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