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 <linux/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 <linux/net_tstamp.h> 59 #include <net/net_namespace.h> 60 #include <linux/u64_stats_sync.h> 61 62 /* The higher levels take care of making this non-reentrant (it's 63 * called with bh's disabled). 64 */ 65 static netdev_tx_t loopback_xmit(struct sk_buff *skb, 66 struct net_device *dev) 67 { 68 struct pcpu_lstats *lb_stats; 69 int len; 70 71 skb_tx_timestamp(skb); 72 skb_orphan(skb); 73 74 /* Before queueing this packet to netif_rx(), 75 * make sure dst is refcounted. 76 */ 77 skb_dst_force(skb); 78 79 skb->protocol = eth_type_trans(skb, dev); 80 81 /* it's OK to use per_cpu_ptr() because BHs are off */ 82 lb_stats = this_cpu_ptr(dev->lstats); 83 84 len = skb->len; 85 if (likely(netif_rx(skb) == NET_RX_SUCCESS)) { 86 u64_stats_update_begin(&lb_stats->syncp); 87 lb_stats->bytes += len; 88 lb_stats->packets++; 89 u64_stats_update_end(&lb_stats->syncp); 90 } 91 92 return NETDEV_TX_OK; 93 } 94 95 static void loopback_get_stats64(struct net_device *dev, 96 struct rtnl_link_stats64 *stats) 97 { 98 u64 bytes = 0; 99 u64 packets = 0; 100 int i; 101 102 for_each_possible_cpu(i) { 103 const struct pcpu_lstats *lb_stats; 104 u64 tbytes, tpackets; 105 unsigned int start; 106 107 lb_stats = per_cpu_ptr(dev->lstats, i); 108 do { 109 start = u64_stats_fetch_begin_irq(&lb_stats->syncp); 110 tbytes = lb_stats->bytes; 111 tpackets = lb_stats->packets; 112 } while (u64_stats_fetch_retry_irq(&lb_stats->syncp, start)); 113 bytes += tbytes; 114 packets += tpackets; 115 } 116 stats->rx_packets = packets; 117 stats->tx_packets = packets; 118 stats->rx_bytes = bytes; 119 stats->tx_bytes = bytes; 120 } 121 122 static u32 always_on(struct net_device *dev) 123 { 124 return 1; 125 } 126 127 static int loopback_get_ts_info(struct net_device *netdev, 128 struct ethtool_ts_info *ts_info) 129 { 130 ts_info->so_timestamping = SOF_TIMESTAMPING_TX_SOFTWARE | 131 SOF_TIMESTAMPING_RX_SOFTWARE | 132 SOF_TIMESTAMPING_SOFTWARE; 133 134 ts_info->phc_index = -1; 135 136 return 0; 137 }; 138 139 static const struct ethtool_ops loopback_ethtool_ops = { 140 .get_link = always_on, 141 .get_ts_info = loopback_get_ts_info, 142 }; 143 144 static int loopback_dev_init(struct net_device *dev) 145 { 146 dev->lstats = netdev_alloc_pcpu_stats(struct pcpu_lstats); 147 if (!dev->lstats) 148 return -ENOMEM; 149 return 0; 150 } 151 152 static void loopback_dev_free(struct net_device *dev) 153 { 154 dev_net(dev)->loopback_dev = NULL; 155 free_percpu(dev->lstats); 156 } 157 158 static const struct net_device_ops loopback_ops = { 159 .ndo_init = loopback_dev_init, 160 .ndo_start_xmit = loopback_xmit, 161 .ndo_get_stats64 = loopback_get_stats64, 162 .ndo_set_mac_address = eth_mac_addr, 163 }; 164 165 /* The loopback device is special. There is only one instance 166 * per network namespace. 167 */ 168 static void loopback_setup(struct net_device *dev) 169 { 170 dev->mtu = 64 * 1024; 171 dev->hard_header_len = ETH_HLEN; /* 14 */ 172 dev->min_header_len = ETH_HLEN; /* 14 */ 173 dev->addr_len = ETH_ALEN; /* 6 */ 174 dev->type = ARPHRD_LOOPBACK; /* 0x0001*/ 175 dev->flags = IFF_LOOPBACK; 176 dev->priv_flags |= IFF_LIVE_ADDR_CHANGE | IFF_NO_QUEUE; 177 netif_keep_dst(dev); 178 dev->hw_features = NETIF_F_GSO_SOFTWARE; 179 dev->features = NETIF_F_SG | NETIF_F_FRAGLIST 180 | NETIF_F_GSO_SOFTWARE 181 | NETIF_F_HW_CSUM 182 | NETIF_F_RXCSUM 183 | NETIF_F_SCTP_CRC 184 | NETIF_F_HIGHDMA 185 | NETIF_F_LLTX 186 | NETIF_F_NETNS_LOCAL 187 | NETIF_F_VLAN_CHALLENGED 188 | NETIF_F_LOOPBACK; 189 dev->ethtool_ops = &loopback_ethtool_ops; 190 dev->header_ops = ð_header_ops; 191 dev->netdev_ops = &loopback_ops; 192 dev->needs_free_netdev = true; 193 dev->priv_destructor = loopback_dev_free; 194 } 195 196 /* Setup and register the loopback device. */ 197 static __net_init int loopback_net_init(struct net *net) 198 { 199 struct net_device *dev; 200 int err; 201 202 err = -ENOMEM; 203 dev = alloc_netdev(0, "lo", NET_NAME_UNKNOWN, loopback_setup); 204 if (!dev) 205 goto out; 206 207 dev_net_set(dev, net); 208 err = register_netdev(dev); 209 if (err) 210 goto out_free_netdev; 211 212 BUG_ON(dev->ifindex != LOOPBACK_IFINDEX); 213 net->loopback_dev = dev; 214 return 0; 215 216 out_free_netdev: 217 free_netdev(dev); 218 out: 219 if (net_eq(net, &init_net)) 220 panic("loopback: Failed to register netdevice: %d\n", err); 221 return err; 222 } 223 224 /* Registered in net/core/dev.c */ 225 struct pernet_operations __net_initdata loopback_net_ops = { 226 .init = loopback_net_init, 227 }; 228