Questions Regarding ANQP Fetch

Jouni Malinen j at w1.fi
Fri Mar 21 14:22:02 EDT 2014


On Thu, Mar 20, 2014 at 11:09:48PM +0530, Shyam wrote:
> As I understand from the code the ANQP fetch is supported by 2 commands
>  1. FETCH_ANQP- To Fetch ANQP information from all the BSSIDs.
>  2. ANQP_GET- Fetch BSSID for a single BSSID.
> Now what was interested to see is that the FETCH_ANQP banks upon the
> in-memory cache maintained in the BSS structure. If the wifi is turned
> on-off or when the BSS flush happens this cache is cleared and hence we
> loose the data. Was there any reason why you didnt think about writing the
> anqp information into a file/DB in which case the data would be available
> upon state resets?

I'm not sure whether any ANQP information should really be expected to
remain constant and since there is no other way of confirming its
current validity apart from fetching it again, I don't see much point in
storing it to a file. The BSS table should not really be flushed during
normal operation, so the information there remains valid as long as the
AP is in range (and then for three minutes, by default, after that to
avoid temporary out-of-range state dropping an entry).

> Were you suggesting that clients read ANQP information from the BSS command
> and they cache it?

No.

What type of ANQP information are you thinking of here and what is the
justification in assuming it to remain static for longer periods of
time?

-- 
Jouni Malinen                                            PGP id EFC895FA


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