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>
41 struct net_device *dev;
42 struct list_head list;
45 static int numdummies = 1;
47 static int dummy_xmit(struct sk_buff *skb, struct net_device *dev);
49 static int dummy_set_address(struct net_device *dev, void *p)
51 struct sockaddr *sa = p;
53 if (!is_valid_ether_addr(sa->sa_data))
54 return -EADDRNOTAVAIL;
56 memcpy(dev->dev_addr, sa->sa_data, ETH_ALEN);
60 /* fake multicast ability */
61 static void set_multicast_list(struct net_device *dev)
65 static void dummy_setup(struct net_device *dev)
67 /* Initialize the device structure. */
68 dev->hard_start_xmit = dummy_xmit;
69 dev->set_multicast_list = set_multicast_list;
70 dev->set_mac_address = dummy_set_address;
71 dev->destructor = free_netdev;
73 /* Fill in device structure with ethernet-generic values. */
75 dev->tx_queue_len = 0;
76 dev->change_mtu = NULL;
77 dev->flags |= IFF_NOARP;
78 dev->flags &= ~IFF_MULTICAST;
79 SET_MODULE_OWNER(dev);
80 random_ether_addr(dev->dev_addr);
83 static int dummy_xmit(struct sk_buff *skb, struct net_device *dev)
85 dev->stats.tx_packets++;
86 dev->stats.tx_bytes += skb->len;
92 static LIST_HEAD(dummies);
94 static int dummy_newlink(struct net_device *dev,
95 struct nlattr *tb[], struct nlattr *data[])
97 struct dummy_priv *priv = netdev_priv(dev);
100 err = register_netdevice(dev);
105 list_add_tail(&priv->list, &dummies);
109 static void dummy_dellink(struct net_device *dev)
111 struct dummy_priv *priv = netdev_priv(dev);
113 list_del(&priv->list);
114 unregister_netdevice(dev);
117 static struct rtnl_link_ops dummy_link_ops __read_mostly = {
119 .priv_size = sizeof(struct dummy_priv),
120 .setup = dummy_setup,
121 .newlink = dummy_newlink,
122 .dellink = dummy_dellink,
125 /* Number of dummy devices to be set up by this module. */
126 module_param(numdummies, int, 0);
127 MODULE_PARM_DESC(numdummies, "Number of dummy pseudo devices");
129 static int __init dummy_init_one(void)
131 struct net_device *dev_dummy;
132 struct dummy_priv *priv;
135 dev_dummy = alloc_netdev(sizeof(struct dummy_priv), "dummy%d",
141 err = dev_alloc_name(dev_dummy, dev_dummy->name);
145 dev_dummy->rtnl_link_ops = &dummy_link_ops;
146 err = register_netdevice(dev_dummy);
150 priv = netdev_priv(dev_dummy);
151 priv->dev = dev_dummy;
152 list_add_tail(&priv->list, &dummies);
156 free_netdev(dev_dummy);
160 static int __init dummy_init_module(void)
162 struct dummy_priv *priv, *next;
166 err = __rtnl_link_register(&dummy_link_ops);
168 for (i = 0; i < numdummies && !err; i++)
169 err = dummy_init_one();
171 list_for_each_entry_safe(priv, next, &dummies, list)
172 dummy_dellink(priv->dev);
173 __rtnl_link_unregister(&dummy_link_ops);
180 static void __exit dummy_cleanup_module(void)
182 struct dummy_priv *priv, *next;
185 list_for_each_entry_safe(priv, next, &dummies, list)
186 dummy_dellink(priv->dev);
188 __rtnl_link_unregister(&dummy_link_ops);
192 module_init(dummy_init_module);
193 module_exit(dummy_cleanup_module);
194 MODULE_LICENSE("GPL");
195 MODULE_ALIAS_RTNL_LINK("dummy");