2 * PPP async serial channel driver for Linux.
4 * Copyright 1999 Paul Mackerras.
6 * This program is free software; you can redistribute it and/or
7 * modify it under the terms of the GNU General Public License
8 * as published by the Free Software Foundation; either version
9 * 2 of the License, or (at your option) any later version.
11 * This driver provides the encapsulation and framing for sending
12 * and receiving PPP frames over async serial lines. It relies on
13 * the generic PPP layer to give it frames to send and to process
14 * received frames. It implements the PPP line discipline.
16 * Part of the code in this driver was inspired by the old async-only
17 * PPP driver, written by Michael Callahan and Al Longyear, and
18 * subsequently hacked by Paul Mackerras.
21 #include <linux/module.h>
22 #include <linux/kernel.h>
23 #include <linux/skbuff.h>
24 #include <linux/tty.h>
25 #include <linux/netdevice.h>
26 #include <linux/poll.h>
27 #include <linux/crc-ccitt.h>
28 #include <linux/ppp_defs.h>
29 #include <linux/if_ppp.h>
30 #include <linux/ppp_channel.h>
31 #include <linux/spinlock.h>
32 #include <linux/init.h>
33 #include <linux/jiffies.h>
34 #include <linux/slab.h>
35 #include <asm/uaccess.h>
36 #include <asm/string.h>
38 #define PPP_VERSION "2.4.2"
42 /* Structure for storing local state. */
44 struct tty_struct *tty;
51 unsigned long xmit_flags;
54 unsigned int bytes_sent;
55 unsigned int bytes_rcvd;
62 unsigned long last_xmit;
66 struct sk_buff_head rqueue;
68 struct tasklet_struct tsk;
71 struct semaphore dead_sem;
72 struct ppp_channel chan; /* interface to generic ppp layer */
73 unsigned char obuf[OBUFSIZE];
76 /* Bit numbers in xmit_flags */
84 #define SC_PREV_ERROR 4
87 #define SC_RCV_BITS (SC_RCV_B7_1|SC_RCV_B7_0|SC_RCV_ODDP|SC_RCV_EVNP)
89 static int flag_time = HZ;
90 module_param(flag_time, int, 0);
91 MODULE_PARM_DESC(flag_time, "ppp_async: interval between flagged packets (in clock ticks)");
92 MODULE_LICENSE("GPL");
93 MODULE_ALIAS_LDISC(N_PPP);
98 static int ppp_async_encode(struct asyncppp *ap);
99 static int ppp_async_send(struct ppp_channel *chan, struct sk_buff *skb);
100 static int ppp_async_push(struct asyncppp *ap);
101 static void ppp_async_flush_output(struct asyncppp *ap);
102 static void ppp_async_input(struct asyncppp *ap, const unsigned char *buf,
103 char *flags, int count);
104 static int ppp_async_ioctl(struct ppp_channel *chan, unsigned int cmd,
106 static void ppp_async_process(unsigned long arg);
108 static void async_lcp_peek(struct asyncppp *ap, unsigned char *data,
109 int len, int inbound);
111 static struct ppp_channel_ops async_ops = {
117 * Routines implementing the PPP line discipline.
121 * We have a potential race on dereferencing tty->disc_data,
122 * because the tty layer provides no locking at all - thus one
123 * cpu could be running ppp_asynctty_receive while another
124 * calls ppp_asynctty_close, which zeroes tty->disc_data and
125 * frees the memory that ppp_asynctty_receive is using. The best
126 * way to fix this is to use a rwlock in the tty struct, but for now
127 * we use a single global rwlock for all ttys in ppp line discipline.
129 * FIXME: this is no longer true. The _close path for the ldisc is
130 * now guaranteed to be sane.
