1 /* vcan.c - Virtual CAN interface
2 *
3 * Copyright (c) 2002-2017 Volkswagen Group Electronic Research
4 * All rights reserved.
5 *
6 * Redistribution and use in source and binary forms, with or without
7 * modification, are permitted provided that the following conditions
8 * are met:
9 * 1. Redistributions of source code must retain the above copyright
10 * notice, this list of conditions and the following disclaimer.
11 * 2. Redistributions in binary form must reproduce the above copyright
12 * notice, this list of conditions and the following disclaimer in the
13 * documentation and/or other materials provided with the distribution.
14 * 3. Neither the name of Volkswagen nor the names of its contributors
15 * may be used to endorse or promote products derived from this software
16 * without specific prior written permission.
17 *
18 * Alternatively, provided that this notice is retained in full, this
19 * software may be distributed under the terms of the GNU General
20 * Public License ("GPL") version 2, in which case the provisions of the
21 * GPL apply INSTEAD OF those given above.
22 *
23 * The provided data structures and external interfaces from this code
24 * are not restricted to be used by modules with a GPL compatible license.
25 *
26 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
27 * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
28 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
29 * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
30 * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
31 * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
32 * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
33 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
34 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
35 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
36 * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH
37 * DAMAGE.
38 *
39 */
40
41 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
42
43 #include <linux/module.h>
44 #include <linux/init.h>
45 #include <linux/netdevice.h>
46 #include <linux/if_arp.h>
47 #include <linux/if_ether.h>
48 #include <linux/can.h>
49 #include <linux/can/can-ml.h>
50 #include <linux/can/dev.h>
51 #include <linux/can/skb.h>
52 #include <linux/slab.h>
53 #include <net/rtnetlink.h>
54
55 #define DRV_NAME "vcan"
56
57 MODULE_DESCRIPTION("virtual CAN interface");
58 MODULE_LICENSE("Dual BSD/GPL");
59 MODULE_AUTHOR("Urs Thuermann <urs.thuermann@volkswagen.de>");
60 MODULE_ALIAS_RTNL_LINK(DRV_NAME);
61
62 /* CAN test feature:
63 * Enable the echo on driver level for testing the CAN core echo modes.
64 * See Documentation/networking/can.rst for details.
65 */
66
67 static bool echo; /* echo testing. Default: 0 (Off) */
68 module_param(echo, bool, 0444);
69 MODULE_PARM_DESC(echo, "Echo sent frames (for testing). Default: 0 (Off)");
70
71 static void vcan_rx(struct sk_buff *skb, struct net_device *dev)
72 {
73 struct canfd_frame *cfd = (struct canfd_frame *)skb->data;
74 struct net_device_stats *stats = &dev->stats;
75
76 stats->rx_packets++;
77 stats->rx_bytes += cfd->len;
78
79 skb->pkt_type = PACKET_BROADCAST;
80 skb->dev = dev;
81 skb->ip_summed = CHECKSUM_UNNECESSARY;
82
83 netif_rx_ni(skb);
84 }
85
86 static netdev_tx_t vcan_tx(struct sk_buff *skb, struct net_device *dev)
87 {
88 struct canfd_frame *cfd = (struct canfd_frame *)skb->data;
89 struct net_device_stats *stats = &dev->stats;
90 int loop;
91
92 if (can_dropped_invalid_skb(dev, skb))
93 return NETDEV_TX_OK;
94
95 stats->tx_packets++;
96 stats->tx_bytes += cfd->len;
97
98 /* set flag whether this packet has to be looped back */
99 loop = skb->pkt_type == PACKET_LOOPBACK;
100
101 if (!echo) {
102 /* no echo handling available inside this driver */
103 if (loop) {
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 skb = can_create_echo_skb(skb);
118 if (!skb)
119 return NETDEV_TX_OK;
120
121 /* receive with packet counting */
122 vcan_rx(skb, dev);
123 } else {
124 /* no looped packets => no counting */
125 consume_skb(skb);
126 }
127 return NETDEV_TX_OK;
128 }
129
130 static int vcan_change_mtu(struct net_device *dev, int new_mtu)
131 {
132 /* Do not allow changing the MTU while running */
133 if (dev->flags & IFF_UP)
134 return -EBUSY;
135
136 if (new_mtu != CAN_MTU && new_mtu != CANFD_MTU)
137 return -EINVAL;
138
139 dev->mtu = new_mtu;
140 return 0;
141 }
142
143 static const struct net_device_ops vcan_netdev_ops = {
144 .ndo_start_xmit = vcan_tx,
145 .ndo_change_mtu = vcan_change_mtu,
146 };
147
148 static void vcan_setup(struct net_device *dev)
149 {
150 dev->type = ARPHRD_CAN;
151 dev->mtu = CANFD_MTU;
152 dev->hard_header_len = 0;
153 dev->addr_len = 0;
154 dev->tx_queue_len = 0;
155 dev->flags = IFF_NOARP;
156 dev->ml_priv = netdev_priv(dev);
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->needs_free_netdev = true;
164 }
165
166 static struct rtnl_link_ops vcan_link_ops __read_mostly = {
167 .kind = DRV_NAME,
168 .priv_size = sizeof(struct can_ml_priv),
169 .setup = vcan_setup,
170 };
171
172 static __init int vcan_init_module(void)
173 {
174 pr_info("Virtual CAN interface driver\n");
175
176 if (echo)
177 pr_info("enabled echo on driver level.\n");
178
179 return rtnl_link_register(&vcan_link_ops);
180 }
181
182 static __exit void vcan_cleanup_module(void)
183 {
184 rtnl_link_unregister(&vcan_link_ops);
185 }
186
187 module_init(vcan_init_module);
188 module_exit(vcan_cleanup_module);