libmbus/mbus/mbus-tcp.c

//------------------------------------------------------------------------------
// Copyright (C) 2011, Robert Johansson, Raditex AB
// All rights reserved.
//
// rSCADA 
// http://www.rSCADA.se
// info@rscada.se
//
//------------------------------------------------------------------------------

#include <unistd.h>
#include <limits.h>
#include <fcntl.h>

#include <sys/socket.h>
#include <sys/types.h>

#include <arpa/inet.h>
#include <netinet/in.h>
#include <netdb.h>

#include <stdio.h>
#include <string.h>
#include <strings.h>
#include <errno.h>

#include "mbus-tcp.h"

#define PACKET_BUFF_SIZE 2048

//------------------------------------------------------------------------------
/// Setup a TCP/IP handle.
//------------------------------------------------------------------------------
int
mbus_tcp_connect(mbus_handle *handle)
{
    char error_str[128], *host;
    struct hostent *host_addr;
    struct sockaddr_in s;
    struct timeval time_out;
    mbus_tcp_data *tcp_data;
    uint16_t port;

    if (handle == NULL)
        return -1;

    tcp_data = (mbus_tcp_data *) handle->auxdata;
    if (tcp_data == NULL || tcp_data->host == NULL)
        return -1;

    host = tcp_data->host;
    port = tcp_data->port;

    //
    // create the TCP connection
    //
    if ((handle->fd = socket(AF_INET,SOCK_STREAM, 0)) < 0)
    {
        snprintf(error_str, sizeof(error_str), "%s: failed to setup a socket.", __PRETTY_FUNCTION__);
        mbus_error_str_set(error_str);
        return -1;
    }

    s.sin_family = AF_INET;
    s.sin_port = htons(port);

    /* resolve hostname */
    if ((host_addr = gethostbyname(host)) == NULL)
    {
        snprintf(error_str, sizeof(error_str), "%s: unknown host: %s", __PRETTY_FUNCTION__, host);
        mbus_error_str_set(error_str);
        return -1;
    }

    memcpy((void *)(&s.sin_addr), (void *)(host_addr->h_addr), host_addr->h_length);

    if (connect(handle->fd, (struct sockaddr *)&s, sizeof(s)) < 0)
    {
        snprintf(error_str, sizeof(error_str), "%s: Failed to establish connection to %s:%d", __PRETTY_FUNCTION__, host, port);
        mbus_error_str_set(error_str);
        return -1;
    }

    // Set a timeout
    time_out.tv_sec  = 4; //seconds
    time_out.tv_usec = 0;
    setsockopt(handle->fd, SOL_SOCKET, SO_SNDTIMEO, &time_out, sizeof(time_out));
    setsockopt(handle->fd, SOL_SOCKET, SO_RCVTIMEO, &time_out, sizeof(time_out));

    return 0;
}

void
mbus_tcp_data_free(mbus_handle *handle)
{
    mbus_tcp_data *tcp_data;

    if (handle)
    {
        tcp_data = (mbus_tcp_data *) handle->auxdata;
        
        if (tcp_data == NULL)
        {
            return;
        }
        
        free(tcp_data->host);
        free(tcp_data);
        handle->auxdata = NULL;
    }
}

//------------------------------------------------------------------------------
//
//------------------------------------------------------------------------------
int
mbus_tcp_disconnect(mbus_handle *handle)
{
    if (handle == NULL)
    {
        return -1;
    }

    close(handle->fd);

    return 0;
}

//------------------------------------------------------------------------------
//
//------------------------------------------------------------------------------
int
mbus_tcp_send_frame(mbus_handle *handle, mbus_frame *frame)
{
    unsigned char buff[PACKET_BUFF_SIZE];
    int len, ret;
    char error_str[128];

    if (handle == NULL || frame == NULL)
    {
        return -1;
    }

    if ((len = mbus_frame_pack(frame, buff, sizeof(buff))) == -1)
    {
        snprintf(error_str, sizeof(error_str), "%s: mbus_frame_pack failed\n", __PRETTY_FUNCTION__);
        mbus_error_str_set(error_str);
        return -1;
    }

    if ((ret = write(handle->fd, buff, len)) == len)
    {
        //
        // call the send event function, if the callback function is registered
        // 
        if (_mbus_send_event)
                _mbus_send_event(MBUS_HANDLE_TYPE_TCP, buff, len);
    }
    else
    {   
        snprintf(error_str, sizeof(error_str), "%s: Failed to write frame to socket (ret = %d)\n", __PRETTY_FUNCTION__, ret);
        mbus_error_str_set(error_str);
        return -1;
    }

    return 0;
}

//------------------------------------------------------------------------------
//
//------------------------------------------------------------------------------
int mbus_tcp_recv_frame(mbus_handle *handle, mbus_frame *frame)
{
    char buff[PACKET_BUFF_SIZE];
    int remaining;
    ssize_t len, nread;

    if (handle == NULL || frame == NULL) {
        fprintf(stderr, "%s: Invalid parameter.\n", __PRETTY_FUNCTION__);
        return MBUS_RECV_RESULT_ERROR;
    }

    memset((void *) buff, 0, sizeof(buff));

    //
    // read data until a packet is received
    //
    remaining = 1; // start by reading 1 byte
    len = 0;

    do {
retry:
        if (len + remaining > PACKET_BUFF_SIZE)
        {
            // avoid out of bounds access
            return MBUS_RECV_RESULT_ERROR;
        }

        nread = read(handle->fd, &buff[len], remaining);
        switch (nread) {
        case -1:
            if (errno == EINTR)
                goto retry;

            if (errno == EAGAIN || errno == EWOULDBLOCK) {
                mbus_error_str_set("M-Bus tcp transport layer response timeout has been reached.");
                return MBUS_RECV_RESULT_TIMEOUT;
            }

            mbus_error_str_set("M-Bus tcp transport layer failed to read data.");
            return MBUS_RECV_RESULT_ERROR;
        case 0:
            mbus_error_str_set("M-Bus tcp transport layer connection closed by remote host.");
            return MBUS_RECV_RESULT_RESET;
        default:
            if (len > (SSIZE_MAX-nread))
            {
                // avoid overflow
                return MBUS_RECV_RESULT_ERROR;
            }
        
            len += nread;
        }
    } while ((remaining = mbus_parse(frame, buff, len)) > 0);

    //
    // call the receive event function, if the callback function is registered
    //
    if (_mbus_recv_event)
        _mbus_recv_event(MBUS_HANDLE_TYPE_TCP, buff, len);

    if (remaining < 0) {
        mbus_error_str_set("M-Bus layer failed to parse data.");
        return MBUS_RECV_RESULT_INVALID;
    }

    return MBUS_RECV_RESULT_OK;
}