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->tx_queue_len = 0; 148 dev->flags |= IFF_NOARP; 149 dev->flags &= ~IFF_MULTICAST; 150 dev->priv_flags |= IFF_LIVE_ADDR_CHANGE; 151 dev->features |= NETIF_F_SG | NETIF_F_FRAGLIST | NETIF_F_TSO; 152 dev->features |= NETIF_F_HW_CSUM | NETIF_F_HIGHDMA | NETIF_F_LLTX; 153 eth_hw_addr_random(dev); 154 } 155 156 static int dummy_validate(struct nlattr *tb[], struct nlattr *data[]) 157 { 158 if (tb[IFLA_ADDRESS]) { 159 if (nla_len(tb[IFLA_ADDRESS]) != ETH_ALEN) 160 return -EINVAL; 161 if (!is_valid_ether_addr(nla_data(tb[IFLA_ADDRESS]))) 162 return -EADDRNOTAVAIL; 163 } 164 return 0; 165 } 166 167 static struct rtnl_link_ops dummy_link_ops __read_mostly = { 168 .kind = DRV_NAME, 169 .setup = dummy_setup, 170 .validate = dummy_validate, 171 }; 172 173 /* Number of dummy devices to be set up by this module. */ 174 module_param(numdummies, int, 0); 175 MODULE_PARM_DESC(numdummies, "Number of dummy pseudo devices"); 176 177 static int __init dummy_init_one(void) 178 { 179 struct net_device *dev_dummy; 180 int err; 181 182 dev_dummy = alloc_netdev(0, "dummy%d", NET_NAME_UNKNOWN, dummy_setup); 183 if (!dev_dummy) 184 return -ENOMEM; 185 186 dev_dummy->rtnl_link_ops = &dummy_link_ops; 187 err = register_netdevice(dev_dummy); 188 if (err < 0) 189 goto err; 190 return 0; 191 192 err: 193 free_netdev(dev_dummy); 194 return err; 195 } 196 197 static int __init dummy_init_module(void) 198 { 199 int i, err = 0; 200 201 rtnl_lock(); 202 err = __rtnl_link_register(&dummy_link_ops); 203 if (err < 0) 204 goto out; 205 206 for (i = 0; i < numdummies && !err; i++) { 207 err = dummy_init_one(); 208 cond_resched(); 209 } 210 if (err < 0) 211 __rtnl_link_unregister(&dummy_link_ops); 212 213 out: 214 rtnl_unlock(); 215 216 return err; 217 } 218 219 static void __exit dummy_cleanup_module(void) 220 { 221 rtnl_link_unregister(&dummy_link_ops); 222 } 223 224 module_init(dummy_init_module); 225 module_exit(dummy_cleanup_module); 226 MODULE_LICENSE("GPL"); 227 MODULE_ALIAS_RTNL_LINK(DRV_NAME); 228 MODULE_VERSION(DRV_VERSION); 229