Re: proposal: rename DLT_PRISM_HEADER

["Guy Harris" <gharris () sonic net>]

David Young said:
> I propose to change the DLT_PRISM_HEADER semantics.  I am trying to
> identify the stakeholders in such a change, to find out what they think.
> I figure some of them read this list.
>
> For DLT_PRISM_HEADER, libpcap expects a header that is a whopping 144
> bytes long. It does not resemble any header a Prism radio will give, so
> the name DLT_PRISM_HEADER for it is misleading.
>
> Examining linux-wlan-ng and ethereal, the header actually consists of
> length-type-value (LTV) tuples for received signal strength, PHY type,
> and other radio parameters.  This seems like a stab at a generic 802.11
> radio header. Why, then, is it not called DLT_IEEE802_11_RADIO, for
> example? The former name is misleading.
>
> I ask because I am adding to NetBSD a DLT whose header contains the
> portions of the Prism header preceding the IEEE802.11 header.  I have
> tentatively called it DLT_SHORT_PRISM_HEADER, to avoid clashing with
> DLT_PRISM_HEADER, but I prefer to rename the old DLT_PRISM_HEADER
> to DLT_IEEE802_11_RADIO, and to call the Prism-specific header
> DLT_PRISM_HEADER.
>
> Your thoughts?
>
> Dave
>
> --
> David Young             OJC Technologies
> dyoung () ojctech com      Engineering from the Right Brain

As I remember, there's more to it than that; DLT_PRISM_HEADER was
originally a short header with just the Prism stuff, but it's now both
that *and* the new TLV header, pending support in Linux for a new ARPHRD_
type for the new TLV header (and support in libpcap for a new DLT_ value
for the new TLV header).

As long as the DLT_PRISM_HEADER header begins with a value other than
0x80211001 (or other 0x80211XXX values), Ethereal will interpret the
packet as having the old Prism header.


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