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 #ifdef LOOPBACK_TSO
  80         if (skb_is_gso(skb)) {
  81                 BUG_ON(skb->protocol != htons(ETH_P_IP));
  82                 BUG_ON(ip_hdr(skb)->protocol != IPPROTO_TCP);
  83
  84                 emulate_large_send_offload(skb);
  85                 return 0;
  86         }
  87 #endif
  88         dev->last_rx = jiffies;
  89
  90         /* it's OK to use per_cpu_ptr() because BHs are off */
  91         pcpu_lstats = dev->ml_priv;
  92         lb_stats = per_cpu_ptr(pcpu_lstats, smp_processor_id());
  93         lb_stats->bytes += skb->len;
  94         lb_stats->packets++;
  95
  96         netif_rx(skb);
  97
  98         return 0;
  99 }
 100
 101 static struct net_device_stats *get_stats(struct net_device *dev)
 102 {
 103         const struct pcpu_lstats *pcpu_lstats;
 104         struct net_device_stats *stats = &dev->stats;
 105         unsigned long bytes = 0;
 106         unsigned long packets = 0;
 107         int i;
 108
 109         pcpu_lstats = dev->ml_priv;
 110         for_each_possible_cpu(i) {
 111                 const struct pcpu_lstats *lb_stats;
 112
 113                 lb_stats = per_cpu_ptr(pcpu_lstats, i);
 114                 bytes   += lb_stats->bytes;
 115                 packets += lb_stats->packets;
 116         }
 117         stats->rx_packets = packets;
 118         stats->tx_packets = packets;
 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 *lstats;
 140
 141         lstats = alloc_percpu(struct pcpu_lstats);
 142         if (!lstats)
 143                 return -ENOMEM;
 144
 145         dev->ml_priv = lstats;
 146         return 0;
 147 }
 148
 149 static void loopback_dev_free(struct net_device *dev)
 150 {
 151         struct pcpu_lstats *lstats = dev->ml_priv;
 152
 153         free_percpu(lstats);
 154         free_netdev(dev);
 155 }
 156
 157 /*
 158  * The loopback device is special. There is only one instance
 159  * per network namespace.
 160  */
 161 static void loopback_setup(struct net_device *dev)
 162 {
 163         dev->get_stats          = &get_stats;
 164         dev->mtu                = (16 * 1024) + 20 + 20 + 12;
 165         dev->hard_start_xmit    = loopback_xmit;
 166         dev->hard_header_len    = ETH_HLEN;     /* 14   */
 167         dev->addr_len           = ETH_ALEN;     /* 6    */
 168         dev->tx_queue_len       = 0;
 169         dev->type               = ARPHRD_LOOPBACK;      /* 0x0001*/
 170         dev->flags              = IFF_LOOPBACK;
 171         dev->features           = NETIF_F_SG | NETIF_F_FRAGLIST
 172                 | NETIF_F_TSO
 173                 | NETIF_F_NO_CSUM
 174                 | NETIF_F_HIGHDMA
 175                 | NETIF_F_LLTX
 176                 | NETIF_F_NETNS_LOCAL;
 177         dev->ethtool_ops        = &loopback_ethtool_ops;
 178         dev->header_ops         = &eth_header_ops;
 179         dev->init = loopback_dev_init;
 180         dev->destructor = loopback_dev_free;
 181 }
 182
 183 /* Setup and register the loopback device. */
 184 static __net_init int loopback_net_init(struct net *net)
 185 {
 186         struct net_device *dev;
 187         int err;
 188
 189         err = -ENOMEM;
 190         dev = alloc_netdev(0, "lo", loopback_setup);
 191         if (!dev)
 192                 goto out;
 193
 194         dev_net_set(dev, net);
 195         err = register_netdev(dev);
 196         if (err)
 197                 goto out_free_netdev;
 198
 199         net->loopback_dev = dev;
 200         return 0;
 201
 202
 203 out_free_netdev:
 204         free_netdev(dev);
 205 out:
 206         if (net == &init_net)
 207                 panic("loopback: Failed to register netdevice: %d\n", err);
 208         return err;
 209 }
 210
 211 static __net_exit void loopback_net_exit(struct net *net)
 212 {
 213         struct net_device *dev = net->loopback_dev;
 214
 215         unregister_netdev(dev);
 216 }
 217
 218 static struct pernet_operations __net_initdata loopback_net_ops = {
 219        .init = loopback_net_init,
 220        .exit = loopback_net_exit,
 221 };
 222
 223 static int __init loopback_init(void)
 224 {
 225         return register_pernet_device(&loopback_net_ops);
 226 }
 227
 228 /* Loopback is special. It should be initialized before any other network
 229  * device and network subsystem.
 230  */
 231 fs_initcall(loopback_init);