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modbus.c
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modbus.c
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/*
* Copyright © 2001-2011 Stéphane Raimbault <stephane.raimbault@gmail.com>
*
* SPDX-License-Identifier: LGPL-2.1+
*
* This library implements the Modbus protocol.
* http://libmodbus.org/
*/
#include <stdio.h>
#include <string.h>
#include <stdlib.h>
#include <stdarg.h>
#include <errno.h>
#include <limits.h>
#include <time.h>
#ifndef _MSC_VER
#include <unistd.h>
#endif
#include <config.h>
#include "modbus.h"
#include "modbus-private.h"
/* Internal use */
#define MSG_LENGTH_UNDEFINED -1
/* Exported version */
const unsigned int libmodbus_version_major = LIBMODBUS_VERSION_MAJOR;
const unsigned int libmodbus_version_minor = LIBMODBUS_VERSION_MINOR;
const unsigned int libmodbus_version_micro = LIBMODBUS_VERSION_MICRO;
/* Max between RTU and TCP max adu length (so TCP) */
#define MAX_MESSAGE_LENGTH 260
/* 3 steps are used to parse the query */
typedef enum {
_STEP_FUNCTION,
_STEP_META,
_STEP_DATA
} _step_t;
const char *modbus_strerror(int errnum) {
switch (errnum) {
case EMBXILFUN:
return "Illegal function";
case EMBXILADD:
return "Illegal data address";
case EMBXILVAL:
return "Illegal data value";
case EMBXSFAIL:
return "Slave device or server failure";
case EMBXACK:
return "Acknowledge";
case EMBXSBUSY:
return "Slave device or server is busy";
case EMBXNACK:
return "Negative acknowledge";
case EMBXMEMPAR:
return "Memory parity error";
case EMBXGPATH:
return "Gateway path unavailable";
case EMBXGTAR:
return "Target device failed to respond";
case EMBBADCRC:
return "Invalid CRC";
case EMBBADDATA:
return "Invalid data";
case EMBBADEXC:
return "Invalid exception code";
case EMBMDATA:
return "Too many data";
case EMBBADSLAVE:
return "Response not from requested slave";
default:
return strerror(errnum);
}
}
void _error_print(modbus_t *ctx, const char *context)
{
if (ctx->debug) {
fprintf(stderr, "ERROR %s", modbus_strerror(errno));
if (context != NULL) {
fprintf(stderr, ": %s\n", context);
} else {
fprintf(stderr, "\n");
}
}
}
static void _sleep_response_timeout(modbus_t *ctx)
{
/* Response timeout is always positive */
#ifdef _WIN32
/* usleep doesn't exist on Windows */
Sleep((ctx->response_timeout.tv_sec * 1000) +
(ctx->response_timeout.tv_usec / 1000));
#else
/* usleep source code */
struct timespec request, remaining;
request.tv_sec = ctx->response_timeout.tv_sec;
request.tv_nsec = ((long int)ctx->response_timeout.tv_usec) * 1000;
while (nanosleep(&request, &remaining) == -1 && errno == EINTR) {
request = remaining;
}
#endif
}
int modbus_flush(modbus_t *ctx)
{
int rc;
if (ctx == NULL) {
errno = EINVAL;
return -1;
}
rc = ctx->backend->flush(ctx);
if (rc != -1 && ctx->debug) {
/* Not all backends are able to return the number of bytes flushed */
printf("Bytes flushed (%d)\n", rc);
}
return rc;
}
/* Computes the length of the expected response */
static unsigned int compute_response_length_from_request(modbus_t *ctx, uint8_t *req)
{
int length;
const int offset = ctx->backend->header_length;
switch (req[offset]) {
case MODBUS_FC_READ_COILS:
case MODBUS_FC_READ_DISCRETE_INPUTS: {
/* Header + nb values (code from write_bits) */
int nb = (req[offset + 3] << 8) | req[offset + 4];
length = 2 + (nb / 8) + ((nb % 8) ? 1 : 0);
}
break;
case MODBUS_FC_WRITE_AND_READ_REGISTERS:
case MODBUS_FC_READ_HOLDING_REGISTERS:
case MODBUS_FC_READ_INPUT_REGISTERS:
/* Header + 2 * nb values */
length = 2 + 2 * (req[offset + 3] << 8 | req[offset + 4]);
break;
case MODBUS_FC_READ_EXCEPTION_STATUS:
length = 3;
break;
case MODBUS_FC_REPORT_SLAVE_ID:
/* The response is device specific (the header provides the
length) */
return MSG_LENGTH_UNDEFINED;
case MODBUS_FC_MASK_WRITE_REGISTER:
length = 7;
break;
default:
