// 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, <[email protected]> * Donald Becker, <[email protected]> * * 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/sch_generic.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(…); /* 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) { … } void dev_lstats_read(struct net_device *dev, u64 *packets, u64 *bytes) { … } EXPORT_SYMBOL(…); static void loopback_get_stats64(struct net_device *dev, struct rtnl_link_stats64 *stats) { … } static u32 always_on(struct net_device *dev) { … } static const struct ethtool_ops loopback_ethtool_ops = …; static int loopback_dev_init(struct net_device *dev) { … } static void loopback_dev_free(struct net_device *dev) { … } static const struct net_device_ops loopback_ops = …; 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)) { … } /* The loopback device is special. There is only one instance * per network namespace. */ static void loopback_setup(struct net_device *dev) { … } /* Setup and register the loopback device. */ static __net_init int loopback_net_init(struct net *net) { … } /* Registered in net/core/dev.c */ struct pernet_operations __net_initdata loopback_net_ops = …; /* blackhole netdevice */ static netdev_tx_t blackhole_netdev_xmit(struct sk_buff *skb, struct net_device *dev) { … } static const struct net_device_ops blackhole_netdev_ops = …; /* 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) { … } /* Setup and register the blackhole_netdev. */ static int __init blackhole_netdev_init(void) { … } device_initcall(blackhole_netdev_init);
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