1/* dummy.c: a dummy net driver
2
3	The purpose of this driver is to provide a device to point a
4	route through, but not to actually transmit packets.
5
6	Why?  If you have a machine whose only connection is an occasional
7	PPP/SLIP/PLIP link, you can only connect to your own hostname
8	when the link is up.  Otherwise you have to use localhost.
9	This isn't very consistent.
10
11	One solution is to set up a dummy link using PPP/SLIP/PLIP,
12	but this seems (to me) too much overhead for too little gain.
13	This driver provides a small alternative. Thus you can do
14
15	[when not running slip]
16		ifconfig dummy slip.addr.ess.here up
17	[to go to slip]
18		ifconfig dummy down
19		dip whatever
20
21	This was written by looking at Donald Becker's skeleton driver
22	and the loopback driver.  I then threw away anything that didn't
23	apply!	Thanks to Alan Cox for the key clue on what to do with
24	misguided packets.
25
26			Nick Holloway, 27th May 1994
27	[I tweaked this explanation a little but that's all]
28			Alan Cox, 30th May 1994
29*/
30
31#include <linux/module.h>
32#include <linux/kernel.h>
33#include <linux/netdevice.h>
34#include <linux/etherdevice.h>
35#include <linux/init.h>
36#include <linux/moduleparam.h>
37#include <linux/rtnetlink.h>
38#include <net/rtnetlink.h>
39#include <linux/u64_stats_sync.h>
40
41#define DRV_NAME	"dummy"
42#define DRV_VERSION	"1.0"
43
44static int numdummies = 1;
45
46/* fake multicast ability */
47static void set_multicast_list(struct net_device *dev)
48{
49}
50
51struct pcpu_dstats {
52	u64			tx_packets;
53	u64			tx_bytes;
54	struct u64_stats_sync	syncp;
55};
56
57static struct rtnl_link_stats64 *dummy_get_stats64(struct net_device *dev,
58						   struct rtnl_link_stats64 *stats)
59{
60	int i;
61
62	for_each_possible_cpu(i) {
63		const struct pcpu_dstats *dstats;
64		u64 tbytes, tpackets;
65		unsigned int start;
66
67		dstats = per_cpu_ptr(dev->dstats, i);
68		do {
69			start = u64_stats_fetch_begin_irq(&dstats->syncp);
70			tbytes = dstats->tx_bytes;
71			tpackets = dstats->tx_packets;
72		} while (u64_stats_fetch_retry_irq(&dstats->syncp, start));
73		stats->tx_bytes += tbytes;
74		stats->tx_packets += tpackets;
75	}
76	return stats;
77}
78
79static netdev_tx_t dummy_xmit(struct sk_buff *skb, struct net_device *dev)
80{
81	struct pcpu_dstats *dstats = this_cpu_ptr(dev->dstats);
82
83	u64_stats_update_begin(&dstats->syncp);
84	dstats->tx_packets++;
85	dstats->tx_bytes += skb->len;
86	u64_stats_update_end(&dstats->syncp);
87
88	dev_kfree_skb(skb);
89	return NETDEV_TX_OK;
90}
91
92static int dummy_dev_init(struct net_device *dev)
93{
94	dev->dstats = netdev_alloc_pcpu_stats(struct pcpu_dstats);
95	if (!dev->dstats)
96		return -ENOMEM;
97
98	return 0;
99}
100
101static void dummy_dev_uninit(struct net_device *dev)
102{
103	free_percpu(dev->dstats);
104}
105
106static int dummy_change_carrier(struct net_device *dev, bool new_carrier)
107{
108	if (new_carrier)
109		netif_carrier_on(dev);
110	else
111		netif_carrier_off(dev);
112	return 0;
113}
114
