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         unsigned long           drops;
  68 };
  69
  70 /*
  71  * The higher levels take care of making this non-reentrant (it's
  72  * called with bh's disabled).
  73  */
  74 static netdev_tx_t loopback_xmit(struct sk_buff *skb,
  75                                  struct net_device *dev)
  76 {
  77         struct pcpu_lstats __percpu *pcpu_lstats;
  78         struct pcpu_lstats *lb_stats;
  79         int len;
  80
  81         skb_orphan(skb);
  82
  83         skb->protocol = eth_type_trans(skb, dev);
  84
  85         /* it's OK to use per_cpu_ptr() because BHs are off */
  86         pcpu_lstats = (void __percpu __force *)dev->ml_priv;
  87         lb_stats = this_cpu_ptr(pcpu_lstats);
  88
  89         len = skb->len;
  90         if (likely(netif_rx(skb) == NET_RX_SUCCESS)) {
  91                 u64_stats_update_begin(&lb_stats->syncp);
  92                 lb_stats->bytes += len;
  93                 lb_stats->packets++;
  94                 u64_stats_update_end(&lb_stats->syncp);
  95         } else
  96                 lb_stats->drops++;
  97
  98         return NETDEV_TX_OK;
  99 }
 100
 101 static struct rtnl_link_stats64 *loopback_get_stats64(struct net_device *dev,
 102                                                       struct rtnl_link_stats64 *stats)
 103 {
 104         const struct pcpu_lstats __percpu *pcpu_lstats;
 105         u64 bytes = 0;
 106         u64 packets = 0;
 107         u64 drops = 0;
 108         int i;
 109
 110         pcpu_lstats = (void __percpu __force *)dev->ml_priv;
 111         for_each_possible_cpu(i) {
 112                 const struct pcpu_lstats *lb_stats;
 113                 u64 tbytes, tpackets;
 114                 unsigned int start;
 115
 116                 lb_stats = per_cpu_ptr(pcpu_lstats, i);
 117                 do {
 118                         start = u64_stats_fetch_begin(&lb_stats->syncp);
 119                         tbytes = lb_stats->bytes;
 120                         tpackets = lb_stats->packets;
 121                 } while (u64_stats_fetch_retry(&lb_stats->syncp, start));
 122                 drops   += lb_stats->drops;
 123                 bytes   += tbytes;
 124                 packets += tpackets;
 125         }
 126         stats->rx_packets = packets;
 127         stats->tx_packets = packets;
 128         stats->rx_dropped = drops;
 129         stats->rx_errors  = drops;
 130         stats->rx_bytes   = bytes;
 131         stats->tx_bytes   = bytes;
 132         return stats;
 133 }
 134
 135 static u32 always_on(struct net_device *dev)
 136 {
 137         return 1;
 138 }
 139
 140 static const struct ethtool_ops loopback_ethtool_ops = {
 141         .get_link               = always_on,
 142         .set_tso                = ethtool_op_set_tso,
 143         .get_tx_csum            = always_on,
 144         .get_sg                 = always_on,
 145         .get_rx_csum            = always_on,
 146 };
 147
 148 static int loopback_dev_init(struct net_device *dev)
 149 {
 150         struct pcpu_lstats __percpu *lstats;
 151
 152         lstats = alloc_percpu(struct pcpu_lstats);
 153         if (!lstats)
 154                 return -ENOMEM;
 155
 156         dev->ml_priv = (void __force *)lstats;
 157         return 0;
 158 }
 159
 160 static void loopback_dev_free(struct net_device *dev)
 161 {
 162         struct pcpu_lstats __percpu *lstats =
 163                 (void __percpu __force *)dev->ml_priv;
 164
 165         free_percpu(lstats);
 166         free_netdev(dev);
 167 }
 168
 169 static const struct net_device_ops loopback_ops = {
 170         .ndo_init      = loopback_dev_init,
 171         .ndo_start_xmit= loopback_xmit,
 172         .ndo_get_stats64 = loopback_get_stats64,
 173 };
 174
 175 /*
 176  * The loopback device is special. There is only one instance
 177  * per network namespace.
 178  */
 179 static void loopback_setup(struct net_device *dev)
 180 {
 181         dev->mtu                = (16 * 1024) + 20 + 20 + 12;
 182         dev->hard_header_len    = ETH_HLEN;     /* 14   */
 183         dev->addr_len           = ETH_ALEN;     /* 6    */
 184         dev->tx_queue_len       = 0;
 185         dev->type               = ARPHRD_LOOPBACK;      /* 0x0001*/
 186         dev->flags              = IFF_LOOPBACK;
 187         dev->priv_flags        &= ~IFF_XMIT_DST_RELEASE;
 188         dev->features           = NETIF_F_SG | NETIF_F_FRAGLIST
 189                 | NETIF_F_TSO
 190                 | NETIF_F_NO_CSUM
 191                 | NETIF_F_HIGHDMA
 192                 | NETIF_F_LLTX
 193                 | NETIF_F_NETNS_LOCAL;
 194         dev->ethtool_ops        = &loopback_ethtool_ops;
 195         dev->header_ops         = &eth_header_ops;
 196         dev->netdev_ops         = &loopback_ops;
 197         dev->destructor         = loopback_dev_free;
 198 }
 199
 200 /* Setup and register the loopback device. */
 201 static __net_init int loopback_net_init(struct net *net)
 202 {
 203         struct net_device *dev;
 204         int err;
 205
 206         err = -ENOMEM;
 207         dev = alloc_netdev(0, "lo", loopback_setup);
 208         if (!dev)
 209                 goto out;
 210
 211         dev_net_set(dev, net);
 212         err = register_netdev(dev);
 213         if (err)
 214                 goto out_free_netdev;
 215
 216         net->loopback_dev = dev;
 217         return 0;
 218
 219
 220 out_free_netdev:
 221         free_netdev(dev);
 222 out:
 223         if (net_eq(net, &init_net))
 224                 panic("loopback: Failed to register netdevice: %d\n", err);
 225         return err;
 226 }
 227
 228 /* Registered in net/core/dev.c */
 229 struct pernet_operations __net_initdata loopback_net_ops = {
 230        .init = loopback_net_init,
 231 };