From: Dave <kilroyd@googlemail.com>
To: Johannes Berg <johannes@sipsolutions.net>
Cc: linux-wireless@vger.kernel.org
Subject: Re: [RFC 5/5] cfg80211: scan before connect if we don't have the bss
Date: Wed, 19 Aug 2009 20:30:05 +0100 [thread overview]
Message-ID: <4A8C52BD.5070609@gmail.com> (raw)
In-Reply-To: <1250668113.16393.25.camel@johannes.local>
Johannes Berg wrote:
> On Wed, 2009-08-19 at 01:04 +0100, David Kilroy wrote:
>> @@ -791,18 +824,55 @@ int __cfg80211_connect(struct cfg80211_registered_device *rdev,
>> + bss = cfg80211_get_bss(wdev->wiphy, NULL, connect->bssid,
>> + connect->ssid, connect->ssid_len,
>> + WLAN_CAPABILITY_ESS,
>> + WLAN_CAPABILITY_ESS);
>
> Hmm. What if the bssid isn't set? Then the card might select a different
> BSS than the one we have on the scan list.
That's correct. For the Agere driver that's also true when bssid is set
- we can't specify which AP the firmware connects to.
>> + /* Failed to clone (or scan), so we can't
>> + * delay the connect. Free everything up and
>> + * go ahead with the connect */
>> + if (wdev->conn)
>> + kfree(wdev->conn->ie);
>> + kfree(wdev->conn);
>> + wdev->conn = NULL;
>
> and that would then run into the warning and the problem anyway? Better
> to just reject with -ENOMEM I think? Also, I really don't think you
> should use wdev->conn anywhere in this code path, because some code
> looks at that to figure out whether or not the cfg80211 SME is used.
I thought that might be the case.
>> + } else {
>> + cfg80211_put_bss(bss);
>
>> err = rdev->ops->connect(&rdev->wiphy, dev, connect);
>
> And it's all racy too -- by the time the driver calls connect_result(),
> the BSS might have expired after it was found here now.
Agreed, but with a 15s expiry period I wouldn't expect this to be a
problem in practice.
> I don't think this is really feasible to implement in cfg80211.
cfg80211 seemed like the appropriate place because it avoids different
(fullmac) drivers having to re-implement this.
> Couldn't
> the driver do a probe to the BSS that the device selected, and report
> that before the connect result?
Yes, that's possible. If we went this way it would make sense to encode
this in the interface by changing the cfg80211_connect_result prototype to:
void cfg80211_connect_result(struct net_device *dev,
const struct bss *bss,
const u8 *req_ie, size_t req_ie_len,
const u8 *resp_ie, size_t resp_ie_len,
u16 status, gfp_t gfp);
So on connecting:
* the driver has to call cfg80211_get_bss() to get the bss pointer.
* if it is not available, scan/probe to get the information, call
cfg80211_inform_bss(), and then use the returned pointer in the
cfg80211_connect_result call.
This means the driver may have to hold onto the IE info to use after the
scan returns.
Another alternative is for cfg80211_connect_result to trigger the scan
if it doesn't have the bss, and only complete the connect when the scan
returns. I think I like the sound of this best.
Dave.
next prev parent reply other threads:[~2009-08-19 19:30 UTC|newest]
Thread overview: 16+ messages / expand[flat|nested] mbox.gz Atom feed top
2009-08-19 0:04 [RFC v2 0/5] orinoco: use cfg80211 for key manipulation David Kilroy
2009-08-19 0:04 ` [RFC 1/5] orinoco: add cfg80211 connect and disconnect David Kilroy
2009-08-19 0:04 ` [RFC 2/5] orinoco: add cfg80211 join_ibss and leave_ibss David Kilroy
2009-08-19 0:04 ` [RFC 3/5] orinoco: implement cfg80211 key manipulation functions David Kilroy
2009-08-19 0:04 ` [RFC 4/5] orinoco: do WE via cfg80211 David Kilroy
2009-08-19 0:04 ` [RFC 5/5] cfg80211: scan before connect if we don't have the bss David Kilroy
2009-08-19 7:48 ` Johannes Berg
2009-08-19 19:30 ` Dave [this message]
2009-08-19 19:37 ` Johannes Berg
2009-08-20 18:01 ` Dave
2009-08-20 6:39 ` Jussi Kivilinna
2009-08-31 17:59 ` [RFC v2 0/5] orinoco: use cfg80211 for key manipulation John W. Linville
2009-09-12 23:54 ` Dave Kilroy
2009-10-23 19:05 ` Dave
2009-10-26 13:17 ` Only device wlan1 but no connection Fritz!WLAN USB stick N2.4 Ed Vaessen
2009-10-26 14:57 ` Luis R. Rodriguez
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=4A8C52BD.5070609@gmail.com \
--to=kilroyd@googlemail.com \
--cc=johannes@sipsolutions.net \
--cc=linux-wireless@vger.kernel.org \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).