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 */
41
42#include <linux/module.h>
43#include <linux/init.h>
44#include <linux/netdevice.h>
45#include <linux/if_arp.h>
46#include <linux/if_ether.h>
47#include <linux/can.h>
48#include <linux/can/dev.h>
49#include <linux/can/skb.h>
50#include <linux/slab.h>
51#include <net/rtnetlink.h>
52
53MODULE_DESCRIPTION("virtual CAN interface");
54MODULE_LICENSE("Dual BSD/GPL");
55MODULE_AUTHOR("Urs Thuermann <urs.thuermann@volkswagen.de>");
56
57
58/*
59 * CAN test feature:
60 * Enable the echo on driver level for testing the CAN core echo modes.
61 * See Documentation/networking/can.txt for details.
62 */
63
64static bool echo; /* echo testing. Default: 0 (Off) */
65module_param(echo, bool, S_IRUGO);
66MODULE_PARM_DESC(echo, "Echo sent frames (for testing). Default: 0 (Off)");
67
68
69static void vcan_rx(struct sk_buff *skb, struct net_device *dev)
70{
71	struct canfd_frame *cfd = (struct canfd_frame *)skb->data;
72	struct net_device_stats *stats = &dev->stats;
73
74	stats->rx_packets++;
75	stats->rx_bytes += cfd->len;
76
77	skb->pkt_type  = PACKET_BROADCAST;
78	skb->dev       = dev;
79	skb->ip_summed = CHECKSUM_UNNECESSARY;
80
81	netif_rx_ni(skb);
82}
83
84static netdev_tx_t vcan_tx(struct sk_buff *skb, struct net_device *dev)
85{
86	struct canfd_frame *cfd = (struct canfd_frame *)skb->data;
87	struct net_device_stats *stats = &dev->stats;
88	int loop;
89
90	if (can_dropped_invalid_skb(dev, skb))
91		return NETDEV_TX_OK;
92
93	stats->tx_packets++;
94	stats->tx_bytes += cfd->len;
95
96	/* set flag whether this packet has to be looped back */
97	loop = skb->pkt_type == PACKET_LOOPBACK;
98
99	if (!echo) {
100		/* no echo handling available inside this driver */
101
102		if (loop) {
103			/*
104			 * only count the packets here, because the
105			 * CAN core already did the echo for us
106			 */
107			stats->rx_packets++;
108			stats->rx_bytes += cfd->len;
109		}
110		consume_skb(skb);
111		return NETDEV_TX_OK;
112	}
113
114	/* perform standard echo handling for CAN network interfaces */
115
116	if (loop) {
117
118		skb = can_create_echo_skb(skb);
119		if (!skb)
120			return NETDEV_TX_OK;
121
122		/* receive with packet counting */
123		vcan_rx(skb, dev);
124	} else {
125		/* no looped packets => no counting */
126		consume_skb(skb);
127	}
128	return NETDEV_TX_OK;
129}
130
131static int vcan_change_mtu(struct net_device *dev, int new_mtu)
132{
133	/* Do not allow changing the MTU while running */
134	if (dev->flags & IFF_UP)
135		return -EBUSY;
136
137	if (new_mtu != CAN_MTU && new_mtu != CANFD_MTU)
138		return -EINVAL;
139
140	dev->mtu = new_mtu;
141	return 0;
142}
143
144static const struct net_device_ops vcan_netdev_ops = {
145	.ndo_start_xmit = vcan_tx,
146	.ndo_change_mtu = vcan_change_mtu,
147};
148
149static void vcan_setup(struct net_device *dev)
150{
151	dev->type		= ARPHRD_CAN;
152	dev->mtu		= CAN_MTU;
153	dev->hard_header_len	= 0;
154	dev->addr_len		= 0;
155	dev->tx_queue_len	= 0;
156	dev->flags		= IFF_NOARP;
157
158	/* set flags according to driver capabilities */
159	if (echo)
160		dev->flags |= IFF_ECHO;
161
162	dev->netdev_ops		= &vcan_netdev_ops;
163	dev->destructor		= free_netdev;
164}
165
166static struct rtnl_link_ops vcan_link_ops __read_mostly = {
167	.kind	= "vcan",
168	.setup	= vcan_setup,
169};
170
171static __init int vcan_init_module(void)
172{
173	pr_info("vcan: Virtual CAN interface driver\n");
174
175	if (echo)
176		printk(KERN_INFO "vcan: enabled echo on driver level.\n");
177
178	return rtnl_link_register(&vcan_link_ops);
179}
180
181static __exit void vcan_cleanup_module(void)
182{
183	rtnl_link_unregister(&vcan_link_ops);
184}
185
186module_init(vcan_init_module);
187module_exit(vcan_cleanup_module);
188