[Tinyos-devel] BaseStationP bug

[David Moss]

Hi Mike -

The location where the header is cleared is just after the source address,
length, and id of that packet are extracted into local variables.  These
local variables are then used in the next send() command and put back into
the packet by the communication driver itself.

-David




-----Original Message-----
From: Chieh-Jan (Mike) Liang [mailto:cliang4 at cs.jhu.edu] 
Sent: Monday, February 18, 2008 5:28 PM
To: David Moss
Cc: tinyos-devel at millennium.berkeley.edu
Subject: Re: [Tinyos-devel] BaseStationP bug

Hi David,

One question about your fix. Before the radio packet is injected to 
serial, you erase the header. If I am not mistaken, after you do this, you 
need to set the packet source address back. This is for the "transparent" 
bridging.

Thank you

Mike

On Fri, 15 Feb 2008, David Moss wrote:

> The BaseStation application moves received packets directly into the send
> branch of the serial or radio stacks without clearing the header.
Residual
> header information is left over from the opposite communication driver,
> which can cause send/receive problems elsewhere.
>
>
>
> The case I'm seeing here is a message is received through the serial
stack,
> causing the message's header to be filled in like a serial header.  The
> message is moved directly into the radio stack without clearing the
header.
> Some bytes of a radio packet header, like FCF, are not edited by the radio
> stack because they are assumed to contain pre-configured settings.  The
FCF
> byte is therefore corrupted by the bytes left over from the serial stack.
> This causes a node receiving the packet with the corrupted FCF byte to
> filter out and drop the packet.
>
>
>
> The solution is for the BaseStation application to clear each message_t's
> header before injecting the message into the send branch of the opposite
> communication driver.  I have attached my version of BaseStationP, but I
> would recommend the owner(s) of this application take a look before
> committing the fixes back to tinyos-2.x/apps/BaseStation.
>
>
>
> -David
>
>
>
>