115static const struct net_device_ops dummy_netdev_ops = {
116	.ndo_init		= dummy_dev_init,
117	.ndo_uninit		= dummy_dev_uninit,
118	.ndo_start_xmit		= dummy_xmit,
119	.ndo_validate_addr	= eth_validate_addr,
120	.ndo_set_rx_mode	= set_multicast_list,
121	.ndo_set_mac_address	= eth_mac_addr,
122	.ndo_get_stats64	= dummy_get_stats64,
123	.ndo_change_carrier	= dummy_change_carrier,
124};
125
126static void dummy_get_drvinfo(struct net_device *dev,
127			      struct ethtool_drvinfo *info)
128{
129	strlcpy(info->driver, DRV_NAME, sizeof(info->driver));
130	strlcpy(info->version, DRV_VERSION, sizeof(info->version));
131}
132
133static const struct ethtool_ops dummy_ethtool_ops = {
134	.get_drvinfo            = dummy_get_drvinfo,
135};
136
137static void dummy_setup(struct net_device *dev)
138{
139	ether_setup(dev);
140
141	/* Initialize the device structure. */
142	dev->netdev_ops = &dummy_netdev_ops;
143	dev->ethtool_ops = &dummy_ethtool_ops;
144	dev->destructor = free_netdev;
145
146	/* Fill in device structure with ethernet-generic values. */
147	dev->tx_queue_len = 0;
148	dev->flags |= IFF_NOARP;
149	dev->flags &= ~IFF_MULTICAST;
150	dev->priv_flags |= IFF_LIVE_ADDR_CHANGE;
151	dev->features	|= NETIF_F_SG | NETIF_F_FRAGLIST | NETIF_F_TSO;
152	dev->features	|= NETIF_F_HW_CSUM | NETIF_F_HIGHDMA | NETIF_F_LLTX;
153	eth_hw_addr_random(dev);
154}
155
156static int dummy_validate(struct nlattr *tb[], struct nlattr *data[])
157{
158	if (tb[IFLA_ADDRESS]) {
159		if (nla_len(tb[IFLA_ADDRESS]) != ETH_ALEN)
160			return -EINVAL;
161		if (!is_valid_ether_addr(nla_data(tb[IFLA_ADDRESS])))
162			return -EADDRNOTAVAIL;
163	}
164	return 0;
165}
166
167static struct rtnl_link_ops dummy_link_ops __read_mostly = {
168	.kind		= DRV_NAME,
169	.setup		= dummy_setup,
170	.validate	= dummy_validate,
171};
172
173/* Number of dummy devices to be set up by this module. */
174module_param(numdummies, int, 0);
175MODULE_PARM_DESC(numdummies, "Number of dummy pseudo devices");
176
177static int __init dummy_init_one(void)
178{
179	struct net_device *dev_dummy;
180	int err;
181
182	dev_dummy = alloc_netdev(0, "dummy%d", NET_NAME_UNKNOWN, dummy_setup);
183	if (!dev_dummy)
184		return -ENOMEM;
185
186	dev_dummy->rtnl_link_ops = &dummy_link_ops;
187	err = register_netdevice(dev_dummy);
188	if (err < 0)
189		goto err;
190	return 0;
191
192err:
193	free_netdev(dev_dummy);
194	return err;
195}
196
197static int __init dummy_init_module(void)
198{
199	int i, err = 0;
200
201	rtnl_lock();
202	err = __rtnl_link_register(&dummy_link_ops);
203	if (err < 0)
204		goto out;
205
206	for (i = 0; i < numdummies && !err; i++) {
207		err = dummy_init_one();
208		cond_resched();
209	}
210	if (err < 0)
211		__rtnl_link_unregister(&dummy_link_ops);
212
213out:
214	rtnl_unlock();
215
216	return err;
217}
218
219static void __exit dummy_cleanup_module(void)
220{
221	rtnl_link_unregister(&dummy_link_ops);
222}
223
224module_init(dummy_init_module);
225module_exit(dummy_cleanup_module);
226MODULE_LICENSE("GPL");
227MODULE_ALIAS_RTNL_LINK(DRV_NAME);
228MODULE_VERSION(DRV_VERSION);
229