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 <linux/uaccess.h>
  44 #include <linux/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 <linux/net_tstamp.h>
  59 #include <net/net_namespace.h>
  60 #include <linux/u64_stats_sync.h>
  61
  62 /* The higher levels take care of making this non-reentrant (it's
  63  * called with bh's disabled).
  64  */
  65 static netdev_tx_t loopback_xmit(struct sk_buff *skb,
  66                                  struct net_device *dev)
  67 {
  68         struct pcpu_lstats *lb_stats;
  69         int len;
  70
  71         skb_tx_timestamp(skb);
  72
  73         /* do not fool net_timestamp_check() with various clock bases */
  74         skb->tstamp = 0;
  75
  76         skb_orphan(skb);
  77
  78         /* Before queueing this packet to netif_rx(),
  79          * make sure dst is refcounted.
  80          */
  81         skb_dst_force(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         lb_stats = this_cpu_ptr(dev->lstats);
  87
  88         len = skb->len;
  89         if (likely(netif_rx(skb) == NET_RX_SUCCESS)) {
  90                 u64_stats_update_begin(&lb_stats->syncp);
  91                 lb_stats->bytes += len;
  92                 lb_stats->packets++;
  93                 u64_stats_update_end(&lb_stats->syncp);
  94         }
  95
  96         return NETDEV_TX_OK;
  97 }
  98
  99 static void loopback_get_stats64(struct net_device *dev,
 100                                  struct rtnl_link_stats64 *stats)
 101 {
 102         u64 bytes = 0;
 103         u64 packets = 0;
 104         int i;
 105
 106         for_each_possible_cpu(i) {
 107                 const struct pcpu_lstats *lb_stats;
 108                 u64 tbytes, tpackets;
 109                 unsigned int start;
 110
 111                 lb_stats = per_cpu_ptr(dev->lstats, i);
 112                 do {
 113                         start = u64_stats_fetch_begin_irq(&lb_stats->syncp);
 114                         tbytes = lb_stats->bytes;
 115                         tpackets = lb_stats->packets;
 116                 } while (u64_stats_fetch_retry_irq(&lb_stats->syncp, start));
 117                 bytes   += tbytes;
 118                 packets += tpackets;
 119         }
 120         stats->rx_packets = packets;
 121         stats->tx_packets = packets;
 122         stats->rx_bytes   = bytes;
 123         stats->tx_bytes   = bytes;
 124 }
 125
 126 static u32 always_on(struct net_device *dev)
 127 {
 128         return 1;
 129 }
 130
 131 static const struct ethtool_ops loopback_ethtool_ops = {
 132         .get_link               = always_on,
 133         .get_ts_info            = ethtool_op_get_ts_info,
 134 };
 135
 136 static int loopback_dev_init(struct net_device *dev)
 137 {
 138         dev->lstats = netdev_alloc_pcpu_stats(struct pcpu_lstats);
 139         if (!dev->lstats)
 140                 return -ENOMEM;
 141         return 0;
 142 }
 143
 144 static void loopback_dev_free(struct net_device *dev)
 145 {
 146         dev_net(dev)->loopback_dev = NULL;
 147         free_percpu(dev->lstats);
 148 }
 149
 150 static const struct net_device_ops loopback_ops = {
 151         .ndo_init        = loopback_dev_init,
 152         .ndo_start_xmit  = loopback_xmit,
 153         .ndo_get_stats64 = loopback_get_stats64,
 154         .ndo_set_mac_address = eth_mac_addr,
 155 };
 156
 157 /* The loopback device is special. There is only one instance
 158  * per network namespace.
 159  */
 160 static void loopback_setup(struct net_device *dev)
 161 {
 162         dev->mtu                = 64 * 1024;
 163         dev->hard_header_len    = ETH_HLEN;     /* 14   */
 164         dev->min_header_len     = ETH_HLEN;     /* 14   */
 165         dev->addr_len           = ETH_ALEN;     /* 6    */
 166         dev->type               = ARPHRD_LOOPBACK;      /* 0x0001*/
 167         dev->flags              = IFF_LOOPBACK;
 168         dev->priv_flags         |= IFF_LIVE_ADDR_CHANGE | IFF_NO_QUEUE;
 169         netif_keep_dst(dev);
 170         dev->hw_features        = NETIF_F_GSO_SOFTWARE;
 171         dev->features           = NETIF_F_SG | NETIF_F_FRAGLIST
 172                 | NETIF_F_GSO_SOFTWARE
 173                 | NETIF_F_HW_CSUM
 174                 | NETIF_F_RXCSUM
 175                 | NETIF_F_SCTP_CRC
 176                 | NETIF_F_HIGHDMA
 177                 | NETIF_F_LLTX
 178                 | NETIF_F_NETNS_LOCAL
 179                 | NETIF_F_VLAN_CHALLENGED
 180                 | NETIF_F_LOOPBACK;
 181         dev->ethtool_ops        = &loopback_ethtool_ops;
 182         dev->header_ops         = &eth_header_ops;
 183         dev->netdev_ops         = &loopback_ops;
 184         dev->needs_free_netdev  = true;
 185         dev->priv_destructor    = loopback_dev_free;
 186 }
 187
 188 /* Setup and register the loopback device. */
 189 static __net_init int loopback_net_init(struct net *net)
 190 {
 191         struct net_device *dev;
 192         int err;
 193
 194         err = -ENOMEM;
 195         dev = alloc_netdev(0, "lo", NET_NAME_UNKNOWN, loopback_setup);
 196         if (!dev)
 197                 goto out;
 198
 199         dev_net_set(dev, net);
 200         err = register_netdev(dev);
 201         if (err)
 202                 goto out_free_netdev;
 203
 204         BUG_ON(dev->ifindex != LOOPBACK_IFINDEX);
 205         net->loopback_dev = dev;
 206         return 0;
 207
 208 out_free_netdev:
 209         free_netdev(dev);
 210 out:
 211         if (net_eq(net, &init_net))
 212                 panic("loopback: Failed to register netdevice: %d\n", err);
 213         return err;
 214 }
 215
 216 /* Registered in net/core/dev.c */
 217 struct pernet_operations __net_initdata loopback_net_ops = {
 218         .init = loopback_net_init,
 219 };