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/ethtool.h> 36 #include <linux/init.h> 37 #include <linux/moduleparam.h> 38 #include <linux/rtnetlink.h> 39 #include <linux/net_tstamp.h> 40 #include <net/rtnetlink.h> 41 #include <linux/u64_stats_sync.h> 42 43 #define DRV_NAME "dummy" 44 #define DRV_VERSION "1.0" 45 46 static int numdummies = 1; 47 48 /* fake multicast ability */ 49 static void set_multicast_list(struct net_device *dev) 50 { 51 } 52 53 struct pcpu_dstats { 54 u64 tx_packets; 55 u64 tx_bytes; 56 struct u64_stats_sync syncp; 57 }; 58 59 static void dummy_get_stats64(struct net_device *dev, 60 struct rtnl_link_stats64 *stats) 61 { 62 int i; 63 64 for_each_possible_cpu(i) { 65 const struct pcpu_dstats *dstats; 66 u64 tbytes, tpackets; 67 unsigned int start; 68 69 dstats = per_cpu_ptr(dev->dstats, i); 70 do { 71 start = u64_stats_fetch_begin_irq(&dstats->syncp); 72 tbytes = dstats->tx_bytes; 73 tpackets = dstats->tx_packets; 74 } while (u64_stats_fetch_retry_irq(&dstats->syncp, start)); 75 stats->tx_bytes += tbytes; 76 stats->tx_packets += tpackets; 77 } 78 } 79 80 static netdev_tx_t dummy_xmit(struct sk_buff *skb, struct net_device *dev) 81 { 82 struct pcpu_dstats *dstats = this_cpu_ptr(dev->dstats); 83 84 u64_stats_update_begin(&dstats->syncp); 85 dstats->tx_packets++; 86 dstats->tx_bytes += skb->len; 87 u64_stats_update_end(&dstats->syncp); 88 89 skb_tx_timestamp(skb); 90 dev_kfree_skb(skb); 91 return NETDEV_TX_OK; 92 } 93 94 static int dummy_dev_init(struct net_device *dev) 95 { 96 dev->dstats = netdev_alloc_pcpu_stats(struct pcpu_dstats); 97 if (!dev->dstats) 98 return -ENOMEM; 99 100 return 0; 101 } 102 103 static void dummy_dev_uninit(struct net_device *dev) 104 { 105 free_percpu(dev->dstats); 106 } 107 108 static int dummy_change_carrier(struct net_device *dev, bool new_carrier) 109 { 110 if (new_carrier) 111 netif_carrier_on(dev); 112 else 113 netif_carrier_off(dev); 114 return 0; 115 } 116 117 static const struct net_device_ops dummy_netdev_ops = { 118 .ndo_init = dummy_dev_init, 119 .ndo_uninit = dummy_dev_uninit, 120 .ndo_start_xmit = dummy_xmit, 121 .ndo_validate_addr = eth_validate_addr, 122 .ndo_set_rx_mode = set_multicast_list, 123 .ndo_set_mac_address = eth_mac_addr, 124 .ndo_get_stats64 = dummy_get_stats64, 125 .ndo_change_carrier = dummy_change_carrier, 126 }; 127 128 static void dummy_get_drvinfo(struct net_device *dev, 129 struct ethtool_drvinfo *info) 130 { 131 strlcpy(info->driver, DRV_NAME, sizeof(info->driver)); 132 strlcpy(info->version, DRV_VERSION, sizeof(info->version)); 133 } 134 135 static const struct ethtool_ops dummy_ethtool_ops = { 136 .get_drvinfo = dummy_get_drvinfo, 137 .get_ts_info = ethtool_op_get_ts_info, 138 }; 139 140 static void dummy_setup(struct net_device *dev) 141 { 142 ether_setup(dev); 143 144 /* Initialize the device structure. */ 145 dev->netdev_ops = &dummy_netdev_ops; 146 dev->ethtool_ops = &dummy_ethtool_ops; 147 dev->needs_free_netdev = true; 148 149 /* Fill in device structure with ethernet-generic values. */ 150 dev->flags |= IFF_NOARP; 151 dev->flags &= ~IFF_MULTICAST; 152 dev->priv_flags |= IFF_LIVE_ADDR_CHANGE | IFF_NO_QUEUE; 153 dev->features |= NETIF_F_SG | NETIF_F_FRAGLIST; 154 dev->features |= NETIF_F_ALL_TSO; 155 dev->features |= NETIF_F_HW_CSUM | NETIF_F_HIGHDMA | NETIF_F_LLTX; 156 dev->features |= NETIF_F_GSO_ENCAP_ALL; 157 dev->hw_features |= dev->features; 158 dev->hw_enc_features |= dev->features; 159 eth_hw_addr_random(dev); 160 161 dev->min_mtu = 0; 162 dev->max_mtu = 0; 163 } 164 165 static int dummy_validate(struct nlattr *tb[], struct nlattr *data[], 166 struct netlink_ext_ack *extack) 167 { 168 if (tb[IFLA_ADDRESS]) { 169 if (nla_len(tb[IFLA_ADDRESS]) != ETH_ALEN) 170 return -EINVAL; 171 if (!is_valid_ether_addr(nla_data(tb[IFLA_ADDRESS]))) 172 return -EADDRNOTAVAIL; 173 } 174 return 0; 175 } 176 177 static struct rtnl_link_ops dummy_link_ops __read_mostly = { 178 .kind = DRV_NAME, 179 .setup = dummy_setup, 180 .validate = dummy_validate, 181 }; 182 183 /* Number of dummy devices to be set up by this module. */ 184 module_param(numdummies, int, 0); 185 MODULE_PARM_DESC(numdummies, "Number of dummy pseudo devices"); 186 187 static int __init dummy_init_one(void) 188 { 189 struct net_device *dev_dummy; 190 int err; 191 192 dev_dummy = alloc_netdev(0, "dummy%d", NET_NAME_ENUM, dummy_setup); 193 if (!dev_dummy) 194 return -ENOMEM; 195 196 dev_dummy->rtnl_link_ops = &dummy_link_ops; 197 err = register_netdevice(dev_dummy); 198 if (err < 0) 199 goto err; 200 return 0; 201 202 err: 203 free_netdev(dev_dummy); 204 return err; 205 } 206 207 static int __init dummy_init_module(void) 208 { 209 int i, err = 0; 210 211 down_write(&pernet_ops_rwsem); 212 rtnl_lock(); 213 err = __rtnl_link_register(&dummy_link_ops); 214 if (err < 0) 215 goto out; 216 217 for (i = 0; i < numdummies && !err; i++) { 218 err = dummy_init_one(); 219 cond_resched(); 220 } 221 if (err < 0) 222 __rtnl_link_unregister(&dummy_link_ops); 223 224 out: 225 rtnl_unlock(); 226 up_write(&pernet_ops_rwsem); 227 228 return err; 229 } 230 231 static void __exit dummy_cleanup_module(void) 232 { 233 rtnl_link_unregister(&dummy_link_ops); 234 } 235 236 module_init(dummy_init_module); 237 module_exit(dummy_cleanup_module); 238 MODULE_LICENSE("GPL"); 239 MODULE_ALIAS_RTNL_LINK(DRV_NAME); 240 MODULE_VERSION(DRV_VERSION); 241