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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 | |
| 40 | static int numdummies = 1; |
| 41 | |
| 42 | static int dummy_xmit(struct sk_buff *skb, 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 const struct net_device_ops dummy_netdev_ops = { |
| 61 | .ndo_start_xmit = dummy_xmit, |
| 62 | .ndo_validate_addr = eth_validate_addr, |
| 63 | .ndo_set_multicast_list = set_multicast_list, |
| 64 | .ndo_set_mac_address = dummy_set_address, |
| 65 | }; |
| 66 | |
| 67 | static void dummy_setup(struct net_device *dev) |
| 68 | { |
| 69 | ether_setup(dev); |
| 70 | |
| 71 | /* Initialize the device structure. */ |
| 72 | dev->netdev_ops = &dummy_netdev_ops; |
| 73 | dev->destructor = free_netdev; |
| 74 | |
| 75 | /* Fill in device structure with ethernet-generic values. */ |
| 76 | dev->tx_queue_len = 0; |
| 77 | dev->flags |= IFF_NOARP; |
| 78 | dev->flags &= ~IFF_MULTICAST; |
| 79 | random_ether_addr(dev->dev_addr); |
| 80 | } |
| 81 | |
| 82 | static int dummy_xmit(struct sk_buff *skb, struct net_device *dev) |
| 83 | { |
| 84 | dev->stats.tx_packets++; |
| 85 | dev->stats.tx_bytes += skb->len; |
| 86 | |
| 87 | dev_kfree_skb(skb); |
| 88 | return 0; |
| 89 | } |
| 90 | |
| 91 | static int dummy_validate(struct nlattr *tb[], struct nlattr *data[]) |
| 92 | { |
| 93 | if (tb[IFLA_ADDRESS]) { |
| 94 | if (nla_len(tb[IFLA_ADDRESS]) != ETH_ALEN) |
| 95 | return -EINVAL; |
| 96 | if (!is_valid_ether_addr(nla_data(tb[IFLA_ADDRESS]))) |
| 97 | return -EADDRNOTAVAIL; |
| 98 | } |
| 99 | return 0; |
| 100 | } |
| 101 | |
| 102 | static struct rtnl_link_ops dummy_link_ops __read_mostly = { |
| 103 | .kind = "dummy", |
| 104 | .setup = dummy_setup, |
| 105 | .validate = dummy_validate, |
| 106 | }; |
| 107 | |
| 108 | /* Number of dummy devices to be set up by this module. */ |
| 109 | module_param(numdummies, int, 0); |
| 110 | MODULE_PARM_DESC(numdummies, "Number of dummy pseudo devices"); |
| 111 | |
| 112 | static int __init dummy_init_one(void) |
| 113 | { |
| 114 | struct net_device *dev_dummy; |
| 115 | int err; |
| 116 | |
| 117 | dev_dummy = alloc_netdev(0, "dummy%d", dummy_setup); |
| 118 | if (!dev_dummy) |
| 119 | return -ENOMEM; |
| 120 | |
| 121 | err = dev_alloc_name(dev_dummy, dev_dummy->name); |
| 122 | if (err < 0) |
| 123 | goto err; |
| 124 | |
| 125 | dev_dummy->rtnl_link_ops = &dummy_link_ops; |
| 126 | err = register_netdevice(dev_dummy); |
| 127 | if (err < 0) |
| 128 | goto err; |
| 129 | return 0; |
| 130 | |
| 131 | err: |
| 132 | free_netdev(dev_dummy); |
| 133 | return err; |
| 134 | } |
| 135 | |
| 136 | static int __init dummy_init_module(void) |
| 137 | { |
| 138 | int i, err = 0; |
| 139 | |
| 140 | rtnl_lock(); |
| 141 | err = __rtnl_link_register(&dummy_link_ops); |
| 142 | |
| 143 | for (i = 0; i < numdummies && !err; i++) |
| 144 | err = dummy_init_one(); |
| 145 | if (err < 0) |
| 146 | __rtnl_link_unregister(&dummy_link_ops); |
| 147 | rtnl_unlock(); |
| 148 | |
| 149 | return err; |
| 150 | } |
| 151 | |
| 152 | static void __exit dummy_cleanup_module(void) |
| 153 | { |
| 154 | rtnl_link_unregister(&dummy_link_ops); |
| 155 | } |
| 156 | |
| 157 | module_init(dummy_init_module); |
| 158 | module_exit(dummy_cleanup_module); |
| 159 | MODULE_LICENSE("GPL"); |
| 160 | MODULE_ALIAS_RTNL_LINK("dummy"); |
| 161 |
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Tags:
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v2.6.34-rc5
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