Re: [PATCH] Fix NetworkManager/wpa_supplicant race condition

[Dan Williams <dcbw@redhat.com>]

On Wed, 2007-04-18 at 13:18 -0600, Tim Gardner wrote:
> Dan Williams wrote:
> > On Wed, 2007-04-18 at 10:40 -0600, Tim Gardner wrote:
> >> This patch fixes an assumption made by wpa_supplicant. Any time
> >> wpa_supplicant requests to set an ESSID (e.g., associate), it expects an
> >> event notifying that association has completed. If the Networkmanager
> >> has already setup an association, such as for an open auth AP, then the
> >> request to associate by wpa_supplicant will be ignored.
> >>
> >> If Networkmanager is requested to restart the connection, such as by
> >> clicking on the SSID, then wpa_supplicant is allowed to build the
> >> association from scratch, which always works.
> >>
> >> https://bugs.launchpad.net/ubuntu/+source/linux-source-2.6.20/+bug/103768
> >>
> >> By always emitting this event, am I causing any unintended side effects?
> > 
> > Interesting.  Setting the SSID should _always_ trigger a reassociation,
> > and therefore eventually trigger an SIOCGIWAP event to userspace.  So
> > this patch looks right from the behavioral point of view.
> > 
> > But it doesn't look right from the technical perspective.  Why isn't
> > softmac trying to reassociate?  Does it automatically reassociate if
> > parameters, like auth mode, keys, WPA, etc are set and so therefore,
> > when it comes around to the SSID being set it doesn't really matter?  If
> > so, we should still be sending the event, and this patch is OK.  But can
> > somebody _guarantee_ that if I authenticate to an AP, then later call
> > SIOCSIWENCODE, and then SIOCSIWESSID to the same SSID, that the new WEP
> > keys have been applied and a reassociation has occurred?  If the auth
> > mode is shared key, a reassociation attempt needs to happen.
> > 
> > WEXT convention is that setting the SSID or BSSID triggers reassociation
> > with the current parameters.  I'd argue that softmac should be starting
> > the association process over again when either SIOCSIWESSID or
> > SIOCSIWBSSID is called.
> > 
> > Dan
> > 
> >> rtg
> >> plain text document attachment (bug_103768)
> >> diff --git a/net/ieee80211/softmac/ieee80211softmac_wx.c b/net/ieee80211/softmac/ieee80211softmac_wx.c
> >> index fa2f7da..cc2e8ba 100644
> >> --- a/net/ieee80211/softmac/ieee80211softmac_wx.c
> >> +++ b/net/ieee80211/softmac/ieee80211softmac_wx.c
> >> @@ -88,6 +88,13 @@ ieee80211softmac_wx_set_essid(struct net_device *net_dev,
> >>  		   !memcmp(n->essid.data, extra, n->essid.len)) {
> >>  			dprintk(KERN_INFO PFX "Already associating or associated to "MAC_FMT"\n",
> >>  				MAC_ARG(sm->associnfo.bssid));
> >> +			/* wpa_supplicant expects an association event, regardless of prior
> >> +			 * association state. If associating, then the associnfo.work task
> >> +			 * will send the appropriate event.
> >> +			 */
> >> +			if (sm->associnfo.associated)
> >> +				ieee80211softmac_call_events_locked(sm,
> >> +					IEEE80211SOFTMAC_EVENT_ASSOCIATED, n);
> >>  			goto out;
> >>  		} else {
> >>  			dprintk(KERN_INFO PFX "Canceling existing associate request!\n");
> > 
> 
> I don't think simply reassociating is sufficient. Consider what happens
> if the authentication algorithm is changed. ieee80211_wx_set_auth() does
> nothing more then set some values. A subsequent attempt to reassociate
> would get all hosed up.

When I say "reassociate", I mean a new association cycle to the _same_
BSSID/SSID using the settings that are current at that point in time.  I
guess I should have made that clear.

Dan

> A quick look at ieee80211_ioctl_siwessid() shows that it always forces
> an authentication cycle.
> 
> I'll experiment a little to see how the Softmac can be driven through an
> authentication/association cycle on calls to SIOCSIWESSID or SIOCSIWAP.
> 
> rtg