1/*
2 * INET An implementation of the TCP/IP protocol suite for the LINUX
3 * operating system. INET is implemented using the BSD Socket
4 * interface as the means of communication with the user level.
5 *
6 * Pseudo-driver for the loopback interface.
7 *
8 * Version: @(#)loopback.c 1.0.4b 08/16/93
9 *
10 * Authors: Ross Biro
11 * Fred N. van Kempen, <waltje@uWalt.NL.Mugnet.ORG>
12 * Donald Becker, <becker@scyld.com>
13 *
14 * Alan Cox : Fixed oddments for NET3.014
15 * Alan Cox : Rejig for NET3.029 snap #3
16 * Alan Cox : Fixed NET3.029 bugs and sped up
17 * Larry McVoy : Tiny tweak to double performance
18 * Alan Cox : Backed out LMV's tweak - the linux mm
19 * can't take it...
20 * Michael Griffith: Don't bother computing the checksums
21 * on packets received on the loopback
22 * interface.
23 * Alexey Kuznetsov: Potential hang under some extreme
24 * cases removed.
25 *
26 * This program is free software; you can redistribute it and/or
27 * modify it under the terms of the GNU General Public License
28 * as published by the Free Software Foundation; either version
29 * 2 of the License, or (at your option) any later version.
30 */
31#include <linux/kernel.h>
32#include <linux/jiffies.h>
33#include <linux/module.h>
34#include <linux/interrupt.h>
35#include <linux/fs.h>
36#include <linux/types.h>
37#include <linux/string.h>
38#include <linux/socket.h>
39#include <linux/errno.h>
40#include <linux/fcntl.h>
41#include <linux/in.h>
42
43#include <linux/uaccess.h>
44#include <linux/io.h>
45
46#include <linux/inet.h>
47#include <linux/netdevice.h>
48#include <linux/etherdevice.h>
49#include <linux/skbuff.h>
50#include <linux/ethtool.h>
51#include <net/sock.h>
52#include <net/checksum.h>
53#include <linux/if_ether.h> /* For the statistics structure. */
54#include <linux/if_arp.h> /* For ARPHRD_ETHER */
55#include <linux/ip.h>
56#include <linux/tcp.h>
57#include <linux/percpu.h>
58#include <linux/net_tstamp.h>
59#include <net/net_namespace.h>
60#include <linux/u64_stats_sync.h>
61
62/* The higher levels take care of making this non-reentrant (it's
63 * called with bh's disabled).
64 */
65static netdev_tx_t loopback_xmit(struct sk_buff *skb,
66 struct net_device *dev)
67{
68 struct pcpu_lstats *lb_stats;
69 int len;
70
71 skb_tx_timestamp(skb);
72
73 /* do not fool net_timestamp_check() with various clock bases */
74 skb->tstamp = 0;
75
76 skb_orphan(skb);
77
78 /* Before queueing this packet to netif_rx(),
79 * make sure dst is refcounted.
80 */
81 skb_dst_force(skb);
82
83 skb->protocol = eth_type_trans(skb, dev);
84
85 /* it's OK to use per_cpu_ptr() because BHs are off */
86 lb_stats = this_cpu_ptr(dev->lstats);
87
88 len = skb->len;
89 if (likely(netif_rx(skb) == NET_RX_SUCCESS)) {
90 u64_stats_update_begin(&lb_stats->syncp);
91 lb_stats->bytes += len;
92 lb_stats->packets++;
93 u64_stats_update_end(&lb_stats->syncp);
94 }
95
96 return NETDEV_TX_OK;
97}
98
99static void loopback_get_stats64(struct net_device *dev,
100 struct rtnl_link_stats64 *stats)
101{
102 u64 bytes = 0;
103 u64 packets = 0;
104 int i;
105
106 for_each_possible_cpu(i) {
107 const struct pcpu_lstats *lb_stats;
108 u64 tbytes, tpackets;
109 unsigned int start;
110
111 lb_stats = per_cpu_ptr(dev->lstats, i);