132 static DEFINE_RWLOCK(disc_data_lock);
134 static struct asyncppp *ap_get(struct tty_struct *tty)
138 read_lock(&disc_data_lock);
141 atomic_inc(&ap->refcnt);
142 read_unlock(&disc_data_lock);
146 static void ap_put(struct asyncppp *ap)
148 if (atomic_dec_and_test(&ap->refcnt))
153 * Called when a tty is put into PPP line discipline. Called in process
157 ppp_asynctty_open(struct tty_struct *tty)
163 if (tty->ops->write == NULL)
167 ap = kzalloc(sizeof(*ap), GFP_KERNEL);
171 /* initialize the asyncppp structure */
174 spin_lock_init(&ap->xmit_lock);
175 spin_lock_init(&ap->recv_lock);
177 ap->xaccm[3] = 0x60000000U;
183 skb_queue_head_init(&ap->rqueue);
184 tasklet_init(&ap->tsk, ppp_async_process, (unsigned long) ap);
186 atomic_set(&ap->refcnt, 1);
187 init_MUTEX_LOCKED(&ap->dead_sem);
189 ap->chan.private = ap;
190 ap->chan.ops = &async_ops;
191 ap->chan.mtu = PPP_MRU;
192 speed = tty_get_baud_rate(tty);
193 ap->chan.speed = speed;
194 err = ppp_register_channel(&ap->chan);
199 tty->receive_room = 65536;
209 * Called when the tty is put into another line discipline
210 * or it hangs up. We have to wait for any cpu currently
211 * executing in any of the other ppp_asynctty_* routines to
212 * finish before we can call ppp_unregister_channel and free
213 * the asyncppp struct. This routine must be called from
214 * process context, not interrupt or softirq context.
217 ppp_asynctty_close(struct tty_struct *tty)
221 write_lock_irq(&disc_data_lock);
223 tty->disc_data = NULL;
224 write_unlock_irq(&disc_data_lock);
229 * We have now ensured that nobody can start using ap from now
230 * on, but we have to wait for all existing users to finish.
231 * Note that ppp_unregister_channel ensures that no calls to
232 * our channel ops (i.e. ppp_async_send/ioctl) are in progress
233 * by the time it returns.
235 if (!atomic_dec_and_test(&ap->refcnt))
237 tasklet_kill(&ap->tsk);
239 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_asynctty_hangup(struct tty_struct *tty)
254 ppp_asynctty_close(tty);
259 * Read does nothing - no data is ever available this way.
260 * Pppd reads and writes packets via /dev/ppp instead.
263 ppp_asynctty_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_asynctty_write(struct tty_struct *tty, struct file *file,
275 const unsigned char *buf, size_t count)
281 * Called in process context only. May be re-entered by multiple
282 * ioctl calling threads.
286 ppp_asynctty_ioctl(struct tty_struct *tty, struct file *file,
287 unsigned int cmd, unsigned long arg)
289 struct asyncppp *ap = ap_get(tty);
291 int __user *p = (int __user *)arg;
299 if (put_user(ppp_channel_index(&ap->chan), p))
306 if (put_user(ppp_unit_number(&ap->chan), p))
312 /* flush our buffers and the serial port's buffer */
313 if (arg == TCIOFLUSH || arg == TCOFLUSH)
314 ppp_async_flush_output(ap);
315 err = tty_perform_flush(tty, arg);
320 if (put_user(val, p))
326 /* Try the various mode ioctls */
327 err = tty_mode_ioctl(tty, file, cmd, arg);
334 /* No kernel lock - fine */
336 ppp_asynctty_poll(struct tty_struct *tty, struct file *file, poll_table *wait)
341 /* May sleep, don't call from interrupt level or with interrupts disabled */
343 ppp_asynctty_receive(struct tty_struct *tty, const unsigned char *buf,
344 char *cflags, int count)
346 struct asyncppp *ap = ap_get(tty);
351 spin_lock_irqsave(&ap->recv_lock, flags);
352 ppp_async_input(ap, buf, cflags, count);
353 spin_unlock_irqrestore(&ap->recv_lock, flags);
354 if (!skb_queue_empty(&ap->rqueue))
355 tasklet_schedule(&ap->tsk);
361 ppp_asynctty_wakeup(struct tty_struct *tty)
363 struct asyncppp *ap = ap_get(tty);
365 clear_bit(TTY_DO_WRITE_WAKEUP, &tty->flags);
368 set_bit(XMIT_WAKEUP, &ap->xmit_flags);
369 tasklet_schedule(&ap->tsk);
374 static struct tty_ldisc_ops ppp_ldisc = {
375 .owner = THIS_MODULE,
376 .magic = TTY_LDISC_MAGIC,
378 .open = ppp_asynctty_open,
379 .close = ppp_asynctty_close,
380 .hangup = ppp_asynctty_hangup,
381 .read = ppp_asynctty_read,
382 .write = ppp_asynctty_write,
383 .ioctl = ppp_asynctty_ioctl,
384 .poll = ppp_asynctty_poll,
385 .receive_buf = ppp_asynctty_receive,
386 .write_wakeup = ppp_asynctty_wakeup,
394 err = tty_register_ldisc(N_PPP, &ppp_ldisc);
396 printk(KERN_ERR "PPP_async: error %d registering line disc.\n",
402 * The following routines provide the PPP channel interface.
