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737 lines
16 KiB
737 lines
16 KiB
// SPDX-License-Identifier: GPL-2.0-or-later |
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/* |
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* PPP synchronous tty channel driver for Linux. |
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* |
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* This is a ppp channel driver that can be used with tty device drivers |
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* that are frame oriented, such as synchronous HDLC devices. |
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* |
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* Complete PPP frames without encoding/decoding are exchanged between |
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* the channel driver and the device driver. |
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* |
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* The async map IOCTL codes are implemented to keep the user mode |
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* applications happy if they call them. Synchronous PPP does not use |
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* the async maps. |
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* |
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* Copyright 1999 Paul Mackerras. |
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* |
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* Also touched by the grubby hands of Paul Fulghum [email protected] |
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* |
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* This driver provides the encapsulation and framing for sending |
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* and receiving PPP frames over sync serial lines. It relies on |
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* the generic PPP layer to give it frames to send and to process |
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* received frames. It implements the PPP line discipline. |
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* |
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* Part of the code in this driver was inspired by the old async-only |
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* PPP driver, written by Michael Callahan and Al Longyear, and |
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* subsequently hacked by Paul Mackerras. |
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* |
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* ==FILEVERSION 20040616== |
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*/ |
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|
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#include <linux/module.h> |
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#include <linux/kernel.h> |
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#include <linux/skbuff.h> |
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#include <linux/tty.h> |
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#include <linux/netdevice.h> |
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#include <linux/poll.h> |
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#include <linux/ppp_defs.h> |
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#include <linux/ppp-ioctl.h> |
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#include <linux/ppp_channel.h> |
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#include <linux/spinlock.h> |
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#include <linux/completion.h> |
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#include <linux/init.h> |
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#include <linux/interrupt.h> |
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#include <linux/slab.h> |
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#include <linux/refcount.h> |
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#include <asm/unaligned.h> |
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#include <linux/uaccess.h> |
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|
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#define PPP_VERSION "2.4.2" |
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|
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/* Structure for storing local state. */ |
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struct syncppp { |
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struct tty_struct *tty; |
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unsigned int flags; |
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unsigned int rbits; |
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int mru; |
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spinlock_t xmit_lock; |
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spinlock_t recv_lock; |
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unsigned long xmit_flags; |
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u32 xaccm[8]; |
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u32 raccm; |
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unsigned int bytes_sent; |
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unsigned int bytes_rcvd; |
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struct sk_buff *tpkt; |
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unsigned long last_xmit; |
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struct sk_buff_head rqueue; |
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|
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struct tasklet_struct tsk; |
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|
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refcount_t refcnt; |
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struct completion dead_cmp; |
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struct ppp_channel chan; /* interface to generic ppp layer */ |
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}; |
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|
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/* Bit numbers in xmit_flags */ |
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#define XMIT_WAKEUP 0 |
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#define XMIT_FULL 1 |
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|
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/* Bits in rbits */ |
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#define SC_RCV_BITS (SC_RCV_B7_1|SC_RCV_B7_0|SC_RCV_ODDP|SC_RCV_EVNP) |
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|
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#define PPPSYNC_MAX_RQLEN 32 /* arbitrary */ |
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|
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/* |
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* Prototypes. |
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*/ |
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static struct sk_buff* ppp_sync_txmunge(struct syncppp *ap, struct sk_buff *); |
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static int ppp_sync_send(struct ppp_channel *chan, struct sk_buff *skb); |
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static int ppp_sync_ioctl(struct ppp_channel *chan, unsigned int cmd, |
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unsigned long arg); |
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static void ppp_sync_process(struct tasklet_struct *t); |
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static int ppp_sync_push(struct syncppp *ap); |
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static void ppp_sync_flush_output(struct syncppp *ap); |
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static void ppp_sync_input(struct syncppp *ap, const unsigned char *buf, |
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char *flags, int count); |
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static const struct ppp_channel_ops sync_ops = { |
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.start_xmit = ppp_sync_send, |
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.ioctl = ppp_sync_ioctl, |
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}; |
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|
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/* |
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* Utility procedure to print a buffer in hex/ascii |
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*/ |
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static void |
