netdev - Re: Required sequence to set wireless parameters? (was: 2.6.29-rc8: Reported regressions from 2.6.28)

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Message-Id: <1237481630.5100.92.camel@johannes.local>
Date:	Thu, 19 Mar 2009 17:53:50 +0100
From:	Johannes Berg <johannes@...solutions.net>
To:	Frans Pop <elendil@...net.nl>
Cc:	"John W. Linville" <linville@...driver.com>,
	jeff.chua.linux@...il.com, mingo@...e.hu,
	torvalds@...ux-foundation.org, rjw@...k.pl,
	linux-kernel@...r.kernel.org, bunk@...nel.org,
	akpm@...ux-foundation.org, kernel-testers@...r.kernel.org,
	netdev@...r.kernel.org
Subject: Re: Required sequence to set wireless parameters? (was:
 2.6.29-rc8: Reported regressions from 2.6.28)

On Thu, 2009-03-19 at 16:02 +0100, Frans Pop wrote:

> Mostly just curious, but is that actually required by some wireless 
> standard? If not, is it really reasonable to ask userland to do things in 
> that particular order?

Wext is a mess, and we've known that for a long time... But no, the
sequence should _not_ be required, it's just _easier_ for the kernel,
and as such has a better probability of succeeding if there are
problems, it should still work though.

However, one thing that will _not_ work is this:

iwconfig wlan0 essid xyz
iwconfig wlan0 key s:xyz

you still need

iwconfig wlan0 ap any

or anything similar after setting the key to trigger the kernel to do
something.

> Reason I ask is that for example when writing wireless support for e.g. a 
> distro installation system, it seems most logical to *first* ask the user 
> what network (ESSID) he wants to connect to. Next to check if we can 
> connect to that network without additional authentication and only then, 
> if needed, ask for keys etc.
> If it's not possible to set that info in that logical order that seems 
> rather restrictive to me and would probably mean that you'd have to reset 
> AP, ESSID and possibly other settings before each incremental attempt.

That's a pretty wrong argument, nothing says your software cannot
collect all the information and then give it to the kernel at once
later, I think... In fact, this is required anyway when you use RSN or
WPA (wpa_supplicant needs all information at once), for example.

johannes

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