// 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)
{
struct pcpu_lstats *lb_stats;
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);
/* 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 void 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_irq(&lb_stats->syncp);
tbytes = lb_stats->bytes;
tpackets = lb_stats->packets;
} while (u64_stats_fetch_retry_irq(&lb_stats->syncp, start));
bytes += tbytes;
packets += tpackets;
}
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);
