Re: [PATCH 2/3] mac80211: Add support to trigger sta disconnect on hardware restart

From: Youghandhar Chintala
Date: Fri Sep 24 2021 - 05:14:25 EST

Hi Johannes

We thought sending the delba would solve the problem as earlier thought but the actual problem is with TX PN in a secure mode.
It is not because of delba that the Seq number and TX PN are reset to zero.
It’s because of the HW restart, these parameters are reset to zero.
Since FW/HW is the one which decides the TX PN, when it goes through SSR, all these parameters are reset.
The other peer say an AP, it does not know anything about the SSR on the peer device. It expects the next TX PN to be current PN + 1.
Since TX PN starts from zero after SSR, PN check at AP will fail and it will silently drop all the packets.


On 2021-09-24 13:09, Johannes Berg wrote:
On Fri, 2021-09-24 at 13:07 +0530, Youghandhar Chintala wrote:
Hi Johannes and felix,

We have tested with DELBA experiment during post SSR, DUT packet seq
number and tx pn is resetting to 0 as expected but AP(Netgear R8000) is
not honoring the tx pn from DUT.
Whereas when we tested with DELBA experiment by making Linux android
device as SAP and DUT as STA with which we don’t see any issue. Ping got
resumed post SSR without disconnect.

Hm. That's a lot of data, and not a lot of explanation :)

I don't understand how DelBA and PN are related?


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