gw.h

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/*
 * linux/can/gw.h
 *
 * Definitions for CAN frame Gateway/Router/Bridge
 *
 * Author: Oliver Hartkopp <[email protected]>
 * 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