/*
* PPP async serial channel driver for Linux.
*
* Copyright 1999 Paul Mackerras.
*
* 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 async 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.
*/
#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/crc-ccitt.h>
#include <linux/ppp_defs.h>
#include <linux/if_ppp.h>
#include <linux/ppp_channel.h>
#include <linux/spinlock.h>
#include <linux/init.h>
#include <linux/jiffies.h>
#include <asm/uaccess.h>
#include <asm/string.h>
#define PPP_VERSION "2.4.2"
#define OBUFSIZE 256
/* Structure for storing local state. */
struct asyncppp {
struct tty_struct *tty;
unsigned int flags;
unsigned int state;
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;
int tpkt_pos;
u16 tfcs;
unsigned char *optr;
unsigned char *olim;
unsigned long last_xmit;
struct sk_buff *rpkt;
int lcp_fcs;
struct sk_buff_head rqueue;
struct tasklet_struct tsk;
atomic_t refcnt;
struct semaphore dead_sem;
struct ppp_channel chan; /* interface to generic ppp layer */
unsigned char obuf[OBUFSIZE];
};
/* Bit numbers in xmit_flags */
#define XMIT_WAKEUP 0
#define XMIT_FULL 1
#define XMIT_BUSY 2
/* State bits */
#define SC_TOSS 1
#define SC_ESCAPE 2
#define SC_PREV_ERROR 4
/* Bits in rbits */
#define SC_RCV_BITS (SC_RCV_B7_1|SC_RCV_B7_0|SC_RCV_ODDP|SC_RCV_EVNP)
static int flag_time = HZ;
module_param(flag_time, int, 0);
MODULE_PARM_DESC(flag_time, "ppp_async: interval between flagged packets (in clock ticks)");
MODULE_LICENSE("GPL");
MODULE_ALIAS_LDISC(N_PPP);
/*
* Prototypes.
*/
static int ppp_async_encode(struct asyncppp *ap);
static int ppp_async_send(struct ppp_channel *chan, struct sk_buff *skb);
static int ppp_async_push(struct asyncppp *ap);
static void ppp_async_flush_output(struct asyncppp *ap);
static void ppp_async_input(struct asyncppp *ap, const unsigned char *buf,
char *flags, int count);
static int ppp_async_ioctl(struct ppp_channel *chan, unsigned int cmd,
unsigned long arg);
static void ppp_async_process(unsigned long arg);
static void async_lcp_peek(struct asyncppp *ap, unsigned char *data,
int len, int inbound);
static struct ppp_channel_ops async_ops = {
ppp_async_send,
ppp_async_ioctl
};
/*
* Routines implementing the 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_asynctty_receive while another
* calls ppp_asynctty_close, which zeroes tty->disc_data and
* frees the memory that ppp_asynctty_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: this is no longer true. The _close path for the ldisc is
* now guaranteed to be sane.
*/
static DEFINE_RWLOCK(disc_data_lock);
static struct asyncppp *ap_get(struct tty_struct *tty)
{
struct asyncppp *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 ap_put(struct asyncppp *ap)
{
if (atomic_dec_and_test(&ap->refcnt))
up(&ap->dead_sem);
}
/*
* Called when a tty is put into PPP line discipline. Called in process
* context.
*/
static int
ppp_asynctty_open(struct tty_struct *tty)
{
struct asyncppp *ap;
int err;
if (tty->ops->write == NULL)
return -EOPNOTSUPP;
err = -ENOMEM;
ap = kzalloc(sizeof(*ap), GFP_KERNEL);
if (!ap)
goto out;
/* initialize the asyncppp structure */
ap->tty = tty;
ap->mru = PPP_MRU;
spin_lock_init(&ap->xmit_lock);
spin_lock_init(&ap->recv_lock