linux/drivers/net/wan/lapbether.c
David S. Miller cf124db566 net: Fix inconsistent teardown and release of private netdev state.
Network devices can allocate reasources and private memory using
netdev_ops->ndo_init().  However, the release of these resources
can occur in one of two different places.

Either netdev_ops->ndo_uninit() or netdev->destructor().

The decision of which operation frees the resources depends upon
whether it is necessary for all netdev refs to be released before it
is safe to perform the freeing.

netdev_ops->ndo_uninit() presumably can occur right after the
NETDEV_UNREGISTER notifier completes and the unicast and multicast
address lists are flushed.

netdev->destructor(), on the other hand, does not run until the
netdev references all go away.

Further complicating the situation is that netdev->destructor()
almost universally does also a free_netdev().

This creates a problem for the logic in register_netdevice().
Because all callers of register_netdevice() manage the freeing
of the netdev, and invoke free_netdev(dev) if register_netdevice()
fails.

If netdev_ops->ndo_init() succeeds, but something else fails inside
of register_netdevice(), it does call ndo_ops->ndo_uninit().  But
it is not able to invoke netdev->destructor().

This is because netdev->destructor() will do a free_netdev() and
then the caller of register_netdevice() will do the same.

However, this means that the resources that would normally be released
by netdev->destructor() will not be.

Over the years drivers have added local hacks to deal with this, by
invoking their destructor parts by hand when register_netdevice()
fails.

Many drivers do not try to deal with this, and instead we have leaks.

Let's close this hole by formalizing the distinction between what
private things need to be freed up by netdev->destructor() and whether
the driver needs unregister_netdevice() to perform the free_netdev().

netdev->priv_destructor() performs all actions to free up the private
resources that used to be freed by netdev->destructor(), except for
free_netdev().

netdev->needs_free_netdev is a boolean that indicates whether
free_netdev() should be done at the end of unregister_netdevice().

Now, register_netdevice() can sanely release all resources after
ndo_ops->ndo_init() succeeds, by invoking both ndo_ops->ndo_uninit()
and netdev->priv_destructor().

And at the end of unregister_netdevice(), we invoke
netdev->priv_destructor() and optionally call free_netdev().

