| /* dummy.c: a dummy net driver |
| |
| The purpose of this driver is to provide a device to point a |
| route through, but not to actually transmit packets. |
| |
| Why? If you have a machine whose only connection is an occasional |
| PPP/SLIP/PLIP link, you can only connect to your own hostname |
| when the link is up. Otherwise you have to use localhost. |
| This isn't very consistent. |
| |
| One solution is to set up a dummy link using PPP/SLIP/PLIP, |
| but this seems (to me) too much overhead for too little gain. |
| This driver provides a small alternative. Thus you can do |
| |
| [when not running slip] |
| ifconfig dummy slip.addr.ess.here up |
| [to go to slip] |
| ifconfig dummy down |
| dip whatever |
| |
| This was written by looking at Donald Becker's skeleton driver |
| and the loopback driver. I then threw away anything that didn't |
| apply! Thanks to Alan Cox for the key clue on what to do with |
| misguided packets. |
| |
| Nick Holloway, 27th May 1994 |
| [I tweaked this explanation a little but that's all] |
| Alan Cox, 30th May 1994 |
| */ |
| |
| #include <linux/module.h> |
| #include <linux/kernel.h> |
| #include <linux/netdevice.h> |
| #include <linux/etherdevice.h> |
| #include <linux/init.h> |
| #include <linux/moduleparam.h> |
| #include <linux/rtnetlink.h> |
| #include <net/rtnetlink.h> |
| #include <linux/u64_stats_sync.h> |
| |
| static int numdummies = 1; |
| |
| /* fake multicast ability */ |
| static void set_multicast_list(struct net_device *dev) |
| { |
| } |
| |
| struct pcpu_dstats { |
| u64 tx_packets; |
| u64 tx_bytes; |
| struct u64_stats_sync syncp; |
| }; |
| |
| static struct rtnl_link_stats64 *dummy_get_stats64(struct net_device *dev, |
| struct rtnl_link_stats64 *stats) |
| { |
| int i; |
| |
| for_each_possible_cpu(i) { |
| const struct pcpu_dstats *dstats; |
| u64 tbytes, tpackets; |
| unsigned int start; |
| |
| dstats = per_cpu_ptr(dev->dstats, i); |
| do { |
| start = u64_stats_fetch_begin(&dstats->syncp); |
| tbytes = dstats->tx_bytes; |
| tpackets = dstats->tx_packets; |
| } while (u64_stats_fetch_retry(&dstats->syncp, start)); |
| stats->tx_bytes += tbytes; |
| stats->tx_packets += tpackets; |
| } |
| return stats; |
| } |
| |
| static netdev_tx_t dummy_xmit(struct sk_buff *skb, struct net_device *dev) |
| { |
| struct pcpu_dstats *dstats = this_cpu_ptr(dev->dstats); |
| |
| u64_stats_update_begin(&dstats->syncp); |
| dstats->tx_packets++; |
| dstats->tx_bytes += skb->len; |
| u64_stats_update_end(&dstats->syncp); |
| |
| dev_kfree_skb(skb); |
| return NETDEV_TX_OK; |
| } |
| |
| static int dummy_dev_init(struct net_device *dev) |
| { |
| dev->dstats = alloc_percpu(struct pcpu_dstats); |
| if (!dev->dstats) |
| return -ENOMEM; |
| |
| return 0; |
| } |
| |
| static void dummy_dev_uninit(struct net_device *dev) |
| { |
| free_percpu(dev->dstats); |
| } |
| |
| static const struct net_device_ops dummy_netdev_ops = { |
| .ndo_init = dummy_dev_init, |
| .ndo_uninit = dummy_dev_uninit, |
| .ndo_start_xmit = dummy_xmit, |
| .ndo_validate_addr = eth_validate_addr, |
| .ndo_set_rx_mode = set_multicast_list, |
| .ndo_set_mac_address = eth_mac_addr, |
| .ndo_get_stats64 = dummy_get_stats64, |
| }; |
| |
| static void dummy_setup(struct net_device *dev) |
| { |
| ether_setup(dev); |
| |
| /* Initialize the device structure. */ |
| dev->netdev_ops = &dummy_netdev_ops; |
| dev->destructor = free_netdev; |
| |
| /* Fill in device structure with ethernet-generic values. */ |
| dev->tx_queue_len = 0; |
| dev->flags |= IFF_NOARP; |
| dev->flags &= ~IFF_MULTICAST; |
| dev->priv_flags |= IFF_LIVE_ADDR_CHANGE; |
| dev->features |= NETIF_F_SG | NETIF_F_FRAGLIST | NETIF_F_TSO; |
| dev->features |= NETIF_F_HW_CSUM | NETIF_F_HIGHDMA | NETIF_F_LLTX; |
| eth_hw_addr_random(dev); |
| } |
| |
| static int dummy_validate(struct nlattr *tb[], struct nlattr *data[]) |
| { |
| if (tb[IFLA_ADDRESS]) { |
| if (nla_len(tb[IFLA_ADDRESS]) != ETH_ALEN) |
| return -EINVAL; |
| if (!is_valid_ether_addr(nla_data(tb[IFLA_ADDRESS]))) |
| return -EADDRNOTAVAIL; |
| } |
| return 0; |
| } |
| |
| static struct rtnl_link_ops dummy_link_ops __read_mostly = { |
| .kind = "dummy", |
| .setup = dummy_setup, |
| .validate = dummy_validate, |
| }; |
| |
| /* Number of dummy devices to be set up by this module. */ |
| module_param(numdummies, int, 0); |
| MODULE_PARM_DESC(numdummies, "Number of dummy pseudo devices"); |
| |
| static int __init dummy_init_one(void) |
| { |
| struct net_device *dev_dummy; |
| int err; |
| |
| dev_dummy = alloc_netdev(0, "dummy%d", dummy_setup); |
| if (!dev_dummy) |
| return -ENOMEM; |
| |
| dev_dummy->rtnl_link_ops = &dummy_link_ops; |
| err = register_netdevice(dev_dummy); |
| if (err < 0) |
| goto err; |
| return 0; |
| |
| err: |
| free_netdev(dev_dummy); |
| return err; |
| } |
| |
| static int __init dummy_init_module(void) |
| { |
| int i, err = 0; |
| |
| rtnl_lock(); |
| err = __rtnl_link_register(&dummy_link_ops); |
| |
| for (i = 0; i < numdummies && !err; i++) { |
| err = dummy_init_one(); |
| cond_resched(); |
| } |
| if (err < 0) |
| __rtnl_link_unregister(&dummy_link_ops); |
| rtnl_unlock(); |
| |
| return err; |
| } |
| |
| static void __exit dummy_cleanup_module(void) |
| { |
| rtnl_link_unregister(&dummy_link_ops); |
| } |
| |
| module_init(dummy_init_module); |
| module_exit(dummy_cleanup_module); |
| MODULE_LICENSE("GPL"); |
| MODULE_ALIAS_RTNL_LINK("dummy"); |