[PATCH] driver_nl80211: set_country fix

[Igal Chernobelsky]

On 06/24/2013 11:04 AM, Johannes Berg wrote:
> On Sun, 2013-06-23 at 16:07 +0300, Igal Chernobelsky wrote:
>> Regulatory domain setting may take some time.
>> Getting reg domain info immediately after reg domain setting returns
>> invalid reg domain data. Loop is added to read reg domain info back and
>> to compare set country. If read country does not match, fail to 1 sec sleep
>> and retry get/compare again.
>>
>> Signed-off-by: Igal Chernobelsky<igalc at ti.com>
>> ---
>>   src/drivers/driver_nl80211.c |   53 +++++++++++++++++++++++++++++++++++++++++-
>>   1 files changed, 52 insertions(+), 1 deletions(-)
>>
>> diff --git a/src/drivers/driver_nl80211.c b/src/drivers/driver_nl80211.c
>> index f705a0c..cc5084b 100644
>> --- a/src/drivers/driver_nl80211.c
>> +++ b/src/drivers/driver_nl80211.c
>> @@ -2689,6 +2689,37 @@ static void wpa_driver_nl80211_event_receive(int sock, void *eloop_ctx,
>>   }
>>
>>
>> +static int get_country_handler(struct nl_msg *msg, void *arg)
>> +{
>> +	char * alpha2 = (char *) arg;
>> +	struct nlattr *tb_msg[NL80211_ATTR_MAX + 1];
>> +	struct genlmsghdr *gnlh = nlmsg_data(nlmsg_hdr(msg));
>> +
>> +	nla_parse(tb_msg, NL80211_ATTR_MAX, genlmsg_attrdata(gnlh, 0),
>> +		  genlmsg_attrlen(gnlh, 0), NULL);
>> +	if (!tb_msg[NL80211_ATTR_REG_ALPHA2]) {
>> +		wpa_printf(MSG_DEBUG, "nl80211: No country information "
>> +			   "available");
>> +		return NL_SKIP;
>> +	}
>> +	os_memcpy(alpha2, nla_data(tb_msg[NL80211_ATTR_REG_ALPHA2]), 3);
>> +	return NL_SKIP;
>> +}
>> +
>> +static int nl80211_get_country(struct wpa_driver_nl80211_data *drv,
>> +				char *alpha2)
>> +{
>> +	struct nl_msg *msg;
>> +
>> +	msg = nlmsg_alloc();
>> +	if (!msg)
>> +		return -ENOMEM;
>> +
>> +	nl80211_cmd(drv, msg, 0, NL80211_CMD_GET_REG);
>> +	return send_and_recv_msgs(drv, msg, get_country_handler, alpha2);
>> +}
>> +
>> +
>>   /**
>>    * wpa_driver_nl80211_set_country - ask nl80211 to set the regulatory domain
>>    * @priv: driver_nl80211 private data
>> @@ -2703,7 +2734,10 @@ static int wpa_driver_nl80211_set_country(void *priv, const char *alpha2_arg)
>>   	struct i802_bss *bss = priv;
>>   	struct wpa_driver_nl80211_data *drv = bss->drv;
>>   	char alpha2[3];
>> +	char alpha2_res[3];
>>   	struct nl_msg *msg;
>> +	int count;
>> +	int ret;
>>
>>   	msg = nlmsg_alloc();
>>   	if (!msg)
>> @@ -2718,7 +2752,24 @@ static int wpa_driver_nl80211_set_country(void *priv, const char *alpha2_arg)
>>   	NLA_PUT_STRING(msg, NL80211_ATTR_REG_ALPHA2, alpha2);
>>   	if (send_and_recv_msgs(drv, msg, NULL, NULL))
>>   		return -EINVAL;
>> -	return 0;
>> +
>> +	/* Validate coutry setting and retry up to 3 times if not match */
>> +	for (count = 0; count<  3; count++) {
>> +		os_memset(alpha2_res, 0, sizeof(alpha2));
>> +		ret = nl80211_get_country(drv, alpha2_res);
>> +		if (ret)
>> +			return ret;
>> +		if (os_strncmp(alpha2, alpha2_res, 3)) {
>> +			wpa_printf(MSG_DEBUG, "wpa_driver_nl80211_set_country:"
>> +					"retry country set after delay");
>> +			os_sleep(1, 0);
>> +		} else {
>> +			/* contry set is completed */
>> +			return 0;
>> +		}
>> +	}
>> +	wpa_printf(MSG_ERROR, "wpa_driver_nl80211_set_country: failed");
>> +	return -EINVAL;
> I don't think this is really a failure -- if you request a country but
> the kernel already has one it might create an intersection etc. Might
> want to even abort the loop in that case.
>
> johannes
>

Johannes, is it possible for you to elaborate about this use case?

The patch is intended to fix hostapd issue while starting on 5 GHz channel
(e.g. country_code=US,  channel=36). Hostapd initialization always fails
at the first start while reg domain is still being configured to US
(tested on TI Sitara am335x evm board).

In this use case hostapd sets US reg domain and then immediately reads back
hw supported modes and channels (get_hw_feature_data) which returns 
invalid data
at this phase (still for default reg domain and not US). So AP 
initialization fails due to
5GHz channels is not supported to start Beacons tx. Re-running hostapd 
the next time is OK
as reg domain has been already correctly set to US.

The patch propose synchronization mechanism for setting reg domain (set 
and read back)
before reading hw supported modes.


-- 

Best regards
Igal