vcan.c revision 424efe9caf6047ffbcd6b383ff4d2347254aabf1 
1/*
2 * vcan.c - Virtual CAN interface
3 *
4 * Copyright (c) 2002-2007 Volkswagen Group Electronic Research
5 * All rights reserved.
6 *
7 * Redistribution and use in source and binary forms, with or without
8 * modification, are permitted provided that the following conditions
9 * are met:
10 * 1. Redistributions of source code must retain the above copyright
11 *    notice, this list of conditions and the following disclaimer.
12 * 2. Redistributions in binary form must reproduce the above copyright
13 *    notice, this list of conditions and the following disclaimer in the
14 *    documentation and/or other materials provided with the distribution.
15 * 3. Neither the name of Volkswagen nor the names of its contributors
16 *    may be used to endorse or promote products derived from this software
17 *    without specific prior written permission.
18 *
19 * Alternatively, provided that this notice is retained in full, this
20 * software may be distributed under the terms of the GNU General
21 * Public License ("GPL") version 2, in which case the provisions of the
22 * GPL apply INSTEAD OF those given above.
23 *
24 * The provided data structures and external interfaces from this code
25 * are not restricted to be used by modules with a GPL compatible license.
26 *
27 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
28 * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
29 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
30 * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
31 * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
32 * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
33 * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
34 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
35 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
36 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
37 * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH
38 * DAMAGE.
39 *
40 * Send feedback to <socketcan-users@lists.berlios.de>
41 *
42 */
43
44#include <linux/module.h>
45#include <linux/init.h>
46#include <linux/netdevice.h>
47#include <linux/if_arp.h>
48#include <linux/if_ether.h>
49#include <linux/can.h>
50#include <net/rtnetlink.h>
51
52static __initdata const char banner[] =
53	KERN_INFO "vcan: Virtual CAN interface driver\n";
54
55MODULE_DESCRIPTION("virtual CAN interface");
56MODULE_LICENSE("Dual BSD/GPL");
57MODULE_AUTHOR("Urs Thuermann <urs.thuermann@volkswagen.de>");
58
59
60/*
61 * CAN test feature:
62 * Enable the echo on driver level for testing the CAN core echo modes.
63 * See Documentation/networking/can.txt for details.
64 */
65
66static int echo; /* echo testing. Default: 0 (Off) */
67module_param(echo, bool, S_IRUGO);
68MODULE_PARM_DESC(echo, "Echo sent frames (for testing). Default: 0 (Off)");
69
70
71static void vcan_rx(struct sk_buff *skb, struct net_device *dev)
72{
73	struct net_device_stats *stats = &dev->stats;
74
75	stats->rx_packets++;
76	stats->rx_bytes += skb->len;
77
78	skb->protocol  = htons(ETH_P_CAN);
79	skb->pkt_type  = PACKET_BROADCAST;
80	skb->dev       = dev;
81	skb->ip_summed = CHECKSUM_UNNECESSARY;
82
83	netif_rx(skb);
84}
85
86static netdev_tx_t vcan_tx(struct sk_buff *skb, struct net_device *dev)
87{
88	struct net_device_stats *stats = &dev->stats;
89	int loop;
90
91	stats->tx_packets++;
92	stats->tx_bytes += skb->len;
93
94	/* set flag whether this packet has to be looped back */
95	loop = skb->pkt_type == PACKET_LOOPBACK;
96
97	if (!echo) {
98		/* no echo handling available inside this driver */
99
100		if (loop) {
101			/*
102			 * only count the packets here, because the
103			 * CAN core already did the echo for us
104			 */
105			stats->rx_packets++;
106			stats->rx_bytes += skb->len;
107		}
108		kfree_skb(skb);
109		return NETDEV_TX_OK;
110	}
111
112	/* perform standard echo handling for CAN network interfaces */
113
114	if (loop) {
115		struct sock *srcsk = skb->sk;
116
117		skb = skb_share_check(skb, GFP_ATOMIC);
118		if (!skb)
119			return NETDEV_TX_OK;
120
121		/* receive with packet counting */
122		skb->sk = srcsk;
123		vcan_rx(skb, dev);
124	} else {
125		/* no looped packets => no counting */
126		kfree_skb(skb);
127	}
128	return NETDEV_TX_OK;
129}
130
131static const struct net_device_ops vcan_netdev_ops = {
132	.ndo_start_xmit = vcan_tx,
133};
134
135static void vcan_setup(struct net_device *dev)
136{
137	dev->type		= ARPHRD_CAN;
138	dev->mtu		= sizeof(struct can_frame);
139	dev->hard_header_len	= 0;
140	dev->addr_len		= 0;
141	dev->tx_queue_len	= 0;
142	dev->flags		= IFF_NOARP;
143
144	/* set flags according to driver capabilities */
145	if (echo)
146		dev->flags |= IFF_ECHO;
147
148	dev->netdev_ops		= &vcan_netdev_ops;
149	dev->destructor		= free_netdev;
150}
151
152static struct rtnl_link_ops vcan_link_ops __read_mostly = {
153	.kind	= "vcan",
154	.setup	= vcan_setup,
155};
156
157static __init int vcan_init_module(void)
158{
159	printk(banner);
160
161	if (echo)
162		printk(KERN_INFO "vcan: enabled echo on driver level.\n");
163
164	return rtnl_link_register(&vcan_link_ops);
165}
166
167static __exit void vcan_cleanup_module(void)
168{
169	rtnl_link_unregister(&vcan_link_ops);
170}
171
172module_init(vcan_init_module);
173module_exit(vcan_cleanup_module);
174