gw.h
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/*
* 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.
*
*/
#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