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#include <linux/init.h>
  43
  44#include <asm/system.h>
  45#include <asm/uaccess.h>
  46#include <asm/io.h>
  47
  48#include <linux/inet.h>
  49#include <linux/netdevice.h>
  50#include <linux/etherdevice.h>
  51#include <linux/skbuff.h>
  52#include <linux/ethtool.h>
  53#include <net/sock.h>
  54#include <net/checksum.h>
  55#include <linux/if_ether.h>     /* For the statistics structure. */
  56#include <linux/if_arp.h>       /* For ARPHRD_ETHER */
  57#include <linux/ip.h>
  58#include <linux/tcp.h>
  59#include <linux/percpu.h>
  60#include <net/net_namespace.h>
  61
  62struct pcpu_lstats {
  63        unsigned long packets;
  64        unsigned long bytes;
  65        unsigned long drops;
  66};
  67
  68/*
  69 * The higher levels take care of making this non-reentrant (it's
  70 * called with bh's disabled).
  71 */
  72static netdev_tx_t loopback_xmit(struct sk_buff *skb,
  73                                 struct net_device *dev)
  74{
  75        struct pcpu_lstats *pcpu_lstats, *lb_stats;
  76        int len;
  77
  78        skb_orphan(skb);
  79
  80        skb->protocol = eth_type_trans(skb, dev);
  81
  82        /* it's OK to use per_cpu_ptr() because BHs are off */
  83        pcpu_lstats = dev->ml_priv;
  84        lb_stats = per_cpu_ptr(pcpu_lstats, smp_processor_id());
  85
  86        len = skb->len;
  87        if (likely(netif_rx(skb) == NET_RX_SUCCESS)) {
  88                lb_stats->bytes += len;
  89                lb_stats->packets++;
  90        } else
  91                lb_stats->drops++;
  92
  93        return NETDEV_TX_OK;
  94}
  95
  96static struct net_device_stats *loopback_get_stats(struct net_device *dev)
  97{
  98        const struct pcpu_lstats *pcpu_lstats;
  99        struct net_device_stats *stats = &dev->stats;
 100        unsigned long bytes = 0;
 101        unsigned long packets = 0;
 102        unsigned long drops = 0;
 103        int i;
 104
 105        pcpu_lstats = dev->ml_priv;
 106        for_each_possible_cpu(i) {
 107                const struct pcpu_lstats *lb_stats;
 108
 109                lb_stats = per_cpu_ptr(pcpu_lstats, i);
 110                bytes   += lb_stats->bytes;
 111                packets += lb_stats->packets;
 112                drops   += lb_stats->drops;
 113        }
 114        stats->rx_packets = packets;
 115        stats->tx_packets = packets;
 116        stats->rx_dropped = drops;
 117        stats->rx_errors  = drops;
 118        stats->rx_bytes   = bytes;
 119        stats->tx_bytes   = bytes;
 120        return stats;
 121}
 122
 123static u32 always_on(struct net_device *dev)
 124{
 125        return 1;
 126}
 127
 128static const struct ethtool_ops loopback_ethtool_ops = {
 129        .get_link               = always_on,
 130        .set_tso                = ethtool_op_set_tso,
 131        .get_tx_csum            = always_on,
 132        .get_sg                 = always_on,
 133        .get_rx_csum            = always_on,
 134};
 135
 136static int loopback_dev_init(struct net_device *dev)
 137{
 138        struct pcpu_lstats *lstats;
 139
 140        lstats = alloc_percpu(struct pcpu_lstats);
 141        if (!lstats)
 142                return -ENOMEM;
 143
 144        dev->ml_priv = lstats;
 145        return 0;
 146}
 147
 148static void loopback_dev_free(struct net_device *dev)
 149{
 150        struct pcpu_lstats *lstats = dev->ml_priv;
 151
 152        free_percpu(lstats);
 153        free_netdev(dev);
 154}
 155
 156static const struct net_device_ops loopback_ops = {
 157        .ndo_init      = loopback_dev_init,
 158        .ndo_start_xmit= loopback_xmit,
 159        .ndo_get_stats = loopback_get_stats,
 160};
 161
 162/*
 163 * The loopback device is special. There is only one instance
 164 * per network namespace.
 165 */
 166static void loopback_setup(struct net_device *dev)
 167{
 168        dev->mtu                = (16 * 1024) + 20 + 20 + 12;
 169        dev->hard_header_len    = ETH_HLEN;     /* 14   */
 170        dev->addr_len           = ETH_ALEN;     /* 6    */
 171        dev->tx_queue_len       = 0;
 172        dev->type               = ARPHRD_LOOPBACK;      /* 0x0001*/
 173        dev->flags              = IFF_LOOPBACK;
 174        dev->priv_flags        &= ~IFF_XMIT_DST_RELEASE;
 175        dev->features           = NETIF_F_SG | NETIF_F_FRAGLIST
 176                | NETIF_F_TSO
 177                | NETIF_F_NO_CSUM
 178                | NETIF_F_HIGHDMA
 179                | NETIF_F_LLTX
 180                | NETIF_F_NETNS_LOCAL;
 181        dev->ethtool_ops        = &loopback_ethtool_ops;
 182        dev->header_ops         = &eth_header_ops;
 183        dev->netdev_ops         = &loopback_ops;
 184        dev->destructor         = loopback_dev_free;
 185}
 186
 187/* Setup and register the loopback device. */
 188static __net_init int loopback_net_init(struct net *net)
 189{
 190        struct net_device *dev;
 191        int err;
 192
 193        err = -ENOMEM;
 194        dev = alloc_netdev(0, "lo", loopback_setup);
 195        if (!dev)
 196                goto out;
 197
 198        dev_net_set(dev, net);
 199        err = register_netdev(dev);
 200        if (err)
 201                goto out_free_netdev;
 202
 203        net->loopback_dev = dev;
 204        return 0;
 205
 206
 207out_free_netdev:
 208        free_netdev(dev);
 209out:
 210        if (net == &init_net)
 211                panic("loopback: Failed to register netdevice: %d\n", err);
 212        return err;
 213}
 214
 215static __net_exit void loopback_net_exit(struct net *net)
 216{
 217        struct net_device *dev = net->loopback_dev;
 218
 219        unregister_netdev(dev);
 220}
 221
 222/* Registered in net/core/dev.c */
 223struct pernet_operations __net_initdata loopback_net_ops = {
 224       .init = loopback_net_init,
 225       .exit = loopback_net_exit,
 226};
 227