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 <linux/net_tstamp.h> 39 #include <net/rtnetlink.h> 40 #include <linux/u64_stats_sync.h> 41 42 #define DRV_NAME "dummy" 43 #define DRV_VERSION "1.0" 44 45 static int numdummies = 1; 46 47 /* fake multicast ability */ 48 static void set_multicast_list(struct net_device *dev) 49 { 50 } 51 52 struct pcpu_dstats { 53 u64 tx_packets; 54 u64 tx_bytes; 55 struct u64_stats_sync syncp; 56 }; 57 58 static void dummy_get_stats64(struct net_device *dev, 59 struct rtnl_link_stats64 *stats) 60 { 61 int i; 62 63 for_each_possible_cpu(i) { 64 const struct pcpu_dstats *dstats; 65 u64 tbytes, tpackets; 66 unsigned int start; 67 68 dstats = per_cpu_ptr(dev->dstats, i); 69 do { 70 start = u64_stats_fetch_begin_irq(&dstats->syncp); 71 tbytes = dstats->tx_bytes; 72 tpackets = dstats->tx_packets; 73 } while (u64_stats_fetch_retry_irq(&dstats->syncp, start)); 74 stats->tx_bytes += tbytes; 75 stats->tx_packets += tpackets; 76 } 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 skb_tx_timestamp(skb); 89 dev_kfree_skb(skb); 90 return NETDEV_TX_OK; 91 } 92 93 static int dummy_dev_init(struct net_device *dev) 94 { 95 dev->dstats = netdev_alloc_pcpu_stats(struct pcpu_dstats); 96 if (!dev->dstats) 97 return -ENOMEM; 98 99 return 0; 100 } 101 102 static void dummy_dev_uninit(struct net_device *dev) 103 { 104 free_percpu(dev->dstats); 105 } 106 107 static int dummy_change_carrier(struct net_device *dev, bool new_carrier) 108 { 109 if (new_carrier) 110 netif_carrier_on(dev); 111 else 112 netif_carrier_off(dev); 113 return 0; 114 } 115 116 static const struct net_device_ops dummy_netdev_ops = { 117 .ndo_init = dummy_dev_init, 118 .ndo_uninit = dummy_dev_uninit, 119 .ndo_start_xmit = dummy_xmit, 120 .ndo_validate_addr = eth_validate_addr, 121 .ndo_set_rx_mode = set_multicast_list, 122 .ndo_set_mac_address = eth_mac_addr, 123 .ndo_get_stats64 = dummy_get_stats64, 124 .ndo_change_carrier = dummy_change_carrier, 125 }; 126 127 static void dummy_get_drvinfo(struct net_device *dev, 128 struct ethtool_drvinfo *info) 129 { 130 strlcpy(info->driver, DRV_NAME, sizeof(info->driver)); 131 strlcpy(info->version, DRV_VERSION, sizeof(info->version)); 132 } 133 134 static int dummy_get_ts_info(struct net_device *dev, 135 struct ethtool_ts_info *ts_info) 136 { 137 ts_info->so_timestamping = SOF_TIMESTAMPING_TX_SOFTWARE | 138 SOF_TIMESTAMPING_RX_SOFTWARE | 139 SOF_TIMESTAMPING_SOFTWARE; 140 141 ts_info->phc_index = -1; 142 143 return 0; 144 }; 145 146 static const struct ethtool_ops dummy_ethtool_ops = { 147 .get_drvinfo = dummy_get_drvinfo, 148 .get_ts_info = dummy_get_ts_info, 149 }; 150 151 static void dummy_setup(struct net_device *dev) 152 { 153 ether_setup(dev); 154 155 /* Initialize the device structure. */ 156 dev->netdev_ops = &dummy_netdev_ops; 157 dev->ethtool_ops = &dummy_ethtool_ops; 158 dev->needs_free_netdev = true; 159 160 /* Fill in device structure with ethernet-generic values. */ 161 dev->flags |= IFF_NOARP; 162 dev->flags &= ~IFF_MULTICAST; 163 dev->priv_flags |= IFF_LIVE_ADDR_CHANGE | IFF_NO_QUEUE; 164 dev->features |= NETIF_F_SG | NETIF_F_FRAGLIST; 165 dev->features |= NETIF_F_ALL_TSO; 166 dev->features |= NETIF_F_HW_CSUM | NETIF_F_HIGHDMA | NETIF_F_LLTX; 167 dev->features |= NETIF_F_GSO_ENCAP_ALL; 168 dev->hw_features |= dev->features; 169 dev->hw_enc_features |= dev->features; 170 eth_hw_addr_random(dev); 171 172 dev->min_mtu = 0; 173 dev->max_mtu = 0; 174 } 175 176 static int dummy_validate(struct nlattr *tb[], struct nlattr *data[], 177 struct netlink_ext_ack *extack) 178 { 179 if (tb[IFLA_ADDRESS]) { 180 if (nla_len(tb[IFLA_ADDRESS]) != ETH_ALEN) 181 return -EINVAL; 182 if (!is_valid_ether_addr(nla_data(tb[IFLA_ADDRESS]))) 183 return -EADDRNOTAVAIL; 184 } 185 return 0; 186 } 187 188 static struct rtnl_link_ops dummy_link_ops __read_mostly = { 189 .kind = DRV_NAME, 190 .setup = dummy_setup, 191 .validate = dummy_validate, 192 }; 193 194 /* Number of dummy devices to be set up by this module. */ 195 module_param(numdummies, int, 0); 196 MODULE_PARM_DESC(numdummies, "Number of dummy pseudo devices"); 197 198 static int __init dummy_init_one(void) 199 { 200 struct net_device *dev_dummy; 201 int err; 202 203 dev_dummy = alloc_netdev(0, "dummy%d", NET_NAME_ENUM, dummy_setup); 204 if (!dev_dummy) 205 return -ENOMEM; 206 207 dev_dummy->rtnl_link_ops = &dummy_link_ops; 208 err = register_netdevice(dev_dummy); 209 if (err < 0) 210 goto err; 211 return 0; 212 213 err: 214 free_netdev(dev_dummy); 215 return err; 216 } 217 218 static int __init dummy_init_module(void) 219 { 220 int i, err = 0; 221 222 rtnl_lock(); 223 err = __rtnl_link_register(&dummy_link_ops); 224 if (err < 0) 225 goto out; 226 227 for (i = 0; i < numdummies && !err; i++) { 228 err = dummy_init_one(); 229 cond_resched(); 230 } 231 if (err < 0) 232 __rtnl_link_unregister(&dummy_link_ops); 233 234 out: 235 rtnl_unlock(); 236 237 return err; 238 } 239 240 static void __exit dummy_cleanup_module(void) 241 { 242 rtnl_link_unregister(&dummy_link_ops); 243 } 244 245 module_init(dummy_init_module); 246 module_exit(dummy_cleanup_module); 247 MODULE_LICENSE("GPL"); 248 MODULE_ALIAS_RTNL_LINK(DRV_NAME); 249 MODULE_VERSION(DRV_VERSION); 250