112 do {
113 start = u64_stats_fetch_begin_irq(&lb_stats->syncp);
114 tbytes = lb_stats->bytes;
115 tpackets = lb_stats->packets;
116 } while (u64_stats_fetch_retry_irq(&lb_stats->syncp, start));
117 bytes += tbytes;
118 packets += tpackets;
119 }
120 stats->rx_packets = packets;
121 stats->tx_packets = packets;
122 stats->rx_bytes = bytes;
123 stats->tx_bytes = bytes;
124}
125
126static u32 always_on(struct net_device *dev)
127{
128 return 1;
129}
130
131static int loopback_get_ts_info(struct net_device *netdev,
132 struct ethtool_ts_info *ts_info)
133{
134 ts_info->so_timestamping = SOF_TIMESTAMPING_TX_SOFTWARE |
135 SOF_TIMESTAMPING_RX_SOFTWARE |
136 SOF_TIMESTAMPING_SOFTWARE;
137
138 ts_info->phc_index = -1;
139
140 return 0;
141};
142
143static const struct ethtool_ops loopback_ethtool_ops = {
144 .get_link = always_on,
145 .get_ts_info = loopback_get_ts_info,
146};
147
148static int loopback_dev_init(struct net_device *dev)
149{
150 dev->lstats = netdev_alloc_pcpu_stats(struct pcpu_lstats);
151 if (!dev->lstats)
152 return -ENOMEM;
153 return 0;
154}
155
156static void loopback_dev_free(struct net_device *dev)
157{
158 dev_net(dev)->loopback_dev = NULL;
159 free_percpu(dev->lstats);
160}
161
162static const struct net_device_ops loopback_ops = {
163 .ndo_init = loopback_dev_init,
164 .ndo_start_xmit = loopback_xmit,
165 .ndo_get_stats64 = loopback_get_stats64,
166 .ndo_set_mac_address = eth_mac_addr,
167};
168
169/* The loopback device is special. There is only one instance
170 * per network namespace.
171 */
172static void loopback_setup(struct net_device *dev)
173{
174 dev->mtu = 64 * 1024;
175 dev->hard_header_len = ETH_HLEN; /* 14 */
176 dev->min_header_len = ETH_HLEN; /* 14 */
177 dev->addr_len = ETH_ALEN; /* 6 */
178 dev->type = ARPHRD_LOOPBACK; /* 0x0001*/
179 dev->flags = IFF_LOOPBACK;
180 dev->priv_flags |= IFF_LIVE_ADDR_CHANGE | IFF_NO_QUEUE;
181 netif_keep_dst(dev);
182 dev->hw_features = NETIF_F_GSO_SOFTWARE;
183 dev->features = NETIF_F_SG | NETIF_F_FRAGLIST
184 | NETIF_F_GSO_SOFTWARE
185 | NETIF_F_HW_CSUM
186 | NETIF_F_RXCSUM
187 | NETIF_F_SCTP_CRC
188 | NETIF_F_HIGHDMA
189 | NETIF_F_LLTX
190 | NETIF_F_NETNS_LOCAL
191 | NETIF_F_VLAN_CHALLENGED
192 | NETIF_F_LOOPBACK;
193 dev->ethtool_ops = &loopback_ethtool_ops;
194 dev->header_ops = &eth_header_ops;
195 dev->netdev_ops = &loopback_ops;
196 dev->needs_free_netdev = true;
197 dev->priv_destructor = loopback_dev_free;
198}
199
200/* Setup and register the loopback device. */
201static __net_init int loopback_net_init(struct net *net)
202{
203 struct net_device *dev;
204 int err;
205
206 err = -ENOMEM;
207 dev = alloc_netdev(0, "lo", NET_NAME_UNKNOWN, loopback_setup);
208 if (!dev)
209 goto out;
210
211 dev_net_set(dev, net);
212 err = register_netdev(dev);
213 if (err)
214 goto out_free_netdev;
215
216 BUG_ON(dev->ifindex != LOOPBACK_IFINDEX);
217 net->loopback_dev = dev;
218 return 0;
219
220out_free_netdev:
221 free_netdev(dev);
222out:
223 if (net_eq(net, &init_net))
224 panic("loopback: Failed to register netdevice: %d\n", err);
225 return err;
226}
227
228/* Registered in net/core/dev.c */
229struct pernet_operations __net_initdata loopback_net_ops = {
230 .init = loopback_net_init,
231};
232