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