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
);
80 if (skb_is_gso(skb
)) {
81 BUG_ON(skb
->protocol
!= htons(ETH_P_IP
));
82 BUG_ON(ip_hdr(skb
)->protocol
!= IPPROTO_TCP
);
84 emulate_large_send_offload(skb
);
88 dev
->last_rx
= jiffies
;
90 /* it's OK to use per_cpu_ptr() because BHs are off */
91 pcpu_lstats
= dev
->ml_priv
;
92 lb_stats
= per_cpu_ptr(pcpu_lstats
, smp_processor_id());
93 lb_stats
->bytes
+= skb
->len
;
101 static struct net_device_stats
*get_stats(struct net_device
*dev
)
103 const struct pcpu_lstats
*pcpu_lstats
;
104 struct net_device_stats
*stats
= &dev
->stats
;
105 unsigned long bytes
= 0;
106 unsigned long packets
= 0;
109 pcpu_lstats
= dev
->ml_priv
;
110 for_each_possible_cpu(i
) {
111 const struct pcpu_lstats
*lb_stats
;
113 lb_stats
= per_cpu_ptr(pcpu_lstats
, i
);
114 bytes
+= lb_stats
->bytes
;
115 packets
+= lb_stats
->packets
;
117 stats
->rx_packets
= packets
;
118 stats
->tx_packets
= packets
;
119 stats
->rx_bytes
= bytes
;
120 stats
->tx_bytes
= bytes
;
124 static u32
always_on(struct net_device
*dev
)
129 static const struct ethtool_ops loopback_ethtool_ops
= {
130 .get_link
= always_on
,
131 .set_tso
= ethtool_op_set_tso
,
132 .get_tx_csum
= always_on
,
134 .get_rx_csum
= always_on
,
137 static int loopback_dev_init(struct net_device
*dev
)
139 struct pcpu_lstats
*lstats
;
141 lstats
= alloc_percpu(struct pcpu_lstats
);
145 dev
->ml_priv
= lstats
;
149 static void loopback_dev_free(struct net_device
*dev
)
151 struct pcpu_lstats
*lstats
= dev
->ml_priv
;
158 * The loopback device is special. There is only one instance
159 * per network namespace.
161 static void loopback_setup(struct net_device
*dev
)
163 dev
->get_stats
= &get_stats
;
164 dev
->mtu
= (16 * 1024) + 20 + 20 + 12;
165 dev
->hard_start_xmit
= loopback_xmit
;
166 dev
->hard_header_len
= ETH_HLEN
; /* 14 */
167 dev
->addr_len
= ETH_ALEN
; /* 6 */
168 dev
->tx_queue_len
= 0;
169 dev
->type
= ARPHRD_LOOPBACK
; /* 0x0001*/
170 dev
->flags
= IFF_LOOPBACK
;
171 dev
->features
= NETIF_F_SG
| NETIF_F_FRAGLIST
176 | NETIF_F_NETNS_LOCAL
;
177 dev
->ethtool_ops
= &loopback_ethtool_ops
;
178 dev
->header_ops
= ð_header_ops
;
179 dev
->init
= loopback_dev_init
;
180 dev
->destructor
= loopback_dev_free
;
183 /* Setup and register the loopback device. */
184 static __net_init
int loopback_net_init(struct net
*net
)
186 struct net_device
*dev
;
190 dev
= alloc_netdev(0, "lo", loopback_setup
);
194 dev_net_set(dev
, net
);
195 err
= register_netdev(dev
);
197 goto out_free_netdev
;
199 net
->loopback_dev
= dev
;
206 if (net
== &init_net
)
207 panic("loopback: Failed to register netdevice: %d\n", err
);
211 static __net_exit
void loopback_net_exit(struct net
*net
)
213 struct net_device
*dev
= net
->loopback_dev
;
215 unregister_netdev(dev
);
218 static struct pernet_operations __net_initdata loopback_net_ops
= {
219 .init
= loopback_net_init
,
220 .exit
= loopback_net_exit
,
223 static int __init
loopback_init(void)
225 return register_pernet_device(&loopback_net_ops
);
228 /* Loopback is special. It should be initialized before any other network
229 * device and network subsystem.
231 fs_initcall(loopback_init
);