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 62 struct pcpu_lstats { 63 unsigned long packets; 64 unsigned long bytes; 65 unsigned long drops; 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 *pcpu_lstats, *lb_stats; 76 int len; 77 78 skb_orphan(skb); 79 80 skb->protocol = eth_type_trans(skb, dev); 81 82 /* it's OK to use per_cpu_ptr() because BHs are off */ 83 pcpu_lstats = dev->ml_priv; 84 lb_stats = per_cpu_ptr(pcpu_lstats, smp_processor_id()); 85 86 len = skb->len; 87 if (likely(netif_rx(skb) == NET_RX_SUCCESS)) { 88 lb_stats->bytes += len; 89 lb_stats->packets++; 90 } else 91 lb_stats->drops++; 92 93 return NETDEV_TX_OK; 94 } 95 96 static struct net_device_stats *loopback_get_stats(struct net_device *dev) 97 { 98 const struct pcpu_lstats *pcpu_lstats; 99 struct net_device_stats *stats = &dev->stats; 100 unsigned long bytes = 0; 101 unsigned long packets = 0; 102 unsigned long drops = 0; 103 int i; 104 105 pcpu_lstats = dev->ml_priv; 106 for_each_possible_cpu(i) { 107 const struct pcpu_lstats *lb_stats; 108 109 lb_stats = per_cpu_ptr(pcpu_lstats, i); 110 bytes += lb_stats->bytes; 111 packets += lb_stats->packets; 112 drops += lb_stats->drops; 113 } 114 stats->rx_packets = packets; 115 stats->tx_packets = packets; 116 stats->rx_dropped = drops; 117 stats->rx_errors = drops; 118 stats->rx_bytes = bytes; 119 stats->tx_bytes = bytes; 120 return stats; 121 } 122 123 static u32 always_on(struct net_device *dev) 124 { 125 return 1; 126 } 127 128 static const struct ethtool_ops loopback_ethtool_ops = { 129 .get_link = always_on, 130 .set_tso = ethtool_op_set_tso, 131 .get_tx_csum = always_on, 132 .get_sg = always_on, 133 .get_rx_csum = always_on, 134 }; 135 136 static int loopback_dev_init(struct net_device *dev) 137 { 138 struct pcpu_lstats *lstats; 139 140 lstats = alloc_percpu(struct pcpu_lstats); 141 if (!lstats) 142 return -ENOMEM; 143 144 dev->ml_priv = lstats; 145 return 0; 146 } 147 148 static void loopback_dev_free(struct net_device *dev) 149 { 150 struct pcpu_lstats *lstats = dev->ml_priv; 151 152 free_percpu(lstats); 153 free_netdev(dev); 154 } 155 156 static const struct net_device_ops loopback_ops = { 157 .ndo_init = loopback_dev_init, 158 .ndo_start_xmit= loopback_xmit, 159 .ndo_get_stats = loopback_get_stats, 160 }; 161 162 /* 163 * The loopback device is special. There is only one instance 164 * per network namespace. 165 */ 166 static void loopback_setup(struct net_device *dev) 167 { 168 dev->mtu = (16 * 1024) + 20 + 20 + 12; 169 dev->hard_header_len = ETH_HLEN; /* 14 */ 170 dev->addr_len = ETH_ALEN; /* 6 */ 171 dev->tx_queue_len = 0; 172 dev->type = ARPHRD_LOOPBACK; /* 0x0001*/ 173 dev->flags = IFF_LOOPBACK; 174 dev->priv_flags &= ~IFF_XMIT_DST_RELEASE; 175 dev->features = NETIF_F_SG | NETIF_F_FRAGLIST 176 | NETIF_F_TSO 177 | NETIF_F_NO_CSUM 178 | NETIF_F_HIGHDMA 179 | NETIF_F_LLTX 180 | NETIF_F_NETNS_LOCAL; 181 dev->ethtool_ops = &loopback_ethtool_ops; 182 dev->header_ops = ð_header_ops; 183 dev->netdev_ops = &loopback_ops; 184 dev->destructor = loopback_dev_free; 185 } 186 187 /* Setup and register the loopback device. */ 188 static __net_init int loopback_net_init(struct net *net) 189 { 190 struct net_device *dev; 191 int err; 192 193 err = -ENOMEM; 194 dev = alloc_netdev(0, "lo", loopback_setup); 195 if (!dev) 196 goto out; 197 198 dev_net_set(dev, net); 199 err = register_netdev(dev); 200 if (err) 201 goto out_free_netdev; 202 203 net->loopback_dev = dev; 204 return 0; 205 206 207 out_free_netdev: 208 free_netdev(dev); 209 out: 210 if (net == &init_net) 211 panic("loopback: Failed to register netdevice: %d\n", err); 212 return err; 213 } 214 215 static __net_exit void loopback_net_exit(struct net *net) 216 { 217 struct net_device *dev = net->loopback_dev; 218 219 unregister_netdev(dev); 220 } 221 222 /* Registered in net/core/dev.c */ 223 struct pernet_operations __net_initdata loopback_net_ops = { 224 .init = loopback_net_init, 225 .exit = loopback_net_exit, 226 }; 227