| // SPDX-License-Identifier: GPL-2.0-or-later |
| /* |
| * 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 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 <linux/refcount.h> |
| #include <asm/unaligned.h> |
| #include <linux/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; |
| |
| refcount_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) |
| refcount_inc(&ap->refcnt); |
| read_unlock(&disc_data_lock); |
| return ap; |
| } |
| |
| static void sp_put(struct syncppp *ap) |
| { |
| if (refcount_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); |
| |
| refcount_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 (!refcount_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 __poll_t |
| 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 > U16_MAX) { |
| err = -EINVAL; |
| 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 (skb->len >= 2 && 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); |