Re: Correct radiotap header for 802.11ad

[Richard Sharpe <realrichardsharpe-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>]

On Mon, Aug 24, 2015 at 12:40 AM, Johannes Berg
<johannes-cdvu00un1VgdHxzADdlk8Q@public.gmane.org> wrote:
> On Sat, 2015-08-22 at 16:34 -0700, Guy Harris wrote:
>>
>> For what it's worth, it appears that the wil6210 driver:
>>
>>       https://wireless.wiki.kernel.org/en/users/drivers/wil6210
>>
>> uses the MCS field and its mcs value for 11ad.  It can also be
>> configured to supply raw "PHY data" with a vendor-namespace field.
>>
>> So code that processes radiotap headers, such as Wireshark's radiotap
>> -header dissector, will have to interpret packets with an MCS field
>> and a channel frequence in the 11ad range as being 11ad packets, and
>> treat the mcs value in the MCS field as an 11ad MCS, not an 11n MCS.
>
> That just seems really lazy though - I think we should rather fix that
> driver and define a proper 60G radiotap field.

Can I suggest something like the following, although we have defined
the presence flags as a UINT32 for the moment in Wireshark:

--- ../linux-3.11-rc6/include/net/ieee80211_radiotap.h 2013-10-20
13:34:23.633866699 -0700
+++ ./include/net/ieee80211_radiotap.h 2015-08-24 09:12:12.416137951 -0700
@@ -190,6 +190,11 @@
  * IEEE80211_RADIOTAP_VHT u16, u8, u8, u8[4], u8, u8, u16
  *
  * Contains VHT information about this frame.
+ *
+ * IEEE80211_RADIOTAP_DMG       u8, u8
+ *
+ *      Contains DMG information about the frame. Currently presence flags
+ *      and the MCS index, if present.
  */
 enum ieee80211_radiotap_type {
  IEEE80211_RADIOTAP_TSFT = 0,
@@ -214,6 +219,7 @@
  IEEE80211_RADIOTAP_MCS = 19,
  IEEE80211_RADIOTAP_AMPDU_STATUS = 20,
  IEEE80211_RADIOTAP_VHT = 21,
+ IEEE80211_RADIOTAP_DMG = 22,

  /* valid in every it_present bitmap, even vendor namespaces */
  IEEE80211_RADIOTAP_RADIOTAP_NAMESPACE = 29,

Also, there is the matter of whether or not we need to indicate Static
Tone Pairing and Dynamic Tone Pairing as that is a bit in the PHY
header and is needed to make sense of MCS values 13-17, maybe.

-- 
Regards,
Richard Sharpe
(何以解憂？唯有杜康。--曹操)