Add IL2P.

Author: wb2osz

CHANGES.md

@@ -7,6 +7,8 @@
 
 ### New Features: ###
 
+- Improved Layer 2 Protocol [(IL2P)](https://en.wikipedia.org/wiki/FX.25_Forward_Error_Correction).  Use "-I 1" to enable transmit for first channel.
+
 - Limited support for CM109/CM119 GPIO PTT on Windows.
 
 - Dire Wolf now advertises itself using DNS Service Discovery.  This allows suitable APRS / Packet Radio applications to find a network KISS TNC without knowing the IP address or TCP port.    Thanks to Hessu for providing this.  Currently available only for Linux and Mac OSX.  [Read all about it here.](https://github.com/hessu/aprs-specs/blob/master/TCP-KISS-DNS-SD.md)

README.md

@@ -13,7 +13,11 @@ Dire Wolf now includes [FX.25](https://en.wikipedia.org/wiki/FX.25_Forward_Error
 
 ![](fx25.png)
 
-Dire Wolf is a modern software replacement for the old 1980's style TNC built with special hardware.
+Version 1.7 adds [IL2P](https://en.wikipedia.org/wiki/Improved_Layer_2_Protocol), a different method of FEC with less overhead.
+
+
+
+### Dire Wolf is a modern software replacement for the old 1980's style TNC built with special hardware. ###
 
 Without any additional software, it can perform as:
 

man/direwolf.1

@@ -87,7 +87,15 @@ Divide audio sample by n for first channel.
 
 .TP
 .BI "-X " "n"
-1 to enable FX.25 transmit.
+1 to enable FX.25 transmit.  16, 32, 64 for specific number of check bytes.
+
+.TP
+.BI "-I " "n"
+Enable IL2P transmit.  n=1 is recommended.  0 uses weaker FEC.
+
+.TP
+.BI "-i " "n"
+Enable IL2P transmit, inverted polarity.  n=1 is recommended.  0 uses weaker FEC.
 
 .TP
 .BI "-d " "x"

man/gen_packets.1

@@ -62,6 +62,18 @@ Force G3RUH modem regardless of data rate.
 .BI "-J " 
 2400 bps QPSK compatible with MFJ-2400.
 
+.TP
+.BI "-X " "n"
+1 to enable FX.25 transmit.  16, 32, 64 for specific number of check bytes.
+
+.TP
+.BI "-I " "n"
+Enable IL2P transmit.  n=1 is recommended.  0 uses weaker FEC.
+
+.TP
+.BI "-i " "n"
+Enable IL2P transmit, inverted polarity.  n=1 is recommended.  0 uses weaker FEC.
+
 
 .TP
 .BI  "-m " "n"

src/CMakeLists.txt

@@ -60,6 +60,13 @@ list(APPEND direwolf_SOURCES
   hdlc_rec2.c
   hdlc_send.c
   igate.c
+  il2p_codec.c
+  il2p_scramble.c
+  il2p_rec.c
+  il2p_payload.c
+  il2p_init.c
+  il2p_header.c
+  il2p_send.c
   kiss_frame.c
   kiss.c
   kissserial.c
@@ -289,12 +296,20 @@ target_link_libraries(log2gpx
 list(APPEND gen_packets_SOURCES
   gen_packets.c
   ax25_pad.c
+  ax25_pad2.c
   fx25_encode.c
+  fx25_extract.c
   fx25_init.c
   fx25_send.c
   hdlc_send.c
   fcs_calc.c
   gen_tone.c
+  il2p_codec.c
+  il2p_scramble.c
+  il2p_payload.c
+  il2p_init.c
+  il2p_header.c
+  il2p_send.c
   morse.c
   dtmf.c
   textcolor.c
@@ -321,14 +336,22 @@ list(APPEND atest_SOURCES
   demod_9600.c
   dsp.c
   fx25_extract.c
+  fx25_encode.c
   fx25_init.c
   fx25_rec.c
   hdlc_rec.c
   hdlc_rec2.c
+  il2p_codec.c
+  il2p_scramble.c
+  il2p_rec.c
+  il2p_payload.c
+  il2p_init.c
+  il2p_header.c
   multi_modem.c
   rrbb.c
   fcs_calc.c
   ax25_pad.c
+  ax25_pad2.c
   decode_aprs.c
   dwgpsnmea.c
   dwgps.c
@@ -421,6 +444,29 @@ if(WIN32 OR CYGWIN)
 endif()
 
