1 /* dummy.c: a dummy net driver
3 The purpose of this driver is to provide a device to point a
4 route through, but not to actually transmit packets.
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.
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
15 [when not running slip]
16 ifconfig dummy slip.addr.ess.here up
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
26 Nick Holloway, 27th May 1994
27 [I tweaked this explanation a little but that's all]
28 Alan Cox, 30th May 1994
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>
41 static int numdummies = 1;
43 static int dummy_set_address(struct net_device *dev, void *p)
45 struct sockaddr *sa = p;
47 if (!is_valid_ether_addr(sa->sa_data))
48 return -EADDRNOTAVAIL;
50 memcpy(dev->dev_addr, sa->sa_data, ETH_ALEN);
54 /* fake multicast ability */
55 static void set_multicast_list(struct net_device *dev)
62 struct u64_stats_sync syncp;
65 static struct rtnl_link_stats64 *dummy_get_stats64(struct net_device *dev,
66 struct rtnl_link_stats64 *stats)
70 for_each_possible_cpu(i) {
71 const struct pcpu_dstats *dstats;
75 dstats = per_cpu_ptr(dev->dstats, i);
77 start = u64_stats_fetch_begin(&dstats->syncp);
78 tbytes = dstats->tx_bytes;
79 tpackets = dstats->tx_packets;
80 } while (u64_stats_fetch_retry(&dstats->syncp, start));
81 stats->tx_bytes += tbytes;
82 stats->tx_packets += tpackets;
87 static netdev_tx_t dummy_xmit(struct sk_buff *skb, struct net_device *dev)
89 struct pcpu_dstats *dstats = this_cpu_ptr(dev->dstats);
91 u64_stats_update_begin(&dstats->syncp);
93 dstats->tx_bytes += skb->len;
94 u64_stats_update_end(&dstats->syncp);
100 static int dummy_dev_init(struct net_device *dev)
102 dev->dstats = alloc_percpu(struct pcpu_dstats);
109 static void dummy_dev_free(struct net_device *dev)
111 free_percpu(dev->dstats);
115 static const struct net_device_ops dummy_netdev_ops = {
116 .ndo_init = dummy_dev_init,
117 .ndo_start_xmit = dummy_xmit,
118 .ndo_validate_addr = eth_validate_addr,
119 .ndo_set_rx_mode = set_multicast_list,
120 .ndo_set_mac_address = dummy_set_address,
121 .ndo_get_stats64 = dummy_get_stats64,
124 static void dummy_setup(struct net_device *dev)
128 /* Initialize the device structure. */
129 dev->netdev_ops = &dummy_netdev_ops;
130 dev->destructor = dummy_dev_free;
132 /* Fill in device structure with ethernet-generic values. */
133 dev->tx_queue_len = 0;
134 dev->flags |= IFF_NOARP;
135 dev->flags &= ~IFF_MULTICAST;
136 dev->features |= NETIF_F_SG | NETIF_F_FRAGLIST | NETIF_F_TSO;
137 dev->features |= NETIF_F_HW_CSUM | NETIF_F_HIGHDMA | NETIF_F_LLTX;
138 random_ether_addr(dev->dev_addr);
141 static int dummy_validate(struct nlattr *tb[], struct nlattr *data[])
143 if (tb[IFLA_ADDRESS]) {
144 if (nla_len(tb[IFLA_ADDRESS]) != ETH_ALEN)
146 if (!is_valid_ether_addr(nla_data(tb[IFLA_ADDRESS])))
147 return -EADDRNOTAVAIL;
152 static struct rtnl_link_ops dummy_link_ops __read_mostly = {
154 .setup = dummy_setup,
155 .validate = dummy_validate,
158 /* Number of dummy devices to be set up by this module. */
159 module_param(numdummies, int, 0);
160 MODULE_PARM_DESC(numdummies, "Number of dummy pseudo devices");
162 static int __init dummy_init_one(void)
164 struct net_device *dev_dummy;
167 dev_dummy = alloc_netdev(0, "dummy%d", dummy_setup);
171 dev_dummy->rtnl_link_ops = &dummy_link_ops;
172 err = register_netdevice(dev_dummy);
178 free_netdev(dev_dummy);
182 static int __init dummy_init_module(void)
187 err = __rtnl_link_register(&dummy_link_ops);
189 for (i = 0; i < numdummies && !err; i++)
190 err = dummy_init_one();
192 __rtnl_link_unregister(&dummy_link_ops);
198 static void __exit dummy_cleanup_module(void)
200 rtnl_link_unregister(&dummy_link_ops);
203 module_init(dummy_init_module);
204 module_exit(dummy_cleanup_module);
205 MODULE_LICENSE("GPL");
206 MODULE_ALIAS_RTNL_LINK("dummy");