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 __percpu *pcpu_lstats;
  76        struct pcpu_lstats *lb_stats;
  77        int len;
  78
  79        skb_orphan(skb);
  80
  81        skb->protocol = eth_type_trans(skb, dev);
  82
  83        /* it's OK to use per_cpu_ptr() because BHs are off */
  84        pcpu_lstats = (void __percpu __force *)dev->ml_priv;
  85        lb_stats = this_cpu_ptr(pcpu_lstats);
  86
  87        len = skb->len;
  88        if (likely(netif_rx(skb) == NET_RX_SUCCESS)) {
  89                lb_stats->bytes += len;
  90                lb_stats->packets++;
  91        } else
  92                lb_stats->drops++;
  93
  94        return NETDEV_TX_OK;
  95}
  96
  97static struct net_device_stats *loopback_get_stats(struct net_device *dev)
  98{
  99        const struct pcpu_lstats __percpu *pcpu_lstats;
 100        struct net_device_stats *stats = &dev->stats;
 101        unsigned long bytes = 0;
 102        unsigned long packets = 0;
 103        unsigned long drops = 0;
 104        int i;
 105
 106        pcpu_lstats = (void __percpu __force *)dev->ml_priv;
 107        for_each_possible_cpu(i) {
 108                const struct pcpu_lstats *lb_stats;
 109
 110                lb_stats = per_cpu_ptr(pcpu_lstats, i);
 111                bytes   += lb_stats->bytes;
 112                packets += lb_stats->packets;
 113                drops   += lb_stats->drops;
 114        }
 115        stats->rx_packets = packets;
 116        stats->tx_packets = packets;
 117        stats->rx_dropped = drops;
 118        stats->rx_errors  = drops;
 119        stats->rx_bytes   = bytes;
 120        stats->tx_bytes   = bytes;
 121        return stats;
 122}
 123
 124static u32 always_on(struct net_device *dev)
 125{
 126        return 1;
 127}
 128
 129static const struct ethtool_ops loopback_ethtool_ops = {
 130        .get_link               = always_on,
 131        .set_tso                = ethtool_op_set_tso,
 132        .get_tx_csum            = always_on,
 133        .get_sg                 = always_on,
 134        .get_rx_csum            = always_on,
 135};
 136
 137static int loopback_dev_init(struct net_device *dev)
 138{
 139        struct pcpu_lstats __percpu *lstats;
 140
 141        lstats = alloc_percpu(struct pcpu_lstats);
 142        if (!lstats)
 143                return -ENOMEM;
 144
 145        dev->ml_priv = (void __force *)lstats;
 146        return 0;
 147}
 148
 149static void loopback_dev_free(struct net_device *dev)
 150{
 151        struct pcpu_lstats __percpu *lstats =
 152                (void __percpu __force *)dev->ml_priv;
 153
 154        free_percpu(lstats);
 155        free_netdev(dev);
 156}
 157
 158static const struct net_device_ops loopback_ops = {
 159        .ndo_init      = loopback_dev_init,
 160        .ndo_start_xmit= loopback_xmit,
 161        .ndo_get_stats = loopback_get_stats,
 162};
 163
 164/*
 165 * The loopback device is special. There is only one instance
 166 * per network namespace.
 167 */
 168static void loopback_setup(struct net_device *dev)
 169{
 170        dev->mtu                = (16 * 1024) + 20 + 20 + 12;
 171        dev->hard_header_len    = ETH_HLEN;     /* 14   */
 172        dev->addr_len           = ETH_ALEN;     /* 6    */
 173        dev->tx_queue_len       = 0;
 174        dev->type               = ARPHRD_LOOPBACK;      /* 0x0001*/
 175        dev->flags              = IFF_LOOPBACK;
 176        dev->priv_flags        &= ~IFF_XMIT_DST_RELEASE;
 177        dev->features           = NETIF_F_SG | NETIF_F_FRAGLIST
 178                | NETIF_F_TSO
 179                | NETIF_F_NO_CSUM
 180                | NETIF_F_HIGHDMA
 181                | NETIF_F_LLTX
 182                | NETIF_F_NETNS_LOCAL;
 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", 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        net->loopback_dev = dev;
 206        return 0;
 207
 208
 209out_free_netdev:
 210        free_netdev(dev);
 211out:
 212        if (net_eq(net, &init_net))
 213                panic("loopback: Failed to register netdevice: %d\n", err);
 214        return err;
 215}
 216
 217/* Registered in net/core/dev.c */
 218struct pernet_operations __net_initdata loopback_net_ops = {
 219       .init = loopback_net_init,
 220};
 221