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/uaccess.h>
  45 #include <asm/io.h>
  46
  47 #include <linux/inet.h>
  48 #include <linux/netdevice.h>
  49 #include <linux/etherdevice.h>
  50 #include <linux/skbuff.h>
  51 #include <linux/ethtool.h>
  52 #include <net/sock.h>
  53 #include <net/checksum.h>
  54 #include <linux/if_ether.h>     /* For the statistics structure. */
  55 #include <linux/if_arp.h>       /* For ARPHRD_ETHER */
  56 #include <linux/ip.h>
  57 #include <linux/tcp.h>
  58 #include <linux/percpu.h>
  59 #include <net/net_namespace.h>
  60 #include <linux/u64_stats_sync.h>
  61
  62 struct pcpu_lstats {
  63         u64                     packets;
  64         u64                     bytes;
  65         struct u64_stats_sync   syncp;
  66 };
  67
  68 /*
  69  * The higher levels take care of making this non-reentrant (it's
  70  * called with bh's disabled).
  71  */
  72 static netdev_tx_t loopback_xmit(struct sk_buff *skb,
  73                                  struct net_device *dev)
  74 {
  75         struct pcpu_lstats *lb_stats;
  76         int len;
  77
  78         skb_orphan(skb);
  79
  80         /* Before queueing this packet to netif_rx(),
  81          * make sure dst is refcounted.
  82          */
  83         skb_dst_force(skb);
  84
  85         skb->protocol = eth_type_trans(skb, dev);
  86
  87         /* it's OK to use per_cpu_ptr() because BHs are off */
  88         lb_stats = this_cpu_ptr(dev->lstats);
  89
  90         len = skb->len;
  91         if (likely(netif_rx(skb) == NET_RX_SUCCESS)) {
  92                 u64_stats_update_begin(&lb_stats->syncp);
  93                 lb_stats->bytes += len;
  94                 lb_stats->packets++;
  95                 u64_stats_update_end(&lb_stats->syncp);
  96         }
  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         u64 bytes = 0;
 105         u64 packets = 0;
 106         int i;
 107
 108         for_each_possible_cpu(i) {
 109                 const struct pcpu_lstats *lb_stats;
 110                 u64 tbytes, tpackets;
 111                 unsigned int start;
 112
 113                 lb_stats = per_cpu_ptr(dev->lstats, i);
 114                 do {
 115                         start = u64_stats_fetch_begin_bh(&lb_stats->syncp);
 116                         tbytes = lb_stats->bytes;
 117                         tpackets = lb_stats->packets;
 118                 } while (u64_stats_fetch_retry_bh(&lb_stats->syncp, start));
 119                 bytes   += tbytes;
 120                 packets += tpackets;
 121         }
 122         stats->rx_packets = packets;
 123         stats->tx_packets = packets;
 124         stats->rx_bytes   = bytes;
 125         stats->tx_bytes   = bytes;
 126         return stats;
 127 }
 128
 129 static u32 always_on(struct net_device *dev)
 130 {
 131         return 1;
 132 }
 133
 134 static const struct ethtool_ops loopback_ethtool_ops = {
 135         .get_link               = always_on,
 136 };
 137
 138 static int loopback_dev_init(struct net_device *dev)
 139 {
 140         dev->lstats = alloc_percpu(struct pcpu_lstats);
 141         if (!dev->lstats)
 142                 return -ENOMEM;
 143
 144         return 0;
 145 }
 146
 147 static void loopback_dev_free(struct net_device *dev)
 148 {
 149         dev_net(dev)->loopback_dev = NULL;
 150         free_percpu(dev->lstats);
 151         free_netdev(dev);
 152 }
 153
 154 static const struct net_device_ops loopback_ops = {
 155         .ndo_init      = loopback_dev_init,
 156         .ndo_start_xmit= loopback_xmit,
 157         .ndo_get_stats64 = loopback_get_stats64,
 158 };
 159
 160 /*
 161  * The loopback device is special. There is only one instance
 162  * per network namespace.
 163  */
 164 static void loopback_setup(struct net_device *dev)
 165 {
 166         dev->mtu                = 64 * 1024;
 167         dev->hard_header_len    = ETH_HLEN;     /* 14   */
 168         dev->addr_len           = ETH_ALEN;     /* 6    */
 169         dev->tx_queue_len       = 0;
 170         dev->type               = ARPHRD_LOOPBACK;      /* 0x0001*/
 171         dev->flags              = IFF_LOOPBACK;
 172         dev->priv_flags        &= ~IFF_XMIT_DST_RELEASE;
 173         dev->hw_features        = NETIF_F_ALL_TSO | NETIF_F_UFO;
 174         dev->features           = NETIF_F_SG | NETIF_F_FRAGLIST
 175                 | NETIF_F_ALL_TSO
 176                 | NETIF_F_UFO
 177                 | NETIF_F_HW_CSUM
 178                 | NETIF_F_RXCSUM
 179                 | NETIF_F_HIGHDMA
 180                 | NETIF_F_LLTX
 181                 | NETIF_F_NETNS_LOCAL
 182                 | NETIF_F_VLAN_CHALLENGED
 183                 | NETIF_F_LOOPBACK;
 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         BUG_ON(dev->ifindex != LOOPBACK_IFINDEX);
 207         net->loopback_dev = dev;
 208         return 0;
 209
 210
 211 out_free_netdev:
 212         free_netdev(dev);
 213 out:
 214         if (net_eq(net, &init_net))
 215                 panic("loopback: Failed to register netdevice: %d\n", err);
 216         return err;
 217 }
 218
 219 /* Registered in net/core/dev.c */
 220 struct pernet_operations __net_initdata loopback_net_ops = {
 221        .init = loopback_net_init,
 222 };