/* * 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 program is free software; you can redistribute it and/or * modify it under the terms of the GNU General Public License * as published by the Free Software Foundation; either version * 2 of the License, or (at your option) any later version. * * 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 #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #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; atomic_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(unsigned long arg); 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, 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) atomic_inc(&ap->refcnt); read_unlock(&disc_data_lock); return ap; } static void sp_put(struct syncppp *ap) { if (atomic_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_init(&ap->tsk, ppp_sync_process, (unsigned long) ap); atomic_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 (!atomic_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 __user *buf, size_t count) { 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 unsigned int 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, 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, .magic = TTY_LDISC_MAGIC, .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(unsigned long arg) { struct syncppp *ap = (struct syncppp *) arg; 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, 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);