405 ppp_async_ioctl(struct ppp_channel *chan, unsigned int cmd, unsigned long arg)
407 struct asyncppp *ap = chan->private;
408 void __user *argp = (void __user *)arg;
409 int __user *p = argp;
416 val = ap->flags | ap->rbits;
417 if (put_user(val, p))
422 if (get_user(val, p))
424 ap->flags = val & ~SC_RCV_BITS;
425 spin_lock_irq(&ap->recv_lock);
426 ap->rbits = val & SC_RCV_BITS;
427 spin_unlock_irq(&ap->recv_lock);
431 case PPPIOCGASYNCMAP:
432 if (put_user(ap->xaccm[0], (u32 __user *)argp))
436 case PPPIOCSASYNCMAP:
437 if (get_user(ap->xaccm[0], (u32 __user *)argp))
442 case PPPIOCGRASYNCMAP:
443 if (put_user(ap->raccm, (u32 __user *)argp))
447 case PPPIOCSRASYNCMAP:
448 if (get_user(ap->raccm, (u32 __user *)argp))
453 case PPPIOCGXASYNCMAP:
454 if (copy_to_user(argp, ap->xaccm, sizeof(ap->xaccm)))
458 case PPPIOCSXASYNCMAP:
459 if (copy_from_user(accm, argp, sizeof(accm)))
461 accm[2] &= ~0x40000000U; /* can't escape 0x5e */
462 accm[3] |= 0x60000000U; /* must escape 0x7d, 0x7e */
463 memcpy(ap->xaccm, accm, sizeof(ap->xaccm));
468 if (put_user(ap->mru, p))
473 if (get_user(val, p))
489 * This is called at softirq level to deliver received packets
490 * to the ppp_generic code, and to tell the ppp_generic code
491 * if we can accept more output now.
493 static void ppp_async_process(unsigned long arg)
495 struct asyncppp *ap = (struct asyncppp *) arg;
498 /* process received packets */
499 while ((skb = skb_dequeue(&ap->rqueue)) != NULL) {
501 ppp_input_error(&ap->chan, 0);
502 ppp_input(&ap->chan, skb);
505 /* try to push more stuff out */
506 if (test_bit(XMIT_WAKEUP, &ap->xmit_flags) && ppp_async_push(ap))
507 ppp_output_wakeup(&ap->chan);
511 * Procedures for encapsulation and framing.
515 * Procedure to encode the data for async serial transmission.
516 * Does octet stuffing (escaping), puts the address/control bytes
517 * on if A/C compression is disabled, and does protocol compression.
518 * Assumes ap->tpkt != 0 on entry.
519 * Returns 1 if we finished the current frame, 0 otherwise.
