//
// This file is part of Dire Wolf, an amateur radio packet TNC.
//
// Copyright (C) 2011, 2013, 2014, 2016, 2017 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.c
*
* Purpose: Act as a virtual KISS TNC for use by other packet radio applications.
* This file implements it with a pseudo terminal for Linux only.
*
* Description: It implements the KISS TNC protocol as 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* Spec says it is obsolete but Xastir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.
*
* _6 SetHardware TNC specific.
*
* FF Return Exit KISS mode. Ignored.
*
*
* Messages sent to client application:
*
* _0 Data Frame Received AX.25 frame in raw format.
*
*
* Platform differences:
*
* For the Linux case,
* We supply a pseudo terminal for use by other applications.
*
* Version 1.5: Split serial port version off into its own file.
*
*---------------------------------------------------------------*/
#if __WIN32__ // Stub for Windows.
#include "direwolf.h"
#include "kiss.h"
void kisspt_init (struct misc_config_s *mc)
{
return;
}
void kisspt_set_debug (int n)
{
return;
}
void kisspt_send_rec_packet (int chan, int kiss_cmd, unsigned char *fbuf, int flen, int client)
{
return;
}
#else // Rest of file is for Linux only.
#include "direwolf.h"
#include <stdio.h>
#include <unistd.h>
#include <stdlib.h>
#include <string.h>
#include <ctype.h>
#include <fcntl.h>
#include <termios.h>
#include <sys/select.h>
#include <sys/types.h>
#include <sys/ioctl.h>
#include <errno.h>
#include "tq.h"
#include "ax25_pad.h"
#include "textcolor.h"
#include "kiss.h"
#include "kiss_frame.h"
#include "xmit.h"
/*
* Accumulated KISS frame and state of decoder.
*/
static kiss_frame_t kf;
/*
* These are for a Linux pseudo terminal.
*/
static int pt_master_fd = -1; /* File descriptor for my end. */
static char pt_slave_name[32]; /* Pseudo terminal slave name */
/* like /dev/pts/999 */
/*
* Symlink to pseudo terminal name which changes.
*/
#define TMP_KISSTNC_SYMLINK "/tmp/kisstnc"
static void * kisspt_listen_thread (void *arg);
static int kisspt_debug = 0; /* Print information flowing from and to client. */
void kisspt_set_debug (int n)
{
kisspt_debug = n;
}
/* In server.c. Should probably move to some misc. function file. */
void hex_dump (unsigned char *p, int len);
/*-------------------------------------------------------------------
*
* Name: kisspt_init
*
* Purpose: Set up a pseudo terminal acting as a virtual KISS TNC.
*
*
* Inputs:
*
* Outputs:
*
* Description: (1) Create a pseudo terminal for the client to use.
* (2) Start a new thread to listen for commands from client app
* so the main application doesn't block while we wait.
*
*
*--------------------------------------------------------------------*/
static int kisspt_open_pt (void);
void kisspt_init (struct misc_config_s *mc)
{
pthread_t kiss_pterm_listen_tid;
int e;
memset (&kf, 0, sizeof(kf));
/*
* This reads messages from client.
*/
pt_master_fd = -1;
if (mc->enable_kiss_pt) {
pt_master_fd = kisspt_open_pt ();
if (pt_master_fd != -1) {
e = pthread_create (&kiss_pterm_listen_tid, (pthread_attr_t*)NULL, kisspt_listen_thread, NULL);
if (e != 0) {
text_color_set(DW_COLOR_ERROR);
perror("Could not create kiss listening thread for Linux pseudo terminal");
}
}
}
else {
//text_color_set(DW_COLOR_INFO);
//dw_printf ("Use -p command line option to enable KISS pseudo terminal.\n");
}
#if DEBUG
text_color_set (DW_COLOR_DEBUG);
dw_printf ("end of kisspt_init: pt_master_fd = %d\n", pt_master_fd);
#endif
}
/*
* Returns fd for master side of pseudo terminal or -1 for error.
*/
static int kisspt_open_pt (void)
{
int fd;
char *pts;
struct termios ts;
int e;
#if DEBUG
text_color_set(DW_COLOR_DEBUG);
dw_printf ("kisspt_open_pt ( )\n");
#endif
fd = posix_openpt(O_RDWR|O_NOCTTY);
if (fd == -1
|| grantpt (fd) == -1
|| unlockpt (fd) == -1
|| (pts = ptsname (fd)) == NULL) {
text_color_set(DW_COLOR_ERROR);
dw_printf ("ERROR - Could not create pseudo terminal for KISS TNC.\n");
return (-1);
}
strlcpy (pt_slave_name, pts, sizeof(pt_slave_name));
e = tcgetattr (fd, &ts);
if (e != 0) {
text_color_set(DW_COLOR_ERROR);
dw_printf ("Can't get pseudo terminal attributes, err=%d\n", e);
perror ("pt tcgetattr");
}
cfmakeraw (&ts);
ts.c_cc[VMIN] = 1; /* wait for at least one character */
ts.c_cc[VTIME] = 0; /* no fancy timing. */
e = tcsetattr (fd, TCSANOW, &ts);
if (e != 0) {
text_color_set(DW_COLOR_ERROR);
dw_printf ("Can't set pseudo terminal attributes, err=%d\n", e);
perror ("pt tcsetattr");
}
/*
* We had a problem here since the beginning.