length = 5;
}
return offset + length + ctx->backend->checksum_length;
}
/* Sends a request/response */
static int send_msg(modbus_t *ctx, uint8_t *msg, int msg_length)
{
int rc;
int i;
msg_length = ctx->backend->send_msg_pre(msg, msg_length);
if (ctx->debug) {
for (i = 0; i < msg_length; i++)
printf("[%.2X]", msg[i]);
printf("\n");
}
/* In recovery mode, the write command will be issued until to be
successful! Disabled by default. */
do {
rc = ctx->backend->send(ctx, msg, msg_length);
if (rc == -1) {
_error_print(ctx, NULL);
if (ctx->error_recovery & MODBUS_ERROR_RECOVERY_LINK) {
int saved_errno = errno;
if ((errno == EBADF || errno == ECONNRESET || errno == EPIPE)) {
modbus_close(ctx);
_sleep_response_timeout(ctx);
modbus_connect(ctx);
} else {
_sleep_response_timeout(ctx);
modbus_flush(ctx);
}
errno = saved_errno;
}
}
} while ((ctx->error_recovery & MODBUS_ERROR_RECOVERY_LINK) &&
rc == -1);
if (rc > 0 && rc != msg_length) {
errno = EMBBADDATA;
return -1;
}
return rc;
}
int modbus_send_raw_request(modbus_t *ctx, uint8_t *raw_req, int raw_req_length)
{
sft_t sft;
uint8_t req[MAX_MESSAGE_LENGTH];
int req_length;
if (ctx == NULL) {
errno = EINVAL;
return -1;
}
if (raw_req_length < 2 || raw_req_length > (MODBUS_MAX_PDU_LENGTH + 1)) {
/* The raw request must contain function and slave at least and
must not be longer than the maximum pdu length plus the slave
address. */
errno = EINVAL;
return -1;
}
sft.slave = raw_req[0];
sft.function = raw_req[1];
/* The t_id is left to zero */
sft.t_id = 0;
/* This response function only set the header so it's convenient here */
req_length = ctx->backend->build_response_basis(&sft, req);
if (raw_req_length > 2) {
/* Copy data after function code */
memcpy(req + req_length, raw_req + 2, raw_req_length - 2);
req_length += raw_req_length - 2;
}
return send_msg(ctx, req, req_length);
}
/*
* ---------- Request Indication ----------
* | Client | ---------------------->| Server |
* ---------- Confirmation Response ----------
*/
/* Computes the length to read after the function received */
static uint8_t compute_meta_length_after_function(int function,
msg_type_t msg_type)
{
int length;
if (msg_type == MSG_INDICATION) {
if (function <= MODBUS_FC_WRITE_SINGLE_REGISTER) {
length = 4;
} else if (function == MODBUS_FC_WRITE_MULTIPLE_COILS ||
function == MODBUS_FC_WRITE_MULTIPLE_REGISTERS) {
length = 5;
} else if (function == MODBUS_FC_MASK_WRITE_REGISTER) {
length = 6;
} else if (function == MODBUS_FC_WRITE_AND_READ_REGISTERS) {
length = 9;
} else {
/* MODBUS_FC_READ_EXCEPTION_STATUS, MODBUS_FC_REPORT_SLAVE_ID */
length = 0;
}
} else {
/* MSG_CONFIRMATION */
switch (function) {
case MODBUS_FC_WRITE_SINGLE_COIL:
case MODBUS_FC_WRITE_SINGLE_REGISTER:
case MODBUS_FC_WRITE_MULTIPLE_COILS:
case MODBUS_FC_WRITE_MULTIPLE_REGISTERS:
length = 4;
break;
case MODBUS_FC_MASK_WRITE_REGISTER:
length = 6;
break;
default:
length = 1;
}
}
return length;
}
/* Computes the length to read after the meta information (address, count, etc) */
static int compute_data_length_after_meta(modbus_t *ctx, uint8_t *msg,
msg_type_t msg_type)
{
int function = msg[ctx->backend->header_length];
int length;
if (msg_type == MSG_INDICATION) {
switch (function) {
case MODBUS_FC_WRITE_MULTIPLE_COILS:
case MODBUS_FC_WRITE_MULTIPLE_REGISTERS:
length = msg[ctx->backend->header_length + 5];
break;
case MODBUS_FC_WRITE_AND_READ_REGISTERS:
length = msg[ctx->backend->header_length + 9];
break;
default:
length = 0;
}
} else {
/* MSG_CONFIRMATION */
if (function <= MODBUS_FC_READ_INPUT_REGISTERS ||
function == MODBUS_FC_REPORT_SLAVE_ID ||
function == MODBUS_FC_WRITE_AND_READ_REGISTERS) {
length = msg[ctx->backend->header_length + 1];
} else {
length = 0;
}
}
length += ctx->backend->checksum_length;
return length;
}
/* Waits a response from a modbus server or a request from a modbus client.
