LXR linux/drivers/net/loopback.c

   1/*
   2 * INET         An implementation of the TCP/IP protocol suite for the LINUX
   3 *              operating system.  INET is implemented using the  BSD Socket
   4 *              interface as the means of communication with the user level.
   5 *
   6 *              Pseudo-driver for the loopback interface.
   7 *
   8 * Version:     @(#)loopback.c  1.0.4b  08/16/93
   9 *
  10 * Authors:     Ross Biro
  11 *              Fred N. van Kempen, <waltje@uWalt.NL.Mugnet.ORG>
  12 *              Donald Becker, <becker@scyld.com>
  13 *
  14 *              Alan Cox        :       Fixed oddments for NET3.014
  15 *              Alan Cox        :       Rejig for NET3.029 snap #3
  16 *              Alan Cox        :       Fixed NET3.029 bugs and sped up
  17 *              Larry McVoy     :       Tiny tweak to double performance
  18 *              Alan Cox        :       Backed out LMV's tweak - the linux mm
  19 *                                      can't take it...
  20 *              Michael Griffith:       Don't bother computing the checksums
  21 *                                      on packets received on the loopback
  22 *                                      interface.
  23 *              Alexey Kuznetsov:       Potential hang under some extreme
  24 *                                      cases removed.
  25 *
  26 *              This program is free software; you can redistribute it and/or
  27 *              modify it under the terms of the GNU General Public License
  28 *              as published by the Free Software Foundation; either version
  29 *              2 of the License, or (at your option) any later version.
  30 */
  31#include <linux/kernel.h>
  32#include <linux/jiffies.h>
  33#include <linux/module.h>
  34#include <linux/interrupt.h>
  35#include <linux/fs.h>
  36#include <linux/types.h>
  37#include <linux/string.h>
  38#include <linux/socket.h>
  39#include <linux/errno.h>
  40#include <linux/fcntl.h>
  41#include <linux/in.h>
  42
  43#include <asm/uaccess.h>
  44#include <asm/io.h>
  45
  46#include <linux/inet.h>
  47#include <linux/netdevice.h>
  48#include <linux/etherdevice.h>
  49#include <linux/skbuff.h>
  50#include <linux/ethtool.h>
  51#include <net/sock.h>
  52#include <net/checksum.h>
  53#include <linux/if_ether.h>     /* For the statistics structure. */
  54#include <linux/if_arp.h>       /* For ARPHRD_ETHER */
  55#include <linux/ip.h>
  56#include <linux/tcp.h>
  57#include <linux/percpu.h>
  58#include <net/net_namespace.h>
  59#include <linux/u64_stats_sync.h>
  60
  61struct pcpu_lstats {
  62        u64                     packets;
  63        u64                     bytes;
  64        struct u64_stats_sync   syncp;
  65};
  66
  67/*
  68 * The higher levels take care of making this non-reentrant (it's
  69 * called with bh's disabled).
  70 */
  71static netdev_tx_t loopback_xmit(struct sk_buff *skb,
  72                                 struct net_device *dev)
  73{
  74        struct pcpu_lstats *lb_stats;
  75        int len;
  76
  77        skb_orphan(skb);
  78
  79        /* Before queueing this packet to netif_rx(),
  80         * make sure dst is refcounted.