Signed-off-by: David S. Miller <davem@davemloft.net>
2017-06-07 15:53:24 -04:00

451 lines
9.9 KiB
C

/*
* "LAPB via ethernet" driver release 001
*
* This code REQUIRES 2.1.15 or higher/ NET3.038
*
* This module:
* This module 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 is a "pseudo" network driver to allow LAPB over Ethernet.
*
* This driver can use any ethernet destination address, and can be
* limited to accept frames from one dedicated ethernet card only.
*
* History
* LAPBETH 001 Jonathan Naylor Cloned from bpqether.c
* 2000-10-29 Henner Eisen lapb_data_indication() return status.
* 2000-11-14 Henner Eisen dev_hold/put, NETDEV_GOING_DOWN support
*/
#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
#include <linux/errno.h>
#include <linux/types.h>
#include <linux/socket.h>
#include <linux/in.h>
#include <linux/slab.h>
#include <linux/kernel.h>
#include <linux/string.h>
#include <linux/net.h>
#include <linux/inet.h>
#include <linux/netdevice.h>
#include <linux/if_arp.h>
#include <linux/skbuff.h>
#include <net/sock.h>
#include <linux/uaccess.h>
#include <linux/mm.h>
#include <linux/interrupt.h>
#include <linux/notifier.h>
#include <linux/stat.h>
#include <linux/module.h>
#include <linux/lapb.h>
#include <linux/init.h>
#include <net/x25device.h>
static const u8 bcast_addr[6] = { 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF };
/* If this number is made larger, check that the temporary string buffer
* in lapbeth_new_device is large enough to store the probe device name.*/
#define MAXLAPBDEV 100
struct lapbethdev {
struct list_head node;
struct net_device *ethdev; /* link to ethernet device */
struct net_device *axdev; /* lapbeth device (lapb#) */
};
static LIST_HEAD(lapbeth_devices);
/* ------------------------------------------------------------------------ */
/*
* Get the LAPB device for the ethernet device
*/
static struct lapbethdev *lapbeth_get_x25_dev(struct net_device *dev)
{
struct lapbethdev *lapbeth;
list_for_each_entry_rcu(lapbeth, &lapbeth_devices, node) {
if (lapbeth->ethdev == dev)
return lapbeth;
}
return NULL;
}
static __inline__ int dev_is_ethdev(struct net_device *dev)
{
return dev->type == ARPHRD_ETHER && strncmp(dev->name, "dummy", 5);
}
/* ------------------------------------------------------------------------ */
/*
* Receive a LAPB frame via an ethernet interface.
*/
static int lapbeth_rcv(struct sk_buff *skb, struct net_device *dev, struct packet_type *ptype, struct net_device *orig_dev)
{
int len, err;
struct lapbethdev *lapbeth;
if (dev_net(dev) != &init_net)
goto drop;
if ((skb = skb_share_check(skb, GFP_ATOMIC)) == NULL)
return NET_RX_DROP;
if (!pskb_may_pull(skb, 2))
goto drop;
rcu_read_lock();
lapbeth = lapbeth_get_x25_dev(dev);
if (!lapbeth)
goto drop_unlock;
if (!netif_running(lapbeth->axdev))
goto drop_unlock;
len = skb->data[0] + skb->data[1] * 256;
dev->stats.rx_packets++;
dev->stats.rx_bytes += len;
skb_pull(skb, 2); /* Remove the length bytes */
skb_trim(skb, len); /* Set the length of the data */
if ((err = lapb_data_received(lapbeth->axdev, skb)) != LAPB_OK) {
printk(KERN_DEBUG "lapbether: lapb_data_received err - %d\n", err);
goto drop_unlock;
}
out:
rcu_read_unlock();
return 0;
drop_unlock:
kfree_skb(skb);
goto out;
drop:
kfree_skb(skb);
return 0;
}
static int lapbeth_data_indication(struct net_device *dev, struct sk_buff *skb)
{
unsigned char *ptr;
skb_push(skb, 1);
if (skb_cow(skb, 1))
return NET_RX_DROP;
ptr = skb->data;
*ptr = X25_IFACE_DATA;
skb->protocol = x25_type_trans(skb, dev);
return netif_rx(skb);
}
/*
* Send a LAPB frame via an ethernet interface
*/
static netdev_tx_t lapbeth_xmit(struct sk_buff *skb,
struct net_device *dev)
{
int err;
/*
* Just to be *really* sure not to send anything if the interface
* is down, the ethernet device may have gone.
*/
if (!netif_running(dev))
goto drop;
switch (skb->data[0]) {
case X25_IFACE_DATA:
break;
case X25_IFACE_CONNECT:
if ((err = lapb_connect_request(dev)) != LAPB_OK)
pr_err("lapb_connect_request error: %d\n", err);
goto drop;
case X25_IFACE_DISCONNECT:
if ((err = lapb_disconnect_request(dev)) != LAPB_OK)
pr_err("lapb_disconnect_request err: %d\n", err);
/* Fall thru */
default:
goto drop;
}
skb_pull(skb, 1);
if ((err = lapb_data_request(dev, skb)) != LAPB_OK) {
pr_err("lapb_data_request error - %d\n", err);
goto drop;
}
out:
return NETDEV_TX_OK;
drop:
kfree_skb(skb);
goto out;
}
static void lapbeth_data_transmit(struct net_device *ndev, struct sk_buff *skb)
{
struct lapbethdev *lapbeth = netdev_priv(ndev);
unsigned char *ptr;
struct net_device *dev;
int size = skb->len;
skb->protocol = htons(ETH_P_X25);
ptr = skb_push(skb, 2);
*ptr++ = size % 256;
*ptr++ = size / 256;
ndev->stats.tx_packets++;
ndev->stats.tx_bytes += size;
skb->dev = dev = lapbeth->ethdev;
dev_hard_header(skb, dev, ETH_P_DEC, bcast_addr, NULL, 0);
