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 u64 packets; 64 u64 bytes; 65 #if BITS_PER_LONG==32 && defined(CONFIG_SMP) 66 seqcount_t seq; 67 #endif 68 unsigned long drops; 69 }; 70 71 #if BITS_PER_LONG==32 && defined(CONFIG_SMP) 72 static void inline lstats_update_begin(struct pcpu_lstats *lstats) 73 { 74 write_seqcount_begin(&lstats->seq); 75 } 76 static void inline lstats_update_end(struct pcpu_lstats *lstats) 77 { 78 write_seqcount_end(&lstats->seq); 79 } 80 static void inline lstats_fetch_and_add(u64 *packets, u64 *bytes, const struct pcpu_lstats *lstats) 81 { 82 u64 tpackets, tbytes; 83 unsigned int seq; 84 85 do { 86 seq = read_seqcount_begin(&lstats->seq); 87 tpackets = lstats->packets; 88 tbytes = lstats->bytes; 89 } while (read_seqcount_retry(&lstats->seq, seq)); 90 91 *packets += tpackets; 92 *bytes += tbytes; 93 } 94 #else 95 static void inline lstats_update_begin(struct pcpu_lstats *lstats) 96 { 97 } 98 static void inline lstats_update_end(struct pcpu_lstats *lstats) 99 { 100 } 101 static void inline lstats_fetch_and_add(u64 *packets, u64 *bytes, const struct pcpu_lstats *lstats) 102 { 103 *packets += lstats->packets; 104 *bytes += lstats->bytes; 105 } 106 #endif 107 108 /* 109 * The higher levels take care of making this non-reentrant (it's 110 * called with bh's disabled). 111 */ 112 static netdev_tx_t loopback_xmit(struct sk_buff *skb, 113 struct net_device *dev) 114 { 115 struct pcpu_lstats __percpu *pcpu_lstats; 116 struct pcpu_lstats *lb_stats; 117 int len; 118 119 skb_orphan(skb); 120 121 skb->protocol = eth_type_trans(skb, dev); 122 123 /* it's OK to use per_cpu_ptr() because BHs are off */ 124 pcpu_lstats = (void __percpu __force *)dev->ml_priv; 125 lb_stats = this_cpu_ptr(pcpu_lstats); 126 127 len = skb->len; 128 if (likely(netif_rx(skb) == NET_RX_SUCCESS)) { 129 lstats_update_begin(lb_stats); 130 lb_stats->bytes += len; 131 lb_stats->packets++; 132 lstats_update_end(lb_stats); 133 } else 134 lb_stats->drops++; 135 136 return NETDEV_TX_OK; 137 } 138 139 static struct rtnl_link_stats64 *loopback_get_stats64(struct net_device *dev) 140 { 141 const struct pcpu_lstats __percpu *pcpu_lstats; 142 struct rtnl_link_stats64 *stats = &dev->stats64; 143 u64 bytes = 0; 144 u64 packets = 0; 145 u64 drops = 0; 146 int i; 147 148 pcpu_lstats = (void __percpu __force *)dev->ml_priv; 149 for_each_possible_cpu(i) { 150 const struct pcpu_lstats *lb_stats; 151 152 lb_stats = per_cpu_ptr(pcpu_lstats, i); 153 lstats_fetch_and_add(&packets, &bytes, lb_stats); 154 drops += lb_stats->drops; 155 } 156 stats->rx_packets = packets; 157 stats->tx_packets = packets; 158 stats->rx_dropped = drops; 159 stats->rx_errors = drops; 160 stats->rx_bytes = bytes; 161 stats->tx_bytes = bytes; 162 return stats; 163 } 164 165 static u32 always_on(struct net_device *dev) 166 { 167 return 1; 168 } 169 170 static const struct ethtool_ops loopback_ethtool_ops = { 171 .get_link = always_on, 172 .set_tso = ethtool_op_set_tso, 173 .get_tx_csum = always_on, 174 .get_sg = always_on, 175 .get_rx_csum = always_on, 176 }; 177 178 static int loopback_dev_init(struct net_device *dev) 179 { 180 struct pcpu_lstats __percpu *lstats; 181 182 lstats = alloc_percpu(struct pcpu_lstats); 183 if (!lstats) 184 return -ENOMEM; 185 186 dev->ml_priv = (void __force *)lstats; 187 return 0; 188 } 189 190 static void loopback_dev_free(struct net_device *dev) 191 { 192 struct pcpu_lstats __percpu *lstats = 193 (void __percpu __force *)dev->ml_priv; 194 195 free_percpu(lstats); 196 free_netdev(dev); 197 } 198 199 static const struct net_device_ops loopback_ops = { 200 .ndo_init = loopback_dev_init, 201 .ndo_start_xmit= loopback_xmit, 202 .ndo_get_stats64 = loopback_get_stats64, 203 }; 204 205 /* 206 * The loopback device is special. There is only one instance 207 * per network namespace. 208 */ 209 static void loopback_setup(struct net_device *dev) 210 { 211 dev->mtu = (16 * 1024) + 20 + 20 + 12; 212 dev->hard_header_len = ETH_HLEN; /* 14 */ 213 dev->addr_len = ETH_ALEN; /* 6 */ 214 dev->tx_queue_len = 0; 215 dev->type = ARPHRD_LOOPBACK; /* 0x0001*/ 216 dev->flags = IFF_LOOPBACK; 217 dev->priv_flags &= ~IFF_XMIT_DST_RELEASE; 218 dev->features = NETIF_F_SG | NETIF_F_FRAGLIST 219 | NETIF_F_TSO 220 | NETIF_F_NO_CSUM 221 | NETIF_F_HIGHDMA 222 | NETIF_F_LLTX 223 | NETIF_F_NETNS_LOCAL; 224 dev->ethtool_ops = &loopback_ethtool_ops; 225 dev->header_ops = ð_header_ops; 226 dev->netdev_ops = &loopback_ops; 227 dev->destructor = loopback_dev_free; 228 } 229 230 /* Setup and register the loopback device. */ 231 static __net_init int loopback_net_init(struct net *net) 232 { 233 struct net_device *dev; 234 int err; 235 236 err = -ENOMEM; 237 dev = alloc_netdev(0, "lo", loopback_setup); 238 if (!dev) 239 goto out; 240 241 dev_net_set(dev, net); 242 err = register_netdev(dev); 243 if (err) 244 goto out_free_netdev; 245 246 net->loopback_dev = dev; 247 return 0; 248 249 250 out_free_netdev: 251 free_netdev(dev); 252 out: 253 if (net_eq(net, &init_net)) 254 panic("loopback: Failed to register netdevice: %d\n", err); 255 return err; 256 } 257 258 /* Registered in net/core/dev.c */ 259 struct pernet_operations __net_initdata loopback_net_ops = { 260 .init = loopback_net_init, 261 }; 262