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