330 lines
8.2 KiB
C
330 lines
8.2 KiB
C
/**
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* \file
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* <!--
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* This file is part of BeRTOS.
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*
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* Bertos is free software; you can redistribute it and/or modify
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* it under the terms of the GNU General Public License as published by
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* the Free Software Foundation; either version 2 of the License, or
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* (at your option) any later version.
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*
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* This program is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License
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* along with this program; if not, write to the Free Software
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* Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA
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*
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* As a special exception, you may use this file as part of a free software
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* library without restriction. Specifically, if other files instantiate
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* templates or use macros or inline functions from this file, or you compile
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* this file and link it with other files to produce an executable, this
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* file does not by itself cause the resulting executable to be covered by
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* the GNU General Public License. This exception does not however
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* invalidate any other reasons why the executable file might be covered by
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* the GNU General Public License.
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*
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* Copyright 2009 Develer S.r.l. (http://www.develer.com/)
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*
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* -->
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* \brief Simple AX25 data link layer implementation.
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*
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* For now, only UI frames without any Layer 3 protocol are handled.
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* This however is enough to send/receive APRS packets.
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*
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* \author Francesco Sacchi <batt@develer.com>
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*
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*/
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#include "ax25.h"
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#include "cfg/cfg_ax25.h"
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#include <algo/crc_ccitt.h>
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#define LOG_LEVEL AX25_LOG_LEVEL
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#define LOG_FORMAT AX25_LOG_FORMAT
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#include <cfg/log.h>
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#include <string.h> //memset, memcmp
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#include <ctype.h> //isalnum, toupper
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#if CONFIG_AX25_RPT_LST
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#define AX25_SET_REPEATED(msg, idx, val) \
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do \
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{ \
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if (val) \
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(msg)->rpt_flags |= BV(idx) ; \
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else \
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(msg)->rpt_flags &= ~BV(idx) ; \
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} while(0)
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#endif
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#define DECODE_CALL(buf, addr) \
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for (unsigned i = 0; i < sizeof((addr)); i++) \
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{ \
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char c = (*(buf)++ >> 1); \
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(addr)[i] = (c == ' ') ? '\x0' : c; \
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}
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static void ax25_decode(AX25Ctx *ctx)
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{
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AX25Msg msg;
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uint8_t *buf = ctx->buf;
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DECODE_CALL(buf, msg.dst.call);
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msg.dst.ssid = (*buf++ >> 1) & 0x0F;
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DECODE_CALL(buf, msg.src.call);
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msg.src.ssid = (*buf >> 1) & 0x0F;
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LOG_INFO("SRC[%.6s-%d], DST[%.6s-%d]\n", msg.src.call, msg.src.ssid, msg.dst.call, msg.dst.ssid);
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/* Repeater addresses */
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#if CONFIG_AX25_RPT_LST
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for (msg.rpt_cnt = 0; !(*buf++ & 0x01) && (msg.rpt_cnt < countof(msg.rpt_lst)); msg.rpt_cnt++)
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{
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DECODE_CALL(buf, msg.rpt_lst[msg.rpt_cnt].call);
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msg.rpt_lst[msg.rpt_cnt].ssid = (*buf >> 1) & 0x0F;
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AX25_SET_REPEATED(&msg, msg.rpt_cnt, (*buf & 0x80));
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LOG_INFO("RPT%d[%.6s-%d]%c\n", msg.rpt_cnt,
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msg.rpt_lst[msg.rpt_cnt].call,
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msg.rpt_lst[msg.rpt_cnt].ssid,
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(AX25_REPEATED(&msg, msg.rpt_cnt) ? '*' : ' '));
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}
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#else
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while (!(*buf++ & 0x01))
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{
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char rpt[6];
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uint8_t ssid;
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DECODE_CALL(buf, rpt);
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ssid = (*buf >> 1) & 0x0F;
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LOG_INFO("RPT[%.6s-%d]\n", rpt, ssid);
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}
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#endif
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msg.ctrl = *buf++;
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if (msg.ctrl != AX25_CTRL_UI)
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{
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LOG_WARN("Only UI frames are handled, got [%02X]\n", msg.ctrl);
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return;
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}
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msg.pid = *buf++;
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if (msg.pid != AX25_PID_NOLAYER3)
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{
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LOG_WARN("Only frames without layer3 protocol are handled, got [%02X]\n", msg.pid);
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return;
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}
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msg.len = ctx->frm_len - 2 - (buf - ctx->buf);
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msg.info = buf;
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LOG_INFO("DATA: %.*s\n", msg.len, msg.info);
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if (ctx->hook)
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ctx->hook(&msg);
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}
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/**
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* Check if there are any AX25 messages to be processed.
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* This function read available characters from the medium and search for
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* any AX25 messages.
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* If a message is found it is decoded and the linked callback executed.
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* This function may be blocking if there are no available chars and the KFile
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* used in \a ctx to access the medium is configured in blocking mode.
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*
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* \param ctx AX25 context to operate on.
