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 61struct 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 */ 71static 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 100static 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_irq(&lb_stats->syncp); 115 tbytes = lb_stats->bytes; 116 tpackets = lb_stats->packets; 117 } while (u64_stats_fetch_retry_irq(&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 128static u32 always_on(struct net_device *dev) 129{ 130 return 1; 131} 132 133static const struct ethtool_ops loopback_ethtool_ops = { 134 .get_link = always_on, 135}; 136 137static int loopback_dev_init(struct net_device *dev) 138{ 139 dev->lstats = netdev_alloc_pcpu_stats(struct pcpu_lstats); 140 if (!dev->lstats) 141 return -ENOMEM; 142 return 0; 143} 144 145static void loopback_dev_free(struct net_device *dev) 146{ 147 dev_net(dev)->loopback_dev = NULL; 148 free_percpu(dev->lstats); 149 free_netdev(dev); 150} 151 152static const struct net_device_ops loopback_ops = { 153 .ndo_init = loopback_dev_init, 154 .ndo_start_xmit= loopback_xmit, 155 .ndo_get_stats64 = loopback_get_stats64, 156 .ndo_set_mac_address = eth_mac_addr, 157}; 158 159/* 160 * The loopback device is special. There is only one instance 161 * per network namespace. 162 */ 163static void loopback_setup(struct net_device *dev) 164{ 165 dev->mtu = 64 * 1024; 166 dev->hard_header_len = ETH_HLEN; /* 14 */ 167 dev->addr_len = ETH_ALEN; /* 6 */ 168 dev->tx_queue_len = 0; 169 dev->type = ARPHRD_LOOPBACK; /* 0x0001*/ 170 dev->flags = IFF_LOOPBACK; 171 dev->priv_flags |= IFF_LIVE_ADDR_CHANGE; 172 netif_keep_dst(dev); 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_SCTP_CSUM 180 | NETIF_F_HIGHDMA 181 | NETIF_F_LLTX 182 | NETIF_F_NETNS_LOCAL 183 | NETIF_F_VLAN_CHALLENGED 184 | NETIF_F_LOOPBACK; 185 dev->ethtool_ops = &loopback_ethtool_ops; 186 dev->header_ops = ð_header_ops; 187 dev->netdev_ops = &loopback_ops; 188 dev->destructor = loopback_dev_free; 189} 190 191/* Setup and register the loopback device. */ 192static __net_init int loopback_net_init(struct net *net) 193{ 194 struct net_device *dev; 195 int err; 196 197 err = -ENOMEM; 198 dev = alloc_netdev(0, "lo", NET_NAME_UNKNOWN, loopback_setup); 199 if (!dev) 200 goto out; 201 202 dev_net_set(dev, net); 203 err = register_netdev(dev); 204 if (err) 205 goto out_free_netdev; 206 207 BUG_ON(dev->ifindex != LOOPBACK_IFINDEX); 208 net->loopback_dev = dev; 209 return 0; 210 211 212out_free_netdev: 213 free_netdev(dev); 214out: 215 if (net_eq(net, &init_net)) 216 panic("loopback: Failed to register netdevice: %d\n", err); 217 return err; 218} 219 220/* Registered in net/core/dev.c */ 221struct pernet_operations __net_initdata loopback_net_ops = { 222 .init = loopback_net_init, 223}; 224