On Feb 8, 2012, at 3:26 AM, mike wakerly wrote:
> I'd like to request a new encapsulation type for NFC Logical Link
> Control Protocol (LLCP) [1].
...
> A new encapsulation type is needed for reasons similar to i2c and
> bluetooth.
No, it's needed because no existing link-layer header type listed on the page at
http://www.tcpdump.org/linktypes.html
corresponds to the NFC LLCP; even if there were *no* pseudo-header there would
*still* need to be a new link-layer header type.
> Hosts need to record frame directionality in addition to
> raw frame data. As an example, a psuedo-header prepended to
> individual LLCP frames recorded in this format might look like this:
>
> struct llcp_phdr {
> guint16 adapter; /* Adapter number, typically 0. */
> guint16 flags; /* Direction flag (TX/RX) and future use. */
> };
>
> Can you allocate a new DLT_ for this?
Yes, once there's a firm final specification for what the pseudo-header will
look like for all frames. (If there's more than one type of pseudo-header,
there will have to be more than one link-layer header type value allocated, one
for each pseudo-header type.)
Presumably what follows the pseudo-header will be an LLCP PDU of the form
described in section 4.1 "LLC PDU Format" of the LLCP specification, i.e. a
byte containing the DSAP and upper two bits of the PTYPE, followed by a byte
containing the lower two bits of the PTYPE and the SSAP, followed by the
sequence byte if the frame has sequence numbers, followed by the bytes of
payload.
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