linux/drivers/net/dummy.c
Kirill Tkhai 554873e517 net: Do not take net_rwsem in __rtnl_link_unregister()
This function calls call_netdevice_notifier(), which also
may take net_rwsem. So, we can't use net_rwsem here.

This patch makes callers of this functions take pernet_ops_rwsem,
like register_netdevice_notifier() does. This will protect
the modifications of net_namespace_list, and allows notifiers
to take it (they won't have to care about context).

Since __rtnl_link_unregister() is used on module load
and unload (which are not frequent operations), this looks
for me better, than make all call_netdevice_notifier()
always executing in "protected net_namespace_list" context.

Also, this fixes the problem we had a deal in 328fbe747a
"Close race between {un, }register_netdevice_notifier and ...",
and guarantees __rtnl_link_unregister() does not skip
exitting net.

Signed-off-by: Kirill Tkhai <ktkhai@virtuozzo.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
2018-03-31 22:24:58 -04:00

252 lines
6.0 KiB
C

/* dummy.c: a dummy net driver
The purpose of this driver is to provide a device to point a
route through, but not to actually transmit packets.
Why? If you have a machine whose only connection is an occasional
PPP/SLIP/PLIP link, you can only connect to your own hostname
when the link is up. Otherwise you have to use localhost.
This isn't very consistent.
One solution is to set up a dummy link using PPP/SLIP/PLIP,
but this seems (to me) too much overhead for too little gain.
This driver provides a small alternative. Thus you can do
[when not running slip]
ifconfig dummy slip.addr.ess.here up
[to go to slip]
ifconfig dummy down
dip whatever
This was written by looking at Donald Becker's skeleton driver
and the loopback driver. I then threw away anything that didn't
apply! Thanks to Alan Cox for the key clue on what to do with
misguided packets.
Nick Holloway, 27th May 1994
[I tweaked this explanation a little but that's all]
Alan Cox, 30th May 1994
*/
#include <linux/module.h>
#include <linux/kernel.h>
#include <linux/netdevice.h>
#include <linux/etherdevice.h>
#include <linux/init.h>
#include <linux/moduleparam.h>
#include <linux/rtnetlink.h>
#include <linux/net_tstamp.h>
#include <net/rtnetlink.h>
#include <linux/u64_stats_sync.h>
#define DRV_NAME "dummy"
#define DRV_VERSION "1.0"
static int numdummies = 1;
/* fake multicast ability */
static void set_multicast_list(struct net_device *dev)
{
}
struct pcpu_dstats {
u64 tx_packets;
u64 tx_bytes;
struct u64_stats_sync syncp;
};
static void dummy_get_stats64(struct net_device *dev,
struct rtnl_link_stats64 *stats)
{
int i;
for_each_possible_cpu(i) {
const struct pcpu_dstats *dstats;
u64 tbytes, tpackets;
unsigned int start;
dstats = per_cpu_ptr(dev->dstats, i);
do {
start = u64_stats_fetch_begin_irq(&dstats->syncp);
tbytes = dstats->tx_bytes;
tpackets = dstats->tx_packets;
} while (u64_stats_fetch_retry_irq(&dstats->syncp, start));
stats->tx_bytes += tbytes;
stats->tx_packets += tpackets;
}
}
static netdev_tx_t dummy_xmit(struct sk_buff *skb, struct net_device *dev)
{
struct pcpu_dstats *dstats = this_cpu_ptr(dev->dstats);
u64_stats_update_begin(&dstats->syncp);
dstats->tx_packets++;
dstats->tx_bytes += skb->len;
u64_stats_update_end(&dstats->syncp);
skb_tx_timestamp(skb);
dev_kfree_skb(skb);
return NETDEV_TX_OK;
}
static int dummy_dev_init(struct net_device *dev)
{
dev->dstats = netdev_alloc_pcpu_stats(struct pcpu_dstats);
