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/uaccess.h> 45 #include <asm/io.h> 46 47 #include <linux/inet.h> 48 #include <linux/netdevice.h> 49 #include <linux/etherdevice.h> 50 #include <linux/skbuff.h> 51 #include <linux/ethtool.h> 52 #include <net/sock.h> 53 #include <net/checksum.h> 54 #include <linux/if_ether.h> /* For the statistics structure. */ 55 #include <linux/if_arp.h> /* For ARPHRD_ETHER */ 56 #include <linux/ip.h> 57 #include <linux/tcp.h> 58 #include <linux/percpu.h> 59 #include <net/net_namespace.h> 60 #include <linux/u64_stats_sync.h> 61 62 struct pcpu_lstats { 63 u64 packets; 64 u64 bytes; 65 struct u64_stats_sync syncp; 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 *lb_stats; 76 int len; 77 78 skb_orphan(skb); 79 80 skb->protocol = eth_type_trans(skb, dev); 81 82 /* it's OK to use per_cpu_ptr() because BHs are off */ 83 lb_stats = this_cpu_ptr(dev->lstats); 84 85 len = skb->len; 86 if (likely(netif_rx(skb) == NET_RX_SUCCESS)) { 87 u64_stats_update_begin(&lb_stats->syncp); 88 lb_stats->bytes += len; 89 lb_stats->packets++; 90 u64_stats_update_end(&lb_stats->syncp); 91 } 92 93 return NETDEV_TX_OK; 94 } 95 96 static struct rtnl_link_stats64 *loopback_get_stats64(struct net_device *dev, 97 struct rtnl_link_stats64 *stats) 98 { 99 u64 bytes = 0; 100 u64 packets = 0; 101 int i; 102 103 for_each_possible_cpu(i) { 104 const struct pcpu_lstats *lb_stats; 105 u64 tbytes, tpackets; 106 unsigned int start; 107 108 lb_stats = per_cpu_ptr(dev->lstats, i); 109 do { 110 start = u64_stats_fetch_begin(&lb_stats->syncp); 111 tbytes = lb_stats->bytes; 112 tpackets = lb_stats->packets; 113 } while (u64_stats_fetch_retry(&lb_stats->syncp, start)); 114 bytes += tbytes; 115 packets += tpackets; 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 }; 132 133 static int loopback_dev_init(struct net_device *dev) 134 { 135 dev->lstats = alloc_percpu(struct pcpu_lstats); 136 if (!dev->lstats) 137 return -ENOMEM; 138 139 return 0; 140 } 141 142 static void loopback_dev_free(struct net_device *dev) 143 { 144 free_percpu(dev->lstats); 145 free_netdev(dev); 146 } 147 148 static const struct net_device_ops loopback_ops = { 149 .ndo_init = loopback_dev_init, 150 .ndo_start_xmit= loopback_xmit, 151 .ndo_get_stats64 = loopback_get_stats64, 152 }; 153 154 /* 155 * The loopback device is special. There is only one instance 156 * per network namespace. 157 */ 158 static void loopback_setup(struct net_device *dev) 159 { 160 dev->mtu = (16 * 1024) + 20 + 20 + 12; 161 dev->hard_header_len = ETH_HLEN; /* 14 */ 162 dev->addr_len = ETH_ALEN; /* 6 */ 163 dev->tx_queue_len = 0; 164 dev->type = ARPHRD_LOOPBACK; /* 0x0001*/ 165 dev->flags = IFF_LOOPBACK; 166 dev->priv_flags &= ~IFF_XMIT_DST_RELEASE; 167 dev->hw_features = NETIF_F_ALL_TSO | NETIF_F_UFO; 168 dev->features = NETIF_F_SG | NETIF_F_FRAGLIST 169 | NETIF_F_ALL_TSO 170 | NETIF_F_UFO 171 | NETIF_F_HW_CSUM 172 | NETIF_F_RXCSUM 173 | NETIF_F_HIGHDMA 174 | NETIF_F_LLTX 175 | NETIF_F_NETNS_LOCAL 176 | NETIF_F_VLAN_CHALLENGED 177 | NETIF_F_LOOPBACK; 178 dev->ethtool_ops = &loopback_ethtool_ops; 179 dev->header_ops = ð_header_ops; 180 dev->netdev_ops = &loopback_ops; 181 dev->destructor = loopback_dev_free; 182 } 183 184 /* Setup and register the loopback device. */ 185 static __net_init int loopback_net_init(struct net *net) 186 { 187 struct net_device *dev; 188 int err; 189 190 err = -ENOMEM; 191 dev = alloc_netdev(0, "lo", loopback_setup); 192 if (!dev) 193 goto out; 194 195 dev_net_set(dev, net); 196 err = register_netdev(dev); 197 if (err) 198 goto out_free_netdev; 199 200 net->loopback_dev = dev; 201 return 0; 202 203 204 out_free_netdev: 205 free_netdev(dev); 206 out: 207 if (net_eq(net, &init_net)) 208 panic("loopback: Failed to register netdevice: %d\n", err); 209 return err; 210 } 211 212 /* Registered in net/core/dev.c */ 213 struct pernet_operations __net_initdata loopback_net_ops = { 214 .init = loopback_net_init, 215 }; 216