antirez/dump1090 — pull request #63 by wiseman (2014-10-21 19:46:02+00:00)
Title: DF 18 / Control field 5 cluttering interactive display

(Sorry, I would open an issue but the repo doesn't have issues. Let me know if there's a better place to talk about this sort of thing.)

In Los Angeles I'm currently getting a lot of messages like this:
```
*95c60bf13b4db286b30fc180d20d;
CRC: 000000 (ok)
DF 18: Extended Squitter.
Control Field : 5 (TIS-B relay of ADS-B message with other address)
```
I also see a lot of what look like dozens of bogus entries in the interactive display:
```
C6021C S 50 3 21
C60979 S 53 10 18
C6067B S 49 22 2
C601EB S 49 18 5
C60A6C S 53 12 17
C60795 S 41 4 18
C601DA S 52 17 1
C60C20 S 46 10 19
C6092E S 47 24 1
C609B1 S 47 9 19
C60B19 S 44 28 1
C60FC6 S 49 13 17
C6078C S 51 11 18
C601B7 S 48 12 18
C60250 S 44 21 2
C60130 S 49 27 1
C60BF5 S 51 3 23
C60652 S 50 6 18
...
```

I don't know the details of DF 18, but the code that prints DF 18 doesn't seem to think there's an address in the message, due to the `mm->ca` guards here:

```
if ((mm->ca == 0) || (mm->ca == 1) || (mm->ca == 6)) {
if (mm->ca == 1) {
printf(" Other Address : %06x\n", mm->addr);
} else {
printf(" ICAO Address : %06x\n", mm->addr);
}
```

But maybe the interactive display (and web API) is somewhat blindly showing the entries with the address, which is invalid?