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001: /*
002:  * linux/can/gw.h
003:  *
004:  * Definitions for CAN frame Gateway/Router/Bridge
005:  *
006:  * Author: Oliver Hartkopp <oliver.hartkopp@volkswagen.de>
007:  * Copyright (c) 2011 Volkswagen Group Electronic Research
008:  * All rights reserved.
009:  *
010:  */
011: 
012: #ifndef CAN_GW_H
013: #define CAN_GW_H
014: 
015: #include <linux/types.h>
016: #include <linux/can.h>
017: 
018: struct rtcanmsg {
019:         __u8  can_family;
020:         __u8  gwtype;
021:         __u16 flags;
022: };
023: 
024: /* CAN gateway types */
025: enum {
026:         CGW_TYPE_UNSPEC,
027:         CGW_TYPE_CAN_CAN,       /* CAN->CAN routing */
028:         __CGW_TYPE_MAX
029: };
030: 
031: #define CGW_TYPE_MAX (__CGW_TYPE_MAX - 1)
032: 
033: /* CAN rtnetlink attribute definitions */
034: enum {
035:         CGW_UNSPEC,
036:         CGW_MOD_AND,    /* CAN frame modification binary AND */
037:         CGW_MOD_OR,     /* CAN frame modification binary OR */
038:         CGW_MOD_XOR,    /* CAN frame modification binary XOR */
039:         CGW_MOD_SET,    /* CAN frame modification set alternate values */
040:         CGW_CS_XOR,     /* set data[] XOR checksum into data[index] */
041:         CGW_CS_CRC8,    /* set data[] CRC8 checksum into data[index] */
042:         CGW_HANDLED,    /* number of handled CAN frames */
043:         CGW_DROPPED,    /* number of dropped CAN frames */
044:         CGW_SRC_IF,     /* ifindex of source network interface */
045:         CGW_DST_IF,     /* ifindex of destination network interface */
046:         CGW_FILTER,     /* specify struct can_filter on source CAN device */
047:         __CGW_MAX
048: };
049: 
050: #define CGW_MAX (__CGW_MAX - 1)
051: 
052: #define CGW_FLAGS_CAN_ECHO 0x01
053: #define CGW_FLAGS_CAN_SRC_TSTAMP 0x02
054: 
055: #define CGW_MOD_FUNCS 4 /* AND OR XOR SET */
056: 
057: /* CAN frame elements that are affected by curr. 3 CAN frame modifications */
058: #define CGW_MOD_ID      0x01
059: #define CGW_MOD_DLC     0x02
060: #define CGW_MOD_DATA    0x04
061: 
062: #define CGW_FRAME_MODS 3 /* ID DLC DATA */
063: 
064: #define MAX_MODFUNCTIONS (CGW_MOD_FUNCS * CGW_FRAME_MODS)
065: 
066: struct cgw_frame_mod {
067:         struct can_frame cf;
068:         __u8 modtype;
069: } __attribute__((packed));
070: 
071: #define CGW_MODATTR_LEN sizeof(struct cgw_frame_mod)
072: 
073: struct cgw_csum_xor {
074:         __s8 from_idx;
075:         __s8 to_idx;
076:         __s8 result_idx;
077:         __u8 init_xor_val;
078: } __attribute__((packed));
079: 
080: struct cgw_csum_crc8 {
081:         __s8 from_idx;
082:         __s8 to_idx;
083:         __s8 result_idx;
084:         __u8 init_crc_val;
085:         __u8 final_xor_val;
086:         __u8 crctab[256];
087:         __u8 profile;
088:         __u8 profile_data[20];
089: } __attribute__((packed));
090: 
091: /* length of checksum operation parameters. idx = index in CAN frame data[] */
092: #define CGW_CS_XOR_LEN  sizeof(struct cgw_csum_xor)
093: #define CGW_CS_CRC8_LEN  sizeof(struct cgw_csum_crc8)
094: 
095: /* CRC8 profiles (compute CRC for additional data elements - see below) */
096: enum {
097:         CGW_CRC8PRF_UNSPEC,
098:         CGW_CRC8PRF_1U8,        /* compute one additional u8 value */
099:         CGW_CRC8PRF_16U8,       /* u8 value table indexed by data[1] & 0xF */
100:         CGW_CRC8PRF_SFFID_XOR,  /* (can_id & 0xFF) ^ (can_id >> 8 & 0xFF) */
101:         __CGW_CRC8PRF_MAX
102: };
103: 
104: #define CGW_CRC8PRF_MAX (__CGW_CRC8PRF_MAX - 1)
105: 
106: /*
107:  * CAN rtnetlink attribute contents in detail
108:  *
109:  * CGW_XXX_IF (length 4 bytes):
110:  * Sets an interface index for source/destination network interfaces.
111:  * For the CAN->CAN gwtype the indices of _two_ CAN interfaces are mandatory.
112:  *
113:  * CGW_FILTER (length 8 bytes):
114:  * Sets a CAN receive filter for the gateway job specified by the
115:  * struct can_filter described in include/linux/can.h
116:  *
117:  * CGW_MOD_XXX (length 17 bytes):
118:  * Specifies a modification that's done to a received CAN frame before it is
119:  * send out to the destination interface.
120:  *
121:  * <struct can_frame> data used as operator
122:  * <u8> affected CAN frame elements
123:  *
124:  * CGW_CS_XOR (length 4 bytes):
125:  * Set a simple XOR checksum starting with an initial value into
126:  * data[result-idx] using data[start-idx] .. data[end-idx]
127:  *
128:  * The XOR checksum is calculated like this:
129:  *
130:  * xor = init_xor_val
131:  *
132:  * for (i = from_idx .. to_idx)
133:  *      xor ^= can_frame.data[i]
134:  *
135:  * can_frame.data[ result_idx ] = xor
136:  *
137:  * CGW_CS_CRC8 (length 282 bytes):
138:  * Set a CRC8 value into data[result-idx] using a given 256 byte CRC8 table,
139:  * a given initial value and a defined input data[start-idx] .. data[end-idx].
140:  * Finally the result value is XOR'ed with the final_xor_val.
141:  *
142:  * The CRC8 checksum is calculated like this:
143:  *
144:  * crc = init_crc_val
145:  *
146:  * for (i = from_idx .. to_idx)
147:  *      crc = crctab[ crc ^ can_frame.data[i] ]
148:  *
149:  * can_frame.data[ result_idx ] = crc ^ final_xor_val
150:  *
151:  * The calculated CRC may contain additional source data elements that can be
152:  * defined in the handling of 'checksum profiles' e.g. shown in AUTOSAR specs
153:  * like http://www.autosar.org/download/R4.0/AUTOSAR_SWS_E2ELibrary.pdf
154:  * E.g. the profile_data[] may contain additional u8 values (called DATA_IDs)
155:  * that are used depending on counter values inside the CAN frame data[].
156:  * So far only three profiles have been implemented for illustration.
157:  *
158:  * Remark: In general the attribute data is a linear buffer.
159:  *         Beware of sending unpacked or aligned structs!
160:  */
161: 
162: #endif
163: 

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