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ppp_print_buffer (const char *name, const __u8 *buf, int count) |
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{ |
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if (name != NULL) |
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printk(KERN_DEBUG "ppp_synctty: %s, count = %d\n", name, count); |
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print_hex_dump_bytes("", DUMP_PREFIX_NONE, buf, count); |
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} |
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/* |
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* Routines implementing the synchronous PPP line discipline. |
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*/ |
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/* |
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* We have a potential race on dereferencing tty->disc_data, |
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* because the tty layer provides no locking at all - thus one |
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* cpu could be running ppp_synctty_receive while another |
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* calls ppp_synctty_close, which zeroes tty->disc_data and |
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* frees the memory that ppp_synctty_receive is using. The best |
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* way to fix this is to use a rwlock in the tty struct, but for now |
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* we use a single global rwlock for all ttys in ppp line discipline. |
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* |
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* FIXME: Fixed in tty_io nowadays. |
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*/ |
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static DEFINE_RWLOCK(disc_data_lock); |
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static struct syncppp *sp_get(struct tty_struct *tty) |
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{ |
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struct syncppp *ap; |
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read_lock(&disc_data_lock); |
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ap = tty->disc_data; |
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if (ap != NULL) |
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refcount_inc(&ap->refcnt); |
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read_unlock(&disc_data_lock); |
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return ap; |
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} |
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static void sp_put(struct syncppp *ap) |
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{ |
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if (refcount_dec_and_test(&ap->refcnt)) |
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complete(&ap->dead_cmp); |
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} |
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/* |
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* Called when a tty is put into sync-PPP line discipline. |
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*/ |
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static int |
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ppp_sync_open(struct tty_struct *tty) |
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{ |
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struct syncppp *ap; |
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int err; |
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int speed; |
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if (tty->ops->write == NULL) |
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return -EOPNOTSUPP; |
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ap = kzalloc(sizeof(*ap), GFP_KERNEL); |
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err = -ENOMEM; |
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if (!ap) |
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goto out; |
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/* initialize the syncppp structure */ |
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ap->tty = tty; |
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ap->mru = PPP_MRU; |
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spin_lock_init(&ap->xmit_lock); |
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spin_lock_init(&ap->recv_lock); |
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ap->xaccm[0] = ~0U; |
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ap->xaccm[3] = 0x60000000U; |
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ap->raccm = ~0U; |
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skb_queue_head_init(&ap->rqueue); |
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tasklet_setup(&ap->tsk, ppp_sync_process); |
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refcount_set(&ap->refcnt, 1); |
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init_completion(&ap->dead_cmp); |
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ap->chan.private = ap; |
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ap->chan.ops = &sync_ops; |
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ap->chan.mtu = PPP_MRU; |
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ap->chan.hdrlen = 2; /* for A/C bytes */ |
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speed = tty_get_baud_rate(tty); |
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ap->chan.speed = speed; |
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err = ppp_register_channel(&ap->chan); |
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if (err) |
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goto out_free; |
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tty->disc_data = ap; |
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tty->receive_room = 65536; |
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return 0; |
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out_free: |
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kfree(ap); |
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out: |
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return err; |
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} |
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/* |
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* Called when the tty is put into another line discipline |
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* or it hangs up. We have to wait for any cpu currently |
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* executing in any of the other ppp_synctty_* routines to |
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* finish before we can call ppp_unregister_channel and free |
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* the syncppp struct. This routine must be called from |
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* process context, not interrupt or softirq context. |
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*/ |
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static void |
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ppp_sync_close(struct tty_struct *tty) |
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{ |
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struct syncppp *ap; |
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write_lock_irq(&disc_data_lock); |
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ap = tty->disc_data; |
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tty->disc_data = NULL; |
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write_unlock_irq(&disc_data_lock); |
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if (!ap) |
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return; |
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/* |
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* We have now ensured that nobody can start using ap from now |
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* on, but we have to wait for all existing users to finish. |
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* Note that ppp_unregister_channel ensures that no calls to |
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* our channel ops (i.e. ppp_sync_send/ioctl) are in progress |
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* by the time it returns. |
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*/ |
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if (!refcount_dec_and_test(&ap->refcnt)) |
