can-gw: add netlink based CAN routing

This patch adds a CAN Gateway/Router to route (and modify) CAN frames.

It is based on the PF_CAN core infrastructure for msg filtering and msg
sending and can optionally modify routed CAN frames on the fly.
CAN frames can *only* be routed between CAN network interfaces (one hop).
They can be modified with AND/OR/XOR/SET operations as configured by the
netlink configuration interface known e.g. from iptables. From the netlink
view this can-gw implements RTM_{NEW|DEL|GET}ROUTE for PF_CAN.

The CAN specific userspace tool to manage CAN routing entries can be found in
the CAN utils http://svn.berlios.de/wsvn/socketcan/trunk/can-utils/cangw.c
at the SocketCAN SVN on BerliOS.

Signed-off-by: Oliver Hartkopp <socketcan@hartkopp.net>
Signed-off-by: David S. Miller <davem@davemloft.net>

2 files changed, 165 insertions, 0 deletions

diff --git a/include/linux/can/Kbuild b/include/linux/can/Kbuild
index 8cb05aa..c62b7f1 100644
--- a/include/linux/can/Kbuild
+++ b/include/linux/can/Kbuild
@@ -1,4 +1,5 @@
 header-y += raw.h
 header-y += bcm.h
+header-y += gw.h
 header-y += error.h
 header-y += netlink.h
diff --git a/include/linux/can/gw.h b/include/linux/can/gw.h
new file mode 100644
index 0000000..5527b54
--- /dev/null
+++ b/include/linux/can/gw.h
@@ -0,0 +1,164 @@
+/*
+ * linux/can/gw.h
+ *
+ * Definitions for CAN frame Gateway/Router/Bridge
+ *
+ * Author: Oliver Hartkopp <oliver.hartkopp@volkswagen.de>
+ * Copyright (c) 2011 Volkswagen Group Electronic Research
+ * All rights reserved.
+ *
+ * Send feedback to <socketcan-users@lists.berlios.de>
+ *
+ */
+
+#ifndef CAN_GW_H
+#define CAN_GW_H
+
+#include <linux/types.h>
+#include <linux/can.h>
+
+struct rtcanmsg {
+	__u8  can_family;
+	__u8  gwtype;
+	__u16 flags;
+};
+
+/* CAN gateway types */
+enum {
+	CGW_TYPE_UNSPEC,
+	CGW_TYPE_CAN_CAN,	/* CAN->CAN routing */
+	__CGW_TYPE_MAX
+};
+
+#define CGW_TYPE_MAX (__CGW_TYPE_MAX - 1)
+
+/* CAN rtnetlink attribute definitions */
+enum {
+	CGW_UNSPEC,
+	CGW_MOD_AND,	/* CAN frame modification binary AND */
+	CGW_MOD_OR,	/* CAN frame modification binary OR */
+	CGW_MOD_XOR,	/* CAN frame modification binary XOR */
+	CGW_MOD_SET,	/* CAN frame modification set alternate values */
+	CGW_CS_XOR,	/* set data[] XOR checksum into data[index] */
+	CGW_CS_CRC8,	/* set data[] CRC8 checksum into data[index] */
+	CGW_HANDLED,	/* number of handled CAN frames */
+	CGW_DROPPED,	/* number of dropped CAN frames */
+	CGW_SRC_IF,	/* ifindex of source network interface */
+	CGW_DST_IF,	/* ifindex of destination network interface */
+	CGW_FILTER,	/* specify struct can_filter on source CAN device */
+	__CGW_MAX
+};
+
+#define CGW_MAX (__CGW_MAX - 1)
+
+#define CGW_FLAGS_CAN_ECHO 0x01
+#define CGW_FLAGS_CAN_SRC_TSTAMP 0x02
+
+#define CGW_MOD_FUNCS 4 /* AND OR XOR SET */
+
+/* CAN frame elements that are affected by curr. 3 CAN frame modifications */
+#define CGW_MOD_ID	0x01
+#define CGW_MOD_DLC	0x02
+#define CGW_MOD_DATA	0x04
+
+#define CGW_FRAME_MODS 3 /* ID DLC DATA */
+
+#define MAX_MODFUNCTIONS (CGW_MOD_FUNCS * CGW_FRAME_MODS)
+
+struct cgw_frame_mod {
