On Sat, Feb 27, 2016 at 04:05:14PM +0100, folkert wrote:
> > As far as I know, AX.25 MTU is only take care of on transmitting.
> > There are no trunked buffer sizes on the rx-routines in the kernel.
> > => larger packets, even beyond the ax25 protocol spec (>256 bytes)
> > could be handled.
> >
> > On transmission, the MTU is respected.
> > But if you read my last posts on this list, that's not always true (IP):
> > I proposed a fix for packets leaving the interface that are much
> > larger than the configured MTU or / and the max-mtu of 256.
> > For normal PID=text packets, data sent with write() is adjusted to the
> > MTU, and data tried to send with syscall sendto() and a size > MTU are
> > rejected.
>
> check
> In which kernel is this implemented?
What of the things I described?
write(): afaik, since ever. segmentation happens (but not as PID=segment
as for IP - just a simple split of the data at the length)
sendto(): for ax25-I: sendto() with len > MTU fails.
for ax25-UI: see my proposal in
https://marc.info/?l=linux-hams&m=145554737504304&w=2 section 2.1
> > Btw, in your line:
> > > 23 11.084320000 FH4GOU-01 TRDS01-01 AX.25-NoL3 271 Text
> >
> > => 271 is beyond the standard. You'll might find many old software,
> > TNCs, etc. that would even not be capable to decode such a packet.
>
> Yes, that's how I found it out :-)
>
> > On the other hand I wonder what packet that was.
> > "NoL3" => I assume PID=text (not IP, ARP, etc.).
>
> It was a conversation between "axcall" and "ax25-node" (or "node"). In
> that packet was the result of "M ax0" (or "mheard ax0").
ax25-node was the sender?
I'd be glad if you could provide:
1. listen -a -h
AND
2. an strace of node ( strace -tt -s 2048 -xx -p PIDofNODE )
..at the point it gets the command it to send the result of "M ax0".
> > Sender is FH4GOU-1 (but that's not a call of one of the two sides in
> > your test setup). How does that callsign comes to the line and what
> > computer / os / pr-program / userspacesprogram sends this data?
>
> It should be correct, I checked it moments ago.
>
> Ok setup:
>
> - laptop with a tnc and a radio running linux kernel 4.2.1-2 from debian
> - raspberry pi with a tnc and a radio running kernel 4.1.18+ (raspbian)
>
> Both are connected to the TNCs via USB to serial converters. Both TNCs
> run the same software.
And I assume, raspberry pi is FH4GOU-0 running "node" with call FH4GOU-1 ?
And the program connecting with call is your laptop?
> The TNCs are arduinos and the radios are LoRa modules connected to them.
> https://www.vanheusden.com/radio/arduino-tnc.php
We talked about it on Jan, 30 ;)
vy 73,
- Thomas dl9sau
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