* If no one was reading from the other end of the pseudo
* terminal, the buffer space would eventually fill up,
* the write here would block, and the receive decode
* thread would get stuck.
*
* March 2016 - A "select" was put before the read to
* solve a different problem. With that in place, we can
* now use non-blocking I/O and detect the buffer full
* condition here.
*/
// text_color_set(DW_COLOR_DEBUG);
// dw_printf("Debug: Try using non-blocking mode for pseudo terminal.\n");
int flags = fcntl(fd, F_GETFL, 0);
e = fcntl (fd, F_SETFL, flags | O_NONBLOCK);
if (e != 0) {
text_color_set(DW_COLOR_ERROR);
dw_printf ("Can't set pseudo terminal to nonblocking, fcntl returns %d, errno = %d\n", e, errno);
perror ("pt fcntl");
}
text_color_set(DW_COLOR_INFO);
dw_printf("Virtual KISS TNC is available on %s\n", pt_slave_name);
#if 1
// Sample code shows this. Why would we open it here?
// On Ubuntu, the slave side disappears after a few
// seconds if no one opens it. Same on Raspbian which
// is also based on Debian.
// Need to revisit this.
int pt_slave_fd;
pt_slave_fd = open(pt_slave_name, O_RDWR|O_NOCTTY);
if (pt_slave_fd < 0) {
text_color_set(DW_COLOR_ERROR);
dw_printf ("Can't open %s\n", pt_slave_name);
perror ("");
return -1;
}
#endif
/*
* The device name is not the same every time.
* This is inconvenient for the application because it might
* be necessary to change the device name in the configuration.
* Create a symlink, /tmp/kisstnc, so the application configuration
* does not need to change when the pseudo terminal name changes.
*/
unlink (TMP_KISSTNC_SYMLINK);
// TODO: Is this removed when application exits?
if (symlink (pt_slave_name, TMP_KISSTNC_SYMLINK) == 0) {
dw_printf ("Created symlink %s -> %s\n", TMP_KISSTNC_SYMLINK, pt_slave_name);
}
else {
text_color_set(DW_COLOR_ERROR);
dw_printf ("Failed to create symlink %s\n", TMP_KISSTNC_SYMLINK);
perror ("");
}
return (fd);
}
/*-------------------------------------------------------------------
*
* Name: kisspt_send_rec_packet
*
* Purpose: Send a received packet or text string to the client app.
*
* Inputs: chan - Channel number where packet was received.
* 0 = first, 1 = second if any.
*
* kiss_cmd - Usually KISS_CMD_DATA_FRAME but we can also have
* KISS_CMD_SET_HARDWARE when responding to a query.
*
* pp - Identifier for packet object.
*
* fbuf - Address of raw received frame buffer
* or a text string.
*
* flen - Length of raw received frame not including the FCS
* or -1 for a text string.
*
* client - Not used for pseudo terminal.
* Here so that 3 related functions all have
* the same parameter list.
*
* Description: Send message to client.
* We really don't care if anyone is listening or not.
* I don't even know if we can find out.
*
*--------------------------------------------------------------------*/
void kisspt_send_rec_packet (int chan, int kiss_cmd, unsigned char *fbuf, int flen, int client)
{
unsigned char kiss_buff[2 * AX25_MAX_PACKET_LEN + 2];
int kiss_len;
int err;
if (pt_master_fd == -1) {
return;
}
if (flen < 0) {
flen = strlen((char*)fbuf);
if (kisspt_debug) {
kiss_debug_print (TO_CLIENT, "Fake command prompt", fbuf, flen);
}
strlcpy ((char *)kiss_buff, (char *)fbuf, sizeof(kiss_buff));
kiss_len = strlen((char *)kiss_buff);
}
else {
unsigned char stemp[AX25_MAX_PACKET_LEN + 1];
if (flen > (int)(sizeof(stemp)) - 1) {
text_color_set(DW_COLOR_ERROR);
dw_printf ("\nPseudo Terminal KISS buffer too small. Truncated.\n\n");
flen = (int)(sizeof(stemp)) - 1;
}
stemp[0] = (chan << 4) | kiss_cmd;
memcpy (stemp+1, fbuf, flen);
if (kisspt_debug >= 2) {
/* AX.25 frame with the CRC removed. */
text_color_set(DW_COLOR_DEBUG);
dw_printf ("\n");
dw_printf ("Packet content before adding KISS framing and any escapes:\n");
hex_dump (fbuf, flen);
}
kiss_len = kiss_encapsulate (stemp, flen+1, kiss_buff);
/* This has KISS framing and escapes for sending to client app. */
if (kisspt_debug) {
kiss_debug_print (TO_CLIENT, NULL, kiss_buff, kiss_len);
}
}
err = write (pt_master_fd, kiss_buff, (size_t)kiss_len);
if (err == -1 && errno == EWOULDBLOCK) {
text_color_set (DW_COLOR_INFO);
dw_printf ("KISS SEND - Discarding message because no one is listening.\n");
dw_printf ("This happens when you use the -p option and don't read from the pseudo terminal.\n");
}
else if (err != kiss_len)
{
text_color_set(DW_COLOR_ERROR);
dw_printf ("\nError sending KISS message to client application on pseudo terminal. fd=%d, len=%d, write returned %d, errno = %d\n\n",
pt_master_fd, kiss_len, err, errno);
perror ("pt write");
}
} /* kisspt_send_rec_packet */
/*-------------------------------------------------------------------
*
* Name: kisspt_get
*
* Purpose: Read one byte from the KISS client app.