This function blocks if there is no replies (3 timeouts).
The function shall return the number of received characters and the received
message in an array of uint8_t if successful. Otherwise it shall return -1
and errno is set to one of the values defined below:
- ECONNRESET
- EMBBADDATA
- EMBUNKEXC
- ETIMEDOUT
- read() or recv() error codes
*/
int _modbus_receive_msg(modbus_t *ctx, uint8_t *msg, msg_type_t msg_type)
{
int rc;
fd_set rset;
struct timeval tv;
struct timeval *p_tv;
int length_to_read;
int msg_length = 0;
_step_t step;
if (ctx->debug) {
if (msg_type == MSG_INDICATION) {
printf("Waiting for a indication...\n");
} else {
printf("Waiting for a confirmation...\n");
}
}
/* Add a file descriptor to the set */
FD_ZERO(&rset);
FD_SET(ctx->s, &rset);
/* We need to analyse the message step by step. At the first step, we want
* to reach the function code because all packets contain this
* information. */
step = _STEP_FUNCTION;
length_to_read = ctx->backend->header_length + 1;
if (msg_type == MSG_INDICATION) {
/* Wait for a message, we don't know when the message will be
* received */
p_tv = NULL;
} else {
tv.tv_sec = ctx->response_timeout.tv_sec;
tv.tv_usec = ctx->response_timeout.tv_usec;
p_tv = &tv;
}
while (length_to_read != 0) {
rc = ctx->backend->select(ctx, &rset, p_tv, length_to_read);
if (rc == -1) {
_error_print(ctx, "select");
if (ctx->error_recovery & MODBUS_ERROR_RECOVERY_LINK) {
int saved_errno = errno;
if (errno == ETIMEDOUT) {
_sleep_response_timeout(ctx);
modbus_flush(ctx);
} else if (errno == EBADF) {
modbus_close(ctx);
modbus_connect(ctx);
}
errno = saved_errno;
}
return -1;
}
rc = ctx->backend->recv(ctx, msg + msg_length, length_to_read);
if (rc == 0) {
errno = ECONNRESET;
rc = -1;
}
if (rc == -1) {
_error_print(ctx, "read");
if ((ctx->error_recovery & MODBUS_ERROR_RECOVERY_LINK) &&
(errno == ECONNRESET || errno == ECONNREFUSED ||
errno == EBADF)) {
int saved_errno = errno;
modbus_close(ctx);
modbus_connect(ctx);
/* Could be removed by previous calls */
errno = saved_errno;
}
return -1;
}
/* Display the hex code of each character received */
if (ctx->debug) {
int i;
for (i=0; i < rc; i++)
printf("<%.2X>", msg[msg_length + i]);
}
/* Sums bytes received */
msg_length += rc;
/* Computes remaining bytes */
length_to_read -= rc;
if (length_to_read == 0) {
switch (step) {
case _STEP_FUNCTION:
/* Function code position */
length_to_read = compute_meta_length_after_function(
msg[ctx->backend->header_length],
msg_type);
if (length_to_read != 0) {
step = _STEP_META;
break;
} /* else switches straight to the next step */
case _STEP_META:
length_to_read = compute_data_length_after_meta(
ctx, msg, msg_type);
if ((msg_length + length_to_read) > (int)ctx->backend->max_adu_length) {
errno = EMBBADDATA;
_error_print(ctx, "too many data");
return -1;
}
step = _STEP_DATA;
break;
default:
break;
}
}
if (length_to_read > 0 &&
(ctx->byte_timeout.tv_sec > 0 || ctx->byte_timeout.tv_usec > 0)) {
/* If there is no character in the buffer, the allowed timeout
interval between two consecutive bytes is defined by
byte_timeout */
tv.tv_sec = ctx->byte_timeout.tv_sec;
tv.tv_usec = ctx->byte_timeout.tv_usec;
p_tv = &tv;
}
/* else timeout isn't set again, the full response must be read before
expiration of response timeout (for CONFIRMATION only) */
}
if (ctx->debug)
printf("\n");
return ctx->backend->check_integrity(ctx, msg, msg_length);
}
/* Receive the request from a modbus master */
int modbus_receive(modbus_t *ctx, uint8_t *req)
{
if (ctx == NULL) {
errno = EINVAL;
return -1;
}
return ctx->backend->receive(ctx, req);
}
/* Receives the confirmation.
