// SPDX-License-Identifier: GPL-2.0-or-later /* * 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. */ #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/uaccess.h> #include <linux/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 <linux/net_tstamp.h> #include <net/net_namespace.h> #include <linux/u64_stats_sync.h> /* blackhole_netdev - a device used for dsts that are marked expired! * This is global device (instead of per-net-ns) since it's not needed * to be per-ns and gets initialized at boot time. */ struct net_device *blackhole_netdev; EXPORT_SYMBOL(blackhole_netdev); /* 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) { int len; skb_tx_timestamp(skb); /* do not fool net_timestamp_check() with various clock bases */ skb->tstamp = 0; skb_orphan(skb); /* Before queueing this packet to netif_rx(), * make sure dst is refcounted. */ skb_dst_force(skb); skb->protocol = eth_type_trans(skb, dev); len = skb->len; if (likely(netif_rx(skb) == NET_RX_SUCCESS)) dev_lstats_add(dev, len); return NETDEV_TX_OK; } void dev_lstats_read(struct net_device *dev, u64 *packets, u64 *bytes) { int i; *packets = 0; *bytes = 0; 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_irq(&lb_stats->syncp); tpackets = u64_stats_read(&lb_stats->packets); tbytes = u64_stats_read(&lb_stats->bytes); } while (u64_stats_fetch_retry_irq(&lb_stats->syncp, start)); *bytes += tbytes; *packets += tpackets; } } EXPORT_SYMBOL(dev_lstats_read); static void loopback_get_stats64(struct net_device *dev, struct rtnl_link_stats64 *stats) { u64 packets, bytes; dev_lstats_read(dev, &packets, &bytes); stats->rx_packets = packets; stats->tx_packets = packets; stats->rx_bytes = bytes; stats->tx_bytes = bytes; } static u32 always_on(struct net_device *dev) { return 1; } static const struct ethtool_ops loopback_ethtool_ops = { .get_link = always_on, .get_ts_info = ethtool_op_get_ts_info, }; static int loopback_dev_init(struct net_device *dev) { dev->lstats = netdev_alloc_pcpu_stats(struct pcpu_lstats); if (!dev->lstats) return -ENOMEM; return 0; } static void loopback_dev_free(struct net_device *dev) { dev_net(dev)->loopback_dev = NULL; free_percpu(dev->lstats); } static const struct net_device_ops loopback_ops = { .ndo_init = loopback_dev_init, .ndo_start_xmit = loopback_xmit, .ndo_get_stats64 = loopback_get_stats64, .ndo_set_mac_address = eth_mac_addr, }; static void gen_lo_setup(struct net_device *dev, unsigned int mtu, const struct ethtool_ops *eth_ops, const struct header_ops *hdr_ops, const struct net_device_ops *dev_ops, void (*dev_destructor)(struct net_device *dev)) { dev->mtu = mtu; dev->hard_header_len = ETH_HLEN; /* 14 */ dev->min_header_len = ETH_HLEN; /* 14 */ dev->addr_len = ETH_ALEN; /* 6 */ dev->type = ARPHRD_LOOPBACK; /* 0x0001*/ dev->flags = IFF_LOOPBACK; dev->priv_flags |= IFF_LIVE_ADDR_CHANGE | IFF_NO_QUEUE; netif_keep_dst(dev); dev->hw_features = NETIF_F_GSO_SOFTWARE; dev->features = NETIF_F_SG | NETIF_F_FRAGLIST | NETIF_F_GSO_SOFTWARE | NETIF_F_HW_CSUM | NETIF_F_RXCSUM | NETIF_F_SCTP_CRC | NETIF_F_HIGHDMA | NETIF_F_LLTX | NETIF_F_NETNS_LOCAL | NETIF_F_VLAN_CHALLENGED | NETIF_F_LOOPBACK; dev->ethtool_ops = eth_ops; dev->header_ops = hdr_ops; dev->netdev_ops = dev_ops; dev->needs_free_netdev = true; dev->priv_destructor = dev_destructor; } /* The loopback device is special. There is only one instance * per network namespace. */ static void loopback_setup(struct net_device *dev) { gen_lo_setup(dev, (64 * 1024), &loopback_ethtool_ops, ð_header_ops, &loopback_ops, 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", NET_NAME_UNKNOWN, loopback_setup); if (!dev) goto out; dev_net_set(dev, net); err = register_netdev(dev); if (err) goto out_free_netdev; BUG_ON(dev->ifindex != LOOPBACK_IFINDEX); 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, }; /* blackhole netdevice */ static netdev_tx_t blackhole_netdev_xmit(struct sk_buff *skb, struct net_device *dev) { kfree_skb(skb); net_warn_ratelimited("%s(): Dropping skb.\n", __func__); return NETDEV_TX_OK; } static const struct net_device_ops blackhole_netdev_ops = { .ndo_start_xmit = blackhole_netdev_xmit, }; /* This is a dst-dummy device used specifically for invalidated * DSTs and unlike loopback, this is not per-ns. */ static void blackhole_netdev_setup(struct net_device *dev) { gen_lo_setup(dev, ETH_MIN_MTU, NULL, NULL, &blackhole_netdev_ops, NULL); } /* Setup and register the blackhole_netdev. */ static int __init blackhole_netdev_init(void) { blackhole_netdev = alloc_netdev(0, "blackhole_dev", NET_NAME_UNKNOWN, blackhole_netdev_setup); if (!blackhole_netdev) return -ENOMEM; rtnl_lock(); dev_init_scheduler(blackhole_netdev); dev_activate(blackhole_netdev); rtnl_unlock(); blackhole_netdev->flags |= IFF_UP | IFF_RUNNING; dev_net_set(blackhole_netdev, &init_net); return 0; } device_initcall(blackhole_netdev_init);