vcan.c revision 5a0e3ad6af8660be21ca98a971cd00f331318c05 
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 <linux/can/dev.h>
51#include <linux/slab.h>
52#include <net/rtnetlink.h>
53
54static __initdata const char banner[] =
55	KERN_INFO "vcan: Virtual CAN interface driver\n";
56
57MODULE_DESCRIPTION("virtual CAN interface");
58MODULE_LICENSE("Dual BSD/GPL");
59MODULE_AUTHOR("Urs Thuermann <urs.thuermann@volkswagen.de>");
60
61
62/*
63 * CAN test feature:
64 * Enable the echo on driver level for testing the CAN core echo modes.
65 * See Documentation/networking/can.txt for details.
66 */
67
68static int echo; /* echo testing. Default: 0 (Off) */
69module_param(echo, bool, S_IRUGO);
70MODULE_PARM_DESC(echo, "Echo sent frames (for testing). Default: 0 (Off)");
71
72
73static void vcan_rx(struct sk_buff *skb, struct net_device *dev)
74{
75	struct can_frame *cf = (struct can_frame *)skb->data;
76	struct net_device_stats *stats = &dev->stats;
77
78	stats->rx_packets++;
79	stats->rx_bytes += cf->can_dlc;
80
81	skb->protocol  = htons(ETH_P_CAN);
82	skb->pkt_type  = PACKET_BROADCAST;
83	skb->dev       = dev;
84	skb->ip_summed = CHECKSUM_UNNECESSARY;
85
86	netif_rx_ni(skb);
87}
88
89static netdev_tx_t vcan_tx(struct sk_buff *skb, struct net_device *dev)
90{
91	struct can_frame *cf = (struct can_frame *)skb->data;
92	struct net_device_stats *stats = &dev->stats;
93	int loop;
94
95	if (can_dropped_invalid_skb(dev, skb))
96		return NETDEV_TX_OK;
97
98	stats->tx_packets++;
99	stats->tx_bytes += cf->can_dlc;
100
101	/* set flag whether this packet has to be looped back */
102	loop = skb->pkt_type == PACKET_LOOPBACK;
103
104	if (!echo) {
105		/* no echo handling available inside this driver */
106
107		if (loop) {
108			/*
109			 * only count the packets here, because the
110			 * CAN core already did the echo for us
111			 */
112			stats->rx_packets++;
113			stats->rx_bytes += cf->can_dlc;
114		}
115		kfree_skb(skb);
116		return NETDEV_TX_OK;
117	}
118
119	/* perform standard echo handling for CAN network interfaces */
120
121	if (loop) {
122		struct sock *srcsk = skb->sk;
123
124		skb = skb_share_check(skb, GFP_ATOMIC);
125		if (!skb)
126			return NETDEV_TX_OK;
127
128		/* receive with packet counting */
129		skb->sk = srcsk;
130		vcan_rx(skb, dev);
131	} else {
132		/* no looped packets => no counting */
133		kfree_skb(skb);
134	}
135	return NETDEV_TX_OK;
136}
137
138static const struct net_device_ops vcan_netdev_ops = {
139	.ndo_start_xmit = vcan_tx,
140};
141
142static void vcan_setup(struct net_device *dev)
143{
144	dev->type		= ARPHRD_CAN;
145	dev->mtu		= sizeof(struct can_frame);
146	dev->hard_header_len	= 0;
147	dev->addr_len		= 0;
148	dev->tx_queue_len	= 0;
149	dev->flags		= IFF_NOARP;
150
151	/* set flags according to driver capabilities */
152	if (echo)
153		dev->flags |= IFF_ECHO;
154
155	dev->netdev_ops		= &vcan_netdev_ops;
156	dev->destructor		= free_netdev;
157}
158
159static struct rtnl_link_ops vcan_link_ops __read_mostly = {
160	.kind	= "vcan",
161	.setup	= vcan_setup,
162};
163
164static __init int vcan_init_module(void)
165{
166	printk(banner);
167
168	if (echo)
169		printk(KERN_INFO "vcan: enabled echo on driver level.\n");
170
171	return rtnl_link_register(&vcan_link_ops);
172}
173
174static __exit void vcan_cleanup_module(void)
175{
176	rtnl_link_unregister(&vcan_link_ops);
177}
178
179module_init(vcan_init_module);
180module_exit(vcan_cleanup_module);
181