 
+# TNC interoperability testing for AX.25 connected mode.
+# tnctest
+list(APPEND tnctest_SOURCES
+  tnctest.c
+  textcolor.c
+  dtime_now.c
+  serial_port.c
+  )
+
+add_executable(tnctest
+  ${tnctest_SOURCES}
+  )
+
+target_link_libraries(tnctest
+  ${MISC_LIBRARIES}
+  Threads::Threads
+  )
+
+if(WIN32 OR CYGWIN)
+  target_link_libraries(tnctest ws2_32)
+endif()
+
+
 # List USB audio adapters than can use GPIO for PTT.
 # Originally for Linux only (using udev).
 # Version 1.7 adds it for Windows.  Needs hidapi library.
@@ -520,6 +566,7 @@ install(TARGETS gen_packets DESTINATION ${INSTALL_BIN_DIR})
 install(TARGETS atest DESTINATION ${INSTALL_BIN_DIR})
 install(TARGETS ttcalc DESTINATION ${INSTALL_BIN_DIR})
 install(TARGETS kissutil DESTINATION ${INSTALL_BIN_DIR})
+install(TARGETS tnctest DESTINATION ${INSTALL_BIN_DIR})
 install(TARGETS appserver DESTINATION ${INSTALL_BIN_DIR})
 if(UDEV_FOUND OR WIN32 OR CYGWIN)
   install(TARGETS cm108 DESTINATION ${INSTALL_BIN_DIR})

src/atest.c

@@ -2,7 +2,7 @@
 //
 //    This file is part of Dire Wolf, an amateur radio packet TNC.
 //
-//    Copyright (C) 2011, 2012, 2013, 2014, 2015, 2016, 2019  John Langner, WB2OSZ
+//    Copyright (C) 2011, 2012, 2013, 2014, 2015, 2016, 2019, 2021  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
@@ -82,6 +82,7 @@
 #include "ptt.h"
 #include "dtime_now.h"
 #include "fx25.h"
+#include "il2p.h"
 #include "hdlc_rec.h"
 
 
@@ -189,6 +190,7 @@ static int h_opt = 0;			// Hexadecimal display of received packet.
 static char P_opt[16] = "";		// Demodulator profiles.
 static int d_x_opt = 1;			// FX.25 debug.
 static int d_o_opt = 0;			// "-d o" option for DCD output control. */	
+static int d_2_opt = 0;			// "-d 2" option for IL2P details. */
 static int dcd_count = 0;
 static int dcd_missing_errors = 0;
 
@@ -389,6 +391,7 @@ int main (int argc, char *argv[])
 	        switch (*p) {
 	           case 'x':  d_x_opt++; break;			// FX.25
 	           case 'o':  d_o_opt++; break;			// DCD output control
+	           case '2':  d_2_opt++; break;			// IL2P debug out
 	           default: break;
 	        }
 	       }
@@ -539,6 +542,7 @@ int main (int argc, char *argv[])
 	}
 
 	fx25_init (d_x_opt);
+	il2p_init (d_2_opt);
 
 	start_time = dtime_now();
 

src/audio.h

@@ -107,10 +107,11 @@ struct audio_s {
 	float recv_ber;			/* Receive Bit Error Rate (BER). */
 					/* Probability of inverting a bit coming out of the modem. */
 
-	int fx25_xmit_enable;		/* Enable transmission of FX.25.  */
+	//int fx25_xmit_enable;		/* Enable transmission of FX.25.  */
 					/* See fx25_init.c for explanation of values. */
 					/* Initially this applies to all channels. */
 					/* This should probably be per channel. One step at a time. */
+					/* v1.7 - replaced by layer2_xmit==LAYER2_FX25 */
 
 	int fx25_auto_enable;		/* Turn on FX.25 for current connected mode session */
 					/* under poor conditions. */
@@ -156,6 +157,23 @@ struct audio_s {
 					/* Might try MFJ-2400 / CCITT v.26 / Bell 201 someday. */
 					/* No modem.  Might want this for DTMF only channel. */
 
+	    enum layer2_t { LAYER2_AX25 = 0, LAYER2_FX25, LAYER2_IL2P } layer2_xmit;
+
+					// IL2P - New for version 1.7.
+					// New layer 2 with FEC.  Much less overhead than FX.25 but no longer backward compatible.
+					// Only applies to transmit.
+					// Listening for FEC sync word should add negligible overhead so
+					// we leave reception enabled all the time as we do with FX.25.
+					// TODO:  FX.25 should probably be put here rather than global for all channels.
+
+	    int fx25_strength;		// Strength of FX.25 FEC.
+					// 16, 23, 64 for specific number of parity symbols.
+					// 1 for automatic selection based on frame size.
+
+	    int il2p_max_fec;		// 1 for max FEC length, 0 for automatic based on size.
+
+	    int il2p_invert_polarity;	// 1 means invert on transmit.  Receive handles either automatically.
+
 	    enum v26_e { V26_UNSPECIFIED=0, V26_A, V26_B } v26_alternative;
 
 					// Original implementation used alternative A for 2400 bbps PSK.

src/ax25_pad.c

@@ -2751,6 +2751,7 @@ unsigned short ax25_m_m_crc (packet_t pp)
 	unsigned char fbuf[AX25_MAX_PACKET_LEN];
 	int flen;
 
+	// TODO: I think this can be more efficient by getting the packet content pointer instead of copying.
 	flen = ax25_pack (pp, fbuf); 
 
 	crc = 0xffff;
@@ -2803,7 +2804,8 @@ unsigned short ax25_m_m_crc (packet_t pp)
  *			
  *------------------------------------------------------------------*/
 
