Improved generation of SREJ frames for more efficient AX.25 v2.2 connected mode.

Author: wb2osz

CHANGES.md

@@ -4,6 +4,8 @@
 
 ### New Features:
 
+- Improved generation of SREJ frames for more efficient AX.25 v2.2 connected mode.
+
 - Add delay before exit so any error messages can be read before window disappears.
 
 - New SCHANNEL feature to map a channel number to an external serial port TNC.    See [APRS-LoRa-VHF-APRS-Bridge.pdf](https://raw.githubusercontent.com/wb2osz/direwolf-doc/main/APRS-LoRa-VHF-APRS-Bridge.pdf) for explanation and example.

src/ax25_link.c

@@ -26,8 +26,9 @@
 #define AX25_N2_RETRY_MAX 15
 
 
-#define AX25_T1V_FRACK_MIN 1		// Number of seconds to wait before retrying.
-#define AX25_T1V_FRACK_DEFAULT 3	// KPC-3+ has 4.  TM-D710A has 3.
+#define AX25_T1V_FRACK_MIN 2		// Number of seconds to wait before retrying.
+#define AX25_T1V_FRACK_DEFAULT 4	// KPC-3+ has 4.  TM-D710A has 3.
+					// Previous 3 seems too agressive in practice for 1200 bps.
 #define AX25_T1V_FRACK_MAX 15
 
 
@@ -37,13 +38,20 @@
 
 #define AX25_K_MAXFRAME_EXTENDED_MIN 1
 #define AX25_K_MAXFRAME_EXTENDED_DEFAULT 32
-#define AX25_K_MAXFRAME_EXTENDED_MAX 63		// In theory 127 but I'm restricting as explained in SREJ handling.
-
+#define AX25_K_MAXFRAME_EXTENDED_MAX 63		// It cannot be 127 because SREJ requires out‑of‑order acceptance,
+						// which forces the window to be <= modulus/2.
+						// With a window of 127, the sender could have 126 outstanding
+						// unacknowledged frames.  If the receiver issues an SREJ for
+						// frame N, but the sender has already wrapped and reused sequence
+						// numbers, the receiver cannot know:
+						//  - Is this SREJ referring to the old frame N?
+						//  - Or the new frame N after wrap-around?
+						// This ambiguity makes SREJ unsafe with a window anywhere near the modulus.
 
 
 // Call once at startup time.
 
-void ax25_link_init (struct misc_config_s *pconfig, int debug);
+void ax25_link_init (struct misc_config_s *pconfig, int debug, int stats);
 
 
 

src/ax25_link.h

@@ -2207,6 +2207,14 @@ ax25_frame_type_t ax25_frame_type (packet_t this_p, cmdres_t *cr, char *desc, in
 	  this_p->modulo = modulo_128;
 	}
 
+// Display "n(s)" & "n(r)" as upper case to indicate modulo 128.
+
+	char ns_str[8] = "n(s)";
+	char nr_str[8] = "n(r)";
+	if (this_p->modulo == modulo_128) {
+	  strlcpy (ns_str, "N(S)", sizeof(ns_str));
+	  strlcpy (nr_str, "N(R)", sizeof(nr_str));
+	}
 
 	if (this_p->modulo == modulo_128) {
 	  c2 = ax25_get_c2 (this_p);
@@ -2242,8 +2250,8 @@ ax25_frame_type_t ax25_frame_type (packet_t this_p, cmdres_t *cr, char *desc, in
 	    *nr = (c >> 5) & 7;
 	  }
 
-	  //snprintf (desc, DESC_SIZ, "I %s, n(s)=%d, n(r)=%d, %s=%d", cr_text, *ns, *nr, pf_text, *pf);
-	  snprintf (desc, DESC_SIZ, "I %s, n(s)=%d, n(r)=%d, %s=%d, pid=0x%02x", cr_text, *ns, *nr, pf_text, *pf, ax25_get_pid(this_p));
+	  snprintf (desc, DESC_SIZ, "I %s, %s=%d, %s=%d, %s=%d, pid=0x%02x",
+			cr_text, ns_str, *ns, nr_str, *nr, pf_text, *pf, ax25_get_pid(this_p));
 	  return (frame_type_I);
 	}
 	else if ((c & 2) == 0) {
@@ -2259,12 +2267,11 @@ ax25_frame_type_t ax25_frame_type (packet_t this_p, cmdres_t *cr, char *desc, in
 	    *nr = (c >> 5) & 7;
 	  }
 
