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 };
  66
  67 /*
  68  * The higher levels take care of making this non-reentrant (it's
  69  * called with bh's disabled).
  70  */
  71 static int loopback_xmit(struct sk_buff *skb, struct net_device *dev)
  72 {
  73         struct pcpu_lstats *pcpu_lstats, *lb_stats;
  74
  75         skb_orphan(skb);
  76
  77         skb->protocol = eth_type_trans(skb,dev);
  78
  79         dev->last_rx = jiffies;
  80
  81         /* it's OK to use per_cpu_ptr() because BHs are off */
  82         pcpu_lstats = dev->ml_priv;
  83         lb_stats = per_cpu_ptr(pcpu_lstats, smp_processor_id());
  84         lb_stats->bytes += skb->len;
  85         lb_stats->packets++;
  86
  87         netif_rx(skb);
  88
  89         return 0;
  90 }
  91
  92 static struct net_device_stats *get_stats(struct net_device *dev)
  93 {
  94         const struct pcpu_lstats *pcpu_lstats;
  95         struct net_device_stats *stats = &dev->stats;
  96         unsigned long bytes = 0;
  97         unsigned long packets = 0;
  98         int i;
  99
 100         pcpu_lstats = dev->ml_priv;
 101         for_each_possible_cpu(i) {
 102                 const struct pcpu_lstats *lb_stats;
 103
 104                 lb_stats = per_cpu_ptr(pcpu_lstats, i);
 105                 bytes   += lb_stats->bytes;
 106                 packets += lb_stats->packets;
 107         }
 108         stats->rx_packets = packets;
 109         stats->tx_packets = packets;
 110         stats->rx_bytes = bytes;
 111         stats->tx_bytes = bytes;
 112         return stats;
 113 }
 114
 115 static u32 always_on(struct net_device *dev)
 116 {
 117         return 1;
 118 }
 119
 120 static const struct ethtool_ops loopback_ethtool_ops = {
 121         .get_link               = always_on,
 122         .set_tso                = ethtool_op_set_tso,
 123         .get_tx_csum            = always_on,
 124         .get_sg                 = always_on,
 125         .get_rx_csum            = always_on,
 126 };
 127
 128 static int loopback_dev_init(struct net_device *dev)
 129 {
 130         struct pcpu_lstats *lstats;
 131
 132         lstats = alloc_percpu(struct pcpu_lstats);
 133         if (!lstats)
 134                 return -ENOMEM;
 135
 136         dev->ml_priv = lstats;
 137         return 0;
 138 }
 139
 140 static void loopback_dev_free(struct net_device *dev)
 141 {
 142         struct pcpu_lstats *lstats = dev->ml_priv;
 143
 144         free_percpu(lstats);
 145         free_netdev(dev);
 146 }
 147
 148 /*
 149  * The loopback device is special. There is only one instance
 150  * per network namespace.
 151  */
 152 static void loopback_setup(struct net_device *dev)
 153 {
 154         dev->get_stats          = &get_stats;
 155         dev->mtu                = (16 * 1024) + 20 + 20 + 12;
 156         dev->hard_start_xmit    = loopback_xmit;
 157         dev->hard_header_len    = ETH_HLEN;     /* 14   */
 158         dev->addr_len           = ETH_ALEN;     /* 6    */
 159         dev->tx_queue_len       = 0;
 160         dev->type               = ARPHRD_LOOPBACK;      /* 0x0001*/
 161         dev->flags              = IFF_LOOPBACK;
 162         dev->features           = NETIF_F_SG | NETIF_F_FRAGLIST
 163                 | NETIF_F_TSO
 164                 | NETIF_F_NO_CSUM
 165                 | NETIF_F_HIGHDMA
 166                 | NETIF_F_LLTX
 167                 | NETIF_F_NETNS_LOCAL;
 168         dev->ethtool_ops        = &loopback_ethtool_ops;
 169         dev->header_ops         = &eth_header_ops;
 170         dev->init = loopback_dev_init;
 171         dev->destructor = loopback_dev_free;
 172 }
 173
 174 /* Setup and register the loopback device. */
 175 static __net_init int loopback_net_init(struct net *net)
 176 {
 177         struct net_device *dev;
 178         int err;
 179
 180         err = -ENOMEM;
 181         dev = alloc_netdev(0, "lo", loopback_setup);
 182         if (!dev)
 183                 goto out;
 184
 185         dev_net_set(dev, net);
 186         err = register_netdev(dev);
 187         if (err)
 188                 goto out_free_netdev;
 189
 190         net->loopback_dev = dev;
 191         return 0;
 192
 193
 194 out_free_netdev:
 195         free_netdev(dev);
 196 out:
 197         if (net == &init_net)
 198                 panic("loopback: Failed to register netdevice: %d\n", err);
 199         return err;
 200 }
 201
 202 static __net_exit void loopback_net_exit(struct net *net)
 203 {
 204         struct net_device *dev = net->loopback_dev;
 205
 206         unregister_netdev(dev);
 207 }
 208
 209 static struct pernet_operations __net_initdata loopback_net_ops = {
 210        .init = loopback_net_init,
 211        .exit = loopback_net_exit,
 212 };
 213
 214 static int __init loopback_init(void)
 215 {
 216         return register_pernet_device(&loopback_net_ops);
 217 }
 218
 219 /* Loopback is special. It should be initialized before any other network
 220  * device and network subsystem.
 221  */
 222 fs_initcall(loopback_init);