On Wed, Jun 20, 2012 at 10:46 AM, Johannes Berg
<johannes@xxxxxxxxxxxxxxxx> wrote:
>> + * @NL80211_ATTR_SCAN_PSV_MAX_CH_TIME: Maximum passive scan time (in TUs),
>> + * u32 attribute (similar to @NL80211_ATTR_SCAN_MAX_CH_TIME).
>> + * Note:
>> + * The above channel time attributes are for the %NL80211_CMD_TRIGGER_SCAN
>> + * command. The attributes are optional, the driver will use default
>> + * channel time values if the attribute is not set.
>> + * If one of the min times will be greater than max or set to zero,
>> + * -EINVAL will be returned. For the software scan only the min times
>> + * are relevant.
>
> What if the driver doesn't support the timings?
>
The attributes are optional, so the scan will run as usual using the
default scan times defined in cfg for software scan and default driver
specific values for the hw_scan (if those exist).
>> + if (info->attrs[NL80211_ATTR_SCAN_MIN_CH_TIME]) {
>> + if (info->attrs[NL80211_ATTR_SCAN_MAX_CH_TIME]) {
>> + if (info->attrs[NL80211_ATTR_SCAN_PSV_MIN_CH_TIME]) {
>> + if (info->attrs[NL80211_ATTR_SCAN_PSV_MAX_CH_TIME]) {
>
> I think you should ignore the attributes if NL80211_FEATURE_SCAN_TIMES
> is not set. That will enforce that anyone implementing it sets the
> feature flag correctly, if they ever test their code at all anyway :-)
>
>
The porpoise of the NL80211_FEATURE_SCAN_TIMES (as we discussed
before) is to advertise this capability to usermode which implements
802.11k.
>> +int cfg80211_trigger_scan(struct cfg80211_registered_device *rdev)
>> +{
>> + struct cfg80211_scan_request *request;
>> +
>> + ASSERT_RDEV_LOCK(rdev);
>> +
>> + request = rdev->scan_req;
>> +
>> + if (!request)
>> + return -EINVAL;
>> +
>> + if (!request->min_passive_ch_time)
>> + request->min_passive_ch_time =
>> + ieee80211_msec_to_tu(IEEE80211_PSV_CH_TIME_MSEC);
>> + if (!request->min_ch_time)
>> + request->min_ch_time =
>> + ieee80211_msec_to_tu(IEEE80211_CH_TIME_MSEC);
>
> I pointed this out before -- this is problematic. Userspace could
> request a max time of 10, and then this would set the min time to 30,
> which means min > max which is completely stupid. We should prevent such
> settings.
>
This check is done in nl80211_trigger_scan(), please see:
+» » if·(request->min_ch_time·>·request->max_ch_time)
+» » » return·-EINVAL;
and
+» » if·(request->min_passive_ch_time·>·request->max_passive_ch_time)
+» » » return·-EINVAL;
in this case we return EINVAL, btw this also documented:
+ * If one of the min times will be greater than max or set to zero,
+ * -EINVAL will be returned. For the software scan only the min times
>
>> @@ -1023,6 +1047,20 @@ int cfg80211_wext_siwscan(struct net_device *dev,
>> if (wiphy->bands[i])
>> creq->rates[i] = (1 << wiphy->bands[i]->n_bitrates) - 1;
>>
>> + if (wreq->min_channel_time) {
>> + creq->min_ch_time = wreq->min_channel_time;
>
> are you sure that wext uses TUs?
>
yes, from "struct iw_scan_req":
__u32 min_channel_time; /* in TU */
__u32 max_channel_time; /* in TU */
--
Thanks,
Victor.
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