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wb2osz / direwolf

Dire Wolf is a software "soundcard" AX.25 packet modem/TNC and APRS encoder/decoder. It can be used stand-alone to observe APRS traffic, as a tracker, digipeater, APRStt gateway, or Internet Gateway (IGate). For more information, look at the bottom 1/4 of this page and in https://github.com/wb2osz/direwolf/blob/dev/doc/README.md
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Direwolf v1.6 - IGate->RF packets malformed? #425

Closed Tyler-2 closed 2 years ago

Tyler-2 commented 2 years ago

I noticed that when I send a message from my phone (APRSDroid) via APRS-IS, when my Direwolf digi picks it up and then tries to TX to RF, it seems to mangle the "header":

[ig>tx] K1MLN-7>APDR16,TCPIP*,qAC,T2MCI::K1MLN-1  :Test{4
[0L] K1MLN-2>APDW16,WIDE1-2:}K1MLN-7>APDR16,TCPIP,K1MLN-2*::K1MLN-1  :Test{4

I think this should look more like:

[ig>tx] K1MLN-7>APDR16,TCPIP*,qAC,T2MCI::K1MLN-1  :Test{4
[0L] K1MLN-7>APDR16,TCPIP,K1MLN-2*,WIDE1-2::K1MLN-1  :Test{4

Shouldn't it? While I'm not sure how IGate paths are supposed to be preserved/represented, it doesn't seem like the WIDE1-2:} that is inserted in the current case is correct, nor the changing of the packet to have "originated" from K1MLN-2.

The current case doesn't look like it would even be routable...

wb2osz commented 2 years ago

Thanks for writing.

"WIDE1-2" is highly unusual. Some digipeaters might discard it depending on the configuration. You probably want to change the IGate configuration to use "WIDE1-1,WIDE2-1". Otherwise it looks normal.

An IGate station wraps the original packet in a third party header. That way it has both the RF station transmitting this new packet and it retains the original sending station. When properly functioning APRS implementations see the "}" data type indicator, they process everything after it to obtain a modified version of the original packet.

You might find these references interesting:

APRS-IS (Automatic Packet Reporting System-Internet Service) http://www.aprs-is.net/Default.aspx

APRS iGate properties http://wiki.ham.fi/APRS_iGate_properties (now gone but you can find a copy here:) https://web.archive.org/web/20120503201832/http://wiki.ham.fi/APRS_iGate_properties

Notes to iGate developers https://github.com/hessu/aprsc/blob/master/doc/IGATE-HINTS.md#igates-dropping-duplicate-packets-unnecessarily

Tyler-2 commented 2 years ago

Thank you, looks like this format wasn't a mistake, it's just something I'm unfamiliar with. I'll read up on the docs. Two things I've already learned:

  1. Just because you're sending stuff to APRS-IS doesn't mean you can crank up the beacon rates.
  2. The main reason I even noticed this was that my nearby digi wasn't digipeating my igate->RF packets.... But it is probably because it had a filter configured to not do so. I'll correct that next time I have access to it.

Thanks for the careful and informative reply, it was probably more than I deserved!