522 #define PUT_BYTE(ap, buf, c, islcp) do { \
523 if ((islcp && c < 0x20) || (ap->xaccm[c >> 5] & (1 << (c & 0x1f)))) {\
524 *buf++ = PPP_ESCAPE; \
531 ppp_async_encode(struct asyncppp *ap)
533 int fcs, i, count, c, proto;
534 unsigned char *buf, *buflim;
542 data = ap->tpkt->data;
543 count = ap->tpkt->len;
545 proto = (data[0] << 8) + data[1];
548 * LCP packets with code values between 1 (configure-reqest)
549 * and 7 (code-reject) must be sent as though no options
550 * had been negotiated.
552 islcp = proto == PPP_LCP && 1 <= data[2] && data[2] <= 7;
556 async_lcp_peek(ap, data, count, 0);
559 * Start of a new packet - insert the leading FLAG
560 * character if necessary.
562 if (islcp || flag_time == 0 ||
563 time_after_eq(jiffies, ap->last_xmit + flag_time))
565 ap->last_xmit = jiffies;
569 * Put in the address/control bytes if necessary
571 if ((ap->flags & SC_COMP_AC) == 0 || islcp) {
572 PUT_BYTE(ap, buf, 0xff, islcp);
573 fcs = PPP_FCS(fcs, 0xff);
574 PUT_BYTE(ap, buf, 0x03, islcp);
575 fcs = PPP_FCS(fcs, 0x03);
580 * Once we put in the last byte, we need to put in the FCS
581 * and closing flag, so make sure there is at least 7 bytes
582 * of free space in the output buffer.
584 buflim = ap->obuf + OBUFSIZE - 6;
585 while (i < count && buf < buflim) {
587 if (i == 1 && c == 0 && (ap->flags & SC_COMP_PROT))
588 continue; /* compress protocol field */
589 fcs = PPP_FCS(fcs, c);
590 PUT_BYTE(ap, buf, c, islcp);
595 * Remember where we are up to in this packet.
604 * We have finished the packet. Add the FCS and flag.
608 PUT_BYTE(ap, buf, c, islcp);
609 c = (fcs >> 8) & 0xff;
610 PUT_BYTE(ap, buf, c, islcp);
620 * Transmit-side routines.
624 * Send a packet to the peer over an async tty line.
625 * Returns 1 iff the packet was accepted.
626 * If the packet was not accepted, we will call ppp_output_wakeup
627 * at some later time.
630 ppp_async_send(struct ppp_channel *chan, struct sk_buff *skb)
632 struct asyncppp *ap = chan->private;
636 if (test_and_set_bit(XMIT_FULL, &ap->xmit_flags))
637 return 0; /* already full */
646 * Push as much data as possible out to the tty.
649 ppp_async_push(struct asyncppp *ap)
651 int avail, sent, done = 0;
652 struct tty_struct *tty = ap->tty;
656 * We can get called recursively here if the tty write
657 * function calls our wakeup function. This can happen
658 * for example on a pty with both the master and slave
659 * set to PPP line discipline.
660 * We use the XMIT_BUSY bit to detect this and get out,
661 * leaving the XMIT_WAKEUP bit set to tell the other
662 * instance that it may now be able to write more now.
664 if (test_and_set_bit(XMIT_BUSY, &ap->xmit_flags))
666 spin_lock_bh(&ap->xmit_lock);
668 if (test_and_clear_bit(XMIT_WAKEUP, &ap->xmit_flags))
670 if (!tty_stuffed && ap->optr < ap->olim) {
671 avail = ap->olim - ap->optr;
672 set_bit(TTY_DO_WRITE_WAKEUP, &tty->flags);
673 sent = tty->ops->write(tty, ap->optr, avail);
675 goto flush; /* error, e.g. loss of CD */
681 if (ap->optr >= ap->olim && ap->tpkt) {
682 if (ppp_async_encode(ap)) {
683 /* finished processing ap->tpkt */
684 clear_bit(XMIT_FULL, &ap->xmit_flags);
690 * We haven't made any progress this time around.
