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 int loopback_xmit(struct sk_buff *skb, struct net_device *dev) 73 { 74 struct pcpu_lstats *pcpu_lstats, *lb_stats; 75 int len; 76 77 skb_orphan(skb); 78 79 skb->protocol = eth_type_trans(skb, dev); 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 85 len = skb->len; 86 if (likely(netif_rx(skb) == NET_RX_SUCCESS)) { 87 lb_stats->bytes += len; 88 lb_stats->packets++; 89 } else 90 lb_stats->drops++; 91 92 return 0; 93 } 94 95 static struct net_device_stats *loopback_get_stats(struct net_device *dev) 96 { 97 const struct pcpu_lstats *pcpu_lstats; 98 struct net_device_stats *stats = &dev->stats; 99 unsigned long bytes = 0; 100 unsigned long packets = 0; 101 unsigned long drops = 0; 102 int i; 103 104 pcpu_lstats = dev->ml_priv; 105 for_each_possible_cpu(i) { 106 const struct pcpu_lstats *lb_stats; 107 108 lb_stats = per_cpu_ptr(pcpu_lstats, i); 109 bytes += lb_stats->bytes; 110 packets += lb_stats->packets; 111 drops += lb_stats->drops; 112 } 113 stats->rx_packets = packets; 114 stats->tx_packets = packets; 115 stats->rx_dropped = drops; 116 stats->rx_errors = drops; 117 stats->rx_bytes = bytes; 118 stats->tx_bytes = bytes; 119 return stats; 120 } 121 122 static u32 always_on(struct net_device *dev) 123 { 124 return 1; 125 } 126 127 static const struct ethtool_ops loopback_ethtool_ops = { 128 .get_link = always_on, 129 .set_tso = ethtool_op_set_tso, 130 .get_tx_csum = always_on, 131 .get_sg = always_on, 132 .get_rx_csum = always_on, 133 }; 134 135 static int loopback_dev_init(struct net_device *dev) 136 { 137 struct pcpu_lstats *lstats; 138 139 lstats = alloc_percpu(struct pcpu_lstats); 140 if (!lstats) 141 return -ENOMEM; 142 143 dev->ml_priv = lstats; 144 return 0; 145 } 146 147 static void loopback_dev_free(struct net_device *dev) 148 { 149 struct pcpu_lstats *lstats = dev->ml_priv; 150 151 free_percpu(lstats); 152 free_netdev(dev); 153 } 154 155 static const struct net_device_ops loopback_ops = { 156 .ndo_init = loopback_dev_init, 157 .ndo_start_xmit= loopback_xmit, 158 .ndo_get_stats = loopback_get_stats, 159 }; 160 161 /* 162 * The loopback device is special. There is only one instance 163 * per network namespace. 164 */ 165 static void loopback_setup(struct net_device *dev) 166 { 167 dev->mtu = (16 * 1024) + 20 + 20 + 12; 168 dev->hard_header_len = ETH_HLEN; /* 14 */ 169 dev->addr_len = ETH_ALEN; /* 6 */ 170 dev->tx_queue_len = 0; 171 dev->type = ARPHRD_LOOPBACK; /* 0x0001*/ 172 dev->flags = IFF_LOOPBACK; 173 dev->priv_flags &= ~IFF_XMIT_DST_RELEASE; 174 dev->features = NETIF_F_SG | NETIF_F_FRAGLIST 175 | NETIF_F_TSO 176 | NETIF_F_NO_CSUM 177 | NETIF_F_HIGHDMA 178 | NETIF_F_LLTX 179 | NETIF_F_NETNS_LOCAL; 180 dev->ethtool_ops = &loopback_ethtool_ops; 181 dev->header_ops = ð_header_ops; 182 dev->netdev_ops = &loopback_ops; 183 dev->destructor = loopback_dev_free; 184 } 185 186 /* Setup and register the loopback device. */ 187 static __net_init int loopback_net_init(struct net *net) 188 { 189 struct net_device *dev; 190 int err; 191 192 err = -ENOMEM; 193 dev = alloc_netdev(0, "lo", loopback_setup); 194 if (!dev) 195 goto out; 196 197 dev_net_set(dev, net); 198 err = register_netdev(dev); 199 if (err) 200 goto out_free_netdev; 201 202 net->loopback_dev = dev; 203 return 0; 204 205 206 out_free_netdev: 207 free_netdev(dev); 208 out: 209 if (net == &init_net) 210 panic("loopback: Failed to register netdevice: %d\n", err); 211 return err; 212 } 213 214 static __net_exit void loopback_net_exit(struct net *net) 215 { 216 struct net_device *dev = net->loopback_dev; 217 218 unregister_netdev(dev); 219 } 220 221 /* Registered in net/core/dev.c */ 222 struct pernet_operations __net_initdata loopback_net_ops = { 223 .init = loopback_net_init, 224 .exit = loopback_net_exit, 225 }; 226