Flag for system timestamp in Beast output

Allow the user to specify that the system timestamp should be used in
the Beast output timestamp bytes instead of the device-specific
timestamp.

dump1090.c

@@ -403,6 +403,7 @@ static void showHelp(void)
 "--net-buffer <n> TCP buffer size 64Kb * (2^n) (default: n=0, 64Kb)\n"
 "--net-verbatim Make output connections default to verbatim mode\n"
 " (forward all messages without correction)\n"
+"--beast-sys-time Encode the system timestamp in Beast output\n"
 "--forward-mlat Allow forwarding of received mlat results\n"
 "\n"
 // ------ 80 char limit ----------------------------------------------------------|
@@ -693,6 +694,8 @@ int main(int argc, char **argv) {
  Modes.net_sndbuf_size = atoi(argv[++j]);
  } else if (!strcmp(argv[j],"--net-verbatim")) {
  Modes.net_verbatim = 1;
+ } else if (!strcmp(argv[j],"--beast-sys-time")) {
+ Modes.beast_sys_timestamp = 1;
  } else if (!strcmp(argv[j],"--forward-mlat")) {
  Modes.forward_mlat = 1;
  } else if (!strcmp(argv[j],"--onlyaddr")) {

dump1090.h

@@ -365,6 +365,7 @@ struct _Modes { // Internal state
  char *net_bind_address; // Bind address
  int net_sndbuf_size; // TCP output buffer size (64Kb * 2^n)
  int net_verbatim; // if true, Beast output connections default to verbatim mode
+ int beast_sys_timestamp; // if true, use the system timestamp for Beast output
  int forward_mlat; // allow forwarding of mlat messages to output ports
  int quiet; // Suppress stdout
  uint32_t show_only; // Only show messages from this ICAO

net_io.c

@@ -399,13 +399,16 @@ static void completeWrite(struct net_writer *writer, void *endptr) {
 //
 // Write raw output in Beast Binary format with Timestamp to TCP clients
 //
+
+#define BEAST_TIMESTAMP Modes.beast_sys_timestamp ? mm->sysTimestampMsg : mm->timestampMsg
+
 static void modesSendBeastVerbatimOutput(struct modesMessage *mm, struct aircraft __attribute__((unused)) *a) {
  // Don't forward mlat messages, unless --forward-mlat is set
  if (mm->source == SOURCE_MLAT && !Modes.forward_mlat)
  return;
 
  // Do verbatim output for all messages
- writeBeastMessage(&Modes.beast_verbatim_out, mm->timestampMsg, mm->signalLevel, mm->verbatim, mm->msgbits / 8);
+ writeBeastMessage(&Modes.beast_verbatim_out, BEAST_TIMESTAMP, mm->signalLevel, mm->verbatim, mm->msgbits / 8);
 }
 
 static void modesSendBeastCookedOutput(struct modesMessage *mm, struct aircraft *a) {
@@ -422,9 +425,11 @@ static void modesSendBeastCookedOutput(struct modesMessage *mm, struct aircraft
  if ((a && !a->reliable) && !mm->reliable)
  return;
 
- writeBeastMessage(&Modes.beast_cooked_out, mm->timestampMsg, mm->signalLevel, mm->msg, mm->msgbits / 8);
+ writeBeastMessage(&Modes.beast_cooked_out, BEAST_TIMESTAMP, mm->signalLevel, mm->msg, mm->msgbits / 8);
 }
 
+#undef BEAST_TIMESTAMP
+
 static void writeBeastMessage(struct net_writer *writer, uint64_t timestamp, double signalLevel, unsigned char *msg, int msgLen) {
  char ch;
  int j;