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 int len; 72 73 skb_tx_timestamp(skb); 74 75 /* do not fool net_timestamp_check() with various clock bases */ 76 skb->tstamp = 0; 77 78 skb_orphan(skb); 79 80 /* Before queueing this packet to netif_rx(), 81 * make sure dst is refcounted. 82 */ 83 skb_dst_force(skb); 84 85 skb->protocol = eth_type_trans(skb, dev); 86 87 len = skb->len; 88 if (likely(netif_rx(skb) == NET_RX_SUCCESS)) 89 dev_lstats_add(dev, len); 90 91 return NETDEV_TX_OK; 92 } 93 94 void dev_lstats_read(struct net_device *dev, u64 *packets, u64 *bytes) 95 { 96 int i; 97 98 *packets = 0; 99 *bytes = 0; 100 101 for_each_possible_cpu(i) { 102 const struct pcpu_lstats *lb_stats; 103 u64 tbytes, tpackets; 104 unsigned int start; 105 106 lb_stats = per_cpu_ptr(dev->lstats, i); 107 do { 108 start = u64_stats_fetch_begin_irq(&lb_stats->syncp); 109 tpackets = u64_stats_read(&lb_stats->packets); 110 tbytes = u64_stats_read(&lb_stats->bytes); 111 } while (u64_stats_fetch_retry_irq(&lb_stats->syncp, start)); 112 *bytes += tbytes; 113 *packets += tpackets; 114 } 115 } 116 EXPORT_SYMBOL(dev_lstats_read); 117 118 static void loopback_get_stats64(struct net_device *dev, 119 struct rtnl_link_stats64 *stats) 120 { 121 u64 packets, bytes; 122 123 dev_lstats_read(dev, &packets, &bytes); 124 125 stats->rx_packets = packets; 126 stats->tx_packets = packets; 127 stats->rx_bytes = bytes; 128 stats->tx_bytes = bytes; 129 } 130 131 static u32 always_on(struct net_device *dev) 132 { 133 return 1; 134 } 135 136 static const struct ethtool_ops loopback_ethtool_ops = { 137 .get_link = always_on, 138 .get_ts_info = ethtool_op_get_ts_info, 139 }; 140 141 static int loopback_dev_init(struct net_device *dev) 142 { 143 dev->lstats = netdev_alloc_pcpu_stats(struct pcpu_lstats); 144 if (!dev->lstats) 145 return -ENOMEM; 146 return 0; 147 } 148 149 static void loopback_dev_free(struct net_device *dev) 150 { 151 dev_net(dev)->loopback_dev = NULL; 152 free_percpu(dev->lstats); 153 } 154 155 static const struct net_device_ops loopback_ops = { 156 .ndo_init = loopback_dev_init, 157 .ndo_start_xmit = loopback_xmit, 158 .ndo_get_stats64 = loopback_get_stats64, 159 .ndo_set_mac_address = eth_mac_addr, 160 }; 161 162 static void gen_lo_setup(struct net_device *dev, 163 unsigned int mtu, 164 const struct ethtool_ops *eth_ops, 165 const struct header_ops *hdr_ops, 166 const struct net_device_ops *dev_ops, 167 void (*dev_destructor)(struct net_device *dev)) 168 { 169 dev->mtu = mtu; 170 dev->hard_header_len = ETH_HLEN; /* 14 */ 171 dev->min_header_len = ETH_HLEN; /* 14 */ 172 dev->addr_len = ETH_ALEN; /* 6 */ 173 dev->type = ARPHRD_LOOPBACK; /* 0x0001*/ 174 dev->flags = IFF_LOOPBACK; 175 dev->priv_flags |= IFF_LIVE_ADDR_CHANGE | IFF_NO_QUEUE; 176 netif_keep_dst(dev); 177 dev->hw_features = NETIF_F_GSO_SOFTWARE; 178 dev->features = NETIF_F_SG | NETIF_F_FRAGLIST 179 | NETIF_F_GSO_SOFTWARE 180 | NETIF_F_HW_CSUM 181 | NETIF_F_RXCSUM 182 | NETIF_F_SCTP_CRC 183 | NETIF_F_HIGHDMA 184 | NETIF_F_LLTX 185 | NETIF_F_NETNS_LOCAL 186 | NETIF_F_VLAN_CHALLENGED 187 | NETIF_F_LOOPBACK; 188 dev->ethtool_ops = eth_ops; 189 dev->header_ops = hdr_ops; 190 dev->netdev_ops = dev_ops; 191 dev->needs_free_netdev = true; 192 dev->priv_destructor = dev_destructor; 193 } 194 195 /* The loopback device is special. There is only one instance 196 * per network namespace. 197 */ 198 static void loopback_setup(struct net_device *dev) 199 { 200 gen_lo_setup(dev, (64 * 1024), &loopback_ethtool_ops, ð_header_ops, 201 &loopback_ops, loopback_dev_free); 202 } 203 204 /* Setup and register the loopback device. */ 205 static __net_init int loopback_net_init(struct net *net) 206 { 207 struct net_device *dev; 208 int err; 209 210 err = -ENOMEM; 211 dev = alloc_netdev(0, "lo", NET_NAME_UNKNOWN, loopback_setup); 212 if (!dev) 213 goto out; 214 215 dev_net_set(dev, net); 216 err = register_netdev(dev); 217 if (err) 218 goto out_free_netdev; 219 220 BUG_ON(dev->ifindex != LOOPBACK_IFINDEX); 221 net->loopback_dev = dev; 222 return 0; 223 224 out_free_netdev: 225 free_netdev(dev); 226 out: 227 if (net_eq(net, &init_net)) 228 panic("loopback: Failed to register netdevice: %d\n", err); 229 return err; 230 } 231 232 /* Registered in net/core/dev.c */ 233 struct pernet_operations __net_initdata loopback_net_ops = { 234 .init = loopback_net_init, 235 }; 236 237 /* blackhole netdevice */ 238 static netdev_tx_t blackhole_netdev_xmit(struct sk_buff *skb, 239 struct net_device *dev) 240 { 241 kfree_skb(skb); 242 net_warn_ratelimited("%s(): Dropping skb.\n", __func__); 243 return NETDEV_TX_OK; 244 } 245 246 static const struct net_device_ops blackhole_netdev_ops = { 247 .ndo_start_xmit = blackhole_netdev_xmit, 248 }; 249 250 /* This is a dst-dummy device used specifically for invalidated 251 * DSTs and unlike loopback, this is not per-ns. 252 */ 253 static void blackhole_netdev_setup(struct net_device *dev) 254 { 255 gen_lo_setup(dev, ETH_MIN_MTU, NULL, NULL, &blackhole_netdev_ops, NULL); 256 } 257 258 /* Setup and register the blackhole_netdev. */ 259 static int __init blackhole_netdev_init(void) 260 { 261 blackhole_netdev = alloc_netdev(0, "blackhole_dev", NET_NAME_UNKNOWN, 262 blackhole_netdev_setup); 263 if (!blackhole_netdev) 264 return -ENOMEM; 265 266 rtnl_lock(); 267 dev_init_scheduler(blackhole_netdev); 268 dev_activate(blackhole_netdev); 269 rtnl_unlock(); 270 271 blackhole_netdev->flags |= IFF_UP | IFF_RUNNING; 272 dev_net_set(blackhole_netdev, &init_net); 273 274 return 0; 275 } 276 277 device_initcall(blackhole_netdev_init); 278