The function shall store the read response in rsp and return the number of
values (bits or words). Otherwise, its shall return -1 and errno is set.
The function doesn't check the confirmation is the expected response to the
initial request.
*/
int modbus_receive_confirmation(modbus_t *ctx, uint8_t *rsp)
{
if (ctx == NULL) {
errno = EINVAL;
return -1;
}
return _modbus_receive_msg(ctx, rsp, MSG_CONFIRMATION);
}
static int check_confirmation(modbus_t *ctx, uint8_t *req,
uint8_t *rsp, int rsp_length)
{
int rc;
int rsp_length_computed;
const int offset = ctx->backend->header_length;
const int function = rsp[offset];
if (ctx->backend->pre_check_confirmation) {
rc = ctx->backend->pre_check_confirmation(ctx, req, rsp, rsp_length);
if (rc == -1) {
if (ctx->error_recovery & MODBUS_ERROR_RECOVERY_PROTOCOL) {
_sleep_response_timeout(ctx);
modbus_flush(ctx);
}
return -1;
}
}
rsp_length_computed = compute_response_length_from_request(ctx, req);
/* Exception code */
if (function >= 0x80) {
if (rsp_length == (offset + 2 + (int)ctx->backend->checksum_length) &&
req[offset] == (rsp[offset] - 0x80)) {
/* Valid exception code received */
int exception_code = rsp[offset + 1];
if (exception_code < MODBUS_EXCEPTION_MAX) {
errno = MODBUS_ENOBASE + exception_code;
} else {
errno = EMBBADEXC;
}
_error_print(ctx, NULL);
return -1;
} else {
errno = EMBBADEXC;
_error_print(ctx, NULL);
return -1;
}
}
/* Check length */
if ((rsp_length == rsp_length_computed ||
rsp_length_computed == MSG_LENGTH_UNDEFINED) &&
function < 0x80) {
int req_nb_value;
int rsp_nb_value;
/* Check function code */
if (function != req[offset]) {
if (ctx->debug) {
fprintf(stderr,
"Received function not corresponding to the request (0x%X != 0x%X)\n",
function, req[offset]);
}
if (ctx->error_recovery & MODBUS_ERROR_RECOVERY_PROTOCOL) {
_sleep_response_timeout(ctx);
modbus_flush(ctx);
}
errno = EMBBADDATA;
return -1;
}
/* Check the number of values is corresponding to the request */
switch (function) {
case MODBUS_FC_READ_COILS:
case MODBUS_FC_READ_DISCRETE_INPUTS:
/* Read functions, 8 values in a byte (nb
* of values in the request and byte count in
* the response. */
req_nb_value = (req[offset + 3] << 8) + req[offset + 4];
req_nb_value = (req_nb_value / 8) + ((req_nb_value % 8) ? 1 : 0);
rsp_nb_value = rsp[offset + 1];
break;
case MODBUS_FC_WRITE_AND_READ_REGISTERS:
case MODBUS_FC_READ_HOLDING_REGISTERS:
case MODBUS_FC_READ_INPUT_REGISTERS:
