_sync_hangup(struct tty_struct *tty)
306 * Read does nothing - no data is ever available this way.
307 * Pppd reads and writes packets via /dev/ppp instead.
310 ppp_sync_read(struct tty_struct *tty, struct file *file,
311 unsigned char __user *buf, size_t count)
317 * Write on the tty does nothing, the packets all come in
318 * from the ppp generic stuff.
321 ppp_sync_write(struct tty_struct *tty, struct file *file,
322 const unsigned char *buf, size_t count)
328 ppp_synctty_ioctl(struct tty_struct *tty, struct file *file,
329 unsigned int cmd, unsigned long arg)
331 struct syncppp *ap = sp_get(tty);
332 int __user *p = (int __user *)arg;
341 if (put_user(ppp_channel_index(&ap->chan), p))
348 if (put_user(ppp_unit_number(&ap->chan), p))
354 /* flush our buffers and the serial port's buffer */
355 if (arg == TCIOFLUSH || arg == TCOFLUSH)
356 ppp_sync_flush_output(ap);
357 err = tty_perform_flush(tty, arg);
362 if (put_user(val, p))
368 err = tty_mode_ioctl(tty, file, cmd, arg);
376 /* No kernel lock - fine */
378 ppp_sync_poll(struct tty_struct *tty, struct file *file, poll_table *wait)
383 /* May sleep, don't call from interrupt level or with interrupts disabled */
385 ppp_sync_receive(struct tty_struct *tty, const unsigned char *buf,
386 char *cflags, int count)
388 struct syncppp *ap = sp_get(tty);
393 spin_lock_irqsave(&ap->recv_lock, flags);
394 ppp_sync_input(ap, buf, cflags, count);
395 spin_unlock_irqrestore(&ap->recv_lock, flags);
396 if (!skb_queue_empty(&ap->rqueue))
397 tasklet_schedule(&ap->tsk);
405 ppp_sync_wakeup(struct tty_struct *tty)
407 struct syncppp *ap = sp_get(tty);
409 clear_bit(TTY_DO_WRITE_WAKEUP, &tty->flags);
412 set_bit(XMIT_WAKEUP, &ap->xmit_flags);
413 tasklet_schedule(&ap->tsk);
418 static struct tty_ldisc_ops ppp_sync_ldisc = {
419 .owner = THIS_MODULE,
420 .magic = TTY_LDISC_MAGIC,
422 .open = ppp_sync_open,
423 .close = ppp_sync_close,
424 .hangup = ppp_sync_hangup,
425 .read = ppp_sync_read,
426 .write = ppp_sync_write,
427 .ioctl = ppp_synctty_ioctl,
428 .poll = ppp_sync_poll,
429 .receive_buf = ppp_sync_receive,
430 .write_wakeup = ppp_sync_wakeup,
438 err = tty_register_ldisc(N_SYNC_PPP, &ppp_sync_ldisc);
440 printk(KERN_ERR "PPP_sync: error %d registering line disc.\n",
446 * The following routines provide the PPP channel interface.
449 ppp_sync_ioctl(struct ppp_channel *chan, unsigned int cmd, unsigned long arg)
451 struct syncppp *ap = chan->private;
454 void __user *argp = (void __user *)arg;
455 u32 __user *p = argp;
460 val = ap->flags | ap->rbits;
461 if (put_user(val, (int __user *) argp))
466 if (get_user(val, (int __user *) argp))
468 ap->flags = val & ~SC_RCV_BITS;
469 spin_lock_irq(&ap->recv_lock);
470 ap->rbits = val & SC_RCV_BITS;
471 spin_unlock_irq(&ap->recv_lock);
475 case PPPIOCGASYNCMAP:
476 if (put_user(ap->xaccm[0], p))
480 case PPPIOCSASYNCMAP:
481 if (get_user(ap->xaccm[0], p))
486 case PPPIOCGRASYNCMAP:
487 if (put_user(ap->raccm, p))
491 case PPPIOCSRASYNCMAP:
492 if (get_user(ap->raccm, p))
497 case PPPIOCGXASYNCMAP:
498 if (copy_to_user(argp, ap->xaccm, sizeof(ap->xaccm)))
502 case PPPIOCSXASYNCMAP:
503 if (copy_from_user(accm, argp, sizeof(accm)))
505 accm[2] &= ~0x40000000U; /* can't escape 0x5e */
506 accm[3] |= 0x60000000U; /* must escape 0x7d, 0x7e */
507 memcpy(ap->xaccm, accm, sizeof(ap->xaccm));
512 if (put_user(ap->mru, (int __user *) argp))
517 if (get_user(val, (int __user *) argp))
532 * This is called at softirq level to deliver received packets
533 * to the ppp_generic code, and to tell the ppp_generic code
534 * if we can accept more output now.
536 static void ppp_sync_process(unsigned long arg)
538 struct syncppp *ap = (struct syncppp *) arg;
541 /* process received packets */
542 while ((skb = skb_dequeue(&ap->rqueue)) != NULL) {
544 /* zero length buffers indicate error */
545 ppp_input_error(&ap->chan, 0);
549 ppp_input(&ap->chan, skb);
552 /* try to push more stuff out */
553 if (test_bit(XMIT_WAKEUP, &ap->xmit_flags) && ppp_sync_push(ap))
554 ppp_output_wakeup(&ap->chan);
558 * Procedures for encapsulation and framing.
