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.
6 * Pseudo-driver for the loopback interface.
8 * Version: @(#)loopback.c 1.0.4b 08/16/93
11 * Fred N. van Kempen, <waltje@uWalt.NL.Mugnet.ORG>
12 * Donald Becker, <becker@scyld.com>
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
20 * Michael Griffith: Don't bother computing the checksums
21 * on packets received on the loopback
23 * Alexey Kuznetsov: Potential hang under some extreme
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.
31 #include <linux/kernel.h>
32 #include <linux/jiffies.h>
33 #include <linux/module.h>
34 #include <linux/interrupt.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>
42 #include <linux/init.h>
44 #include <asm/system.h>
45 #include <asm/uaccess.h>
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>
54 #include <net/checksum.h>
55 #include <linux/if_ether.h> /* For the statistics structure. */
56 #include <linux/if_arp.h> /* For ARPHRD_ETHER */
58 #include <linux/tcp.h>
59 #include <linux/percpu.h>
60 #include <net/net_namespace.h>
63 unsigned long packets;
68 * The higher levels take care of making this non-reentrant (it's
69 * called with bh's disabled).
71 static int loopback_xmit(struct sk_buff *skb, struct net_device *dev)
73 struct pcpu_lstats *pcpu_lstats, *lb_stats;
77 skb->protocol = eth_type_trans(skb,dev);
78 #ifndef LOOPBACK_MUST_CHECKSUM
79 skb->ip_summed = CHECKSUM_UNNECESSARY;
83 if (skb_is_gso(skb)) {
84 BUG_ON(skb->protocol != htons(ETH_P_IP));
85 BUG_ON(ip_hdr(skb)->protocol != IPPROTO_TCP);
87 emulate_large_send_offload(skb);
91 dev->last_rx = jiffies;
93 /* it's OK to use per_cpu_ptr() because BHs are off */
94 pcpu_lstats = dev->ml_priv;
95 lb_stats = per_cpu_ptr(pcpu_lstats, smp_processor_id());
96 lb_stats->bytes += skb->len;
104 static struct net_device_stats *get_stats(struct net_device *dev)
106 const struct pcpu_lstats *pcpu_lstats;
107 struct net_device_stats *stats = &dev->stats;
108 unsigned long bytes = 0;
109 unsigned long packets = 0;
112 pcpu_lstats = dev->ml_priv;
113 for_each_possible_cpu(i) {
114 const struct pcpu_lstats *lb_stats;
116 lb_stats = per_cpu_ptr(pcpu_lstats, i);
117 bytes += lb_stats->bytes;
118 packets += lb_stats->packets;
120 stats->rx_packets = packets;
121 stats->tx_packets = packets;
122 stats->rx_bytes = bytes;
123 stats->tx_bytes = bytes;
127 static u32 always_on(struct net_device *dev)
132 static const struct ethtool_ops loopback_ethtool_ops = {
133 .get_link = always_on,
134 .set_tso = ethtool_op_set_tso,
135 .get_tx_csum = always_on,
137 .get_rx_csum = always_on,
140 static int loopback_dev_init(struct net_device *dev)
142 struct pcpu_lstats *lstats;
144 lstats = alloc_percpu(struct pcpu_lstats);
148 dev->ml_priv = lstats;
152 static void loopback_dev_free(struct net_device *dev)
154 struct pcpu_lstats *lstats = dev->ml_priv;
161 * The loopback device is special. There is only one instance
162 * per network namespace.
164 static void loopback_setup(struct net_device *dev)
166 dev->get_stats = &get_stats;
167 dev->mtu = (16 * 1024) + 20 + 20 + 12;
168 dev->hard_start_xmit = loopback_xmit;
169 dev->hard_header_len = ETH_HLEN; /* 14 */
170 dev->addr_len = ETH_ALEN; /* 6 */
171 dev->tx_queue_len = 0;
172 dev->type = ARPHRD_LOOPBACK; /* 0x0001*/
173 dev->flags = IFF_LOOPBACK;
174 dev->features = NETIF_F_SG | NETIF_F_FRAGLIST
179 | NETIF_F_NETNS_LOCAL;
180 dev->ethtool_ops = &loopback_ethtool_ops;
181 dev->header_ops = ð_header_ops;
182 dev->init = loopback_dev_init;
183 dev->destructor = loopback_dev_free;
186 /* Setup and register the loopback device. */
187 static __net_init int loopback_net_init(struct net *net)
189 struct net_device *dev;
193 dev = alloc_netdev(0, "lo", loopback_setup);
197 dev_net_set(dev, net);
198 err = register_netdev(dev);
200 goto out_free_netdev;
202 net->loopback_dev = dev;
209 if (net == &init_net)
210 panic("loopback: Failed to register netdevice: %d\n", err);
214 static __net_exit void loopback_net_exit(struct net *net)
216 struct net_device *dev = net->loopback_dev;
218 unregister_netdev(dev);
221 static struct pernet_operations __net_initdata loopback_net_ops = {
222 .init = loopback_net_init,
223 .exit = loopback_net_exit,
226 static int __init loopback_init(void)
228 return register_pernet_device(&loopback_net_ops);
231 /* Loopback is special. It should be initialized before any other network
232 * device and network subsystem.
234 fs_initcall(loopback_init);