/* Read functions 1 value = 2 bytes */
req_nb_value = (req[offset + 3] << 8) + req[offset + 4];
rsp_nb_value = (rsp[offset + 1] / 2);
break;
case MODBUS_FC_WRITE_MULTIPLE_COILS:
case MODBUS_FC_WRITE_MULTIPLE_REGISTERS:
/* N Write functions */
req_nb_value = (req[offset + 3] << 8) + req[offset + 4];
rsp_nb_value = (rsp[offset + 3] << 8) | rsp[offset + 4];
break;
case MODBUS_FC_REPORT_SLAVE_ID:
/* Report slave ID (bytes received) */
req_nb_value = rsp_nb_value = rsp[offset + 1];
break;
default:
/* 1 Write functions & others */
req_nb_value = rsp_nb_value = 1;
}
if (req_nb_value == rsp_nb_value) {
rc = rsp_nb_value;
} else {
if (ctx->debug) {
fprintf(stderr,
"Quantity not corresponding to the request (%d != %d)\n",
rsp_nb_value, req_nb_value);
}
if (ctx->error_recovery & MODBUS_ERROR_RECOVERY_PROTOCOL) {
_sleep_response_timeout(ctx);
modbus_flush(ctx);
}
errno = EMBBADDATA;
rc = -1;
}
} else {
if (ctx->debug) {
fprintf(stderr,
"Message length not corresponding to the computed length (%d != %d)\n",
rsp_length, rsp_length_computed);
}
if (ctx->error_recovery & MODBUS_ERROR_RECOVERY_PROTOCOL) {
_sleep_response_timeout(ctx);
modbus_flush(ctx);
}
errno = EMBBADDATA;
rc = -1;
}
return rc;
}
static int response_io_status(uint8_t *tab_io_status,
int address, int nb,
uint8_t *rsp, int offset)
{
int shift = 0;
/* Instead of byte (not allowed in Win32) */
int one_byte = 0;
int i;
for (i = address; i < address + nb; i++) {
one_byte |= tab_io_status[i] << shift;
if (shift == 7) {
/* Byte is full */
rsp[offset++] = one_byte;
one_byte = shift = 0;
} else {
shift++;
}
}
if (shift != 0)
rsp[offset++] = one_byte;
return offset;
}
/* Build the exception response */
static int response_exception(modbus_t *ctx, sft_t *sft,
int exception_code, uint8_t *rsp,
unsigned int to_flush,
const char* template, ...)
{
int rsp_length;
/* Print debug message */
if (ctx->debug) {
va_list ap;
va_start(ap, template);
vfprintf(stderr, template, ap);
va_end(ap);
}
/* Flush if required */
if (to_flush) {
_sleep_response_timeout(ctx);
modbus_flush(ctx);
}
/* Build exception response */
sft->function = sft->function + 0x80;
rsp_length = ctx->backend->build_response_basis(sft, rsp);
rsp[rsp_length++] = exception_code;
return rsp_length;
}
/* Send a response to the received request.
Analyses the request and constructs a response.
If an error occurs, this function construct the response
accordingly.
