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
  62 struct 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  */
  72 static 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
  97 static 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
 124 static u32 always_on(struct net_device *dev)
 125 {
 126         return 1;
 127 }
 128
 129 static 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
 137 static 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
 149 static 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
 158 static 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  */
 168 static 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. */
 190 static __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
 209 out_free_netdev:
 210         free_netdev(dev);
 211 out:
 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 */
 218 struct pernet_operations __net_initdata loopback_net_ops = {
 219        .init = loopback_net_init,
 220 };