159 lines
3.7 KiB
C
159 lines
3.7 KiB
C
/* dummy.c: a dummy net driver
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The purpose of this driver is to provide a device to point a
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route through, but not to actually transmit packets.
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Why? If you have a machine whose only connection is an occasional
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PPP/SLIP/PLIP link, you can only connect to your own hostname
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when the link is up. Otherwise you have to use localhost.
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This isn't very consistent.
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One solution is to set up a dummy link using PPP/SLIP/PLIP,
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but this seems (to me) too much overhead for too little gain.
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This driver provides a small alternative. Thus you can do
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[when not running slip]
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ifconfig dummy slip.addr.ess.here up
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[to go to slip]
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ifconfig dummy down
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dip whatever
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This was written by looking at Donald Becker's skeleton driver
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and the loopback driver. I then threw away anything that didn't
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apply! Thanks to Alan Cox for the key clue on what to do with
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misguided packets.
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Nick Holloway, 27th May 1994
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[I tweaked this explanation a little but that's all]
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Alan Cox, 30th May 1994
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*/
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#include <linux/module.h>
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#include <linux/kernel.h>
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#include <linux/netdevice.h>
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#include <linux/etherdevice.h>
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#include <linux/init.h>
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#include <linux/moduleparam.h>
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#include <linux/rtnetlink.h>
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#include <net/rtnetlink.h>
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static int numdummies = 1;
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static int dummy_set_address(struct net_device *dev, void *p)
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{
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struct sockaddr *sa = p;
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if (!is_valid_ether_addr(sa->sa_data))
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return -EADDRNOTAVAIL;
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memcpy(dev->dev_addr, sa->sa_data, ETH_ALEN);
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return 0;
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}
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/* fake multicast ability */
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static void set_multicast_list(struct net_device *dev)
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{
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}
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static netdev_tx_t dummy_xmit(struct sk_buff *skb, struct net_device *dev)
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{
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dev->stats.tx_packets++;
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dev->stats.tx_bytes += skb->len;
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dev_kfree_skb(skb);
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return NETDEV_TX_OK;
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}
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static const struct net_device_ops dummy_netdev_ops = {
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.ndo_start_xmit = dummy_xmit,
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.ndo_validate_addr = eth_validate_addr,
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.ndo_set_multicast_list = set_multicast_list,
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.ndo_set_mac_address = dummy_set_address,
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};
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static void dummy_setup(struct net_device *dev)
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{
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ether_setup(dev);
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/* Initialize the device structure. */
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dev->netdev_ops = &dummy_netdev_ops;
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dev->destructor = free_netdev;
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/* Fill in device structure with ethernet-generic values. */
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dev->tx_queue_len = 0;
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dev->flags |= IFF_NOARP;
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dev->flags &= ~IFF_MULTICAST;
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random_ether_addr(dev->dev_addr);
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}
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static int dummy_validate(struct nlattr *tb[], struct nlattr *data[])
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{
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if (tb[IFLA_ADDRESS]) {
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if (nla_len(tb[IFLA_ADDRESS]) != ETH_ALEN)
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return -EINVAL;
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if (!is_valid_ether_addr(nla_data(tb[IFLA_ADDRESS])))
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return -EADDRNOTAVAIL;
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}
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return 0;
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}
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static struct rtnl_link_ops dummy_link_ops __read_mostly = {
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.kind = "dummy",
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.setup = dummy_setup,
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.validate = dummy_validate,
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};
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/* Number of dummy devices to be set up by this module. */
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module_param(numdummies, int, 0);
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MODULE_PARM_DESC(numdummies, "Number of dummy pseudo devices");
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static int __init dummy_init_one(void)
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{
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struct net_device *dev_dummy;
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int err;
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dev_dummy = alloc_netdev(0, "dummy%d", dummy_setup);
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if (!dev_dummy)
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return -ENOMEM;
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err = dev_alloc_name(dev_dummy, dev_dummy->name);
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if (err < 0)
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goto err;
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dev_dummy->rtnl_link_ops = &dummy_link_ops;
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err = register_netdevice(dev_dummy);
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if (err < 0)
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goto err;
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return 0;
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err:
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free_netdev(dev_dummy);
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return err;
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}
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static int __init dummy_init_module(void)
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{
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int i, err = 0;
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rtnl_lock();
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err = __rtnl_link_register(&dummy_link_ops);
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for (i = 0; i < numdummies && !err; i++)
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err = dummy_init_one();
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if (err < 0)
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__rtnl_link_unregister(&dummy_link_ops);
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rtnl_unlock();
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return err;
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}
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static void __exit dummy_cleanup_module(void)
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{
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rtnl_link_unregister(&dummy_link_ops);
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}
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module_init(dummy_init_module);
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module_exit(dummy_cleanup_module);
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MODULE_LICENSE("GPL");
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MODULE_ALIAS_RTNL_LINK("dummy");
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