diff options
Diffstat (limited to 'drivers/net/ppp/ppp_synctty.c')
| -rw-r--r-- | drivers/net/ppp/ppp_synctty.c | 741 |
1 files changed, 741 insertions, 0 deletions
diff --git a/drivers/net/ppp/ppp_synctty.c b/drivers/net/ppp/ppp_synctty.c new file mode 100644 index 000000000..925d3e295 --- /dev/null +++ b/drivers/net/ppp/ppp_synctty.c @@ -0,0 +1,741 @@ +/* + * 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 <linux/module.h> +#include <linux/kernel.h> +#include <linux/skbuff.h> +#include <linux/tty.h> +#include <linux/netdevice.h> +#include <linux/poll.h> +#include <linux/ppp_defs.h> +#include <linux/ppp-ioctl.h> +#include <linux/ppp_channel.h> +#include <linux/spinlock.h> +#include <linux/completion.h> +#include <linux/init.h> +#include <linux/interrupt.h> +#include <linux/slab.h> +#include <asm/unaligned.h> +#include <asm/uaccess.h> + +#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; + } + + p = skb_put(skb, count); + memcpy(p, 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); + } + + /* decompress protocol field if compressed */ + if (p[0] & 1) { + /* protocol is compressed */ + skb_push(skb, 1)[0] = 0; + } else if (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); |