2.4.19 panic, netrom

2.4.19 panic, netrom

[Kjell Jarl]

Hi,
I now think I can repeat the netrom disconnect causing kernel panics.

Netrom over ax.25.

It seems that outstanding netrom frames when the disconnect arrives is 
dangerous:

- I issue a netrom connect to a distand node.
- When connected, I send sveral "b" commands.
- When (unsure of the number) one or two "b" has been sent, there comes 
a netrom disconnect from the remote station.
- In my vnc window, the last thing I saw was another b being sent to my 
neighboring node after the disconnect arrived.


Red Hat Linux release 7.1 (Seawolf)
Kernel 2.4.19 on an i586
uscc card 1200 bit


73
Kjell, sm7gvf

Re: 2.4.19 panic, netrom

[Lars E. Pettersson]

On Tuesday 29 April 2003 08:12, Kjell Jarl wrote:
...
> - I issue a netrom connect to a distand node.
> - When connected, I send sveral "b" commands.
> - When (unsure of the number) one or two "b" has been sent, there comes
> a netrom disconnect from the remote station.
> - In my vnc window, the last thing I saw was another b being sent to my
> neighboring node after the disconnect arrived.

My kernel panics (it get hung in the interrupt handler) seem to come when I 
have a netrom connection with outstanding frames (if I remember correctly) 
and we get a timeout from the ax25 connection. When the ax25 connection, 
initiated by the netrom connect, times out, we get the hang.

Anyone with kernel knowledge that gets any wiser by this?

73 de Lars, sm6rpz
-- 
Lars E. Pettersson, SM6RPZ
Gothenburg, SWEDEN
sm6rpz@home.se
http://www.gbg.bonet.se/cassegrain/

TNC Software emulator - talk with KISS interface

[Sriram Chadalavada]

Hello everyone,
  I am looking for software (KISS-based)TNC emulators
that can run on Redhat 7.3 configured with AX.25
support.
Currently, I have installed KISS interfaces on two
Linux boxes and made them talk. But our project
(KUTESAT) needs emulation of an AX.25 link between two
systems ie a KISS interface on host talking to a sw
TNC which in turn communicates with its counterpart on
the other machine.
               I looked up on the web and found tfkiss
rpm which works on Suse. Can this be used on Redhat
7.3 too (installation as rpm or from source)? If so,
is it possible to make it work with the KISS
interfaces described above (created by using
kissattach command)?
                                       Cheers,
                                       Sriram
                                    
                         

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Re: TNC Software emulator - talk with KISS interface

[Tomi Manninen]

On Fri, 2 May 2003, Sriram Chadalavada wrote:

>   I am looking for software (KISS-based)TNC emulators
> that can run on Redhat 7.3 configured with AX.25
> support.
> Currently, I have installed KISS interfaces on two
> Linux boxes and made them talk. But our project
> (KUTESAT) needs emulation of an AX.25 link between two
> systems ie a KISS interface on host talking to a sw
> TNC which in turn communicates with its counterpart on
> the other machine.

Hmm... What do you mean by an AX.25 link? What kind of signals do you need 
for the link?

The KISS "protocol" is simply a very simple encapsulation of AX.25 frames 
over serial lines. When using KISS mode, a TNC actually hands over all the 
AX.25 protocol handling to the host PC. The TNC is left only with HDLC 
processing (bit stuffing and framing), CRC checking and the actual 
modulation/demodulation.

I would say that two computers talking KISS to each other, actually have
an AX.25 link.

But maybe you need something else? Syncronous HDLC signals maybe?

>                I looked up on the web and found tfkiss
> rpm which works on Suse. Can this be used on Redhat
> 7.3 too (installation as rpm or from source)? If so,
> is it possible to make it work with the KISS
> interfaces described above (created by using
> kissattach command)?

I'm not very familiar with the TFKISS software but my understanding is
that it enables one to use a KISS TNC with terminal software that is
written for the so called WA8DED HostMode. So the serial port will still
be talking KISS. And you can not make TFKISS talk with the linux kernel.

I don't think this is what you want (?).

-- 
Tomi Manninen           Internet:  oh2bns@sral.fi
OH2BNS                  AX.25:     oh2bns@oh2rbi.fin.eu
KP20ME04                Amprnet:   oh2bns@oh2rbi.ampr.org

Re: 2.4.19 panic, netrom

[Bernard Pidoux F6BVP]

Lars E. Pettersson wrote:

>On Tuesday 29 April 2003 08:12, Kjell Jarl wrote:
>...
>  
>
>>- I issue a netrom connect to a distand node.
>>- When connected, I send sveral "b" commands.
>>- When (unsure of the number) one or two "b" has been sent, there comes
>>a netrom disconnect from the remote station.
>>- In my vnc window, the last thing I saw was another b being sent to my
>>neighboring node after the disconnect arrived.
>>    
>>
>
>My kernel panics (it get hung in the interrupt handler) seem to come when I 
>have a netrom connection with outstanding frames (if I remember correctly) 
>and we get a timeout from the ax25 connection. When the ax25 connection, 
>initiated by the netrom connect, times out, we get the hang.
>
>Anyone with kernel knowledge that gets any wiser by this?
>
>73 de Lars, sm6rpz
>  
>
I have already reported to the list my findings about  kernel 2.4.x panics.
For me there is no question about the origin of the problem : it is not 
specifically related with netrom but with ax25.

Here I am using serial mkiss interface and I think that the problem is 
related to the serial management part of the code with intensive use of 
clear interrupt (cli) instructions. In 2.4 kernels the interrupts are 
handled differently than in 2.2 kernels by a new procedure called 
softirq, that apparently is unable to recover from all the interrupts 
generated by ax25 code.

I have traced the oops five times following the recommandations in
Documentation/oops-tracing.txt ( see REPORTING-BUGS and README files  in 
/usr/src/linux/ )

All reports gave the same message :
<0> Kernel panic : Aiee, killing interrupt handler !
interrupt handler not sycing

To make it short (I have 5 complete listing of traces with the last 
subroutines addresses processed by the CPU ) the 29 sequence of routines 
given by trace before kernel panics are not always exactly the same but 
it always start at

sock_def_write_space (sock.c)

and the last 13 are always the same, beginning with do_sysctl_strategy 
in sysctl.c and finishing by ksoftirq in softirq.c.

I guess that the important point is the way the code sequence leading to 
a kernel panic is started and what routines are involved.

In my case, subroutine ax25_rcv, that make a lot of cli() instructions, 
and ax25_kiss_rcv, were often involved in the fatal sequence.

I am aware that a lot of code cleaning is being performed in 2.5.x 
kernels following the decision to remove cli() / sti() mechanism. This 
should prevent system hanging, but until now I was not able to run such 
an experimental kernel (no display at boot !).

I certainly would be interested in testing ax25 after these intensive 
modifications around interrupt mechanism.


73 de Bernard F6BVP