1 // SPDX-License-Identifier: GPL-2.0-only
2 /* dummy.c: a dummy net driver
4 The purpose of this driver is to provide a device to point a
5 route through, but not to actually transmit packets.
7 Why? If you have a machine whose only connection is an occasional
8 PPP/SLIP/PLIP link, you can only connect to your own hostname
9 when the link is up. Otherwise you have to use localhost.
10 This isn't very consistent.
12 One solution is to set up a dummy link using PPP/SLIP/PLIP,
13 but this seems (to me) too much overhead for too little gain.
14 This driver provides a small alternative. Thus you can do
16 [when not running slip]
17 ifconfig dummy slip.addr.ess.here up
22 This was written by looking at Donald Becker's skeleton driver
23 and the loopback driver. I then threw away anything that didn't
24 apply! Thanks to Alan Cox for the key clue on what to do with
27 Nick Holloway, 27th May 1994
28 [I tweaked this explanation a little but that's all]
29 Alan Cox, 30th May 1994
32 #include <linux/module.h>
33 #include <linux/kernel.h>
34 #include <linux/netdevice.h>
35 #include <linux/etherdevice.h>
36 #include <linux/ethtool.h>
37 #include <linux/init.h>
38 #include <linux/moduleparam.h>
39 #include <linux/rtnetlink.h>
40 #include <linux/net_tstamp.h>
41 #include <net/rtnetlink.h>
42 #include <linux/u64_stats_sync.h>
44 #define DRV_NAME "dummy"
45 #define DRV_VERSION "1.0"
47 static int numdummies = 1;
49 /* fake multicast ability */
50 static void set_multicast_list(struct net_device *dev)
57 struct u64_stats_sync syncp;
60 static void dummy_get_stats64(struct net_device *dev,
61 struct rtnl_link_stats64 *stats)
65 for_each_possible_cpu(i) {
66 const struct pcpu_dstats *dstats;
70 dstats = per_cpu_ptr(dev->dstats, i);
72 start = u64_stats_fetch_begin_irq(&dstats->syncp);
73 tbytes = dstats->tx_bytes;
74 tpackets = dstats->tx_packets;
75 } while (u64_stats_fetch_retry_irq(&dstats->syncp, start));
76 stats->tx_bytes += tbytes;
77 stats->tx_packets += tpackets;
81 static netdev_tx_t dummy_xmit(struct sk_buff *skb, struct net_device *dev)
83 struct pcpu_dstats *dstats = this_cpu_ptr(dev->dstats);
85 u64_stats_update_begin(&dstats->syncp);
87 dstats->tx_bytes += skb->len;
88 u64_stats_update_end(&dstats->syncp);
90 skb_tx_timestamp(skb);
95 static int dummy_dev_init(struct net_device *dev)
97 dev->dstats = netdev_alloc_pcpu_stats(struct pcpu_dstats);
104 static void dummy_dev_uninit(struct net_device *dev)
106 free_percpu(dev->dstats);
109 static int dummy_change_carrier(struct net_device *dev, bool new_carrier)
112 netif_carrier_on(dev);
114 netif_carrier_off(dev);
118 static const struct net_device_ops dummy_netdev_ops = {
119 .ndo_init = dummy_dev_init,
120 .ndo_uninit = dummy_dev_uninit,
121 .ndo_start_xmit = dummy_xmit,
122 .ndo_validate_addr = eth_validate_addr,
123 .ndo_set_rx_mode = set_multicast_list,
124 .ndo_set_mac_address = eth_mac_addr,
125 .ndo_get_stats64 = dummy_get_stats64,
126 .ndo_change_carrier = dummy_change_carrier,
129 static void dummy_get_drvinfo(struct net_device *dev,
130 struct ethtool_drvinfo *info)
132 strlcpy(info->driver, DRV_NAME, sizeof(info->driver));
133 strlcpy(info->version, DRV_VERSION, sizeof(info->version));
136 static const struct ethtool_ops dummy_ethtool_ops = {
137 .get_drvinfo = dummy_get_drvinfo,
138 .get_ts_info = ethtool_op_get_ts_info,
141 static void dummy_setup(struct net_device *dev)
145 /* Initialize the device structure. */
146 dev->netdev_ops = &dummy_netdev_ops;
147 dev->ethtool_ops = &dummy_ethtool_ops;
148 dev->needs_free_netdev = true;
150 /* Fill in device structure with ethernet-generic values. */
151 dev->flags |= IFF_NOARP;
152 dev->flags &= ~IFF_MULTICAST;
153 dev->priv_flags |= IFF_LIVE_ADDR_CHANGE | IFF_NO_QUEUE;
154 dev->features |= NETIF_F_SG | NETIF_F_FRAGLIST;
155 dev->features |= NETIF_F_ALL_TSO;
156 dev->features |= NETIF_F_HW_CSUM | NETIF_F_HIGHDMA | NETIF_F_LLTX;
157 dev->features |= NETIF_F_GSO_ENCAP_ALL;
158 dev->hw_features |= dev->features;
159 dev->hw_enc_features |= dev->features;
160 eth_hw_addr_random(dev);
166 static int dummy_validate(struct nlattr *tb[], struct nlattr *data[],
167 struct netlink_ext_ack *extack)
169 if (tb[IFLA_ADDRESS]) {
170 if (nla_len(tb[IFLA_ADDRESS]) != ETH_ALEN)
172 if (!is_valid_ether_addr(nla_data(tb[IFLA_ADDRESS])))
173 return -EADDRNOTAVAIL;
178 static struct rtnl_link_ops dummy_link_ops __read_mostly = {
180 .setup = dummy_setup,
181 .validate = dummy_validate,
184 /* Number of dummy devices to be set up by this module. */
185 module_param(numdummies, int, 0);
186 MODULE_PARM_DESC(numdummies, "Number of dummy pseudo devices");
188 static int __init dummy_init_one(void)
190 struct net_device *dev_dummy;
193 dev_dummy = alloc_netdev(0, "dummy%d", NET_NAME_ENUM, dummy_setup);
197 dev_dummy->rtnl_link_ops = &dummy_link_ops;
198 err = register_netdevice(dev_dummy);
204 free_netdev(dev_dummy);
208 static int __init dummy_init_module(void)
212 down_write(&pernet_ops_rwsem);
214 err = __rtnl_link_register(&dummy_link_ops);
218 for (i = 0; i < numdummies && !err; i++) {
219 err = dummy_init_one();
223 __rtnl_link_unregister(&dummy_link_ops);
227 up_write(&pernet_ops_rwsem);
232 static void __exit dummy_cleanup_module(void)
234 rtnl_link_unregister(&dummy_link_ops);
237 module_init(dummy_init_module);
238 module_exit(dummy_cleanup_module);
239 MODULE_LICENSE("GPL");
240 MODULE_ALIAS_RTNL_LINK(DRV_NAME);
241 MODULE_VERSION(DRV_VERSION);