691 * Clear XMIT_BUSY to let other callers in, but
692 * after doing so we have to check if anyone set
693 * XMIT_WAKEUP since we last checked it. If they
694 * did, we should try again to set XMIT_BUSY and go
695 * around again in case XMIT_BUSY was still set when
696 * the other caller tried.
698 clear_bit(XMIT_BUSY, &ap->xmit_flags);
699 /* any more work to do? if not, exit the loop */
700 if (!(test_bit(XMIT_WAKEUP, &ap->xmit_flags) ||
701 (!tty_stuffed && ap->tpkt)))
703 /* more work to do, see if we can do it now */
704 if (test_and_set_bit(XMIT_BUSY, &ap->xmit_flags))
707 spin_unlock_bh(&ap->xmit_lock);
711 clear_bit(XMIT_BUSY, &ap->xmit_flags);
715 clear_bit(XMIT_FULL, &ap->xmit_flags);
719 spin_unlock_bh(&ap->xmit_lock);
724 * Flush output from our internal buffers.
725 * Called for the TCFLSH ioctl. Can be entered in parallel
726 * but this is covered by the xmit_lock.
729 ppp_async_flush_output(struct asyncppp *ap)
733 spin_lock_bh(&ap->xmit_lock);
735 if (ap->tpkt != NULL) {
738 clear_bit(XMIT_FULL, &ap->xmit_flags);
741 spin_unlock_bh(&ap->xmit_lock);
743 ppp_output_wakeup(&ap->chan);
747 * Receive-side routines.
750 /* see how many ordinary chars there are at the start of buf */
752 scan_ordinary(struct asyncppp *ap, const unsigned char *buf, int count)
756 for (i = 0; i < count; ++i) {
758 if (c == PPP_ESCAPE || c == PPP_FLAG ||
759 (c < 0x20 && (ap->raccm & (1 << c)) != 0))
765 /* called when a flag is seen - do end-of-packet processing */
767 process_input_packet(struct asyncppp *ap)
771 unsigned int len, fcs, proto;
774 if (ap->state & (SC_TOSS | SC_ESCAPE))
778 return; /* 0-length packet */
784 goto err; /* too short */
786 for (; len > 0; --len)
787 fcs = PPP_FCS(fcs, *p++);
788 if (fcs != PPP_GOODFCS)
789 goto err; /* bad FCS */
790 skb_trim(skb, skb->len - 2);
792 /* check for address/control and protocol compression */
794 if (p[0] == PPP_ALLSTATIONS) {
795 /* chop off address/control */
796 if (p[1] != PPP_UI || skb->len < 3)
798 p = skb_pull(skb, 2);
802 /* protocol is compressed */
803 skb_push(skb, 1)[0] = 0;
807 proto = (proto << 8) + p[1];
808 if (proto == PPP_LCP)
809 async_lcp_peek(ap, p, skb->len, 1);
812 /* queue the frame to be processed */
813 skb->cb[0] = ap->state;
814 skb_queue_tail(&ap->rqueue, skb);
820 /* frame had an error, remember that, reset SC_TOSS & SC_ESCAPE */
821 ap->state = SC_PREV_ERROR;
823 /* make skb appear as freshly allocated */
825 skb_reserve(skb, - skb_headroom(skb));
829 /* Called when the tty driver has data for us. Runs parallel with the
830 other ldisc functions but will not be re-entered */
833 ppp_async_input(struct asyncppp *ap, const unsigned char *buf,
834 char *flags, int count)
837 int c, i, j, n, s, f;
840 /* update bits used for 8-bit cleanness detection */
841 if (~ap->rbits & SC_RCV_BITS) {
843 for (i = 0; i < count; ++i) {
845 if (flags && flags[i] != 0)
847 s |= (c & 0x80)? SC_RCV_B7_1: SC_RCV_B7_0;
848 c = ((c >> 4) ^ c) & 0xf;
849 s |= (0x6996 & (1 << c))? SC_RCV_ODDP: SC_RCV_EVNP;
855 /* scan through and see how many chars we can do in bulk */
856 if ((ap->state & SC_ESCAPE) && buf[0] == PPP_ESCAPE)
859 n = scan_ordinary(ap, buf, count);
862 if (flags && (ap->state & SC_TOSS) == 0) {
863 /* check the flags to see if any char had an error */
864 for (j = 0; j < n; ++j)
865 if ((f = flags[j]) != 0)
870 ap->state |= SC_TOSS;
872 } else if (n > 0 && (ap->state & SC_TOSS) == 0) {
873 /* stuff the chars in the skb */
876 skb = dev_alloc_skb(ap->mru + PPP_HDRLEN + 2);
882 /* Try to get the payload 4-byte aligned.
