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
  43 #include <asm/uaccess.h>
  44 #include <asm/io.h>
  45
  46 #include <linux/inet.h>
  47 #include <linux/netdevice.h>
  48 #include <linux/etherdevice.h>
  49 #include <linux/skbuff.h>
  50 #include <linux/ethtool.h>
  51 #include <net/sock.h>
  52 #include <net/checksum.h>
  53 #include <linux/if_ether.h>     /* For the statistics structure. */
  54 #include <linux/if_arp.h>       /* For ARPHRD_ETHER */
  55 #include <linux/ip.h>
  56 #include <linux/tcp.h>
  57 #include <linux/percpu.h>
  58 #include <net/net_namespace.h>
  59 #include <linux/u64_stats_sync.h>
  60
  61 struct pcpu_lstats {
  62         u64                     packets;
  63         u64                     bytes;
  64         struct u64_stats_sync   syncp;
  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 netdev_tx_t loopback_xmit(struct sk_buff *skb,
  72                                  struct net_device *dev)
  73 {
  74         struct pcpu_lstats *lb_stats;
  75         int len;
  76
  77         skb_orphan(skb);
  78
  79         /* Before queueing this packet to netif_rx(),
  80          * make sure dst is refcounted.
  81          */
  82         skb_dst_force(skb);
  83
  84         skb->protocol = eth_type_trans(skb, dev);
  85
  86         /* it's OK to use per_cpu_ptr() because BHs are off */
  87         lb_stats = this_cpu_ptr(dev->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         }
  96
  97         return NETDEV_TX_OK;
  98 }
  99
 100 static struct rtnl_link_stats64 *loopback_get_stats64(struct net_device *dev,
 101                                                       struct rtnl_link_stats64 *stats)
 102 {
 103         u64 bytes = 0;
 104         u64 packets = 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_bh(&lb_stats->syncp);
 115                         tbytes = lb_stats->bytes;
 116                         tpackets = lb_stats->packets;
 117                 } while (u64_stats_fetch_retry_bh(&lb_stats->syncp, start));
 118                 bytes   += tbytes;
 119                 packets += tpackets;
 120         }
 121         stats->rx_packets = packets;
 122         stats->tx_packets = packets;
 123         stats->rx_bytes   = bytes;
 124         stats->tx_bytes   = bytes;
 125         return stats;
 126 }
 127
 128 static u32 always_on(struct net_device *dev)
 129 {
 130         return 1;
 131 }
 132
 133 static const struct ethtool_ops loopback_ethtool_ops = {
 134         .get_link               = always_on,
 135 };
 136
 137 static int loopback_dev_init(struct net_device *dev)
 138 {
 139         int i;
 140         dev->lstats = alloc_percpu(struct pcpu_lstats);
 141         if (!dev->lstats)
 142                 return -ENOMEM;
 143
 144         for_each_possible_cpu(i) {
 145                 struct pcpu_lstats *lb_stats;
 146                 lb_stats = per_cpu_ptr(dev->lstats, i);
 147                 u64_stats_init(&lb_stats->syncp);
 148         }
 149         return 0;
 150 }
 151
 152 static void loopback_dev_free(struct net_device *dev)
 153 {
 154         dev_net(dev)->loopback_dev = NULL;
 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                = 64 * 1024;
 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->hw_features        = NETIF_F_ALL_TSO | NETIF_F_UFO;
 179         dev->features           = NETIF_F_SG | NETIF_F_FRAGLIST
 180                 | NETIF_F_ALL_TSO
 181                 | NETIF_F_UFO
 182                 | NETIF_F_HW_CSUM
 183                 | NETIF_F_RXCSUM
 184                 | NETIF_F_HIGHDMA
 185                 | NETIF_F_LLTX
 186                 | NETIF_F_NETNS_LOCAL
 187                 | NETIF_F_VLAN_CHALLENGED
 188                 | NETIF_F_LOOPBACK;
 189         dev->ethtool_ops        = &loopback_ethtool_ops;
 190         dev->header_ops         = &eth_header_ops;
 191         dev->netdev_ops         = &loopback_ops;
 192         dev->destructor         = loopback_dev_free;
 193 }
 194
 195 /* Setup and register the loopback device. */
 196 static __net_init int loopback_net_init(struct net *net)
 197 {
 198         struct net_device *dev;
 199         int err;
 200
 201         err = -ENOMEM;
 202         dev = alloc_netdev(0, "lo", loopback_setup);
 203         if (!dev)
 204                 goto out;
 205
 206         dev_net_set(dev, net);
 207         err = register_netdev(dev);
 208         if (err)
 209                 goto out_free_netdev;
 210
 211         BUG_ON(dev->ifindex != LOOPBACK_IFINDEX);
 212         net->loopback_dev = dev;
 213         return 0;
 214
 215
 216 out_free_netdev:
 217         free_netdev(dev);
 218 out:
 219         if (net_eq(net, &init_net))
 220                 panic("loopback: Failed to register netdevice: %d\n", err);
 221         return err;
 222 }
 223
 224 /* Registered in net/core/dev.c */
 225 struct pernet_operations __net_initdata loopback_net_ops = {
 226        .init = loopback_net_init,
 227 };