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linux/net/lapb/lapb_iface.c
Xie He 65d2dbb300 net: lapb: Make "lapb_t1timer_running" able to detect an already running timer 
Problem:

The "lapb_t1timer_running" function in "lapb_timer.c" is used in only
one place: in the "lapb_kick" function in "lapb_out.c". "lapb_kick" calls
"lapb_t1timer_running" to check if the timer is already pending, and if
it is not, schedule it to run.

However, if the timer has already fired and is running, and is waiting to
get the "lapb->lock" lock, "lapb_t1timer_running" will not detect this,
and "lapb_kick" will then schedule a new timer. The old timer will then
abort when it sees a new timer pending.

I think this is not right. The purpose of "lapb_kick" should be ensuring
that the actual work of the timer function is scheduled to be done.
If the timer function is already running but waiting for the lock,
"lapb_kick" should not abort and reschedule it.

Changes made:

I added a new field "t1timer_running" in "struct lapb_cb" for
"lapb_t1timer_running" to use. "t1timer_running" will accurately reflect
whether the actual work of the timer is pending. If the timer has fired
but is still waiting for the lock, "t1timer_running" will still correctly
reflect whether the actual work is waiting to be done.

The old "t1timer_stop" field, whose only responsibility is to ask a timer
(that is already running but waiting for the lock) to abort, is no longer
needed, because the new "t1timer_running" field can fully take over its
responsibility. Therefore "t1timer_stop" is deleted.

"t1timer_running" is not simply a negation of the old "t1timer_stop".
At the end of the timer function, if it does not reschedule itself,
"t1timer_running" is set to false to indicate that the timer is stopped.

For consistency of the code, I also added "t2timer_running" and deleted
"t2timer_stop".

Signed-off-by: Xie He <xie.he.0141@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
2021-03-23 14:14:50 -07:00

