Track what data we got via TIS-B, report it as such.

dump1090.h

@@ -165,6 +165,7 @@ typedef struct rtlsdr_dev rtlsdr_dev_t;
 #define MODES_ACFLAGS_FROM_MLAT      (1<<18) // Data was derived from multilateration
 #define MODES_ACFLAGS_ALTITUDE_HAE_VALID (1<<19) // altitude_hae is valid
 #define MODES_ACFLAGS_HAE_DELTA_VALID    (1<<20) // hae_delta is valid
+#define MODES_ACFLAGS_FROM_TISB      (1<<21) // Data was derived from TIS-B messages
 
 #define MODES_ACFLAGS_LLEITHER_VALID (MODES_ACFLAGS_LLEVEN_VALID | MODES_ACFLAGS_LLODD_VALID)
 #define MODES_ACFLAGS_LLBOTH_VALID   (MODES_ACFLAGS_LLEVEN_VALID | MODES_ACFLAGS_LLODD_VALID)

mode_s.c

@@ -714,6 +714,11 @@ static void decodeExtendedSquitter(struct modesMessage *mm)
 
     // Check CF on DF18 to work out the format of the ES and whether we need to look for an IMF bit
     if (mm->msgtype == 18) {
+        /* we just globally tag any DF18 as TIS-B,
+         * which is not strictly true but close enough
+         */
+        mm->bFlags |= MODES_ACFLAGS_FROM_TISB;
+
         switch (mm->cf) {
         case 0: //   ADS-B ES/NT devices that report the ICAO 24-bit address in the AA field
             break;

net_io.c

@@ -879,6 +879,31 @@ static const char *jsonEscapeString(const char *str) {
     return buf;
 }
 
+static char *append_flags(char *p, char *end, int flags)
+{
+    p += sprintf(p, end-p, "[");
+    if (flags & MODES_ACFLAGS_SQUAWK_VALID)
+        p += snprintf(p, end-p, "\"squawk\",");
+    if (flags & MODES_ACFLAGS_CALLSIGN_VALID)
+        p += snprintf(p, end-p, "\"callsign\",");
+    if (flags & MODES_ACFLAGS_LATLON_VALID)
+        p += snprintf(p, end-p, "\"lat\",\"lon\",");
+    if (flags & MODES_ACFLAGS_ALTITUDE_VALID)
+        p += snprintf(p, end-p, "\"altitude\",");
+    if (flags & MODES_ACFLAGS_HEADING_VALID)
+        p += snprintf(p, end-p, "\"track\",");
+    if (flags & MODES_ACFLAGS_SPEED_VALID)
+        p += snprintf(p, end-p, "\"speed\",");
+    if (flags & MODES_ACFLAGS_VERTRATE_VALID)
+        p += snprintf(p, end-p, "\"vert_rate\",");
+    if (flags & MODES_ACFLAGS_CATEGORY_VALID)
+        p += snprintf(p, end-p, "\"category\",");
+    if (p[-1] != '[')
+        --p;
+    p += snprintf(p, end-p, "]");
+    return p;
+}
+
 char *generateAircraftJson(const char *url_path, int *len) {
     uint64_t now = mstime();
     struct aircraft *a;
@@ -929,26 +954,12 @@ char *generateAircraftJson(const char *url_path, int *len) {
         if (a->bFlags & MODES_ACFLAGS_CATEGORY_VALID)
             p += snprintf(p, end-p, ",\"category\":\"%02X\"", a->category);
         if (a->mlatFlags) {
-            p += snprintf(p, end-p, ",\"mlat\":[");
+            p += snprintf(p, end-p, ",\"mlat\":");
-            if (a->mlatFlags & MODES_ACFLAGS_SQUAWK_VALID)
+            p = append_flags(p, end, a->mlatFlags);
-                p += snprintf(p, end-p, "\"squawk\",");
+        }
-            if (a->mlatFlags & MODES_ACFLAGS_CALLSIGN_VALID)
+        if (a->tisbFlags) {
-                p += snprintf(p, end-p, "\"callsign\",");
+            p += snprintf(p, end-p, ",\"tisb\":");
-            if (a->mlatFlags & MODES_ACFLAGS_LATLON_VALID)
+            p = append_flags(p, end, a->tisbFlags);
-                p += snprintf(p, end-p, "\"lat\",\"lon\",");
-            if (a->mlatFlags & MODES_ACFLAGS_ALTITUDE_VALID)
-                p += snprintf(p, end-p, "\"altitude\",");
-            if (a->mlatFlags & MODES_ACFLAGS_HEADING_VALID)
-                p += snprintf(p, end-p, "\"track\",");
-            if (a->mlatFlags & MODES_ACFLAGS_SPEED_VALID)
-                p += snprintf(p, end-p, "\"speed\",");
-            if (a->mlatFlags & MODES_ACFLAGS_VERTRATE_VALID)
-                p += snprintf(p, end-p, "\"vert_rate\",");
-            if (a->mlatFlags & MODES_ACFLAGS_CATEGORY_VALID)
-                p += snprintf(p, end-p, "\"category\",");
-            if (p[-1] != '[')
-                --p;
-            p += snprintf(p, end-p, "]");
         }
 
