sender header callsign gets a * causes aprslib to fail to decode packet about aioax25 HOT 10 CLOSED

I found a workaround for the time being.

After getting the frame from aioax25, I force the control bit to False for the sender with

frame.header._source._ch = False

from aioax25.

For what it's worth, here is my patch on aprsd that uses aioax25. I have it working with tcpkiss and am testing it with serialkiss next.

aprsd <---> aioax25 <-- tcp kiss --> direwolf

from aioax25.

Okay, so that field marked CH in this code base can mean two different things:

• In a source or destination call-sign/SSID, it's the "command" bit
• In a repeater call-sign/SSID, it's the "has been repeated" bit

http://web.archive.org/web/20190522033714/https://www.tapr.org/pub_ax25.html#2.4.1.2

I set the bits according to what I understood from that part of the AX.25 2.0 specification. Clearly APRS is special. ;-)

from aioax25.

http://www.aprs.org/aprs11/C-bits-SSID.txt … took some digging, but this is where I got the idea that the destination call-sign should have a C bit set on the destination and cleared on the source.

Since bit also doubles as the has been digipeated bit when the field is used in a digipeater context, * gets appended anywhere the C/H bit is set.

In the bug report though, one can clearly see it's the source bit that's getting that C bit set… so ch=False is being passed in somewhere. Been a while since I looked at this code, so it might take some digging.

from aioax25.

@hemna I had a look at the code in aprslib and in aprsd… it would seem the problem is we really need a means of obtaining a frame in "TNC2 format" which could then be passed to aprslib.

Have a look at https://github.com/sjlongland/aioax25/tree/bugfix/issue-9-addr-ch-bit-set and in your code https://github.com/craigerl/aprsd/blob/master/aprsd/threads.py#L374-L375, you should be able to replace that with:

msg = frame.tnc2

from aioax25.

https://github.com/craigerl/aprsd/blob/master/aprsd/threads.py#L374-L375

awesome. I'll give that a try!

from aioax25.

This is what I got.

Traceback (most recent call last):
  File "/Users/i530566/.pyenv/versions/3.8.5/lib/python3.8/asyncio/events.py", line 81, in _run
    self._context.run(self._callback, *self._args)
  File "/Users/i530566/devel/mine/aprsd/aprsd/threads.py", line 376, in process_packet
    msg = frame.tnc2
AttributeError: 'APRSMessageFrame' object has no attribute 'tnc2'

from aioax25.

Strange… because APRSMessageFrame is a APRSFrame, which is a AX25UnnumberedInformationFrame…

AX25UnnumberedInformationFrame defines the tnc2 property and get_tnc2() method.

Are you sure you pulled the right branch (bugfix/issue-9-addr-ch-bit-set)? Did you symbolically link aioax25's module directory into your project or run setup.py install to install the module in your library path?

from aioax25.

ah! I didn't pull the bugfix/issue-9-addr-ch-bit-set. branch. I tried that out and it's working.
I just set my message to frame.tnc2 and it's good to get decoded!

from aioax25.

No worries, I figured I'd try this first before I tried mucking with changing the C bits actually sent over the air. :-)

Half the problem with AX.25 is a lot of the standards were written about the time I was born or a few years after, and so getting documentation on them today can be sketchy. Then you have "de-facto standards" like "TNC2 format", which are seemingly undocumented.

Anyway, if it's working now, I guess we can close this unless we strike issues later. Many thanks.

from aioax25.