Re: iwd picking worse network despite better one available - Sven-Hendrik Haase

From: "Sven-Hendrik Haase" <mailinglists@svenstaro.org>
To: "James Prestwood" <prestwoj@gmail.com>, iwd@lists.linux.dev
Subject: Re: iwd picking worse network despite better one available
Date: Wed, 27 Mar 2024 20:21:14 +0100	[thread overview]
Message-ID: <07f49420-74e8-4954-bd87-9ae3290e86d3@app.fastmail.com> (raw)
In-Reply-To: <16f79ea4-32a2-47f5-b6a9-cfd911454a6a@gmail.com>

On Wed, Mar 27, 2024, at 19:54, James Prestwood wrote:
> Hi,
> 
> On 3/27/24 11:36 AM, Sven-Hendrik Haase wrote:
> > Hello,
> >
> > I've spent a good chunk of my evening looking into why iwd doesn't select the network I want it to select. I have a network "Home" with two APs. iwd seems to strongly prefer the AP that is further away and that has worse strength as measured by iwd.
> >
> >  From some testing, I believe it has to do with the AP rather than the wifi adapter. I tested a wifi adapter using mt7921e and one using iwlwifi and the result is the same in both cases. The APs are both pretty modern: The one iwd doesn't like is a FRITZ!Box 7590 AX while the one it likes is a FRITZ!Repeater 6000. From the log it seems that iwd is unable to perform a proper data rate estimation and then falls back to some default. At any rate, the rank would indicate that the estimated data rate plays an important role. If I use the developer mode to force roaming to the AP I want (named "better" in the log) then I'm able to use it perfectly well with a good data rate.
> >
> > As such I think this is a bug _somewhere_ but I'm not exactly sure where. I searched the configuration options but it seems it's not possible to turn off the data rate estimations for the ranking. I'd be perfectly happy to just go by signal strength. However, I suppose it would be better to actually fix the core problem in iwd.
> 
> IWD bases the ranking of BSS's heavily off the estimated data rate. If 
> that fails then as you see the rank is very low as it defaults back to 
> 802.11b rates. There are several IEs the AP sends which IWD parses, any 
> one of them could be either not included at all, or not be formatted 
> correctly, or an actual bug in the parsing code. Could you get an iwmon 
> capture of IWD scanning your APs so I could take a look and see exactly 
> why its failing? Then we can go from there.
> 
> Thanks,
> 
> James
> 

Hi James,

You should have received a pcap file of an iwd restart in a separate email. I hope there's some usable data in there for you.

Cheers,
Sven