| 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_clear_tstamp(skb); |
| 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(&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(&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 | netif_set_tso_max_size(dev, GSO_MAX_SIZE); |
| 196 | } |
| 197 | |
| 198 | /* The loopback device is special. There is only one instance |
| 199 | * per network namespace. |
| 200 | */ |
| 201 | static void loopback_setup(struct net_device *dev) |
| 202 | { |
| 203 | gen_lo_setup(dev, (64 * 1024), &loopback_ethtool_ops, ð_header_ops, |
| 204 | &loopback_ops, loopback_dev_free); |
| 205 | } |
| 206 | |
| 207 | /* Setup and register the loopback device. */ |
| 208 | static __net_init int loopback_net_init(struct net *net) |
| 209 | { |
| 210 | struct net_device *dev; |
| 211 | int err; |
| 212 | |
| 213 | err = -ENOMEM; |
| 214 | dev = alloc_netdev(0, "lo", NET_NAME_PREDICTABLE, loopback_setup); |
| 215 | if (!dev) |
| 216 | goto out; |
| 217 | |
| 218 | dev_net_set(dev, net); |
| 219 | err = register_netdev(dev); |
| 220 | if (err) |
| 221 | goto out_free_netdev; |
| 222 | |
| 223 | BUG_ON(dev->ifindex != LOOPBACK_IFINDEX); |
| 224 | net->loopback_dev = dev; |
| 225 | return 0; |
| 226 | |
| 227 | out_free_netdev: |
| 228 | free_netdev(dev); |
| 229 | out: |
| 230 | if (net_eq(net, &init_net)) |
| 231 | panic("loopback: Failed to register netdevice: %d\n", err); |
| 232 | return err; |
| 233 | } |
| 234 | |
| 235 | /* Registered in net/core/dev.c */ |
| 236 | struct pernet_operations __net_initdata loopback_net_ops = { |
| 237 | .init = loopback_net_init, |
| 238 | }; |
| 239 | |
| 240 | /* blackhole netdevice */ |
| 241 | static netdev_tx_t blackhole_netdev_xmit(struct sk_buff *skb, |
| 242 | struct net_device *dev) |
| 243 | { |
| 244 | kfree_skb(skb); |
| 245 | net_warn_ratelimited("%s(): Dropping skb.\n", __func__); |
| 246 | return NETDEV_TX_OK; |
| 247 | } |
| 248 | |
| 249 | static const struct net_device_ops blackhole_netdev_ops = { |
| 250 | .ndo_start_xmit = blackhole_netdev_xmit, |
| 251 | }; |
| 252 | |
| 253 | /* This is a dst-dummy device used specifically for invalidated |
| 254 | * DSTs and unlike loopback, this is not per-ns. |
| 255 | */ |
| 256 | static void blackhole_netdev_setup(struct net_device *dev) |
| 257 | { |
| 258 | gen_lo_setup(dev, ETH_MIN_MTU, NULL, NULL, &blackhole_netdev_ops, NULL); |
| 259 | } |
| 260 | |
| 261 | /* Setup and register the blackhole_netdev. */ |
| 262 | static int __init blackhole_netdev_init(void) |
| 263 | { |
| 264 | blackhole_netdev = alloc_netdev(0, "blackhole_dev", NET_NAME_UNKNOWN, |
| 265 | blackhole_netdev_setup); |
| 266 | if (!blackhole_netdev) |
| 267 | return -ENOMEM; |
| 268 | |
| 269 | rtnl_lock(); |
| 270 | dev_init_scheduler(blackhole_netdev); |
| 271 | dev_activate(blackhole_netdev); |
| 272 | rtnl_unlock(); |
| 273 | |
| 274 | blackhole_netdev->flags |= IFF_UP | IFF_RUNNING; |
| 275 | dev_net_set(blackhole_netdev, &init_net); |
| 276 | |
| 277 | return 0; |
| 278 | } |
| 279 | |
| 280 | device_initcall(blackhole_netdev_init); |