  81         */
  82        skb_dst_force(skb);
  83
  84        skb->protocol = eth_type_trans(skb, dev);
  85
  86        /* it's OK to use per_cpu_ptr() because BHs are off */
  87        lb_stats = this_cpu_ptr(dev->lstats);
  88
  89        len = skb->len;
  90        if (likely(netif_rx(skb) == NET_RX_SUCCESS)) {
  91                u64_stats_update_begin(&lb_stats->syncp);
  92                lb_stats->bytes += len;
  93                lb_stats->packets++;
  94                u64_stats_update_end(&lb_stats->syncp);
  95        }
  96
  97        return NETDEV_TX_OK;
  98}
  99
 100static struct rtnl_link_stats64 *loopback_get_stats64(struct net_device *dev,
 101                                                      struct rtnl_link_stats64 *stats)
 102{
 103        u64 bytes = 0;
 104        u64 packets = 0;
 105        int i;
 106
 107        for_each_possible_cpu(i) {
 108                const struct pcpu_lstats *lb_stats;
 109                u64 tbytes, tpackets;
 110                unsigned int start;
 111
 112                lb_stats = per_cpu_ptr(dev->lstats, i);
 113                do {
 114                        start = u64_stats_fetch_begin_irq(&lb_stats->syncp);
 115                        tbytes = lb_stats->bytes;
 116                        tpackets = lb_stats->packets;
 117                } while (u64_stats_fetch_retry_irq(&lb_stats->syncp, start));
 118                bytes   += tbytes;
 119                packets += tpackets;
 120        }
 121        stats->rx_packets = packets;
 122        stats->tx_packets = packets;
 123        stats->rx_bytes   = bytes;
 124        stats->tx_bytes   = bytes;
 125        return stats;
 126}
 127
 128static u32 always_on(struct net_device *dev)
 129{
 130        return 1;
 131}
 132
 133static const struct ethtool_ops loopback_ethtool_ops = {
 134        .get_link               = always_on,
 135};
 136
 137static int loopback_dev_init(struct net_device *dev)
 138{
 139        dev->lstats = netdev_alloc_pcpu_stats(struct pcpu_lstats);
 140        if (!dev->lstats)
 141                return -ENOMEM;
 142        return 0;
 143}
 144
 145static void loopback_dev_free(struct net_device *dev)
 146{
 147        dev_net(dev)->loopback_dev = NULL;
 148        free_percpu(dev->lstats);
 149        free_netdev(dev);
 150}
 151
 152static const struct net_device_ops loopback_ops = {
 153        .ndo_init      = loopback_dev_init,
 154        .ndo_start_xmit= loopback_xmit,
 155        .ndo_get_stats64 = loopback_get_stats64,
 156        .ndo_set_mac_address = eth_mac_addr,
 157};
 158
 159/*
 160 * The loopback device is special. There is only one instance
 161 * per network namespace.
 162 */
 163static void loopback_setup(struct net_device *dev)
 164{
 165        dev->mtu                = 64 * 1024;
 166        dev->hard_header_len    = ETH_HLEN;     /* 14   */
 167        dev->addr_len           = ETH_ALEN;     /* 6    */
 168        dev->type               = ARPHRD_LOOPBACK;      /* 0x0001*/
 169        dev->flags              = IFF_LOOPBACK;
 170        dev->priv_flags         |= IFF_LIVE_ADDR_CHANGE | IFF_NO_QUEUE;
 171        netif_keep_dst(dev);
 172        dev->hw_features        = NETIF_F_GSO_SOFTWARE;
 173        dev->features           = NETIF_F_SG | NETIF_F_FRAGLIST
 174                | NETIF_F_GSO_SOFTWARE
 175                | NETIF_F_HW_CSUM
 176                | NETIF_F_RXCSUM
 177                | NETIF_F_SCTP_CRC
 178                | NETIF_F_HIGHDMA
 179                | NETIF_F_LLTX
 180                | NETIF_F_NETNS_LOCAL
 181                | NETIF_F_VLAN_CHALLENGED
 182                | NETIF_F_LOOPBACK;
 183        dev->ethtool_ops        = &loopback_ethtool_ops;
 184        dev->header_ops         = &eth_header_ops;
 185        dev->netdev_ops         = &loopback_ops;
 186        dev->destructor         = loopback_dev_free;
 187}
 188
 189/* Setup and register the loopback device. */
 190static __net_init int loopback_net_init(struct net *net)
 191{
 192        struct net_device *dev;
 193        int err;
 194
 195        err = -ENOMEM;
 196        dev = alloc_netdev(0, "lo", NET_NAME_UNKNOWN, loopback_setup);
 197        if (!dev)
 198                goto out;
 199
 200        dev_net_set(dev, net);
 201        err = register_netdev(dev);
 202        if (err)
 203                goto out_free_netdev;
 204
 205        BUG_ON(dev->ifindex != LOOPBACK_IFINDEX);
 206        net->loopback_dev = dev;
 207        return 0;
 208
 209
 210out_free_netdev:
 211        free_netdev(dev);
 212out:
 213        if (net_eq(net, &init_net))
 214                panic("loopback: Failed to register netdevice: %d\n", err);
 215        return err;
 216}
 217
 218/* Registered in net/core/dev.c */
 219struct pernet_operations __net_initdata loopback_net_ops = {
 220       .init = loopback_net_init,
 221};
 222