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direwolf/kiss_frame.c

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//
// This file is part of Dire Wolf, an amateur radio packet TNC.
//
// Copyright (C) 2013 John Langner, WB2OSZ
//
// 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, either version 2 of the License, or
// (at your option) any later version.
//
// 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.
//
// You should have received a copy of the GNU General Public License
// along with this program. If not, see <http://www.gnu.org/licenses/>.
//
/*------------------------------------------------------------------
*
* Module: kiss_frame.c
*
* Purpose: Common code used by Serial port and network versions of KISS protocol.
*
* Description: The KISS TNS protocol is described in http://www.ka9q.net/papers/kiss.html
*
* Briefly, a frame is composed of
*
* * FEND (0xC0)
* * Contents - with special escape sequences so a 0xc0
* byte in the data is not taken as end of frame.
* as part of the data.
* * FEND
*
* The first byte of the frame contains:
*
* * port number in upper nybble.
* * command in lower nybble.
*
*
* Commands from application recognized:
*
* 0 Data Frame AX.25 frame in raw format.
*
* 1 TXDELAY See explanation in xmit.c.
*
* 2 Persistence " "
*
* 3 SlotTime " "
*
* 4 TXtail " "
* Spec says it is obsolete but Xastir
* sends it and we respect it.
*
* 5 FullDuplex Ignored. Always full duplex.
*
* 6 SetHardware TNC specific. Ignored.
*
* FF Return Exit KISS mode. Ignored.
*
*
* Messages sent to client application:
*
* 0 Data Frame Received AX.25 frame in raw format.
*
*---------------------------------------------------------------*/
#include <stdio.h>
#include <unistd.h>
#include <stdlib.h>
#include <ctype.h>
#include <assert.h>
#include <string.h>
#include "direwolf.h"
#include "ax25_pad.h"
#include "textcolor.h"
#include "kiss_frame.h"
#include "tq.h"
#include "xmit.h"
/*-------------------------------------------------------------------
*
* Name: kiss_frame
*
* Purpose: Extract a KISS frame from byte stream.
*
* Inputs: kf - Current state of building a frame.
* ch - A byte from the input stream.
* debug - Activates debug output.
* sendfun - Function to send something to the client application.
*
* Outputs: kf - Current state is updated.
*
* Returns: TRUE when a complete frame is ready for processing.
*
* Bug: For send, the debug output shows exactly what is
* being sent including the surrounding FEND and any
* escapes. For receive, we don't show those.
*
*-----------------------------------------------------------------*/
/*
* Application might send some commands to put TNC into KISS mode.
* For example, APRSIS32 sends something like:
*
* <0x0d>
* <0x0d>
* XFLOW OFF<0x0d>
* FULLDUP OFF<0x0d>
* KISS ON<0x0d>
* RESTART<0x0d>
* <0x03><0x03><0x03>
* TC 1<0x0d>
* TN 2,0<0x0d><0x0d><0x0d>
* XFLOW OFF<0x0d>
* FULLDUP OFF<0x0d>
* KISS ON<0x0d>
* RESTART<0x0d>
*
* This keeps repeating over and over and over and over again if
* it doesn't get any sort of response.
*
* Let's try to keep it happy by sending back a command prompt.
*/
int kiss_frame (kiss_frame_t *kf, unsigned char ch, int debug, void (*sendfun)(int,unsigned char*,int))
{
switch (kf->state) {
case KS_SEARCHING: /* Searching for starting FEND. */
if (ch == FEND) {
/* Start of frame. But first print any collected noise for debugging. */
if (kf->noise_len > 0) {
if (debug) {
kiss_debug_print (FROM_CLIENT, "Rejected Noise", kf->noise, kf->noise_len);
}
kf->noise_len = 0;
}
kf->kiss_len = 0;
kf->state = KS_COLLECTING;
return 0;
}
/* Noise to be rejected. */
if (kf->noise_len < MAX_NOISE_LEN) {
kf->noise[kf->noise_len++] = ch;
}
if (ch == '\r') {
if (debug) {
kiss_debug_print (FROM_CLIENT, "Rejected Noise", kf->noise, kf->noise_len);
kf->noise[kf->noise_len] = '\0';
}
/* Try to appease it by sending something back. */
if (strcasecmp("restart\r", (char*)(kf->noise)) == 0 ||
strcasecmp("reset\r", (char*)(kf->noise)) == 0) {
(*sendfun) (0, (unsigned char *)"\xc0\xc0", -1);
}
else {
(*sendfun) (0, (unsigned char *)"\r\ncmd:", -1);
}
kf->noise_len = 0;
}
return 0;
case KS_COLLECTING: /* Frame collection in progress. */
if (ch == FEND) {
/* End of frame. */
if (kf->kiss_len == 0) {
/* Empty frame. Just go on collecting. */
return 0;
}
if (debug) {
kiss_debug_print (FROM_CLIENT, NULL, kf->kiss_msg, kf->kiss_len);
}
kf->state = KS_SEARCHING;
return 1;
}
if (kf->kiss_len < MAX_KISS_LEN) {
kf->kiss_msg[kf->kiss_len++] = ch;
}
else {
text_color_set(DW_COLOR_ERROR);
dw_printf ("KISS message exceeded maximum length.\n");
}
return 0;
case KS_ESCAPE: /* Expecting TFESC or TFEND. */
if (kf->kiss_len >= MAX_KISS_LEN) {
text_color_set(DW_COLOR_ERROR);
dw_printf ("KISS message exceeded maximum length.\n");
kf->state = KS_COLLECTING;
return 0;
}
if (ch == TFESC) {
kf->kiss_msg[kf->kiss_len++] = FESC;
}
else if (ch == TFEND) {
kf->kiss_msg[kf->kiss_len++] = FEND;
}
else {
text_color_set(DW_COLOR_ERROR);
dw_printf ("KISS protocol error. TFESC or TFEND expected.\n");
}
kf->state = KS_COLLECTING;
return 0;
}
return 0; /* unreachable but suppress compiler warning. */
} /* end kiss_frame */
/*-------------------------------------------------------------------
*
* Name: kiss_process_msg
*
* Purpose: Process a message from the KISS client.
