1 // SPDX-License-Identifier: GPL-2.0-or-later 2 /* 3 * INET An implementation of the TCP/IP protocol suite for the LINUX 4 * operating system. INET is implemented using the BSD Socket 5 * interface as the means of communication with the user level. 6 * 7 * Pseudo-driver for the loopback interface. 8 * 9 * Version: @(#)loopback.c 1.0.4b 08/16/93 10 * 11 * Authors: Ross Biro 12 * Fred N. van Kempen, <waltje@uWalt.NL.Mugnet.ORG> 13 * Donald Becker, <becker@scyld.com> 14 * 15 * Alan Cox : Fixed oddments for NET3.014 16 * Alan Cox : Rejig for NET3.029 snap #3 17 * Alan Cox : Fixed NET3.029 bugs and sped up 18 * Larry McVoy : Tiny tweak to double performance 19 * Alan Cox : Backed out LMV's tweak - the linux mm 20 * can't take it... 21 * Michael Griffith: Don't bother computing the checksums 22 * on packets received on the loopback 23 * interface. 24 * Alexey Kuznetsov: Potential hang under some extreme 25 * cases removed. 26 */ 27 #include <linux/kernel.h> 28 #include <linux/jiffies.h> 29 #include <linux/module.h> 30 #include <linux/interrupt.h> 31 #include <linux/fs.h> 32 #include <linux/types.h> 33 #include <linux/string.h> 34 #include <linux/socket.h> 35 #include <linux/errno.h> 36 #include <linux/fcntl.h> 37 #include <linux/in.h> 38 39 #include <linux/uaccess.h> 40 #include <linux/io.h> 41 42 #include <linux/inet.h> 43 #include <linux/netdevice.h> 44 #include <linux/etherdevice.h> 45 #include <linux/skbuff.h> 46 #include <linux/ethtool.h> 47 #include <net/sch_generic.h> 48 #include <net/sock.h> 49 #include <net/checksum.h> 50 #include <linux/if_ether.h> /* For the statistics structure. */ 51 #include <linux/if_arp.h> /* For ARPHRD_ETHER */ 52 #include <linux/ip.h> 53 #include <linux/tcp.h> 54 #include <linux/percpu.h> 55 #include <linux/net_tstamp.h> 56 #include <net/net_namespace.h> 57 #include <net/netdev_lock.h> 58 #include <linux/u64_stats_sync.h> 59 60 /* blackhole_netdev - a device used for dsts that are marked expired! 61 * This is global device (instead of per-net-ns) since it's not needed 62 * to be per-ns and gets initialized at boot time. 63 */ 64 struct net_device *blackhole_netdev; 65 EXPORT_SYMBOL(blackhole_netdev); 66 67 /* The higher levels take care of making this non-reentrant (it's 68 * called with bh's disabled). 69 */ 70 static netdev_tx_t loopback_xmit(struct sk_buff *skb, 71 struct net_device *dev) 72 { 73 enum skb_drop_reason reason; 74 int len; 75 76 skb_tx_timestamp(skb); 77 78 /* do not fool net_timestamp_check() with various clock bases */ 79 skb_clear_tstamp(skb); 80 81 skb_orphan(skb); 82 83 /* Before queueing this packet to __netif_rx(), 84 * make sure dst is refcounted. 85 */ 86 skb_dst_force(skb); 87 88 reason = eth_type_trans_careful(skb, dev); 89 if (unlikely(reason)) { 90 dev_core_stats_tx_dropped_inc(dev); 91 kfree_skb_reason(skb, reason); 92 return NETDEV_TX_OK; 93 } 94 95 len = skb->len; 96 if (likely(__netif_rx(skb) == NET_RX_SUCCESS)) 97 dev_lstats_add(dev, len); 98 99 return NETDEV_TX_OK; 100 } 101 102 void dev_lstats_read(struct net_device *dev, u64 *packets, u64 *bytes) 103 { 104 int i; 105 106 *packets = 0; 107 *bytes = 0; 108 109 for_each_possible_cpu(i) { 110 const struct pcpu_lstats *lb_stats; 111 u64 tbytes, tpackets; 112 unsigned int start; 113 114 lb_stats = per_cpu_ptr(dev->lstats, i); 115 do { 116 start = u64_stats_fetch_begin(&lb_stats->syncp); 117 tpackets = u64_stats_read(&lb_stats->packets); 118 tbytes = u64_stats_read(&lb_stats->bytes); 119 } while (u64_stats_fetch_retry(&lb_stats->syncp, start)); 120 *bytes += tbytes; 121 *packets += tpackets; 122 } 123 } 124 EXPORT_SYMBOL(dev_lstats_read); 125 126 static void loopback_get_stats64(struct net_device *dev, 127 struct rtnl_link_stats64 *stats) 128 { 129 u64 packets, bytes; 130 131 dev_lstats_read(dev, &packets, &bytes); 132 133 stats->rx_packets = packets; 134 stats->tx_packets = packets; 135 stats->rx_bytes = bytes; 136 stats->tx_bytes = bytes; 137 } 138 139 static u32 always_on(struct net_device *dev) 140 { 141 return 1; 142 } 143 144 static const struct ethtool_ops loopback_ethtool_ops = { 145 .get_link = always_on, 146 .get_ts_info = ethtool_op_get_ts_info, 147 }; 148 149 static int loopback_dev_init(struct