Linux kernel mirror (for testing)
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1// SPDX-License-Identifier: GPL-2.0-or-later
2/*
3 * INET An implementation of the TCP/IP protocol suite for the LINUX
4 * operating system. INET is implemented using the BSD Socket
5 * 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 08/16/93
10 *
11 * Authors: Ross Biro
12 * Fred N. van Kempen, <waltje@uWalt.NL.Mugnet.ORG>
13 * Donald Becker, <becker@scyld.com>
14 *
15 * Alan Cox : Fixed oddments for NET3.014
16 * Alan Cox : Rejig for NET3.029 snap #3
17 * Alan Cox : Fixed NET3.029 bugs and sped up
18 * Larry McVoy : Tiny tweak to double performance
19 * Alan Cox : Backed out LMV's tweak - the linux mm
20 * can't take it...
21 * Michael Griffith: Don't bother computing the checksums
22 * on packets received on the loopback
23 * interface.
24 * Alexey Kuznetsov: Potential hang under some extreme
25 * 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/sock.h>
48#include <net/checksum.h>
49#include <linux/if_ether.h> /* For the statistics structure. */
50#include <linux/if_arp.h> /* For ARPHRD_ETHER */
51#include <linux/ip.h>
52#include <linux/tcp.h>
53#include <linux/percpu.h>
54#include <linux/net_tstamp.h>
55#include <net/net_namespace.h>
56#include <linux/u64_stats_sync.h>
57
58/* The higher levels take care of making this non-reentrant (it's
59 * called with bh's disabled).
60 */
61static netdev_tx_t loopback_xmit(struct sk_buff *skb,
62 struct net_device *dev)
63{
64 struct pcpu_lstats *lb_stats;
65 int len;
66
67 skb_tx_timestamp(skb);
68
69 /* do not fool net_timestamp_check() with various clock bases */
70 skb->tstamp = 0;
71
72 skb_orphan(skb);
73
74 /* Before queueing this packet to netif_rx(),
75 * make sure dst is refcounted.
76 */
77 skb_dst_force(skb);
78
79 skb->protocol = eth_type_trans(skb, dev);
80
81 /* it's OK to use per_cpu_ptr() because BHs are off */
82 lb_stats = this_cpu_ptr(dev->lstats);
83
84 len = skb->len;
85 if (likely(netif_rx(skb) == NET_RX_SUCCESS)) {
86 u64_stats_update_begin(&lb_stats->syncp);
87 lb_stats->bytes += len;
88 lb_stats->packets++;
89 u64_stats_update_end(&lb_stats->syncp);
90 }
91
92 return NETDEV_TX_OK;
93}
94
95static void loopback_get_stats64(struct net_device *dev,
96 struct rtnl_link_stats64 *stats)
97{
98 u64 bytes = 0;
99 u64 packets = 0;
100 int i;
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_irq(&lb_stats->syncp);
110 tbytes = lb_stats->bytes;
111 tpackets = lb_stats->packets;
112 } while (u64_stats_fetch_retry_irq(&lb_stats->syncp, start));
113 bytes += tbytes;
114 packets += tpackets;
115 }
116 stats->rx_packets = packets;
117 stats->tx_packets = packets;
118 stats->rx_bytes = bytes;
119 stats->tx_bytes = bytes;
120}
121
122static u32 always_on(struct net_device *dev)
123{
124 return 1;
125}
126
127static const struct ethtool_ops loopback_ethtool_ops = {
128 .get_link = always_on,
129 .get_ts_info = ethtool_op_get_ts_info,
130};
131
132static int loopback_dev_init(struct net_device *dev)
133{
134 dev->lstats = netdev_alloc_pcpu_stats(struct pcpu_lstats);
135 if (!dev->lstats)
136 return -ENOMEM;
137 return 0;
138}
139
140static void loopback_dev_free(struct net_device *dev)
141{
142 dev_net(dev)->loopback_dev = NULL;
143 free_percpu(dev->lstats);
144}
145
146static const struct net_device_ops loopback_ops = {
147 .ndo_init = loopback_dev_init,
148 .ndo_start_xmit = loopback_xmit,
149 .ndo_get_stats64 = loopback_get_stats64,
150 .ndo_set_mac_address = eth_mac_addr,
151};
152
153/* The loopback device is special. There is only one instance
154 * per network namespace.
155 */
156static void loopback_setup(struct net_device *dev)
157{
158 dev->mtu = 64 * 1024;
159 dev->hard_header_len = ETH_HLEN; /* 14 */
160 dev->min_header_len = ETH_HLEN; /* 14 */
161 dev->addr_len = ETH_ALEN; /* 6 */
162 dev->type = ARPHRD_LOOPBACK; /* 0x0001*/
163 dev->flags = IFF_LOOPBACK;
164 dev->priv_flags |= IFF_LIVE_ADDR_CHANGE | IFF_NO_QUEUE;
165 netif_keep_dst(dev);
166 dev->hw_features = NETIF_F_GSO_SOFTWARE;
167 dev->features = NETIF_F_SG | NETIF_F_FRAGLIST
168 | NETIF_F_GSO_SOFTWARE
169 | NETIF_F_HW_CSUM
170 | NETIF_F_RXCSUM
171 | NETIF_F_SCTP_CRC
172 | NETIF_F_HIGHDMA
173 | NETIF_F_LLTX
174 | NETIF_F_NETNS_LOCAL
175 | NETIF_F_VLAN_CHALLENGED
176 | NETIF_F_LOOPBACK;
177 dev->ethtool_ops = &loopback_ethtool_ops;
178 dev->header_ops = ð_header_ops;
179 dev->netdev_ops = &loopback_ops;
180 dev->needs_free_netdev = true;
181 dev->priv_destructor = loopback_dev_free;
182}
183
184/* Setup and register the loopback device. */
185static __net_init int loopback_net_init(struct net *net)
186{
187 struct net_device *dev;
188 int err;
189
190 err = -ENOMEM;
191 dev = alloc_netdev(0, "lo", NET_NAME_UNKNOWN, loopback_setup);
192 if (!dev)
193 goto out;
194
195 dev_net_set(dev, net);
196 err = register_netdev(dev);
197 if (err)
198 goto out_free_netdev;
199
200 BUG_ON(dev->ifindex != LOOPBACK_IFINDEX);
201 net->loopback_dev = dev;
202 return 0;
203
204out_free_netdev:
205 free_netdev(dev);
206out:
207 if (net_eq(net, &init_net))
208 panic("loopback: Failed to register netdevice: %d\n", err);
209 return err;
210}
211
212/* Registered in net/core/dev.c */
213struct pernet_operations __net_initdata loopback_net_ops = {
214 .init = loopback_net_init,
215};