*
* Inputs: kf - Current state of building a frame.
* Should be complete.
*
* debug - Debug option is selected.
*
*-----------------------------------------------------------------*/
void kiss_process_msg (kiss_frame_t *kf, int debug)
{
int port;
int cmd;
packet_t pp;
port = (kf->kiss_msg[0] >> 4) & 0xf;
cmd = kf->kiss_msg[0] & 0xf;
switch (cmd)
{
case 0: /* Data Frame */
/* Special hack - Discard apparently bad data from Linux AX25. */
if ((port == 2 || port == 8) &&
kf->kiss_msg[1] == 'Q' << 1 &&
kf->kiss_msg[2] == 'S' << 1 &&
kf->kiss_msg[3] == 'T' << 1 &&
kf->kiss_msg[4] == ' ' << 1 &&
kf->kiss_msg[15] == 3 &&
kf->kiss_msg[16] == 0xcd) {
if (debug) {
text_color_set(DW_COLOR_ERROR);
dw_printf ("Special case - Drop packets which appear to be in error.\n");
}
return;
}
pp = ax25_from_frame (kf->kiss_msg+1, kf->kiss_len-1, -1);
if (pp == NULL) {
text_color_set(DW_COLOR_ERROR);
dw_printf ("ERROR - Invalid KISS data frame from client app.\n");
}
else {
/* How can we determine if it is an original or repeated message? */
/* If there is at least one digipeater in the frame, AND */
/* that digipeater has been used, it should go out quickly thru */
/* the high priority queue. */
/* Otherwise, it is an original for the low priority queue. */
if (ax25_get_num_repeaters(pp) >= 1 &&
ax25_get_h(pp,AX25_REPEATER_1)) {
tq_append (port, TQ_PRIO_0_HI, pp);
}
else {
tq_append (port, TQ_PRIO_1_LO, pp);
}
}
break;
case 1: /* TXDELAY */
text_color_set(DW_COLOR_INFO);
dw_printf ("KISS protocol set TXDELAY = %d, port %d\n", kf->kiss_msg[1], port);
xmit_set_txdelay (port, kf->kiss_msg[1]);
break;
case 2: /* Persistence */
text_color_set(DW_COLOR_INFO);
dw_printf ("KISS protocol set Persistence = %d, port %d\n", kf->kiss_msg[1], port);
xmit_set_persist (port, kf->kiss_msg[1]);
break;
case 3: /* SlotTime */
text_color_set(DW_COLOR_INFO);
dw_printf ("KISS protocol set SlotTime = %d, port %d\n", kf->kiss_msg[1], port);
xmit_set_slottime (port, kf->kiss_msg[1]);
break;
case 4: /* TXtail */
text_color_set(DW_COLOR_INFO);
dw_printf ("KISS protocol set TXtail = %d, port %d\n", kf->kiss_msg[1], port);
xmit_set_txtail (port, kf->kiss_msg[1]);
break;
case 5: /* FullDuplex */
text_color_set(DW_COLOR_INFO);
dw_printf ("KISS protocol set FullDuplex = %d, port %d\n", kf->kiss_msg[1], port);
break;
case 6: /* TNC specific */
text_color_set(DW_COLOR_INFO);
dw_printf ("KISS protocol set hardware - ignored.\n");
break;
case 15: /* End KISS mode, port should be 15. */
/* Ignore it. */
text_color_set(DW_COLOR_INFO);
dw_printf ("KISS protocol end KISS mode\n");
break;
default:
text_color_set(DW_COLOR_DEBUG);
dw_printf ("KISS Invalid command %d\n", cmd);
kiss_debug_print (FROM_CLIENT, NULL, kf->kiss_msg, kf->kiss_len);
break;
}
} /* end kiss_process_msg */
/*-------------------------------------------------------------------
*
* Name: kiss_debug_print
*
* Purpose: Print message to/from client for debugging.
*
* Inputs: fromto - Direction of message.
* special - Comment if not a KISS frame.
* pmsg - Address of the message block.
* msg_len - Length of the message.
*
*--------------------------------------------------------------------*/
/* In server.c. Should probably move to some misc. function file. */
void hex_dump (unsigned char *p, int len);
void kiss_debug_print (fromto_t fromto, char *special, unsigned char *pmsg, int msg_len)
{
const char *direction [2] = { "from", "to" };
const char *prefix [2] = { "<<<", ">>>" };
const char *function[16] = {
"Data frame", "TXDELAY", "P", "SlotTime",
"TXtail", "FullDuplex", "SetHardware", "Invalid 7",
"Invalid 8", "Invalid 9", "Invalid 10", "Invalid 11",
"Invalid 12", "Invalid 13", "Invalid 14", "Return" };
text_color_set(DW_COLOR_DEBUG);
dw_printf ("\n");
if (special == NULL) {
dw_printf ("%s %s %s KISS client application, port %d, total length = %d\n",
prefix[(int)fromto], function[pmsg[0] & 0xf], direction[(int)fromto],
(pmsg[0] >> 4) & 0xf, msg_len);
}
else {
dw_printf ("%s %s %s KISS client application, total length = %d\n",
prefix[(int)fromto], special, direction[(int)fromto],
msg_len);
}
hex_dump ((char*)pmsg, msg_len);
} /* end kiss_debug_print */
/* end kiss_frame.c */
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