drivers/net/dummy.c

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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 /* To have statistics (just packets sent) define this */
 32
 33 #include <linux/config.h>
 34 #include <linux/module.h>
 35 #include <linux/kernel.h>
 36 #include <linux/netdevice.h>
 37 #include <linux/init.h>
 38
 39 static intdummy_xmit(struct sk_buff *skb,struct net_device *dev);
 40 static struct net_device_stats *dummy_get_stats(struct net_device *dev);
 41
 42 /* fake multicast ability */
 43 static voidset_multicast_list(struct net_device *dev)
 44 {
 45 }
 46
 47 #ifdef CONFIG_NET_FASTROUTE
 48 static intdummy_accept_fastpath(struct net_device *dev,struct dst_entry *dst)
 49 {
 50 return-1;
 51 }
 52 #endif
 53
 54 static int __init dummy_init(struct net_device *dev)
 55 {
 56 /* Initialize the device structure. */
 57  dev->hard_start_xmit = dummy_xmit;
 58
 59  dev->priv =kmalloc(sizeof(struct net_device_stats), GFP_KERNEL);
 60 if(dev->priv == NULL)
 61 return-ENOMEM;
 62 memset(dev->priv,0,sizeof(struct net_device_stats));
 63  dev->get_stats = dummy_get_stats;
 64
 65  dev->set_multicast_list = set_multicast_list;
 66
 67 /* Fill in the fields of the device structure with ethernet-generic values. */
 68 ether_setup(dev);
 69  dev->tx_queue_len =0;
 70  dev->flags |= IFF_NOARP;
 71  dev->flags &= ~IFF_MULTICAST;
 72 #ifdef CONFIG_NET_FASTROUTE
 73  dev->accept_fastpath = dummy_accept_fastpath;
 74 #endif
 75
 76 return0;
 77 }
 78
 79 static intdummy_xmit(struct sk_buff *skb,struct net_device *dev)
 80 {
 81 struct net_device_stats *stats;
 82
 83  stats = (struct net_device_stats *)dev->priv;
 84  stats->tx_packets++;
 85  stats->tx_bytes+=skb->len;
 86
 87 dev_kfree_skb(skb);
 88 return0;
 89 }
 90
 91 static struct net_device_stats *dummy_get_stats(struct net_device *dev)
 92 {
 93 return dev->priv;
 94 }
 95
 96 static struct net_device dev_dummy;
 97
 98 static int __init dummy_init_module(void)
 99 {
 100 int err;
 101
 102  dev_dummy.init = dummy_init;
 103 SET_MODULE_OWNER(&dev_dummy);
 104
 105 /* Find a name for this unit */
 106  err=dev_alloc_name(&dev_dummy,"dummy%d");
 107 if(err<0)
 108 return err;
 109 if(register_netdev(&dev_dummy) !=0)
 110 return-EIO;
 111 return0;
 112 }
 113
 114 static void __exit dummy_cleanup_module(void)
 115 {
 116 unregister_netdev(&dev_dummy);
 117 kfree(dev_dummy.priv);
 118
 119 memset(&dev_dummy,0,sizeof(dev_dummy));
 120  dev_dummy.init = dummy_init;
 121 }
 122
 123 module_init(dummy_init_module);
 124 module_exit(dummy_cleanup_module);