-#define MAXSAFE 500
+//#define MAXSAFE 500
+#define MAXSAFE AX25_MAX_INFO_LEN
 
 void ax25_safe_print (char *pstr, int len, int ascii_only)
 {

src/config.c

@@ -585,7 +585,7 @@ static int check_via_path (char *via_path)
  *
  *--------------------------------------------------------------------*/
 
-#define MAXCMDLEN 256
+#define MAXCMDLEN 1200
 
 
 static char *split (char *string, int rest_of_line)
@@ -770,6 +770,10 @@ void config_init (char *fname, struct audio_s *p_audio_config,
 	  p_audio_config->achan[channel].num_freq = 1;				
 	  p_audio_config->achan[channel].offset = 0;
 
+	  p_audio_config->achan[channel].layer2_xmit = LAYER2_AX25;
+	  p_audio_config->achan[channel].il2p_max_fec = 1;
+	  p_audio_config->achan[channel].il2p_invert_polarity = 0;
+
 	  p_audio_config->achan[channel].fix_bits = DEFAULT_FIX_BITS;
 	  p_audio_config->achan[channel].sanity_test = SANITY_APRS;
 	  p_audio_config->achan[channel].passall = 0;
@@ -2252,7 +2256,7 @@ void config_init (char *fname, struct audio_s *p_audio_config,
  *				0 = off, 1 = auto mode, others are suggestions for testing
  *				or special cases.  16, 32, 64 is number of parity bytes to add.
  *				Also set by "-X n" command line option.
- *				Current a global setting.  Could be per channel someday.
+ *				V1.7 changed from global to per-channel setting.
  */
 
 	  else if (strcasecmp(t, "FX25TX") == 0) {
@@ -2265,13 +2269,15 @@ void config_init (char *fname, struct audio_s *p_audio_config,
 	    }
 	    n = atoi(t);
             if (n >= 0 && n < 200) {
-	      p_audio_config->fx25_xmit_enable = n;
+	      p_audio_config->achan[channel].fx25_strength = n;
+	      p_audio_config->achan[channel].layer2_xmit = LAYER2_FX25;
 	    }
 	    else {
-	      p_audio_config->fx25_xmit_enable = 1;
+	      p_audio_config->achan[channel].fx25_strength = 1;
+	      p_audio_config->achan[channel].layer2_xmit = LAYER2_FX25;
 	      text_color_set(DW_COLOR_ERROR);
               dw_printf ("Line %d: Unreasonable value for FX.25 transmission mode. Using %d.\n", 
-			line, p_audio_config->fx25_xmit_enable);
+			line, p_audio_config->achan[channel].fx25_strength);
    	    }
 	  }
 
@@ -2304,6 +2310,48 @@ void config_init (char *fname, struct audio_s *p_audio_config,
    	    }
 	  }
 
+/*
+ * IL2PTX  [ + - ] [ 0 1 ]	- Enable IL2P transmission.  Default off.
+ *				"+" means normal polarity. Redundant since it is the default.
+ *					(command line -I for first channel)
+ *				"-" means inverted polarity. Do not use for 1200 bps.
+ *					(command line -i for first channel)
+ *				"0" means weak FEC.  Not recommended.
+ *				"1" means stronger FEC.  "Max FEC."  Default if not specified.
+ */
+
+	  else if (strcasecmp(t, "IL2PTX") == 0) {
+
+	    p_audio_config->achan[channel].layer2_xmit = LAYER2_IL2P;
+	    p_audio_config->achan[channel].il2p_max_fec = 1;
+	    p_audio_config->achan[channel].il2p_invert_polarity = 0;
+
+	    while ((t = split(NULL,0)) != NULL) {
+	      for (char *c = t; *t != '\0'; c++) {
+	        switch (*c) {
+	          case '+':
+	            p_audio_config->achan[channel].il2p_invert_polarity = 0;
+	            break;
+	          case '-':
+	            p_audio_config->achan[channel].il2p_invert_polarity = 1;
+	            break;
+	          case '0':
+	            p_audio_config->achan[channel].il2p_max_fec = 0;
+	            break;
+	          case '1':
+	            p_audio_config->achan[channel].il2p_max_fec = 1;
+	            break;
+	          default:
+	            text_color_set(DW_COLOR_ERROR);
+	            dw_printf ("Line %d: Invalid parameter '%c' fol IL2PTX command.\n", line, *c);
+	            continue;
+	            break;
+	        }
+	      }
+	    }
+	  }
+
+
 /*
  * ==================== APRS Digipeater parameters ====================
  */
@@ -5399,7 +5447,7 @@ static int beacon_options(char *cmd, struct beacon_s *b, int line, struct audio_
 	while ((t = split(NULL,0)) != NULL) {
 
 	  char keyword[20];
-	  char value[200];
+	  char value[1000];
 	  char *e;
 	  char *p;