[CAN]: Add virtual CAN netdevice driver

This patch adds the virtual CAN bus (vcan) network driver.
The vcan device is just a loopback device for CAN frames, no
real CAN hardware is involved.

Signed-off-by: Oliver Hartkopp <oliver.hartkopp@volkswagen.de>
Signed-off-by: Urs Thuermann <urs.thuermann@volkswagen.de>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/Makefile

@@ -12,6 +12,7 @@ obj-$(CONFIG_IP1000) += ipg.o
 obj-$(CONFIG_CHELSIO_T1) += chelsio/
 obj-$(CONFIG_CHELSIO_T3) += cxgb3/
 obj-$(CONFIG_EHEA) += ehea/
+obj-$(CONFIG_CAN) += can/
 obj-$(CONFIG_BONDING) += bonding/
 obj-$(CONFIG_ATL1) += atl1/
 obj-$(CONFIG_GIANFAR) += gianfar_driver.o

drivers/net/can/Kconfig

@@ -0,0 +1,25 @@
+menu "CAN Device Drivers"
+	depends on CAN
+
+config CAN_VCAN
+	tristate "Virtual Local CAN Interface (vcan)"
+	depends on CAN
+	default N
+	---help---
+	  Similar to the network loopback devices, vcan offers a
+	  virtual local CAN interface.
+
+	  This driver can also be built as a module.  If so, the module
+	  will be called vcan.
+
+config CAN_DEBUG_DEVICES
+	bool "CAN devices debugging messages"
+	depends on CAN
+	default N
+	---help---
+	  Say Y here if you want the CAN device drivers to produce a bunch of
+	  debug messages to the system log.  Select this if you are having
+	  a problem with CAN support and want to see more of what is going
+	  on.
+
+endmenu

drivers/net/can/Makefile

@@ -0,0 +1,5 @@
+#
+#  Makefile for the Linux Controller Area Network drivers.
+#
+
+obj-$(CONFIG_CAN_VCAN)		+= vcan.o

drivers/net/can/vcan.c

@@ -0,0 +1,169 @@
+/*
+ * vcan.c - Virtual CAN interface
+ *
+ * Copyright (c) 2002-2007 Volkswagen Group Electronic Research
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in the
+ *    documentation and/or other materials provided with the distribution.
+ * 3. Neither the name of Volkswagen nor the names of its contributors
+ *    may be used to endorse or promote products derived from this software
+ *    without specific prior written permission.
+ *
+ * Alternatively, provided that this notice is retained in full, this
+ * software may be distributed under the terms of the GNU General
+ * Public License ("GPL") version 2, in which case the provisions of the
+ * GPL apply INSTEAD OF those given above.
+ *
+ * The provided data structures and external interfaces from this code
+ * are not restricted to be used by modules with a GPL compatible license.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+ * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+ * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+ * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+ * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+ * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+ * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+ * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+ * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+ * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH
+ * DAMAGE.
+ *
+ * Send feedback to <socketcan-users@lists.berlios.de>
+ *
+ */
+
+#include <linux/module.h>
+#include <linux/init.h>
+#include <linux/netdevice.h>
+#include <linux/if_arp.h>
+#include <linux/if_ether.h>
+#include <linux/can.h>
+#include <net/rtnetlink.h>
+
+static __initdata const char banner[] =
+	KERN_INFO "vcan: Virtual CAN interface driver\n";
+
+MODULE_DESCRIPTION("virtual CAN interface");
+MODULE_LICENSE("Dual BSD/GPL");
+MODULE_AUTHOR("Urs Thuermann <urs.thuermann@volkswagen.de>");
+
+
+/*
+ * CAN test feature:
+ * Enable the echo on driver level for testing the CAN core echo modes.
+ * See Documentation/networking/can.txt for details.
+ */
+
+static int echo; /* echo testing. Default: 0 (Off) */
+module_param(echo, bool, S_IRUGO);
+MODULE_PARM_DESC(echo, "Echo sent frames (for testing). Default: 0 (Off)");
+
+
+static void vcan_rx(struct sk_buff *skb, struct net_device *dev)
+{
+	struct net_device_stats *stats = &dev->stats;
+
+	stats->rx_packets++;
+	stats->rx_bytes += skb->len;
+
+	skb->protocol  = htons(ETH_P_CAN);
+	skb->pkt_type  = PACKET_BROADCAST;
+	skb->dev       = dev;
+	skb->ip_summed = CHECKSUM_UNNECESSARY;
+
+	netif_rx(skb);
+}
+
+static int vcan_tx(struct sk_buff *skb, struct net_device *dev)
+{
+	struct net_device_stats *stats = &dev->stats;
+	int loop;
+
+	stats->tx_packets++;
+	stats->tx_bytes += skb->len;
+
+	/* set flag whether this packet has to be looped back */
+	loop = skb->pkt_type == PACKET_LOOPBACK;
+
+	if (!echo) {
+		/* no echo handling available inside this driver */
+
+		if (loop) {
+			/*
+			 * only count the packets here, because the
+			 * CAN core already did the echo for us
+			 */
+			stats->rx_packets++;
+			stats->rx_bytes += skb->len;
+		}
+		kfree_skb(skb);
+		return NETDEV_TX_OK;
+	}
+
+	/* perform standard echo handling for CAN network interfaces */
+
+	if (loop) {
+		struct sock *srcsk = skb->sk;
+
+		skb = skb_share_check(skb, GFP_ATOMIC);
+		if (!skb)
+			return NETDEV_TX_OK;
+
+		/* receive with packet counting */
+		skb->sk = srcsk;
+		vcan_rx(skb, dev);
+	} else {
+		/* no looped packets => no counting */
+		kfree_skb(skb);
+	}
+	return NETDEV_TX_OK;
+}
+
+static void vcan_setup(struct net_device *dev)
+{
+	dev->type              = ARPHRD_CAN;
+	dev->mtu               = sizeof(struct can_frame);
+	dev->hard_header_len   = 0;
+	dev->addr_len          = 0;
+	dev->tx_queue_len      = 0;
+	dev->flags             = IFF_NOARP;
+
+	/* set flags according to driver capabilities */
+	if (echo)
+		dev->flags |= IFF_ECHO;
+
+	dev->hard_start_xmit   = vcan_tx;
+	dev->destructor        = free_netdev;
+}
+
+static struct rtnl_link_ops vcan_link_ops __read_mostly = {
+       .kind           = "vcan",
+       .setup          = vcan_setup,
+};
+
+static __init int vcan_init_module(void)
+{
+	printk(banner);
+
+	if (echo)
+		printk(KERN_INFO "vcan: enabled echo on driver level.\n");
+
+	return rtnl_link_register(&vcan_link_ops);
+}
+
+static __exit void vcan_cleanup_module(void)
+{
+	rtnl_link_unregister(&vcan_link_ops);
+}
+
+module_init(vcan_init_module);
+module_exit(vcan_cleanup_module);

net/can/Kconfig

@@ -39,3 +39,6 @@ config CAN_BCM
 	  You probably want to use the bcm socket in most cases where cyclic
 	  CAN messages are used on the bus (e.g. in automotive environments).
 	  To use the Broadcast Manager, use AF_CAN with protocol CAN_BCM.
+
+
+source "drivers/net/can/Kconfig"