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/sock.h> 48 #include <net/checksum.h> 49 #include <linux/if_ether.h> /* For the statistics structure. */ 50 #include <linux/if_arp.h> /* For ARPHRD_ETHER */ 51 #include <linux/ip.h> 52 #include <linux/tcp.h> 53 #include <linux/percpu.h> 54 #include <linux/net_tstamp.h> 55 #include <net/net_namespace.h> 56 #include <linux/u64_stats_sync.h> 57 58 /* blackhole_netdev - a device used for dsts that are marked expired! 59 * This is global device (instead of per-net-ns) since it's not needed 60 * to be per-ns and gets initialized at boot time. 61 */ 62 struct net_device *blackhole_netdev; 63 EXPORT_SYMBOL(blackhole_netdev); 64 65 /* The higher levels take care of making this non-reentrant (it's 66 * called with bh's disabled). 67 */ 68 static netdev_tx_t loopback_xmit(struct sk_buff *skb, 69 struct net_device *dev) 70 { 71 struct pcpu_lstats *lb_stats; 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 /* it's OK to use per_cpu_ptr() because BHs are off */ 89 lb_stats = this_cpu_ptr(dev->lstats); 90 91 len = skb->len; 92 if (likely(netif_rx(skb) == NET_RX_SUCCESS)) { 93 u64_stats_update_begin(&lb_stats->syncp); 94 lb_stats->bytes += len; 95 lb_stats->packets++; 96 u64_stats_update_end(&lb_stats->syncp); 97 } 98 99 return NETDEV_TX_OK; 100 } 101 102 static void loopback_get_stats64(struct net_device *dev, 103 struct rtnl_link_stats64 *stats) 104 { 105 u64 bytes = 0; 106 u64 packets = 0; 107 int i; 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_irq(&lb_stats->syncp); 117 tbytes = lb_stats->bytes; 118 tpackets = lb_stats->packets; 119 } while (u64_stats_fetch_retry_irq(&lb_stats->syncp, start)); 120 bytes += tbytes; 121 packets += tpackets; 122 } 123 stats->rx_packets = packets; 124 stats->tx_packets = packets; 125 stats->rx_bytes = bytes; 126 stats->tx_bytes = bytes; 127 } 128 129 static u32 always_on(struct net_device *dev) 130 { 131 return 1; 132 } 133 134 static const struct ethtool_ops loopback_ethtool_ops = { 135 .get_link = always_on, 136 .get_ts_info = ethtool_op_get_ts_info, 137 }; 138 139 static int loopback_dev_init(struct net_device *dev) 140 { 141 dev->lstats = netdev_alloc_pcpu_stats(struct pcpu_lstats); 142 if (!dev->lstats) 143 return -ENOMEM; 144 return 0; 145 } 146 147 static void loopback_dev_free(struct net_device *dev) 148 { 149 dev_net(dev)->loopback_dev = NULL; 150 free_percpu(dev->lstats); 151 } 152 153 static const struct net_device_ops loopback_ops = { 154 .ndo_init = loopback_dev_init, 155 .ndo_start_xmit = loopback_xmit, 156 .ndo_get_stats64 = loopback_get_stats64, 157 .ndo_set_mac_address = eth_mac_addr, 158 }; 159 160 static void gen_lo_setup(struct net_device *dev, 161 unsigned int mtu, 162 const struct ethtool_ops *eth_ops, 163 const struct header_ops *hdr_ops, 164 const struct net_device_ops *dev_ops, 165 void (*dev_destructor)(struct net_device *dev)) 166 { 167 dev->mtu = mtu; 168 dev->hard_header_len = ETH_HLEN; /* 14 */ 169 dev->min_header_len = ETH_HLEN; /* 14 */ 170 dev->addr_len = ETH_ALEN; /* 6 */ 171 dev->type = ARPHRD_LOOPBACK; /* 0x0001*/ 172 dev->flags = IFF_LOOPBACK; 173 dev->priv_flags |= IFF_LIVE_ADDR_CHANGE | IFF_NO_QUEUE; 174 netif_keep_dst(dev); 175 dev->hw_features = NETIF_F_GSO_SOFTWARE; 176 dev->features = NETIF_F_SG | NETIF_F_FRAGLIST 177 | NETIF_F_GSO_SOFTWARE 178 | NETIF_F_HW_CSUM 179 | NETIF_F_RXCSUM 180 | NETIF_F_SCTP_CRC 181 | NETIF_F_HIGHDMA 182 | NETIF_F_LLTX 183 | NETIF_F_NETNS_LOCAL 184 | NETIF_F_VLAN_CHALLENGED 185 | NETIF_F_LOOPBACK; 186 dev->ethtool_ops = eth_ops; 187 dev->header_ops = hdr_ops; 188 dev->netdev_ops = dev_ops; 189 dev->needs_free_netdev = true; 190 dev->priv_destructor = dev_destructor; 191 } 192 193 /* The loopback device is special. There is only one instance 194 * per network namespace. 195 */ 196 static void loopback_setup(struct net_device *dev) 197 { 198 gen_lo_setup(dev, (64 * 1024), &loopback_ethtool_ops, ð_header_ops, 199 &loopback_ops, loopback_dev_free); 200 } 201 202 /* Setup and register the loopback device. */ 203 static __net_init int loopback_net_init(struct net *net) 204 { 205 struct net_device *dev; 206 int err; 207 208 err = -ENOMEM; 209 dev = alloc_netdev(0, "lo", NET_NAME_UNKNOWN, loopback_setup); 210 if (!dev) 211 goto out; 212 213 dev_net_set(dev, net); 214 err = register_netdev(dev); 215 if (err) 216 goto out_free_netdev; 217 218 BUG_ON(dev->ifindex != LOOPBACK_IFINDEX); 219 net->loopback_dev = dev; 220 return 0; 221 222 out_free_netdev: 223 free_netdev(dev); 224 out: 225 if (net_eq(net, &init_net)) 226 panic("loopback: Failed to register netdevice: %d\n", err); 227 return err; 228 } 229 230 /* Registered in net/core/dev.c */ 231 struct pernet_operations __net_initdata loopback_net_ops = { 232 .init = loopback_net_init, 233 }; 234 235 /* blackhole netdevice */ 236 static netdev_tx_t blackhole_netdev_xmit(struct sk_buff *skb, 237 struct net_device *dev) 238 { 239 kfree_skb(skb); 240 net_warn_ratelimited("%s(): Dropping skb.\n", __func__); 241 return NETDEV_TX_OK; 242 } 243 244 static const struct net_device_ops blackhole_netdev_ops = { 245 .ndo_start_xmit = blackhole_netdev_xmit, 246 }; 247 248 /* This is a dst-dummy device used specifically for invalidated 249 * DSTs and unlike loopback, this is not per-ns. 250 */ 251 static void blackhole_netdev_setup(struct net_device *dev) 252 { 253 gen_lo_setup(dev, ETH_MIN_MTU, NULL, NULL, &blackhole_netdev_ops, NULL); 254 } 255 256 /* Setup and register the blackhole_netdev. */ 257 static int __init blackhole_netdev_init(void) 258 { 259 blackhole_netdev = alloc_netdev(0, "blackhole_dev", NET_NAME_UNKNOWN, 260 blackhole_netdev_setup); 261 if (!blackhole_netdev) 262 return -ENOMEM; 263 264 rtnl_lock(); 265 dev_init_scheduler(blackhole_netdev); 266 dev_activate(blackhole_netdev); 267 rtnl_unlock(); 268 269 blackhole_netdev->flags |= IFF_UP | IFF_RUNNING; 270 dev_net_set(blackhole_netdev, &init_net); 271 272 return 0; 273 } 274 275 device_initcall(blackhole_netdev_init); 276