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 #ifdef LOOPBACK_TSO 80 if (skb_is_gso(skb)) { 81 BUG_ON(skb->protocol != htons(ETH_P_IP)); 82 BUG_ON(ip_hdr(skb)->protocol != IPPROTO_TCP); 83 84 emulate_large_send_offload(skb); 85 return 0; 86 } 87 #endif 88 dev->last_rx = jiffies; 89 90 /* it's OK to use per_cpu_ptr() because BHs are off */ 91 pcpu_lstats = dev->ml_priv; 92 lb_stats = per_cpu_ptr(pcpu_lstats, smp_processor_id()); 93 lb_stats->bytes += skb->len; 94 lb_stats->packets++; 95 96 netif_rx(skb); 97 98 return 0; 99 } 100 101 static struct net_device_stats *get_stats(struct net_device *dev) 102 { 103 const struct pcpu_lstats *pcpu_lstats; 104 struct net_device_stats *stats = &dev->stats; 105 unsigned long bytes = 0; 106 unsigned long packets = 0; 107 int i; 108 109 pcpu_lstats = dev->ml_priv; 110 for_each_possible_cpu(i) { 111 const struct pcpu_lstats *lb_stats; 112 113 lb_stats = per_cpu_ptr(pcpu_lstats, i); 114 bytes += lb_stats->bytes; 115 packets += lb_stats->packets; 116 } 117 stats->rx_packets = packets; 118 stats->tx_packets = packets; 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 *lstats; 140 141 lstats = alloc_percpu(struct pcpu_lstats); 142 if (!lstats) 143 return -ENOMEM; 144 145 dev->ml_priv = lstats; 146 return 0; 147 } 148 149 static void loopback_dev_free(struct net_device *dev) 150 { 151 struct pcpu_lstats *lstats = dev->ml_priv; 152 153 free_percpu(lstats); 154 free_netdev(dev); 155 } 156 157 /* 158 * The loopback device is special. There is only one instance 159 * per network namespace. 160 */ 161 static void loopback_setup(struct net_device *dev) 162 { 163 dev->get_stats = &get_stats; 164 dev->mtu = (16 * 1024) + 20 + 20 + 12; 165 dev->hard_start_xmit = loopback_xmit; 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->features = NETIF_F_SG | NETIF_F_FRAGLIST 172 | NETIF_F_TSO 173 | NETIF_F_NO_CSUM 174 | NETIF_F_HIGHDMA 175 | NETIF_F_LLTX 176 | NETIF_F_NETNS_LOCAL; 177 dev->ethtool_ops = &loopback_ethtool_ops; 178 dev->header_ops = ð_header_ops; 179 dev->init = loopback_dev_init; 180 dev->destructor = loopback_dev_free; 181 } 182 183 /* Setup and register the loopback device. */ 184 static __net_init int loopback_net_init(struct net *net) 185 { 186 struct net_device *dev; 187 int err; 188 189 err = -ENOMEM; 190 dev = alloc_netdev(0, "lo", loopback_setup); 191 if (!dev) 192 goto out; 193 194 dev_net_set(dev, net); 195 err = register_netdev(dev); 196 if (err) 197 goto out_free_netdev; 198 199 net->loopback_dev = dev; 200 return 0; 201 202 203 out_free_netdev: 204 free_netdev(dev); 205 out: 206 if (net == &init_net) 207 panic("loopback: Failed to register netdevice: %d\n", err); 208 return err; 209 } 210 211 static __net_exit void loopback_net_exit(struct net *net) 212 { 213 struct net_device *dev = net->loopback_dev; 214 215 unregister_netdev(dev); 216 } 217 218 static struct pernet_operations __net_initdata loopback_net_ops = { 219 .init = loopback_net_init, 220 .exit = loopback_net_exit, 221 }; 222 223 static int __init loopback_init(void) 224 { 225 return register_pernet_device(&loopback_net_ops); 226 } 227 228 /* Loopback is special. It should be initialized before any other network 229 * device and network subsystem. 230 */ 231 fs_initcall(loopback_init); 232