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 void 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 } 77 78 static netdev_tx_t dummy_xmit(struct sk_buff *skb, struct net_device *dev) 79 { 80 struct pcpu_dstats *dstats = this_cpu_ptr(dev->dstats); 81 82 u64_stats_update_begin(&dstats->syncp); 83 dstats->tx_packets++; 84 dstats->tx_bytes += skb->len; 85 u64_stats_update_end(&dstats->syncp); 86 87 dev_kfree_skb(skb); 88 return NETDEV_TX_OK; 89 } 90 91 static int dummy_dev_init(struct net_device *dev) 92 { 93 dev->dstats = netdev_alloc_pcpu_stats(struct pcpu_dstats); 94 if (!dev->dstats) 95 return -ENOMEM; 96 97 return 0; 98 } 99 100 static void dummy_dev_uninit(struct net_device *dev) 101 { 102 free_percpu(dev->dstats); 103 } 104 105 static int dummy_change_carrier(struct net_device *dev, bool new_carrier) 106 { 107 if (new_carrier) 108 netif_carrier_on(dev); 109 else 110 netif_carrier_off(dev); 111 return 0; 112 } 113 114 static const struct net_device_ops dummy_netdev_ops = { 115 .ndo_init = dummy_dev_init, 116 .ndo_uninit = dummy_dev_uninit, 117 .ndo_start_xmit = dummy_xmit, 118 .ndo_validate_addr = eth_validate_addr, 119 .ndo_set_rx_mode = set_multicast_list, 120 .ndo_set_mac_address = eth_mac_addr, 121 .ndo_get_stats64 = dummy_get_stats64, 122 .ndo_change_carrier = dummy_change_carrier, 123 }; 124 125 static void dummy_get_drvinfo(struct net_device *dev, 126 struct ethtool_drvinfo *info) 127 { 128 strlcpy(info->driver, DRV_NAME, sizeof(info->driver)); 129 strlcpy(info->version, DRV_VERSION, sizeof(info->version)); 130 } 131 132 static const struct ethtool_ops dummy_ethtool_ops = { 133 .get_drvinfo = dummy_get_drvinfo, 134 }; 135 136 static void dummy_setup(struct net_device *dev) 137 { 138 ether_setup(dev); 139 140 /* Initialize the device structure. */ 141 dev->netdev_ops = &dummy_netdev_ops; 142 dev->ethtool_ops = &dummy_ethtool_ops; 143 dev->destructor = free_netdev; 144 145 /* Fill in device structure with ethernet-generic values. */ 146 dev->flags |= IFF_NOARP; 147 dev->flags &= ~IFF_MULTICAST; 148 dev->priv_flags |= IFF_LIVE_ADDR_CHANGE | IFF_NO_QUEUE; 149 dev->features |= NETIF_F_SG | NETIF_F_FRAGLIST; 150 dev->features |= NETIF_F_ALL_TSO | NETIF_F_UFO; 151 dev->features |= NETIF_F_HW_CSUM | NETIF_F_HIGHDMA | NETIF_F_LLTX; 152 dev->features |= NETIF_F_GSO_ENCAP_ALL; 153 dev->hw_features |= dev->features; 154 dev->hw_enc_features |= dev->features; 155 eth_hw_addr_random(dev); 156 157 dev->min_mtu = 0; 158 dev->max_mtu = ETH_MAX_MTU; 159 } 160 161 static int dummy_validate(struct nlattr *tb[], struct nlattr *data[]) 162 { 163 if (tb[IFLA_ADDRESS]) { 164 if (nla_len(tb[IFLA_ADDRESS]) != ETH_ALEN) 165 return -EINVAL; 166 if (!is_valid_ether_addr(nla_data(tb[IFLA_ADDRESS]))) 167 return -EADDRNOTAVAIL; 168 } 169 return 0; 170 } 171 172 static struct rtnl_link_ops dummy_link_ops __read_mostly = { 173 .kind = DRV_NAME, 174 .setup = dummy_setup, 175 .validate = dummy_validate, 176 }; 177 178 /* Number of dummy devices to be set up by this module. */ 179 module_param(numdummies, int, 0); 180 MODULE_PARM_DESC(numdummies, "Number of dummy pseudo devices"); 181 182 static int __init dummy_init_one(void) 183 { 184 struct net_device *dev_dummy; 185 int err; 186 187 dev_dummy = alloc_netdev(0, "dummy%d", NET_NAME_UNKNOWN, dummy_setup); 188 if (!dev_dummy) 189 return -ENOMEM; 190 191 dev_dummy->rtnl_link_ops = &dummy_link_ops; 192 err = register_netdevice(dev_dummy); 193 if (err < 0) 194 goto err; 195 return 0; 196 197 err: 198 free_netdev(dev_dummy); 199 return err; 200 } 201 202 static int __init dummy_init_module(void) 203 { 204 int i, err = 0; 205 206 rtnl_lock(); 207 err = __rtnl_link_register(&dummy_link_ops); 208 if (err < 0) 209 goto out; 210 211 for (i = 0; i < numdummies && !err; i++) { 212 err = dummy_init_one(); 213 cond_resched(); 214 } 215 if (err < 0) 216 __rtnl_link_unregister(&dummy_link_ops); 217 218 out: 219 rtnl_unlock(); 220 221 return err; 222 } 223 224 static void __exit dummy_cleanup_module(void) 225 { 226 rtnl_link_unregister(&dummy_link_ops); 227 } 228 229 module_init(dummy_init_module); 230 module_exit(dummy_cleanup_module); 231 MODULE_LICENSE("GPL"); 232 MODULE_ALIAS_RTNL_LINK(DRV_NAME); 233 MODULE_VERSION(DRV_VERSION); 234