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 int len; 74 75 skb_tx_timestamp(skb); 76 77 /* do not fool net_timestamp_check() with various clock bases */ 78 skb_clear_tstamp(skb); 79 80 skb_orphan(skb); 81 82 /* Before queueing this packet to __netif_rx(), 83 * make sure dst is refcounted. 84 */ 85 skb_dst_force(skb); 86 87 skb->protocol = eth_type_trans(skb, dev); 88 89 len = skb->len; 90 if (likely(__netif_rx(skb) == NET_RX_SUCCESS)) 91 dev_lstats_add(dev, len); 92 93 return NETDEV_TX_OK; 94 } 95 96 void dev_lstats_read(struct net_device *dev, u64 *packets, u64 *bytes) 97 { 98 int i; 99 100 *packets = 0; 101 *bytes = 0; 102 103 for_each_possible_cpu(i) { 104 const struct pcpu_lstats *lb_stats; 105 u64 tbytes, tpackets; 106 unsigned int start; 107 108 lb_stats = per_cpu_ptr(dev->lstats, i); 109 do { 110 start = u64_stats_fetch_begin(&lb_stats->syncp); 111 tpackets = u64_stats_read(&lb_stats->packets); 112 tbytes = u64_stats_read(&lb_stats->bytes); 113 } while (u64_stats_fetch_retry(&lb_stats->syncp, start)); 114 *bytes += tbytes; 115 *packets += tpackets; 116 } 117 } 118 EXPORT_SYMBOL(dev_lstats_read); 119 120 static void loopback_get_stats64(struct net_device *dev, 121 struct rtnl_link_stats64 *stats) 122 { 123 u64 packets, bytes; 124 125 dev_lstats_read(dev, &packets, &bytes); 126 127 stats->rx_packets = packets; 128 stats->tx_packets = packets; 129 stats->rx_bytes = bytes; 130 stats->tx_bytes = bytes; 131 } 132 133 static u32 always_on(struct net_device *dev) 134 { 135 return 1; 136 } 137 138 static const struct ethtool_ops loopback_ethtool_ops = { 139 .get_link = always_on, 140 .get_ts_info = ethtool_op_get_ts_info, 141 }; 142 143 static int loopback_dev_init(struct net_device *dev) 144 { 145 netdev_lockdep_set_classes(dev); 146 return 0; 147 } 148 149 static void loopback_dev_free(struct net_device *dev) 150 { 151 dev_net(dev)->loopback_dev = NULL; 152 } 153 154 static const struct net_device_ops loopback_ops = { 155 .ndo_init = loopback_dev_init, 156 .ndo_start_xmit = loopback_xmit, 157 .ndo_get_stats64 = loopback_get_stats64, 158 .ndo_set_mac_address = eth_mac_addr, 159 }; 160 161 static void gen_lo_setup(struct net_device *dev, 162 unsigned int mtu, 163 const struct ethtool_ops *eth_ops, 164 const struct header_ops *hdr_ops, 165 const struct net_device_ops *dev_ops, 166 void (*dev_destructor)(struct net_device *dev)) 167 { 168 dev->mtu = mtu; 169 dev->hard_header_len = ETH_HLEN; /* 14 */ 170 dev->min_header_len = ETH_HLEN; /* 14 */ 171 dev->addr_len = ETH_ALEN; /* 6 */ 172 dev->type = ARPHRD_LOOPBACK; /* 0x0001*/ 173 dev->flags = IFF_LOOPBACK; 174 dev->priv_flags |= IFF_LIVE_ADDR_CHANGE | IFF_NO_QUEUE; 175 dev->lltx = true; 176 dev->netns_immutable = true; 177 netif_keep_dst(dev); 178 dev->hw_features = NETIF_F_GSO_SOFTWARE; 179 dev->features = NETIF_F_SG | NETIF_F_FRAGLIST 180 | NETIF_F_GSO_SOFTWARE 181 | NETIF_F_HW_CSUM 182 | NETIF_F_RXCSUM 183 | NETIF_F_SCTP_CRC 184 | NETIF_F_HIGHDMA 185 | NETIF_F_VLAN_CHALLENGED 186 | NETIF_F_LOOPBACK; 187 dev->ethtool_ops = eth_ops; 188 dev->header_ops = hdr_ops; 189 dev->netdev_ops = dev_ops; 190 dev->needs_free_netdev = true; 191 dev->pcpu_stat_type = NETDEV_PCPU_STAT_LSTATS; 192 dev->priv_destructor = dev_destructor; 193 194 netif_set_tso_max_size(dev, GSO_MAX_SIZE); 195 } 196 197 /* The loopback device is special. There is only one instance 198 * per network namespace. 