+	struct can_frame cf;
+	__u8 modtype;
+} __attribute__((packed));
+
+#define CGW_MODATTR_LEN sizeof(struct cgw_frame_mod)
+
+struct cgw_csum_xor {
+	__s8 from_idx;
+	__s8 to_idx;
+	__s8 result_idx;
+	__u8 init_xor_val;
+} __attribute__((packed));
+
+struct cgw_csum_crc8 {
+	__s8 from_idx;
+	__s8 to_idx;
+	__s8 result_idx;
+	__u8 init_crc_val;
+	__u8 final_xor_val;
+	__u8 crctab[256];
+	__u8 profile;
+	__u8 profile_data[20];
+} __attribute__((packed));
+
+/* length of checksum operation parameters. idx = index in CAN frame data[] */
+#define CGW_CS_XOR_LEN  sizeof(struct cgw_csum_xor)
+#define CGW_CS_CRC8_LEN  sizeof(struct cgw_csum_crc8)
+
+/* CRC8 profiles (compute CRC for additional data elements - see below) */
+enum {
+	CGW_CRC8PRF_UNSPEC,
+	CGW_CRC8PRF_1U8,	/* compute one additional u8 value */
+	CGW_CRC8PRF_16U8,	/* u8 value table indexed by data[1] & 0xF */
+	CGW_CRC8PRF_SFFID_XOR,	/* (can_id & 0xFF) ^ (can_id >> 8 & 0xFF) */
+	__CGW_CRC8PRF_MAX
+};
+
+#define CGW_CRC8PRF_MAX (__CGW_CRC8PRF_MAX - 1)
+
+/*
+ * CAN rtnetlink attribute contents in detail
+ *
+ * CGW_XXX_IF (length 4 bytes):
+ * Sets an interface index for source/destination network interfaces.
+ * For the CAN->CAN gwtype the indices of _two_ CAN interfaces are mandatory.
+ *
+ * CGW_FILTER (length 8 bytes):
+ * Sets a CAN receive filter for the gateway job specified by the
+ * struct can_filter described in include/linux/can.h
+ *
+ * CGW_MOD_XXX (length 17 bytes):
+ * Specifies a modification that's done to a received CAN frame before it is
+ * send out to the destination interface.
+ *
+ * <struct can_frame> data used as operator
+ * <u8> affected CAN frame elements
+ *
+ * CGW_CS_XOR (length 4 bytes):
+ * Set a simple XOR checksum starting with an initial value into
+ * data[result-idx] using data[start-idx] .. data[end-idx]
+ *
+ * The XOR checksum is calculated like this:
+ *
+ * xor = init_xor_val
+ *
+ * for (i = from_idx .. to_idx)
+ *      xor ^= can_frame.data[i]
+ *
+ * can_frame.data[ result_idx ] = xor
+ *
+ * CGW_CS_CRC8 (length 282 bytes):
+ * Set a CRC8 value into data[result-idx] using a given 256 byte CRC8 table,
+ * a given initial value and a defined input data[start-idx] .. data[end-idx].
+ * Finally the result value is XOR'ed with the final_xor_val.
+ *
+ * The CRC8 checksum is calculated like this:
+ *
+ * crc = init_crc_val
+ *
+ * for (i = from_idx .. to_idx)
+ *      crc = crctab[ crc ^ can_frame.data[i] ]
+ *
+ * can_frame.data[ result_idx ] = crc ^ final_xor_val
+ *
+ * The calculated CRC may contain additional source data elements that can be
+ * defined in the handling of 'checksum profiles' e.g. shown in AUTOSAR specs
+ * like http://www.autosar.org/download/R4.0/AUTOSAR_SWS_E2ELibrary.pdf
+ * E.g. the profile_data[] may contain additional u8 values (called DATA_IDs)
+ * that are used depending on counter values inside the CAN frame data[].
+ * So far only three profiles have been implemented for illustration.
+ *
+ * Remark: In general the attribute data is a linear buffer.
+ *         Beware of sending unpacked or aligned structs!
+ */
+
+#endif