drivers/net/dummy.c

   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 <linux/net_tstamp.h>
  39 #include <net/rtnetlink.h>
  40 #include <linux/u64_stats_sync.h>
  41
  42 #define DRV_NAME        "dummy"
  43 #define DRV_VERSION     "1.0"
  44
  45 static int numdummies = 1;
  46
  47 /* fake multicast ability */
  48 static void set_multicast_list(struct net_device *dev)
  49 {
  50 }
  51
  52 struct pcpu_dstats {
  53         u64                     tx_packets;
  54         u64                     tx_bytes;
  55         struct u64_stats_sync   syncp;
  56 };
  57
  58 static void dummy_get_stats64(struct net_device *dev,
  59                               struct rtnl_link_stats64 *stats)
  60 {
  61         int i;
  62
  63         for_each_possible_cpu(i) {
  64                 const struct pcpu_dstats *dstats;
  65                 u64 tbytes, tpackets;
  66                 unsigned int start;
  67
  68                 dstats = per_cpu_ptr(dev->dstats, i);
  69                 do {
  70                         start = u64_stats_fetch_begin_irq(&dstats->syncp);
  71                         tbytes = dstats->tx_bytes;
  72                         tpackets = dstats->tx_packets;
  73                 } while (u64_stats_fetch_retry_irq(&dstats->syncp, start));
  74                 stats->tx_bytes += tbytes;
  75                 stats->tx_packets += tpackets;
  76         }
  77 }
  78
  79 static netdev_tx_t dummy_xmit(struct sk_buff *skb, struct net_device *dev)
  80 {
  81         struct pcpu_dstats *dstats = this_cpu_ptr(dev->dstats);
  82
  83         u64_stats_update_begin(&dstats->syncp);
  84         dstats->tx_packets++;
  85         dstats->tx_bytes += skb->len;
  86         u64_stats_update_end(&dstats->syncp);
  87
  88         skb_tx_timestamp(skb);
  89         dev_kfree_skb(skb);
  90         return NETDEV_TX_OK;
  91 }
  92
  93 static int dummy_dev_init(struct net_device *dev)
  94 {
  95         dev->dstats = netdev_alloc_pcpu_stats(struct pcpu_dstats);
  96         if (!dev->dstats)
  97                 return -ENOMEM;
  98
  99         return 0;
 100 }
 101
 102 static void dummy_dev_uninit(struct net_device *dev)
 103 {
 104         free_percpu(dev->dstats);
 105 }
 106
 107 static int dummy_change_carrier(struct net_device *dev, bool new_carrier)
 108 {
 109         if (new_carrier)
 110                 netif_carrier_on(dev);
 111         else
 112                 netif_carrier_off(dev);
 113         return 0;
 114 }
 115
 116 static const struct net_device_ops dummy_netdev_ops = {
 117         .ndo_init               = dummy_dev_init,
 118         .ndo_uninit             = dummy_dev_uninit,
 119         .ndo_start_xmit         = dummy_xmit,
 120         .ndo_validate_addr      = eth_validate_addr,
 121         .ndo_set_rx_mode        = set_multicast_list,
 122         .ndo_set_mac_address    = eth_mac_addr,
 123         .ndo_get_stats64        = dummy_get_stats64,
 124         .ndo_change_carrier     = dummy_change_carrier,
 125 };
 126
 127 static void dummy_get_drvinfo(struct net_device *dev,
 128                               struct ethtool_drvinfo *info)
 129 {
 130         strlcpy(info->driver, DRV_NAME, sizeof(info->driver));
 131         strlcpy(info->version, DRV_VERSION, sizeof(info->version));
 132 }
 133
 134 static int dummy_get_ts_info(struct net_device *dev,
 135                               struct ethtool_ts_info *ts_info)
 136 {
 137         ts_info->so_timestamping = SOF_TIMESTAMPING_TX_SOFTWARE |
 138                                    SOF_TIMESTAMPING_RX_SOFTWARE |
 139                                    SOF_TIMESTAMPING_SOFTWARE;