- 
 	  switch ((c >> 2) & 3) {
-	    case 0: snprintf (desc, DESC_SIZ, "RR %s, n(r)=%d, %s=%d", cr_text, *nr, pf_text, *pf);   return (frame_type_S_RR);   break;
-	    case 1: snprintf (desc, DESC_SIZ, "RNR %s, n(r)=%d, %s=%d", cr_text, *nr, pf_text, *pf);  return (frame_type_S_RNR);  break;
-	    case 2: snprintf (desc, DESC_SIZ, "REJ %s, n(r)=%d, %s=%d", cr_text, *nr, pf_text, *pf);  return (frame_type_S_REJ);  break;
-	    case 3: snprintf (desc, DESC_SIZ, "SREJ %s, n(r)=%d, %s=%d", cr_text, *nr, pf_text, *pf); return (frame_type_S_SREJ); break;
+	    case 0: snprintf (desc, DESC_SIZ, "RR %s, %s=%d, %s=%d", cr_text, nr_str, *nr, pf_text, *pf);   return (frame_type_S_RR);   break;
+	    case 1: snprintf (desc, DESC_SIZ, "RNR %s, %s=%d, %s=%d", cr_text, nr_str, *nr, pf_text, *pf);  return (frame_type_S_RNR);  break;
+	    case 2: snprintf (desc, DESC_SIZ, "REJ %s, %s=%d, %s=%d", cr_text, nr_str, *nr, pf_text, *pf);  return (frame_type_S_REJ);  break;
+	    case 3: snprintf (desc, DESC_SIZ, "SREJ %s, %s=%d, %s=%d", cr_text, nr_str, *nr, pf_text, *pf); return (frame_type_S_SREJ); break;
 	 } 
 	}
 	else {

src/ax25_pad.c

@@ -4785,6 +4785,10 @@ void config_init (char *fname, struct audio_s *p_audio_config,
  * IGTXVIA  channel  [ path ]
  */
 
+// FIXME: Should allow multiple transmit channels.
+// Should probably have multiple IGTXVIA, rather than a list of channels,
+// because they might want different paths.
+
 	  else if (strcasecmp(t, "IGTXVIA") == 0) {
 	    int n;
 

src/config.c

@@ -215,7 +215,10 @@ int main (int argc, char *argv[])
 	char input_file[80];
 	char T_opt_timestamp[40];
 
-	int t_opt = 1;		/* Text color option. */				
+	int t_opt = 1;		/* Text color option. */
+	char o_opt[80] = "";	// Console capture received raw packets. 
+	char O_opt[80] = "";	// Console capture all output.
+
 	int a_opt = 0;		/* "-a n" interval, in seconds, for audio statistics report.  0 for none. */
 	int g_opt = 0;		/* G3RUH mode, ignoring default for speed. */				
 	int j_opt = 0;		/* 2400 bps PSK compatible with direwolf <= 1.5 */
@@ -236,6 +239,7 @@ int main (int argc, char *argv[])
 	int d_2_opt = 0;	/* "-d 2" option for IL2P.  Default minimal. Repeat for more detail. */
 	int d_c_opt = 0;	/* "-d c" option for connected mode data link state machine. */
 	int d_q_opt = 0;	/* "-d q" option for data link state machine queue. */
+	int d_s_opt = 0;	/* "-d s" print statistics when link ends. */
 
 	int aprstt_debug = 0;	/* "-d d" option for APRStt (think Dtmf) debug. */
 
@@ -295,11 +299,19 @@ int main (int argc, char *argv[])
 
 // FIXME: consider case of no space between t and number.
 
+// Prescan for options that are needed before ant text goes to console.
+
 	for (j=1; j<argc-1; j++) {
 	  if (strcmp(argv[j], "-t") == 0) {
 	    t_opt = atoi (argv[j+1]);
 	    //dw_printf ("DEBUG: text color option = %d.\n", t_opt);
 	  }
+	  if (strcmp(argv[j], "-o") == 0) {
+	    strlcpy (o_opt, argv[j+1], sizeof(o_opt));
+	  }
+	  if (strcmp(argv[j], "-O") == 0) {
+	    strlcpy (O_opt, argv[j+1], sizeof(O_opt));
+	  }
 	}
 
 	// TODO: control development/beta/release by version.h instead of changing here.
@@ -310,6 +322,10 @@ int main (int argc, char *argv[])
 	// https://www.dennisbabkin.com/blog/?t=how-to-tell-the-real-version-of-windows-your-app-is-running-on
 
 	text_color_init(t_opt);
+	dw_printf_capture_init (o_opt, O_opt);
+
+// Print application version.
+
 	text_color_set(DW_COLOR_INFO);
 	//dw_printf ("Dire Wolf version %d.%d (%s) BETA TEST 1\n", MAJOR_VERSION, MINOR_VERSION, __DATE__);
 	dw_printf ("Dire Wolf DEVELOPMENT version %d.%d %s (%s)\n", MAJOR_VERSION, MINOR_VERSION, "B", __DATE__);
@@ -453,7 +469,7 @@ int main (int argc, char *argv[])
 
