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 43 #include <linux/uaccess.h> 44 #include <asm/io.h> 45 46 #include <linux/inet.h> 47 #include <linux/netdevice.h> 48 #include <linux/etherdevice.h> 49 #include <linux/skbuff.h> 50 #include <linux/ethtool.h> 51 #include <net/sock.h> 52 #include <net/checksum.h> 53 #include <linux/if_ether.h> /* For the statistics structure. */ 54 #include <linux/if_arp.h> /* For ARPHRD_ETHER */ 55 #include <linux/ip.h> 56 #include <linux/tcp.h> 57 #include <linux/percpu.h> 58 #include <net/net_namespace.h> 59 #include <linux/u64_stats_sync.h> 60 61 struct pcpu_lstats { 62 u64 packets; 63 u64 bytes; 64 struct u64_stats_sync syncp; 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 netdev_tx_t loopback_xmit(struct sk_buff *skb, 72 struct net_device *dev) 73 { 74 struct pcpu_lstats *lb_stats; 75 int len; 76 77 skb_orphan(skb); 78 79 /* Before queueing this packet to netif_rx(), 80 * make sure dst is refcounted. 81 */ 82 skb_dst_force(skb); 83 84 skb->protocol = eth_type_trans(skb, dev); 85 86 /* it's OK to use per_cpu_ptr() because BHs are off */ 87 lb_stats = this_cpu_ptr(dev->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 } 96 97 return NETDEV_TX_OK; 98 } 99 100 static void loopback_get_stats64(struct net_device *dev, 101 struct rtnl_link_stats64 *stats) 102 { 103 u64 bytes = 0; 104 u64 packets = 0; 105 int i; 106 107 for_each_possible_cpu(i) { 108 const struct pcpu_lstats *lb_stats; 109 u64 tbytes, tpackets; 110 unsigned int start; 111 112 lb_stats = per_cpu_ptr(dev->lstats, i); 113 do { 114 start = u64_stats_fetch_begin_irq(&lb_stats->syncp); 115 tbytes = lb_stats->bytes; 116 tpackets = lb_stats->packets; 117 } while (u64_stats_fetch_retry_irq(&lb_stats->syncp, start)); 118 bytes += tbytes; 119 packets += tpackets; 120 } 121 stats->rx_packets = packets; 122 stats->tx_packets = packets; 123 stats->rx_bytes = bytes; 124 stats->tx_bytes = bytes; 125 } 126 127 static u32 always_on(struct net_device *dev) 128 { 129 return 1; 130 } 131 132 static const struct ethtool_ops loopback_ethtool_ops = { 133 .get_link = always_on, 134 }; 135 136 static int loopback_dev_init(struct net_device *dev) 137 { 138 dev->lstats = netdev_alloc_pcpu_stats(struct pcpu_lstats); 139 if (!dev->lstats) 140 return -ENOMEM; 141 return 0; 142 } 143 144 static void loopback_dev_free(struct net_device *dev) 145 { 146 dev_net(dev)->loopback_dev = NULL; 147 free_percpu(dev->lstats); 148 free_netdev(dev); 149 } 150 151 static const struct net_device_ops loopback_ops = { 152 .ndo_init = loopback_dev_init, 153 .ndo_start_xmit= loopback_xmit, 154 .ndo_get_stats64 = loopback_get_stats64, 155 .ndo_set_mac_address = eth_mac_addr, 156 }; 157 158 /* 159 * The loopback device is special. There is only one instance 160 * per network namespace. 161 */ 162 static void loopback_setup(struct net_device *dev) 163 { 164 dev->mtu = 64 * 1024; 165 dev->hard_header_len = ETH_HLEN; /* 14 */ 166 dev->min_header_len = ETH_HLEN; /* 14 */ 167 dev->addr_len = ETH_ALEN; /* 6 */ 168 dev->type = ARPHRD_LOOPBACK; /* 0x0001*/ 169 dev->flags = IFF_LOOPBACK; 170 dev->priv_flags |= IFF_LIVE_ADDR_CHANGE | IFF_NO_QUEUE; 171 netif_keep_dst(dev); 172 dev->hw_features = NETIF_F_GSO_SOFTWARE; 173 dev->features = NETIF_F_SG | NETIF_F_FRAGLIST 174 | NETIF_F_GSO_SOFTWARE 175 | NETIF_F_HW_CSUM 176 | NETIF_F_RXCSUM 177 | NETIF_F_SCTP_CRC 178 | NETIF_F_HIGHDMA 179 | NETIF_F_LLTX 180 | NETIF_F_NETNS_LOCAL 181 | NETIF_F_VLAN_CHALLENGED 182 | NETIF_F_LOOPBACK; 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", NET_NAME_UNKNOWN, 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 BUG_ON(dev->ifindex != LOOPBACK_IFINDEX); 206 net->loopback_dev = dev; 207 return 0; 208 209 210 out_free_netdev: 211 free_netdev(dev); 212 out: 213 if (net_eq(net, &init_net)) 214 panic("loopback: Failed to register netdevice: %d\n", err); 215 return err; 216 } 217 218 /* Registered in net/core/dev.c */ 219 struct pernet_operations __net_initdata loopback_net_ops = { 220 .init = loopback_net_init, 221 }; 222