556 lines
12 KiB
C
Raw Blame History

// SPDX-License-Identifier: GPL-2.0-or-later
/*
* LAPB release 002
*
* This code REQUIRES 2.1.15 or higher/ NET3.038
*
* History
* LAPB 001 Jonathan Naylor Started Coding
* LAPB 002 Jonathan Naylor New timer architecture.
* 2000-10-29 Henner Eisen lapb_data_indication() return status.
*/
#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
#include <linux/module.h>
#include <linux/errno.h>
#include <linux/types.h>
#include <linux/socket.h>
#include <linux/in.h>
#include <linux/kernel.h>
#include <linux/jiffies.h>
#include <linux/timer.h>
#include <linux/string.h>
#include <linux/sockios.h>
#include <linux/net.h>
#include <linux/inet.h>
#include <linux/if_arp.h>
#include <linux/skbuff.h>
#include <linux/slab.h>
#include <net/sock.h>
#include <linux/uaccess.h>
#include <linux/fcntl.h>
#include <linux/mm.h>
#include <linux/interrupt.h>
#include <linux/stat.h>
#include <linux/init.h>
#include <net/lapb.h>
static LIST_HEAD(lapb_list);
static DEFINE_RWLOCK(lapb_list_lock);
/*
* Free an allocated lapb control block.
*/
static void lapb_free_cb(struct lapb_cb *lapb)
{
kfree(lapb);
}
static __inline__ void lapb_hold(struct lapb_cb *lapb)
{
refcount_inc(&lapb->refcnt);
}
static __inline__ void lapb_put(struct lapb_cb *lapb)
{
if (refcount_dec_and_test(&lapb->refcnt))
lapb_free_cb(lapb);
}
/*
* Socket removal during an interrupt is now safe.
*/
static void __lapb_remove_cb(struct lapb_cb *lapb)
{
if (lapb->node.next) {
list_del(&lapb->node);
lapb_put(lapb);
}
}
/*
* Add a socket to the bound sockets list.
*/
static void __lapb_insert_cb(struct lapb_cb *lapb)
{
list_add(&lapb->node, &lapb_list);
lapb_hold(lapb);
}
static struct lapb_cb *__lapb_devtostruct(struct net_device *dev)
{
struct list_head *entry;
struct lapb_cb *lapb, *use = NULL;
list_for_each(entry, &lapb_list) {
lapb = list_entry(entry, struct lapb_cb, node);
if (lapb->dev == dev) {
use = lapb;
break;
}
}
if (use)
lapb_hold(use);
return use;
}
static struct lapb_cb *lapb_devtostruct(struct net_device *dev)
{
struct lapb_cb *rc;
read_lock_bh(&lapb_list_lock);
rc = __lapb_devtostruct(dev);
read_unlock_bh(&lapb_list_lock);
return rc;
}
/*
* Create an empty LAPB control block.
*/
static struct lapb_cb *lapb_create_cb(void)
{
struct lapb_cb *lapb = kzalloc(sizeof(*lapb), GFP_ATOMIC);
if (!lapb)
goto out;
skb_queue_head_init(&lapb->write_queue);
skb_queue_head_init(&lapb->ack_queue);
timer_setup(&lapb->t1timer, NULL, 0);
timer_setup(&lapb->t2timer, NULL, 0);
lapb->t1timer_running = false;
lapb->t2timer_running = false;
lapb->t1 = LAPB_DEFAULT_T1;
lapb->t2 = LAPB_DEFAULT_T2;
lapb->n2 = LAPB_DEFAULT_N2;
lapb->mode = LAPB_DEFAULT_MODE;
lapb->window = LAPB_DEFAULT_WINDOW;
lapb->state = LAPB_STATE_0;
spin_lock_init(&lapb->lock);
refcount_set(&lapb->refcnt, 1);
out:
return lapb;
}
int lapb_register(struct net_device *dev,
const struct lapb_register_struct *callbacks)
{
struct lapb_cb *lapb;
int rc = LAPB_BADTOKEN;
write_lock_bh(&lapb_list_lock);
lapb = __lapb_devtostruct(dev);
if (lapb) {
lapb_put(lapb);
goto out;
}
lapb = lapb_create_cb();
rc = LAPB_NOMEM;
if (!lapb)
goto out;
lapb->dev = dev;
lapb->callbacks = callbacks;
__lapb_insert_cb(lapb);
lapb_start_t1timer(lapb);
rc = LAPB_OK;
out:
write_unlock_bh(&lapb_list_lock);
return rc;
}
EXPORT_SYMBOL(lapb_register);
int lapb_unregister(struct net_device *dev)
{
struct lapb_cb *lapb;
int rc = LAPB_BADTOKEN;
write_lock_bh(&lapb_list_lock);
lapb = __lapb_devtostruct(dev);
if (!lapb)
goto out;
lapb_put(lapb);
/* Wait for other refs to "lapb" to drop */
while (refcount_read(&lapb->refcnt) > 2)
usleep_range(1, 10);
spin_lock_bh(&lapb->lock);
lapb_stop_t1timer(lapb);
lapb_stop_t2timer(lapb);
lapb_clear_queues(lapb);
spin_unlock_bh(&lapb->lock);
