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>
40 static int numdummies = 1;
42 static int dummy_xmit(struct sk_buff *skb, struct net_device *dev);
44 static int dummy_set_address(struct net_device *dev, void *p)
46 struct sockaddr *sa = p;
48 if (!is_valid_ether_addr(sa->sa_data))
49 return -EADDRNOTAVAIL;
51 memcpy(dev->dev_addr, sa->sa_data, ETH_ALEN);
55 /* fake multicast ability */
56 static void set_multicast_list(struct net_device *dev)
60 static const struct net_device_ops dummy_netdev_ops = {
61 .ndo_start_xmit = dummy_xmit,
62 .ndo_validate_addr = eth_validate_addr,
63 .ndo_set_multicast_list = set_multicast_list,
64 .ndo_set_mac_address = dummy_set_address,
67 static void dummy_setup(struct net_device *dev)
71 /* Initialize the device structure. */
72 dev->netdev_ops = &dummy_netdev_ops;
73 dev->destructor = free_netdev;
75 /* Fill in device structure with ethernet-generic values. */
76 dev->tx_queue_len = 0;
77 dev->flags |= IFF_NOARP;
78 dev->flags &= ~IFF_MULTICAST;
79 random_ether_addr(dev->dev_addr);
82 static int dummy_xmit(struct sk_buff *skb, struct net_device *dev)
84 dev->stats.tx_packets++;
85 dev->stats.tx_bytes += skb->len;
91 static int dummy_validate(struct nlattr *tb[], struct nlattr *data[])
93 if (tb[IFLA_ADDRESS]) {
94 if (nla_len(tb[IFLA_ADDRESS]) != ETH_ALEN)
96 if (!is_valid_ether_addr(nla_data(tb[IFLA_ADDRESS])))
97 return -EADDRNOTAVAIL;
102 static struct rtnl_link_ops dummy_link_ops __read_mostly = {
104 .setup = dummy_setup,
105 .validate = dummy_validate,
108 /* Number of dummy devices to be set up by this module. */
109 module_param(numdummies, int, 0);
110 MODULE_PARM_DESC(numdummies, "Number of dummy pseudo devices");
112 static int __init dummy_init_one(void)
114 struct net_device *dev_dummy;
117 dev_dummy = alloc_netdev(0, "dummy%d", dummy_setup);
121 err = dev_alloc_name(dev_dummy, dev_dummy->name);
125 dev_dummy->rtnl_link_ops = &dummy_link_ops;
126 err = register_netdevice(dev_dummy);
132 free_netdev(dev_dummy);
136 static int __init dummy_init_module(void)
141 err = __rtnl_link_register(&dummy_link_ops);
143 for (i = 0; i < numdummies && !err; i++)
144 err = dummy_init_one();
146 __rtnl_link_unregister(&dummy_link_ops);
152 static void __exit dummy_cleanup_module(void)
154 rtnl_link_unregister(&dummy_link_ops);
157 module_init(dummy_init_module);
158 module_exit(dummy_cleanup_module);
159 MODULE_LICENSE("GPL");
160 MODULE_ALIAS_RTNL_LINK("dummy");