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1/* dummy.c: a dummy net driver
2
3 The purpose of this driver is to provide a device to point a
4 route through, but not to actually transmit packets.
5
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.
10
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
14
15 [when not running slip]
16 ifconfig dummy slip.addr.ess.here up
17 [to go to slip]
18 ifconfig dummy down
19 dip whatever
20
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
24 misguided packets.
25
26 Nick Holloway, 27th May 1994
27 [I tweaked this explanation a little but that's all]
28 Alan Cox, 30th May 1994
29*/
30
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
40static int numdummies = 1;
41
42static int dummy_xmit(struct sk_buff *skb, struct net_device *dev);
43
44static int dummy_set_address(struct net_device *dev, void *p)
45{
46 struct sockaddr *sa = p;
47
48 if (!is_valid_ether_addr(sa->sa_data))
49 return -EADDRNOTAVAIL;
50
51 memcpy(dev->dev_addr, sa->sa_data, ETH_ALEN);
52 return 0;
53}
54
55/* fake multicast ability */
56static void set_multicast_list(struct net_device *dev)
57{
58}
59
60static void dummy_setup(struct net_device *dev)
61{
62 /* Initialize the device structure. */
63 dev->hard_start_xmit = dummy_xmit;
64 dev->set_multicast_list = set_multicast_list;
65 dev->set_mac_address = dummy_set_address;
66 dev->destructor = free_netdev;
67
68 /* Fill in device structure with ethernet-generic values. */
69 ether_setup(dev);
70 dev->tx_queue_len = 0;
71 dev->change_mtu = NULL;
72 dev->flags |= IFF_NOARP;
73 dev->flags &= ~IFF_MULTICAST;
74 random_ether_addr(dev->dev_addr);
75}
76
77static int dummy_xmit(struct sk_buff *skb, struct net_device *dev)
78{
79 dev->stats.tx_packets++;
80 dev->stats.tx_bytes += skb->len;
81
82 dev_kfree_skb(skb);
83 return 0;
84}
85
86static int dummy_validate(struct nlattr *tb[], struct nlattr *data[])
87{
88 if (tb[IFLA_ADDRESS]) {
89 if (nla_len(tb[IFLA_ADDRESS]) != ETH_ALEN)
90 return -EINVAL;
91 if (!is_valid_ether_addr(nla_data(tb[IFLA_ADDRESS])))
92 return -EADDRNOTAVAIL;
93 }
94 return 0;
95}
96
97static struct rtnl_link_ops dummy_link_ops __read_mostly = {
98 .kind = "dummy",
99 .setup = dummy_setup,
100 .validate = dummy_validate,
101};
102
103/* Number of dummy devices to be set up by this module. */
104module_param(numdummies, int, 0);
105MODULE_PARM_DESC(numdummies, "Number of dummy pseudo devices");
106
107static int __init dummy_init_one(void)
108{
109 struct net_device *dev_dummy;
110 int err;
111
112 dev_dummy = alloc_netdev(0, "dummy%d", dummy_setup);
113 if (!dev_dummy)
114 return -ENOMEM;
115
116 err = dev_alloc_name(dev_dummy, dev_dummy->name);
117 if (err < 0)
118 goto err;
119
120 dev_dummy->rtnl_link_ops = &dummy_link_ops;
121 err = register_netdevice(dev_dummy);
122 if (err < 0)
123 goto err;
124 return 0;
125
126err:
127 free_netdev(dev_dummy);
128 return err;
129}
130
131static int __init dummy_init_module(void)
132{
133 int i, err = 0;
134
135 rtnl_lock();
136 err = __rtnl_link_register(&dummy_link_ops);
137
138 for (i = 0; i < numdummies && !err; i++)
139 err = dummy_init_one();
140 if (err < 0)
141 __rtnl_link_unregister(&dummy_link_ops);
142 rtnl_unlock();
143
144 return err;
145}
146
147static void __exit dummy_cleanup_module(void)
148{
149 rtnl_link_unregister(&dummy_link_ops);
150}
151
152module_init(dummy_init_module);
153module_exit(dummy_cleanup_module);
154MODULE_LICENSE("GPL");
155MODULE_ALIAS_RTNL_LINK("dummy");