HamBSD Development Log 2020-05-06

· hambsd journal aprs openbsd ax25

I worked on HamBSD today, still looking at improvements to aprsisd(8). My focus today was on gating from the Internet to RF.

In the morning I cleaned up the mess I made yesterday with escaping the non-printable characters in packets before uploading them. I ran some test packets through and both Xastir and aprs.fi could decode them so that must be the correct way to do it.

I also added filtering of generic station queries (?APRS?) and IGate queries (?IGATE?). When an IGate query is seen, aprsisd will now respond with a station capabilities packet. The packet is not very exciting as it only contains the “IGATE” capability right now, but at least it does that.

Third-party packets are also identified, and have their RF headers stripped, and then are unconditionally thrown away. I need to add a check there to see if TCPIP is in the path and gate it if it’s not but I didn’t get to that today.

I added a new flag to aprsisd, -b, to allow the operator to indicate whether or not this station is a bi-directional IGate station. This currently only affects the q construct added to the path for uploaded packets (there wasn’t one before today) to indicate to APRS-IS whether or not this station can be used for two-way messaging with RF stations in range. Later I’ll make this also drop incoming messages if it’s set to receive-only instead of attempting to gate them anyway.

I noticed that when I connect to aprsc servers with TLS, they have actually been appending a qAS (message generated by server) instead of qAR (message is from RF) which I think is a bug, so I filed a GitHub issue.

The big thing today was generating third-party headers. Until now, aprsisd has tried to stuff the TNC2 header back into an AX.25 packet with a lot of truncated path entries. It’s now building the headers correctly(ish) and it’s possible to have bi-directional messaging through a HamBSD IGate. The path in the encapsulated header is currently entirely missing but it still works.

As this is a completely different way of handling these packets, it meant a rewrite of a good chunk of code. The skeleton is there now, just need to fill it in.

APRS message from MM0ROR: Hello from APRS-IS!

Next steps:

  • Generate proper paths for 3rd-party packets
  • Include a path for RF headers for station capabilities and 3rd-party packets
  • Add the new -b flag to the man page

If you would like to contact me with comments, please send me an email.
If you would like to support my free software work, you can support me on Patreon or donate via PayPal.

This post was syndicated on: