LXR linux/drivers/net/loopback.c

   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 */
  62struct net_device *blackhole_netdev;
  63EXPORT_SYMBOL(blackhole_netdev);
  64
  65/* The higher levels take care of making this non-reentrant (it's
  66 * called with bh's disabled).
  67 */
  68static 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
  94void 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}
 116EXPORT_SYMBOL(dev_lstats_read);
 117
 118static 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
 131static u32 always_on(struct net_device *dev)
 132{
 133        return 1;
 134}
 135
 136static const struct ethtool_ops loopback_ethtool_ops = {
 137        .get_link               = always_on,
 138        .get_ts_info            = ethtool_op_get_ts_info,
 139};
 140
 141static 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
 149static void loopback_dev_free(struct net_device *dev)
 150{
 151        dev_net(dev)->loopback_dev = NULL;
 152        free_percpu(dev->lstats);
 153}
 154
 155static 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
 162static 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 */
 198static void loopback_setup(struct net_device *dev)
 199{
 200        gen_lo_setup(dev, (64 * 1024), &loopback_ethtool_ops, &eth_header_ops,
 201                     &loopback_ops, loopback_dev_free);
 202}
 203
 204/* Setup and register the loopback device. */
 205static __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
 224out_free_netdev:
 225        free_netdev(dev);
 226out:
 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 */
 233struct pernet_operations __net_initdata loopback_net_ops = {
 234        .init = loopback_net_init,
 235};
 236
 237/* blackhole netdevice */
 238static 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
 246static 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 */
 253static 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. */
 259static 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
 277device_initcall(blackhole_netdev_init);
 278