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>
38 static int numdummies = 1;
40 static int dummy_xmit(struct sk_buff *skb, struct net_device *dev);
42 static int dummy_set_address(struct net_device *dev, void *p)
44 struct sockaddr *sa = p;
46 if (!is_valid_ether_addr(sa->sa_data))
47 return -EADDRNOTAVAIL;
49 memcpy(dev->dev_addr, sa->sa_data, ETH_ALEN);
53 /* fake multicast ability */
54 static void set_multicast_list(struct net_device *dev)
58 static void __init dummy_setup(struct net_device *dev)
60 /* Initialize the device structure. */
61 dev->hard_start_xmit = dummy_xmit;
62 dev->set_multicast_list = set_multicast_list;
63 dev->set_mac_address = dummy_set_address;
65 /* Fill in device structure with ethernet-generic values. */
67 dev->tx_queue_len = 0;
68 dev->change_mtu = NULL;
69 dev->flags |= IFF_NOARP;
70 dev->flags &= ~IFF_MULTICAST;
71 SET_MODULE_OWNER(dev);
72 random_ether_addr(dev->dev_addr);
75 static int dummy_xmit(struct sk_buff *skb, struct net_device *dev)
77 dev->stats.tx_packets++;
78 dev->stats.tx_bytes += skb->len;
84 static struct net_device **dummies;
86 /* Number of dummy devices to be set up by this module. */
87 module_param(numdummies, int, 0);
88 MODULE_PARM_DESC(numdummies, "Number of dummy pseudo devices");
90 static int __init dummy_init_one(int index)
92 struct net_device *dev_dummy;
95 dev_dummy = alloc_netdev(0, "dummy%d", dummy_setup);
100 if ((err = register_netdev(dev_dummy))) {
101 free_netdev(dev_dummy);
104 dummies[index] = dev_dummy;
110 static void dummy_free_one(int index)
112 unregister_netdev(dummies[index]);
113 free_netdev(dummies[index]);
116 static int __init dummy_init_module(void)
119 dummies = kmalloc(numdummies * sizeof(void *), GFP_KERNEL);
122 for (i = 0; i < numdummies && !err; i++)
123 err = dummy_init_one(i);
132 static void __exit dummy_cleanup_module(void)
135 for (i = 0; i < numdummies; i++)
140 module_init(dummy_init_module);
141 module_exit(dummy_cleanup_module);
142 MODULE_LICENSE("GPL");