Questions Regarding ANQP Fetch

[Shyam]

Thanks Jouni for your reply.
Okay, Its a bit clear now..However I am curious to know one thing from your
reply:
Is ANQP information consumption limited to wpa_supplicant? I thought that
the client could read the ANQP information through BSS command?

Thanks,
Shyam

> 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.
Okay, so the
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?

> 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?



On Thu, Mar 20, 2014 at 11:09 PM, Shyam <shyamms2003 at gmail.com> wrote:

> Hi Jouni,
>> 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?
> Were you suggesting that clients read ANQP information from the BSS
> command and they cache it?
>
> Pls share your thoughts?
>
> Thanks
> Shyam
>
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