 	  /* ':' following option character means arg is required. */
 
-          c = getopt_long(argc, argv, "hP:B:gjJD:U:c:px:r:b:n:d:q:t:ul:L:Sa:E:T:e:X:AI:i:",
+          c = getopt_long(argc, argv, "hP:B:gjJD:U:c:px:r:b:n:d:q:t:ul:L:Sa:E:T:e:X:AI:i:o:O:",
                         long_options, &option_index);
           if (c == -1)
             break;
@@ -666,6 +682,8 @@ int main (int argc, char *argv[])
 	      case 'h':  d_h_opt++; break;			// Hamlib verbose level.
 #endif
 	      case 'c':  d_c_opt++; break;			// Connected mode data link state machine
+								// Repeat for more detail.
+	      case 's':  d_s_opt++; break;			// Print statistics when link ends
 	      case 'x':  d_x_opt++; break;			// FX.25
 	      case '2':  d_2_opt++; break;			// IL2P
 	      case 'd':	 aprstt_debug++; break;			// APRStt (mnemonic Dtmf)
@@ -691,6 +709,8 @@ int main (int argc, char *argv[])
 	    break;
 
 	  case 't':				/* Was handled earlier. */
+	  case 'o':
+	  case 'O':
 	    break;
 
 
@@ -791,7 +811,6 @@ int main (int argc, char *argv[])
           }
 
 	  strlcpy (input_file, argv[optind], sizeof(input_file));
-
 	}
 
 /*
@@ -1148,7 +1167,7 @@ int main (int argc, char *argv[])
 	igate_init (&audio_config, &igate_config, &digi_config, d_i_opt);
 	cdigipeater_init (&audio_config, &cdigi_config);
 	pfilter_init (&igate_config, d_f_opt);
-	ax25_link_init (&misc_config, d_c_opt);
+	ax25_link_init (&misc_config, d_c_opt, d_s_opt);
 
 /*
  * Provide the AGW & KISS socket interfaces for use by a client application.
@@ -1355,7 +1374,7 @@ void app_process_rec_packet (int chan, int subchan, int slice, packet_t pp, alev
 	// TODO:  suppress this message if not using soundcard input.
 	// i.e. we have no control over the situation when using SDR.
 
-	if (alevel.rec > 110) {
+	if (!q_h_opt && alevel.rec > 110) {
 
 	  text_color_set(DW_COLOR_ERROR);
 	  dw_printf ("Audio input level is too high. This may cause distortion and reduced decode performance.\n");
@@ -1451,6 +1470,14 @@ void app_process_rec_packet (int chan, int subchan, int slice, packet_t pp, alev
 	    xid_parse (pinfo, info_len, &param, info2text, sizeof(info2text));
 	    dw_printf (" %s\n", info2text);
 	  }
+	  else if (ftype == frame_type_S_SREJ) {
+	    // Additional sequence numbers can be in the info part.
+	    // This does not handle the range case, which we don't generate.
+	    for (int j = 0; j < info_len; j++) {
+	      dw_printf (" +%d", (unsigned int)(pinfo[j]) >> 1);
+	    }
+	    dw_printf ("\n");
+	  }
 	  else {
 	    ax25_safe_print ((char *)pinfo, info_len, ( ! ax25_is_aprs(pp)) && ( ! d_u_opt) );
 	    dw_printf ("\n");
@@ -1742,7 +1769,8 @@ static void usage (void)
 	dw_printf ("Usage: direwolf [options] [ - | stdin | UDP:nnnn ]\n");
 	dw_printf ("Options:\n");
 	dw_printf ("    -c fname       Configuration file name.\n");
-	dw_printf ("    -l logdir      Directory name for log files.  Use . for current.\n");
+	dw_printf ("    -l logdir      Directory name for daily log files.  Use . for current.\n");
+	dw_printf ("    -L logname     Generate single log file with fixed name.\n");
 	dw_printf ("    -r n           Audio sample rate, per sec.\n");
 	dw_printf ("    -n n           Number of audio channels, 1 or 2.\n");
 	dw_printf ("    -b n           Bits per audio sample, 8 or 16.\n");
@@ -1780,6 +1808,7 @@ static void usage (void)
 	dw_printf ("       h             h = hamlib increase verbose level.\n");
 #endif
 	dw_printf ("       c             c = Connected mode data link state machine.\n");
+	dw_printf ("       s             s = Print statistics when link ends.\n");
 	dw_printf ("       x             x = FX.25 increase verbose level.\n");
 	dw_printf ("       2             2 = IL2P.\n");
 	dw_printf ("       d             d = APRStt (DTMF to APRS object translation).\n");