dev_queue_xmit(skb);
}
static void lapbeth_connected(struct net_device *dev, int reason)
{
unsigned char *ptr;
struct sk_buff *skb = dev_alloc_skb(1);
if (!skb) {
pr_err("out of memory\n");
return;
}
ptr = skb_put(skb, 1);
*ptr = X25_IFACE_CONNECT;
skb->protocol = x25_type_trans(skb, dev);
netif_rx(skb);
}
static void lapbeth_disconnected(struct net_device *dev, int reason)
{
unsigned char *ptr;
struct sk_buff *skb = dev_alloc_skb(1);
if (!skb) {
pr_err("out of memory\n");
return;
}
ptr = skb_put(skb, 1);
*ptr = X25_IFACE_DISCONNECT;
skb->protocol = x25_type_trans(skb, dev);
netif_rx(skb);
}
/*
* Set AX.25 callsign
*/
static int lapbeth_set_mac_address(struct net_device *dev, void *addr)
{
struct sockaddr *sa = addr;
memcpy(dev->dev_addr, sa->sa_data, dev->addr_len);
return 0;
}
static const struct lapb_register_struct lapbeth_callbacks = {
.connect_confirmation = lapbeth_connected,
.connect_indication = lapbeth_connected,
.disconnect_confirmation = lapbeth_disconnected,
.disconnect_indication = lapbeth_disconnected,
.data_indication = lapbeth_data_indication,
.data_transmit = lapbeth_data_transmit,
};
/*
* open/close a device
*/
static int lapbeth_open(struct net_device *dev)
{
int err;
if ((err = lapb_register(dev, &lapbeth_callbacks)) != LAPB_OK) {
pr_err("lapb_register error: %d\n", err);
return -ENODEV;
}
netif_start_queue(dev);
return 0;
}
static int lapbeth_close(struct net_device *dev)
{
int err;
netif_stop_queue(dev);
if ((err = lapb_unregister(dev)) != LAPB_OK)
pr_err("lapb_unregister error: %d\n", err);
return 0;
}
/* ------------------------------------------------------------------------ */
static const struct net_device_ops lapbeth_netdev_ops = {
.ndo_open = lapbeth_open,
.ndo_stop = lapbeth_close,
.ndo_start_xmit = lapbeth_xmit,
.ndo_set_mac_address = lapbeth_set_mac_address,
};
static void lapbeth_setup(struct net_device *dev)
{
dev->netdev_ops = &lapbeth_netdev_ops;
dev->needs_free_netdev = true;
dev->type = ARPHRD_X25;
dev->hard_header_len = 3;
dev->mtu = 1000;
dev->addr_len = 0;
}
/*
* Setup a new device.
*/
static int lapbeth_new_device(struct net_device *dev)
{
struct net_device *ndev;
struct lapbethdev *lapbeth;
int rc = -ENOMEM;
ASSERT_RTNL();
ndev = alloc_netdev(sizeof(*lapbeth), "lapb%d", NET_NAME_UNKNOWN,
lapbeth_setup);
if (!ndev)
goto out;
lapbeth = netdev_priv(ndev);
lapbeth->axdev = ndev;
dev_hold(dev);
lapbeth->ethdev = dev;
rc = -EIO;
if (register_netdevice(ndev))
goto fail;
list_add_rcu(&lapbeth->node, &lapbeth_devices);
rc = 0;
out:
return rc;
fail:
dev_put(dev);
free_netdev(ndev);
kfree(lapbeth);
goto out;
}
/*
* Free a lapb network device.
*/
static void lapbeth_free_device(struct lapbethdev *lapbeth)
{
dev_put(lapbeth->ethdev);
list_del_rcu(&lapbeth->node);
unregister_netdevice(lapbeth->axdev);
}
/*
* Handle device status changes.
*
* Called from notifier with RTNL held.
*/
static int lapbeth_device_event(struct notifier_block *this,
unsigned long event, void *ptr)
{
struct lapbethdev *lapbeth;
struct net_device *dev = netdev_notifier_info_to_dev(ptr);
if (dev_net(dev) != &init_net)
return NOTIFY_DONE;
if (!dev_is_ethdev(dev))
return NOTIFY_DONE;
switch (event) {
case NETDEV_UP:
/* New ethernet device -> new LAPB interface */
if (lapbeth_get_x25_dev(dev) == NULL)
lapbeth_new_device(dev);
break;
case NETDEV_DOWN:
/* ethernet device closed -> close LAPB interface */
lapbeth = lapbeth_get_x25_dev(dev);
if (lapbeth)
dev_close(lapbeth->axdev);
break;
case NETDEV_UNREGISTER:
/* ethernet device disappears -> remove LAPB interface */
lapbeth = lapbeth_get_x25_dev(dev);
if (lapbeth)
lapbeth_free_device(lapbeth);
break;
}
return NOTIFY_DONE;
}
/* ------------------------------------------------------------------------ */
static struct packet_type lapbeth_packet_type __read_mostly = {
.type = cpu_to_be16(ETH_P_DEC),
.func = lapbeth_rcv,
};
static struct notifier_block lapbeth_dev_notifier = {
.notifier_call = lapbeth_device_event,
};
static const char banner[] __initconst =
KERN_INFO "LAPB Ethernet driver version 0.02\n";
static int __init lapbeth_init_driver(void)
{
dev_add_pack(&lapbeth_packet_type);
register_netdevice_notifier(&lapbeth_dev_notifier);
printk(banner);
return 0;
}
module_init(lapbeth_init_driver);
static void __exit lapbeth_cleanup_driver(void)
{
struct lapbethdev *lapbeth;
struct list_head *entry, *tmp;
dev_remove_pack(&lapbeth_packet_type);
unregister_netdevice_notifier(&lapbeth_dev_notifier);
rtnl_lock();
list_for_each_safe(entry, tmp, &lapbeth_devices) {
lapbeth = list_entry(entry, struct lapbethdev, node);
dev_put(lapbeth->ethdev);
unregister_netdevice(lapbeth->axdev);
}
rtnl_unlock();
}
module_exit(lapbeth_cleanup_driver);
MODULE_AUTHOR("Jonathan Naylor <g4klx@g4klx.demon.co.uk>");
MODULE_DESCRIPTION("The unofficial LAPB over Ethernet driver");
MODULE_LICENSE("GPL");