Unable to map /tmp/kisstnc to any channel other than 0

[craigerl]

Maybe I overlooked it, but is it possible to map clients connecting to /tmp/kisstnc (pseudoterminal) to a specific channel in direwolf? Something besides the default channel 0?

We can do this on the tcp kiss port (map 8007/tcp to channel 7 for example):

KISSPORT   8007     7

but there is no equivalent method for the pseudoterminal. Any apps that use the psuedoterminal (kissattach/ax.25) are all put on channel 0.

I tried a few incantations of socat to represent the tcp port as a serial device, but all lead to tears.

I thought perhaps I could CDIGIPEAT one channel to the other, but no luck.

curiously,
-craig
KM6LYW

[dranch]

In Linux land, read the man page on "mkiss" and how the user needs to use different ptys to map to different KISS channels.
That said, Direwolf doesn't support multiple ptys today but maybe there is a way to to patch the SCHANNEL code to change the default KISS channel from a default of 0 to 7. Ideally, this should be configurable in the direwolf.conf file in the future

[wb2osz]

From what I've been able to find, AX.25 for Linux does not directly support dual port TNCs such as KPC-9612.
ax25ipd was used to make a dual port TNC look like two separate TNCs each with only port/channel 0.
I haven't looked at the PTY code for about 10 years. Need to refresh my memory before commenting further.

73,
John WB2OSZ

[craigerl]

Thanks guys, I tried mkiss, which gets close (direwolf must be run as root),

sudo mkiss -x 8 /tmp/kisstnc
Awaiting client connects on:
/dev/pts/7 /dev/pts/8 /dev/pts/9 /dev/pts/10 /dev/pts/11 /dev/pts/12 /dev/pts/13 /dev/pts/14 /dev/pts/15

sudo kissattach /dev/pts/15 radio
AX.25 port radio bound to device ax0

axcall COOL
... direwolf log...
[7>st] KM6LYW-10>COOL:(*
[7>st] KM6LYW-10>COOL:<0x92><0x87>
[7>st] KM6LYW>COOL:

[craigerl]

... and just to add context, this will allow us to setup AX.25 over bluetooth to KenwoodTHD74, Vero models, etc. No wires required, making data modes highly accessible to new operators. I'd really like to see an SCHANNEL equivalent. Is PCHANNEL taken? P(seudotty)CHANNEL?

thanks again,
-craig
KM6LYW

[wb2osz]

Pseudo terminals have caused me a lot of aggravation; I wish people would use TCP.
Probably not possible for your scenario.

The current pty KISS implementation has been stable for almost a decade.
It should not be difficult to generalize it for multiple ptys.
Just off the top of my head, configuration might look like:

PTYKISS (or KISSPTY?) -- same as command line option -p -- only one allowed -- all channels -- symlink /tmp/kisstnc

PTYKISS n -- up to some small number of pty interfaces allowed.
Frames received from channel n would go to client with 4 bit kiss channel field set to 0.
For KISS frames from client, the channel would be ignored, and it would be transmitted to channel n.
symlink /tmp/kisstnc{n}

e.g. PTYKISS 7 --> symlink /tmp/kisstnc7

This is not a promise to do it. Just thinking about what it might look like.

73,
John WB2OSZ

[craigerl]

YES! that! brilliant, as usual.

mkiss should essentially be doing that, but I'm not sure why the data is corrupted. I got the same result using socat to map the TCP/KISS port to a virtual serial port. If we figure out mkiss perhaps we could save you some time?

[dranch]

The mkiss tool comes from the ax25tools suite which hasn't seen enhancements in many years. Bernard and Lee keep the ax25apps/libs/tools compiling as Linux marches forward in the VE7FET repo but they don't do much else. I haven't seen Thomas do an updates on the dormant "official ax.25 repo" in years. Anyway, Bernard / Lee might consider accepting a merge request to add the missing functionality but someone else will probably need to code it.

[wb2osz]

Maybe we should be putting effort into eliminating the need to use AX.25 for Linux.
https://www.ardc.net/apply/grants/2021-grants/grant-fixing-the-linux-kernel-ax-25/
I believe that PAT already supports the AGW interface.

73,
John WB2OSZ

[dranch]

Funny.. that initial proposal idea was from me and the grant was accepted by Thomas DL9SAU years ago. After some time of zero progress, the funds were returned as Thomas could not take on the project at that time. If we could find a new kernel developer to take on the effort, that would be fantastic. That said, I don't see that happening any time soon.

[craigerl]

That was $180K? I wish I had the cognitive capacity for that.

Is there a way to temporarily brute force traffic on /tmp/kisstnc to use channel 7 in the short term? Doing the socat tricks, and using mkiss both fail the same way when attempting an ax.25 connection. It hits channel 7, which is great, but there's four bytes of garbage in the payloads, then nothing,

sudo rfcomm bind /dev/rfcomm7 24:71:89:95:56:71 2 #bluetooth

SCHANNEL 7 /dev/frcom7 115200
KISSPORT 8001 7

socat pty,link=/tmp/kiss8001,echo=0 tcp:localhost:8001. #turn tcp/8001 into a serial port
kissattach /tmp/kiss8001 radio #bring up ax0

$ axcall COOL

(direwolf.log)
[7>st] KM6LYW-10>COOL:(*
[7>st] KM6LYW-10>COOL:<0x92><0x87>
[7>st] KM6LYW-10>COOL:
[7>st] KM6LYW-10>COOL:
[7>st] KM6LYW-10>COOL:

I grepped "channel" in the direwolf src directory ... and I noped' out. :)

thanks,
-craig
KM6LYW

[wb2osz]

Making progress.

[wb2osz]

The desired functionality is in the dev branch.
Keep this open because it needs more testing, cleanup, and documentation.

73,
John WB2OSZ