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/ethtool.h>
36 #include <linux/init.h>
37 #include <linux/moduleparam.h>
38 #include <linux/rtnetlink.h>
39 #include <linux/net_tstamp.h>
40 #include <net/rtnetlink.h>
41 #include <linux/u64_stats_sync.h>
43 #define DRV_NAME "dummy"
44 #define DRV_VERSION "1.0"
46 static int numdummies = 1;
48 /* fake multicast ability */
49 static void set_multicast_list(struct net_device *dev)
56 struct u64_stats_sync syncp;
59 static void dummy_get_stats64(struct net_device *dev,
60 struct rtnl_link_stats64 *stats)
64 for_each_possible_cpu(i) {
65 const struct pcpu_dstats *dstats;
69 dstats = per_cpu_ptr(dev->dstats, i);
71 start = u64_stats_fetch_begin_irq(&dstats->syncp);
72 tbytes = dstats->tx_bytes;
73 tpackets = dstats->tx_packets;
74 } while (u64_stats_fetch_retry_irq(&dstats->syncp, start));
75 stats->tx_bytes += tbytes;
76 stats->tx_packets += tpackets;
80 static netdev_tx_t dummy_xmit(struct sk_buff *skb, struct net_device *dev)
82 struct pcpu_dstats *dstats = this_cpu_ptr(dev->dstats);
84 u64_stats_update_begin(&dstats->syncp);
86 dstats->tx_bytes += skb->len;
87 u64_stats_update_end(&dstats->syncp);
89 skb_tx_timestamp(skb);
94 static int dummy_dev_init(struct net_device *dev)
96 dev->dstats = netdev_alloc_pcpu_stats(struct pcpu_dstats);
103 static void dummy_dev_uninit(struct net_device *dev)
105 free_percpu(dev->dstats);
108 static int dummy_change_carrier(struct net_device *dev, bool new_carrier)
111 netif_carrier_on(dev);
113 netif_carrier_off(dev);
117 static const struct net_device_ops dummy_netdev_ops = {
118 .ndo_init = dummy_dev_init,
119 .ndo_uninit = dummy_dev_uninit,
120 .ndo_start_xmit = dummy_xmit,
121 .ndo_validate_addr = eth_validate_addr,
122 .ndo_set_rx_mode = set_multicast_list,
123 .ndo_set_mac_address = eth_mac_addr,
124 .ndo_get_stats64 = dummy_get_stats64,
125 .ndo_change_carrier = dummy_change_carrier,
128 static void dummy_get_drvinfo(struct net_device *dev,
129 struct ethtool_drvinfo *info)
131 strlcpy(info->driver, DRV_NAME, sizeof(info->driver));
132 strlcpy(info->version, DRV_VERSION, sizeof(info->version));
135 static const struct ethtool_ops dummy_ethtool_ops = {
136 .get_drvinfo = dummy_get_drvinfo,
137 .get_ts_info = ethtool_op_get_ts_info,
140 static void dummy_setup(struct net_device *dev)
144 /* Initialize the device structure. */
145 dev->netdev_ops = &dummy_netdev_ops;
146 dev->ethtool_ops = &dummy_ethtool_ops;
147 dev->needs_free_netdev = true;
149 /* Fill in device structure with ethernet-generic values. */
150 dev->flags |= IFF_NOARP;
151 dev->flags &= ~IFF_MULTICAST;
152 dev->priv_flags |= IFF_LIVE_ADDR_CHANGE | IFF_NO_QUEUE;
153 dev->features |= NETIF_F_SG | NETIF_F_FRAGLIST;
154 dev->features |= NETIF_F_ALL_TSO;
155 dev->features |= NETIF_F_HW_CSUM | NETIF_F_HIGHDMA | NETIF_F_LLTX;
156 dev->features |= NETIF_F_GSO_ENCAP_ALL;
157 dev->hw_features |= dev->features;
158 dev->hw_enc_features |= dev->features;
159 eth_hw_addr_random(dev);
165 static int dummy_validate(struct nlattr *tb[], struct nlattr *data[],
166 struct netlink_ext_ack *extack)
168 if (tb[IFLA_ADDRESS]) {
169 if (nla_len(tb[IFLA_ADDRESS]) != ETH_ALEN)
171 if (!is_valid_ether_addr(nla_data(tb[IFLA_ADDRESS])))
172 return -EADDRNOTAVAIL;
177 static struct rtnl_link_ops dummy_link_ops __read_mostly = {
179 .setup = dummy_setup,
180 .validate = dummy_validate,
183 /* Number of dummy devices to be set up by this module. */
184 module_param(numdummies, int, 0);
185 MODULE_PARM_DESC(numdummies, "Number of dummy pseudo devices");
187 static int __init dummy_init_one(void)
189 struct net_device *dev_dummy;
192 dev_dummy = alloc_netdev(0, "dummy%d", NET_NAME_ENUM, dummy_setup);
196 dev_dummy->rtnl_link_ops = &dummy_link_ops;
197 err = register_netdevice(dev_dummy);
203 free_netdev(dev_dummy);
207 static int __init dummy_init_module(void)
211 down_write(&pernet_ops_rwsem);
213 err = __rtnl_link_register(&dummy_link_ops);
217 for (i = 0; i < numdummies && !err; i++) {
218 err = dummy_init_one();
222 __rtnl_link_unregister(&dummy_link_ops);
226 up_write(&pernet_ops_rwsem);
231 static void __exit dummy_cleanup_module(void)
233 rtnl_link_unregister(&dummy_link_ops);
236 module_init(dummy_init_module);
237 module_exit(dummy_cleanup_module);
238 MODULE_LICENSE("GPL");
239 MODULE_ALIAS_RTNL_LINK(DRV_NAME);
240 MODULE_VERSION(DRV_VERSION);