/* Wait for running timers to stop */
del_timer_sync(&lapb->t1timer);
del_timer_sync(&lapb->t2timer);
__lapb_remove_cb(lapb);
lapb_put(lapb);
rc = LAPB_OK;
out:
write_unlock_bh(&lapb_list_lock);
return rc;
}
EXPORT_SYMBOL(lapb_unregister);
int lapb_getparms(struct net_device *dev, struct lapb_parms_struct *parms)
{
int rc = LAPB_BADTOKEN;
struct lapb_cb *lapb = lapb_devtostruct(dev);
if (!lapb)
goto out;
spin_lock_bh(&lapb->lock);
parms->t1 = lapb->t1 / HZ;
parms->t2 = lapb->t2 / HZ;
parms->n2 = lapb->n2;
parms->n2count = lapb->n2count;
parms->state = lapb->state;
parms->window = lapb->window;
parms->mode = lapb->mode;
if (!timer_pending(&lapb->t1timer))
parms->t1timer = 0;
else
parms->t1timer = (lapb->t1timer.expires - jiffies) / HZ;
if (!timer_pending(&lapb->t2timer))
parms->t2timer = 0;
else
parms->t2timer = (lapb->t2timer.expires - jiffies) / HZ;
spin_unlock_bh(&lapb->lock);
lapb_put(lapb);
rc = LAPB_OK;
out:
return rc;
}
EXPORT_SYMBOL(lapb_getparms);
int lapb_setparms(struct net_device *dev, struct lapb_parms_struct *parms)
{
int rc = LAPB_BADTOKEN;
struct lapb_cb *lapb = lapb_devtostruct(dev);
if (!lapb)
goto out;
spin_lock_bh(&lapb->lock);
rc = LAPB_INVALUE;
if (parms->t1 < 1 || parms->t2 < 1 || parms->n2 < 1)
goto out_put;
if (lapb->state == LAPB_STATE_0) {
if (parms->mode & LAPB_EXTENDED) {
if (parms->window < 1 || parms->window > 127)
goto out_put;
} else {
if (parms->window < 1 || parms->window > 7)
goto out_put;
}
lapb->mode = parms->mode;
lapb->window = parms->window;
}
lapb->t1 = parms->t1 * HZ;
lapb->t2 = parms->t2 * HZ;
lapb->n2 = parms->n2;
rc = LAPB_OK;
out_put:
spin_unlock_bh(&lapb->lock);
lapb_put(lapb);
out:
return rc;
}
EXPORT_SYMBOL(lapb_setparms);
int lapb_connect_request(struct net_device *dev)
{
struct lapb_cb *lapb = lapb_devtostruct(dev);
int rc = LAPB_BADTOKEN;
if (!lapb)
goto out;
spin_lock_bh(&lapb->lock);
rc = LAPB_OK;
if (lapb->state == LAPB_STATE_1)
goto out_put;
rc = LAPB_CONNECTED;
if (lapb->state == LAPB_STATE_3 || lapb->state == LAPB_STATE_4)
goto out_put;
lapb_establish_data_link(lapb);
lapb_dbg(0, "(%p) S0 -> S1\n", lapb->dev);
lapb->state = LAPB_STATE_1;
rc = LAPB_OK;
out_put:
spin_unlock_bh(&lapb->lock);
lapb_put(lapb);
out:
return rc;
}
EXPORT_SYMBOL(lapb_connect_request);
static int __lapb_disconnect_request(struct lapb_cb *lapb)
{
switch (lapb->state) {
case LAPB_STATE_0:
return LAPB_NOTCONNECTED;
case LAPB_STATE_1:
lapb_dbg(1, "(%p) S1 TX DISC(1)\n", lapb->dev);
lapb_dbg(0, "(%p) S1 -> S0\n", lapb->dev);
lapb_send_control(lapb, LAPB_DISC, LAPB_POLLON, LAPB_COMMAND);
lapb->state = LAPB_STATE_0;
lapb_start_t1timer(lapb);
return LAPB_NOTCONNECTED;
case LAPB_STATE_2:
return LAPB_OK;
}
lapb_clear_queues(lapb);
lapb->n2count = 0;
lapb_send_control(lapb, LAPB_DISC, LAPB_POLLON, LAPB_COMMAND);
lapb_start_t1timer(lapb);
lapb_stop_t2timer(lapb);
lapb->state = LAPB_STATE_2;
lapb_dbg(1, "(%p) S3 DISC(1)\n", lapb->dev);
lapb_dbg(0, "(%p) S3 -> S2\n", lapb->dev);
return LAPB_OK;
}
int lapb_disconnect_request(struct net_device *dev)
{
struct lapb_cb *lapb = lapb_devtostruct(dev);
int rc = LAPB_BADTOKEN;
if (!lapb)
goto out;
spin_lock_bh(&lapb->lock);
rc = __lapb_disconnect_request(lapb);
spin_unlock_bh(&lapb->lock);
lapb_put(lapb);
out:
return rc;
}
EXPORT_SYMBOL(lapb_disconnect_request);
int lapb_data_request(struct net_device *dev, struct sk_buff *skb)
{
struct lapb_cb *lapb = lapb_devtostruct(dev);
int rc = LAPB_BADTOKEN;
if (!lapb)
goto out;
spin_lock_bh(&lapb->lock);
rc = LAPB_NOTCONNECTED;
if (lapb->state != LAPB_STATE_3 && lapb->state != LAPB_STATE_4)
goto out_put;
skb_queue_tail(&lapb->write_queue, skb);
lapb_kick(lapb);
rc = LAPB_OK;
out_put:
spin_unlock_bh(&lapb->lock);
lapb_put(lapb);
out:
return rc;
}
