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

[Anil Madhavapeddy <anil@xxxxxxxxxx>]

On 12 Apr 2015, at 16:51, Magnus Therning <magnus@xxxxxxxxxxxx> wrote:
> 
> On Sat, Apr 11, 2015 at 11:33:40PM +0800, Anil Madhavapeddy wrote:
>> On 11 Apr 2015, at 23:13, Magnus Skjegstad <magnus@xxxxx> wrote:
>>> 
> I backed to tcpip 2.3.0 (before the assert "fix") then
> 
> 1. `ncat` from dom0 works just fine, no assert and full string
>   received and returned.
> 2. `ncat` from my PC triggers the assert, the full string is received
>   and returned, but `ncat` hangs.

The perfect bisection, thank you!  This means that the Cstruct length
is shorter than the advertised packet length in the IP header for
some reason.  See:

https://github.com/mirage/mirage-tcpip/pull/122/files#diff-1b30afa1d7f89fe0693b36ef4006c6f4L178

Some more debugging around what the various values are would pin
down the problem.  You could put in some Printf.printfs around
the TCPIP code and see what comes out on the VM console.

> 
> Is there some pre-packaged ARM Linux guest image to download from
> somewhere?

There's a create-linux-guest script in /root of the Cubie/Xen
image.  That should debootstrap you up a guest quite conveniently.
However, it looks like you've pinpointed the problem source in the
TCPIP code (that only triggers on ARM).

-anil
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