if (!dev->dstats)
return -ENOMEM;
return 0;
}
static void dummy_dev_uninit(struct net_device *dev)
{
free_percpu(dev->dstats);
}
static int dummy_change_carrier(struct net_device *dev, bool new_carrier)
{
if (new_carrier)
netif_carrier_on(dev);
else
netif_carrier_off(dev);
return 0;
}
static const struct net_device_ops dummy_netdev_ops = {
.ndo_init = dummy_dev_init,
.ndo_uninit = dummy_dev_uninit,
.ndo_start_xmit = dummy_xmit,
.ndo_validate_addr = eth_validate_addr,
.ndo_set_rx_mode = set_multicast_list,
.ndo_set_mac_address = eth_mac_addr,
.ndo_get_stats64 = dummy_get_stats64,
.ndo_change_carrier = dummy_change_carrier,
};
static void dummy_get_drvinfo(struct net_device *dev,
struct ethtool_drvinfo *info)
{
strlcpy(info->driver, DRV_NAME, sizeof(info->driver));
strlcpy(info->version, DRV_VERSION, sizeof(info->version));
}
static int dummy_get_ts_info(struct net_device *dev,
struct ethtool_ts_info *ts_info)
{
ts_info->so_timestamping = SOF_TIMESTAMPING_TX_SOFTWARE |
SOF_TIMESTAMPING_RX_SOFTWARE |
SOF_TIMESTAMPING_SOFTWARE;
ts_info->phc_index = -1;
return 0;
};
static const struct ethtool_ops dummy_ethtool_ops = {
.get_drvinfo = dummy_get_drvinfo,
.get_ts_info = dummy_get_ts_info,
};
static void dummy_setup(struct net_device *dev)
{
ether_setup(dev);
/* Initialize the device structure. */
dev->netdev_ops = &dummy_netdev_ops;
dev->ethtool_ops = &dummy_ethtool_ops;
dev->needs_free_netdev = true;
/* Fill in device structure with ethernet-generic values. */
dev->flags |= IFF_NOARP;
dev->flags &= ~IFF_MULTICAST;
dev->priv_flags |= IFF_LIVE_ADDR_CHANGE | IFF_NO_QUEUE;
dev->features |= NETIF_F_SG | NETIF_F_FRAGLIST;
dev->features |= NETIF_F_ALL_TSO;
dev->features |= NETIF_F_HW_CSUM | NETIF_F_HIGHDMA | NETIF_F_LLTX;
dev->features |= NETIF_F_GSO_ENCAP_ALL;
dev->hw_features |= dev->features;
dev->hw_enc_features |= dev->features;
eth_hw_addr_random(dev);
dev->min_mtu = 0;
dev->max_mtu = 0;
}
static int dummy_validate(struct nlattr *tb[], struct nlattr *data[],
struct netlink_ext_ack *extack)
{
if (tb[IFLA_ADDRESS]) {
if (nla_len(tb[IFLA_ADDRESS]) != ETH_ALEN)
return -EINVAL;
if (!is_valid_ether_addr(nla_data(tb[IFLA_ADDRESS])))
return -EADDRNOTAVAIL;
}
return 0;
}
static struct rtnl_link_ops dummy_link_ops __read_mostly = {
.kind = DRV_NAME,
.setup = dummy_setup,
.validate = dummy_validate,
};
/* Number of dummy devices to be set up by this module. */
module_param(numdummies, int, 0);
MODULE_PARM_DESC(numdummies, "Number of dummy pseudo devices");
static int __init dummy_init_one(void)
{
struct net_device *dev_dummy;
int err;
dev_dummy = alloc_netdev(0, "dummy%d", NET_NAME_ENUM, dummy_setup);
if (!dev_dummy)
return -ENOMEM;
dev_dummy->rtnl_link_ops = &dummy_link_ops;
err = register_netdevice(dev_dummy);
if (err < 0)
goto err;
return 0;
err:
free_netdev(dev_dummy);
return err;
}
static int __init dummy_init_module(void)
{
int i, err = 0;
down_write(&pernet_ops_rwsem);
rtnl_lock();
err = __rtnl_link_register(&dummy_link_ops);
if (err < 0)
goto out;
for (i = 0; i < numdummies && !err; i++) {
err = dummy_init_one();
cond_resched();
}
if (err < 0)
__rtnl_link_unregister(&dummy_link_ops);
out:
rtnl_unlock();
up_write(&pernet_ops_rwsem);
return err;
}
static void __exit dummy_cleanup_module(void)
{
rtnl_link_unregister(&dummy_link_ops);
}
module_init(dummy_init_module);
module_exit(dummy_cleanup_module);
MODULE_LICENSE("GPL");
MODULE_ALIAS_RTNL_LINK(DRV_NAME);
MODULE_VERSION(DRV_VERSION);