883 * This should match the
884 * PPP_ALLSTATIONS/PPP_UI/compressed tests in
885 * process_input_packet, but we do not have
886 * enough chars here to test buf[1] and buf[2].
888 if (buf[0] != PPP_ALLSTATIONS)
889 skb_reserve(skb, 2 + (buf[0] & 1));
891 if (n > skb_tailroom(skb)) {
892 /* packet overflowed MRU */
893 ap->state |= SC_TOSS;
895 sp = skb_put(skb, n);
897 if (ap->state & SC_ESCAPE) {
899 ap->state &= ~SC_ESCAPE;
908 if (flags != NULL && flags[n] != 0) {
909 ap->state |= SC_TOSS;
910 } else if (c == PPP_FLAG) {
911 process_input_packet(ap);
912 } else if (c == PPP_ESCAPE) {
913 ap->state |= SC_ESCAPE;
914 } else if (I_IXON(ap->tty)) {
915 if (c == START_CHAR(ap->tty))
917 else if (c == STOP_CHAR(ap->tty))
920 /* otherwise it's a char in the recv ACCM */
931 printk(KERN_ERR "PPPasync: no memory (input pkt)\n");
932 ap->state |= SC_TOSS;
936 * We look at LCP frames going past so that we can notice
937 * and react to the LCP configure-ack from the peer.
938 * In the situation where the peer has been sent a configure-ack
939 * already, LCP is up once it has sent its configure-ack
940 * so the immediately following packet can be sent with the
941 * configured LCP options. This allows us to process the following
942 * packet correctly without pppd needing to respond quickly.
944 * We only respond to the received configure-ack if we have just
945 * sent a configure-request, and the configure-ack contains the
946 * same data (this is checked using a 16-bit crc of the data).
948 #define CONFREQ 1 /* LCP code field values */
950 #define LCP_MRU 1 /* LCP option numbers */
951 #define LCP_ASYNCMAP 2
953 static void async_lcp_peek(struct asyncppp *ap, unsigned char *data,
954 int len, int inbound)
956 int dlen, fcs, i, code;
959 data += 2; /* skip protocol bytes */
961 if (len < 4) /* 4 = code, ID, length */
964 if (code != CONFACK && code != CONFREQ)
966 dlen = (data[2] << 8) + data[3];
968 return; /* packet got truncated or length is bogus */
970 if (code == (inbound? CONFACK: CONFREQ)) {
972 * sent confreq or received confack:
973 * calculate the crc of the data from the ID field on.
976 for (i = 1; i < dlen; ++i)
977 fcs = PPP_FCS(fcs, data[i]);
980 /* outbound confreq - remember the crc for later */
985 /* received confack, check the crc */
991 return; /* not interested in received confreq */
993 /* process the options in the confack */
996 /* data[0] is code, data[1] is length */
997 while (dlen >= 2 && dlen >= data[1] && data[1] >= 2) {
1000 val = (data[2] << 8) + data[3];
1007 val = (data[2] << 24) + (data[3] << 16)
1008 + (data[4] << 8) + data[5];
1020 static void __exit ppp_async_cleanup(void)
1022 if (tty_unregister_ldisc(N_PPP) != 0)
1023 printk(KERN_ERR "failed to unregister PPP line discipline\n");
1026 module_init(ppp_async_init);
1027 module_exit(ppp_async_cleanup);