*
* Global In: pt_master_fd
*
* Returns: one byte (value 0 - 255) or terminate thread on error.
*
* Description: There is room for improvment here. Reading one byte
* at a time is inefficient. We could read a large block
* into a local buffer and return a byte from that most of the time.
* Is it worth the effort? I don't know. With GHz processors and
* the low data rate here it might not make a noticable difference.
*
*--------------------------------------------------------------------*/
static int kisspt_get (void)
{
unsigned char ch;
int n = 0;
fd_set fd_in, fd_ex;
int rc;
while ( n == 0 ) {
/*
* Since the beginning we've always had a couple annoying problems with
* the pseudo terminal KISS interface.
* When using "kissattach" we would sometimes get the error message:
*
* kissattach: Error setting line discipline: TIOCSETD: Device or resource busy
* Are you sure you have enabled MKISS support in the kernel
* or, if you made it a module, that the module is loaded?
*
* martinhpedersen came up with the interesting idea of putting in a "select"
* before the "read" and explained it like this:
*
* "Reading from master fd of the pty before the client has connected leads
* to trouble with kissattach. Use select to check if the slave has sent
* any data before trying to read from it."
*
* "This fix resolves the issue by not reading from the pty's master fd, until
* kissattach has opened and configured the slave. This is implemented using
* select() to wait for data before reading from the master fd."
*
* The submitted code looked like this:
*
* FD_ZERO(&fd_in);
* rc = select(pt_master_fd + 1, &fd_in, NULL, &fd_in, NULL);
*
* That doesn't look right to me for a couple reasons.
* First, I would expect to use FD_SET for the fd.
* Second, using the same bit mask for two arguments doesn't seem
* like a good idea because select modifies them.
* When I tried running it, we don't get the failure message
* anymore but the select never returns so we can't read data from
* the KISS client app.
*
* I think this is what we want.
*
* Tested on Raspian (ARM) and Ubuntu (x86_64).
* We don't get the error from kissattach anymore.
*/
FD_ZERO(&fd_in);
FD_SET(pt_master_fd, &fd_in);
FD_ZERO(&fd_ex);
FD_SET(pt_master_fd, &fd_ex);
rc = select(pt_master_fd + 1, &fd_in, NULL, &fd_ex, NULL);
#if 0
text_color_set(DW_COLOR_DEBUG);
dw_printf ("select returns %d, errno=%d, fd=%d, fd_in=%08x, fd_ex=%08x\n", rc, errno, pt_master_fd, *((int*)(&fd_in)), *((int*)(&fd_in)));
#endif
if (rc == 0)
{
continue; // When could we get a 0?
}
if (rc == -1
|| (n = read(pt_master_fd, &ch, (size_t)1)) != 1)
{
text_color_set(DW_COLOR_ERROR);
dw_printf ("\nError receiving KISS message from client application. Closing %s.\n\n", pt_slave_name);
perror ("");
close (pt_master_fd);
pt_master_fd = -1;
unlink (TMP_KISSTNC_SYMLINK);
pthread_exit (NULL);
}
}
#if DEBUGx
text_color_set(DW_COLOR_DEBUG);
dw_printf ("kisspt_get(%d) returns 0x%02x\n", fd, ch);
#endif
return (ch);
}
/*-------------------------------------------------------------------
*
* Name: kisspt_listen_thread
*
* Purpose: Read messages from serial port KISS client application.
*
* Global In:
*
* Description: Reads bytes from the KISS client app and
* sends them to kiss_rec_byte for processing.
*
*--------------------------------------------------------------------*/
static void * kisspt_listen_thread (void *arg)
{
unsigned char ch;
#if DEBUG
text_color_set(DW_COLOR_DEBUG);
dw_printf ("kisspt_listen_thread ( %d )\n", fd);
#endif
while (1) {
ch = kisspt_get();
kiss_rec_byte (&kf, ch, kisspt_debug, -1, kisspt_send_rec_packet);
}
return (void *) 0; /* Unreachable but avoids compiler warning. */
}
#endif // Linux version
/* end kiss.c */