linux-stable/drivers/net/dummy.c
John Stultz 827da44c61 net: Explicitly initialize u64_stats_sync structures for lockdep
In order to enable lockdep on seqcount/seqlock structures, we
must explicitly initialize any locks.

The u64_stats_sync structure, uses a seqcount, and thus we need
to introduce a u64_stats_init() function and use it to initialize
the structure.

This unfortunately adds a lot of fairly trivial initialization code
to a number of drivers. But the benefit of ensuring correctness makes
this worth while.

Because these changes are required for lockdep to be enabled, and the
changes are quite trivial, I've not yet split this patch out into 30-some
separate patches, as I figured it would be better to get the various
maintainers thoughts on how to best merge this change along with
the seqcount lockdep enablement.

Feedback would be appreciated!

Signed-off-by: John Stultz <john.stultz@linaro.org>
Acked-by: Julian Anastasov <ja@ssi.bg>
Signed-off-by: Peter Zijlstra <peterz@infradead.org>
Cc: Alexey Kuznetsov <kuznet@ms2.inr.ac.ru>
Cc: "David S. Miller" <davem@davemloft.net>
Cc: Eric Dumazet <eric.dumazet@gmail.com>
Cc: Hideaki YOSHIFUJI <yoshfuji@linux-ipv6.org>
Cc: James Morris <jmorris@namei.org>
Cc: Jesse Gross <jesse@nicira.com>
Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Cc: "Michael S. Tsirkin" <mst@redhat.com>
Cc: Mirko Lindner <mlindner@marvell.com>
Cc: Patrick McHardy <kaber@trash.net>
Cc: Roger Luethi <rl@hellgate.ch>
Cc: Rusty Russell <rusty@rustcorp.com.au>
Cc: Simon Horman <horms@verge.net.au>
Cc: Stephen Hemminger <stephen@networkplumber.org>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>
Cc: Wensong Zhang <wensong@linux-vs.org>
Cc: netdev@vger.kernel.org
Link: http://lkml.kernel.org/r/1381186321-4906-2-git-send-email-john.stultz@linaro.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>
2013-11-06 12:40:25 +01:00

218 lines
5.1 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 <net/rtnetlink.h>
#include <linux/u64_stats_sync.h>
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 struct rtnl_link_stats64 *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_bh(&dstats->syncp);
tbytes = dstats->tx_bytes;
tpackets = dstats->tx_packets;
} while (u64_stats_fetch_retry_bh(&dstats->syncp, start));
stats->tx_bytes += tbytes;
stats->tx_packets += tpackets;
}
return stats;
}
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);
dev_kfree_skb(skb);
return NETDEV_TX_OK;
}
static int dummy_dev_init(struct net_device *dev)
{
int i;
dev->dstats = alloc_percpu(struct pcpu_dstats);
if (!dev->dstats)
return -ENOMEM;
for_each_possible_cpu(i) {
struct pcpu_dstats *dstats;
dstats = per_cpu_ptr(dev->dstats, i);
u64_stats_init(&dstats->syncp);
}
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_setup(struct net_device *dev)
{
ether_setup(dev);
/* Initialize the device structure. */
dev->netdev_ops = &dummy_netdev_ops;
dev->destructor = free_netdev;
/* Fill in device structure with ethernet-generic values. */
dev->tx_queue_len = 0;
dev->flags |= IFF_NOARP;
dev->flags &= ~IFF_MULTICAST;
dev->priv_flags |= IFF_LIVE_ADDR_CHANGE;
dev->features |= NETIF_F_SG | NETIF_F_FRAGLIST | NETIF_F_TSO;
dev->features |= NETIF_F_HW_CSUM | NETIF_F_HIGHDMA | NETIF_F_LLTX;
eth_hw_addr_random(dev);
}
static int dummy_validate(struct nlattr *tb[], struct nlattr *data[])
{
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 = "dummy",
.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", 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;
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();
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("dummy");