*/
int modbus_reply(modbus_t *ctx, const uint8_t *req,
int req_length, modbus_mapping_t *mb_mapping)
{
int offset;
int slave;
int function;
uint16_t address;
uint8_t rsp[MAX_MESSAGE_LENGTH];
int rsp_length = 0;
sft_t sft;
if (ctx == NULL) {
errno = EINVAL;
return -1;
}
offset = ctx->backend->header_length;
slave = req[offset - 1];
function = req[offset];
address = (req[offset + 1] << 8) + req[offset + 2];
sft.slave = slave;
sft.function = function;
sft.t_id = ctx->backend->prepare_response_tid(req, &req_length);
/* Data are flushed on illegal number of values errors. */
switch (function) {
case MODBUS_FC_READ_COILS:
case MODBUS_FC_READ_DISCRETE_INPUTS: {
unsigned int is_input = (function == MODBUS_FC_READ_DISCRETE_INPUTS);
int start_bits = is_input ? mb_mapping->start_input_bits : mb_mapping->start_bits;
int nb_bits = is_input ? mb_mapping->nb_input_bits : mb_mapping->nb_bits;
uint8_t *tab_bits = is_input ? mb_mapping->tab_input_bits : mb_mapping->tab_bits;
const char * const name = is_input ? "read_input_bits" : "read_bits";
int nb = (req[offset + 3] << 8) + req[offset + 4];
/* The mapping can be shifted to reduce memory consumption and it
doesn't always start at address zero. */
int mapping_address = address - start_bits;
if (nb < 1 || MODBUS_MAX_READ_BITS < nb) {
rsp_length = response_exception(
ctx, &sft, MODBUS_EXCEPTION_ILLEGAL_DATA_VALUE, rsp, TRUE,
"Illegal nb of values %d in %s (max %d)\n",
nb, name, MODBUS_MAX_READ_BITS);
} else if (mapping_address < 0 || (mapping_address + nb) > nb_bits) {
rsp_length = response_exception(
ctx, &sft,
MODBUS_EXCEPTION_ILLEGAL_DATA_ADDRESS, rsp, FALSE,
"Illegal data address 0x%0X in %s\n",
mapping_address < 0 ? address : address + nb, name);
} else {
rsp_length = ctx->backend->build_response_basis(&sft, rsp);
rsp[rsp_length++] = (nb / 8) + ((nb % 8) ? 1 : 0);
rsp_length = response_io_status(tab_bits, mapping_address, nb,
rsp, rsp_length);
}
}
break;
case MODBUS_FC_READ_HOLDING_REGISTERS:
case MODBUS_FC_READ_INPUT_REGISTERS: {
unsigned int is_input = (function == MODBUS_FC_READ_INPUT_REGISTERS);
int start_registers = is_input ? mb_mapping->start_input_registers : mb_mapping->start_registers;
int nb_registers = is_input ? mb_mapping->nb_input_registers : mb_mapping->nb_registers;
uint16_t *tab_registers = is_input ? mb_mapping->tab_input_registers : mb_mapping->tab_registers;
const char * const name = is_input ? "read_input_registers" : "read_registers";
int nb = (req[offset + 3] << 8) + req[offset + 4];
/* The mapping can be shifted to reduce memory consumption and it
doesn't always start at address zero. */
int mapping_address = address - start_registers;
if (nb < 1 || MODBUS_MAX_READ_REGISTERS < nb) {
rsp_length = response_exception(
ctx, &sft, MODBUS_EXCEPTION_ILLEGAL_DATA_VALUE, rsp, TRUE,
"Illegal nb of values %d in %s (max %d)\n",
nb, name, MODBUS_MAX_READ_REGISTERS);
} else if (mapping_address < 0 || (mapping_address + nb) > nb_registers) {
rsp_length = response_exception(
ctx, &sft, MODBUS_EXCEPTION_ILLEGAL_DATA_ADDRESS, rsp, FALSE,
"Illegal data address 0x%0X in %s\n",
mapping_address < 0 ? address : address + nb, name);
} else {
int i;
rsp_length = ctx->backend->build_response_basis(&sft, rsp);
rsp[rsp_length++] = nb << 1;
for (i = mapping_address; i < mapping_address + nb; i++) {
rsp[rsp_length++] = tab_registers[i] >> 8;
rsp[rsp_length++] = tab_registers[i] & 0xFF;
}
}
}
break;
case MODBUS_FC_WRITE_SINGLE_COIL: {
int mapping_address = address - mb_mapping->start_bits;
