279 lines · c
1// SPDX-License-Identifier: GPL-2.0-or-later2/*3 * INET An implementation of the TCP/IP protocol suite for the LINUX4 * operating system. INET is implemented using the BSD Socket5 * interface as the means of communication with the user level.6 *7 * Pseudo-driver for the loopback interface.8 *9 * Version: @(#)loopback.c 1.0.4b 08/16/9310 *11 * Authors: Ross Biro12 * Fred N. van Kempen, <waltje@uWalt.NL.Mugnet.ORG>13 * Donald Becker, <becker@scyld.com>14 *15 * Alan Cox : Fixed oddments for NET3.01416 * Alan Cox : Rejig for NET3.029 snap #317 * Alan Cox : Fixed NET3.029 bugs and sped up18 * Larry McVoy : Tiny tweak to double performance19 * Alan Cox : Backed out LMV's tweak - the linux mm20 * can't take it...21 * Michael Griffith: Don't bother computing the checksums22 * on packets received on the loopback23 * interface.24 * Alexey Kuznetsov: Potential hang under some extreme25 * cases removed.26 */27#include <linux/kernel.h>28#include <linux/jiffies.h>29#include <linux/module.h>30#include <linux/interrupt.h>31#include <linux/fs.h>32#include <linux/types.h>33#include <linux/string.h>34#include <linux/socket.h>35#include <linux/errno.h>36#include <linux/fcntl.h>37#include <linux/in.h>38 39#include <linux/uaccess.h>40#include <linux/io.h>41 42#include <linux/inet.h>43#include <linux/netdevice.h>44#include <linux/etherdevice.h>45#include <linux/skbuff.h>46#include <linux/ethtool.h>47#include <net/sch_generic.h>48#include <net/sock.h>49#include <net/checksum.h>50#include <linux/if_ether.h> /* For the statistics structure. */51#include <linux/if_arp.h> /* For ARPHRD_ETHER */52#include <linux/ip.h>53#include <linux/tcp.h>54#include <linux/percpu.h>55#include <linux/net_tstamp.h>56#include <net/net_namespace.h>57#include <linux/u64_stats_sync.h>58 59/* blackhole_netdev - a device used for dsts that are marked expired!60 * This is global device (instead of per-net-ns) since it's not needed61 * to be per-ns and gets initialized at boot time.62 */63struct net_device *blackhole_netdev;64EXPORT_SYMBOL(blackhole_netdev);65 66/* The higher levels take care of making this non-reentrant (it's67 * called with bh's disabled).68 */69static netdev_tx_t loopback_xmit(struct sk_buff *skb,70 struct net_device *dev)71{72 int len;73 74 skb_tx_timestamp(skb);75 76 /* do not fool net_timestamp_check() with various clock bases */77 skb_clear_tstamp(skb);78 79 skb_orphan(skb);80 81 /* Before queueing this packet to __netif_rx(),82 * make sure dst is refcounted.83 */84 skb_dst_force(skb);85 86 skb->protocol = eth_type_trans(skb, dev);87 88 len = skb->len;89 if (likely(__netif_rx(skb) == NET_RX_SUCCESS))90 dev_lstats_add(dev, len);91 92 return NETDEV_TX_OK;93}94 95void dev_lstats_read(struct net_device *dev, u64 *packets, u64 *bytes)96{97 int i;98 99 *packets = 0;100 *bytes = 0;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(&lb_stats->syncp);110 tpackets = u64_stats_read(&lb_stats->packets);111 tbytes = u64_stats_read(&lb_stats->bytes);112 } while (u64_stats_fetch_retry(&lb_stats->syncp, start));113 *bytes += tbytes;114 *packets += tpackets;115 }116}117EXPORT_SYMBOL(dev_lstats_read);118 119static void loopback_get_stats64(struct net_device *dev,120 struct rtnl_link_stats64 *stats)121{122 u64 packets, bytes;123 124 dev_lstats_read(dev, &packets, &bytes);125 126 stats->rx_packets = packets;127 stats->tx_packets = packets;128 stats->rx_bytes = bytes;129 stats->tx_bytes = bytes;130}131 132static u32 always_on(struct net_device *dev)133{134 return 1;135}136 137static const struct ethtool_ops loopback_ethtool_ops = {138 .get_link = always_on,139 .get_ts_info = ethtool_op_get_ts_info,140};141 142static int loopback_dev_init(struct net_device *dev)143{144 netdev_lockdep_set_classes(dev);145 return 0;146}147 148static void loopback_dev_free(struct net_device *dev)149{150 dev_net(dev)->loopback_dev = NULL;151}152 153static const struct net_device_ops loopback_ops = {154 .ndo_init = loopback_dev_init,155 .ndo_start_xmit = loopback_xmit,156 .ndo_get_stats64 = loopback_get_stats64,157 .ndo_set_mac_address = eth_mac_addr,158};159 160static void gen_lo_setup(struct net_device *dev,161 unsigned int mtu,162 const struct ethtool_ops *eth_ops,163 const struct header_ops *hdr_ops,164 const struct net_device_ops *dev_ops,165 void (*dev_destructor)(struct net_device *dev))166{167 dev->mtu = mtu;168 dev->hard_header_len = ETH_HLEN; /* 14 */169 dev->min_header_len = ETH_HLEN; /* 14 */170 dev->addr_len = ETH_ALEN; /* 6 */171 dev->type = ARPHRD_LOOPBACK; /* 0x0001*/172 dev->flags = IFF_LOOPBACK;173 dev->priv_flags |= IFF_LIVE_ADDR_CHANGE | IFF_NO_QUEUE;174 dev->lltx = true;175 dev->netns_local = true;176 netif_keep_dst(dev);177 dev->hw_features = NETIF_F_GSO_SOFTWARE;178 dev->features = NETIF_F_SG | NETIF_F_FRAGLIST179 | NETIF_F_GSO_SOFTWARE180 | NETIF_F_HW_CSUM181 | NETIF_F_RXCSUM182 | NETIF_F_SCTP_CRC183 | NETIF_F_HIGHDMA184 | NETIF_F_VLAN_CHALLENGED185 | NETIF_F_LOOPBACK;186 dev->ethtool_ops = eth_ops;187 dev->header_ops = hdr_ops;188 dev->netdev_ops = dev_ops;189 dev->needs_free_netdev = true;190 dev->pcpu_stat_type = NETDEV_PCPU_STAT_LSTATS;191 dev->priv_destructor = dev_destructor;192 193 netif_set_tso_max_size(dev, GSO_MAX_SIZE);194}195 196/* The loopback device is special. There is only one instance197 * per network namespace.198 */199static void loopback_setup(struct net_device *dev)200{201 gen_lo_setup(dev, (64 * 1024), &loopback_ethtool_ops, ð_header_ops,202 &loopback_ops, loopback_dev_free);203}204 205/* Setup and register the loopback device. */206static __net_init int loopback_net_init(struct net *net)207{208 struct net_device *dev;209 int err;210 211 err = -ENOMEM;212 dev = alloc_netdev(0, "lo", NET_NAME_PREDICTABLE, loopback_setup);213 if (!dev)214 goto out;215 216 dev_net_set(dev, net);217 err = register_netdev(dev);218 if (err)219 goto out_free_netdev;220 221 BUG_ON(dev->ifindex != LOOPBACK_IFINDEX);222 net->loopback_dev = dev;223 return 0;224 225out_free_netdev:226 free_netdev(dev);227out:228 if (net_eq(net, &init_net))229 panic("loopback: Failed to register netdevice: %d\n", err);230 return err;231}232 233/* Registered in net/core/dev.c */234struct pernet_operations __net_initdata loopback_net_ops = {235 .init = loopback_net_init,236};237 238/* blackhole netdevice */239static netdev_tx_t blackhole_netdev_xmit(struct sk_buff *skb,240 struct net_device *dev)241{242 kfree_skb(skb);243 net_warn_ratelimited("%s(): Dropping skb.\n", __func__);244 return NETDEV_TX_OK;245}246 247static const struct net_device_ops blackhole_netdev_ops = {248 .ndo_start_xmit = blackhole_netdev_xmit,249};250 251/* This is a dst-dummy device used specifically for invalidated252 * DSTs and unlike loopback, this is not per-ns.253 */254static void blackhole_netdev_setup(struct net_device *dev)255{256 gen_lo_setup(dev, ETH_MIN_MTU, NULL, NULL, &blackhole_netdev_ops, NULL);257}258 259/* Setup and register the blackhole_netdev. */260static int __init blackhole_netdev_init(void)261{262 blackhole_netdev = alloc_netdev(0, "blackhole_dev", NET_NAME_UNKNOWN,263 blackhole_netdev_setup);264 if (!blackhole_netdev)265 return -ENOMEM;266 267 rtnl_lock();268 dev_init_scheduler(blackhole_netdev);269 dev_activate(blackhole_netdev);270 rtnl_unlock();271 272 blackhole_netdev->flags |= IFF_UP | IFF_RUNNING;273 dev_net_set(blackhole_netdev, &init_net);274 275 return 0;276}277 278device_initcall(blackhole_netdev_init);279