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 }; 66 67 /* 68 * The higher levels take care of making this non-reentrant (it's 69 * called with bh's disabled). 70 */ 71 static int loopback_xmit(struct sk_buff *skb, struct net_device *dev) 72 { 73 struct pcpu_lstats *pcpu_lstats, *lb_stats; 74 75 skb_orphan(skb); 76 77 skb->protocol = eth_type_trans(skb,dev); 78 79 dev->last_rx = jiffies; 80 81 /* it's OK to use per_cpu_ptr() because BHs are off */ 82 pcpu_lstats = dev->ml_priv; 83 lb_stats = per_cpu_ptr(pcpu_lstats, smp_processor_id()); 84 lb_stats->bytes += skb->len; 85 lb_stats->packets++; 86 87 netif_rx(skb); 88 89 return 0; 90 } 91 92 static struct net_device_stats *get_stats(struct net_device *dev) 93 { 94 const struct pcpu_lstats *pcpu_lstats; 95 struct net_device_stats *stats = &dev->stats; 96 unsigned long bytes = 0; 97 unsigned long packets = 0; 98 int i; 99 100 pcpu_lstats = dev->ml_priv; 101 for_each_possible_cpu(i) { 102 const struct pcpu_lstats *lb_stats; 103 104 lb_stats = per_cpu_ptr(pcpu_lstats, i); 105 bytes += lb_stats->bytes; 106 packets += lb_stats->packets; 107 } 108 stats->rx_packets = packets; 109 stats->tx_packets = packets; 110 stats->rx_bytes = bytes; 111 stats->tx_bytes = bytes; 112 return stats; 113 } 114 115 static u32 always_on(struct net_device *dev) 116 { 117 return 1; 118 } 119 120 static const struct ethtool_ops loopback_ethtool_ops = { 121 .get_link = always_on, 122 .set_tso = ethtool_op_set_tso, 123 .get_tx_csum = always_on, 124 .get_sg = always_on, 125 .get_rx_csum = always_on, 126 }; 127 128 static int loopback_dev_init(struct net_device *dev) 129 { 130 struct pcpu_lstats *lstats; 131 132 lstats = alloc_percpu(struct pcpu_lstats); 133 if (!lstats) 134 return -ENOMEM; 135 136 dev->ml_priv = lstats; 137 return 0; 138 } 139 140 static void loopback_dev_free(struct net_device *dev) 141 { 142 struct pcpu_lstats *lstats = dev->ml_priv; 143 144 free_percpu(lstats); 145 free_netdev(dev); 146 } 147 148 /* 149 * The loopback device is special. There is only one instance 150 * per network namespace. 151 */ 152 static void loopback_setup(struct net_device *dev) 153 { 154 dev->get_stats = &get_stats; 155 dev->mtu = (16 * 1024) + 20 + 20 + 12; 156 dev->hard_start_xmit = loopback_xmit; 157 dev->hard_header_len = ETH_HLEN; /* 14 */ 158 dev->addr_len = ETH_ALEN; /* 6 */ 159 dev->tx_queue_len = 0; 160 dev->type = ARPHRD_LOOPBACK; /* 0x0001*/ 161 dev->flags = IFF_LOOPBACK; 162 dev->features = NETIF_F_SG | NETIF_F_FRAGLIST 163 | NETIF_F_TSO 164 | NETIF_F_NO_CSUM 165 | NETIF_F_HIGHDMA 166 | NETIF_F_LLTX 167 | NETIF_F_NETNS_LOCAL; 168 dev->ethtool_ops = &loopback_ethtool_ops; 169 dev->header_ops = ð_header_ops; 170 dev->init = loopback_dev_init; 171 dev->destructor = loopback_dev_free; 172 } 173 174 /* Setup and register the loopback device. */ 175 static __net_init int loopback_net_init(struct net *net) 176 { 177 struct net_device *dev; 178 int err; 179 180 err = -ENOMEM; 181 dev = alloc_netdev(0, "lo", loopback_setup); 182 if (!dev) 183 goto out; 184 185 dev_net_set(dev, net); 186 err = register_netdev(dev); 187 if (err) 188 goto out_free_netdev; 189 190 net->loopback_dev = dev; 191 return 0; 192 193 194 out_free_netdev: 195 free_netdev(dev); 196 out: 197 if (net == &init_net) 198 panic("loopback: Failed to register netdevice: %d\n", err); 199 return err; 200 } 201 202 static __net_exit void loopback_net_exit(struct net *net) 203 { 204 struct net_device *dev = net->loopback_dev; 205 206 unregister_netdev(dev); 207 } 208 209 static struct pernet_operations __net_initdata loopback_net_ops = { 210 .init = loopback_net_init, 211 .exit = loopback_net_exit, 212 }; 213 214 static int __init loopback_init(void) 215 { 216 return register_pernet_device(&loopback_net_ops); 217 } 218 219 /* Loopback is special. It should be initialized before any other network 220 * device and network subsystem. 221 */ 222 fs_initcall(loopback_init); 223