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