Linux kernel mirror (for testing)
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linux
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/uaccess.h>
45#include <asm/io.h>
46
47#include <linux/inet.h>
48#include <linux/netdevice.h>
49#include <linux/etherdevice.h>
50#include <linux/skbuff.h>
51#include <linux/ethtool.h>
52#include <net/sock.h>
53#include <net/checksum.h>
54#include <linux/if_ether.h> /* For the statistics structure. */
55#include <linux/if_arp.h> /* For ARPHRD_ETHER */
56#include <linux/ip.h>
57#include <linux/tcp.h>
58#include <linux/percpu.h>
59#include <net/net_namespace.h>
60#include <linux/u64_stats_sync.h>
61
62struct pcpu_lstats {
63 u64 packets;
64 u64 bytes;
65 struct u64_stats_sync syncp;
66};
67
68/*
69 * The higher levels take care of making this non-reentrant (it's
70 * called with bh's disabled).
71 */
72static netdev_tx_t loopback_xmit(struct sk_buff *skb,
73 struct net_device *dev)
74{
75 struct pcpu_lstats *lb_stats;
76 int len;
77
78 skb_orphan(skb);
79
80 /* Before queueing this packet to netif_rx(),
81 * make sure dst is refcounted.
82 */
83 skb_dst_force(skb);
84
85 skb->protocol = eth_type_trans(skb, dev);
86
87 /* it's OK to use per_cpu_ptr() because BHs are off */
88 lb_stats = this_cpu_ptr(dev->lstats);
89
90 len = skb->len;
91 if (likely(netif_rx(skb) == NET_RX_SUCCESS)) {
92 u64_stats_update_begin(&lb_stats->syncp);
93 lb_stats->bytes += len;
94 lb_stats->packets++;
95 u64_stats_update_end(&lb_stats->syncp);
96 }
97
98 return NETDEV_TX_OK;
99}
100
101static struct rtnl_link_stats64 *loopback_get_stats64(struct net_device *dev,
102 struct rtnl_link_stats64 *stats)
103{
104 u64 bytes = 0;
105 u64 packets = 0;
106 int i;
107
108 for_each_possible_cpu(i) {
109 const struct pcpu_lstats *lb_stats;
110 u64 tbytes, tpackets;
111 unsigned int start;
112
113 lb_stats = per_cpu_ptr(dev->lstats, i);
114 do {
115 start = u64_stats_fetch_begin_bh(&lb_stats->syncp);
116 tbytes = lb_stats->bytes;
117 tpackets = lb_stats->packets;
118 } while (u64_stats_fetch_retry_bh(&lb_stats->syncp, start));
119 bytes += tbytes;
120 packets += tpackets;
121 }
122 stats->rx_packets = packets;
123 stats->tx_packets = packets;
124 stats->rx_bytes = bytes;
125 stats->tx_bytes = bytes;
126 return stats;
127}
128
129static u32 always_on(struct net_device *dev)
130{
131 return 1;
132}
133
134static const struct ethtool_ops loopback_ethtool_ops = {
135 .get_link = always_on,
136};
137
138static int loopback_dev_init(struct net_device *dev)
139{
140 int i;
141 dev->lstats = alloc_percpu(struct pcpu_lstats);
142 if (!dev->lstats)
143 return -ENOMEM;
144
145 for_each_possible_cpu(i) {
146 struct pcpu_lstats *lb_stats;
147 lb_stats = per_cpu_ptr(dev->lstats, i);
148 u64_stats_init(&lb_stats->syncp);
149 }
150 return 0;
151}
152
153static void loopback_dev_free(struct net_device *dev)
154{
155 dev_net(dev)->loopback_dev = NULL;
156 free_percpu(dev->lstats);
157 free_netdev(dev);
158}
159
160static const struct net_device_ops loopback_ops = {
161 .ndo_init = loopback_dev_init,
162 .ndo_start_xmit= loopback_xmit,
163 .ndo_get_stats64 = loopback_get_stats64,
164};
165
166/*
167 * The loopback device is special. There is only one instance
168 * per network namespace.
169 */
170static void loopback_setup(struct net_device *dev)
171{
172 dev->mtu = 64 * 1024;
173 dev->hard_header_len = ETH_HLEN; /* 14 */
174 dev->addr_len = ETH_ALEN; /* 6 */
175 dev->tx_queue_len = 0;
176 dev->type = ARPHRD_LOOPBACK; /* 0x0001*/
177 dev->flags = IFF_LOOPBACK;
178 dev->priv_flags &= ~IFF_XMIT_DST_RELEASE;
179 dev->hw_features = NETIF_F_ALL_TSO | NETIF_F_UFO;
180 dev->features = NETIF_F_SG | NETIF_F_FRAGLIST
181 | NETIF_F_ALL_TSO
182 | NETIF_F_UFO
183 | NETIF_F_HW_CSUM
184 | NETIF_F_RXCSUM
185 | NETIF_F_HIGHDMA
186 | NETIF_F_LLTX
187 | NETIF_F_NETNS_LOCAL
188 | NETIF_F_VLAN_CHALLENGED
189 | NETIF_F_LOOPBACK;
190 dev->ethtool_ops = &loopback_ethtool_ops;
191 dev->header_ops = ð_header_ops;
192 dev->netdev_ops = &loopback_ops;
193 dev->destructor = loopback_dev_free;
194}
195
196/* Setup and register the loopback device. */
197static __net_init int loopback_net_init(struct net *net)
198{
199 struct net_device *dev;
200 int err;
201
202 err = -ENOMEM;
203 dev = alloc_netdev(0, "lo", loopback_setup);
204 if (!dev)
205 goto out;
206
207 dev_net_set(dev, net);
208 err = register_netdev(dev);
209 if (err)
210 goto out_free_netdev;
211
212 BUG_ON(dev->ifindex != LOOPBACK_IFINDEX);
213 net->loopback_dev = dev;
214 return 0;
215
216
217out_free_netdev:
218 free_netdev(dev);
219out:
220 if (net_eq(net, &init_net))
221 panic("loopback: Failed to register netdevice: %d\n", err);
222 return err;
223}
224
225/* Registered in net/core/dev.c */
226struct pernet_operations __net_initdata loopback_net_ops = {
227 .init = loopback_net_init,
228};