if (mapping_address < 0 || mapping_address >= mb_mapping->nb_bits) {
rsp_length = response_exception(
ctx, &sft, MODBUS_EXCEPTION_ILLEGAL_DATA_ADDRESS, rsp, FALSE,
"Illegal data address 0x%0X in write_bit\n",
address);
} else {
int data = (req[offset + 3] << 8) + req[offset + 4];
if (data == 0xFF00 || data == 0x0) {
mb_mapping->tab_bits[mapping_address] = data ? ON : OFF;
memcpy(rsp, req, req_length);
rsp_length = req_length;
} else {
rsp_length = response_exception(
ctx, &sft,
MODBUS_EXCEPTION_ILLEGAL_DATA_VALUE, rsp, FALSE,
"Illegal data value 0x%0X in write_bit request at address %0X\n",
data, address);
}
}
}
break;
case MODBUS_FC_WRITE_SINGLE_REGISTER: {
int mapping_address = address - mb_mapping->start_registers;
if (mapping_address < 0 || mapping_address >= mb_mapping->nb_registers) {
rsp_length = response_exception(
ctx, &sft,
MODBUS_EXCEPTION_ILLEGAL_DATA_ADDRESS, rsp, FALSE,
"Illegal data address 0x%0X in write_register\n",
address);
} else {
int data = (req[offset + 3] << 8) + req[offset + 4];
mb_mapping->tab_registers[mapping_address] = data;
memcpy(rsp, req, req_length);
rsp_length = req_length;
}
}
break;
case MODBUS_FC_WRITE_MULTIPLE_COILS: {
int nb = (req[offset + 3] << 8) + req[offset + 4];
int mapping_address = address - mb_mapping->start_bits;
if (nb < 1 || MODBUS_MAX_WRITE_BITS < nb) {
/* May be the indication has been truncated on reading because of
* invalid address (eg. nb is 0 but the request contains values to
* write) so it's necessary to flush. */
rsp_length = response_exception(
ctx, &sft, MODBUS_EXCEPTION_ILLEGAL_DATA_VALUE, rsp, TRUE,
"Illegal number of values %d in write_bits (max %d)\n",
nb, MODBUS_MAX_WRITE_BITS);
} else if (mapping_address < 0 ||
(mapping_address + nb) > mb_mapping->nb_bits) {
rsp_length = response_exception(
ctx, &sft,
MODBUS_EXCEPTION_ILLEGAL_DATA_ADDRESS, rsp, FALSE,
"Illegal data address 0x%0X in write_bits\n",
mapping_address < 0 ? address : address + nb);
} else {
/* 6 = byte count */
modbus_set_bits_from_bytes(mb_mapping->tab_bits, mapping_address, nb,
&req[offset + 6]);
rsp_length = ctx->backend->build_response_basis(&sft, rsp);
/* 4 to copy the bit address (2) and the quantity of bits */
memcpy(rsp + rsp_length, req + rsp_length, 4);
rsp_length += 4;
}
}
break;
case MODBUS_FC_WRITE_MULTIPLE_REGISTERS: {
int nb = (req[offset + 3] << 8) + req[offset + 4];
int mapping_address = address - mb_mapping->start_registers;
if (nb < 1 || MODBUS_MAX_WRITE_REGISTERS < nb) {
rsp_length = response_exception(
ctx, &sft, MODBUS_EXCEPTION_ILLEGAL_DATA_VALUE, rsp, TRUE,
"Illegal number of values %d in write_registers (max %d)\n",
nb, MODBUS_MAX_WRITE_REGISTERS);
} else if (mapping_address < 0 ||
(mapping_address + nb) > mb_mapping->nb_registers) {
rsp_length = response_exception(
ctx, &sft, MODBUS_EXCEPTION_ILLEGAL_DATA_ADDRESS, rsp, FALSE,
"Illegal data address 0x%0X in write_registers\n",
mapping_address < 0 ? address : address + nb);
} else {
int i, j;
for (i = mapping_address, j = 6; i < mapping_address + nb; i++, j += 2) {
/* 6 and 7 = first value */
mb_mapping->tab_registers[i] =
(req[offset + j] << 8) + req[offset + j + 1];
}
rsp_length = ctx->backend->build_response_basis(&sft, rsp);
/* 4 to copy the address (2) and the no. of registers */
memcpy(rsp + rsp_length, req + rsp_length, 4);
rsp_length += 4;
}
}
break;
case MODBUS_FC_REPORT_SLAVE_ID: {
int str_len;
int byte_count_pos;
rsp_length = ctx->backend->build_response_basis(&sft, rsp);
/* Skip byte count for now */