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*/
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void ax25_poll(AX25Ctx *ctx)
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{
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int c;
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while ((c = kfile_getc(ctx->ch)) != EOF)
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{
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if (!ctx->escape && c == HDLC_FLAG)
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{
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if (ctx->frm_len >= AX25_MIN_FRAME_LEN)
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{
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if (ctx->crc_in == AX25_CRC_CORRECT)
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{
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LOG_INFO("Frame found!\n");
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ax25_decode(ctx);
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}
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else
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{
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LOG_INFO("CRC error, computed [%04X]\n", ctx->crc_in);
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}
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}
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ctx->sync = true;
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ctx->crc_in = CRC_CCITT_INIT_VAL;
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ctx->frm_len = 0;
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continue;
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}
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if (!ctx->escape && c == HDLC_RESET)
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{
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LOG_INFO("HDLC reset\n");
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ctx->sync = false;
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continue;
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}
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if (!ctx->escape && c == AX25_ESC)
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{
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ctx->escape = true;
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continue;
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}
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if (ctx->sync)
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{
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if (ctx->frm_len < CONFIG_AX25_FRAME_BUF_LEN)
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{
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ctx->buf[ctx->frm_len++] = c;
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ctx->crc_in = updcrc_ccitt(c, ctx->crc_in);
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}
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else
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{
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LOG_INFO("Buffer overrun");
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ctx->sync = false;
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}
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}
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ctx->escape = false;
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}
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if (kfile_error(ctx->ch))
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{
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LOG_ERR("Channel error [%04x]\n", kfile_error(ctx->ch));
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kfile_clearerr(ctx->ch);
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}
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}
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static void ax25_putchar(AX25Ctx *ctx, uint8_t c)
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{
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if (c == HDLC_FLAG || c == HDLC_RESET
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|| c == AX25_ESC)
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kfile_putc(AX25_ESC, ctx->ch);
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ctx->crc_out = updcrc_ccitt(c, ctx->crc_out);
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kfile_putc(c, ctx->ch);
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}
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static void ax25_sendCall(AX25Ctx *ctx, const AX25Call *addr, bool last)
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{
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unsigned len = MIN(sizeof(addr->call), strlen(addr->call));
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for (unsigned i = 0; i < len; i++)
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{
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uint8_t c = addr->call[i];
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ASSERT(isalnum(c) || c == ' ');
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c = toupper(c);
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ax25_putchar(ctx, c << 1);
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}
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/* Fill with spaces the rest of the CALL if it's shorter */
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if (len < sizeof(addr->call))
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for (unsigned i = 0; i < sizeof(addr->call) - len; i++)
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ax25_putchar(ctx, ' ' << 1);
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/* The bit7 "has-been-repeated" flag is not implemented here */
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/* Bits6:5 should be set to 1 for all SSIDs (0x60) */
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/* The bit0 of last call SSID should be set to 1 */
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uint8_t ssid = 0x60 | (addr->ssid << 1) | (last ? 0x01 : 0);
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ax25_putchar(ctx, ssid);
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}
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/**
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* Send an AX25 frame on the channel through a specific path.
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* \param ctx AX25 context to operate on.
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* \param path An array of callsigns used as path, \see AX25_PATH for
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* an handy way to create a path.
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* \param path_len callsigns path lenght.
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* \param _buf payload buffer.
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* \param len length of the payload.
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*/
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void ax25_sendVia(AX25Ctx *ctx, const AX25Call *path, size_t path_len, const void *_buf, size_t len)
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{
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const uint8_t *buf = (const uint8_t *)_buf;
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ASSERT(path);
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ASSERT(path_len >= 2);
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ctx->crc_out = CRC_CCITT_INIT_VAL;
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kfile_putc(HDLC_FLAG, ctx->ch);
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/* Send call */
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for (size_t i = 0; i < path_len; i++)
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ax25_sendCall(ctx, &path[i], (i == path_len - 1));
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ax25_putchar(ctx, AX25_CTRL_UI);
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ax25_putchar(ctx, AX25_PID_NOLAYER3);
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while (len--)
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ax25_putchar(ctx, *buf++);
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/*
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* According to AX25 protocol,
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* CRC is sent in reverse order!
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*/
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uint8_t crcl = (ctx->crc_out & 0xff) ^ 0xff;
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uint8_t crch = (ctx->crc_out >> 8) ^ 0xff;
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ax25_putchar(ctx, crcl);
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ax25_putchar(ctx, crch);
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ASSERT(ctx->crc_out == AX25_CRC_CORRECT);
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kfile_putc(HDLC_FLAG, ctx->ch);
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}
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static void print_call(KFile *ch, const AX25Call *call)
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{
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kfile_printf(ch, "%.6s", call->call);
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if (call->ssid)
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kfile_printf(ch, "-%d", call->ssid);
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}
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/**
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* Print a AX25 message in TNC-2 packet monitor format.
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* \param ch a kfile channel where the message will be printed.
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* \param msg the message to be printed.
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*/
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void ax25_print(KFile *ch, const AX25Msg *msg)
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{
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print_call(ch, &msg->src);
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kfile_putc('>', ch);
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print_call(ch, &msg->dst);
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#if CONFIG_AX25_RPT_LST
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for (int i = 0; i < msg->rpt_cnt; i++)
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{
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kfile_putc(',', ch);
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print_call(ch, &msg->rpt_lst[i]);
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/* Print a '*' if packet has already been transmitted
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* by this repeater */
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if (AX25_REPEATED(msg, i))
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kfile_putc('*', ch);
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}
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#endif
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kfile_printf(ch, ":%.*s\n", msg->len, msg->info);
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}
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/**
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* Init the AX25 protocol decoder.
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*
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* \param ctx AX25 context to init.
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* \param channel Used to gain access to the physical medium
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* \param hook Callback function called when a message is received
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*/
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void ax25_init(AX25Ctx *ctx, KFile *channel, ax25_callback_t hook)
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{
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ASSERT(ctx);
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ASSERT(channel);
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memset(ctx, 0, sizeof(*ctx));
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ctx->ch = channel;
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ctx->hook = hook;
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ctx->crc_in = ctx->crc_out = CRC_CCITT_INIT_VAL;
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}
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