OSCL-LXR linux-6.0.1/​drivers/​net/​ppp/​ppp_synctty.c	Source navigation Diff markup Identifier search General search
	Version: linux-6.0.1 spark-3.0.0 hadoop-3.2.0-src hadoop-3.3.0-src spark-2.4.7 linux-4.15.13 hadoop-2.7.4-src Revert   Change

 // 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(struct tasklet_struct *t);
 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,
                const 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_setup(&ap->tsk, ppp_sync_process);
 
     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 void ppp_sync_hangup(struct tty_struct *tty)
 {
     ppp_sync_close(tty);
 }
 
 /*
  * 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 *buf, size_t count,
           void **cookie, unsigned long offset)
 {
     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, 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, cmd, arg);
         break;
 
     case FIONREAD:
         val = 0;
         if (put_user(val, p))
             break;
         err = 0;
         break;
 
     default:
         err = tty_mode_ioctl(tty, 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,
           const 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,
     .num    = N_SYNC_PPP,
     .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(&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(struct tasklet_struct *t)
 {
     struct syncppp *ap = from_tasklet(ap, t, tsk);
     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,
         const 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)
 {
     tty_unregister_ldisc(&ppp_sync_ldisc);
 }
 
 module_init(ppp_sync_init);
 module_exit(ppp_sync_cleanup);
 MODULE_LICENSE("GPL");
 MODULE_ALIAS_LDISC(N_SYNC_PPP);

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