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wait_for_completion(&ap->dead_cmp); |
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tasklet_kill(&ap->tsk); |
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ppp_unregister_channel(&ap->chan); |
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skb_queue_purge(&ap->rqueue); |
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kfree_skb(ap->tpkt); |
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kfree(ap); |
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} |
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/* |
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* Called on tty hangup in process context. |
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* |
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* Wait for I/O to driver to complete and unregister PPP channel. |
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* This is already done by the close routine, so just call that. |
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*/ |
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static int ppp_sync_hangup(struct tty_struct *tty) |
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{ |
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ppp_sync_close(tty); |
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return 0; |
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} |
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/* |
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* Read does nothing - no data is ever available this way. |
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* Pppd reads and writes packets via /dev/ppp instead. |
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*/ |
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static ssize_t |
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ppp_sync_read(struct tty_struct *tty, struct file *file, |
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unsigned char *buf, size_t count, |
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void **cookie, unsigned long offset) |
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{ |
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return -EAGAIN; |
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} |
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/* |
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* Write on the tty does nothing, the packets all come in |
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* from the ppp generic stuff. |
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*/ |
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static ssize_t |
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ppp_sync_write(struct tty_struct *tty, struct file *file, |
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const unsigned char *buf, size_t count) |
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{ |
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return -EAGAIN; |
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} |
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static int |
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ppp_synctty_ioctl(struct tty_struct *tty, struct file *file, |
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unsigned int cmd, unsigned long arg) |
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{ |
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struct syncppp *ap = sp_get(tty); |
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int __user *p = (int __user *)arg; |
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int err, val; |
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if (!ap) |
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return -ENXIO; |
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err = -EFAULT; |
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switch (cmd) { |
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case PPPIOCGCHAN: |
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err = -EFAULT; |
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if (put_user(ppp_channel_index(&ap->chan), p)) |
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break; |
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err = 0; |
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break; |
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case PPPIOCGUNIT: |
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err = -EFAULT; |
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if (put_user(ppp_unit_number(&ap->chan), p)) |
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break; |
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err = 0; |
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break; |
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case TCFLSH: |
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/* flush our buffers and the serial port's buffer */ |
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if (arg == TCIOFLUSH || arg == TCOFLUSH) |
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ppp_sync_flush_output(ap); |
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err = n_tty_ioctl_helper(tty, file, cmd, arg); |
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break; |
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case FIONREAD: |
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val = 0; |
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if (put_user(val, p)) |
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break; |
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err = 0; |
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break; |
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default: |
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err = tty_mode_ioctl(tty, file, cmd, arg); |
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break; |
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} |
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sp_put(ap); |
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return err; |
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} |
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/* No kernel lock - fine */ |
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static __poll_t |
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ppp_sync_poll(struct tty_struct *tty, struct file *file, poll_table *wait) |
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{ |
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return 0; |
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} |
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/* May sleep, don't call from interrupt level or with interrupts disabled */ |
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static void |
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ppp_sync_receive(struct tty_struct *tty, const unsigned char *buf, |
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char *cflags, int count) |
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{ |
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struct syncppp *ap = sp_get(tty); |
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unsigned long flags; |
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if (!ap) |
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return; |
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spin_lock_irqsave(&ap->recv_lock, flags); |
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ppp_sync_input(ap, buf, cflags, count); |
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spin_unlock_irqrestore(&ap->recv_lock, flags); |
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if (!skb_queue_empty(&ap->rqueue)) |
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tasklet_schedule(&ap->tsk); |
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sp_put(ap); |
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tty_unthrottle(tty); |
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} |
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static void |
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ppp_sync_wakeup(struct tty_struct *tty) |
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{ |
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struct syncppp *ap = sp_get(tty); |
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clear_bit(TTY_DO_WRITE_WAKEUP, &tty->flags); |
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if (!ap) |
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return; |
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set_bit(XMIT_WAKEUP, &ap->xmit_flags); |