561 static struct sk_buff*
562 ppp_sync_txmunge(struct syncppp *ap, struct sk_buff *skb)
569 proto = get_unaligned_be16(data);
571 /* LCP packets with codes between 1 (configure-request)
572 * and 7 (code-reject) must be sent as though no options
573 * have been negotiated.
575 islcp = proto == PPP_LCP && 1 <= data[2] && data[2] <= 7;
577 /* compress protocol field if option enabled */
578 if (data[0] == 0 && (ap->flags & SC_COMP_PROT) && !islcp)
581 /* prepend address/control fields if necessary */
582 if ((ap->flags & SC_COMP_AC) == 0 || islcp) {
583 if (skb_headroom(skb) < 2) {
584 struct sk_buff *npkt = dev_alloc_skb(skb->len + 2);
590 skb_copy_from_linear_data(skb,
591 skb_put(npkt, skb->len), skb->len);
596 skb->data[0] = PPP_ALLSTATIONS;
597 skb->data[1] = PPP_UI;
600 ap->last_xmit = jiffies;
602 if (skb && ap->flags & SC_LOG_OUTPKT)
603 ppp_print_buffer ("send buffer", skb->data, skb->len);
609 * Transmit-side routines.
613 * Send a packet to the peer over an sync tty line.
614 * Returns 1 iff the packet was accepted.
615 * If the packet was not accepted, we will call ppp_output_wakeup
616 * at some later time.
619 ppp_sync_send(struct ppp_channel *chan, struct sk_buff *skb)
621 struct syncppp *ap = chan->private;
625 if (test_and_set_bit(XMIT_FULL, &ap->xmit_flags))
626 return 0; /* already full */
627 skb = ppp_sync_txmunge(ap, skb);
631 clear_bit(XMIT_FULL, &ap->xmit_flags);
638 * Push as much data as possible out to the tty.
641 ppp_sync_push(struct syncppp *ap)
644 struct tty_struct *tty = ap->tty;
647 if (!spin_trylock_bh(&ap->xmit_lock))
650 if (test_and_clear_bit(XMIT_WAKEUP, &ap->xmit_flags))
652 if (!tty_stuffed && ap->tpkt) {
653 set_bit(TTY_DO_WRITE_WAKEUP, &tty->flags);
654 sent = tty->ops->write(tty, ap->tpkt->data, ap->tpkt->len);
656 goto flush; /* error, e.g. loss of CD */
657 if (sent < ap->tpkt->len) {
662 clear_bit(XMIT_FULL, &ap->xmit_flags);
667 /* haven't made any progress */
668 spin_unlock_bh(&ap->xmit_lock);
669 if (!(test_bit(XMIT_WAKEUP, &ap->xmit_flags) ||
670 (!tty_stuffed && ap->tpkt)))
672 if (!spin_trylock_bh(&ap->xmit_lock))
681 clear_bit(XMIT_FULL, &ap->xmit_flags);
684 spin_unlock_bh(&ap->xmit_lock);
689 * Flush output from our internal buffers.
690 * Called for the TCFLSH ioctl.
693 ppp_sync_flush_output(struct syncppp *ap)
697 spin_lock_bh(&ap->xmit_lock);
698 if (ap->tpkt != NULL) {
701 clear_bit(XMIT_FULL, &ap->xmit_flags);
704 spin_unlock_bh(&ap->xmit_lock);
706 ppp_output_wakeup(&ap->chan);
710 * Receive-side routines.
713 /* called when the tty driver has data for us.
715 * Data is frame oriented: each call to ppp_sync_input is considered
716 * a whole frame. If the 1st flag byte is non-zero then the whole
717 * frame is considered to be in error and is tossed.
720 ppp_sync_input(struct syncppp *ap, const unsigned char *buf,
721 char *flags, int count)
729 if (ap->flags & SC_LOG_INPKT)
730 ppp_print_buffer ("receive buffer", buf, count);
732 /* stuff the chars in the skb */
733 skb = dev_alloc_skb(ap->mru + PPP_HDRLEN + 2);
735 printk(KERN_ERR "PPPsync: no memory (input pkt)\n");
738 /* Try to get the payload 4-byte aligned */
739 if (buf[0] != PPP_ALLSTATIONS)
740 skb_reserve(skb, 2 + (buf[0] & 1));
742 if (flags && *flags) {
743 /* error flag set, ignore frame */
745 } else if (count > skb_tailroom(skb)) {
746 /* packet overflowed MRU */
750 p = skb_put(skb, count);
751 memcpy(p, buf, count);
753 /* strip address/control field if present */
755 if (p[0] == PPP_ALLSTATIONS && p[1] == PPP_UI) {
756 /* chop off address/control */
759 p = skb_pull(skb, 2);
762 /* decompress protocol field if compressed */
764 /* protocol is compressed */
765 skb_push(skb, 1)[0] = 0;
766 } else if (skb->len < 2)
769 /* queue the frame to be processed */
770 skb_queue_tail(&ap->rqueue, skb);
774 /* queue zero length packet as error indication */
775 if (skb || (skb = dev_alloc_skb(0))) {
777 skb_queue_tail(&ap->rqueue, skb);
782 ppp_sync_cleanup(void)
784 if (tty_unregister_ldisc(N_SYNC_PPP) != 0)
785 printk(KERN_ERR "failed to unregister Sync PPP line discipline\n");
788 module_init(ppp_sync_init);
789 module_exit(ppp_sync_cleanup);
790 MODULE_LICENSE("GPL");
791 MODULE_ALIAS_LDISC(N_SYNC_PPP);