net_device *dev) 150 { 151 netdev_lockdep_set_classes(dev); 152 return 0; 153 } 154 155 static void loopback_dev_free(struct net_device *dev) 156 { 157 dev_net(dev)->loopback_dev = NULL; 158 } 159 160 static const struct net_device_ops loopback_ops = { 161 .ndo_init = loopback_dev_init, 162 .ndo_start_xmit = loopback_xmit, 163 .ndo_get_stats64 = loopback_get_stats64, 164 .ndo_set_mac_address = eth_mac_addr, 165 }; 166 167 static void gen_lo_setup(struct net_device *dev, 168 unsigned int mtu, 169 const struct ethtool_ops *eth_ops, 170 const struct header_ops *hdr_ops, 171 const struct net_device_ops *dev_ops, 172 void (*dev_destructor)(struct net_device *dev)) 173 { 174 dev->mtu = mtu; 175 dev->hard_header_len = ETH_HLEN; /* 14 */ 176 dev->min_header_len = ETH_HLEN; /* 14 */ 177 dev->addr_len = ETH_ALEN; /* 6 */ 178 dev->type = ARPHRD_LOOPBACK; /* 0x0001*/ 179 dev->flags = IFF_LOOPBACK; 180 dev->priv_flags |= IFF_LIVE_ADDR_CHANGE | IFF_NO_QUEUE; 181 dev->lltx = true; 182 dev->netns_immutable = true; 183 netif_keep_dst(dev); 184 dev->hw_features = NETIF_F_GSO_SOFTWARE; 185 dev->features = NETIF_F_SG | NETIF_F_FRAGLIST 186 | NETIF_F_GSO_SOFTWARE 187 | NETIF_F_HW_CSUM 188 | NETIF_F_RXCSUM 189 | NETIF_F_SCTP_CRC 190 | NETIF_F_HIGHDMA 191 | NETIF_F_VLAN_CHALLENGED 192 | NETIF_F_LOOPBACK; 193 dev->ethtool_ops = eth_ops; 194 dev->header_ops = hdr_ops; 195 dev->netdev_ops = dev_ops; 196 dev->needs_free_netdev = true; 197 dev->pcpu_stat_type = NETDEV_PCPU_STAT_LSTATS; 198 dev->priv_destructor = dev_destructor; 199 200 netif_set_tso_max_size(dev, GSO_MAX_SIZE); 201 } 202 203 /* The loopback device is special. There is only one instance 204 * per network namespace. 205 */ 206 static void loopback_setup(struct net_device *dev) 207 { 208 gen_lo_setup(dev, (64 * 1024), &loopback_ethtool_ops, ð_header_ops, 209 &loopback_ops, loopback_dev_free); 210 } 211 212 /* Setup and register the loopback device. */ 213 static __net_init int loopback_net_init(struct net *net) 214 { 215 struct net_device *dev; 216 int err; 217 218 err = -ENOMEM; 219 dev = alloc_netdev(0, "lo", NET_NAME_PREDICTABLE, loopback_setup); 220 if (!dev) 221 goto out; 222 223 dev_net_set(dev, net); 224 err = register_netdev(dev); 225 if (err) 226 goto out_free_netdev; 227 228 BUG_ON(dev->ifindex != LOOPBACK_IFINDEX); 229 net->loopback_dev = dev; 230 return 0; 231 232 out_free_netdev: 233 free_netdev(dev); 234 out: 235 if (net_eq(net, &init_net)) 236 panic("loopback: Failed to register netdevice: %d\n", err); 237 return err; 238 } 239 240 /* Registered in net/core/dev.c */ 241 struct pernet_operations __net_initdata loopback_net_ops = { 242 .init = loopback_net_init, 243 }; 244 245 /* blackhole netdevice */ 246 static netdev_tx_t blackhole_netdev_xmit(struct sk_buff *skb, 247 struct net_device *dev) 248 { 249 kfree_skb(skb); 250 net_warn_ratelimited("%s(): Dropping skb.\n", __func__); 251 return NETDEV_TX_OK; 252 } 253 254 static int blackhole_neigh_output(struct neighbour *n, struct sk_buff *skb) 255 { 256 kfree_skb(skb); 257 return 0; 258 } 259 260 static int blackhole_neigh_construct(struct net_device *dev, 261 struct neighbour *n) 262 { 263 n->output = blackhole_neigh_output; 264 return 0; 265 } 266 267 static const struct net_device_ops blackhole_netdev_ops = { 268 .ndo_start_xmit = blackhole_netdev_xmit, 269 .ndo_neigh_construct = blackhole_neigh_construct, 270 }; 271 272 /* This is a dst-dummy device used specifically for invalidated 273 * DSTs and unlike loopback, this is not per-ns. 274 */ 275 static void blackhole_netdev_setup(struct net_device *dev) 276 { 277 gen_lo_setup(dev, ETH_MIN_MTU, NULL, NULL, &blackhole_netdev_ops, NULL); 278 } 279 280 /* Setup and register the blackhole_netdev. */ 281 static int __init blackhole_netdev_init(void) 282 { 283 blackhole_netdev = alloc_netdev(0, "blackhole_dev", NET_NAME_UNKNOWN, 284 blackhole_netdev_setup); 285 if (!blackhole_netdev) 286 return -ENOMEM; 287 288 rtnl_net_lock(&init_net); 289 dev_init_scheduler(blackhole_netdev); 290 dev_activate(blackhole_netdev); 291 rtnl_net_unlock(&init_net); 292 293 blackhole_netdev->flags |= IFF_UP | IFF_RUNNING; 294 295 return 0; 296 } 297 298 subsys_initcall_sync(blackhole_netdev_init); 299