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tasklet_schedule(&ap->tsk); |
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sp_put(ap); |
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} |
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static struct tty_ldisc_ops ppp_sync_ldisc = { |
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.owner = THIS_MODULE, |
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.magic = TTY_LDISC_MAGIC, |
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.name = "pppsync", |
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.open = ppp_sync_open, |
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.close = ppp_sync_close, |
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.hangup = ppp_sync_hangup, |
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.read = ppp_sync_read, |
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.write = ppp_sync_write, |
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.ioctl = ppp_synctty_ioctl, |
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.poll = ppp_sync_poll, |
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.receive_buf = ppp_sync_receive, |
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.write_wakeup = ppp_sync_wakeup, |
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}; |
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static int __init |
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ppp_sync_init(void) |
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{ |
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int err; |
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err = tty_register_ldisc(N_SYNC_PPP, &ppp_sync_ldisc); |
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if (err != 0) |
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printk(KERN_ERR "PPP_sync: error %d registering line disc.\n", |
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err); |
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return err; |
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} |
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/* |
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* The following routines provide the PPP channel interface. |
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*/ |
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static int |
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ppp_sync_ioctl(struct ppp_channel *chan, unsigned int cmd, unsigned long arg) |
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{ |
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struct syncppp *ap = chan->private; |
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int err, val; |
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u32 accm[8]; |
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void __user *argp = (void __user *)arg; |
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u32 __user *p = argp; |
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err = -EFAULT; |
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switch (cmd) { |
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case PPPIOCGFLAGS: |
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val = ap->flags | ap->rbits; |
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if (put_user(val, (int __user *) argp)) |
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break; |
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err = 0; |
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break; |
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case PPPIOCSFLAGS: |
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if (get_user(val, (int __user *) argp)) |
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break; |
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ap->flags = val & ~SC_RCV_BITS; |
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spin_lock_irq(&ap->recv_lock); |
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ap->rbits = val & SC_RCV_BITS; |
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spin_unlock_irq(&ap->recv_lock); |
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err = 0; |
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break; |
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case PPPIOCGASYNCMAP: |
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if (put_user(ap->xaccm[0], p)) |
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break; |
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err = 0; |
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break; |
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case PPPIOCSASYNCMAP: |
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if (get_user(ap->xaccm[0], p)) |
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break; |
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err = 0; |
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break; |
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case PPPIOCGRASYNCMAP: |
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if (put_user(ap->raccm, p)) |
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break; |
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err = 0; |
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break; |
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case PPPIOCSRASYNCMAP: |
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if (get_user(ap->raccm, p)) |
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break; |
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err = 0; |
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break; |
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case PPPIOCGXASYNCMAP: |
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if (copy_to_user(argp, ap->xaccm, sizeof(ap->xaccm))) |
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break; |
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err = 0; |
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break; |
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case PPPIOCSXASYNCMAP: |
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if (copy_from_user(accm, argp, sizeof(accm))) |
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break; |
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accm[2] &= ~0x40000000U; /* can't escape 0x5e */ |
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accm[3] |= 0x60000000U; /* must escape 0x7d, 0x7e */ |
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memcpy(ap->xaccm, accm, sizeof(ap->xaccm)); |
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err = 0; |
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break; |
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case PPPIOCGMRU: |
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if (put_user(ap->mru, (int __user *) argp)) |
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break; |
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err = 0; |
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break; |
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case PPPIOCSMRU: |
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if (get_user(val, (int __user *) argp)) |
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break; |
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if (val < PPP_MRU) |
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val = PPP_MRU; |
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ap->mru = val; |
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err = 0; |
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break; |
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default: |
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err = -ENOTTY; |
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} |
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return err; |
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} |
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|
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/* |
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* This is called at softirq level to deliver received packets |
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* to the ppp_generic code, and to tell the ppp_generic code |
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* if we can accept more output now. |
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*/ |
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static void ppp_sync_process(struct tasklet_struct *t) |
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{ |
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struct syncppp *ap = from_tasklet(ap, t, tsk); |