src/direwolf.c

@@ -2,7 +2,7 @@
 //
 //    This file is part of Dire Wolf, an amateur radio packet TNC.
 //
-//    Copyright (C) 2011, 2012, 2013, 2014, 2019  John Langner, WB2OSZ
+//    Copyright (C) 2011, 2012, 2013, 2014, 2019, 2025  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
@@ -186,17 +186,21 @@ static const char clear_eos[]	= "\e[0J";
  *	9 (more accurately any invalid value) = try all of them and exit.
  */
 
+// TODO:  Should we have an exit handler to restore initial condition?
+
 static int g_enable_color = 1;
+static FILE *o_fp = NULL;
+static FILE *O_fp = NULL;
+static int current_color = 0;
 
 
 void text_color_init (int enable_color)
 {
 
+	g_enable_color = enable_color;
 
 #if __WIN32__
 
-g_enable_color = enable_color;
-
 	if (g_enable_color != 0) {
 
 	  HANDLE h;
@@ -226,7 +230,7 @@ g_enable_color = enable_color;
 
 // Run a test if outside of acceptable range.
 
-	if (enable_color < 0 || enable_color > MAX_T) {
+	if (g_enable_color < 0 || g_enable_color > MAX_T) {
 	  int t;
 	  for (t = 0; t <= MAX_T; t++) {
 	    text_color_init (t);
@@ -245,8 +249,6 @@ g_enable_color = enable_color;
 	   exit (EXIT_SUCCESS);
 	}
 
-	g_enable_color = enable_color;
-
 	if (g_enable_color != 0) {
 	  int t = g_enable_color;
 
@@ -258,7 +260,36 @@ g_enable_color = enable_color;
 	  printf ("%s", t_black[t]);
 	}
 #endif
-}
+
+} //end text_color_init
+
+
+// Creat screen output capture files.
+// "-o" is for only raw received packets.
+// "-O" is for everything.
+
+void dw_printf_capture_init (char *o_opt, char *O_opt)
+{
+	if (strlen(o_opt) > 0) {
+	  o_fp = fopen (o_opt, "w");
+	  if (o_fp == NULL) {
+	    text_color_set (DW_COLOR_ERROR);
+	    dw_printf ("Failed to open -o %s for write.\n", o_opt);
+	    exit (EXIT_FAILURE);
+	  }
+	}
+printf ("DEBUG O_opt=%s, strlen=%d\n", O_opt, (int)strlen(O_opt));
+	if (strlen(O_opt) > 0) {
+	  O_fp = fopen (o_opt, "w+");
+	  if (O_fp == NULL) {
+	    text_color_set (DW_COLOR_ERROR);
+	    dw_printf ("Failed to open -O %s for write.\n", O_opt);
+	dw_printf ("errno=%d\n", errno);
+	    exit (EXIT_FAILURE);
+	  }
+	}
+
+}  // end dw_printf_capture_init
 
 
 #if __WIN32__
@@ -335,6 +366,7 @@ void text_color_set ( enum dw_color_e c )
 
 #else
 
+
 void text_color_set ( enum dw_color_e c )
 {
 
@@ -377,6 +409,8 @@ void text_color_set ( enum dw_color_e c )
 	    printf ("%s", t_dark_green[t]);
 	    break;
 	}
+
+	current_color = c;
 }
 
 #endif
@@ -416,7 +450,14 @@ int dw_printf (const char *fmt, ...)
 	len = vsnprintf (buffer, BSIZE, fmt, args);
 	va_end (args);
 
-// TODO: other possible destinations...
+// other possible destinations...
+
+	if (o_fp != NULL && current_color == DW_COLOR_REC) {
+	  fputs (buffer, o_fp);
+	}
+	if (O_fp != NULL) {
+	  fputs (buffer, O_fp);
+	}
 
 	fputs (buffer, stdout);
 	return (len);

src/textcolor.c

@@ -23,6 +23,7 @@ typedef enum dw_color_e dw_color_t;
 
 
 void text_color_init (int enable_color);
+void dw_printf_capture_init (char *o_opt, char *O_opt);
 void text_color_set (dw_color_t c);
 void text_color_term (void);