byte_count_pos = rsp_length++;
rsp[rsp_length++] = _REPORT_SLAVE_ID;
/* Run indicator status to ON */
rsp[rsp_length++] = 0xFF;
/* LMB + length of LIBMODBUS_VERSION_STRING */
str_len = 3 + strlen(LIBMODBUS_VERSION_STRING);
memcpy(rsp + rsp_length, "LMB" LIBMODBUS_VERSION_STRING, str_len);
rsp_length += str_len;
rsp[byte_count_pos] = rsp_length - byte_count_pos - 1;
}
break;
case MODBUS_FC_READ_EXCEPTION_STATUS:
if (ctx->debug) {
fprintf(stderr, "FIXME Not implemented\n");
}
errno = ENOPROTOOPT;
return -1;
break;
case MODBUS_FC_MASK_WRITE_REGISTER: {
int mapping_address = address - mb_mapping->start_registers;
if (mapping_address < 0 || mapping_address >= mb_mapping->nb_registers) {
rsp_length = response_exception(
ctx, &sft, MODBUS_EXCEPTION_ILLEGAL_DATA_ADDRESS, rsp, FALSE,
"Illegal data address 0x%0X in write_register\n",
address);
} else {
uint16_t data = mb_mapping->tab_registers[mapping_address];
uint16_t and = (req[offset + 3] << 8) + req[offset + 4];
uint16_t or = (req[offset + 5] << 8) + req[offset + 6];
data = (data & and) | (or & (~and));
mb_mapping->tab_registers[mapping_address] = data;
memcpy(rsp, req, req_length);
rsp_length = req_length;
}
}
break;
case MODBUS_FC_WRITE_AND_READ_REGISTERS: {
int nb = (req[offset + 3] << 8) + req[offset + 4];
uint16_t address_write = (req[offset + 5] << 8) + req[offset + 6];
int nb_write = (req[offset + 7] << 8) + req[offset + 8];
int nb_write_bytes = req[offset + 9];
int mapping_address = address - mb_mapping->start_registers;
int mapping_address_write = address_write - mb_mapping->start_registers;
if (nb_write < 1 || MODBUS_MAX_WR_WRITE_REGISTERS < nb_write ||
nb < 1 || MODBUS_MAX_WR_READ_REGISTERS < nb ||
nb_write_bytes != nb_write * 2) {
rsp_length = response_exception(
ctx, &sft, MODBUS_EXCEPTION_ILLEGAL_DATA_VALUE, rsp, TRUE,
"Illegal nb of values (W%d, R%d) in write_and_read_registers (max W%d, R%d)\n",
nb_write, nb, MODBUS_MAX_WR_WRITE_REGISTERS, MODBUS_MAX_WR_READ_REGISTERS);
} else if (mapping_address < 0 ||
(mapping_address + nb) > mb_mapping->nb_registers ||
mapping_address < 0 ||
(mapping_address_write + nb_write) > mb_mapping->nb_registers) {
rsp_length = response_exception(
ctx, &sft, MODBUS_EXCEPTION_ILLEGAL_DATA_ADDRESS, rsp, FALSE,
"Illegal data read address 0x%0X or write address 0x%0X write_and_read_registers\n",
mapping_address < 0 ? address : address + nb,
mapping_address_write < 0 ? address_write : address_write + nb_write);
} else {
int i, j;
rsp_length = ctx->backend->build_response_basis(&sft, rsp);
rsp[rsp_length++] = nb << 1;
/* Write first.
10 and 11 are the offset of the first values to write */
for (i = mapping_address_write, j = 10;
i < mapping_address_write + nb_write; i++, j += 2) {
mb_mapping->tab_registers[i] =
(req[offset + j] << 8) + req[offset + j + 1];
}
/* and read the data for the response */
for (i = mapping_address; i < mapping_address + nb; i++) {
rsp[rsp_length++] = mb_mapping->tab_registers[i] >> 8;
rsp[rsp_length++] = mb_mapping->tab_registers[i] & 0xFF;
}
}
}
break;
default:
rsp_length = response_exception(
ctx, &sft, MODBUS_EXCEPTION_ILLEGAL_FUNCTION, rsp, TRUE,
"Unknown Modbus function code: 0x%0X\n", function);
break;
}
/* Suppress any responses when the request was a broadcast */
return (slave == MODBUS_BROADCAST_ADDRESS) ? 0 : send_msg(ctx, rsp, rsp_length);
}
int modbus_reply_exception(modbus_t *ctx, const uint8_t *req,
unsigned int exception_code)
{
int offset;
int slave;
int function;
uint8_t rsp[MAX_MESSAGE_LENGTH];