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struct sk_buff *skb; |
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|
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/* process received packets */ |
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while ((skb = skb_dequeue(&ap->rqueue)) != NULL) { |
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if (skb->len == 0) { |
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/* zero length buffers indicate error */ |
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ppp_input_error(&ap->chan, 0); |
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kfree_skb(skb); |
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} |
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else |
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ppp_input(&ap->chan, skb); |
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} |
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|
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/* try to push more stuff out */ |
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if (test_bit(XMIT_WAKEUP, &ap->xmit_flags) && ppp_sync_push(ap)) |
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ppp_output_wakeup(&ap->chan); |
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} |
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|
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/* |
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* Procedures for encapsulation and framing. |
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*/ |
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|
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static struct sk_buff* |
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ppp_sync_txmunge(struct syncppp *ap, struct sk_buff *skb) |
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{ |
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int proto; |
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unsigned char *data; |
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int islcp; |
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|
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data = skb->data; |
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proto = get_unaligned_be16(data); |
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|
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/* LCP packets with codes between 1 (configure-request) |
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* and 7 (code-reject) must be sent as though no options |
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* have been negotiated. |
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*/ |
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islcp = proto == PPP_LCP && 1 <= data[2] && data[2] <= 7; |
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|
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/* compress protocol field if option enabled */ |
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if (data[0] == 0 && (ap->flags & SC_COMP_PROT) && !islcp) |
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skb_pull(skb,1); |
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|
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/* prepend address/control fields if necessary */ |
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if ((ap->flags & SC_COMP_AC) == 0 || islcp) { |
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if (skb_headroom(skb) < 2) { |
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struct sk_buff *npkt = dev_alloc_skb(skb->len + 2); |
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if (npkt == NULL) { |
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kfree_skb(skb); |
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return NULL; |
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} |
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skb_reserve(npkt,2); |
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skb_copy_from_linear_data(skb, |
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skb_put(npkt, skb->len), skb->len); |
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consume_skb(skb); |
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skb = npkt; |
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} |
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skb_push(skb,2); |
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skb->data[0] = PPP_ALLSTATIONS; |
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skb->data[1] = PPP_UI; |
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} |
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|
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ap->last_xmit = jiffies; |
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|
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if (skb && ap->flags & SC_LOG_OUTPKT) |
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ppp_print_buffer ("send buffer", skb->data, skb->len); |
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|
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return skb; |
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} |
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|
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/* |
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* Transmit-side routines. |
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*/ |
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|
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/* |
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* Send a packet to the peer over an sync tty line. |
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* Returns 1 iff the packet was accepted. |
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* If the packet was not accepted, we will call ppp_output_wakeup |
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* at some later time. |
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*/ |
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static int |
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ppp_sync_send(struct ppp_channel *chan, struct sk_buff *skb) |
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{ |
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struct syncppp *ap = chan->private; |
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|
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ppp_sync_push(ap); |
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|
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if (test_and_set_bit(XMIT_FULL, &ap->xmit_flags)) |
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return 0; /* already full */ |
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skb = ppp_sync_txmunge(ap, skb); |
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if (skb != NULL) |
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ap->tpkt = skb; |
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else |
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clear_bit(XMIT_FULL, &ap->xmit_flags); |
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|
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ppp_sync_push(ap); |
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return 1; |
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} |
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|
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/* |
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* Push as much data as possible out to the tty. |
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*/ |
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static int |
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ppp_sync_push(struct syncppp *ap) |
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{ |
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int sent, done = 0; |
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struct tty_struct *tty = ap->tty; |
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int tty_stuffed = 0; |
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|
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if (!spin_trylock_bh(&ap->xmit_lock)) |
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return 0; |
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for (;;) { |
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if (test_and_clear_bit(XMIT_WAKEUP, &ap->xmit_flags)) |
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tty_stuffed = 0; |
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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);
|
|
|