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
);