Re: [MirageOS-devel] More troubles with tcp on ARM

[Magnus Therning <magnus@xxxxxxxxxxxx>]

On Thu, Apr 09, 2015 at 10:18:53PM +0200, Magnus Therning wrote:
[...]

> 
> It works fine in Unix mode, both on x86 and on my cubietruck board.
> When built in Xen mode though it doesn't work as well.
> 
> When run in Unix mode I see the expected behaviour:
> 
>   shell                                         my server console
>   -----                                         -----------------
>   % echo hello | ncat -4 -u localhost 18081 ->  udp: 127.0.0.1:46507
>                                                  udp: 6 - hello
> 
>   % echo hello | ncat -4 localhost 18080    ->  tcp: 127.0.0.1:59888
>   hello                                          6 - hello
> 
>   % echo foobar | ncat -4 localhost 18080   ->  tcp: 127.0.0.1:59888
>   foobar                                         6 - foobar

That last line should of course read

  foobar                                         7 - foobar

That was caused by a copy-paste mistake of mine.

> When running the server in a VM on ARM I see the same behaviour for
> UDP, but for TCP it changes.
> 
>   shell                                         my server console
>   -----                                         -----------------
>   % echo hello | ncat -4 -u localhost 18081 ->  udp: 127.0.0.1:46507
>                                                  udp: 6 - hello
> 
>   % echo hello | ncat -4 localhost 18080    ->  tcp: 127.0.0.1:59888
>                                                  6 -
>                                                  6 -

And here there are even more copy-paste mistakes.  I must have been
tired yesterday.  Just disregard the `localhost` and `127.0.0.1`, that
should of course be the IPs of my cubietruck and my PC, respectively.

I did a little bit more testing of this just now, and found something
surprising.  This is against a VM on ARM:

~~~
% echo thisisalongerstring | ncat -4 192.168.0.33 18080
alongerstring

->

tcp: 192.168.0.11:48731
 6 - 
 14 - alongerstring
~~~

and

~~~
% echo thisisalongerstringandthisislongerstill | ncat -4 192.168.0.33 18080
alongerstringandthisislongerstill

->

tcp: 192.168.0.11:48732
 6 - 
 34 - alongerstringandthisislongerstill
~~~

and if I send a string that is shorter than 6 characters (I'm guessing
including the trailing \r\n), then `ncat` hangs and on the ARM I only
see a single line of "length - content":

~~~
tcp: 192.168.0.11:48766
 6 -
~~~

I do wonder where those initial 6 characters go...

/M

-- 
Magnus Therning                      OpenPGP: 0xAB4DFBA4 
email: magnus@xxxxxxxxxxxx   jabber: magnus@xxxxxxxxxxxx
twitter: magthe               http://therning.org/magnus

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