projects/linux·blob v2.6.21 · refs

239 lines · 6.3 KiB

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, <[email protected]>
12 * Donald Becker, <[email protected]>
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
61struct pcpu_lstats {
62 unsigned long packets;
63 unsigned long bytes;
64};
65static DEFINE_PER_CPU(struct pcpu_lstats, pcpu_lstats);
66
67#define LOOPBACK_OVERHEAD (128 + MAX_HEADER + 16 + 16)
68
69/* KISS: just allocate small chunks and copy bits.
70 *
71 * So, in fact, this is documentation, explaining what we expect
72 * of largesending device modulo TCP checksum, which is ignored for loopback.
73 */
74
75#ifdef LOOPBACK_TSO
76static void emulate_large_send_offload(struct sk_buff *skb)
77{
78 struct iphdr *iph = skb->nh.iph;
79 struct tcphdr *th = (struct tcphdr*)(skb->nh.raw + (iph->ihl * 4));
80 unsigned int doffset = (iph->ihl + th->doff) * 4;
81 unsigned int mtu = skb_shinfo(skb)->gso_size + doffset;
82 unsigned int offset = 0;
83 u32 seq = ntohl(th->seq);
84 u16 id = ntohs(iph->id);
85
86 while (offset + doffset < skb->len) {
87 unsigned int frag_size = min(mtu, skb->len - offset) - doffset;
88 struct sk_buff *nskb = alloc_skb(mtu + 32, GFP_ATOMIC);
89
90 if (!nskb)
91 break;
92 skb_reserve(nskb, 32);
93 nskb->mac.raw = nskb->data - 14;
94 nskb->nh.raw = nskb->data;
95 iph = nskb->nh.iph;
96 memcpy(nskb->data, skb->nh.raw, doffset);
97 if (skb_copy_bits(skb,
98 doffset + offset,
99 nskb->data + doffset,
100 frag_size))
101 BUG();
102 skb_put(nskb, doffset + frag_size);
103 nskb->ip_summed = CHECKSUM_UNNECESSARY;
104 nskb->dev = skb->dev;
105 nskb->priority = skb->priority;
106 nskb->protocol = skb->protocol;
107 nskb->dst = dst_clone(skb->dst);
108 memcpy(nskb->cb, skb->cb, sizeof(skb->cb));
109 nskb->pkt_type = skb->pkt_type;
110
111 th = (struct tcphdr*)(nskb->nh.raw + iph->ihl*4);
112 iph->tot_len = htons(frag_size + doffset);
113 iph->id = htons(id);
114 iph->check = 0;
115 iph->check = ip_fast_csum((unsigned char *) iph, iph->ihl);
116 th->seq = htonl(seq);
117 if (offset + doffset + frag_size < skb->len)
118 th->fin = th->psh = 0;
119 netif_rx(nskb);
120 offset += frag_size;
121 seq += frag_size;
122 id++;
123 }
124
125 dev_kfree_skb(skb);
126}
127#endif /* LOOPBACK_TSO */
128
129/*
130 * The higher levels take care of making this non-reentrant (it's
131 * called with bh's disabled).
132 */
133static int loopback_xmit(struct sk_buff *skb, struct net_device *dev)
134{
135 struct pcpu_lstats *lb_stats;
136
137 skb_orphan(skb);
138
139 skb->protocol = eth_type_trans(skb,dev);
140 skb->dev = dev;
141#ifndef LOOPBACK_MUST_CHECKSUM
142 skb->ip_summed = CHECKSUM_UNNECESSARY;
143#endif
144
145#ifdef LOOPBACK_TSO
146 if (skb_is_gso(skb)) {
147 BUG_ON(skb->protocol != htons(ETH_P_IP));
148 BUG_ON(skb->nh.iph->protocol != IPPROTO_TCP);
149
150 emulate_large_send_offload(skb);
151 return 0;
152 }
153#endif
154 dev->last_rx = jiffies;
155
156 /* it's OK to use __get_cpu_var() because BHs are off */
157 lb_stats = &__get_cpu_var(pcpu_lstats);
158 lb_stats->bytes += skb->len;
159 lb_stats->packets++;
160
161 netif_rx(skb);
162
163 return 0;
164}
165
166static struct net_device_stats loopback_stats;
167
168static struct net_device_stats *get_stats(struct net_device *dev)
169{
170 struct net_device_stats *stats = &loopback_stats;
171 unsigned long bytes = 0;
172 unsigned long packets = 0;
173 int i;
174
175 for_each_possible_cpu(i) {
176 const struct pcpu_lstats *lb_stats;
177
178 lb_stats = &per_cpu(pcpu_lstats, i);
179 bytes += lb_stats->bytes;
180 packets += lb_stats->packets;
181 }
182 stats->rx_packets = packets;
183 stats->tx_packets = packets;
184 stats->rx_bytes = bytes;
185 stats->tx_bytes = bytes;
186 return stats;
187}
188
189static u32 always_on(struct net_device *dev)
190{
191 return 1;
192}
193
194static const struct ethtool_ops loopback_ethtool_ops = {
195 .get_link = always_on,
196 .get_tso = ethtool_op_get_tso,
197 .set_tso = ethtool_op_set_tso,
198 .get_tx_csum = always_on,
199 .get_sg = always_on,
200 .get_rx_csum = always_on,
201};
202
203/*
204 * The loopback device is special. There is only one instance and
205 * it is statically allocated. Don't do this for other devices.
206 */
207struct net_device loopback_dev = {
208 .name = "lo",
209 .get_stats = &get_stats,
210 .priv = &loopback_stats,
211 .mtu = (16 * 1024) + 20 + 20 + 12,
212 .hard_start_xmit = loopback_xmit,
213 .hard_header = eth_header,
214 .hard_header_cache = eth_header_cache,
215 .header_cache_update = eth_header_cache_update,
216 .hard_header_len = ETH_HLEN, /* 14 */
217 .addr_len = ETH_ALEN, /* 6 */
218 .tx_queue_len = 0,
219 .type = ARPHRD_LOOPBACK, /* 0x0001*/
220 .rebuild_header = eth_rebuild_header,
221 .flags = IFF_LOOPBACK,
222 .features = NETIF_F_SG | NETIF_F_FRAGLIST
223#ifdef LOOPBACK_TSO
224 | NETIF_F_TSO
225#endif
226 | NETIF_F_NO_CSUM | NETIF_F_HIGHDMA
227 | NETIF_F_LLTX,
228 .ethtool_ops = &loopback_ethtool_ops,
229};
230
231/* Setup and register the loopback device. */
232static int __init loopback_init(void)
233{
234 return register_netdev(&loopback_dev);
235};
236
237module_init(loopback_init);
238
239EXPORT_SYMBOL(loopback_dev);