/* * INET An implementation of the TCP/IP protocol suite for the LINUX * operating system. INET is implemented using the BSD Socket * interface as the means of communication with the user level. * * Pseudo-driver for the loopback interface. * * Version: @(#)loopback.c 1.0.4b 08/16/93 * * Authors: Ross Biro * Fred N. van Kempen, <waltje@uWalt.NL.Mugnet.ORG> * Donald Becker, <becker@scyld.com> * * Alan Cox : Fixed oddments for NET3.014 * Alan Cox : Rejig for NET3.029 snap #3 * Alan Cox : Fixed NET3.029 bugs and sped up * Larry McVoy : Tiny tweak to double performance * Alan Cox : Backed out LMV's tweak - the linux mm * can't take it... * Michael Griffith: Don't bother computing the checksums * on packets received on the loopback * interface. * Alexey Kuznetsov: Potential hang under some extreme * cases removed. * * This program is free software; you can redistribute it and/or * modify it under the terms of the GNU General Public License * as published by the Free Software Foundation; either version * 2 of the License, or (at your option) any later version. */ #include <linux/kernel.h> #include <linux/jiffies.h> #include <linux/module.h> #include <linux/interrupt.h> #include <linux/fs.h> #include <linux/types.h> #include <linux/string.h> #include <linux/socket.h> #include <linux/errno.h> #include <linux/fcntl.h> #include <linux/in.h> #include <linux/init.h> #include <asm/system.h> #include <asm/uaccess.h> #include <asm/io.h> #include <linux/inet.h> #include <linux/netdevice.h> #include <linux/etherdevice.h> #include <linux/skbuff.h> #include <linux/ethtool.h> #include <net/sock.h> #include <net/checksum.h> #include <linux/if_ether.h> /* For the statistics structure. */ #include <linux/if_arp.h> /* For ARPHRD_ETHER */ #include <linux/ip.h> #include <linux/tcp.h> #include <linux/percpu.h> #include <net/net_namespace.h> #include <linux/u64_stats_sync.h> struct pcpu_lstats { u64 packets; u64 bytes; struct u64_stats_sync syncp; }; /* * The higher levels take care of making this non-reentrant (it's * called with bh's disabled). */ static netdev_tx_t loopback_xmit(struct sk_buff *skb, struct net_device *dev) { struct pcpu_lstats *lb_stats; int len; skb_orphan(skb); skb->protocol = eth_type_trans(skb, dev); /* it's OK to use per_cpu_ptr() because BHs are off */ lb_stats = this_cpu_ptr(dev->lstats); len = skb->len; if (likely(netif_rx(skb) == NET_RX_SUCCESS)) { u64_stats_update_begin(&lb_stats->syncp); lb_stats->bytes += len; lb_stats->packets++; u64_stats_update_end(&lb_stats->syncp); } return NETDEV_TX_OK; } static struct rtnl_link_stats64 *loopback_get_stats64(struct net_device *dev, struct rtnl_link_stats64 *stats) { u64 bytes = 0; u64 packets = 0; int i; for_each_possible_cpu(i) { const struct pcpu_lstats *lb_stats; u64 tbytes, tpackets; unsigned int start; lb_stats = per_cpu_ptr(dev->lstats, i); do { start = u64_stats_fetch_begin(&lb_stats->syncp); tbytes = lb_stats->bytes; tpackets = lb_stats->packets; } while (u64_stats_fetch_retry(&lb_stats->syncp, start)); bytes += tbytes; packets += tpackets; } stats->rx_packets = packets; stats->tx_packets = packets; stats->rx_bytes = bytes; stats->tx_bytes = bytes; return stats; } static u32 always_on(struct net_device *dev) { return 1; } static const struct ethtool_ops loopback_ethtool_ops = { .get_link = always_on, }; static int loopback_dev_init(struct net_device *dev) { dev->lstats = alloc_percpu(struct pcpu_lstats); if (!dev->lstats) return -ENOMEM; return 0; } static void loopback_dev_free(struct net_device *dev) { free_percpu(dev->lstats); free_netdev(dev); } static const struct net_device_ops loopback_ops = { .ndo_init = loopback_dev_init, .ndo_start_xmit= loopback_xmit, .ndo_get_stats64 = loopback_get_stats64, }; /* * The loopback device is special. There is only one instance * per network namespace. */ static void loopback_setup(struct net_device *dev) { dev->mtu = (16 * 1024) + 20 + 20 + 12; dev->hard_header_len = ETH_HLEN; /* 14 */ dev->addr_len = ETH_ALEN; /* 6 */ dev->tx_queue_len = 0; dev->type = ARPHRD_LOOPBACK; /* 0x0001*/ dev->flags = IFF_LOOPBACK; dev->priv_flags &= ~IFF_XMIT_DST_RELEASE; dev->hw_features = NETIF_F_ALL_TSO | NETIF_F_UFO; dev->features = NETIF_F_SG | NETIF_F_FRAGLIST | NETIF_F_ALL_TSO | NETIF_F_UFO | NETIF_F_NO_CSUM | NETIF_F_RXCSUM | NETIF_F_HIGHDMA | NETIF_F_LLTX | NETIF_F_NETNS_LOCAL | NETIF_F_VLAN_CHALLENGED | NETIF_F_LOOPBACK; dev->ethtool_ops = &loopback_ethtool_ops; dev->header_ops = ð_header_ops; dev->netdev_ops = &loopback_ops; dev->destructor = loopback_dev_free; } /* Setup and register the loopback device. */ static __net_init int loopback_net_init(struct net *net) { struct net_device *dev; int err; err = -ENOMEM; dev = alloc_netdev(0, "lo", loopback_setup); if (!dev) goto out; dev_net_set(dev, net); err = register_netdev(dev); if (err) goto out_free_netdev; net->loopback_dev = dev; return 0; out_free_netdev: free_netdev(dev); out: if (net_eq(net, &init_net)) panic("loopback: Failed to register netdevice: %d\n", err); return err; } /* Registered in net/core/dev.c */ struct pernet_operations __net_initdata loopback_net_ops = { .init = loopback_net_init, };