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#include <linux/init.h>
43
44#include <asm/system.h>
45#include <asm/uaccess.h>
46#include <asm/io.h>
47
48#include <linux/inet.h>
49#include <linux/netdevice.h>
50#include <linux/etherdevice.h>
51#include <linux/skbuff.h>
52#include <linux/ethtool.h>
53#include <net/sock.h>
54#include <net/checksum.h>
55#include <linux/if_ether.h>	/* For the statistics structure. */
56#include <linux/if_arp.h>	/* For ARPHRD_ETHER */
57#include <linux/ip.h>
58#include <linux/tcp.h>
59#include <linux/percpu.h>
60#include <net/net_namespace.h>
61#include <linux/u64_stats_sync.h>
62
63struct pcpu_lstats {
64	u64			packets;
65	u64			bytes;
66	struct u64_stats_sync	syncp;
67};
68
69/*
70 * The higher levels take care of making this non-reentrant (it's
71 * called with bh's disabled).
72 */
73static netdev_tx_t loopback_xmit(struct sk_buff *skb,
74				 struct net_device *dev)
75{
76	struct pcpu_lstats *lb_stats;
77	int len;
78
79	skb_orphan(skb);
80
81	skb->protocol = eth_type_trans(skb, dev);
82
83	/* it's OK to use per_cpu_ptr() because BHs are off */
84	lb_stats = this_cpu_ptr(dev->lstats);
85
86	len = skb->len;
87	if (likely(netif_rx(skb) == NET_RX_SUCCESS)) {
88		u64_stats_update_begin(&lb_stats->syncp);
89		lb_stats->bytes += len;
90		lb_stats->packets++;
91		u64_stats_update_end(&lb_stats->syncp);
92	}
93
94	return NETDEV_TX_OK;
95}
96
97static struct rtnl_link_stats64 *loopback_get_stats64(struct net_device *dev,
98						      struct rtnl_link_stats64 *stats)
99{
100	u64 bytes = 0;
101	u64 packets = 0;
102	int i;
103
104	for_each_possible_cpu(i) {
105		const struct pcpu_lstats *lb_stats;
106		u64 tbytes, tpackets;
107		unsigned int start;
108
109		lb_stats = per_cpu_ptr(dev->lstats, i);
110		do {
111			start = u64_stats_fetch_begin(&lb_stats->syncp);
112			tbytes = lb_stats->bytes;
113			tpackets = lb_stats->packets;
114		} while (u64_stats_fetch_retry(&lb_stats->syncp, start));
115		bytes   += tbytes;
116		packets += tpackets;
117	}
118	stats->rx_packets = packets;
119	stats->tx_packets = packets;
120	stats->rx_bytes   = bytes;
121	stats->tx_bytes   = bytes;
122	return stats;
123}
124
125static u32 always_on(struct net_device *dev)
126{
127	return 1;
128}
129
130static const struct ethtool_ops loopback_ethtool_ops = {
131	.get_link		= always_on,
132};
133
134static int loopback_dev_init(struct net_device *dev)
135{
136	dev->lstats = alloc_percpu(struct pcpu_lstats);
137	if (!dev->lstats)
138		return -ENOMEM;
139
140	return 0;
141}
142
143static void loopback_dev_free(struct net_device *dev)
144{
145	free_percpu(dev->lstats);
146	free_netdev(dev);
147}
148
149static const struct net_device_ops loopback_ops = {
150	.ndo_init      = loopback_dev_init,
151	.ndo_start_xmit= loopback_xmit,
152	.ndo_get_stats64 = loopback_get_stats64,
153};
154
155/*
156 * The loopback device is special. There is only one instance
157 * per network namespace.
158 */
159static void loopback_setup(struct net_device *dev)
160{
161	dev->mtu		= (16 * 1024) + 20 + 20 + 12;
162	dev->hard_header_len	= ETH_HLEN;	/* 14	*/
163	dev->addr_len		= ETH_ALEN;	/* 6	*/
164	dev->tx_queue_len	= 0;
165	dev->type		= ARPHRD_LOOPBACK;	/* 0x0001*/
166	dev->flags		= IFF_LOOPBACK;
167	dev->priv_flags	       &= ~IFF_XMIT_DST_RELEASE;
168	dev->hw_features	= NETIF_F_ALL_TSO | NETIF_F_UFO;
169	dev->features 		= NETIF_F_SG | NETIF_F_FRAGLIST
170		| NETIF_F_ALL_TSO
171		| NETIF_F_UFO
172		| NETIF_F_HW_CSUM
173		| NETIF_F_RXCSUM
174		| NETIF_F_HIGHDMA
175		| NETIF_F_LLTX
176		| NETIF_F_NETNS_LOCAL
177		| NETIF_F_VLAN_CHALLENGED
178		| NETIF_F_LOOPBACK;
179	dev->ethtool_ops	= &loopback_ethtool_ops;
180	dev->header_ops		= &eth_header_ops;
181	dev->netdev_ops		= &loopback_ops;
182	dev->destructor		= loopback_dev_free;
183}
184
185/* Setup and register the loopback device. */
186static __net_init int loopback_net_init(struct net *net)
187{
188	struct net_device *dev;
189	int err;
190
191	err = -ENOMEM;
192	dev = alloc_netdev(0, "lo", loopback_setup);
193	if (!dev)
194		goto out;
195
196	dev_net_set(dev, net);
197	err = register_netdev(dev);
198	if (err)
199		goto out_free_netdev;
200
201	net->loopback_dev = dev;
202	return 0;
203
204
205out_free_netdev:
206	free_netdev(dev);
207out:
208	if (net_eq(net, &init_net))
209		panic("loopback: Failed to register netdevice: %d\n", err);
210	return err;
211}
212
213/* Registered in net/core/dev.c */
214struct pernet_operations __net_initdata loopback_net_ops = {
215       .init = loopback_net_init,
216};
217