Hi Harti,

Thanks for your pointers.

On 03/09/11 10:40, Harti Brandt wrote:
Hi Martin,

On Sat, 19 Feb 2011, Martin Birgmeier wrote:


MB>- whether and how it is even possible to inject raw ATM cells,

AF_NATM with AAL0.

MB>- whether I even need "options NATM" (currently I can happily instantiate a
MB>(of course non-functional) ATM interface using just "device atm"),

Since time has passed I'm not sure on this. You need optiosn NATM either
to do IP over ATM directly or to get the AF_NATM stuff. Don't remember,

From looking at the source I believe "options NATM" might only be needed to do IP over ATM directly. Specifically, routing information seems to be stored somewhere (this is where "options NATM" currently breaks). However, I have no idea what one actually gets with just "device atm" but no "options NATM". As I said, I can do atm_ifattach() successfully, but don't currently know what that really accomplishes.

I do not need IP over ATM, but rather need PPPoA. For this, I need to extract the raw PPP frames either directly, or from their LLC encapsulation, as per RFC2364. That I want to do via netgraph, specifically by expanding the functionality of the ng_atmllc node to also treat LLC/ISO, thereby turning ng_atmllc into "ng_llc" (RFC2684).

MB>- what do I need to do on the USB side to start receive and transmit machines
MB>(do I need to start separate kernel threads or just issue two
MB>usbd_transfer_setup() calls as for loading the firmware),

I'v no idea on this.

I would suppose, that your driver would appear to the atm stack as an ATM
interface, right?

That question was in fact more directed to Hans-Petter, and he has already answered it. But regarding your question, I simply don't yet know enough about the ATM stack. The only thing I know is that I can get raw ATM cells out of and into the USB interface/ADSL line, but I do not know how to make this meaningful to the current ATM stack. I probably need to do the AAL5 SAR myself, because from looking at the drivers (fatm, hatm, etc.) I have the impression that this is something which is normally handled by the hardware itself (does the hardware know how to handle either AAL0 or AAL5, doing SAR for the latter? And for AAL0, what do I get on a socket read/write? - One ore multiple cells? - Same for AAL5 - do I get one or may I also get multiple packets?).

I'd also be interested in understanding how I might be able to handle signaling information arriving over the ADSL line - I believe this does sometime happen.

MB>I do of course read the source, but with the scarce documentation available
MB>that's a steep learning curve.

You may try to look up the original paper on NATM - its a nice reading as
far as I remember...



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