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/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
61static DEFINE_PER_CPU(struct net_device_stats, loopback_stats);
62
63#define LOOPBACK_OVERHEAD (128 + MAX_HEADER + 16 + 16)
64
65/* KISS: just allocate small chunks and copy bits.
66 *
67 * So, in fact, this is documentation, explaining what we expect
68 * of largesending device modulo TCP checksum, which is ignored for loopback.
69 */
70
71#ifdef LOOPBACK_TSO
72static void emulate_large_send_offload(struct sk_buff *skb)
73{
74 struct iphdr *iph = skb->nh.iph;
75 struct tcphdr *th = (struct tcphdr*)(skb->nh.raw + (iph->ihl * 4));
76 unsigned int doffset = (iph->ihl + th->doff) * 4;
77 unsigned int mtu = skb_shinfo(skb)->tso_size + doffset;
78 unsigned int offset = 0;
79 u32 seq = ntohl(th->seq);
80 u16 id = ntohs(iph->id);
81
82 while (offset + doffset < skb->len) {
83 unsigned int frag_size = min(mtu, skb->len - offset) - doffset;
84 struct sk_buff *nskb = alloc_skb(mtu + 32, GFP_ATOMIC);
85
86 if (!nskb)
87 break;
88 skb_reserve(nskb, 32);
89 nskb->mac.raw = nskb->data - 14;
90 nskb->nh.raw = nskb->data;
91 iph = nskb->nh.iph;
92 memcpy(nskb->data, skb->nh.raw, doffset);
93 if (skb_copy_bits(skb,
94 doffset + offset,
95 nskb->data + doffset,
96 frag_size))
97 BUG();
98 skb_put(nskb, doffset + frag_size);
99 nskb->ip_summed = CHECKSUM_UNNECESSARY;
100 nskb->dev = skb->dev;
101 nskb->priority = skb->priority;
102 nskb->protocol = skb->protocol;
103 nskb->dst = dst_clone(skb->dst);
104 memcpy(nskb->cb, skb->cb, sizeof(skb->cb));
105 nskb->pkt_type = skb->pkt_type;
106
107 th = (struct tcphdr*)(nskb->nh.raw + iph->ihl*4);
108 iph->tot_len = htons(frag_size + doffset);
109 iph->id = htons(id);
110 iph->check = 0;
111 iph->check = ip_fast_csum((unsigned char *) iph, iph->ihl);
112 th->seq = htonl(seq);
113 if (offset + doffset + frag_size < skb->len)
114 th->fin = th->psh = 0;
115 netif_rx(nskb);
116 offset += frag_size;
117 seq += frag_size;
118 id++;
119 }
120
121 dev_kfree_skb(skb);
122}
123#endif /* LOOPBACK_TSO */
124
125/*
126 * The higher levels take care of making this non-reentrant (it's
127 * called with bh's disabled).
128 */
129static int loopback_xmit(struct sk_buff *skb, struct net_device *dev)
130{
131 struct net_device_stats *lb_stats;
132
133 skb_orphan(skb);
134
135 skb->protocol = eth_type_trans(skb,dev);
136 skb->dev = dev;
137#ifndef LOOPBACK_MUST_CHECKSUM
138 skb->ip_summed = CHECKSUM_UNNECESSARY;
139#endif
140
141#ifdef LOOPBACK_TSO
142 if (skb_shinfo(skb)->tso_size) {
143 BUG_ON(skb->protocol != htons(ETH_P_IP));
144 BUG_ON(skb->nh.iph->protocol != IPPROTO_TCP);
145
146 emulate_large_send_offload(skb);
147 return 0;
148 }
149#endif
150 dev->last_rx = jiffies;
151
152 lb_stats = &per_cpu(loopback_stats, get_cpu());
153 lb_stats->rx_bytes += skb->len;
154 lb_stats->tx_bytes = lb_stats->rx_bytes;
155 lb_stats->rx_packets++;
156 lb_stats->tx_packets = lb_stats->rx_packets;
157 put_cpu();
158
159 netif_rx(skb);
160
161 return(0);
162}
163
164static struct net_device_stats *get_stats(struct net_device *dev)
165{
166 struct net_device_stats *stats = dev->priv;
167 int i;
168
169 if (!stats) {
170 return NULL;
171 }
172
173 memset(stats, 0, sizeof(struct net_device_stats));
174
175 for (i=0; i < NR_CPUS; i++) {
176 struct net_device_stats *lb_stats;
177
178 if (!cpu_possible(i))
179 continue;
180 lb_stats = &per_cpu(loopback_stats, i);
181 stats->rx_bytes += lb_stats->rx_bytes;
182 stats->tx_bytes += lb_stats->tx_bytes;
183 stats->rx_packets += lb_stats->rx_packets;
184 stats->tx_packets += lb_stats->tx_packets;
185 }
186
187 return stats;
188}
189
190static u32 loopback_get_link(struct net_device *dev)
191{
192 return 1;
193}
194
195static struct ethtool_ops loopback_ethtool_ops = {
196 .get_link = loopback_get_link,
197 .get_tso = ethtool_op_get_tso,
198 .set_tso = ethtool_op_set_tso,
199};
200
201struct net_device loopback_dev = {
202 .name = "lo",
203 .mtu = (16 * 1024) + 20 + 20 + 12,
204 .hard_start_xmit = loopback_xmit,
205 .hard_header = eth_header,
206 .hard_header_cache = eth_header_cache,
207 .header_cache_update = eth_header_cache_update,
208 .hard_header_len = ETH_HLEN, /* 14 */
209 .addr_len = ETH_ALEN, /* 6 */
210 .tx_queue_len = 0,
211 .type = ARPHRD_LOOPBACK, /* 0x0001*/
212 .rebuild_header = eth_rebuild_header,
213 .flags = IFF_LOOPBACK,
214 .features = NETIF_F_SG | NETIF_F_FRAGLIST
215#ifdef LOOPBACK_TSO
216 | NETIF_F_TSO
217#endif
218 | NETIF_F_NO_CSUM | NETIF_F_HIGHDMA
219 | NETIF_F_LLTX,
220 .ethtool_ops = &loopback_ethtool_ops,
221};
222
223/* Setup and register the loopback device. */
224int __init loopback_init(void)
225{
226 struct net_device_stats *stats;
227
228 /* Can survive without statistics */
229 stats = kmalloc(sizeof(struct net_device_stats), GFP_KERNEL);
230 if (stats) {
231 memset(stats, 0, sizeof(struct net_device_stats));
232 loopback_dev.priv = stats;
233 loopback_dev.get_stats = &get_stats;
234 }
235
236 return register_netdev(&loopback_dev);
237};
238
239EXPORT_SYMBOL(loopback_dev);