199 */ 200 static void loopback_setup(struct net_device *dev) 201 { 202 gen_lo_setup(dev, (64 * 1024), &loopback_ethtool_ops, ð_header_ops, 203 &loopback_ops, loopback_dev_free); 204 } 205 206 /* Setup and register the loopback device. */ 207 static __net_init int loopback_net_init(struct net *net) 208 { 209 struct net_device *dev; 210 int err; 211 212 err = -ENOMEM; 213 dev = alloc_netdev(0, "lo", NET_NAME_PREDICTABLE, loopback_setup); 214 if (!dev) 215 goto out; 216 217 dev_net_set(dev, net); 218 err = register_netdev(dev); 219 if (err) 220 goto out_free_netdev; 221 222 BUG_ON(dev->ifindex != LOOPBACK_IFINDEX); 223 net->loopback_dev = dev; 224 return 0; 225 226 out_free_netdev: 227 free_netdev(dev); 228 out: 229 if (net_eq(net, &init_net)) 230 panic("loopback: Failed to register netdevice: %d\n", err); 231 return err; 232 } 233 234 /* Registered in net/core/dev.c */ 235 struct pernet_operations __net_initdata loopback_net_ops = { 236 .init = loopback_net_init, 237 }; 238 239 /* blackhole netdevice */ 240 static netdev_tx_t blackhole_netdev_xmit(struct sk_buff *skb, 241 struct net_device *dev) 242 { 243 kfree_skb(skb); 244 net_warn_ratelimited("%s(): Dropping skb.\n", __func__); 245 return NETDEV_TX_OK; 246 } 247 248 static int blackhole_neigh_output(struct neighbour *n, struct sk_buff *skb) 249 { 250 kfree_skb(skb); 251 return 0; 252 } 253 254 static int blackhole_neigh_construct(struct net_device *dev, 255 struct neighbour *n) 256 { 257 n->output = blackhole_neigh_output; 258 return 0; 259 } 260 261 static const struct net_device_ops blackhole_netdev_ops = { 262 .ndo_start_xmit = blackhole_netdev_xmit, 263 .ndo_neigh_construct = blackhole_neigh_construct, 264 }; 265 266 /* This is a dst-dummy device used specifically for invalidated 267 * DSTs and unlike loopback, this is not per-ns. 268 */ 269 static void blackhole_netdev_setup(struct net_device *dev) 270 { 271 gen_lo_setup(dev, ETH_MIN_MTU, NULL, NULL, &blackhole_netdev_ops, NULL); 272 } 273 274 /* Setup and register the blackhole_netdev. */ 275 static int __init blackhole_netdev_init(void) 276 { 277 blackhole_netdev = alloc_netdev(0, "blackhole_dev", NET_NAME_UNKNOWN, 278 blackhole_netdev_setup); 279 if (!blackhole_netdev) 280 return -ENOMEM; 281 282 rtnl_net_lock(&init_net); 283 dev_init_scheduler(blackhole_netdev); 284 dev_activate(blackhole_netdev); 285 rtnl_net_unlock(&init_net); 286 287 blackhole_netdev->flags |= IFF_UP | IFF_RUNNING; 288 289 return 0; 290 } 291 292 device_initcall(blackhole_netdev_init); 293