xref: /openbmc/linux/drivers/net/loopback.c (revision 22246614)
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 #include <net/net_namespace.h>
61 
62 struct pcpu_lstats {
63 	unsigned long packets;
64 	unsigned long bytes;
65 };
66 
67 /* KISS: just allocate small chunks and copy bits.
68  *
69  * So, in fact, this is documentation, explaining what we expect
70  * of largesending device modulo TCP checksum, which is ignored for loopback.
71  */
72 
73 #ifdef LOOPBACK_TSO
74 static void emulate_large_send_offload(struct sk_buff *skb)
75 {
76 	struct iphdr *iph = ip_hdr(skb);
77 	struct tcphdr *th = (struct tcphdr *)(skb_network_header(skb) +
78 					      (iph->ihl * 4));
79 	unsigned int doffset = (iph->ihl + th->doff) * 4;
80 	unsigned int mtu = skb_shinfo(skb)->gso_size + doffset;
81 	unsigned int offset = 0;
82 	u32 seq = ntohl(th->seq);
83 	u16 id  = ntohs(iph->id);
84 
85 	while (offset + doffset < skb->len) {
86 		unsigned int frag_size = min(mtu, skb->len - offset) - doffset;
87 		struct sk_buff *nskb = alloc_skb(mtu + 32, GFP_ATOMIC);
88 
89 		if (!nskb)
90 			break;
91 		skb_reserve(nskb, 32);
92 		skb_set_mac_header(nskb, -ETH_HLEN);
93 		skb_reset_network_header(nskb);
94 		iph = ip_hdr(nskb);
95 		skb_copy_to_linear_data(nskb, skb_network_header(skb),
96 					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 *)(skb_network_header(nskb) + 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  */
133 static int loopback_xmit(struct sk_buff *skb, struct net_device *dev)
134 {
135 	struct pcpu_lstats *pcpu_lstats, *lb_stats;
136 
137 	skb_orphan(skb);
138 
139 	skb->protocol = eth_type_trans(skb,dev);
140 #ifndef LOOPBACK_MUST_CHECKSUM
141 	skb->ip_summed = CHECKSUM_UNNECESSARY;
142 #endif
143 
144 #ifdef LOOPBACK_TSO
145 	if (skb_is_gso(skb)) {
146 		BUG_ON(skb->protocol != htons(ETH_P_IP));
147 		BUG_ON(ip_hdr(skb)->protocol != IPPROTO_TCP);
148 
149 		emulate_large_send_offload(skb);
150 		return 0;
151 	}
152 #endif
153 	dev->last_rx = jiffies;
154 
155 	/* it's OK to use per_cpu_ptr() because BHs are off */
156 	pcpu_lstats = netdev_priv(dev);
157 	lb_stats = per_cpu_ptr(pcpu_lstats, smp_processor_id());
158 	lb_stats->bytes += skb->len;
159 	lb_stats->packets++;
160 
161 	netif_rx(skb);
162 
163 	return 0;
164 }
165 
166 static struct net_device_stats *get_stats(struct net_device *dev)
167 {
168 	const struct pcpu_lstats *pcpu_lstats;
169 	struct net_device_stats *stats = &dev->stats;
170 	unsigned long bytes = 0;
171 	unsigned long packets = 0;
172 	int i;
173 
174 	pcpu_lstats = netdev_priv(dev);
175 	for_each_possible_cpu(i) {
176 		const struct pcpu_lstats *lb_stats;
177 
178 		lb_stats = per_cpu_ptr(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 
189 static u32 always_on(struct net_device *dev)
190 {
191 	return 1;
192 }
193 
194 static const struct ethtool_ops loopback_ethtool_ops = {
195 	.get_link		= always_on,
196 	.set_tso		= ethtool_op_set_tso,
197 	.get_tx_csum		= always_on,
198 	.get_sg			= always_on,
199 	.get_rx_csum		= always_on,
200 };
201 
202 static int loopback_dev_init(struct net_device *dev)
203 {
204 	struct pcpu_lstats *lstats;
205 
206 	lstats = alloc_percpu(struct pcpu_lstats);
207 	if (!lstats)
208 		return -ENOMEM;
209 
210 	dev->priv = lstats;
211 	return 0;
212 }
213 
214 static void loopback_dev_free(struct net_device *dev)
215 {
216 	struct pcpu_lstats *lstats = netdev_priv(dev);
217 
218 	free_percpu(lstats);
219 	free_netdev(dev);
220 }
221 
222 /*
223  * The loopback device is special. There is only one instance
224  * per network namespace.
225  */
226 static void loopback_setup(struct net_device *dev)
227 {
228 	dev->get_stats		= &get_stats;
229 	dev->mtu		= (16 * 1024) + 20 + 20 + 12;
230 	dev->hard_start_xmit	= loopback_xmit;
231 	dev->hard_header_len	= ETH_HLEN;	/* 14	*/
232 	dev->addr_len		= ETH_ALEN;	/* 6	*/
233 	dev->tx_queue_len	= 0;
234 	dev->type		= ARPHRD_LOOPBACK;	/* 0x0001*/
235 	dev->flags		= IFF_LOOPBACK;
236 	dev->features 		= NETIF_F_SG | NETIF_F_FRAGLIST
237 #ifdef LOOPBACK_TSO
238 		| NETIF_F_TSO
239 #endif
240 		| NETIF_F_NO_CSUM
241 		| NETIF_F_HIGHDMA
242 		| NETIF_F_LLTX
243 		| NETIF_F_NETNS_LOCAL;
244 	dev->ethtool_ops	= &loopback_ethtool_ops;
245 	dev->header_ops		= &eth_header_ops;
246 	dev->init = loopback_dev_init;
247 	dev->destructor = loopback_dev_free;
248 }
249 
250 /* Setup and register the loopback device. */
251 static __net_init int loopback_net_init(struct net *net)
252 {
253 	struct net_device *dev;
254 	int err;
255 
256 	err = -ENOMEM;
257 	dev = alloc_netdev(0, "lo", loopback_setup);
258 	if (!dev)
259 		goto out;
260 
261 	dev_net_set(dev, net);
262 	err = register_netdev(dev);
263 	if (err)
264 		goto out_free_netdev;
265 
266 	net->loopback_dev = dev;
267 	return 0;
268 
269 
270 out_free_netdev:
271 	free_netdev(dev);
272 out:
273 	if (net == &init_net)
274 		panic("loopback: Failed to register netdevice: %d\n", err);
275 	return err;
276 }
277 
278 static __net_exit void loopback_net_exit(struct net *net)
279 {
280 	struct net_device *dev = net->loopback_dev;
281 
282 	unregister_netdev(dev);
283 }
284 
285 static struct pernet_operations __net_initdata loopback_net_ops = {
286        .init = loopback_net_init,
287        .exit = loopback_net_exit,
288 };
289 
290 static int __init loopback_init(void)
291 {
292 	return register_pernet_device(&loopback_net_ops);
293 }
294 
295 /* Loopback is special. It should be initialized before any other network
296  * device and network subsystem.
297  */
298 fs_initcall(loopback_init);
299