AX25Control.cpp

/*
 *	Copyright (C) 2020 Jonathan Naylor, G4KLX
 *
 *	This program is free software; you can redistribute it and/or modify
 *	it under the terms of the GNU General Public License as published by
 *	the Free Software Foundation; version 2 of the License.
 *
 *	This program is distributed in the hope that it will be useful,
 *	but WITHOUT ANY WARRANTY; without even the implied warranty of
 *	MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 *	GNU General Public License for more details.
 */

#include "AX25Control.h"
#include "AX25Defines.h"
#include "Utils.h"
#include "Log.h"

#include <cstdio>
#include <cassert>
#include <cstring>
#include <ctime>

// #define	DUMP_AX25

const unsigned char BIT_MASK_TABLE[] = { 0x80U, 0x40U, 0x20U, 0x10U, 0x08U, 0x04U, 0x02U, 0x01U };

#define WRITE_BIT1(p,i,b) p[(i)>>3] = (b) ? (p[(i)>>3] | BIT_MASK_TABLE[(i)&7]) : (p[(i)>>3] & ~BIT_MASK_TABLE[(i)&7])
#define READ_BIT1(p,i)    (p[(i)>>3] & BIT_MASK_TABLE[(i)&7])

CAX25Control::CAX25Control(CAX25Network* network, bool trace) :
m_network(network),
m_trace(trace),
m_enabled(true),
m_fp(NULL)
{
}

CAX25Control::~CAX25Control()
{
}

bool CAX25Control::writeModem(unsigned char *data, unsigned int len)
{
	assert(data != NULL);

	if (!m_enabled)
		return false;

    if (m_trace)
        decode(data, len);

    CUtils::dump(1U, "AX.25 received packet", data, len);

    if (m_network == NULL)
        return true;

    return m_network->write(data, len);
}

unsigned int CAX25Control::readModem(unsigned char* data)
{
    assert(data != NULL);

    if (m_network == NULL)
        return 0U;

    if (!m_enabled)
        return 0U;

    unsigned int length = m_network->read(data, 500U);

    if (length > 0U)
        CUtils::dump(1U, "AX.25 transmitted packet", data, length);

    return length;
}

bool CAX25Control::openFile()
{
	if (m_fp != NULL)
		return true;

	time_t t;
	::time(&t);

	struct tm* tm = ::localtime(&t);

	char name[100U];
	::sprintf(name, "AX25_%04d%02d%02d_%02d%02d%02d.ambe", tm->tm_year + 1900, tm->tm_mon + 1, tm->tm_mday, tm->tm_hour, tm->tm_min, tm->tm_sec);

	m_fp = ::fopen(name, "wb");
	if (m_fp == NULL)
		return false;

	::fwrite("AX25", 1U, 4U, m_fp);

	return true;
}

bool CAX25Control::writeFile(const unsigned char* data, unsigned int length)
{
	if (m_fp == NULL)
		return false;

	::fwrite(&length, 1U, sizeof(unsigned int), m_fp);
	::fwrite(data, 1U, length, m_fp);

	return true;
}

void CAX25Control::closeFile()
{
	if (m_fp != NULL) {
		::fclose(m_fp);
		m_fp = NULL;
	}
}

void CAX25Control::enable(bool enabled)
{
	m_enabled = enabled;
}

void CAX25Control::decode(const unsigned char* data, unsigned int length)
{
    assert(data != NULL);
    assert(length >= 15U);

    std::string text;

    bool more = decodeAddress(data + 7U, text);

    text += '>';

    decodeAddress(data + 0U, text);

    unsigned int n = 14U;
    while (more && n < length) {
        text += ',';
        more = decodeAddress(data + n, text, true);
        n += 7U;
    }

    text += ' ';

    if ((data[n] & 0x01U) == 0x00U) {
        // I frame
        char t[20U];
        ::sprintf(t, "<I S%u R%u>", (data[n] >> 1) & 0x07U, (data[n] >> 5) & 0x07U);
        text += t;
    } else {
        if ((data[n] & 0x02U) == 0x00U) {
            // S frame
            char t[20U];
            switch (data[n] & 0x0FU) {
            case 0x01U:
                sprintf(t, "<RR R%u>", (data[n] >> 5) & 0x07U);
                break;
            case 0x05U:
                sprintf(t, "<RNR R%u>", (data[n] >> 5) & 0x07U);
                break;
            case 0x09U:
                sprintf(t, "<REJ R%u>", (data[n] >> 5) & 0x07U);
                break;
            case 0x0DU:
                sprintf(t, "<SREJ R%u>", (data[n] >> 5) & 0x07U);
                break;
            default:
                sprintf(t, "<Unknown R%u>", (data[n] >> 5) & 0x07U);
                break;
            }

            text += t;
            LogMessage("AX.25, %s", text.c_str());
            return;
        } else {
            // U frame
            switch (data[n] & 0xEFU) {
            case 0x6FU:
                text += "<SABME>";
                break;
            case 0x2FU:
                text += "<SABM>";
                break;
            case 0x43U:
                text += "<DISC>";
                break;
            case 0x0FU:
                text += "<DM>";
                break;
            case 0x63U:
                text += "<UA>";
                break;
            case 0x87U:
                text += "<FRMR>";
                break;
            case 0x03U:
                text += "<UI>";
                break;
            case 0xAFU:
                text += "<XID>";
                break;
            case 0xE3U:
                text += "<TEST>";
                break;
            default:
                text += "<Unknown>";
                break;
            }

            if ((data[n] & 0xEFU) != 0x03U) {
                LogMessage("AX.25, %s", text.c_str());
                return;
            }
        }
    }

    n += 2U;

    LogMessage("AX.25, %s %.*s", text.c_str(), length - n, data + n);
}

bool CAX25Control::decodeAddress(const unsigned char* data, std::string& text, bool isDigi) const
{
	assert(data != NULL);

	for (unsigned int i = 0U; i < 6U; i++) {
		char c = data[i] >> 1;
		if (c != ' ')
			text += c;
	}

	unsigned char ssid = (data[6U] >> 1) & 0x0FU;
	if (ssid > 0U) {
		text += '-';
		if (ssid >= 10U) {
			text += '1';
			text += '0' + ssid - 10U;
		}
		else {
			text += '0' + ssid;
		}
	}

	if (isDigi) {
		if ((data[6U] & 0x80U) == 0x80U)
			text += '*';
	}

	return (data[6U] & 0x01U) == 0x00U;
}