 140
 141         ts_info->phc_index = -1;
 142
 143         return 0;
 144 };
 145
 146 static const struct ethtool_ops dummy_ethtool_ops = {
 147         .get_drvinfo            = dummy_get_drvinfo,
 148         .get_ts_info            = dummy_get_ts_info,
 149 };
 150
 151 static void dummy_setup(struct net_device *dev)
 152 {
 153         ether_setup(dev);
 154
 155         /* Initialize the device structure. */
 156         dev->netdev_ops = &dummy_netdev_ops;
 157         dev->ethtool_ops = &dummy_ethtool_ops;
 158         dev->needs_free_netdev = true;
 159
 160         /* Fill in device structure with ethernet-generic values. */
 161         dev->flags |= IFF_NOARP;
 162         dev->flags &= ~IFF_MULTICAST;
 163         dev->priv_flags |= IFF_LIVE_ADDR_CHANGE | IFF_NO_QUEUE;
 164         dev->features   |= NETIF_F_SG | NETIF_F_FRAGLIST;
 165         dev->features   |= NETIF_F_ALL_TSO;
 166         dev->features   |= NETIF_F_HW_CSUM | NETIF_F_HIGHDMA | NETIF_F_LLTX;
 167         dev->features   |= NETIF_F_GSO_ENCAP_ALL;
 168         dev->hw_features |= dev->features;
 169         dev->hw_enc_features |= dev->features;
 170         eth_hw_addr_random(dev);
 171
 172         dev->min_mtu = 0;
 173         dev->max_mtu = 0;
 174 }
 175
 176 static int dummy_validate(struct nlattr *tb[], struct nlattr *data[],
 177                           struct netlink_ext_ack *extack)
 178 {
 179         if (tb[IFLA_ADDRESS]) {
 180                 if (nla_len(tb[IFLA_ADDRESS]) != ETH_ALEN)
 181                         return -EINVAL;
 182                 if (!is_valid_ether_addr(nla_data(tb[IFLA_ADDRESS])))
 183                         return -EADDRNOTAVAIL;
 184         }
 185         return 0;
 186 }
 187
 188 static struct rtnl_link_ops dummy_link_ops __read_mostly = {
 189         .kind           = DRV_NAME,
 190         .setup          = dummy_setup,
 191         .validate       = dummy_validate,
 192 };
 193
 194 /* Number of dummy devices to be set up by this module. */
 195 module_param(numdummies, int, 0);
 196 MODULE_PARM_DESC(numdummies, "Number of dummy pseudo devices");
 197
 198 static int __init dummy_init_one(void)
 199 {
 200         struct net_device *dev_dummy;
 201         int err;
 202
 203         dev_dummy = alloc_netdev(0, "dummy%d", NET_NAME_ENUM, dummy_setup);
 204         if (!dev_dummy)
 205                 return -ENOMEM;
 206
 207         dev_dummy->rtnl_link_ops = &dummy_link_ops;
 208         err = register_netdevice(dev_dummy);
 209         if (err < 0)
 210                 goto err;
 211         return 0;
 212
 213 err:
 214         free_netdev(dev_dummy);
 215         return err;
 216 }
 217
 218 static int __init dummy_init_module(void)
 219 {
 220         int i, err = 0;
 221
 222         down_write(&pernet_ops_rwsem);
 223         rtnl_lock();
 224         err = __rtnl_link_register(&dummy_link_ops);
 225         if (err < 0)
 226                 goto out;
 227
 228         for (i = 0; i < numdummies && !err; i++) {
 229                 err = dummy_init_one();
 230                 cond_resched();
 231         }
 232         if (err < 0)
 233                 __rtnl_link_unregister(&dummy_link_ops);
 234
 235 out:
 236         rtnl_unlock();
 237         up_write(&pernet_ops_rwsem);
 238
 239         return err;
 240 }
 241
 242 static void __exit dummy_cleanup_module(void)
 243 {
 244         rtnl_link_unregister(&dummy_link_ops);
 245 }
 246
 247 module_init(dummy_init_module);
 248 module_exit(dummy_cleanup_module);
 249 MODULE_LICENSE("GPL");
 250 MODULE_ALIAS_RTNL_LINK(DRV_NAME);
 251 MODULE_VERSION(DRV_VERSION);