| Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 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/config.h> |
| 32 | #include <linux/module.h> |
| 33 | #include <linux/kernel.h> |
| 34 | #include <linux/netdevice.h> |
| 35 | #include <linux/etherdevice.h> |
| 36 | #include <linux/init.h> |
| 37 | #include <linux/moduleparam.h> |
| 38 | |
| 39 | static int numdummies = 1; |
| 40 | |
| 41 | static int dummy_xmit(struct sk_buff *skb, struct net_device *dev); |
| 42 | static struct net_device_stats *dummy_get_stats(struct net_device *dev); |
| 43 | |
| 44 | static 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 */ |
| 56 | static void set_multicast_list(struct net_device *dev) |
| 57 | { |
| 58 | } |
| 59 | |
| 60 | static void __init dummy_setup(struct net_device *dev) |
| 61 | { |
| 62 | /* Initialize the device structure. */ |
| 63 | dev->get_stats = dummy_get_stats; |
| 64 | dev->hard_start_xmit = dummy_xmit; |
| 65 | dev->set_multicast_list = set_multicast_list; |
| 66 | dev->set_mac_address = dummy_set_address; |
| 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 | SET_MODULE_OWNER(dev); |
| 75 | random_ether_addr(dev->dev_addr); |
| 76 | } |
| 77 | |
| 78 | static int dummy_xmit(struct sk_buff *skb, struct net_device *dev) |
| 79 | { |
| 80 | struct net_device_stats *stats = netdev_priv(dev); |
| 81 | |
| 82 | stats->tx_packets++; |
| 83 | stats->tx_bytes+=skb->len; |
| 84 | |
| 85 | dev_kfree_skb(skb); |
| 86 | return 0; |
| 87 | } |
| 88 | |
| 89 | static struct net_device_stats *dummy_get_stats(struct net_device *dev) |
| 90 | { |
| 91 | return netdev_priv(dev); |
| 92 | } |
| 93 | |
| 94 | static struct net_device **dummies; |
| 95 | |
| 96 | /* Number of dummy devices to be set up by this module. */ |
| 97 | module_param(numdummies, int, 0); |
| 98 | MODULE_PARM_DESC(numdummies, "Number of dummy pseudo devices"); |
| 99 | |
| 100 | static int __init dummy_init_one(int index) |
| 101 | { |
| 102 | struct net_device *dev_dummy; |
| 103 | int err; |
| 104 | |
| 105 | dev_dummy = alloc_netdev(sizeof(struct net_device_stats), |
| 106 | "dummy%d", dummy_setup); |
| 107 | |
| 108 | if (!dev_dummy) |
| 109 | return -ENOMEM; |
| 110 | |
| 111 | if ((err = register_netdev(dev_dummy))) { |
| 112 | free_netdev(dev_dummy); |
| 113 | dev_dummy = NULL; |
| 114 | } else { |
| 115 | dummies[index] = dev_dummy; |
| 116 | } |
| 117 | |
| 118 | return err; |
| 119 | } |
| 120 | |
| 121 | static void dummy_free_one(int index) |
| 122 | { |
| 123 | unregister_netdev(dummies[index]); |
| 124 | free_netdev(dummies[index]); |
| 125 | } |
| 126 | |
| 127 | static int __init dummy_init_module(void) |
| 128 | { |
| 129 | int i, err = 0; |
| 130 | dummies = kmalloc(numdummies * sizeof(void *), GFP_KERNEL); |
| 131 | if (!dummies) |
| 132 | return -ENOMEM; |
| 133 | for (i = 0; i < numdummies && !err; i++) |
| 134 | err = dummy_init_one(i); |
| 135 | if (err) { |
| 136 | while (--i >= 0) |
| 137 | dummy_free_one(i); |
| 138 | } |
| 139 | return err; |
| 140 | } |
| 141 | |
| 142 | static void __exit dummy_cleanup_module(void) |
| 143 | { |
| 144 | int i; |
| 145 | for (i = 0; i < numdummies; i++) |
| 146 | dummy_free_one(i); |
| 147 | kfree(dummies); |
| 148 | } |
| 149 | |
| 150 | module_init(dummy_init_module); |
| 151 | module_exit(dummy_cleanup_module); |
| 152 | MODULE_LICENSE("GPL"); |