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 <linux/u64_stats_sync.h> 58 59 /* blackhole_netdev - a device used for dsts that are marked expired! 60 * This is global device (instead of per-net-ns) since it's not needed 61 * to be per-ns and gets initialized at boot time. 62 */ 63 struct net_device *blackhole_netdev; 64 EXPORT_SYMBOL(blackhole_netdev); 65 66 /* The higher levels take care of making this non-reentrant (it's 67 * called with bh's disabled). 68 */ 69 static netdev_tx_t loopback_xmit(struct sk_buff *skb, 70 struct net_device *dev) 71 { 72 int len; 73 74 skb_tx_timestamp(skb); 75 76 /* do not fool net_timestamp_check() with various clock bases */ 77 skb->tstamp = 0; 78 79 skb_orphan(skb); 80 81 /* Before queueing this packet to netif_rx(), 82 * make sure dst is refcounted. 83 */ 84 skb_dst_force(skb); 85 86 skb->protocol = eth_type_trans(skb, dev); 87 88 len = skb->len; 89 if (likely(netif_rx(skb) == NET_RX_SUCCESS)) 90 dev_lstats_add(dev, len); 91 92 return NETDEV_TX_OK; 93 } 94 95 void dev_lstats_read(struct net_device *dev, u64 *packets, u64 *bytes) 96 { 97 int i; 98 99 *packets = 0; 100 *bytes = 0; 101 102 for_each_possible_cpu(i) { 103 const struct pcpu_lstats *lb_stats; 104 u64 tbytes, tpackets; 105 unsigned int start; 106 107 lb_stats = per_cpu_ptr(dev->lstats, i); 108 do { 109 start = u64_stats_fetch_begin_irq(&lb_stats->syncp); 110 tpackets = u64_stats_read(&lb_stats->packets); 111 tbytes = u64_stats_read(&lb_stats->bytes); 112 } while (u64_stats_fetch_retry_irq(&lb_stats->syncp, start)); 113 *bytes += tbytes; 114 *packets += tpackets; 115 } 116 } 117 EXPORT_SYMBOL(dev_lstats_read); 118 119 static void loopback_get_stats64(struct net_device *dev, 120 struct rtnl_link_stats64 *stats) 121 { 122 u64 packets, bytes; 123 124 dev_lstats_read(dev, &packets, &bytes); 125 126 stats->rx_packets = packets; 127 stats->tx_packets = packets; 128 stats->rx_bytes = bytes; 129 stats->tx_bytes = bytes; 130 } 131 132 static u32 always_on(struct net_device *dev) 133 { 134 return 1; 135 } 136 137 static const struct ethtool_ops loopback_ethtool_ops = { 138 .get_link = always_on, 139 .get_ts_info = ethtool_op_get_ts_info, 140 }; 141 142 static int loopback_dev_init(struct net_device *dev) 143 { 144 dev->lstats = netdev_alloc_pcpu_stats(struct pcpu_lstats); 145 if (!dev->lstats) 146 return -ENOMEM; 147 return 0; 148 } 149 150 static void loopback_dev_free(struct net_device *dev) 151 { 152 dev_net(dev)->loopback_dev = NULL; 153 free_percpu(dev->lstats); 154 } 155 156 static const struct net_device_ops loopback_ops = { 157 .ndo_init = loopback_dev_init, 158 .ndo_start_xmit = loopback_xmit, 159 .ndo_get_stats64 = loopback_get_stats64, 160 .ndo_set_mac_address = eth_mac_addr, 161 }; 162 163 static void gen_lo_setup(struct net_device *dev, 164 unsigned int mtu, 165 const struct ethtool_ops *eth_ops, 166 const struct header_ops *hdr_ops, 167 const struct net_device_ops *dev_ops, 168 void (*dev_destructor)(struct net_device *dev)) 169 { 170 dev->mtu = mtu; 171 dev->hard_header_len = ETH_HLEN; /* 14 */ 172 dev->min_header_len = ETH_HLEN; /* 14 */ 173 dev->addr_len = ETH_ALEN; /* 6 */ 174 dev->type = ARPHRD_LOOPBACK; /* 0x0001*/ 175 dev->flags = IFF_LOOPBACK; 176 dev->priv_flags |= IFF_LIVE_ADDR_CHANGE | IFF_NO_QUEUE; 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_LLTX 186 | NETIF_F_NETNS_LOCAL 187 | NETIF_F_VLAN_CHALLENGED 188 | NETIF_F_LOOPBACK; 189 dev->ethtool_ops = eth_ops; 190 dev->header_ops = hdr_ops; 191 dev->netdev_ops = dev_ops; 192 dev->needs_free_netdev = true; 193 dev->priv_destructor = dev_destructor; 194 } 195 196 /* The loopback device is special. There is only one instance 197 * per network namespace. 198 */ 199 static void loopback_setup(struct net_device *dev) 200 { 201 gen_lo_setup(dev, (64 * 1024), &loopback_ethtool_ops, ð_header_ops, 202 &loopback_ops, loopback_dev_free); 203 } 204 205 /* Setup and register the loopback device. */ 206 static __net_init int loopback_net_init(struct net *net) 207 { 208 struct net_device *dev; 209 int err; 210 211 err = -ENOMEM; 212 dev = alloc_netdev(0, "lo", NET_NAME_UNKNOWN, loopback_setup); 213 if (!dev) 214 goto out; 215 216 dev_net_set(dev, net); 217 err = register_netdev(dev); 218 if (err) 219 goto out_free_netdev; 220 221 BUG_ON(dev->ifindex != LOOPBACK_IFINDEX); 222 net->loopback_dev = dev; 223 return 0; 224 225 out_free_netdev: 226 free_netdev(dev); 227 out: 228 if (net_eq(net, &init_net)) 229 panic("loopback: Failed to register netdevice: %d\n", err); 230 return err; 231 } 232 233 /* Registered in net/core/dev.c */ 234 struct pernet_operations __net_initdata loopback_net_ops = { 235 .init = loopback_net_init, 236 }; 237 238 /* blackhole netdevice */ 239 static netdev_tx_t blackhole_netdev_xmit(struct sk_buff *skb, 240 struct net_device *dev) 241 { 242 kfree_skb(skb); 243 net_warn_ratelimited("%s(): Dropping skb.\n", __func__); 244 return NETDEV_TX_OK; 245 } 246 247 static const struct net_device_ops blackhole_netdev_ops = { 248 .ndo_start_xmit = blackhole_netdev_xmit, 249 }; 250 251 /* This is a dst-dummy device used specifically for invalidated 252 * DSTs and unlike loopback, this is not per-ns. 253 */ 254 static void blackhole_netdev_setup(struct net_device *dev) 255 { 256 gen_lo_setup(dev, ETH_MIN_MTU, NULL, NULL, &blackhole_netdev_ops, NULL); 257 } 258 259 /* Setup and register the blackhole_netdev. */ 260 static int __init blackhole_netdev_init(void) 261 { 262 blackhole_netdev = alloc_netdev(0, "blackhole_dev", NET_NAME_UNKNOWN, 263 blackhole_netdev_setup); 264 if (!blackhole_netdev) 265 return -ENOMEM; 266 267 rtnl_lock(); 268 dev_init_scheduler(blackhole_netdev); 269 dev_activate(blackhole_netdev); 270 rtnl_unlock(); 271 272 blackhole_netdev->flags |= IFF_UP | IFF_RUNNING; 273 dev_net_set(blackhole_netdev, &init_net); 274 275 return 0; 276 } 277 278 device_initcall(blackhole_netdev_init); 279