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Rate-limit the size of faup1090 (fatsv) updates #328

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Rate-limit the size of faup1090 (fatsv) updates #328

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34 changes: 31 additions & 3 deletions net_io.c
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Original file line number Diff line number Diff line change
Expand Up @@ -2648,6 +2648,7 @@ static void writeFATSV()
{
struct aircraft *a;
static uint64_t next_update;
static uint32_t resume_at; // if non-zero, last scan stopped at this aircraft

if (!Modes.fatsv_out.service || !Modes.fatsv_out.service->connections) {
return; // not enabled or no active connections
Expand All @@ -2661,7 +2662,25 @@ static void writeFATSV()
// scan once a second at most
next_update = now + 1000;

for (a = Modes.aircrafts; a; a = a->next) {
unsigned emitted = 0; // Bytes emitted so far this update
const unsigned BYTES_PER_UPDATE = 10000; // Generate up to about this many bytes per update

// Find our starting point
a = Modes.aircrafts;
if (resume_at) {
for (; a; a = a->next) {
if (a->addr == resume_at)
break;
}
if (!a) {
// Missed the resume point (e.g. aircraft entry expired)
// just run the whole list again
a = Modes.aircrafts;
}
}

// Scan until we've emitted enough, or reached the end of the list
for (; a && emitted < BYTES_PER_UPDATE; a = a->next) {
if (!a->reliable)
continue;

Expand Down Expand Up @@ -2755,6 +2774,7 @@ static void writeFATSV()
char *p = prepareWrite(&Modes.fatsv_out, TSV_MAX_PACKET_SIZE);
if (!p)
return;
char *start = p;
char *end = p + TSV_MAX_PACKET_SIZE;

p = appendFATSV(p, end, "_v", "%s", TSV_VERSION);
Expand Down Expand Up @@ -2845,10 +2865,12 @@ static void writeFATSV()
--p; // remove last tab
p = safe_snprintf(p, end, "\n");

if (p < end)
if (p < end) {
emitted += (p - start);
completeWrite(&Modes.fatsv_out, p);
else
} else {
fprintf(stderr, "fatsv: output too large (max %d, overran by %d)\n", TSV_MAX_PACKET_SIZE, (int) (p - end));
}

a->fatsv_emitted_altitude_baro = a->altitude_baro;
a->fatsv_emitted_altitude_geom = a->altitude_geom;
Expand Down Expand Up @@ -2886,6 +2908,12 @@ static void writeFATSV()
a->fatsv_last_force_emit = now;
}
}

// If we didn't completely scan the list, resume next time
// from the point where we stopped. We use the aircraft
// address to track this, to avoid worrying about the lifetime
// of the aircraft struct.
resume_at = a ? a->addr : 0;
}

//
Expand Down