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 <linux/net_tstamp.h>
39#include <net/rtnetlink.h>
40#include <linux/u64_stats_sync.h>
41
42#define DRV_NAME "dummy"
43#define DRV_VERSION "1.0"
44
45static int numdummies = 1;
46
47/* fake multicast ability */
48static void set_multicast_list(struct net_device *dev)
49{
50}
51
52struct pcpu_dstats {
53 u64 tx_packets;
54 u64 tx_bytes;
55 struct u64_stats_sync syncp;
56};
57
58static void dummy_get_stats64(struct net_device *dev,
59 struct rtnl_link_stats64 *stats)
60{
61 int i;
62
63 for_each_possible_cpu(i) {
64 const struct pcpu_dstats *dstats;
65 u64 tbytes, tpackets;
66 unsigned int start;
67
68 dstats = per_cpu_ptr(dev->dstats, i);
69 do {
70 start = u64_stats_fetch_begin_irq(&dstats->syncp);
71 tbytes = dstats->tx_bytes;
72 tpackets = dstats->tx_packets;
73 } while (u64_stats_fetch_retry_irq(&dstats->syncp, start));
74 stats->tx_bytes += tbytes;
75 stats->tx_packets += tpackets;
76 }
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 skb_tx_timestamp(skb);
89 dev_kfree_skb(skb);
90 return NETDEV_TX_OK;
91}
92
93static int dummy_dev_init(struct net_device *dev)
94{
95 dev->dstats = netdev_alloc_pcpu_stats(struct pcpu_dstats);
96 if (!dev->dstats)
97 return -ENOMEM;
98
99 return 0;
100}
101
102static void dummy_dev_uninit(struct net_device *dev)
103{
104 free_percpu(dev->dstats);
105}
106
107static int dummy_change_carrier(struct net_device *dev, bool new_carrier)
108{
109 if (new_carrier)
110 netif_carrier_on(dev);
111 else
112 netif_carrier_off(dev);
113 return 0;
114}
115
116static const struct net_device_ops dummy_netdev_ops = {
117 .ndo_init = dummy_dev_init,
118 .ndo_uninit = dummy_dev_uninit,
119 .ndo_start_xmit = dummy_xmit,
120 .ndo_validate_addr = eth_validate_addr,
121 .ndo_set_rx_mode = set_multicast_list,
122 .ndo_set_mac_address = eth_mac_addr,
123 .ndo_get_stats64 = dummy_get_stats64,
124 .ndo_change_carrier = dummy_change_carrier,
125};
126
127static void dummy_get_drvinfo(struct net_device *dev,
128 struct ethtool_drvinfo *info)
129{
130 strlcpy(info->driver, DRV_NAME, sizeof(info->driver));
131 strlcpy(info->version, DRV_VERSION, sizeof(info->version));
132}
133
134static int dummy_get_ts_info(struct net_device *dev,
135 struct ethtool_ts_info *ts_info)
136{
137 ts_info->so_timestamping = SOF_TIMESTAMPING_TX_SOFTWARE |
138 SOF_TIMESTAMPING_RX_SOFTWARE |
139 SOF_TIMESTAMPING_SOFTWARE;
140
141 ts_info->phc_index = -1;
142
143 return 0;
144};
145
146static const struct ethtool_ops dummy_ethtool_ops = {
147 .get_drvinfo = dummy_get_drvinfo,
148 .get_ts_info = dummy_get_ts_info,
149};
150
151static void dummy_setup(struct net_device *dev)
152{
153 ether_setup(dev);
154
155 /* Initialize the device structure. */
156 dev->netdev_ops = &dummy_netdev_ops;
157 dev->ethtool_ops = &dummy_ethtool_ops;
158 dev->needs_free_netdev = true;
159
160 /* Fill in device structure with ethernet-generic values. */
161 dev->flags |= IFF_NOARP;
162 dev->flags &= ~IFF_MULTICAST;
163 dev->priv_flags |= IFF_LIVE_ADDR_CHANGE | IFF_NO_QUEUE;
164 dev->features |= NETIF_F_SG | NETIF_F_FRAGLIST;
165 dev->features |= NETIF_F_ALL_TSO;
166 dev->features |= NETIF_F_HW_CSUM | NETIF_F_HIGHDMA | NETIF_F_LLTX;
167 dev->features |= NETIF_F_GSO_ENCAP_ALL;
168 dev->hw_features |= dev->features;
169 dev->hw_enc_features |= dev->features;
170 eth_hw_addr_random(dev);
171
172 dev->min_mtu = 0;
173 dev->max_mtu = 0;
174}
175
176static int dummy_validate(struct nlattr *tb[], struct nlattr *data[],
177 struct netlink_ext_ack *extack)
178{
179 if (tb[IFLA_ADDRESS]) {
180 if (nla_len(tb[IFLA_ADDRESS]) != ETH_ALEN)
181 return -EINVAL;
182 if (!is_valid_ether_addr(nla_data(tb[IFLA_ADDRESS])))
183 return -EADDRNOTAVAIL;
184 }
185 return 0;
186}
187
188static struct rtnl_link_ops dummy_link_ops __read_mostly = {
189 .kind = DRV_NAME,
190 .setup = dummy_setup,
191 .validate = dummy_validate,
192};
193
194/* Number of dummy devices to be set up by this module. */
195module_param(numdummies, int, 0);
196MODULE_PARM_DESC(numdummies, "Number of dummy pseudo devices");
197
198static int __init dummy_init_one(void)
199{
200 struct net_device *dev_dummy;
201 int err;
202
203 dev_dummy = alloc_netdev(0, "dummy%d", NET_NAME_ENUM, dummy_setup);
204 if (!dev_dummy)
205 return -ENOMEM;
206
207 dev_dummy->rtnl_link_ops = &dummy_link_ops;
208 err = register_netdevice(dev_dummy);
209 if (err < 0)
210 goto err;
211 return 0;
212
213err:
214 free_netdev(dev_dummy);
215 return err;
216}
217
218static int __init dummy_init_module(void)
219{
220 int i, err = 0;
221
222 down_write(&pernet_ops_rwsem);
223 rtnl_lock();
224 err = __rtnl_link_register(&dummy_link_ops);
225 if (err < 0)
226 goto out;
227
228 for (i = 0; i < numdummies && !err; i++) {
229 err = dummy_init_one();
230 cond_resched();
231 }
232 if (err < 0)
233 __rtnl_link_unregister(&dummy_link_ops);
234
235out:
236 rtnl_unlock();
237 up_write(&pernet_ops_rwsem);
238
239 return err;
240}
241
242static void __exit dummy_cleanup_module(void)
243{
244 rtnl_link_unregister(&dummy_link_ops);
245}
246
247module_init(dummy_init_module);
248module_exit(dummy_cleanup_module);
249MODULE_LICENSE("GPL");
250MODULE_ALIAS_RTNL_LINK(DRV_NAME);
251MODULE_VERSION(DRV_VERSION);
252