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 #include <linux/u64_stats_sync.h>
  62
  63 struct pcpu_lstats {
  64         u64                     packets;
  65         u64                     bytes;
  66         struct u64_stats_sync   syncp;
  67 };
  68
  69 /*
  70  * The higher levels take care of making this non-reentrant (it's
  71  * called with bh's disabled).
  72  */
  73 static netdev_tx_t loopback_xmit(struct sk_buff *skb,
  74                                  struct net_device *dev)
  75 {
  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         lb_stats = this_cpu_ptr(dev->lstats);
  85
  86         len = skb->len;
  87         if (likely(netif_rx(skb) == NET_RX_SUCCESS)) {
  88                 u64_stats_update_begin(&lb_stats->syncp);
  89                 lb_stats->bytes += len;
  90                 lb_stats->packets++;
  91                 u64_stats_update_end(&lb_stats->syncp);
  92         }
  93
  94         return NETDEV_TX_OK;
  95 }
  96
  97 static struct rtnl_link_stats64 *loopback_get_stats64(struct net_device *dev,
  98                                                       struct rtnl_link_stats64 *stats)
  99 {
 100         u64 bytes = 0;
 101         u64 packets = 0;
 102         int i;
 103
 104         for_each_possible_cpu(i) {
 105                 const struct pcpu_lstats *lb_stats;
 106                 u64 tbytes, tpackets;
 107                 unsigned int start;
 108
 109                 lb_stats = per_cpu_ptr(dev->lstats, i);
 110                 do {
 111                         start = u64_stats_fetch_begin(&lb_stats->syncp);
 112                         tbytes = lb_stats->bytes;
 113                         tpackets = lb_stats->packets;
 114                 } while (u64_stats_fetch_retry(&lb_stats->syncp, start));
 115                 bytes   += tbytes;
 116                 packets += tpackets;
 117         }
 118         stats->rx_packets = packets;
 119         stats->tx_packets = packets;
 120         stats->rx_bytes   = bytes;
 121         stats->tx_bytes   = bytes;
 122         return stats;
 123 }
 124
 125 static u32 always_on(struct net_device *dev)
 126 {
 127         return 1;
 128 }
 129
 130 static const struct ethtool_ops loopback_ethtool_ops = {
 131         .get_link               = always_on,
 132 };
 133
 134 static int loopback_dev_init(struct net_device *dev)
 135 {
 136         dev->lstats = alloc_percpu(struct pcpu_lstats);
 137         if (!dev->lstats)
 138                 return -ENOMEM;
 139
 140         return 0;
 141 }
 142
 143 static void loopback_dev_free(struct net_device *dev)
 144 {
 145         free_percpu(dev->lstats);
 146         free_netdev(dev);
 147 }
 148
 149 static const struct net_device_ops loopback_ops = {
 150         .ndo_init      = loopback_dev_init,
 151         .ndo_start_xmit= loopback_xmit,
 152         .ndo_get_stats64 = loopback_get_stats64,
 153 };
 154
 155 /*
 156  * The loopback device is special. There is only one instance
 157  * per network namespace.
 158  */
 159 static void loopback_setup(struct net_device *dev)
 160 {
 161         dev->mtu                = (16 * 1024) + 20 + 20 + 12;
 162         dev->hard_header_len    = ETH_HLEN;     /* 14   */
 163         dev->addr_len           = ETH_ALEN;     /* 6    */
 164         dev->tx_queue_len       = 0;
 165         dev->type               = ARPHRD_LOOPBACK;      /* 0x0001*/
 166         dev->flags              = IFF_LOOPBACK;
 167         dev->priv_flags        &= ~IFF_XMIT_DST_RELEASE;
 168         dev->hw_features        = NETIF_F_ALL_TSO | NETIF_F_UFO;
 169         dev->features           = NETIF_F_SG | NETIF_F_FRAGLIST
 170                 | NETIF_F_ALL_TSO
 171                 | NETIF_F_UFO
 172                 | NETIF_F_NO_CSUM
 173                 | NETIF_F_RXCSUM
 174                 | NETIF_F_HIGHDMA
 175                 | NETIF_F_LLTX
 176                 | NETIF_F_NETNS_LOCAL
 177                 | NETIF_F_VLAN_CHALLENGED
 178                 | NETIF_F_LOOPBACK;
 179         dev->ethtool_ops        = &loopback_ethtool_ops;
 180         dev->header_ops         = &eth_header_ops;
 181         dev->netdev_ops         = &loopback_ops;
 182         dev->destructor         = loopback_dev_free;
 183 }
 184
 185 /* Setup and register the loopback device. */
 186 static __net_init int loopback_net_init(struct net *net)
 187 {
 188         struct net_device *dev;
 189         int err;
 190
 191         err = -ENOMEM;
 192         dev = alloc_netdev(0, "lo", loopback_setup);
 193         if (!dev)
 194                 goto out;
 195
 196         dev_net_set(dev, net);
 197         err = register_netdev(dev);
 198         if (err)
 199                 goto out_free_netdev;
 200
 201         net->loopback_dev = dev;
 202         return 0;
 203
 204
 205 out_free_netdev:
 206         free_netdev(dev);
 207 out:
 208         if (net_eq(net, &init_net))
 209                 panic("loopback: Failed to register netdevice: %d\n", err);
 210         return err;
 211 }
 212
 213 /* Registered in net/core/dev.c */
 214 struct pernet_operations __net_initdata loopback_net_ops = {
 215        .init = loopback_net_init,
 216 };