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 #include <linux/u64_stats_sync.h> 62 63 struct pcpu_lstats { 64 u64 packets; 65 u64 bytes; 66 struct u64_stats_sync syncp; 67 unsigned long drops; 68 }; 69 70 /* 71 * The higher levels take care of making this non-reentrant (it's 72 * called with bh's disabled). 73 */ 74 static netdev_tx_t loopback_xmit(struct sk_buff *skb, 75 struct net_device *dev) 76 { 77 struct pcpu_lstats __percpu *pcpu_lstats; 78 struct pcpu_lstats *lb_stats; 79 int len; 80 81 skb_orphan(skb); 82 83 skb->protocol = eth_type_trans(skb, dev); 84 85 /* it's OK to use per_cpu_ptr() because BHs are off */ 86 pcpu_lstats = (void __percpu __force *)dev->ml_priv; 87 lb_stats = this_cpu_ptr(pcpu_lstats); 88 89 len = skb->len; 90 if (likely(netif_rx(skb) == NET_RX_SUCCESS)) { 91 u64_stats_update_begin(&lb_stats->syncp); 92 lb_stats->bytes += len; 93 lb_stats->packets++; 94 u64_stats_update_end(&lb_stats->syncp); 95 } else 96 lb_stats->drops++; 97 98 return NETDEV_TX_OK; 99 } 100 101 static struct rtnl_link_stats64 *loopback_get_stats64(struct net_device *dev, 102 struct rtnl_link_stats64 *stats) 103 { 104 const struct pcpu_lstats __percpu *pcpu_lstats; 105 u64 bytes = 0; 106 u64 packets = 0; 107 u64 drops = 0; 108 int i; 109 110 pcpu_lstats = (void __percpu __force *)dev->ml_priv; 111 for_each_possible_cpu(i) { 112 const struct pcpu_lstats *lb_stats; 113 u64 tbytes, tpackets; 114 unsigned int start; 115 116 lb_stats = per_cpu_ptr(pcpu_lstats, i); 117 do { 118 start = u64_stats_fetch_begin(&lb_stats->syncp); 119 tbytes = lb_stats->bytes; 120 tpackets = lb_stats->packets; 121 } while (u64_stats_fetch_retry(&lb_stats->syncp, start)); 122 drops += lb_stats->drops; 123 bytes += tbytes; 124 packets += tpackets; 125 } 126 stats->rx_packets = packets; 127 stats->tx_packets = packets; 128 stats->rx_dropped = drops; 129 stats->rx_errors = drops; 130 stats->rx_bytes = bytes; 131 stats->tx_bytes = bytes; 132 return stats; 133 } 134 135 static u32 always_on(struct net_device *dev) 136 { 137 return 1; 138 } 139 140 static const struct ethtool_ops loopback_ethtool_ops = { 141 .get_link = always_on, 142 .set_tso = ethtool_op_set_tso, 143 .get_tx_csum = always_on, 144 .get_sg = always_on, 145 .get_rx_csum = always_on, 146 }; 147 148 static int loopback_dev_init(struct net_device *dev) 149 { 150 struct pcpu_lstats __percpu *lstats; 151 152 lstats = alloc_percpu(struct pcpu_lstats); 153 if (!lstats) 154 return -ENOMEM; 155 156 dev->ml_priv = (void __force *)lstats; 157 return 0; 158 } 159 160 static void loopback_dev_free(struct net_device *dev) 161 { 162 struct pcpu_lstats __percpu *lstats = 163 (void __percpu __force *)dev->ml_priv; 164 165 free_percpu(lstats); 166 free_netdev(dev); 167 } 168 169 static const struct net_device_ops loopback_ops = { 170 .ndo_init = loopback_dev_init, 171 .ndo_start_xmit= loopback_xmit, 172 .ndo_get_stats64 = loopback_get_stats64, 173 }; 174 175 /* 176 * The loopback device is special. There is only one instance 177 * per network namespace. 178 */ 179 static void loopback_setup(struct net_device *dev) 180 { 181 dev->mtu = (16 * 1024) + 20 + 20 + 12; 182 dev->hard_header_len = ETH_HLEN; /* 14 */ 183 dev->addr_len = ETH_ALEN; /* 6 */ 184 dev->tx_queue_len = 0; 185 dev->type = ARPHRD_LOOPBACK; /* 0x0001*/ 186 dev->flags = IFF_LOOPBACK; 187 dev->priv_flags &= ~IFF_XMIT_DST_RELEASE; 188 dev->features = NETIF_F_SG | NETIF_F_FRAGLIST 189 | NETIF_F_TSO 190 | NETIF_F_NO_CSUM 191 | NETIF_F_HIGHDMA 192 | NETIF_F_LLTX 193 | NETIF_F_NETNS_LOCAL; 194 dev->ethtool_ops = &loopback_ethtool_ops; 195 dev->header_ops = ð_header_ops; 196 dev->netdev_ops = &loopback_ops; 197 dev->destructor = loopback_dev_free; 198 } 199 200 /* Setup and register the loopback device. */ 201 static __net_init int loopback_net_init(struct net *net) 202 { 203 struct net_device *dev; 204 int err; 205 206 err = -ENOMEM; 207 dev = alloc_netdev(0, "lo", loopback_setup); 208 if (!dev) 209 goto out; 210 211 dev_net_set(dev, net); 212 err = register_netdev(dev); 213 if (err) 214 goto out_free_netdev; 215 216 net->loopback_dev = dev; 217 return 0; 218 219 220 out_free_netdev: 221 free_netdev(dev); 222 out: 223 if (net_eq(net, &init_net)) 224 panic("loopback: Failed to register netdevice: %d\n", err); 225 return err; 226 } 227 228 /* Registered in net/core/dev.c */ 229 struct pernet_operations __net_initdata loopback_net_ops = { 230 .init = loopback_net_init, 231 }; 232