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 *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
  96 static 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
 123 static u32 always_on(struct net_device *dev)
 124 {
 125         return 1;
 126 }
 127
 128 static 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
 136 static 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
 148 static 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
 156 static 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  */
 166 static 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. */
 188 static __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
 207 out_free_netdev:
 208         free_netdev(dev);
 209 out:
 210         if (net_eq(net, &init_net))
 211                 panic("loopback: Failed to register netdevice: %d\n", err);
 212         return err;
 213 }
 214
 215 static __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 */
 223 struct pernet_operations __net_initdata loopback_net_ops = {
 224        .init = loopback_net_init,
 225        .exit = loopback_net_exit,
 226 };