         p += snprintf(p, end-p, ",\"messages\":%ld,\"seen\":%.1f,\"rssi\":%.1f}",
@@ -1554,7 +1565,7 @@ static void modesReadFromClient(struct client *c) {
     }
 }
 
-#define TSV_MAX_PACKET_SIZE 160
+#define TSV_MAX_PACKET_SIZE 180
 
 static void writeFATSV()
 {
@@ -1599,6 +1610,7 @@ static void writeFATSV()
         char *p, *end;
 
         int flags;
+        int used_tisb = 0;
 
         // skip non-ICAO
         if (a->addr & MODES_NON_ICAO_ADDRESS)
@@ -1621,6 +1633,7 @@ static void writeFATSV()
             alt = a->altitude;
             altAge = now - a->seenAltitude;
             altValid = (altAge <= 30000);
+            used_tisb |= (a->tisbFlags & MODES_ACFLAGS_ALTITUDE_VALID);
         }
         
         if (flags & MODES_ACFLAGS_AOG_VALID) {
@@ -1633,21 +1646,26 @@ static void writeFATSV()
                 altAge = 0;
                 ground = 1;
             }
+
+            used_tisb |= (a->tisbFlags & MODES_ACFLAGS_AOG_VALID);
         }
 
         if (flags & MODES_ACFLAGS_LATLON_VALID) {
             latlonAge = now - a->seenLatLon;
             latlonValid = (latlonAge <= 30000);
+            used_tisb |= (a->tisbFlags & MODES_ACFLAGS_LATLON_VALID);
         }
 
         if (flags & MODES_ACFLAGS_HEADING_VALID) {
             trackAge = now - a->seenTrack;
             trackValid = (trackAge <= 30000);
+            used_tisb |= (a->tisbFlags & MODES_ACFLAGS_HEADING_VALID);
         }
 
         if (flags & MODES_ACFLAGS_SPEED_VALID) {
             speedAge = now - a->seenSpeed;
             speedValid = (speedAge <= 30000);
+            used_tisb |= (a->tisbFlags & MODES_ACFLAGS_SPEED_VALID);
         }
 
         // don't send mode S very often
@@ -1729,6 +1747,10 @@ static void writeFATSV()
             useful = 1;
         }
 
+        if (used_tisb) {
+            p += snprintf(p, bufsize(p,end), "\ttisb\t1");
+        }
+
         // if we didn't get at least an alt or a speed or a latlon or
         // a heading, bail out. We don't need to do anything special
         // to unwind prepareWrite().

track.c

@@ -597,6 +597,12 @@ struct aircraft *trackUpdateFromMessage(struct modesMessage *mm)
     else
         a->mlatFlags = (a->mlatFlags & a->bFlags) & ~mm->bFlags;
 
+    // Same for TIS-B
+    if (mm->bFlags & MODES_ACFLAGS_FROM_TISB)
+        a->tisbFlags = (a->tisbFlags & a->bFlags) | mm->bFlags;
+    else
+        a->tisbFlags = (a->tisbFlags & a->bFlags) & ~mm->bFlags;
+
     if (mm->msgtype == 32) {
         int flags = a->modeACflags;
         if ((flags & (MODEAC_MSG_MODEC_HIT | MODEAC_MSG_MODEC_OLD)) == MODEAC_MSG_MODEC_OLD) {

track.h

@@ -78,6 +78,7 @@ struct aircraft {
     uint64_t      seenTrack;      // Time (millis) at which track was measured
 
     int           mlatFlags;      // Data derived from mlat messages
+    int           tisbFlags;      // Data derived from TIS-B messages
 
     long          messages;       // Number of Mode S messages received
     int           modeA;          // Squawk