EXPORT_SYMBOL(lapb_data_request);
int lapb_data_received(struct net_device *dev, struct sk_buff *skb)
{
struct lapb_cb *lapb = lapb_devtostruct(dev);
int rc = LAPB_BADTOKEN;
if (lapb) {
spin_lock_bh(&lapb->lock);
lapb_data_input(lapb, skb);
spin_unlock_bh(&lapb->lock);
lapb_put(lapb);
rc = LAPB_OK;
}
return rc;
}
EXPORT_SYMBOL(lapb_data_received);
void lapb_connect_confirmation(struct lapb_cb *lapb, int reason)
{
if (lapb->callbacks->connect_confirmation)
lapb->callbacks->connect_confirmation(lapb->dev, reason);
}
void lapb_connect_indication(struct lapb_cb *lapb, int reason)
{
if (lapb->callbacks->connect_indication)
lapb->callbacks->connect_indication(lapb->dev, reason);
}
void lapb_disconnect_confirmation(struct lapb_cb *lapb, int reason)
{
if (lapb->callbacks->disconnect_confirmation)
lapb->callbacks->disconnect_confirmation(lapb->dev, reason);
}
void lapb_disconnect_indication(struct lapb_cb *lapb, int reason)
{
if (lapb->callbacks->disconnect_indication)
lapb->callbacks->disconnect_indication(lapb->dev, reason);
}
int lapb_data_indication(struct lapb_cb *lapb, struct sk_buff *skb)
{
if (lapb->callbacks->data_indication)
return lapb->callbacks->data_indication(lapb->dev, skb);
kfree_skb(skb);
return NET_RX_SUCCESS; /* For now; must be != NET_RX_DROP */
}
int lapb_data_transmit(struct lapb_cb *lapb, struct sk_buff *skb)
{
int used = 0;
if (lapb->callbacks->data_transmit) {
lapb->callbacks->data_transmit(lapb->dev, skb);
used = 1;
}
return used;
}
/* Handle device status changes. */
static int lapb_device_event(struct notifier_block *this, unsigned long event,
void *ptr)
{
struct net_device *dev = netdev_notifier_info_to_dev(ptr);
struct lapb_cb *lapb;
if (!net_eq(dev_net(dev), &init_net))
return NOTIFY_DONE;
if (dev->type != ARPHRD_X25)
return NOTIFY_DONE;
lapb = lapb_devtostruct(dev);
if (!lapb)
return NOTIFY_DONE;
spin_lock_bh(&lapb->lock);
switch (event) {
case NETDEV_UP:
lapb_dbg(0, "(%p) Interface up: %s\n", dev, dev->name);
if (netif_carrier_ok(dev)) {
lapb_dbg(0, "(%p): Carrier is already up: %s\n", dev,
dev->name);
if (lapb->mode & LAPB_DCE) {
lapb_start_t1timer(lapb);
} else {
if (lapb->state == LAPB_STATE_0) {
lapb->state = LAPB_STATE_1;
lapb_establish_data_link(lapb);
}
}
}
break;
case NETDEV_GOING_DOWN:
if (netif_carrier_ok(dev))
__lapb_disconnect_request(lapb);
break;
case NETDEV_DOWN:
lapb_dbg(0, "(%p) Interface down: %s\n", dev, dev->name);
lapb_dbg(0, "(%p) S%d -> S0\n", dev, lapb->state);
lapb_clear_queues(lapb);
lapb->state = LAPB_STATE_0;
lapb->n2count = 0;
lapb_stop_t1timer(lapb);
lapb_stop_t2timer(lapb);
break;
case NETDEV_CHANGE:
if (netif_carrier_ok(dev)) {
lapb_dbg(0, "(%p): Carrier detected: %s\n", dev,
dev->name);
if (lapb->mode & LAPB_DCE) {
lapb_start_t1timer(lapb);
} else {
if (lapb->state == LAPB_STATE_0) {
lapb->state = LAPB_STATE_1;
lapb_establish_data_link(lapb);
}
}
} else {
lapb_dbg(0, "(%p) Carrier lost: %s\n", dev, dev->name);
lapb_dbg(0, "(%p) S%d -> S0\n", dev, lapb->state);
lapb_clear_queues(lapb);
lapb->state = LAPB_STATE_0;
lapb->n2count = 0;
lapb_stop_t1timer(lapb);
lapb_stop_t2timer(lapb);
}
break;
}
spin_unlock_bh(&lapb->lock);
lapb_put(lapb);
return NOTIFY_DONE;
}
static struct notifier_block lapb_dev_notifier = {
.notifier_call = lapb_device_event,
};
static int __init lapb_init(void)
{
return register_netdevice_notifier(&lapb_dev_notifier);
}
static void __exit lapb_exit(void)
{
WARN_ON(!list_empty(&lapb_list));
unregister_netdevice_notifier(&lapb_dev_notifier);
}
MODULE_AUTHOR("Jonathan Naylor <g4klx@g4klx.demon.co.uk>");
MODULE_DESCRIPTION("The X.25 Link Access Procedure B link layer protocol");
MODULE_LICENSE("GPL");
module_init(lapb_init);
module_exit(lapb_exit);
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